Site (NTS) began in January 1951, and the first nuclear weapon was detonated then.“ Of more than 600 clouds from 40 subsurface blasts trav- eled beyond site boundaries, contami- detonations, 183 were in the atmo- nating Utah,including the 100-kt “Sedan” in 1962 and “Coulomniers” in were not blowing toward Las Vegas was compromised by failure to activate radiation monitoring apparatus sphere (1951 through 1962). Tests were usually conducted when winds and Los Angeles, which were 140 km and 420 km from ground zero (GZ), respectively. At least 87 of the 121 atmospheric tests between 1951 and 1958 caused offsite contamination, and 28 (>620 kilotons[kt], totally) lay down a swath of radioactive fallout over Utah.’ Exact patterns were unpredictable and depended on the presence of functioning monitoring devices in local areas. The nuclear bomb “Small Boy” of about 1 kt was detonated on a tower 3 m high (July 14, 1962) and produced a “hot spot” af 100 rad/hr 540 km downwind (48.5°) from GZ in the Orem, Utah, area.‘ Within a radius of 8 to 16 km around this spot, the radiation dosage rate increased by 25 times. There may have been manyother such areas that were not detected. An infinite dose of 100 rad was calculated for an area on the highway between St George, Utah, and Cedar City, Utah (228 km and 276 km from GZ, respectively), after the detonation of “Harry,” and offsite doses of similar magnitude were reported for detonations of “Nancy,” “Simon,” “Badger,” and “Boltzman” (Harold A. Knapp, PhD, US Defense Communications Agency, oral communication, Nov 5, 1982). High explosive tests were later made to study the dispersion of plutonium or uranium from nuclear weapons, measurably contaminating over 250,000 sq km, with most contamina- tion occurring in northern Nevada and Utah. The highest offsite plutonium concentration reported was 9.6 picocuries per square centimeter (pCi/sq em), two orders of magnitude greater than that produced by weaponsfallout for nearby states downwind from the NTS and three orders greater than for states more distant from the NTS.’ (A picocurie of a radioactive isotope of an element is a quantity sufficient to produce 2.2 disintegrations per minute. Each disintegration releases ionizing radiation. There are eight important isotopes of plutonium, but “Pu is the predominant isotope and has a half-life of 24,390 years.') Radioactive plumes and JAMA, Jan 13, 1984—Vol 251, No. 2 1977. Official monitoring of fallout during nuclear tests (Deseret News, Dee 4, 1979, p 8-B). After a test on May 19, 1953, more than 300 mR per hour (mR/hr) were observed “in and out of cars” in St George. Former Atomic Energy Commission Chairman, Lewis -Strauss noted that “East they got over Pioche and over St George which they apparently always pilaster.” “Estimates of dosage delivered by radioactive iodine to the thyroids of children in St George, Utah, who were less than five years old in 1953, vary between 500 and 2,500 ga ” (Michael May, PhD, Lawrence “Radiation Laboratory, Berkeley, Calif, written communication, Nov 29, 1965). These doses are of the same order of magnitude as those sustained by the Rongelap children, who also received 175 rad of wholebody radiation.’ Livestock received much higher doses, and deaths of more than 4,000 sheep in 1953 were associated with the passage of radioactive plumes or clouds. Harold Knapp, PhD, reported fetal lambs had received doses of 20,000 to 40,000 rad to the thyroid gland and sheep had received 1,500 to 6,000 rad to the gastrointestinal (GI) tract, where the external doses were estimated to be only 4 rad (oral communication, Nov 5, 1982). Sheep near Cedar City received 38 to 169 rad of external gamma radiation.’ Despite reports of high levels of radiation in Utah and Nevada, and in Salt Lake City, Denver, and points more distant, there have been few investigations. Important exposures of the Los Angeles population went virtually unnoticed." An increase in leukemia mortality in southwestern Utah (1950 through 1964) was reported in 1965 (EdwardS. Weiss, MSPH, Public Health Service, written communication) and corroborated in a follow-up study of leukemia deaths in children 14 years later.” More than 30 years have now passed since the first exposure of people in southwestern Utah to radioactive fallout. There have been external exposures to radioactive gases and particulates in theair, ar from contaminated soil, and intern exposures to radioactive isotopes i gested in food and water, or inhale and stored in the body. Many perso in this area milk cows andraise the own produce and meat and a: exposed to resuspended dust fro agricultural activities. Of some 2¢ longer-lived radionuclides released t the fissioning of uranium and plut: nium, there are radioactive isotope of every trace element and othe elements important in human nutr tion.’”’ Most are cumulative an become concentrated in the foo chain. The molecular, cellular, an developmental effects of these radic nuclides have been poorly studiec This is especially true of long-terr. effects on human reproduction. Be cause of the possibility of an effect o: residents of the high-fallout areas i) the United States, an empirical inves tigation of the incidence of all cance in Mormons was conducted in com munities in southwestern Utah. METHODS Selection of the study group requirec that religion be considered as a potentia confounding factor. Utah has the lowes cancer incidence of any state, attributed tc the life-style of members of the Churcho: Jesus Christ of Latter Day Saints, 01 Mormons.” Utah Mormons (72% of the population) have a cancer incidence 23% less than the national average. Utah nonMormons have a cancer incidence 16% greater than that of Mormons. Church members are urged to abstain from tobacco, alcohol, tea, and coffee, avoid extramarital sexual activity, conform to certain family customs, and pursue higher education. Furthermore, the Mormon population in Utah seems to have greaterstability. The beneficial effects of the Mormon life-style were also reported in Califcrnia. Because of these considerations, the cancer incidence in Mormons in the highfallout area in southwestern Utah (4,125) was compared with the cancerincidence in all Utah Mormons (population, 781,735 in July 1971). Towns with heavy fallout exposure included the St George area, Parowan, Paragonah, and Kanab, Utah; Fredonia, Ariz; and Bunkerville, Nev. A high-risk population was defined as those Mormon families or persons listed in 1951 telephonedirectories in these townsstill listed in the 1962 directories and who could be located in 1981. This roster was checked against church records. “Family” included all persons related by blood or marriage in Cancer and Radioactive Fallout—Johnson 231