1
00:00:00,750 --> 00:00:03,120
The following content is
provided under a Creative

2
00:00:03,120 --> 00:00:04,510
Commons license.

3
00:00:04,510 --> 00:00:06,720
Your support will help
MIT OpenCourseWare

4
00:00:06,720 --> 00:00:10,810
continue to offer high quality
educational resources for free.

5
00:00:10,810 --> 00:00:13,380
To make a donation or to
view additional materials

6
00:00:13,380 --> 00:00:17,340
from hundreds of MIT courses,
visit MIT OpenCourseWare

7
00:00:17,340 --> 00:00:18,226
at ocw.mit.edu.

8
00:00:22,232 --> 00:00:23,690
MICHAEL SHORT: So
as a quick review

9
00:00:23,690 --> 00:00:26,180
of all the different
biological effects,

10
00:00:26,180 --> 00:00:30,080
we've pretty much
taken it up to here.

11
00:00:30,080 --> 00:00:32,870
We've explained the
physical and chemical stages

12
00:00:32,870 --> 00:00:34,730
of what happens when
radiation interacts

13
00:00:34,730 --> 00:00:37,970
with mostly bags of water with
some solutes in them, better

14
00:00:37,970 --> 00:00:41,300
known as organisms at
dynamic equilibrium.

15
00:00:41,300 --> 00:00:45,590
Everything from the sort of
femptosecond level, ionization

16
00:00:45,590 --> 00:00:47,450
of water almost
certainly, because that's

17
00:00:47,450 --> 00:00:50,240
most of what
biological things are,

18
00:00:50,240 --> 00:00:55,610
to the formation of many, many,
many, many, many different

19
00:00:55,610 --> 00:01:00,260
radiolysis byproducts eventually
that end up as just a few

20
00:01:00,260 --> 00:01:02,840
that we care about, the
longer-lived radiolytic

21
00:01:02,840 --> 00:01:06,200
byproducts that will
then diffuse away

22
00:01:06,200 --> 00:01:08,600
from the original
damage cascades

23
00:01:08,600 --> 00:01:13,490
and go on to eat something
else, likely DNA or something

24
00:01:13,490 --> 00:01:18,680
that you don't want to get
oxidized or chemically changed.

25
00:01:18,680 --> 00:01:21,797
We talked a little bit
about radiolysis in reactors

26
00:01:21,797 --> 00:01:23,630
and how you can actually
measure it directly

27
00:01:23,630 --> 00:01:27,470
which was only done really a few
years ago which is pretty cool.

28
00:01:27,470 --> 00:01:29,270
Just to remind you
of this experiment,

29
00:01:29,270 --> 00:01:31,250
there's a tiny
high-pressure cell

30
00:01:31,250 --> 00:01:33,270
of high-pressure,
high-temperature water.

31
00:01:33,270 --> 00:01:37,130
There is a foil sample with a
very thin region and protons

32
00:01:37,130 --> 00:01:40,100
firing through it, so that
they both irradiate the sample

33
00:01:40,100 --> 00:01:43,690
and induce radiolysis in
the water at the same time.

34
00:01:43,690 --> 00:01:46,640
And this way, you can test
the effect of radiolysis

35
00:01:46,640 --> 00:01:49,430
in the water here versus just
plain, old, high-pressure,

36
00:01:49,430 --> 00:01:51,410
high-temperature corrosion here.

37
00:01:51,410 --> 00:01:53,510
And the results are
pretty striking,

38
00:01:53,510 --> 00:01:56,600
where you can clearly see
the boundary where the proton

39
00:01:56,600 --> 00:02:00,380
beam was as well as
the increased thickness

40
00:02:00,380 --> 00:02:03,630
of the oxide and corrosion
layer formed when radiolysis

41
00:02:03,630 --> 00:02:06,650
is turned on, so to speak.

42
00:02:06,650 --> 00:02:11,820
We went through DNA damage, and
we ended with pseudoscience.

43
00:02:11,820 --> 00:02:14,710
So I want to bring up a couple--

44
00:02:14,710 --> 00:02:17,590
no, we don't have time for that.

45
00:02:17,590 --> 00:02:20,133
But we spent the last 15
minutes of class railing

46
00:02:20,133 --> 00:02:22,800
against pseudoscience and making
sure that you check your facts,

47
00:02:22,800 --> 00:02:24,342
but we pointed out
a number of things

48
00:02:24,342 --> 00:02:26,430
wrong with some of the studies.

49
00:02:26,430 --> 00:02:29,940
So aside from just that
guy misreading everything

50
00:02:29,940 --> 00:02:32,820
on that entire blog, of
the studies that you felt

51
00:02:32,820 --> 00:02:36,260
weren't very convincing, what
do you remember about them?

52
00:02:36,260 --> 00:02:38,900
Some of those studies were
totally fine, but some of them

53
00:02:38,900 --> 00:02:41,242
were not.

54
00:02:41,242 --> 00:02:43,350
AUDIENCE: The ones with
particularly small sample

55
00:02:43,350 --> 00:02:43,850
sizes.

56
00:02:43,850 --> 00:02:46,267
MICHAEL SHORT: That's what I
was hoping someone would say.

57
00:02:46,267 --> 00:02:47,830
Yeah, the case
study of four women

58
00:02:47,830 --> 00:02:49,900
who got breast
cancer in the pocket

59
00:02:49,900 --> 00:02:52,840
where they held their
cell phones, four, right?

60
00:02:52,840 --> 00:02:56,950
Or in a study of 29 humans, 11
of them got brain tumors here.

61
00:02:56,950 --> 00:03:00,080
It's pretty easy to cherry
pick small amounts of data.

62
00:03:00,080 --> 00:03:03,430
I did want to say that just
because radio frequency

63
00:03:03,430 --> 00:03:07,720
photons aren't ionizing, doesn't
mean they can't hurt you.

64
00:03:07,720 --> 00:03:12,250
If you've ever-- no, no one's
ever been inside a microwave.

65
00:03:12,250 --> 00:03:14,170
I wonder if anyone's
ever felt the effects

66
00:03:14,170 --> 00:03:16,990
of an external microwave
being by something like this,

67
00:03:16,990 --> 00:03:18,400
the active denial system.

68
00:03:18,400 --> 00:03:22,210
One of my favorite weapons ever,
because it doesn't actually

69
00:03:22,210 --> 00:03:24,190
permanently hurt anyone.

70
00:03:24,190 --> 00:03:26,890
It just heats up the
outer layer of your skin.

71
00:03:26,890 --> 00:03:30,850
It fires these non-ionizing
photons at RF frequency

72
00:03:30,850 --> 00:03:34,180
and effectively makes you
feel like you're on fire.

73
00:03:34,180 --> 00:03:36,610
So if there's a whole mess
of troops charging at you--

74
00:03:36,610 --> 00:03:40,600
let's say at the DMZ from
North and South Korea--

75
00:03:40,600 --> 00:03:42,910
all you've got to do
is turn on this thing,

76
00:03:42,910 --> 00:03:44,470
and they all think
they're on fire,

77
00:03:44,470 --> 00:03:47,380
because their body is sending
them signals that I'm on fire.

78
00:03:47,380 --> 00:03:49,390
And then you turn it
off, and they're OK.

79
00:03:49,390 --> 00:03:52,480
So no loss of life,
no permanent damage,

80
00:03:52,480 --> 00:03:54,730
a lot of maybe
psychological, but whatever,

81
00:03:54,730 --> 00:03:56,820
you can't see that.

82
00:03:56,820 --> 00:03:57,820
AUDIENCE: Active denial.

83
00:03:57,820 --> 00:04:00,580
MICHAEL SHORT: Active denial
system, great name for it,

84
00:04:00,580 --> 00:04:01,210
isn't it?

85
00:04:01,210 --> 00:04:03,335
Yeah, I think non-lethal
weapons are really the way

86
00:04:03,335 --> 00:04:07,270
of the future is just make
it unpleasant to engage

87
00:04:07,270 --> 00:04:09,790
in warfare, and
people probably won't.

88
00:04:09,790 --> 00:04:13,720
But then no one has to
get hurt, which is nice.

89
00:04:13,720 --> 00:04:16,600
But then onto the sources of
data, because like Sarah said,

90
00:04:16,600 --> 00:04:19,660
sample size is everything,
especially when you're

91
00:04:19,660 --> 00:04:22,210
trying to figure out, are
small amounts of radiation

92
00:04:22,210 --> 00:04:23,110
bad for you?

93
00:04:23,110 --> 00:04:25,210
This simple question
hasn't really

94
00:04:25,210 --> 00:04:28,960
been answered suitably yet,
and that's because, thank god,

95
00:04:28,960 --> 00:04:31,600
we don't have enough
people exposed

96
00:04:31,600 --> 00:04:33,730
to small but measurable
amounts of radiation

97
00:04:33,730 --> 00:04:37,300
to draw meaningful
conclusions from this data.

98
00:04:37,300 --> 00:04:40,810
I think that's a good thing,
is if we were certain about

99
00:04:40,810 --> 00:04:42,730
whether small
amounts of radiation,

100
00:04:42,730 --> 00:04:44,795
like one millisieverts,
could cause cancer,

101
00:04:44,795 --> 00:04:47,170
then there would have been
millions or billions of people

102
00:04:47,170 --> 00:04:49,900
exposed, and so it's kind of a
good thing that they weren't.

103
00:04:49,900 --> 00:04:52,510
But the sources of this
data, the first source

104
00:04:52,510 --> 00:04:55,522
was radium dial workers,
like you may have heard of,

105
00:04:55,522 --> 00:04:57,730
the folks that would lick
the paint brushes with glow

106
00:04:57,730 --> 00:04:59,560
in the dark radium watches.

107
00:04:59,560 --> 00:05:04,090
They ended up setting the first
occupational limit for dose,

108
00:05:04,090 --> 00:05:05,950
because they were
the first large group

109
00:05:05,950 --> 00:05:09,220
to be exposed to radiation
in a controlled setting.

110
00:05:09,220 --> 00:05:12,400
Things like uranium miners,
radon breathers, better known

111
00:05:12,400 --> 00:05:15,880
as us, but especially
folks that smoke anything.

112
00:05:15,880 --> 00:05:19,840
Medical diagnostics, so anyone
that gets a medical procedure,

113
00:05:19,840 --> 00:05:22,060
you can follow up with them
to find out what's, let's

114
00:05:22,060 --> 00:05:24,820
say, the extra incidence
of cancer and figure

115
00:05:24,820 --> 00:05:27,880
out, if you have a
high-dose medical procedure,

116
00:05:27,880 --> 00:05:30,520
does it induce secondary
cancer down the line?

117
00:05:30,520 --> 00:05:33,810
But like we said last time,
down the line is the key here.

118
00:05:33,810 --> 00:05:35,780
I'd take a whole
bunch of radiation

119
00:05:35,780 --> 00:05:38,830
now, if it was going to
save my life now, and maybe

120
00:05:38,830 --> 00:05:40,150
make it messed up in 20 years.

121
00:05:40,150 --> 00:05:42,100
Because then you get
20 more years of life

122
00:05:42,100 --> 00:05:43,800
or however long you get.

123
00:05:43,800 --> 00:05:45,670
And then from
accidents, survivors

124
00:05:45,670 --> 00:05:48,610
of the atomic bombs, not just
the folks at the epicenter,

125
00:05:48,610 --> 00:05:51,610
but in the whole fallout
regions and nearby, as well as

126
00:05:51,610 --> 00:05:54,970
nearby nuclear accidents
and the criticality events

127
00:05:54,970 --> 00:05:58,000
like the demon core that you
guys analyzed on the exam.

128
00:05:58,000 --> 00:06:00,340
Luckily, there aren't
a lot of those, either.

129
00:06:00,340 --> 00:06:03,260
But they were pretty severe,
the ones that got exposed.

130
00:06:03,260 --> 00:06:05,260
And speaking of accidents,
has anyone ever heard

131
00:06:05,260 --> 00:06:08,150
of the Kyshtym disaster?

132
00:06:08,150 --> 00:06:10,430
This is the third-worst
nuclear accident

133
00:06:10,430 --> 00:06:13,760
that we know of in history,
after Chernobyl and Fukushima,

134
00:06:13,760 --> 00:06:15,560
and worse than
Three Mile Island,

135
00:06:15,560 --> 00:06:18,620
because Three Mile Island
was an almost accident.

136
00:06:18,620 --> 00:06:21,050
There was some partial
melting of the core.

137
00:06:21,050 --> 00:06:23,630
There was almost no
release of radioactivity.

138
00:06:23,630 --> 00:06:26,420
And the definition of a nuclear
accident in the public sense

139
00:06:26,420 --> 00:06:28,490
is release of radioactivity.

140
00:06:28,490 --> 00:06:31,040
There's actually two
quantities that folks

141
00:06:31,040 --> 00:06:33,680
in PRA, or Probabilistic
Risk Analysis,

142
00:06:33,680 --> 00:06:34,790
are most interested in.

143
00:06:34,790 --> 00:06:38,630
Has anyone heard of these
terms, CDF and LERF?

144
00:06:38,630 --> 00:06:43,400
Core Damage Frequency and
Large Early Release Frequency.

145
00:06:43,400 --> 00:06:46,640
All the fancy probability
fault trees and everything

146
00:06:46,640 --> 00:06:48,500
goes into calculating
the probability

147
00:06:48,500 --> 00:06:50,300
that the core gets damaged.

148
00:06:50,300 --> 00:06:52,280
So that could be an
accident in one right.

149
00:06:52,280 --> 00:06:54,380
Or the probability of a
radioactivity release.

150
00:06:54,380 --> 00:06:56,163
And that is an accident.

151
00:06:56,163 --> 00:06:57,580
So if no one's
ever heard of this,

152
00:06:57,580 --> 00:06:59,920
there's a city in Russia--

153
00:06:59,920 --> 00:07:01,990
I don't know why it says
Russland, maybe came

154
00:07:01,990 --> 00:07:04,390
from a different language--

155
00:07:04,390 --> 00:07:06,310
called Kyshtym, where
they had the Mayak

156
00:07:06,310 --> 00:07:08,970
nuclear and reprocessing plant.

157
00:07:08,970 --> 00:07:12,010
And there was a tank
full of radioactive waste

158
00:07:12,010 --> 00:07:13,450
that was exploded.

159
00:07:13,450 --> 00:07:17,140
It was a chemical explosion,
but full of strontium,

160
00:07:17,140 --> 00:07:19,210
all sorts of other
radionuclides that

161
00:07:19,210 --> 00:07:22,270
blew up with about
100 tons worth of TNT,

162
00:07:22,270 --> 00:07:25,360
and ended up contaminating
a rather large area

163
00:07:25,360 --> 00:07:27,700
with this plume called the--

164
00:07:27,700 --> 00:07:30,600
I think it's called the East
Chelyabinsk Radioactive Trace--

165
00:07:30,600 --> 00:07:31,370
or the--

166
00:07:31,370 --> 00:07:31,870
what is it?

167
00:07:31,870 --> 00:07:35,380
The south-- South-something
Urals Radioactive Trace.

168
00:07:35,380 --> 00:07:37,960
And that area is still
contaminated today,

169
00:07:37,960 --> 00:07:41,260
because the disaster was
covered up, or rather wasn't--

170
00:07:41,260 --> 00:07:42,430
nothing was said.

171
00:07:42,430 --> 00:07:44,290
These towns here, they didn't--

172
00:07:44,290 --> 00:07:47,913
weren't actually towns back
in 1957 when this happened.

173
00:07:47,913 --> 00:07:49,330
They were just
given designations,

174
00:07:49,330 --> 00:07:52,660
like Chelyabinsk-40
or Chelyabinsk-65,

175
00:07:52,660 --> 00:07:56,110
because the largest nearby
city was Chelyabinsk,

176
00:07:56,110 --> 00:07:58,360
and the villages nearby
were just numbered.

177
00:07:58,360 --> 00:08:01,540
So that was just the post code
for the secret nuclear city.

178
00:08:01,540 --> 00:08:05,412
The US had a few, Russia
had something like 120.

179
00:08:05,412 --> 00:08:06,870
And they still have
a lot of cities

180
00:08:06,870 --> 00:08:11,070
where entry is restricted, or
it's still awfully difficult

181
00:08:11,070 --> 00:08:11,580
to go there.

182
00:08:11,580 --> 00:08:14,250
Like when you have to declare
where in Russia are you going

183
00:08:14,250 --> 00:08:16,320
to get a visa, if you
say one of these cities,

184
00:08:16,320 --> 00:08:18,693
there's going to
be some questions.

185
00:08:18,693 --> 00:08:19,860
And this is where I'm going.

186
00:08:19,860 --> 00:08:22,175
AUDIENCE: To one
of those cities.

187
00:08:22,175 --> 00:08:23,550
MICHAEL SHORT:
Best possible logo

188
00:08:23,550 --> 00:08:28,080
for a conference being held
in Siberia in February.

189
00:08:28,080 --> 00:08:29,148
Right on the end--

190
00:08:29,148 --> 00:08:30,690
right on the edge
in this town called

191
00:08:30,690 --> 00:08:33,780
Kyshtym, the nearest
town to the Mayak plant.

192
00:08:33,780 --> 00:08:35,220
So I'll be taking my camera.

193
00:08:35,220 --> 00:08:37,090
I don't know if I'll
be allowed to use it,

194
00:08:37,090 --> 00:08:38,971
but we're going to
find out anyway.

195
00:08:38,971 --> 00:08:40,304
It's being held in a sanatorium.

196
00:08:40,304 --> 00:08:43,130
And does anyone know
what a sanatorium is?

197
00:08:43,130 --> 00:08:45,260
Like, I'm honestly
asking a question.

198
00:08:45,260 --> 00:08:46,940
I don't know what
a sanatorium is

199
00:08:46,940 --> 00:08:49,370
or why the nuclear conference
is being held there.

200
00:08:49,370 --> 00:08:52,060
But it should be pretty cool.

201
00:08:52,060 --> 00:08:55,090
So yeah, Siberia in February,
right near the South Urals

202
00:08:55,090 --> 00:08:57,520
Radioactive Trace,
should be interesting.

203
00:08:57,520 --> 00:08:59,960
Those of the first group
of folks that were exposed

204
00:08:59,960 --> 00:09:03,010
were the people painting
radium watch dials.

205
00:09:03,010 --> 00:09:05,140
And the reason radium
was so damaging is

206
00:09:05,140 --> 00:09:08,410
because radium is in the same
column of the periodic table

207
00:09:08,410 --> 00:09:09,580
as calcium.

208
00:09:09,580 --> 00:09:11,290
It's a bone-seeking element.

209
00:09:11,290 --> 00:09:12,790
So which of the
tissues do you think

210
00:09:12,790 --> 00:09:17,350
would be most damaged
by ingestion of radium?

211
00:09:17,350 --> 00:09:18,240
AUDIENCE: The bones.

212
00:09:18,240 --> 00:09:20,290
MICHAEL SHORT: Bones-- what
part of the bone, specifically?

213
00:09:20,290 --> 00:09:21,257
AUDIENCE: The marrow.

214
00:09:21,257 --> 00:09:22,340
MICHAEL SHORT: The marrow.

215
00:09:22,340 --> 00:09:24,440
The rapidly dividing
part of the bones.

216
00:09:24,440 --> 00:09:27,110
If you remember from the--

217
00:09:27,110 --> 00:09:29,420
I don't have it on
this presentation,

218
00:09:29,420 --> 00:09:33,260
but the relative tissue
factors for different tissues,

219
00:09:33,260 --> 00:09:35,900
the hard part of
the bone is a 0.01.

220
00:09:35,900 --> 00:09:37,880
It's basically like
a nobody cares.

221
00:09:37,880 --> 00:09:39,680
Bone marrow, however,
is a different story,

222
00:09:39,680 --> 00:09:42,740
because it's always rapidly
dividing, producing red blood

223
00:09:42,740 --> 00:09:45,490
cells, platelets, lymphocytes.

224
00:09:45,490 --> 00:09:49,460
It's making your blood, the
solid portion of your blood.

225
00:09:49,460 --> 00:09:52,160
And so it's a pretty
important tissue.

226
00:09:52,160 --> 00:09:54,440
So you get radium--

227
00:09:54,440 --> 00:09:56,450
anyone also know, what
does radium tend to emit?

228
00:09:59,940 --> 00:10:02,262
Which kind of particles?

229
00:10:02,262 --> 00:10:03,190
AUDIENCE: Alphas.

230
00:10:03,190 --> 00:10:04,940
MICHAEL SHORT: If you have to
take a guess-- yeah, alphas.

231
00:10:04,940 --> 00:10:06,500
It's a pretty heavy element.

232
00:10:06,500 --> 00:10:07,880
It emits alphas.

233
00:10:07,880 --> 00:10:11,450
And alphas have that radiation
quality factor of 20,

234
00:10:11,450 --> 00:10:13,620
meaning alphas have
very short range,

235
00:10:13,620 --> 00:10:15,710
but they're the most
damaging type of radiation

236
00:10:15,710 --> 00:10:16,880
when ingested.

237
00:10:16,880 --> 00:10:18,210
So this was really bad news.

238
00:10:18,210 --> 00:10:20,870
There was a lot of incidents
of illness and cancer

239
00:10:20,870 --> 00:10:23,330
from folks painting
radium watch dials.

240
00:10:23,330 --> 00:10:25,980
And then the first data
from bones after death,

241
00:10:25,980 --> 00:10:28,310
because there were a lot
of those, established,

242
00:10:28,310 --> 00:10:31,040
how much radium were you
allowed to get exposed to?

243
00:10:31,040 --> 00:10:34,580
And this came out to about
0.6 milligray per week.

244
00:10:34,580 --> 00:10:36,080
Anyone have any
idea what that would

245
00:10:36,080 --> 00:10:38,060
be in millisieverts per week?

246
00:10:38,060 --> 00:10:41,810
With a quality factor
of 20 and a bone marrow

247
00:10:41,810 --> 00:10:46,888
factor of about 0.12?

248
00:10:46,888 --> 00:10:48,750
AUDIENCE: 1.73?

249
00:10:48,750 --> 00:10:49,680
MICHAEL SHORT: Yeah.

250
00:10:49,680 --> 00:10:54,740
On the order of like singles
of millisieverts per week.

251
00:10:54,740 --> 00:10:55,340
Not bad.

252
00:10:55,340 --> 00:10:56,965
Anyone know how much
dose you typically

253
00:10:56,965 --> 00:10:59,880
get in a year in background?

254
00:10:59,880 --> 00:11:00,380
Yeah?

255
00:11:00,380 --> 00:11:01,280
AUDIENCE: A few.

256
00:11:01,280 --> 00:11:03,030
MICHAEL SHORT: A few
millisieverts a year.

257
00:11:03,030 --> 00:11:03,810
Yeah.

258
00:11:03,810 --> 00:11:06,390
So this was the first
occupational safety

259
00:11:06,390 --> 00:11:08,070
limit for radiation risk.

260
00:11:08,070 --> 00:11:11,130
It is-- actually, it comes out
to larger than 50 millisieverts

261
00:11:11,130 --> 00:11:14,250
per year, which is what the
normal occupational workers are

262
00:11:14,250 --> 00:11:15,090
allowed.

263
00:11:15,090 --> 00:11:16,900
How about you radiation workers?

264
00:11:16,900 --> 00:11:17,910
What's your limit?

265
00:11:17,910 --> 00:11:18,900
AUDIENCE: 5 rem.

266
00:11:18,900 --> 00:11:20,950
MICHAEL SHORT: 5 rem,
which comes out to?

267
00:11:20,950 --> 00:11:22,545
AUDIENCE: Like 50
millisieverts--

268
00:11:22,545 --> 00:11:23,320
MICHAEL SHORT: 50
millisieverts per year.

269
00:11:23,320 --> 00:11:24,060
OK, there you go.

270
00:11:26,630 --> 00:11:28,633
Large population
sizes that do exist

271
00:11:28,633 --> 00:11:30,050
that get a whole
lot of radiation,

272
00:11:30,050 --> 00:11:33,500
however, is anyone that
smokes an anything,

273
00:11:33,500 --> 00:11:35,210
because when you take
plant matter, which

274
00:11:35,210 --> 00:11:37,520
has a high surface
area, concentrate it,

275
00:11:37,520 --> 00:11:40,817
so anything that it brings up
from the roots in the soil,

276
00:11:40,817 --> 00:11:42,650
or that settles out on
the leaves in the air

277
00:11:42,650 --> 00:11:45,050
gets concentrated
in the dry fraction,

278
00:11:45,050 --> 00:11:46,730
and then gets
burned and inhaled.

279
00:11:46,730 --> 00:11:50,630
A lot of those heavy metals that
are radon byproducts and such

280
00:11:50,630 --> 00:11:52,100
are fairly reactive.

281
00:11:52,100 --> 00:11:53,990
They'll stick around
in your tissues

282
00:11:53,990 --> 00:11:55,910
and give you a whole
lot of alpha dose.

283
00:11:55,910 --> 00:11:58,280
So when you have
populations of people

284
00:11:58,280 --> 00:12:00,650
who have or haven't
smoked, you actually

285
00:12:00,650 --> 00:12:03,830
can figure out the number
of extra attributable deaths

286
00:12:03,830 --> 00:12:06,110
to things like indoor
radon, depending

287
00:12:06,110 --> 00:12:10,150
on if you live in a
smoky atmosphere or not.

288
00:12:10,150 --> 00:12:12,640
And so to distinguish the
types of biological effects

289
00:12:12,640 --> 00:12:14,970
that we're worried about,
we can group these into two.

290
00:12:14,970 --> 00:12:17,380
There's short-term effects,
which manifest themselves

291
00:12:17,380 --> 00:12:19,270
in hours, days, or weeks.

292
00:12:19,270 --> 00:12:20,632
We'll call that immediate.

293
00:12:20,632 --> 00:12:22,090
And then there's
long-term effects,

294
00:12:22,090 --> 00:12:26,620
which tend to manifest in
shortest, years, and longest,

295
00:12:26,620 --> 00:12:28,410
decades.

296
00:12:28,410 --> 00:12:31,500
So things like acute
radiation sickness

297
00:12:31,500 --> 00:12:35,550
is due to rapid cell death of a
few different kinds over time.

298
00:12:35,550 --> 00:12:38,410
And which kind depends
on the route of exposure,

299
00:12:38,410 --> 00:12:40,620
the isotope, the
type of radiation,

300
00:12:40,620 --> 00:12:43,002
and the total amount of
dose to those tissues.

301
00:12:43,002 --> 00:12:44,460
And if you guys
have all-- what are

302
00:12:44,460 --> 00:12:46,750
some of the symptoms of
acute radiation sickness?

303
00:12:46,750 --> 00:12:48,750
Like, did anyone read
what happened to the folks

304
00:12:48,750 --> 00:12:50,832
in the demon core?

305
00:12:50,832 --> 00:12:52,290
AUDIENCE: That
their hair fell out.

306
00:12:52,290 --> 00:12:53,498
MICHAEL SHORT: Hair fell out.

307
00:12:53,498 --> 00:12:54,420
What else?

308
00:12:54,420 --> 00:12:55,740
AUDIENCE: They vomit.

309
00:12:55,740 --> 00:12:57,038
MICHAEL SHORT: Vomiting.

310
00:12:57,038 --> 00:12:57,830
AUDIENCE: Diarrhea.

311
00:12:57,830 --> 00:12:59,220
MICHAEL SHORT: Diarrhea.

312
00:12:59,220 --> 00:13:01,320
All the fun ones, yeah.

313
00:13:01,320 --> 00:13:03,210
Well, we'll explain why
these sorts of things

314
00:13:03,210 --> 00:13:05,830
happen with acute
radiation exposure.

315
00:13:05,830 --> 00:13:08,850
Now if you don't get that
much radiation exposure,

316
00:13:08,850 --> 00:13:10,410
but you do get enough
to mutate cells

317
00:13:10,410 --> 00:13:13,260
you have what's called
delayed somatic effects,

318
00:13:13,260 --> 00:13:14,820
anything from cancer,
to straight up

319
00:13:14,820 --> 00:13:16,770
mutations, to birth defects.

320
00:13:16,770 --> 00:13:20,040
Any sort of permanent and
reproducible modification

321
00:13:20,040 --> 00:13:23,480
to a cell's DNA that
can induce mutations.

322
00:13:23,480 --> 00:13:25,480
So let's first talk about
the short-term effects

323
00:13:25,480 --> 00:13:27,760
because they're a little
easier to understand.

324
00:13:27,760 --> 00:13:30,940
And because the doses were much
higher, you don't need as much

325
00:13:30,940 --> 00:13:34,870
of a population size in order
to figure out, did this affect--

326
00:13:34,870 --> 00:13:37,130
did this amount of
dose have an effect?

327
00:13:37,130 --> 00:13:39,790
So for things up to
a quarter of a gray,

328
00:13:39,790 --> 00:13:40,960
pretty much nothing happens.

329
00:13:40,960 --> 00:13:43,180
That's quite a toasty dose.

330
00:13:43,180 --> 00:13:46,090
For gammas, that would be
like getting five times

331
00:13:46,090 --> 00:13:50,990
your occupational yearly
limit instantaneously.

332
00:13:50,990 --> 00:13:51,490
Yeah.

333
00:13:51,490 --> 00:13:53,440
This is not something
you'd want to happen.

334
00:13:53,440 --> 00:13:56,680
But it's not going to cause
any significant ill effects.

335
00:13:56,680 --> 00:14:00,010
Up to a gray, you'll start
to see a few symptoms,

336
00:14:00,010 --> 00:14:02,540
like nausea and anorexia.

337
00:14:02,540 --> 00:14:04,180
They probably tend
to go together.

338
00:14:04,180 --> 00:14:06,790
If you're feeling
gastrointestinally horrible,

339
00:14:06,790 --> 00:14:08,830
you probably don't
want to eat much.

340
00:14:08,830 --> 00:14:11,260
And you will see things
like bone marrow damage,

341
00:14:11,260 --> 00:14:13,730
like we talked about
with the radium workers.

342
00:14:13,730 --> 00:14:16,150
Fewer red and white blood
cells, less platelets,

343
00:14:16,150 --> 00:14:18,400
also means easier to bleed.

344
00:14:18,400 --> 00:14:20,350
So a lot of the effects
of radiation damage

345
00:14:20,350 --> 00:14:23,380
are not primary,
they're secondary.

346
00:14:23,380 --> 00:14:25,540
Just like most radiation
damage to cells

347
00:14:25,540 --> 00:14:28,950
itself is not damage
to the DNA, but it's

348
00:14:28,950 --> 00:14:32,410
radiolysis of the water nearby
the DNA, and eventual chemical

349
00:14:32,410 --> 00:14:36,600
migration to cause damage
to the DNA chemically.

350
00:14:36,600 --> 00:14:39,090
In this case, it's not
like radiation takes out

351
00:14:39,090 --> 00:14:40,500
your platelets.

352
00:14:40,500 --> 00:14:42,690
Radiation takes out
the cells that create

353
00:14:42,690 --> 00:14:44,580
the platelets, the bone marrow.

354
00:14:44,580 --> 00:14:47,070
Meaning that platelets, if
they live about three weeks,

355
00:14:47,070 --> 00:14:48,870
you'll tend to see a
drop in platelet count

356
00:14:48,870 --> 00:14:51,930
when your production
system gets lower.

357
00:14:51,930 --> 00:14:56,160
This should sound strikingly
similar to series radioactive

358
00:14:56,160 --> 00:14:59,580
decay because the same equations
can be used to model it.

359
00:14:59,580 --> 00:15:02,937
Let's say you have a normal,
stable platelet count.

360
00:15:02,937 --> 00:15:04,520
Eh, I'm not going
to get on the board.

361
00:15:04,520 --> 00:15:06,960
I told you guys we wouldn't
get to derivey anymore.

362
00:15:06,960 --> 00:15:09,780
But you've got some
source of platelets, which

363
00:15:09,780 --> 00:15:10,947
would be your bone marrow.

364
00:15:10,947 --> 00:15:12,780
And you've got some
sink of platelets, which

365
00:15:12,780 --> 00:15:14,050
would be normal cell death.

366
00:15:14,050 --> 00:15:17,670
So let's say there's a half-life
or a lifetime of platelets.

367
00:15:17,670 --> 00:15:19,380
If you kill a little
bit of the source,

368
00:15:19,380 --> 00:15:21,427
then you'll see the
sink start to decay.

369
00:15:21,427 --> 00:15:23,010
But the source will
start to grow back

370
00:15:23,010 --> 00:15:24,810
over time from cell division.

371
00:15:24,810 --> 00:15:27,260
And you'll see the
level pop back up again.

372
00:15:27,260 --> 00:15:29,850
And you can model it
with the same first-order

373
00:15:29,850 --> 00:15:32,460
linear ordinary
differential equations.

374
00:15:32,460 --> 00:15:35,198
Same ODEs as series
radioactive decay,

375
00:15:35,198 --> 00:15:36,990
you can use to guess
how many platelets you

376
00:15:36,990 --> 00:15:42,340
should have in your body at any
time following a certain dose.

377
00:15:42,340 --> 00:15:45,340
1 to 3 grays is when
things get bad from-- go

378
00:15:45,340 --> 00:15:47,350
to bed from worse pretty quick.

379
00:15:47,350 --> 00:15:50,770
Nausea, anorexia,
and infection--

380
00:15:50,770 --> 00:15:53,740
tell me, why do you
think infection results

381
00:15:53,740 --> 00:15:56,460
from radiation damage?

382
00:15:56,460 --> 00:15:56,960
Yeah.

383
00:15:56,960 --> 00:15:58,212
Let's hear everything, yeah.

384
00:15:58,212 --> 00:15:59,420
Front to back, let's hear it.

385
00:15:59,420 --> 00:16:00,890
AUDIENCE: I was saying
the immune system

386
00:16:00,890 --> 00:16:03,250
is most likely compromised
because of bone marrow being

387
00:16:03,250 --> 00:16:03,808
compromised.

388
00:16:03,808 --> 00:16:04,600
MICHAEL SHORT: Yep.

389
00:16:04,600 --> 00:16:06,230
The immune system's compromised.

390
00:16:06,230 --> 00:16:07,220
What else?

391
00:16:07,220 --> 00:16:07,970
AUDIENCE: You're--

392
00:16:07,970 --> 00:16:08,865
AUDIENCE: [INAUDIBLE]

393
00:16:08,865 --> 00:16:10,710
MICHAEL SHORT: Is everyone
going to say the same thing?

394
00:16:10,710 --> 00:16:11,210
OK.

395
00:16:11,210 --> 00:16:12,660
I have another story.

396
00:16:12,660 --> 00:16:14,090
So I agree with you guys.

397
00:16:14,090 --> 00:16:18,510
But it also has to do
with these platelets.

398
00:16:18,510 --> 00:16:22,170
Anytime anything happens to
you ever, cells tend to die.

399
00:16:22,170 --> 00:16:24,618
You clap your hands, you
probably kill a few cells.

400
00:16:24,618 --> 00:16:26,910
You bump into something, you
probably kill a few cells.

401
00:16:26,910 --> 00:16:28,980
You swallow some
metal shavings, you're

402
00:16:28,980 --> 00:16:30,750
going to kill a lot of cells.

403
00:16:30,750 --> 00:16:32,820
But your body has
got mucous membranes,

404
00:16:32,820 --> 00:16:35,640
and all sorts of things,
and platelets in order

405
00:16:35,640 --> 00:16:37,920
to repair that damage.

406
00:16:37,920 --> 00:16:41,010
All of a sudden, if your
blood thins out, and can

407
00:16:41,010 --> 00:16:42,600
start leaking from
different places,

408
00:16:42,600 --> 00:16:45,060
or it's a lot harder to
repair like physical leaks

409
00:16:45,060 --> 00:16:48,025
in your body,
bacteria can get in.

410
00:16:48,025 --> 00:16:49,650
So the normal amount
of bacteria you're

411
00:16:49,650 --> 00:16:52,235
exposed to every day,
which is enormous--

412
00:16:52,235 --> 00:16:53,610
there's theorized
to be something

413
00:16:53,610 --> 00:16:55,470
like 10 times as
many bacteria cells

414
00:16:55,470 --> 00:16:57,730
in your body as human cells.

415
00:16:57,730 --> 00:16:59,370
They're all over the place.

416
00:16:59,370 --> 00:17:01,003
They're just a lot smaller.

417
00:17:01,003 --> 00:17:03,420
Well, they can get into places
that they wouldn't normally

418
00:17:03,420 --> 00:17:03,930
get in.

419
00:17:03,930 --> 00:17:06,359
So what would
normally be a pinprick

420
00:17:06,359 --> 00:17:09,510
in a simple immune response,
with a suppressed immune system

421
00:17:09,510 --> 00:17:11,910
and a lower platelet count,
becomes a much more dangerous

422
00:17:11,910 --> 00:17:12,510
thing.

423
00:17:12,510 --> 00:17:14,940
You could undergo
something called sepsis.

424
00:17:14,940 --> 00:17:17,339
That's basically blood
turning to sewage because you

425
00:17:17,339 --> 00:17:19,410
get a massive blood infection.

426
00:17:19,410 --> 00:17:22,170
This is, again let's say, a
secondary or even a tertiary

427
00:17:22,170 --> 00:17:25,060
effect, but very real.

428
00:17:25,060 --> 00:17:27,234
Hematologic damage more severe--

429
00:17:27,234 --> 00:17:29,680
hema refers to blood.

430
00:17:29,680 --> 00:17:31,660
That's basically
saying the same thing.

431
00:17:31,660 --> 00:17:34,480
Recovery probable,
though not assured.

432
00:17:34,480 --> 00:17:38,402
Why probable, and
why not assured?

433
00:17:38,402 --> 00:17:40,265
AUDIENCE: Everybody
reacts differently.

434
00:17:40,265 --> 00:17:41,390
MICHAEL SHORT: That's true.

435
00:17:41,390 --> 00:17:42,950
Everyone reacts differently.

436
00:17:42,950 --> 00:17:45,320
It also matters how
much treatment you get.

437
00:17:45,320 --> 00:17:48,020
So if you get a crazy
compromised immune system,

438
00:17:48,020 --> 00:17:50,690
we have hospitals,
and sterile bubbles,

439
00:17:50,690 --> 00:17:52,800
and all sorts of things
that you can be put in.

440
00:17:52,800 --> 00:17:55,670
But if you don't get
to a hospital in time

441
00:17:55,670 --> 00:17:58,910
to reduce the onset
of massive infection,

442
00:17:58,910 --> 00:18:00,770
that's what could happen.

443
00:18:00,770 --> 00:18:03,070
Then you go higher 3
to 6 gray, everything

444
00:18:03,070 --> 00:18:08,180
as above, plus diarrhea,
depilation, hair loss,

445
00:18:08,180 --> 00:18:09,530
temporary sterility.

446
00:18:09,530 --> 00:18:12,740
Think the temporary
sterility one's obvious.

447
00:18:12,740 --> 00:18:15,320
Why do you think diarrhea
and hair loss would occur?

448
00:18:18,520 --> 00:18:20,420
AUDIENCE: Isn't it like
the fact that your--

449
00:18:20,420 --> 00:18:22,760
the cells of your
like intestines--

450
00:18:22,760 --> 00:18:27,410
then you can't like hold it
in anymore because the damage.

451
00:18:27,410 --> 00:18:28,370
MICHAEL SHORT: Yeah.

452
00:18:28,370 --> 00:18:30,020
Exactly.

453
00:18:30,020 --> 00:18:32,030
The most sensitive
cells are the ones

454
00:18:32,030 --> 00:18:35,300
that are rapidly dividing
to make villi and stem cells

455
00:18:35,300 --> 00:18:36,500
in your intestines.

456
00:18:36,500 --> 00:18:40,190
Hair follicles, gonads, anything
that's dividing all the time,

457
00:18:40,190 --> 00:18:42,860
is going to feel the
effects of radiation damage

458
00:18:42,860 --> 00:18:44,240
much more severely.

459
00:18:44,240 --> 00:18:46,460
And barring any mutation,
which may take a long time

460
00:18:46,460 --> 00:18:49,310
to manifest, the wrong
damage to DNA, and the cell

461
00:18:49,310 --> 00:18:50,420
just can't divide.

462
00:18:50,420 --> 00:18:51,860
So it dies.

463
00:18:51,860 --> 00:18:54,050
And if those cells
die, then that

464
00:18:54,050 --> 00:18:56,150
means that you can't
uptake nutrition.

465
00:18:56,150 --> 00:19:00,990
And your body just flushes
everything out in diarrhea.

466
00:19:00,990 --> 00:19:03,330
Fatalities will occur in
the range of 3 and 1/2

467
00:19:03,330 --> 00:19:05,370
gray without treatment.

468
00:19:05,370 --> 00:19:07,650
And this is what's
called the typical LD50.

469
00:19:07,650 --> 00:19:09,648
Does anyone know
what an LD50 is?

470
00:19:09,648 --> 00:19:11,652
AUDIENCE: The lethal dose.

471
00:19:11,652 --> 00:19:13,110
MICHAEL SHORT: The
lethal dose for?

472
00:19:13,110 --> 00:19:14,460
AUDIENCE: 50% of the population.

473
00:19:14,460 --> 00:19:15,335
MICHAEL SHORT: Right.

474
00:19:15,335 --> 00:19:20,010
So about 50% of the people
exposed to 3.5 gray will die.

475
00:19:20,010 --> 00:19:22,630
This doesn't take into account
difference in treatment,

476
00:19:22,630 --> 00:19:24,947
difference in person, or
everything, it's altogether.

477
00:19:24,947 --> 00:19:27,030
And I'll go into what an
LD50 for different things

478
00:19:27,030 --> 00:19:28,140
is in a second.

479
00:19:28,140 --> 00:19:32,940
And then over 6 gray, you
get immediate incapacitation.

480
00:19:32,940 --> 00:19:33,960
Hits the nervous system.

481
00:19:33,960 --> 00:19:35,790
You get so many
cells leaking out

482
00:19:35,790 --> 00:19:38,670
that the chemical signals
for your neurons, sodium,

483
00:19:38,670 --> 00:19:39,960
and potassium, and other ions.

484
00:19:39,960 --> 00:19:41,982
Well, if all your
cells die and leak out,

485
00:19:41,982 --> 00:19:43,440
then all of a sudden
you're flooded

486
00:19:43,440 --> 00:19:46,020
with the ions that are
normally kept in a very

487
00:19:46,020 --> 00:19:48,510
careful equilibrium to signal.

488
00:19:48,510 --> 00:19:50,670
So you can actually get
sudden unconsciousness

489
00:19:50,670 --> 00:19:52,890
in a matter of seconds to
minutes from doses over 10

490
00:19:52,890 --> 00:19:54,000
gray.

491
00:19:54,000 --> 00:19:55,860
So you just-- you just
go out like a light,

492
00:19:55,860 --> 00:19:58,720
like that, and may not recover.

493
00:19:58,720 --> 00:20:00,340
What's an LD50?

494
00:20:00,340 --> 00:20:04,210
It's the-- it's whenever
an effect gets an onset

495
00:20:04,210 --> 00:20:05,770
by 50% of the population.

496
00:20:05,770 --> 00:20:08,680
And there are different
something-something 50 doses,

497
00:20:08,680 --> 00:20:11,920
depending on, let's say, whether
something's therapeutic, toxic,

498
00:20:11,920 --> 00:20:12,970
or lethal.

499
00:20:12,970 --> 00:20:16,231
The example I like
to give is selenium.

500
00:20:16,231 --> 00:20:20,080
Does anyone know anything
about selenium in the diet?

501
00:20:20,080 --> 00:20:23,440
It's one of those trace minerals
that you need to survive,

502
00:20:23,440 --> 00:20:25,648
but can also kill you.

503
00:20:25,648 --> 00:20:27,190
If you need to get,
about on average,

504
00:20:27,190 --> 00:20:29,620
5 micrograms of
selenium in order

505
00:20:29,620 --> 00:20:32,570
to produce certain enzymes that
keep things going in the body.

506
00:20:32,570 --> 00:20:34,540
5 micrograms is not a lot.

507
00:20:34,540 --> 00:20:37,510
But you know that in order to
have a little bit of selenium,

508
00:20:37,510 --> 00:20:39,280
it's got a therapeutic effect.

509
00:20:39,280 --> 00:20:40,840
Once you get around
5 micrograms,

510
00:20:40,840 --> 00:20:44,425
most people will see some
sort of biological benefit.

511
00:20:44,425 --> 00:20:48,390
If you get 5 milligrams,
starts to become toxic.

512
00:20:48,390 --> 00:20:50,650
And this is the case with
pretty much anything.

513
00:20:50,650 --> 00:20:53,520
Vitamins-- anyone ever had--

514
00:20:53,520 --> 00:20:55,200
this is probably
going to be a no--

515
00:20:55,200 --> 00:20:57,590
anyone ever eaten raw
seal liver before?

516
00:20:57,590 --> 00:20:58,910
Or polar bear livers?

517
00:20:58,910 --> 00:20:59,680
I don't know.

518
00:20:59,680 --> 00:21:01,450
No one's gone up,
way, way up north?

519
00:21:01,450 --> 00:21:02,510
AUDIENCE: Vitamin C.

520
00:21:02,510 --> 00:21:03,790
MICHAEL SHORT: Anyone--
do you know why?

521
00:21:03,790 --> 00:21:04,382
Or--

522
00:21:04,382 --> 00:21:06,110
AUDIENCE: Because they
have too much vitamin A--

523
00:21:06,110 --> 00:21:07,027
MICHAEL SHORT: Indeed.

524
00:21:07,027 --> 00:21:10,150
Vitamin A, something that you
need a whole lot to survive.

525
00:21:10,150 --> 00:21:12,310
It's so concentrated
in the livers the seals

526
00:21:12,310 --> 00:21:14,978
and polar bears that if you were
to just eat a polar bear liver,

527
00:21:14,978 --> 00:21:16,520
you would die of
vitamin A poisoning.

528
00:21:16,520 --> 00:21:17,740
[INTERPOSING VOICES]

529
00:21:17,740 --> 00:21:18,823
AUDIENCE: --you'd be dead.

530
00:21:18,823 --> 00:21:21,198
MICHAEL SHORT: So I didn't
hear all those things at once.

531
00:21:21,198 --> 00:21:22,010
One of the time.

532
00:21:22,010 --> 00:21:24,460
AUDIENCE: If anyone ever offers
you that, you just say no.

533
00:21:24,460 --> 00:21:26,460
MICHAEL SHORT: Just
take a little taste.

534
00:21:26,460 --> 00:21:28,480
You know, it's all
about the amount, right?

535
00:21:28,480 --> 00:21:29,572
What were you guys saying?

536
00:21:29,572 --> 00:21:31,739
AUDIENCE: If we had eaten
it, wouldn't we have died?

537
00:21:31,739 --> 00:21:32,739
MICHAEL SHORT: Well, no.

538
00:21:32,739 --> 00:21:34,560
It's not like you take
a taste and you die.

539
00:21:34,560 --> 00:21:36,880
Again, it's all about
the amount of exposure.

540
00:21:36,880 --> 00:21:39,580
One little taste is not going to
flood your system with vitamin

541
00:21:39,580 --> 00:21:41,498
A. But you eat an entire
polar bears liver,

542
00:21:41,498 --> 00:21:42,790
you're going to have a bad day.

543
00:21:42,790 --> 00:21:45,140
AUDIENCE: Why does it
have so much vitamin A?

544
00:21:45,140 --> 00:21:45,530
MICHAEL SHORT: Wait, what?

545
00:21:45,530 --> 00:21:47,245
AUDIENCE: Why does it
have so much vitamin A?

546
00:21:47,245 --> 00:21:49,578
MICHAEL SHORT: I don't know
why polar bears have so much

547
00:21:49,578 --> 00:21:53,150
vitamin A. No idea, actually.

548
00:21:53,150 --> 00:21:55,640
But then beyond that, you
can get lethal effects,

549
00:21:55,640 --> 00:21:58,220
where you might get sick from
eating too much of something.

550
00:21:58,220 --> 00:22:00,475
But then again, you know--

551
00:22:00,475 --> 00:22:01,850
anyone ever heard
of the old hold

552
00:22:01,850 --> 00:22:04,050
your wee for a Wii contest?

553
00:22:04,050 --> 00:22:08,300
Where we found out
really the LD50 of water?

554
00:22:08,300 --> 00:22:08,800
Yeah.

555
00:22:08,800 --> 00:22:12,130
So you drink way too much water
without any other solutes,

556
00:22:12,130 --> 00:22:14,680
you deplete your body
from electrolytes.

557
00:22:14,680 --> 00:22:17,170
And then you can also die.

558
00:22:17,170 --> 00:22:19,750
So I ran into this
experience personally.

559
00:22:19,750 --> 00:22:21,250
I don't have to ask
any of you guys.

560
00:22:21,250 --> 00:22:23,290
I went hiking with
my dad in Nepal,

561
00:22:23,290 --> 00:22:25,910
in 2009, and the last
vacation I've taken--

562
00:22:25,910 --> 00:22:27,280
that's a long time ago.

563
00:22:27,280 --> 00:22:28,030
It's kind of cool.

564
00:22:28,030 --> 00:22:29,488
At MIT, it's fun
enough here that I

565
00:22:29,488 --> 00:22:31,960
haven't felt like I've
needed a vacation in, what,

566
00:22:31,960 --> 00:22:33,800
like seven years?

567
00:22:33,800 --> 00:22:35,530
I'm actually kind of
taking one this year

568
00:22:35,530 --> 00:22:37,030
because I'm going
somewhere for research

569
00:22:37,030 --> 00:22:38,080
and just sticking around.

570
00:22:38,080 --> 00:22:40,820
But we went hiking in Nepal
I eat something I probably

571
00:22:40,820 --> 00:22:41,320
shouldn't.

572
00:22:41,320 --> 00:22:43,653
In fact, everyone eventually
ate something they probably

573
00:22:43,653 --> 00:22:44,500
shouldn't.

574
00:22:44,500 --> 00:22:47,050
And I had what
could be described

575
00:22:47,050 --> 00:22:48,610
as massive GI syndrome--

576
00:22:48,610 --> 00:22:51,820
Delhi belly, whatever
you wanted to call it.

577
00:22:51,820 --> 00:22:54,400
My brother likes to call
it poop and mouth disease,

578
00:22:54,400 --> 00:22:58,580
because sanitation and
stuff is not the best there.

579
00:22:58,580 --> 00:23:00,790
And so I was in a
pretty bad state.

580
00:23:00,790 --> 00:23:03,490
And instead of drinking water
to replenish all of the water

581
00:23:03,490 --> 00:23:06,460
that was leaving out of every
direction from the body,

582
00:23:06,460 --> 00:23:07,750
drinking saltwater.

583
00:23:07,750 --> 00:23:11,110
We took tablets that had the
same isotonic concentration

584
00:23:11,110 --> 00:23:15,460
of electrolytes, amino acids,
as those being lost by the body,

585
00:23:15,460 --> 00:23:17,110
because when water
goes in the body,

586
00:23:17,110 --> 00:23:19,300
everything osmotically
equilibrates.

587
00:23:19,300 --> 00:23:22,335
If you take in
lots of pure water,

588
00:23:22,335 --> 00:23:23,710
it will-- a little
bit of sodium,

589
00:23:23,710 --> 00:23:27,040
potassium, other electrolytes
will dissolve into that water.

590
00:23:27,040 --> 00:23:29,650
If it's going out
in any direction,

591
00:23:29,650 --> 00:23:32,450
it's going to leave your body,
depleting you of electrolytes.

592
00:23:32,450 --> 00:23:34,600
So I had seven wonderful
days lying in bed,

593
00:23:34,600 --> 00:23:37,900
drinking about a liter of warm
salt water every 15 minutes

594
00:23:37,900 --> 00:23:40,930
or so in order to maintain
not just the water,

595
00:23:40,930 --> 00:23:44,990
but the electrolytes
that your body needed.

596
00:23:44,990 --> 00:23:45,548
Freaky, huh?

597
00:23:45,548 --> 00:23:47,090
AUDIENCE: Sounds
like a fun vacation.

598
00:23:47,090 --> 00:23:48,965
MICHAEL SHORT: Yeah, it
was a great vacation.

599
00:23:48,965 --> 00:23:51,420
Is there any wonder why I
don't want to take another one?

600
00:23:51,420 --> 00:23:54,700
If I go back there, I'm
having nothing but Clif bars.

601
00:23:54,700 --> 00:23:57,200
It's hard to say no when folks
that live up in the mountains

602
00:23:57,200 --> 00:23:58,742
offer you what little
food they have,

603
00:23:58,742 --> 00:24:02,010
but you should really say
no for your own safety.

604
00:24:02,010 --> 00:24:05,150
Anyway, yeah, there's
an LD50 for water--

605
00:24:05,150 --> 00:24:08,120
by any mechanism, from
electrolyte depletion

606
00:24:08,120 --> 00:24:10,430
to-- there was a
contest on the radio

607
00:24:10,430 --> 00:24:11,750
called hold your wee for a Wii.

608
00:24:11,750 --> 00:24:13,500
When the Nintendo Wii
came out, they said,

609
00:24:13,500 --> 00:24:16,760
how much water could you drink
without going to the bathroom?

610
00:24:16,760 --> 00:24:18,656
And someone's bladder exploded.

611
00:24:18,656 --> 00:24:20,600
AUDIENCE: Like
literally exploded?

612
00:24:20,600 --> 00:24:20,730
MICHAEL SHORT: Yeah.

613
00:24:20,730 --> 00:24:21,597
That's what I heard.

614
00:24:21,597 --> 00:24:23,180
Either it would be
a bladder explosion

615
00:24:23,180 --> 00:24:24,570
or an electrolyte depletion.

616
00:24:24,570 --> 00:24:26,900
So whatever the
mechanism, the LD50

617
00:24:26,900 --> 00:24:30,015
just tells if somebody--
if a population ingests

618
00:24:30,015 --> 00:24:31,640
a certain amount of
something, or takes

619
00:24:31,640 --> 00:24:33,710
in a certain amount
of radiation,

620
00:24:33,710 --> 00:24:36,140
how much will cause 50% to die.

621
00:24:36,140 --> 00:24:39,380
Or for much lower
doses, 50% will

622
00:24:39,380 --> 00:24:42,980
see some therapeutic
effect by any mechanism.

623
00:24:42,980 --> 00:24:45,190
It doesn't distinguish
by mechanism.

624
00:24:45,190 --> 00:24:47,860
So the four phases of
radiation damage, this

625
00:24:47,860 --> 00:24:50,990
is where all those Latin and
bio roots really come in handy.

626
00:24:50,990 --> 00:24:53,230
The prodromal phase is
the initial symptoms

627
00:24:53,230 --> 00:24:58,000
of exposure, which may or may
not happen one to three days

628
00:24:58,000 --> 00:24:59,410
after exposure.

629
00:24:59,410 --> 00:25:01,588
For massive exposure,
you're not going

630
00:25:01,588 --> 00:25:03,130
to see this, because
you're not going

631
00:25:03,130 --> 00:25:05,020
to live one to three days.

632
00:25:05,020 --> 00:25:07,420
For very minor exposure,
you may not even

633
00:25:07,420 --> 00:25:12,880
see these prodromal effects,
like a drop in blood cell

634
00:25:12,880 --> 00:25:15,550
count, or GI syndrome,
because the dose might not

635
00:25:15,550 --> 00:25:19,300
be severe enough for your body
not to be able to cope with it.

636
00:25:19,300 --> 00:25:21,190
The latent phase this,
is the tricky one.

637
00:25:21,190 --> 00:25:24,790
An apparent recovery from
the prodromal systems.

638
00:25:24,790 --> 00:25:26,950
So getting a medium dose
of radiation-- let's call,

639
00:25:26,950 --> 00:25:28,720
that like 2 to 5 gray--

640
00:25:28,720 --> 00:25:31,320
will cause some nausea,
vomiting, and headache.

641
00:25:31,320 --> 00:25:33,150
And then you get better.

642
00:25:33,150 --> 00:25:37,390
And then you get worse in
the manifest illness phase,

643
00:25:37,390 --> 00:25:39,730
because a lot of the things
that radiation will do

644
00:25:39,730 --> 00:25:41,410
can be immediate.

645
00:25:41,410 --> 00:25:45,520
If you suddenly cause the
body to release serotonin

646
00:25:45,520 --> 00:25:47,770
and induce the
vomiting reflex, that

647
00:25:47,770 --> 00:25:50,455
goes away once that serotonin
is consumed or dealt with.

648
00:25:50,455 --> 00:25:52,330
I don't know how the
body would deal with it.

649
00:25:52,330 --> 00:25:54,430
And you might think
you're getting better.

650
00:25:54,430 --> 00:25:55,960
But the cells that
divide rapidly

651
00:25:55,960 --> 00:25:57,790
have still incurred that damage.

652
00:25:57,790 --> 00:26:00,400
And you won't see that damage
until they fail to divide

653
00:26:00,400 --> 00:26:02,510
in their normal amount of time.

654
00:26:02,510 --> 00:26:05,350
So things like GI
syndrome and hair loss

655
00:26:05,350 --> 00:26:07,750
might not show up for
a few days afterwards,

656
00:26:07,750 --> 00:26:10,720
because it's not like your hair
will just instantly fall out,

657
00:26:10,720 --> 00:26:13,570
like there's some cell that is
holding onto your hair follicle

658
00:26:13,570 --> 00:26:15,950
and then will just release
it when irradiated.

659
00:26:15,950 --> 00:26:17,980
But those follicles
won't continue

660
00:26:17,980 --> 00:26:20,260
to produce the keratin
at the same rate,

661
00:26:20,260 --> 00:26:23,140
or in a different way, or I
can't speak that intelligently

662
00:26:23,140 --> 00:26:26,440
about exactly the
mechanism of hair loss,

663
00:26:26,440 --> 00:26:28,900
but it will take a little
bit of time to get there.

664
00:26:28,900 --> 00:26:30,470
And the final phase is a binary.

665
00:26:30,470 --> 00:26:32,860
Do you recover or do you die?

666
00:26:32,860 --> 00:26:36,420
Could take days, to months,
to years to figure that out.

667
00:26:36,420 --> 00:26:37,820
And these weren't
in the reading,

668
00:26:37,820 --> 00:26:40,640
but I wanted to pull some
much better tables about what

669
00:26:40,640 --> 00:26:44,270
happens in each of these phases
as a function of radiation

670
00:26:44,270 --> 00:26:45,200
dose.

671
00:26:45,200 --> 00:26:46,750
So when does vomiting onset?

672
00:26:46,750 --> 00:26:49,200
There are actually
patterns to be seen here.

673
00:26:49,200 --> 00:26:53,270
So for mild, it may take a
couple of hours after exposure.

674
00:26:53,270 --> 00:26:55,670
You may not stimulate
the immediate release

675
00:26:55,670 --> 00:26:57,560
of the hormones that
induce vomiting.

676
00:26:57,560 --> 00:26:59,570
But then as the dose gets
more and more severe,

677
00:26:59,570 --> 00:27:03,690
could be anywhere from hours
to less than 10 minutes.

678
00:27:03,690 --> 00:27:08,550
So you can use the onset of
things like vomiting, diarrhea,

679
00:27:08,550 --> 00:27:12,230
headache, loss of
consciousness in severe cases,

680
00:27:12,230 --> 00:27:13,970
to gauge the amount
of dose someone

681
00:27:13,970 --> 00:27:16,340
has absorbed in some
unknown accident.

682
00:27:16,340 --> 00:27:18,590
Because it's not like if
you're in some severe nuclear

683
00:27:18,590 --> 00:27:20,990
accident, and you don't
happened to be wearing

684
00:27:20,990 --> 00:27:23,570
a very large range
dosimeter, how do you

685
00:27:23,570 --> 00:27:24,950
know how much dose you've got?

686
00:27:24,950 --> 00:27:28,070
And how do you know how
to treat the person?

687
00:27:28,070 --> 00:27:30,410
Time can be your
best weapon there,

688
00:27:30,410 --> 00:27:33,860
because except for
very lethal doses,

689
00:27:33,860 --> 00:27:36,620
where you could go unconscious
in seconds or minutes,

690
00:27:36,620 --> 00:27:38,900
you've got some
time-- hours to days--

691
00:27:38,900 --> 00:27:40,640
to treat what happened.

692
00:27:40,640 --> 00:27:43,220
And if you can say, all right,
I know the time of exposure,

693
00:27:43,220 --> 00:27:45,770
and I know the time
of onset of headache,

694
00:27:45,770 --> 00:27:49,010
of diarrhea, of vomiting,
you can figure out, roughly

695
00:27:49,010 --> 00:27:52,160
maybe within plus or minus a
gray, how much dose you had

696
00:27:52,160 --> 00:27:53,303
and what to treat.

697
00:27:53,303 --> 00:27:55,220
There are probably smarter
ways of doing this,

698
00:27:55,220 --> 00:27:58,160
but with nothing else,
you've got time as a variable

699
00:27:58,160 --> 00:28:00,720
to help you figure this out.

700
00:28:00,720 --> 00:28:04,460
Why do you guys think that your
body temperature would go up

701
00:28:04,460 --> 00:28:08,780
upon exposure to huge
amounts of radiation?

702
00:28:08,780 --> 00:28:10,400
What's with the fever?

703
00:28:10,400 --> 00:28:12,545
What is the fever a response to?

704
00:28:12,545 --> 00:28:14,787
Or could it be a response to?

705
00:28:14,787 --> 00:28:15,620
AUDIENCE: Infection.

706
00:28:15,620 --> 00:28:16,980
MICHAEL SHORT: Infection.

707
00:28:16,980 --> 00:28:19,070
So any sort of sudden
massive infection

708
00:28:19,070 --> 00:28:21,140
would mount an immune response.

709
00:28:21,140 --> 00:28:23,030
And that would cause
a fever because you've

710
00:28:23,030 --> 00:28:25,820
got all sorts of cells
doing things, expending

711
00:28:25,820 --> 00:28:28,730
energy, trying to rid your
body of the infection.

712
00:28:28,730 --> 00:28:29,300
What else?

713
00:28:34,723 --> 00:28:37,960
That's OK, something for you
to read up on for the-- not

714
00:28:37,960 --> 00:28:38,470
for the--

715
00:28:38,470 --> 00:28:39,780
for the practice homework.

716
00:28:39,780 --> 00:28:41,530
The one that I can't
make due because it's

717
00:28:41,530 --> 00:28:43,960
after the last day of classes.

718
00:28:43,960 --> 00:28:46,460
What about-- let's see--

719
00:28:46,460 --> 00:28:49,220
headache, I don't think
we've explained that well.

720
00:28:49,220 --> 00:28:51,560
We'll get into the
diarrhea stuff.

721
00:28:51,560 --> 00:28:54,020
Let's go into the latent phase.

722
00:28:54,020 --> 00:28:55,470
What tends to happen?

723
00:28:55,470 --> 00:28:57,860
Well, looks like you get
better, but blood work

724
00:28:57,860 --> 00:28:59,590
will tell you otherwise.

725
00:28:59,590 --> 00:29:01,250
And you can then
tell how much dose

726
00:29:01,250 --> 00:29:04,070
you were exposed to after
a certain amount of time

727
00:29:04,070 --> 00:29:07,010
by things like lymphocyte
and granulocyte count,

728
00:29:07,010 --> 00:29:09,740
different immune system
blood cells, also platelets,

729
00:29:09,740 --> 00:29:11,450
also all sorts of other things.

730
00:29:11,450 --> 00:29:14,960
You can tell by a drop in
certain blood cell levels

731
00:29:14,960 --> 00:29:16,830
how much dose you've had.

732
00:29:16,830 --> 00:29:18,950
And you can sustain
a certain drop

733
00:29:18,950 --> 00:29:21,860
in platelets and immune cells
without any ill effects.

734
00:29:21,860 --> 00:29:25,070
Something like 30% to 40% of
your platelets could go away,

735
00:29:25,070 --> 00:29:26,780
you're not a
hemophiliac, temporarily.

736
00:29:26,780 --> 00:29:28,130
You're still going to be OK.

737
00:29:28,130 --> 00:29:30,470
You can form blood
clots in result--

738
00:29:30,470 --> 00:29:32,940
what is it-- response to
a nosebleed or a bruise,

739
00:29:32,940 --> 00:29:35,420
and these things aren't
going to be life-threatening.

740
00:29:35,420 --> 00:29:39,500
Diarrhea, for low doses,
you don't really get any.

741
00:29:39,500 --> 00:29:42,320
So it looks like intestinal
cells may be a little bit more

742
00:29:42,320 --> 00:29:44,720
robust than bone marrow.

743
00:29:44,720 --> 00:29:47,570
Except with really
severe doses, you'll

744
00:29:47,570 --> 00:29:51,660
start to see that pop up once
those cells fail to divide.

745
00:29:51,660 --> 00:29:54,890
Once, let's say, the
existing villi die off,

746
00:29:54,890 --> 00:29:57,170
new ones don't replace them,
and you lose your ability

747
00:29:57,170 --> 00:29:59,080
to uptake nutrition.

748
00:29:59,080 --> 00:30:01,640
And then depilation, hair loss.

749
00:30:01,640 --> 00:30:03,015
Beginning on day
15 or later, you

750
00:30:03,015 --> 00:30:04,515
might think you're
out of the woods,

751
00:30:04,515 --> 00:30:06,823
and then all of a sudden,
your hair starts to fall out.

752
00:30:06,823 --> 00:30:08,990
And that'll help tell you
about how much dose you've

753
00:30:08,990 --> 00:30:10,430
had once again.

754
00:30:10,430 --> 00:30:11,930
And then the
critical phase, what

755
00:30:11,930 --> 00:30:15,500
happens when things go from
bad, to better, to worse?

756
00:30:15,500 --> 00:30:17,520
How quickly does this happen?

757
00:30:17,520 --> 00:30:20,060
You tend to get things
like infections,

758
00:30:20,060 --> 00:30:24,470
more severe infections,
disorientation.

759
00:30:24,470 --> 00:30:28,892
On longer times, like seven
days, your platelet count--

760
00:30:28,892 --> 00:30:31,690
it's pretty
proportional to dose.

761
00:30:31,690 --> 00:30:35,260
Same thing with the number of
lymphocytes, lower, and lower,

762
00:30:35,260 --> 00:30:36,190
and lower.

763
00:30:36,190 --> 00:30:38,643
And then the onset time
is smaller and smaller.

764
00:30:38,643 --> 00:30:40,060
And then you can
see the lethality

765
00:30:40,060 --> 00:30:41,518
of these different
doses, depending

766
00:30:41,518 --> 00:30:44,440
on the person, the treatments,
the susceptibility,

767
00:30:44,440 --> 00:30:45,940
any sort of
pre-existing conditions,

768
00:30:45,940 --> 00:30:46,982
which you might not know.

769
00:30:46,982 --> 00:30:47,950
Do you have a question?

770
00:30:47,950 --> 00:30:48,575
AUDIENCE: Yeah.

771
00:30:48,575 --> 00:30:51,678
I was going to ask,
for cancer patients,

772
00:30:51,678 --> 00:30:53,470
when you hear about
them losing their hair,

773
00:30:53,470 --> 00:30:57,853
are they actually getting doses
in like the 2 to 4 gray range?

774
00:30:57,853 --> 00:30:59,020
MICHAEL SHORT: Cancer, yeah.

775
00:30:59,020 --> 00:31:00,730
AUDIENCE: Because
it's so concentrated.

776
00:31:00,730 --> 00:31:03,250
MICHAEL SHORT: Radiation
doses are pretty intense.

777
00:31:03,250 --> 00:31:05,343
So the dose to the
tumor, for example,

778
00:31:05,343 --> 00:31:07,510
in proton therapy, which
is the only one I've really

779
00:31:07,510 --> 00:31:09,880
read about, can be in
the kilogray level.

780
00:31:09,880 --> 00:31:13,420
But the idea there is you fry
the tumor, you kill it soon.

781
00:31:13,420 --> 00:31:16,420
Like you go beyond the
lethal dose for those

782
00:31:16,420 --> 00:31:19,900
cells, while inducing
much less damage

783
00:31:19,900 --> 00:31:22,168
in the rest of the
surrounding person.

784
00:31:22,168 --> 00:31:23,710
And that's the nice
quirk of protons,

785
00:31:23,710 --> 00:31:26,480
is you can do that in
a very narrow range.

786
00:31:26,480 --> 00:31:29,320
The straggle on 250
MeV proton beams

787
00:31:29,320 --> 00:31:33,370
is on the order of like,
microns, less than millimeters,

788
00:31:33,370 --> 00:31:34,960
which is pretty cool.

789
00:31:34,960 --> 00:31:38,680
But a lot of the hair loss can
come from the chemotherapy.

790
00:31:38,680 --> 00:31:42,610
Chemotherapy is better
known as poison.

791
00:31:42,610 --> 00:31:46,138
It's just a poison that affects
tumor cells slightly more

792
00:31:46,138 --> 00:31:47,680
strongly than the
rest of your cells.

793
00:31:47,680 --> 00:31:49,570
But it is nasty stuff.

794
00:31:49,570 --> 00:31:53,250
And it's the chemo that can
cause the hair loss as well.

795
00:31:53,250 --> 00:31:54,010
Yeah.

796
00:31:54,010 --> 00:31:56,950
So would you attribute the hair
loss to radiation or to chemo?

797
00:31:56,950 --> 00:31:59,290
I would say chances are
it's chemo, depending

798
00:31:59,290 --> 00:32:00,340
on where the tumor is.

799
00:32:00,340 --> 00:32:02,860
I mean, if you have a
localized proton beam coming in

800
00:32:02,860 --> 00:32:05,020
to treat a tumor
there or there, you're

801
00:32:05,020 --> 00:32:07,650
not going to get much
hair loss up here.

802
00:32:07,650 --> 00:32:10,560
But chemo penetrates
throughout the whole body.

803
00:32:10,560 --> 00:32:13,050
As far as if you're getting
X-ray therapy of a brain tumor,

804
00:32:13,050 --> 00:32:14,910
that I don't know.

805
00:32:14,910 --> 00:32:16,590
I really haven't
looked into that.

806
00:32:16,590 --> 00:32:17,730
So good question.

807
00:32:20,500 --> 00:32:23,770
And then the time and
severity of these symptoms.

808
00:32:23,770 --> 00:32:26,440
Well, this is something I'd like
you guys to read on your own,

809
00:32:26,440 --> 00:32:28,065
because it's tons of
words on a screen.

810
00:32:28,065 --> 00:32:30,190
But it's something
I suggest you read.

811
00:32:30,190 --> 00:32:32,390
It's not done that
carefully in the reading,

812
00:32:32,390 --> 00:32:36,490
which is why I provided it
here for you in the slides.

813
00:32:36,490 --> 00:32:40,510
And then going on to what
these radiation symptoms mean,

814
00:32:40,510 --> 00:32:43,030
I wanted to translate a
little bit of the Latin,

815
00:32:43,030 --> 00:32:45,670
Greek, whatever, roots into
something you can understand.

816
00:32:45,670 --> 00:32:49,840
These hematopoietic symptoms--
anything to do with the blood,

817
00:32:49,840 --> 00:32:52,210
decreased platelets,
immune suppression,

818
00:32:52,210 --> 00:32:53,180
all that kind of stuff.

819
00:32:53,180 --> 00:32:56,410
And the origin is the stem
cell system in your bone marrow

820
00:32:56,410 --> 00:32:58,390
breaks down and you
don't make as much

821
00:32:58,390 --> 00:33:01,600
of all the components of
blood as you normally should.

822
00:33:01,600 --> 00:33:04,300
The gastrointestinal
comes from the stem cells

823
00:33:04,300 --> 00:33:06,070
in the villi, those
high surface area

824
00:33:06,070 --> 00:33:08,170
structures in your
intestines that

825
00:33:08,170 --> 00:33:11,170
absorb the nutrition, which
are also normally covered

826
00:33:11,170 --> 00:33:13,240
in a thick layer of
mucus to keep all

827
00:33:13,240 --> 00:33:14,980
the bacteria from getting out.

828
00:33:14,980 --> 00:33:16,780
Because nutrients,
like, let's say,

829
00:33:16,780 --> 00:33:19,900
minerals or small proteins,
are a hell of a lot

830
00:33:19,900 --> 00:33:23,560
smaller than bacteria, they
can diffuse or transport

831
00:33:23,560 --> 00:33:24,930
through the mucus much faster.

832
00:33:24,930 --> 00:33:28,970
So you can uptake the nutrition
and not let the bad stuff in.

833
00:33:28,970 --> 00:33:31,150
And the neuro or
cerebrovascular stuff

834
00:33:31,150 --> 00:33:34,220
is straight up blasting
of endothelial cells.

835
00:33:34,220 --> 00:33:36,400
Your, let's say-- yeah--

836
00:33:36,400 --> 00:33:38,080
I think that's skin cells.

837
00:33:38,080 --> 00:33:41,080
A term called edema,
which is fluid leakage.

838
00:33:41,080 --> 00:33:44,200
Has anyone ever seen pictures
of folks with massive edema

839
00:33:44,200 --> 00:33:44,740
in the legs?

840
00:33:44,740 --> 00:33:46,698
Like, folks that, let's
say, haven't gotten out

841
00:33:46,698 --> 00:33:49,810
of bed for years and their
legs swell up like this?

842
00:33:49,810 --> 00:33:52,240
That's just fluid leaking
into the intracellular spaces.

843
00:33:52,240 --> 00:33:53,113
I'd say take a look.

844
00:33:53,113 --> 00:33:55,030
I don't think I'm going
to show pictures of it

845
00:33:55,030 --> 00:33:56,870
because it's kind of
nasty on the screen.

846
00:33:56,870 --> 00:33:59,240
But if you want to know
what edema looks like,

847
00:33:59,240 --> 00:34:00,490
then I suggest you look it up.

848
00:34:00,490 --> 00:34:05,100
There's plenty of horrific
stuff on Google Images.

849
00:34:05,100 --> 00:34:08,969
And so what happens in
these hematopoietic cells?

850
00:34:08,969 --> 00:34:12,630
About 1 gray can knock
out about a third

851
00:34:12,630 --> 00:34:16,290
of your bone marrow cells,
and that's actually OK,

852
00:34:16,290 --> 00:34:20,159
because those surviving cells
are redividing quite quickly.

853
00:34:20,159 --> 00:34:22,409
And that means that you won't
have that much of a drop

854
00:34:22,409 --> 00:34:24,929
in blood cells, because let's
say you kill off a bunch

855
00:34:24,929 --> 00:34:28,183
of the bone marrow cells ,
but they redivide in a shorter

856
00:34:28,183 --> 00:34:30,600
lifetime than, let's say, the
red blood cells or platelets

857
00:34:30,600 --> 00:34:31,320
live.

858
00:34:31,320 --> 00:34:34,770
You're not going to see that
much of a dip in the blood cell

859
00:34:34,770 --> 00:34:37,440
levels, which are ultimately
your main line of defense

860
00:34:37,440 --> 00:34:39,530
against sepsis.

861
00:34:39,530 --> 00:34:42,380
Things like destruction of
bone marrow, yeah that would--

862
00:34:42,380 --> 00:34:44,713
that would be a bad thing.

863
00:34:44,713 --> 00:34:46,130
There's a whole
lot of words here.

864
00:34:46,130 --> 00:34:47,755
I'd say this is better
for you to read.

865
00:34:47,755 --> 00:34:50,510
I want to go through an
explanation of some pictures

866
00:34:50,510 --> 00:34:52,969
of what tends to happen
to, in this case,

867
00:34:52,969 --> 00:34:57,230
mouse bone marrow tissue
after a lethal dose, 9.5 gray.

868
00:34:57,230 --> 00:34:59,630
That's what it looks
like beforehand.

869
00:34:59,630 --> 00:35:02,390
That's what you're left with,
is very, very few cells.

870
00:35:02,390 --> 00:35:05,540
So that would be definitely
what a lethal dose looks like,

871
00:35:05,540 --> 00:35:08,480
because the ability to make
all the things that bone

872
00:35:08,480 --> 00:35:13,450
marrow makes has been almost
eliminated in this tissue.

873
00:35:13,450 --> 00:35:16,430
So a visual of what these
sorts of things look like.

874
00:35:16,430 --> 00:35:18,700
For the gastrointestinal
systems--

875
00:35:18,700 --> 00:35:20,990
I'm going to skip right
ahead and show you

876
00:35:20,990 --> 00:35:25,202
what healthy and irradiated
villi tend to look like.

877
00:35:25,202 --> 00:35:26,660
So I've been-- does
anyone not know

878
00:35:26,660 --> 00:35:29,680
what I mean when I say villi?

879
00:35:29,680 --> 00:35:30,280
OK, good.

880
00:35:30,280 --> 00:35:32,740
So the little high
surface area structures

881
00:35:32,740 --> 00:35:34,810
in your intestine
that are normally

882
00:35:34,810 --> 00:35:37,420
great absorbers of nutrition,
mostly due to their surface

883
00:35:37,420 --> 00:35:39,700
area, but also due
to their structure

884
00:35:39,700 --> 00:35:41,580
and their biological function.

885
00:35:41,580 --> 00:35:45,650
And you tend to kill those off
with a fair bit of radiation.

886
00:35:45,650 --> 00:35:48,580
So this is what it looks like
after four days, and seven

887
00:35:48,580 --> 00:35:50,680
days, and then 12 days.

888
00:35:50,680 --> 00:35:52,115
Things can recover.

889
00:35:52,115 --> 00:35:54,490
As long as you don't kill all
the cells, they will divide

890
00:35:54,490 --> 00:35:55,960
and they will reconquer.

891
00:35:55,960 --> 00:35:57,850
And if the organism
can live long enough

892
00:35:57,850 --> 00:36:00,790
to allow for that natural
healing to take place,

893
00:36:00,790 --> 00:36:03,700
then you can survive an
acute dose of radiation.

894
00:36:03,700 --> 00:36:06,160
So when we talk about why do
you need hospital treatment,

895
00:36:06,160 --> 00:36:10,300
it's basically to stand in for
your body's normal functions

896
00:36:10,300 --> 00:36:12,850
while your body regenerates
those functions.

897
00:36:12,850 --> 00:36:17,432
But for extremely severe cases--
let's go back to that table

898
00:36:17,432 --> 00:36:18,890
of how many, let's
say, leukocytes,

899
00:36:18,890 --> 00:36:21,080
or what not you have--
or lymphocytes--

900
00:36:21,080 --> 00:36:22,520
if you get down
to the zero level,

901
00:36:22,520 --> 00:36:24,920
you've completely knocked
out your body's ability

902
00:36:24,920 --> 00:36:26,240
to produce those.

903
00:36:26,240 --> 00:36:28,490
You might have a few
cells left here or there.

904
00:36:28,490 --> 00:36:30,800
But at that point, there's
not much anyone can do

905
00:36:30,800 --> 00:36:34,592
but make you comfortable.

906
00:36:34,592 --> 00:36:36,800
And then in this case, I
think this was a human one--

907
00:36:36,800 --> 00:36:38,270
yeah, OK.

908
00:36:38,270 --> 00:36:40,250
So a healthy intestine
from a human.

909
00:36:40,250 --> 00:36:45,080
It's got a rather small whatever
that part is in the submucosa

910
00:36:45,080 --> 00:36:45,800
level.

911
00:36:45,800 --> 00:36:48,500
Lots of villi, lots
of surface area.

912
00:36:48,500 --> 00:36:51,080
After radiation damage, when
you have massive cell death,

913
00:36:51,080 --> 00:36:54,060
notice that the structures
out here are pretty much gone.

914
00:36:54,060 --> 00:36:56,930
And there's a lot of
scarring or-- what's

915
00:36:56,930 --> 00:36:59,240
the word that they use?

916
00:36:59,240 --> 00:37:01,250
Severe fibrosis.

917
00:37:01,250 --> 00:37:03,500
Why would your body make
scar tissue in response

918
00:37:03,500 --> 00:37:04,640
to radiation damage?

919
00:37:11,080 --> 00:37:14,490
So anytime your body senses that
a whole lot of cells are dying,

920
00:37:14,490 --> 00:37:17,412
it's going to respond
by attempting to repair.

921
00:37:17,412 --> 00:37:19,870
So like if you get, let's say,
a small bit of surgery done,

922
00:37:19,870 --> 00:37:21,537
you could be left
with some scar tissue.

923
00:37:21,537 --> 00:37:24,520
That's cells that have died,
and when those cell contents

924
00:37:24,520 --> 00:37:28,340
leak out, they signal to the
nearby cells, fix something.

925
00:37:28,340 --> 00:37:30,340
I can't speak any more
intelligently about that,

926
00:37:30,340 --> 00:37:31,750
but the body does.

927
00:37:31,750 --> 00:37:35,170
And scar tissue is not what
you want in your intestines

928
00:37:35,170 --> 00:37:37,460
because that interferes with--

929
00:37:37,460 --> 00:37:37,960
what is it?

930
00:37:37,960 --> 00:37:39,700
Nutrition uptake
as well as killing

931
00:37:39,700 --> 00:37:42,950
the structures that are doing
that uptake to begin with.

932
00:37:42,950 --> 00:37:45,560
Then there's the
neurovascular stuff.

933
00:37:45,560 --> 00:37:48,650
Massive cell death from a
huge amount of absorbed energy

934
00:37:48,650 --> 00:37:52,190
can just cause those
cells to die and leak out,

935
00:37:52,190 --> 00:37:53,750
causing a lot of edema.

936
00:37:53,750 --> 00:37:56,990
That can cause a drop in blood
pressure, which is also not

937
00:37:56,990 --> 00:37:57,773
good for you.

938
00:37:57,773 --> 00:38:00,440
This could be part of what leads
to some of the unconsciousness.

939
00:38:00,440 --> 00:38:03,260
If you have a drop in blood
pressure due to any reason,

940
00:38:03,260 --> 00:38:05,630
then that can make
you go unconscious.

941
00:38:05,630 --> 00:38:09,380
And there's pretty much not a
prodromal or a latent phase.

942
00:38:09,380 --> 00:38:11,293
If you hit the
neurovascular syndrome,

943
00:38:11,293 --> 00:38:13,460
you're pretty much going
to go to the critical phase

944
00:38:13,460 --> 00:38:15,020
right away, within
seconds, minutes,

945
00:38:15,020 --> 00:38:18,266
or small number of hours.

946
00:38:18,266 --> 00:38:22,600
Here's another question,
why the skin lesions?

947
00:38:22,600 --> 00:38:26,100
Because mature skin cells
live about three weeks.

948
00:38:26,100 --> 00:38:29,010
If you kill off the skin
cells in the dividing layer,

949
00:38:29,010 --> 00:38:32,040
and you don't reform new ones,
and those skin cells die,

950
00:38:32,040 --> 00:38:34,950
you end up with the
grossest word in this class,

951
00:38:34,950 --> 00:38:37,490
moist desquamation.

952
00:38:37,490 --> 00:38:39,140
It kind of sounds
like what it is.

953
00:38:39,140 --> 00:38:41,570
That's like
sloughing off of skin

954
00:38:41,570 --> 00:38:44,120
and leaving open
sores because you

955
00:38:44,120 --> 00:38:47,450
don't have the ability to
regenerate that skin, which

956
00:38:47,450 --> 00:38:50,240
is normally your first line
of defense to everything,

957
00:38:50,240 --> 00:38:51,650
and you've got
fluid leaking out.

958
00:38:51,650 --> 00:38:55,850
And it's just-- yeah--
it's moist desquamation.

959
00:38:55,850 --> 00:38:56,840
Why the vomiting?

960
00:38:56,840 --> 00:39:00,207
Well, this question hasn't
been fully answered yet.

961
00:39:00,207 --> 00:39:02,540
As far as back when I've
looked at the literature around

962
00:39:02,540 --> 00:39:06,740
to 2011, there is a hypothesis
that intestinal cells

963
00:39:06,740 --> 00:39:10,790
will secrete serotonin in
certain conditions, including

964
00:39:10,790 --> 00:39:13,280
when they start dying,
which would then stimulate

965
00:39:13,280 --> 00:39:17,000
a center in your medulla, the
sort of automatic reflex center

966
00:39:17,000 --> 00:39:19,910
of the brain, to
induce vomiting.

967
00:39:19,910 --> 00:39:21,600
Why might this be a good thing?

968
00:39:21,600 --> 00:39:23,120
We're not talking about
radiation, but why would

969
00:39:23,120 --> 00:39:24,912
you want to stimulate
this vomiting reflex?

970
00:39:27,111 --> 00:39:28,778
AUDIENCE: In case
whatever's going wrong

971
00:39:28,778 --> 00:39:30,200
is because of something you ate.

972
00:39:30,200 --> 00:39:31,033
MICHAEL SHORT: Yeah.

973
00:39:31,033 --> 00:39:34,360
So let's say you eat
a wet aged steak.

974
00:39:34,360 --> 00:39:37,327
You know, something that's
left out on the table,

975
00:39:37,327 --> 00:39:39,410
or in the fridge, or let's
say, behind the fridge,

976
00:39:39,410 --> 00:39:41,820
or left to marinate in the sun.

977
00:39:41,820 --> 00:39:43,830
And you eat it,
and those bacteria

978
00:39:43,830 --> 00:39:45,570
start killing everything.

979
00:39:45,570 --> 00:39:47,250
If those cells in
your intestine die,

980
00:39:47,250 --> 00:39:49,230
they've got to send
some signal far away

981
00:39:49,230 --> 00:39:53,400
to the brain to tell you to get
everything out of the stomach.

982
00:39:53,400 --> 00:39:54,600
And that's what happens.

983
00:39:54,600 --> 00:39:58,080
So the body has developed
these long distance hormonal

984
00:39:58,080 --> 00:40:00,690
signaling mechanisms
to say, something

985
00:40:00,690 --> 00:40:03,330
is going wrong,
expel everything,

986
00:40:03,330 --> 00:40:05,250
because it's
probably bad for you.

987
00:40:05,250 --> 00:40:07,740
So radiation damage to these
cells, which will kill them,

988
00:40:07,740 --> 00:40:09,900
may trigger the same effects.

989
00:40:09,900 --> 00:40:12,690
If those cells have little
pockets or organelles that

990
00:40:12,690 --> 00:40:15,750
contain these hormones
and cause instantaneous

991
00:40:15,750 --> 00:40:19,350
secretion by cell death, that
might do the same thing, too.

992
00:40:19,350 --> 00:40:22,410
But as far as this
paper, it's a hypothesis.

993
00:40:22,410 --> 00:40:25,020
It's not necessarily proven.

994
00:40:25,020 --> 00:40:28,350
But it does correlate inversely
with the amount of time

995
00:40:28,350 --> 00:40:30,900
to vomiting, in terms of
dose and time to vomiting.

996
00:40:30,900 --> 00:40:33,400
So that much we do know.

997
00:40:33,400 --> 00:40:36,067
And then onto the
long-term effects.

998
00:40:36,067 --> 00:40:37,650
There's two that are
really important,

999
00:40:37,650 --> 00:40:40,470
is cancer risk and
birth defect risk.

1000
00:40:40,470 --> 00:40:44,490
You won't tend to see this
happen, despite popular media.

1001
00:40:44,490 --> 00:40:47,580
But you will see a lot
of bad stuff happen.

1002
00:40:47,580 --> 00:40:51,390
These are extremely difficult
to wrap our heads around.

1003
00:40:51,390 --> 00:40:54,960
And the reason for that is
the population size required

1004
00:40:54,960 --> 00:40:58,530
in order to do a proper
study with proper statistics,

1005
00:40:58,530 --> 00:41:01,770
and give confidence to
the saying, let's say,

1006
00:41:01,770 --> 00:41:04,200
a dose-- in order to,
let's say, a dose of 1

1007
00:41:04,200 --> 00:41:07,170
milligray would have some
amount of excess risk,

1008
00:41:07,170 --> 00:41:11,540
you'd need to expose
61.8 million people,

1009
00:41:11,540 --> 00:41:15,720
plus a similarly sized control
to distinguish whether or not

1010
00:41:15,720 --> 00:41:19,447
0.1 milligray has an
additional amount of risk.

1011
00:41:19,447 --> 00:41:21,030
So let's say for
gammas to whole body,

1012
00:41:21,030 --> 00:41:23,850
what's 0.1 milligray in
terms of increased risk

1013
00:41:23,850 --> 00:41:24,960
dose in sieverts--

1014
00:41:27,600 --> 00:41:28,905
sorry-- 1 milligray?

1015
00:41:31,880 --> 00:41:33,740
1 millisievert.

1016
00:41:33,740 --> 00:41:37,220
Tissue factor is 1, gamma
radiation quality factor

1017
00:41:37,220 --> 00:41:39,590
is 1, that's 1 millisievert.

1018
00:41:39,590 --> 00:41:43,190
That's 20 years of exposure--
or 20 years of allowed exposure

1019
00:41:43,190 --> 00:41:44,570
at the same time.

1020
00:41:44,570 --> 00:41:46,940
Or 10 years of exposure
at the same time,

1021
00:41:46,940 --> 00:41:51,620
where 100 microsievert exposure
at once has been said to say,

1022
00:41:51,620 --> 00:41:55,730
maybe that's the onset of
detectable amount of damage.

1023
00:41:55,730 --> 00:42:00,290
Pretty difficult, and our
sources of data for these doses

1024
00:42:00,290 --> 00:42:02,900
are a lot smaller--

1025
00:42:02,900 --> 00:42:05,300
with the exception of
very high irradiations

1026
00:42:05,300 --> 00:42:08,400
than we need to make
any real conclusions.

1027
00:42:08,400 --> 00:42:10,700
The largest sample size
we have besides smokers

1028
00:42:10,700 --> 00:42:12,650
would be atomic bomb survivors.

1029
00:42:12,650 --> 00:42:17,930
So folks have followed all of
the survivors of the Hiroshima

1030
00:42:17,930 --> 00:42:19,160
and Nagasaki bombings.

1031
00:42:19,160 --> 00:42:22,820
Not just the people nearby, but
in the surrounding countryside.

1032
00:42:22,820 --> 00:42:25,850
And tried to follow, how many
excess cancers were there

1033
00:42:25,850 --> 00:42:27,830
as a result of the radiation?

1034
00:42:27,830 --> 00:42:30,920
For anyone exposed within 3
kilometers for less than 5

1035
00:42:30,920 --> 00:42:36,000
milligray, you can attribute,
basically, either one or none.

1036
00:42:36,000 --> 00:42:37,830
So by following
this group of people

1037
00:42:37,830 --> 00:42:40,650
and finding out how many of them
got cancer compared to control

1038
00:42:40,650 --> 00:42:43,140
groups, you can
try and figure out,

1039
00:42:43,140 --> 00:42:47,030
how much extra cancer
was due to radiation?

1040
00:42:47,030 --> 00:42:49,040
And to graph this-- this
is actually in the--

1041
00:42:49,040 --> 00:42:51,830
I think the ICRP
publication, graphing

1042
00:42:51,830 --> 00:42:53,810
the amount of relative
risk, or to use

1043
00:42:53,810 --> 00:42:56,780
the words from the last studies
we saw, the Odds Ratio--

1044
00:42:56,780 --> 00:43:00,650
the OR-- of getting
cancer, an odds ratio of 1

1045
00:43:00,650 --> 00:43:03,560
means exactly the same
amount of risk with

1046
00:43:03,560 --> 00:43:05,390
versus without the radiation.

1047
00:43:05,390 --> 00:43:08,628
And the actual raw data
points are plotted here.

1048
00:43:08,628 --> 00:43:10,670
And there's a couple of
lines drawn through here.

1049
00:43:10,670 --> 00:43:12,753
And this is the source of
a lot of the controversy

1050
00:43:12,753 --> 00:43:15,320
behind radiation
damaged nowadays.

1051
00:43:15,320 --> 00:43:20,060
The black line is the LNT, or
the Linear No-Threshold model,

1052
00:43:20,060 --> 00:43:23,420
which is a hypothesis that
says every amount of radiation

1053
00:43:23,420 --> 00:43:27,380
is bad, and it is
linear with dose.

1054
00:43:27,380 --> 00:43:29,210
I, for one, don't
believe this model.

1055
00:43:29,210 --> 00:43:32,090
This is, to me, a
fear-based model.

1056
00:43:32,090 --> 00:43:34,430
It's certainly easy to
make policy based on this,

1057
00:43:34,430 --> 00:43:35,880
because you can--

1058
00:43:35,880 --> 00:43:38,667
I think your average congressman
can understand a linear graph.

1059
00:43:38,667 --> 00:43:40,250
Not sure whether
they could understand

1060
00:43:40,250 --> 00:43:42,410
p-values and statistics.

1061
00:43:42,410 --> 00:43:44,500
But they're-- they
don't have to.

1062
00:43:44,500 --> 00:43:47,600
It's what they ask
scientists to testify about.

1063
00:43:47,600 --> 00:43:49,820
When you look at
the actual data,

1064
00:43:49,820 --> 00:43:51,860
there's this kind
of funky shaped line

1065
00:43:51,860 --> 00:43:54,260
along with plus or minus
1 sigma error bars.

1066
00:43:54,260 --> 00:43:58,580
It doesn't really show a
linear threshold, does it?

1067
00:43:58,580 --> 00:44:01,250
It actually looks like
it might be super linear

1068
00:44:01,250 --> 00:44:03,307
for very small doses.

1069
00:44:03,307 --> 00:44:05,390
And then it tails off, and
then it picks up again.

1070
00:44:05,390 --> 00:44:09,678
But this right here is a
zoom-in of this data rich area

1071
00:44:09,678 --> 00:44:10,220
of the graph.

1072
00:44:10,220 --> 00:44:12,573
It actually looks like
for really high doses,

1073
00:44:12,573 --> 00:44:14,240
it might be a little
super linear again,

1074
00:44:14,240 --> 00:44:16,220
where things get
much, much worse.

1075
00:44:16,220 --> 00:44:18,920
Hopefully you don't have
anyone exposed to, let's say,

1076
00:44:18,920 --> 00:44:22,550
2 gray of dose, but the
real controversy is here,

1077
00:44:22,550 --> 00:44:24,650
in the small dose region.

1078
00:44:24,650 --> 00:44:28,820
We don't really know enough to
say whether very small doses

1079
00:44:28,820 --> 00:44:30,140
are hurtful or not--

1080
00:44:30,140 --> 00:44:31,340
or harmful or not.

1081
00:44:31,340 --> 00:44:34,330
In fact, they might
even be helpful.

1082
00:44:34,330 --> 00:44:36,850
So you guys, I think, were
the first class that I-- no--

1083
00:44:36,850 --> 00:44:38,265
I had you last year-- no.

1084
00:44:38,265 --> 00:44:39,980
You guys remember
the answer to what

1085
00:44:39,980 --> 00:44:42,140
is the idea that a
little bit of radiation

1086
00:44:42,140 --> 00:44:43,920
might be good for you?

1087
00:44:43,920 --> 00:44:46,270
From the cash class?

1088
00:44:46,270 --> 00:44:47,758
Anyone remember
what that's called?

1089
00:44:47,758 --> 00:44:48,550
AUDIENCE: Hormesis?

1090
00:44:48,550 --> 00:44:49,800
MICHAEL SHORT: Hormesis, yeah.

1091
00:44:49,800 --> 00:44:52,570
This idea that a little
bit of something bad

1092
00:44:52,570 --> 00:44:54,220
could actually be good for you.

1093
00:44:54,220 --> 00:44:56,560
This is also a theory,
and to my knowledge,

1094
00:44:56,560 --> 00:44:58,660
has not been proven to be true.

1095
00:44:58,660 --> 00:45:01,940
But it is evident in
some other studies,

1096
00:45:01,940 --> 00:45:05,350
along with different fields
of research beyond radiation.

1097
00:45:05,350 --> 00:45:07,270
For example, there
had been an experiment

1098
00:45:07,270 --> 00:45:10,300
where rats were kept
in shielded lead boxes

1099
00:45:10,300 --> 00:45:12,640
as opposed to just
out on the bench

1100
00:45:12,640 --> 00:45:14,230
where they got less radiation.

1101
00:45:14,230 --> 00:45:16,420
And the rats that
had less radiation

1102
00:45:16,420 --> 00:45:18,650
had less incidence of cancer.

1103
00:45:18,650 --> 00:45:20,770
However, it's
extremely difficult

1104
00:45:20,770 --> 00:45:24,756
to remove all other confounding
variables from this data.

1105
00:45:24,756 --> 00:45:27,720
And that's the trick there,
is when trying to tease out,

1106
00:45:27,720 --> 00:45:30,640
are small amounts of
radiation bad for you?

1107
00:45:30,640 --> 00:45:33,600
You also have to tease
out confounding variables

1108
00:45:33,600 --> 00:45:36,220
or other things that might
be obscuring your data.

1109
00:45:39,090 --> 00:45:40,440
Why the hormetic effect?

1110
00:45:40,440 --> 00:45:42,790
So what are some of
the ideas behind why

1111
00:45:42,790 --> 00:45:45,120
hormesis might happen?

1112
00:45:45,120 --> 00:45:47,990
So there are some theories,
and some controlled studies

1113
00:45:47,990 --> 00:45:50,930
showing that if you
irradiate cells very lightly,

1114
00:45:50,930 --> 00:45:52,820
they mount an immune response.

1115
00:45:52,820 --> 00:45:54,920
There are proteins
and things circulating

1116
00:45:54,920 --> 00:45:58,670
throughout your cells that
are there to repair DNA.

1117
00:45:58,670 --> 00:46:01,040
And if you stimulate the
production of those repair

1118
00:46:01,040 --> 00:46:04,070
mechanisms, then the repair
will be more rapid given

1119
00:46:04,070 --> 00:46:06,150
the same amount of stimulus.

1120
00:46:06,150 --> 00:46:07,727
So in this case there are--

1121
00:46:07,727 --> 00:46:09,560
let's see-- I'm just
going to say proteins--

1122
00:46:09,560 --> 00:46:11,120
I can't say anything more--

1123
00:46:11,120 --> 00:46:12,860
that will actually
travel along DNA,

1124
00:46:12,860 --> 00:46:15,950
looking for certain
types of kinks or breaks

1125
00:46:15,950 --> 00:46:17,240
and repair them.

1126
00:46:17,240 --> 00:46:19,670
If those repairs happen
before cell division,

1127
00:46:19,670 --> 00:46:21,500
then the mutation is avoided.

1128
00:46:21,500 --> 00:46:23,450
If you have more of
those repair mechanisms,

1129
00:46:23,450 --> 00:46:25,880
it takes a little bit
more energy to make them,

1130
00:46:25,880 --> 00:46:27,650
but you also have
less of a chance

1131
00:46:27,650 --> 00:46:32,160
of a mutation manifesting
itself past division number one.

1132
00:46:32,160 --> 00:46:34,530
So this is kind at the
cellular level idea

1133
00:46:34,530 --> 00:46:36,810
why might hormesis
be true, because you

1134
00:46:36,810 --> 00:46:40,110
stimulate your body's
ability to defend

1135
00:46:40,110 --> 00:46:43,237
against this kind of stuff.

1136
00:46:43,237 --> 00:46:44,070
And so there you go.

1137
00:46:44,070 --> 00:46:46,530
Cells can actually
signal each other.

1138
00:46:46,530 --> 00:46:51,510
So let's say a cell undergoes
DNA damage and can't divide.

1139
00:46:51,510 --> 00:46:52,980
These cells can
actually send what

1140
00:46:52,980 --> 00:46:55,920
they call kill signals
in the intercelluar space

1141
00:46:55,920 --> 00:46:58,320
to the nearby cells,
stimulating them

1142
00:46:58,320 --> 00:47:00,030
to mount some sort of response.

1143
00:47:00,030 --> 00:47:02,310
Either release
something or divide more

1144
00:47:02,310 --> 00:47:04,710
to make up for the dead
cells, which could be good

1145
00:47:04,710 --> 00:47:06,420
or which could be bad.

1146
00:47:06,420 --> 00:47:08,760
If you make more of these
DNA repair mechanisms,

1147
00:47:08,760 --> 00:47:10,590
that's probably a good thing.

1148
00:47:10,590 --> 00:47:12,300
If you stimulate
the nearby cells to

1149
00:47:12,300 --> 00:47:15,750
divide faster, well what are the
two things that could happen?

1150
00:47:19,350 --> 00:47:19,850
Yeah?

1151
00:47:19,850 --> 00:47:21,330
AUDIENCE: More mutations.

1152
00:47:21,330 --> 00:47:22,740
MICHAEL SHORT: Why do
you say more mutations?

1153
00:47:22,740 --> 00:47:24,198
AUDIENCE: Well, I
mean, If you have

1154
00:47:24,198 --> 00:47:26,820
cells that were in a radiation
environment, that are exposed

1155
00:47:26,820 --> 00:47:29,250
to that radiation
you're dividing faster,

1156
00:47:29,250 --> 00:47:31,740
each division has a
certain chance of mutation.

1157
00:47:31,740 --> 00:47:34,260
More divisions overall means
more mutations [INAUDIBLE]

1158
00:47:34,260 --> 00:47:35,520
MICHAEL SHORT: Exactly, yeah.

1159
00:47:35,520 --> 00:47:38,685
If there are cells nearby that
have been exposed or mutated

1160
00:47:38,685 --> 00:47:40,830
and you induce
faster division, you

1161
00:47:40,830 --> 00:47:44,550
may induce faster
incidence of the--

1162
00:47:44,550 --> 00:47:47,850
what is it-- of manifestation
of this mutation.

1163
00:47:47,850 --> 00:47:49,687
But also, if-- let's
say, a few cells die

1164
00:47:49,687 --> 00:47:51,270
and the other ones
divide to make up--

1165
00:47:51,270 --> 00:47:53,307
take up the slack, that
might be a good thing.

1166
00:47:53,307 --> 00:47:55,140
This is a normal way
that you repair injury,

1167
00:47:55,140 --> 00:47:58,830
is upon cell death, the
cells nearby divide faster,

1168
00:47:58,830 --> 00:48:01,240
fill in the gaps, and try
and repair the tissue.

1169
00:48:01,240 --> 00:48:03,750
So it's both a good thing
and can be a bad thing,

1170
00:48:03,750 --> 00:48:08,810
depending on what the nearby
cells have been exposed to.

1171
00:48:08,810 --> 00:48:11,500
And so there's also this-- they
call that the bystander effect,

1172
00:48:11,500 --> 00:48:14,980
where, interestingly, you
can have biological effects

1173
00:48:14,980 --> 00:48:18,430
in cells that receive no
radiation exposure if they're

1174
00:48:18,430 --> 00:48:21,740
near cells that have
received radiation exposure.

1175
00:48:21,740 --> 00:48:24,040
There are some awesome
experiments showing this.

1176
00:48:24,040 --> 00:48:27,040
We had one here, back when
we had a professor that

1177
00:48:27,040 --> 00:48:28,750
did medical physics.

1178
00:48:28,750 --> 00:48:31,300
She had created an
accelerator with a microbeam,

1179
00:48:31,300 --> 00:48:33,730
like a micron-wide
proton beam, when

1180
00:48:33,730 --> 00:48:36,520
you could irradiate single
cells and watch what

1181
00:48:36,520 --> 00:48:38,260
happens to the cells nearby.

1182
00:48:38,260 --> 00:48:41,150
So to study in a controlled
way, this bystander effect.

1183
00:48:41,150 --> 00:48:43,750
So if you irradiate one
cell on a glass slide,

1184
00:48:43,750 --> 00:48:45,535
how do the other ones respond?

1185
00:48:45,535 --> 00:48:47,230
So you know which
one was irradiated

1186
00:48:47,230 --> 00:48:49,360
and you can watch what
happens to the other ones--

1187
00:48:49,360 --> 00:48:50,650
pretty slick.

1188
00:48:50,650 --> 00:48:52,510
That accelerator,
actually, parts of that

1189
00:48:52,510 --> 00:48:55,025
live on the DANTE
proton accelerator

1190
00:48:55,025 --> 00:48:56,650
that we now use for
physics and things.

1191
00:48:56,650 --> 00:49:00,070
But a lot of the parts from
those machines are still here,

1192
00:49:00,070 --> 00:49:02,050
just the microbeams and
the cell parts aren't.

1193
00:49:04,730 --> 00:49:07,220
And then I highlighted
a few of these passages

1194
00:49:07,220 --> 00:49:10,550
in sort of the DNA
damage bystander effect.

1195
00:49:10,550 --> 00:49:13,700
One of the reasons is
when cells nearby divide,

1196
00:49:13,700 --> 00:49:15,530
they scale up their metabolism.

1197
00:49:15,530 --> 00:49:17,120
They have to burn
more energy in order

1198
00:49:17,120 --> 00:49:19,220
to undergo division faster.

1199
00:49:19,220 --> 00:49:22,760
And that can undergo what's
called oxidative metabolism.

1200
00:49:22,760 --> 00:49:27,200
Cells can produce energy
aerobically or anaerobically.

1201
00:49:27,200 --> 00:49:29,480
When you're dividing very
quickly, all of a sudden,

1202
00:49:29,480 --> 00:49:32,450
you start burning more
oxygen to divide faster,

1203
00:49:32,450 --> 00:49:34,280
to do whatever you have to do.

1204
00:49:34,280 --> 00:49:38,000
And that oxidative metabolism
also creates free radicals just

1205
00:49:38,000 --> 00:49:40,670
from normal wear and
tear to your cells.

1206
00:49:40,670 --> 00:49:43,550
And those oxidative
byproducts may also

1207
00:49:43,550 --> 00:49:46,850
induce mutations in
the same primary way

1208
00:49:46,850 --> 00:49:48,410
that radiation does.

1209
00:49:48,410 --> 00:49:51,770
Radiation does hydrolysis,
makes oxidative species

1210
00:49:51,770 --> 00:49:53,240
that damage DNA.

1211
00:49:53,240 --> 00:49:56,450
Chemical oxidative metabolism
can produce the same sorts

1212
00:49:56,450 --> 00:49:59,570
of things that can damage
DNA in the same way, just

1213
00:49:59,570 --> 00:50:02,220
a different initial effect.

1214
00:50:02,220 --> 00:50:04,170
I'm going to stop here,
even though we only

1215
00:50:04,170 --> 00:50:07,760
have a few slides to go,
because it's exactly five of.