Radioactive fallout in the Manila Area and its public health significance

Media

Part of Acta Medica Philippina

Title: Radioactive fallout in the Manila Area and its public health significance
Creator: Lesaca, Reynaldo M.; Reyes, Wilfredo L.
Language: English
Source: Volume XV (2) October-December 1958
Year: 1958
Subject: Radioactive fallout; Radioactive pollution of the atmosphere; Medicine -- Periodicals
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Fulltext: RADIOACTIVE FALLOUT IN THE MANILA AREA AND ITS PUBLIC HEALTH SIGNIFICANCE* REYNAJ,DO P.I. LESACA., Dr. Eng'g . ..• WIU'REDO I,, REYES, M.P.H. Department of P1tl1lic Health Engineeri11y Institute of Hy{/iene, Univei·sity of the Phili1minn; When a nuclear weapon is detonate<l, fission or fusion 1n·oducts are formed together with the various comJ)onents of the weapons assembly which are \'Olatilized by the intense heat generated. This mass of luminescent gas, popularly known as the fireball, sucks up varring amounts of dust from the gl'ound and forms eventually the familiar mushroom-shaped cloud so characteristic of these explosions. Th<' radioactin~ particulate matter that are formed are t-arried to great heights and are often carried br the atmospheric jet stream all O\'Cl' th<' '''01·Jd. These particles then begin their slow rlescent to ca1th, subject to existing meteorological conrlitions. Radioactive dust thus accumulated on the earth's surface following nuclear explosions are known as fallout. The increase in rarliation background obser\·ed following these rletonations are due primarily to the rleposition of these very fine materials, especially the relatively Jong-lived ones (1, 2, 3). Up to the present time the exact mechanism by \vhich these particles settle to the earth's surface is not too well understood. However, it is now \1·ell accepted that megaton yield weapons ( H-bombs) carrr rarlioactive material to the stratosphere (abon~ 50,000 ft.) and are almost entirely responsible for the world-wide fallout, while kiloton yield weapons carrr radioactive debris to the troposphere (below 40,000 ft.) and is responsible for localizerl fallout ('I). Historically, fallout began in 19,lfi when the firl'il atomic bombs were explorlerl in New l\'lexieo a1ul .Japa·n. Subsequent • Read at the regular monthly mcl'ting o( !hi' Philippinl' Public Health AS&Oeiation, Dttember 15. 1958. 87 88 ACTA MEDICA PHILIPPINA tests Of conventional bombs also produced fallout, buUn all thl!se cases it was small in amount and more or less localized in extent. Numerous studies have been and are being undertaken in other countries on the extent of this problem, and al1 indications point to the fact that nuclear detonations definitely cause an increase of radioactive debris in the upper layers of the atmosphere, the debris floating down very slowly to the earth's surface. This fact principally has led to the general agitation of peoples all over the world to ban further nuclear testing. In this country no such studies have yet been undertaken save perhaps a few samples examined every now and then as reported by the world-wide gummed film network of the U.S. Atomic Energy Commission (3). The purpose of this study then, is to obtain some data on the fallout in the Manila area as measured at the Institute of Hygiene building, resulting from the various nuclear explosions that have recently occurred. These detonations started on April 28, 1958 and lasted till about the first week of November when no more explosions were reported in the papers. It is hoped that this paper may stimulate others in undertaking or initiating further studies along this line. Fallout measurements are generally given in disintegration l'ate (curie) units because of technical difficulties and expense that would be involved in making continuous low-level rediation dose measurements. Actually it would have been better to give the results in dose rate units - rads, roentgen, rems - since these are the expressions that are of genetic and biological importance. Approximate indirect methods have been devised to express fallout measurements in terms of dosage, but the literature and equipment available at the present does not permit us to do this. SAMPLING AND MEASUREMENT Three methods of sampling were used. The first method consists of drawing air through an ordinary filter paper and the accumulated dust coming from the atmosphere is measured for radioactivity. Results are then expressed as disintegration per minute and converted to millicuries per cubic meter of air sampled. An ordinary baby milk glass bottle with plastic screw RADIOACTIVE FALLGUT .. 89 cap and inverted rubber nipple was connected to a suctioii pump through a gas meter as shown in Figµ.re A. The al·ea of the exposed filter paper was approximately 0.8 square inch. The second method makes use of filter paper of known area exposed to the air for 24 hours and the measured activity is then expressed in disintegration per minute transformed . into millicuries per square mile per 24 hours. This method has been lately improved by using the 1 foot square of gummed filin (similar to Scotch tape) provided by the Philippine Atomic Energy Commission. Whenever this supply is exhausted, use is made of a 10 inch x 10 inch ordinary filter paper coated with vaseline (petrolatum) in order for the settled particulate matter to adhere to the paper. The latter method is used by the Japanese (5). In both methods, the collecting media (filter papel' or gummed film loc~ted in the roof of the Institute of Hygiene building about 70 feet above ground level) are then ashed in an evaporating dish at 550°C. (about l000°F.), washed with distilled water to a I-inch stainless steel planchet, dried to constant weight and counted for activity by a Tracerlab GeigerMuller (GM) Tube of about 1.8 mg. per sq. cm. window thickness. A matched decimal Scaler records the activity of the sample which is placed about 8.7 mm. from the thin end window of the GM tube whose rliameter is 27 mm. Another method tried utilized the electrostatic precipitator to gather the airborne dust particles. These are collected by rlrawing air into a chamber where a potential of 12 kilovolts is applied. Once collected, the dust particles are washed into a containet· with distilled water and filtered through the membrane microfilter. The filter is then ashed and counted for activity as in the other two methods, the results being expressed in disintegrations per minute per unit volume of air. Use of this method in this study was limited to days when there were noticeably high counts in the other two methods and served mainly as a check. The above methods referred to collection of airborne particles directly. Mention should also be marle of the attempt to determine the radioactivity brought down by precipit.ation. Here, a measured amount of rainfall, 3li collected in a beaker, 90 ACTA llEDJCA PHILIPPINA Filter filtor cap (a) Filter Paper-Suction Pump @Board I film (bl Gummed Film Method (c) Electrostatic Precipitator FIG.A- DIAGRAM OF SAMPLING SET-UP RADIOACTIVE FALWUT 91 is slowly evapol'ated directly into a planchet and counted. Results are then expressed in disintegrations per minute and conve1ted to micromicrocuries per liter of water sample. RESULTS AND INTERPRETATION The results of the various measurements made are given in the tables and figures. Table 1 shows the air dust radioactivity in net counts per minute per cubic meter of air sampled. This activity is then divided by the efficiency of the counter (0.186 as determined by using 2 reference standards: simulated 1m with an activity of 2.30 x 10·5 microcuries and m2io with Table 1. RADlOACTIVITY, INSTITUTE OF HYGIENE, MANILA, PHILIPPINES, JUNE-NOVEMBER, 1958 in Net CPM/cu. m. AIR, FILTER PAPER-SUCTION PUMP SAMPLE Air Dust Air Dust Air Dust DATE Activity, Net. DATE Activity, Net DATE Activity, Net cpm/cu. m. c1>1n/cu. m. cpm/cu. m. -- - -- -- - -- --- - Tune ' :1.0 July 10 2.2 Sept. 1 0.1 ' 3.7 11 1.3 3 o.o 6 1.9 12 3.1 4 0.5 8 3.4 17 0.3 • 0.8 • 2.7 22 0.7 10 ... 10 2.2 23 4.8 16 0.0 12 0.0 24 3.3 17 0.4 13 O.!i 28 0.8 Oct. 8 0.2 14 0.9 30 3.1 9 0.8 16 0.2 :n 1.1 10 1.8 17 0.1 Aug. 1 1.7 14 0.2 20 t.a • 2.3 1:; 0.1 23 0.4 7 2.2 16 0.7 24 0.7 8 0.8 Nov. 3 :\,0 26 1.9 II 2.0 ' 0.1 26 7.2 12 1.2 9 0.0 27 8.4 13 1.5 10 0.3 28 a.• 14 2.!i 17 0.9 30 9.2 15 2.4 19 0.0 July l 15.7 18 0.9 20 l.l 2 3,:1 20 0.6 21 2.1 ' 16.6 21 1.1 22 :1.2 5 5.3 22 0.7 25 1.5 7 7.0 26 0.2 29 :u 8 4.6 27 1.0 • 28 0.9 ,.,. • c ~ 10~ .. ! E : ! 0 II 10' ; 5 i l• IS ,,, $1 rs 0 ,,, I •• .IUME .IULT AUGUST SIEPTEMBU OCTOIElt NOYEllHll FIG.I-RADIOACTIVITY. INSTITUTE OF HYGIENE. MANILA. PHILIPPINES • .IUNE-HOV •• 1111 IN MICRO·MICROCURIES PER 10 CU.M. AIR (FILTER PAPER-SUCTION PUMP IAll~Lltl ~ "' .. ::i > RADIOACTIVE FALLOUT 93 an activity of 1.50 x 10·6 microcuries, both beta emitters) and coitverted into micromicrocuries per 10 cu. meters and plotterl in Figure 1. Table 2 shows the net counts per minute of settle<l dust per sq. foot of exposed area per day. This is converted into millicuries per square mile per day and plotted in Figure 2. Table 3 presents the rainwater activity. A few decay curves of unusually high activities obtained are plotted in Figure 3. The results obtained in these studies on gross activities of sampled fallout may be summarized as follows : 1. Using our instrument, the background count in the Manila area apparently increased from about 22 counts per minute (September 1957 to June 1958) to about 27 counts per minute (July 1958 to present), an increase of almost 23%. 2. The natural (or normal) radioactivity in the Manila atmosphere is estimated to be about 2 x 10·12 curies per cubic meter. This compares with the 5 x 10·11 curies per cubic meter observed in New York (I) and about 10·11 curies per cubic meter in Tokyo, Japan (5). '3. The apparent natural activity of settled dust in Manila is about 3.5 x 10·11 curies per square foot or roughly 1 me/sq. mile. This is approximately half of the U.S. figures, and about the same as Japanese findings. 4. Radioacti\'e fallout may be cletected in Manila from about 3 days to as long as two weeks after a nuclear detonation, <lepending largely upon local atmospheric con<litions and energy yield of the weapon tested as suggested by the Report of the U.N. Scientific Committee on Atomic Ra<liation (6). A nuclear explosion somewhere in the world however, cannot always be detected in Manila from fallout measurements alone. Nevertheless, an unusually high activity locally recorded means a detonation especially of high rield weapons such as hycil'ogen bombs. Showers and rainfalls also usually bring about an apparent increase of atmospheric radioactivity. 5. Several peaks were observed during the announced test explosions and these peaks represented high activities from about twice to 60 times the natural activity. The maximum activity was estimated on July 3-6 when settled dust registered an acth'ity of about 40 me per square mile (using only a plan94 ACTA MEDICA PBILIPPINA chet as sample holder). Two other peaks were observed using the one-foot square gummed film: one on September 16 with Table 2. RADIOACTIVITY, INSTITUTE OF HYGIENE, MANILA PHILIPPINES, AUGUST·DECEMBER, 1968 in Net CPM/sq. ft., GUMMED FILM SAMPLE - - - Air Dust Air Dust I Air Dust DATE Activity, Net DATE Activity, Net DATE Activity, Net cpm/sq. ft. cpm/sq. ft. cpm/eq. ft. Aug.is . -- 25 ·-- Sept. 23 -----44-- Nov. a· - - 1 - 17 8 24 53 4 3 18 • 26 6 ' • 19 26 26 3 ' 33 20 18 27 7 7 • 21 28 28 17 8 3 22 32 29 17 9 2 " 5 30 • 10 2 24 5 O<l 1 3 11 1 " 15 2 86 12 3 26 34 3 • 13 • 27 29 4 1 14 7 28 21 ' 6 16 • 29 21 • 7 16 • 30 17 7 5 17 ' 31 6 • 2 18 • Sept. 1 6 • • 19 12 2 29 10 0 20 6 3 11 11 10 21 11 4 9 12 1 22 1 5 2 13 1 " 1 6 16 16 4 24 • 7 15 17 15 25 13 • 15 18 16 26 16 9 23 19 21 27 16 10 13 20 21 28 26 11 11 22 6 29 7 12 9 23 • 30 7 13 29 24 1 Dec. 1 7 14 12 25 3 2 6 16 13 26 7 3 5 16 388 27 7 • 21 17 30 28 1 5 31 181 20 29 13 • 10 19 25 30 220 7 10 20 • 31 23 • • 21 5 Nov, 1 1 • 6 22 5 2 1 10 10 11 UK• t IOI 1.0 0.11 II'"' " ua~ • 111 t I U II •1.181111 IOlll THTI FIG.2-RADIOACTIVITY, INSTITUTE OF HYGIENE, MANIL~ ~ AUG-DEC,1958,MILLICURIES PER SQ.MILE(GUMMEu FILM) 96 ACT A MED.ICA PHILIPPl~.A • .... "ULY . ... FIG.3-DECAY CURVES HIGH-COUNT SAMPLES RADIOACTIVE FALWUT 9V an activity of about 26 miJlicuries per square mile and a second on October 30 which showed about 15 mi11icuries per square mile. Table 3. RAIN WATER RADIOACTIVITY, INSTITUTE OF HYGIENE, HERRAN, MANILA, JULY-OCTOBER, 1958 DATE July 11 12 13 " 15 16 18 Aug. 3 22 25 Sept. 15 16 "' 23 Oct. 7 14 26 Rain Water Activity Net cpm/100 ml. 34 38 25 21 11 16 s 6. Japanese scientists have suggested that air which ha<l been over the Bikini Atoll at noon on May 8, 1954 (3 days after a bomb explosion) passed by the Philippines sometime between May 12 and 13 and caused an increase of activity in Tokyo and other cities (7). This is probably what occuned again in June 29, 1958 when a high yield weapon was exploded anrl which resulted in an unusually high atmospheric radioactivity on July 3-6, assuming similar atmospheric conditions existed. An announced H-bomb test by the United Kingdom in Christmas Islands in the Pacific on Auliust 2, 1958 did not result in any unusual activity on September 16. Russian explosions on October 21 and 22 and on November 1 and 2 also resulted in a high activity 4 to 8 days later. 7. The natural radioaetivity of tap water in Manila averues about 2 cpm per liter or 5 micromicrocuries per liter. Raifl 98 ACTA MBDICA PRILIPPINA water activity on July 11-18 showed from 112 to 382 cpm or 275 to 930 micromicrocuries per liter, the maximum occuring during the rain of July 13, 1958. Due to laboratory difficulties, however, there were only a few rain samples studied. Lack of equipment has prevented us from determining the concentration of strontium-90 and cesium-137, long-lived radioactive nuclides that are of principal biological importance. Libby (4) has reported that from March 1955 to November 1957 the cumulative Sr90 fallout as recorded in Pittsburgh, Pa. was about 23 millicuries per square mile which is even greater than the gross activity peak recorded in Manila on October 30, 1958. Undoubtedly it is even higher today since there have occurred at least 20 nuclear explosions since then. In the one period, from November 1956 to October 1957, Libby estimates that the Sr90 cumulative fallout varies from less than a millicurie per square mile in Penya, Africa as reported by the U.S. Atomic Energy Commission to almost 12 millicuries per square mile as observed in Salt Lake City, Utah. In Nagasaki, Japan, the figure is about 7 me per square mile. Eisenbud and Harley (3) has reported that as of June 1957 the cumulative Sr90 in Manila is about 17 me per square mile and about 23 me per square mile in Tokyo, Japan, with a maximum of about 54 me per square mile in the Nevada area and 78 me square mile in Bikini area. PUBLIC HEALTH SIGNIFICANCE As public health workers we are interested in the possible harmful effects of these ionizing radiations to om· country and people. Just what is the magnitude of the problem posed by th.ese local findings and as reported in foreign scientific journals anrl how would we react to such problems? Before proceeding to answer these questions let us first state some facts concerning radiation in general (6): Fact I: Even the smallest amounts of radiation are liable to cause deleterious genetic effects - that is, limited to descendants - and perhaps also somatic effects, those limited to the irradiated organism itself. A Study Group convened by WHO categorically states that all man-made radiation must be regarded as harmful to man from the genetic point of view. RADIOACTIVE FALWUT 99 Fact 2: There are three principal sources of these radiations to which mankind in general is exposed : Natural sources - cosmic rays, atmospheric and terrestial radiation and the naturally occurring radionuclides. Man-made sources - medical uses of X-rays and radiotracers, industrial uses of X-rays and others such as luminous dials, TV sets, etc. Environmental contamination - due to nuclear explosions, radioactive waste disposal and accidents. Fact 3: Of these three sources, the first is outside of human control while the second and third are controllable. The second source is of great importance in science and industry and exposures can be reduced by perfecting protection and safety techniques. The third source constitutes a growing increment to world-wide radiation hazards and are beyond control of the exposed persons. With these in mind let us now try to get a quantitative comparison of the exposure dosages resulting from these sources. The following table, based on world-wide averages, summarizes these estimated dosages that may be applied to Philippine conditions (6): So 11 r c: e 11 Genetically Signifi- Per Capita 1'fean c:anl Dose - 30 year 1'farrow Dose - 70 niaximum in rems y'ar maximum in rema -------- ______ , _____ _ Natunil Man-made SOUJ'('es except environmcnt.-il contamination and oc<"upational expo1mre Occu1mtional expoi;ure Environmental contamination Teat.R end 1958 Tl.'sts continue 0.5-5 f,<>i>." tha11 0.116 .01 .Ol>-.12 Rangei; heyond 7 0.J-.2 .~.; 7.0-17 It is evident from the above data that even without the advent of tlw nuclear age we would be receh·ing f!Omc 3 rems of radiation during our repr·oductive period anrl about 7 rems t}froughout our life span. This flose we easily assimilate, since ·roo ACTA MEDJCA PfflLIPPINA it has always been with us and our bodies have been used to these normal radiations. In the United States, an upper limit of lOr for a 30-year genetic dose has been set with a balance between possible harm and possible benefit. It may be mentioned in passing that an acute dose of up to 25 rems over the whole body produces no obvious injury while dosages of more than 600 rems are fatal (9). The usual maximum permissible tissue dose has been set at 300 m re1Il8 per week ( 10) by the International Commission on Radiological Protection. The exposure due to natural sources has therefore practically an insignificant effect, the body capable of repairing any injury that may have resulted. The Advisory Committe on Biology and Medicine of the National Academy of Science sums up the problems of radioactive fallout thus: "Radioactive fallout in the surface of the earth can deliver 1·adioactivity to animals and man in two ways: ( 1) by the external route in which case the penetrating gamma radiation is of chief importance, and (2) by the internal route when the material is taken into the body with food, water, air, in which case the radiation of low penetrating powers can also reach the internal organs and is of chief concern. Therefore the problem is to estimate what harm may possibly result to man from the general increase in background radiation and from radioactive substances introduced into the body. This requires quantitative data on the accumulation of radioactive material on the ground and in the body." This then is the problem and the available literature seems to point out that at the moment, exposure due to faHout is of lesser order of magnitude than that due to natural radiation, and hence of even less concern. It may be concluded that all steps designed to minimize fr-radiation of human population will be to the benefit of human health. Such steps include the avoidance of unnecessary exposure resulting from man-made sources and the cessation of environmental contamination by nuclear weapons explosion. The citizens of any country, however, are primarily concerned about the military safety of their country and hence the authorRADIOACTIVE FALLOUT 101 ities are expected to keep abreast of new weapons development. In terms of their own national security, therefore, countries undertaking nuclear weapons are justified especially if it is recalled that estimated damage resulting from such tests is well within tolerable limits. However, in fairness to all, it is only proper that these tests be held to a minimum consistent with scientific and military requirements, if it is not possible to eliminate them entirely. REFEllENCES 1. EISENBUD, M. and HARLEY, J, H.: Radioactive Dust from Nuclear Detonation, Science, 11;:141·147. (February 13), 19!)3. 2. EISENBUD, M. and HARLEY, J. H.: Radioactive Fallout in the United States, Seien€!e, 121:677-680 (May 13). 1955. 3. EISENBUD, M. and HARLEY, J. H.: Long Term Fallout, Science, J21J':39!>-402 (Aug. 22), 19!)8. 4. LIBBY, W. F.: Radioactive Fullout, Proceedings of the National Academy of Science of the U.S.A., H :800-81!1 (August), 19!)8. 6. YANO, NAOSHI and NARUSE, HIROSHI: Artificial Radioactive Dust. Research in the Effect and Influences of the Nuclear Bomb Test Explosion, Japun Societ~· for the Promotion of Sciences, 1 :137, l!)!j6, G. UNITED NATIONS: Report of the l"nited Nations Scientific Committee on the Effect of Atomic Radiation. U.N. General Assembly Official Records, 1:ith Sl.'ssion. Supplement No. 17, 1958, New York, p. !18. 7. MIYAKE, Y.: The Artificiul Uudio;Lctivity in Hain Water Ollserved in Ja1mn, 1054-1956. Hesearch in th<> Effects and Influences of the Nuclear Bomb 'l'••st Explosion, Jarmn Society for the Promotion or S1:ienre, J:lt•l·l.-,:?, 195ti. 8. WORLD HEALTH OHGANIZATION: Effect of Radiation on Hu111an Heredity. Re11ort of a WHO Gl'our1, 1!)57, Wol'ld Health Orgnnization, Palais dei; Nntion~, GC'11e\·a, p. 11. 9. ADVISORY COMMITTEE ON lllOLOGY AND MEDICINE: Statement on Rudioadiw· Fallout, Anwrican .~kientist, 6-':l!JS-150 (.June), 1958. 10. U.S. DEPARTMENT OF COMMEltCE: Handbook 5:?. Maximum ('.,rmh;iiiblc Amounts of Hadioisotupes in the Hum1m Body and Maximum Permissible Concentration in Air and in Water, 1953, Nation11I Bure11.u of Slandards, 111>. 4, 11.
pages: 87-101