The following table is meant to orient the reader to comparative radiation levels. It is expressed in multiples of the lowest level in my studio, which happened to be my darkroom coating counter.
Nearly adjacent spots can read wildly differently. For example, in this table a certain drainpipe appears twice. When I frisked it at 1 foot above ground level, it was 200 times more radioactive than my coating counter. As I bent down and continued measuring, the level quickly rose. At ground level it had more than doubled, to 533 times the benchmark value. The moral: If you enter a hot zone, please do not stay very long unless you know which side of the street to stand on.*
Please note that nearly all the Japanese readings in this table were made in 2014. In 2011 many of them would have been much higher. For instance, on March 16, 2011, one spot in the town of Iitate reportedly read more than 95 microsieverts an hour. When I measured this same place on October 23, 2014, the level was less than 5 micros.
Do not conclude from this that the nightmare of Fukushima was approaching its end. Cesium-137, a major pollutant, has a half-life of 30.2 years. As you will see, 10 half-lives, or 302 years, must pass to reduce the concentration of this isotope to 1/1,000 of its peak level.—Why then did the measured radiation decline so rapidly?—Because the cesium had been washed a few centimeters underground, or into rivers, or took up residence in mushrooms and trees.
In the abandoned town of Tomioka I got the chance to measure the drainpipe of a certain house which had been under decontamination eight months before. On that first occasion it had measured 22.1 micros per hour (evidently the crew had not yet gotten to it). On my return, with the yellow tape around it removed and the crew long gone, it measured 32 micros. How would you like to live in that house?
COMPARATIVE MEASURED RADIATION LEVELS, 2014–15* (with Hiroshima readings from 2017),
in multiples of lowest Sacramento interior reading
(from pancake frisker* data)
All levels expressed in [microsieverts per hour]. Benchmarks interpolated in boldface.
“<R>” means “reported”; in other words, this value was not measured by me.
“Average frisk” is the arithmetical average of several instantaneous readings in NORMAL mode. “Short frisk” is a steady NORMAL reading measured over 1 to 10 seconds. Dental X-rays have been read in MAX mode. All others measured in 1-minute timed counts.
The full data from which these readings were selected appears in the end matter.
1 sievert (Sv) = 1,000 millisieverts or “millis” (mSv) = 1,000,000 microsieverts or “micros” (microSv). 1 rem = 10 mSv. For definitions, see here. All figures over 1 million rounded to 2 significant digits.
<1–7.61
<R> 0.04 to 4 mSv per year. Worldwide variations in natural background dose. [0.00457 to 0.457 microSv/hr].*
1
My studio darkroom coating counter, Sacramento. The lowest measurement of which the frisker was capable [0.001 micros per second].* A full year later, having frisked many other places, I had duplicated this lovely reading in only a few places, so I shall list them all here: Dunsmuir, California (in a forest overlooking the Sacramento River), some surprisingly urban sites in Portland, Oregon; Subway L3 in Barcelona (well underground); a breeze in the middle of the Neva River in Saint Petersburg [Russia], and the marble floor of the cafeteria in the Tretyakov Gallery in Moscow [0.06 microSv/hr]. This equals 0.5256 millis/yr. On a per-minute basis, the cumulative per capita fallout dose in the Northern Hemisphere from 1945 through 1999 was 1/27 of this amount.
1.9
<R> 1 mSv per year. Maximum dose advised for ordinary citizens, per the International Commission on Radiological Protection.* Obviously this conservative standard generally goes unmet. See entry for multiple 4.6. It approximates the total body irradiation one receives from natural sources at sea level “in most parts of the world.” For every increase in altitude of 1,500 meters, an additional 0.28 millis a year [0.03 micros a minute] may accrue. For professional workers, the ICRP maximum was 20 mSv. [0.11416].
2
The Darjeeling tea palace, Ginza, Tokyo. Coal House (built almost entirely of coal), Williamson, West Virginia, U.S.A. My studio’s kitchen counter in Sacramento. Kievsky metro station, Moscow (deep underground). Shore of Lake Geneva, at Cully, Switzerland (near Lausanne). Air dose in La Rambla, Barcelona. Also typical of downtown Poza Rica, Veracruz, Mexico. [0.12].
3
Air dose in National Orchid Garden, Singapore. Concrete office interior, sex workers’ organization, Dhaka, Bangladesh. Ironwork railing of Gogol’s grave, Moscow. Sewer grating in Passeig de Sant Joan, Barcelona. Lump of coal on ground, mountaintop removal mine, Cook Mountain, West Virginia. Air dose near Barapukuria Coal Mine Company conveyor, Bangladesh. Stone step of El Tajín archaeological site (Totonac pyramids), near Poza Rica. Front of railroad station, Fukushima City, Japan (same reading for 3 consecutive days). Air dose [at waist level] on bridge between Atomic Dome [= Ground Zero, 1945] and Peace Park, Hiroshima. [0.18].
3.67
<R> Decontamination target for households in Iwaki, Japan* [0.22].
3.8
<R> 2 mSv per year. Japanese national target air dose (“1 additional milli”). Based on the same assumptions as in the footnote to 3.67. [0.22832].
4
Mary Cook’s headstone, Cook Mountain, West Virginia. Carrea Sant Anna, Barcelona, after a rain. Air dose by Atomic Dome, Hiroshima. Fallen leaf on gravel walkway, Tsurugajo Castle, Aizu-Wakamatsu, Japan. Interior of taxi van, Hirono, Japan. Interior wall of Enrique’s Restaurant, Poza Rica. The last 3 readings were the highest in their respective locales. [0.24].
4.6
<R> 2.4 mSv per year. Average worldwide annual dose, according to Mr. Kida Shoichi, Nuclear Hazard Countermeasure Division, Iwaki. [0.27397].
5
Deserted playground, Naraha, Japan [0.296]. Granite wall of Jardin de Veant, Lausanne. Bricks in Bangladeshi brickyard, 60 km north of Dhaka. Interior of Taylor’s Books, Charleston, West Virginia [0.3]. On a different day, Taylor’s Books measured only 0.18.*
5
Granite countertops in hotel suites in Charleston, West Virginia, and in Portland, Oregon [0.3].
5.7
<R> “An average radiation background dose for a human being,” according to James A. Mahaffey, Ph.D. (3 mSv per year). An identical value: “The average resident of the United States is routinely exposed to about 300 millirem . . . every year from the soil beneath their [sic] feet and the sun shining overhead.” [0.34248].
6
Air dose on stone curb by Atomic Dome, Hiroshima. Ocean vantage point, Naraha [0.36]. The highest reading found in both locales.
6.83
<R> Average American yearly dose, mid-1990s [0.41].
6.85
<R> 3.6 milliSv per year. Alleged average worldwide dose. [0.41095].
7
Koriyama Station [Japan], outdoor plaza [0.42].
7.61
<R> 4 milliSv per year. Old recommendation of International Committee on Radiological Protection, re: ceiling dose. [0.4566].
8
Ten Commandments courthouse tablet, Pineville, West Virginia [0.48].
9
Granite curb of Molotov’s grave, Moscow. Sidewalk by air dose marker, Fukushima City. Ocean beach in Okuma red zone, 3.5 km from Reactor No. 1. This last was the lowest reading found in that red zone. [0.54].
9.51
<R> 5 milliSv per year. “For an individual steadily receiving 500 millirads [= 5 milliSv] per year, the chance of dying from cancer or leukemia is increased by 30 percent.” That claim (from 1971) is much disputed; see header 190. “A read of 5 millisieverts is one of the thresholds for whether [Japanese] nuclear plant workers suffering from leukemia can be eligible for compensation . . .” [0.570776].
10
Granite pedestrian zone of Anichkov Bridge, Saint Petersburg, Russia [0.60].
13
Air dose upon entering greater Iitate, Japan [0.78].
16.67
<R> 0.1 millirem/hour. Per First Responder’s Guide to Radiation Incidents (2006), the ceiling for safe background dose. [1.0].
19
Decontaminated driveway, Iitate red zone [1.14].
23
Cherry trees not exposed to ocean wind, Iitate red zone [1.38].
29
<R> More than 15 milliSv per year. “Living on the atoll and consuming local food,” Bikini, 1997—a half-century after U.S. nuclear bomb tests. [1.712].
29
Roadside 10 m from bags of contamination waste, Iitate red zone [1.74].
34
A moment at cruising altitude (elevation unstated), Tokyo to Singapore [2.04].*
38
<R> 20 milliSv per year. Upper limit of Japanese green zone (this color meant “decontaminate with priority,” and here the government hoped soon to lift any ban). Lower limit of Japanese yellow [“residence restriction,” or daytime use only] zone designation. [In 2014, central downtown Tomioka was one such zone.] Legal ceiling for a nuclear worker in non-emergency conditions. The ICRP maximum for professional workers, including radiologists, dental technicians, etc. [2.283].
39
Edge of red zone, downtown Tomioka, Japan [2.34].
41
A sampled moment at airplane cruising altitude (36,000 ft), Washington, D.C., to San Francisco [2.46].
42
A sampled moment at cruising altitude (37,013 ft), San Francisco to Los Angeles [2.52].
49
First torus of White Bird Shrine, Iitate red zone [2.94].
54
Average frisk, roadside hydrangea flowers, Iitate red zone [3.25].
55
Airplane reading, maximum in five-minute interval, 35,988 feet over North Pole [3.32].
61
Two steps past no-go zone warning sign [i.e., for red zone] on Hometown Appreciation Road, Tomioka [3.66].
68
Ten steps farther into red zone in same place as previous. Identical reading standing in center of cherry tree boulevard, Yonomori, Tomioka yellow zone. [4.08].
71
Average frisk, deserted crossroads beside radiation dose digital sign, Iitate red zone [4.25].
83
Short frisk, vegetation in abandoned downtown, Okuma red zone [5].
83
<R> “A passenger in a plane flying at 12,000 meters [39,360 feet] receives 5 microSv/hr from cosmic rays . . .” [5]. This figure seems high to me; see 41 and 55.
87
“WELCOME TO OKHUMA,”* downtown by JR station, Okuma red zone [5.19].
95
<R> 50 milliSv per year. Upper limit of yellow zone designation; lower limit of red [no-go] zone. [5.708].
99
Goldenrod by wrecked houses, Okuma red zone [5.94].
100
Cherry trees exposed to ocean wind, Iitate red zone, average frisk [6]. Interior of closed vehicle at this spot measured 3.5.
115
Downtown street between former town hall and the tsunami-damaged Ono train station, Okuma red zone [6.9].
123
Fence of abandoned old age home in Okuma red zone, with clear line of sight to Reactor No. 1 (at about 2.5 km away) [7.38].
133
Average frisk, interior of Ono station, Okuma red zone [8].
142
Destroyed shrine, Okuma red zone [8.52]. The road two steps past this spot measured 20 and higher (which encouraged me to make a short frisk).
181
Air dose in front of fish hatchery, Okuma red zone [10.86].
183
Air on side street in Tomioka green zone, just off Highway 6 (which was probably contaminated by the trucks of decontamination workers), frisked at waist level [11].
190
<R> 100 milliSv per year. 0.5 percent increase in probability of fatal cancer, if this dose is received for the entire year.* [11.416]. This was the average dose received by the “liquidators” who entombed the reactor at Chernobyl.
200
Drainpipe in Tomioka green zone, frisked at 1 ft from ground level [12].
>217
<R> Hot spots in Aiikuen Orphanage, Fukushima City, March 2013 [>13].
228
<R> 120 millis per year. Alleged annual dose in an unnamed Brazilian village. [This would be awfuly high.* The Brazilian town of Guarapari* is said to receive 10 millis per year]. [13.699].
333
Drainage grating by fish hatchery in Okuma red zone, short-frisked at waist level [20]. At 3 inches, this same grating measured 30. I chose to reach no closer.
350
The same side street in Tomioka green zone that measured 11 micros at waist level, now frisked 3 inches from pavement [21].
365
Another drainage grating in Okuma red zone [21.9].
492
Pavement in Okuma red zone [29.5].
533
Same Tomioka green zone drainpipe that measured 12 micros when frisked at 1 ft [see multiple 200], now frisked at ground level [32].
692
Grass near hatchery in Okuma red zone [41.5].
This last is the highest reading I personally measured in the field. Of course it is disturbing. The municipal officials accompanying me were unimpressed. They said that in 2011 this area read 100 micros and more. Exactly how dangerous was that grassy spot when I frisked it? If sustained over a year, its radiation level would produce a dose of 363.54 millis. Needless to say, nobody was planning to camp there for a year. And so I must reiterate that so long as the level is, in and of itself, subacute, the peril at that level depends on the duration of the exposure. Even in Okuma I probably increased my lethal cancer risk only negligibly, assuming that I managed not to inhale too many alpha or beta particles. I remained in Okuma for all of four hours, and much of that in a closed vehicle. Had I idled away 40 hours by that grassy place of the 41.5 micros, I would still have been considered safe enough by 1958 standards [see 1,250].
761–1,712
<R> Exposure in outer space (400 to 900 mSv per year) [45.662–102.7397].
880
<R> Mission to Mars (1.14 Sv over 30 months) [52.778].
1,000 if single dose, or 3.6 million sustained over 1 hr
<R> [0.6 millis] Japanese chest X-ray, ca. 2007 [60 micros, received in about 1 sec. Hence this same dose sustained over an hour would be about 216,000 micros or 216 mSv.].
1,250
<R> [0.3 rem per week or 7.5 mrem per hour for a 40-hr workweek.] Maximum permissible external dose for an American nuclear worker in 1958. [75].
> 1,667
<R> Stated level in Okuma immediately after the nuclear accident [> 100].
Reader, how brave do you feel when you go to get your teeth checked? Back home in Sacramento my kindly dentist agreed to receive the pancake frisker as a special patient. I laid it down in the chair, and the beautiful Amanda trained her X-ray camera on its head. The results were thought-provoking:
2,520 if single dose
Dental X-ray camera, fired through protective lead apron, intensity at 0.20, which was the setting Amanda used for most teeth [151.2]. My first thought was that pregnant women had better ask for two lead aprons. But Dr. Richard Crownover reassured me: “The shielding for dental X-rays is not placed in the direct beam. It is designed to be adequate shielding for peripheral leakage and scatter outside of the imaging field. If your numbers refer to an apron in the direct beam then you will be criticized for alarmist advice to pregnant women.”
4,117 if single dose
Dental X-ray camera, without lead apron, intensity at 0.20 [247].
4,183 if single dose
Dental X-ray camera, without lead apron, intensity at 0.23, which is used for molars [251].
Because I laid a dosimeter next to the frisker for each of those three readings, the results were even more enlightening. The lead apron blocked out 1 of the 2 micros. Without the apron, a full 2 micros fell upon my instruments. Increasing the setting from 0.20 to 0.23 did not much raise the radiation level, but it must have increased either the duration or the width of the beam, because instead of another 2 micros, the dosimeter registered 37. 9—about the same as if one had stood at that grassy place in Okuma for a whole hour.*
9,921
<R> 100 milliSv per week. Emergency exposure limit for nuclear workers in Japan, 2014 (susceptible to upward revision, which the government was considering). [595.238].
16,250 if single dose
Security X-ray for carry-on baggage, Yaeger Airport, Charleston, West Virginia. (Frisker sent through screening machine.) [975 over about 1 min]
16,667 if single dose
<R> Full-body CT [computerized tomography] scan: 10 millis. [Assuming the duration of the scan is an hour, this would be 1,000 micros an hour.]
17,100
Security X-ray, Los Angeles International Airport [1,026]. One hopes for the workers’ sake that this device is shielded.*
833,333
<R> 50 milliSv per hour.* [5 rems]. Maximum dose for an American “first responder” not saving lives or valuable property. Estimated level in collapsed plutonium storage tunnel during 2017 nuclear accident in Hanford, Washington.* [50,000 micros/hr].
2.5 million
<R> 25 mSv received in 10 minutes by the crewmen who sought to release steam from Reactor No. 1 before it exploded. Over an hour this would have added up to 150 millis. [150,000].
8.33 million
<R> 500 milliSv, over any time period [50 rems]. [500,000 micros/interval]. “A total dose of 50 rem of gamma radiation, largely independent of the rate of administration, causes approximately the same number of mutations as occur spontaneously over a lifetime.”* This author (writing in 1958) believed that such a dose received in a few hours and over the entire body would probably cause radiation sickness. This may be too pessimistic.
11.67 million
<R> 0.7 Sv per hour* [70 rems]. Possible onset of radiation sickness. [700,000]. 16,868 times higher than my highest measurement in Okuma.
11.67 million
<R> 1 Sv per hour* [100 rems]. Definite onset of radiation sickness. [1 million].
21.67 million
<R> 1.3 Sv per hour, most of which was received almost at once by a female victim of the Hiroshima A-bomb. She was bedridden with “acute radiation syndrome” for 3 months. [1.3 million].
33.33–50 million
<R> 2–3 Sv per hour.* “Permanent female sterility is possible.” [2–3 million].
50–66.67 million
<R> 3–4 Sv per hour.* “Uncontrollable bleeding in the mouth, under the skin and in the kidneys after the latent period”; 50% will die within 30 days. [3–4 million].
75 million
<R> 4.5 Sv, instantly. “At Hiroshima a dose equal to or greater than 450 rads (4.5 grays) extended to almost 1 mi. . . .” [4.5 million, instantly].
100 million
<R> 6 Sv per hour. Probably lethal within 1–3 weeks. [6 million].
279.89 million
<R> 16.793 Sv per hour.* Dose taken by the helicopter pilot Colonel Vodolazhsky [and probably sustained for only a few minutes] in one of his flights over the Chernobyl reactor, 1986. [He died, but not right away, and possibly not just from this.] [16,793,394.598]
166.67–833.33 million
<R> 10–50 Sv per hour.* “100 percent fatal after seven days”—but see slightly different claim for 50 Sv/hr, below. “Conditions for this exposure have depended on touching proximity to a supercritical sphere of naked plutonium.” [10–50 million].
171.67 million
<R> 10.3 Sv per hour. Measured value in Reactor No. 1’s suppression chamber, June 2012 (“likely to be fatal if a person stays there for an hour”). [10,300,000].
833.33 million
<R> 50 Sv per hour* [5,000 rems]. All exposed persons die within 48 hours. [50 million].