Appendix D
Thyroid Cancer in Idaho 1970-1996

Christopher J. Johnson, MPH, Epidemiologist

Stacey L. Carson, ART, CTR, Director

Cancer Data Registry of Idaho

PO Box 1278

Boise, Idaho 83701-1278

(208) 338-5100 ext. 213 (phone)

(208) 338-7800 (FAX)

Following release of the National Cancer Institute's report of its study to assess Americans' exposure to radioactive iodine-131 from atmospheric nuclear bomb testing in the 1950s and 1960s at the Nevada Test Site, and pursuant to requests from the public, media, and health officials, staff at the Cancer Data Registry of Idaho (CDRI) conducted several analyses of thyroid cancer. This report describes the analyses of thyroid cancer incidence rates in Idaho, 1970-1996, and the ratio of female-to-male thyroid cancer cases by age group. Because four of the five counties in the United States with highest estimated exposure to iodine-131 from atmospheric nuclear bomb tests at the Nevada Test Site are located in Idaho (Blaine, Custer, Gem, and Lemhi), and public health services are delivered at the health district level, analyses were conducted at both the county and health district levels of geography (see Appendix for listing of counties by health district).

METHODS

Established in 1969, CDRI is a population-based cancer registry that collects incidence and survival data on cancer patients who reside in the state of Idaho at the time of diagnosis or who are diagnosed and/or treated for cancer in the state of Idaho. All cases of invasive thyroid cancer diagnosed among residents of the state of Idaho between January 1, 1970, and December 31, 1996, were included in these analyses.



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Exposure of the American People to Iodine-131 from Nevada Nuclear-Bomb Tests: Review of the National Cancer Institute Report and Public Health Implications Appendix D Thyroid Cancer in Idaho 1970-1996 Christopher J. Johnson, MPH, Epidemiologist Stacey L. Carson, ART, CTR, Director Cancer Data Registry of Idaho PO Box 1278 Boise, Idaho 83701-1278 (208) 338-5100 ext. 213 (phone) (208) 338-7800 (FAX) Following release of the National Cancer Institute's report of its study to assess Americans' exposure to radioactive iodine-131 from atmospheric nuclear bomb testing in the 1950s and 1960s at the Nevada Test Site, and pursuant to requests from the public, media, and health officials, staff at the Cancer Data Registry of Idaho (CDRI) conducted several analyses of thyroid cancer. This report describes the analyses of thyroid cancer incidence rates in Idaho, 1970-1996, and the ratio of female-to-male thyroid cancer cases by age group. Because four of the five counties in the United States with highest estimated exposure to iodine-131 from atmospheric nuclear bomb tests at the Nevada Test Site are located in Idaho (Blaine, Custer, Gem, and Lemhi), and public health services are delivered at the health district level, analyses were conducted at both the county and health district levels of geography (see Appendix for listing of counties by health district). METHODS Established in 1969, CDRI is a population-based cancer registry that collects incidence and survival data on cancer patients who reside in the state of Idaho at the time of diagnosis or who are diagnosed and/or treated for cancer in the state of Idaho. All cases of invasive thyroid cancer diagnosed among residents of the state of Idaho between January 1, 1970, and December 31, 1996, were included in these analyses.

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Exposure of the American People to Iodine-131 from Nevada Nuclear-Bomb Tests: Review of the National Cancer Institute Report and Public Health Implications Thyroid Cancer Incidence in Idaho, 1970-1996, by Birth Cohort and Overall A combination of direct and indirect age adjustment was used to compare the incidence rates of thyroid cancer among geographic areas and by birth cohort. The following provides an overview of the steps taken in the analysis. Step 1. The number of invasive cases of thyroid cancer diagnosed among residents of the state of Idaho, 1970-1996, were summed by sex, 5-year age group, county of residence, and year of diagnosis. The age groups were: 0-4, 5-9, 10-14, …, 85+. Cases with missing information on sex, age at diagnosis, or county were not included in the analysis. If birth year was unknown, it was imputed from diagnosis date and estimated age at diagnosis. Birth cohort was defined by birth year: before 1948, 1948-1958, and after 1958. Given the years that atmospheric nuclear bomb tests were conducted at the Nevada Test Site, and the fact that children aged 0-5 are biologically most sensitive to iodine-131, persons born during the time period 1948-1958 are thought to have been at the risk of highest exposure. The other birth cohorts were chosen for comparison purposes. Step 2. Population data were obtained from the U.S. Bureau of the Census. Data for 1970-1989 were available by sex and 5-year age-group. Data for 1990-1996 were available by sex and single-year age group. Single-year age group estimates were derived from 1970-1989 data by dividing the population in each 5-year age group into 5 equal parts. For example, if 1,000 persons were in the 5-year age group 15-19, 200 persons each were assigned to ages 15, 16, 17, 18, and 19. Separating the population data into single-year age groups was necessary to calculate age-adjusted rates by birth cohort. Step 3. Three birth cohorts were defined, again based upon differences due to age in estimated exposure to iodine-131 from atmospheric nuclear bomb tests at the Nevada Test Site: before 1948, 1948-1958, and after 1958. Population data were estimated for each of the birth cohorts, by county, sex, and 5-year age group. Two age breaks were defined and incremented by year of study. The lower age break was defined as: AGELOW = YEAR - 1958, and year was varied from 1970-1996, the years for which CDRI has reliable statewide case information. The upper age break was defined as: AGEHIGH = YEAR - 1948, and year was again varied from 1970-1996. AGELOW and AGEHIGH give the (truncated) ages a person would have been in each year, 1970-1996, given that they were born in the period 1948-1958. Thus, a person born from 1948-1958 would have been assigned ages 12-22 in 1970, and between 32 and 42 in 1990, etc. Population data were assigned to birth cohorts depending on single-year age group and year (1970-1996). For example, for the year 1970, persons aged 10 were assigned to the after-1958 birth cohort; persons aged 20 were assigned to the 1948-1958 birth cohort; and persons aged 30 were assigned to the before-1948 birth

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Exposure of the American People to Iodine-131 from Nevada Nuclear-Bomb Tests: Review of the National Cancer Institute Report and Public Health Implications cohort. Finally, population data were collapsed over age to yield estimates by birth cohort, county, sex, and 5-year age group. Step 4. The age-adjusted rate of invasive thyroid cancer for the state of Idaho, 1970-1996, was calculated by the direct method, using the 1970 U.S. population as standard. Age-specific rates for the state of Idaho were calculated for use in direct age adjustment. The result was an age-adjusted incidence rate of thyroid cancer for the state of Idaho, 1970-1996, of 4.22 cases per 100,000 person-years. Step 5. Age- and sex-specific rates for the state of Idaho for the time period 1970-1996 were calculated for use as standard rates in indirect age and sex adjustment. Step 6. For all birth cohorts combined, the numbers of observed and expected cases were calculated for each health district and county. Expected cases were calculated by applying the age- and sex-specific rates for the state of Idaho to the population by age and sex in each health district and county. Two-tailed p-values comparing the number of observed and expected cases were calculated using the Poisson probability distribution. Observed and expected cases, and p-values, were calculated separately for males, females, and both sexes combined. Step 7. The adjusted incidence rates for each health district and county were calculated as the standardized incidence ratio (observed/expected) multiplied by the age-adjusted rate from Step 4. For example, there were 314 cases observed, and 254.6 cases expected in Health District 4, yielding an adjusted incidence rate of (314/254.6) * 4.22 = 5.20 cases per 100,000 person-years. Step 8. Age- and sex-specific rates for the state of Idaho, 1970-1996, were calculated by birth cohort for use in indirect age and sex adjustment by birth cohort. (Step 5 was repeated by birth cohort.) Step 9. For each birth cohort, the number of observed and expected cases were calculated for each health district and county. Expected cases were calculated by applying the age- and sex-specific rates for the state of Idaho, by birth cohort (from Step 8), to the population by age and sex in each health district and county. Two-tailed p-values comparing the number of observed and expected cases were calculated using the Poisson probability distribution. Observed and expected cases, and p-values, were calculated separately for males, females, and both sexes combined, by birth cohort. Statistical significance was set at α = .05. Step 10. The adjusted rates for each health district and county were calculated by birth cohort as the standardized incidence ratio for that birth cohort (observed/expected) multiplied by the age-adjusted rate for all birth cohorts (from Step 4). For example, there were 87 cases observed and 69.4 expected in Health District 4

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Exposure of the American People to Iodine-131 from Nevada Nuclear-Bomb Tests: Review of the National Cancer Institute Report and Public Health Implications for the birth cohort 1948-1958, yielding an adjusted incidence rate of (87/69.4) * 4.22 = 5.29. The overall rate from Step 4 was used as the reference rate in order to facilitate comparisons across birth cohort for individual health districts and counties, and to allow comparisons among health districts and counties within birth cohort. See Box D.1 for a description of the Idaho population by health districts. Step 11. The adjusted rates for the state of Idaho were calculated by birth cohort using the standardized incidence ratio for that birth cohort (observed/expected), with expected cases based upon age- and sex-specific rates for all birth cohorts BOX D.1 Description of Idaho Population The population of the state of Idaho in 1996 was estimated to be 1,189,251, made up of 594,604 males and 594,647 females (U.S. Bureau of the Census). Idaho comprises 44 counties grouped into seven health districts. The composition of the health districts and population estimates by sex are shown below: District Counties Males Females District 1 Benewah, Bonner, Boundary, Kootenai, Shoshone 80,792 81,548 District 2 Clearwater, Idaho, Latah, Lewis, Nez Perce 49,574 48,568 District 3 Adams, Canyon, Gem, Owyhee, Payette, Washington 84,753 85,602 District 4 Ada, Boise, Elmore, Valley 147,684 149,119 District 5 Blaine, Camas, Cassia, Gooding, Jerome, Lincoln, Minidoka, Twin Falls 77,788 77,139 District 6 Bannock, Bear Lake, Bingham, Butte, Caribou, Franklin, Oneida, Power 77,425 77,227 District 7 Bonneville, Clark, Custer, Fremont, Jefferson, Lemhi, Madison, Teton  76,588 75,444

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Exposure of the American People to Iodine-131 from Nevada Nuclear-Bomb Tests: Review of the National Cancer Institute Report and Public Health Implications (from Step 5). For example, there were 271 cases observed and 256.9 expected in the state of Idaho, 1970-1996, among the 1948-1958 cohort, yielding an adjusted incidence rate of (271/256.9) * 4.22 = 4.45 cases per 100,000 person-years. The state of Idaho rates by birth cohort were designed to be compared to each other, and to the overall state of Idaho rate of 4.22 cases per 100,000 person-years. Ratio of Female-to-Male Thyroid Cancer Cases by Age Group and Birth Cohort The overall ratio of thyroid cancer cases among females versus males differed by birth cohort, with a ratio of 2.7 in the before-1948 cohort, 5.2 in the 1948-1958 cohort, and 5.3 in the after-1958 cohort. In order to examine if the differences in female-to-male ratios by birth cohort were an artifact of differing age-specific rates by sex, cumulative ratios of female-to-male cases were calculated by age group. For all invasive cases of thyroid cancer diagnosed among Idaho residents, 1970-1996, the numbers of cases were summed separately for males and females by 5-year age group and birth cohort. The cumulative ratios of female-to-male cases were calculated by 5-year age group and birth cohort. For example, for the age group 35-39, the cumulative female-to-male ratio in the before-1948 birth cohort was 5.0 (75 cases among females aged 39 years and younger, and 15 cases among males aged 39 years and younger). RESULTS The overall age-adjusted incidence rate of invasive thyroid cancer in Idaho, 1970-1996, was 4.22 cases per 100,000 person-years (see Table D.1). Incidence rates varied by geographic location, ranging from 3.28 cases per 100,000 person-years in Health District 2 to 5.20 cases per 100,000 person-years in Health District 4. There were significantly more cases of invasive thyroid cancer diagnosed among residents of Health District 4 than expected based upon rates in the state of Idaho (314 observed, 254.6 expected, p<.001), and the number of observed cases was higher than expected for both males and females. Ada County had significantly more cases of invasive thyroid cancer than expected based upon rates in the state of Idaho (276 observed, 221.4 expected, p<.001). None of the four Idaho counties with highest estimated exposure to iodine-131 showed an elevation in thyroid cancer cases from 1970-1996. Among the birth cohort born before 1948, the incidence rate of invasive thyroid cancer, 1970-1996, was 4.10 cases per 100,000 person-years (see Table D.2). There were significantly more cases observed than expected in Health District 4 and Ada County. None of the four Idaho counties with highest estimated exposure to iodine-131 showed an elevation in thyroid cancer cases from 1970-1996 in the birth cohort born before 1948.

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Exposure of the American People to Iodine-131 from Nevada Nuclear-Bomb Tests: Review of the National Cancer Institute Report and Public Health Implications Among the birth cohort born 1948-1958, the incidence rate of invasive thyroid cancer, 1970-1996, was 4.45 cases per 100,000 person-years (see Table D.3). There were significantly more cases observed than expected in Health District 4 and Ada County. None of the four Idaho counties with highest estimated exposure to iodine-131 showed an elevation in thyroid cancer cases from 1970-1996 in the birth cohort born 1948-1958. Although the incidence rate of invasive thyroid cancer, 1970-1996, was highest for the birth cohort born 1948-1958, the number of cases observed was not statistically significantly different from that expected based upon rates for all birth cohorts. Among the birth cohort born after 1958, the incidence rate of invasive thyroid cancer, 1970-1996, was 4.35 cases per 100,000 person-years (see Table D.4). There were significantly more cases observed than expected in Elmore County. None of the four counties with highest estimated exposure to iodine-131 showed an elevation in thyroid cancer cases from 1970-1996 in the birth cohort born after 1958. Regarding the female-to-male ratios for invasive thyroid cancer cases, the differences in the overall female-to-male ratios by birth cohort (see Table D.5) appear to be due to the higher age-specific thyroid cancer incidence rates in younger females as compared with younger males. In all three birth cohorts, the cumulative age-specific ratios were similar for the age groups 25-29, 30-34, and 35-39 (the only age groups for which comparisons are available across all three birth cohorts, as CDRI has reliable statewide cancer incidence data since 1970). SUMMARY AND CONCLUSIONS Thyroid cancer is relatively rare among all cancers, accounting for less than 2% of invasive cases in Idaho in 1996. The age-adjusted incidence rate of invasive thyroid cancer in Idaho, 1970-1996, was 4.22 cases per 100,000 person-years. In comparison, the Surveillance, Epidemiology, and End Results (SEER) rate for whites, 1973-1995, was 4.39 cases per 100,000 person-years. CDRI investigated thyroid cancer incidence in three birth cohorts to explore the relationship between age at the time of iodine-131 release from atmospheric nuclear bomb tests at the Nevada Test Site and thyroid cancer incidence. The number of invasive thyroid cancer cases in the state of Idaho, 1970-1996, was not statistically significantly higher than expected, based upon overall rates, for any of the three birth cohorts. Within each birth cohort, and for all cohorts combined, variation existed among health districts and counties in the incidence of thyroid cancer, with more marked variation observed among geographic areas with smaller populations. There are several limitations of the data that may have influenced the results of the analyses. The accuracy of the estimated incidence rates assumes similar case

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Exposure of the American People to Iodine-131 from Nevada Nuclear-Bomb Tests: Review of the National Cancer Institute Report and Public Health Implications TABLE D.1  Invasive Thyroid Cancer in Idaho, 1970-1996, Among All Birth Cohorts     All Cases                                     Male Cases                                   Female Cases                                 Residence Incidence Rate Observed Expected P-Value Observed Expected P-Value Observed Expected P-Value STATE OF IDAHO 4.22 1,119 n/a n/a 256 n/a n/a 863 n/a n/a HEALTH DISTRICT 1 3.60 127 148.9 0.074 26 35.2 0.132 101 113.7 0.250 HEALTH DISTRICT 2 3.28 85 109.4 0.018 18 25.8 0.141 67 83.6 0.072 HEALTH DISTRICT 3 4.34 165 160.6 0.751 39 37.4 0.838 126 123.2 0.826 HEALTH DISTRICT 4 5.20 314 254.6 0.000 70 55.5 0.067 244 199.2 0.002 HEALTH DISTRICT 5 4.59 171 157.2 0.291 37 36.9 1.000 134 120.3 0.232 HEALTH DISTRICT 6 3.52 126 151.0 0.042 34 34.3 1.000 92 116.7 0.021 HEALTH DISTRICT 7 4.03 131 137.2 0.631 32 30.9 0.897 99 106.3 0.515 ADA 5.26 276 221.4 0.000 63 47.7 0.039 213 173.7 0.004 ADAMS 4.13 4 4.1 1.000 2 1.1 0.570 2 3.0 0.834 BANNOCK 4.19 72 72.5 1.000 17 15.8 0.828 55 56.7 0.894 BEAR LAKE 4.64 8 7.3 0.887 2 1.8 1.000 6 5.5 0.949 BENEWAH 2.67 6 9.5 0.333 1 2.4 0.624 5 7.1 0.578 BINGHAM 3.29 30 38.5 0.190 11 8.9 0.553 19 29.7 0.050 BLAINE 4.80 16 14.1 0.674 4 3.2 0.783 12 10.9 0.815 BOISE 4.42 4 3.8 1.000 2 1.0 0.510 2 2.8 0.916 BONNER 3.40 25 31.0 0.322 6 7.6 0.733 19 23.4 0.424 BONNEVILLE 4.31 75 73.5 0.888 14 16.3 0.685 61 57.2 0.648 BOUNDARY 5.13 11 9.0 0.598 4 2.2 0.362 7 6.8 1.000 BUTTE 2.38 2 3.5 0.626 1 0.9 1.000 1 2.6 0.519 CAMAS 0.00 — 0.9 0.793 — 0.2 1.000 — 0.7 1.000 CANYON 4.67 113 102.1 0.305 28 23.1 0.354 85 79.0 0.532 CARIBOU 2.08 4 8.1 0.184 — 1.9 0.299 4 6.2 0.510 CASSIA 3.37 17 21.3 0.421 5 5.0 1.000 12 16.3 0.348 CLARK 0.00 — 0.9 0.821 — 0.3 1.000 — 0.6 1.000 CLEARWATER 3.93 11 11.8 0.969 2 3.0 0.843 9 8.8 1.000 CUSTER 7.91 9 4.8 0.112 5 1.2 0.017 4 3.6 0.957

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Exposure of the American People to Iodine-131 from Nevada Nuclear-Bomb Tests: Review of the National Cancer Institute Report and Public Health Implications     All Cases                                     Male Cases Female Cases                                 Residence Incidence Rate Observed Expected P-Value Observed Expected P-Value Observed Expected P-Value ELMORE 4.40 23 22.0 0.894 2 5.0 0.251 21 17.1 0.396 FRANKLIN 0.88 2 9.6 0.008 1 2.3 0.641 1 7.3 0.012 FREMONT 3.34 9 11.4 0.600 — 2.7 0.130 9 8.7 0.996 GEM 4.66 16 14.5 0.757 3 3.5 1.000 13 10.9 0.607 GOODING 3.87 13 14.2 0.888 3 3.6 1.000 10 10.6 1.000 IDAHO 2.47 10 17.1 0.094 1 4.3 0.140 9 12.8 0.363 JEFFERSON 2.90 11 16.0 0.255 4 3.8 1.000 7 12.2 0.164 JEROME 4.85 20 17.4 0.594 4 4.1 1.000 16 13.3 0.519 KOOTENAI 3.53 66 78.9 0.156 11 18.1 0.105 55 60.8 0.501 LATAH 3.40 27 33.5 0.295 6 7.4 0.771 21 26.1 0.372 LEMHI 4.29 9 8.9 1.000 2 2.2 1.000 7 6.6 0.989 LEWIS 0.87 1 4.8 0.092 — 1.2 0.580 1 3.6 0.249 LINCOLN 3.13 3 4.0 0.850 — 1.0 0.713 3 3.0 1.000 MADISON 4.17 18 18.2 1.000 7 3.5 0.134 11 14.7 0.409 MINIDOKA 4.51 23 21.5 0.806 1 5.1 0.074 22 16.4 0.216 NEZ PERCE 3.61 36 42.1 0.394 9 9.7 0.980 27 32.3 0.400 ONEIDA 3.21 3 3.9 0.889 — 1.0 0.749 3 3.0 1.000 OWYHEE 2.76 6 9.2 0.381 1 2.3 0.647 5 6.9 0.639 PAYETTE 3.21 15 19.7 0.344 1 4.7 0.106 14 15.0 0.924 POWER 2.82 5 7.5 0.486 2 1.7 1.000 3 5.7 0.352 SHOSHONE 3.92 19 20.4 0.863 4 4.9 0.902 15 15.5 1.000 TETON 0.00 — 3.6 0.053 — 0.9 0.808 — 2.7 0.131 TWIN FALLS 5.22 79 63.8 0.073 20 14.7 0.216 59 49.1 0.187 VALLEY 6.33 11 7.3 0.248 3 1.8 0.531 8 5.5 0.393 WASHINGTON 4.20 11 11.0 1.000 4 2.7 0.581 7 8.3 0.817 NOTES: The incidence rate for the state of Idaho is age adjusted to the standard 1970 U.S. population using the direct method. The incidence rates for the other geographic areas are the products of the standardized incidence ratios and the state age-adjusted rate. Expected cases are based upon age- and sex-specific rates for the state of Idaho. P-values compare observed and expected cases, are two-tailed, based upon the Poisson probability distribution.

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Exposure of the American People to Iodine-131 from Nevada Nuclear-Bomb Tests: Review of the National Cancer Institute Report and Public Health Implications TABLE D.2 Invasive Thyroid Cancer in Idaho, 1970-1996, Among Birth Cohort Born Before 1948     All Cases                                     Male Cases                                   Female Cases                                  Residence Incidence Rate Observed Expected P-Value Observed Expected P-Value Observed Expected P-Value STATE OF IDAHO 4.10 679 698.3 0.480 185 186.5 0.953 494 511.8 0.447 HEALTH DISTRICT 1 3.55 79 93.8 0.133 21 26.4 0.346 58 67.5 0.273 HEALTH DISTRICT 2 3.08 50 68.5 0.024 13 19.1 0.190 37 49.4 0.082 HEALTH DISTRICT 3 4.32 106 103.6 0.841 31 28.4 0.669 75 75.3 1.000 HEALTH DISTRICT 4 5.13 173 142.3 0.014 44 37.3 0.306 129 105.0 0.026 HEALTH DISTRICT 5 4.54 108 100.3 0.468 25 27.6 0.716 83 72.8 0.255 HEALTH DISTRICT 6 3.77 81 90.7 0.334 27 24.6 0.682 54 66.1 0.147 HEALTH DISTRICT 7 4.34 82 79.8 0.837 24 21.8 0.688 58 58.0 1.000 ADA 5.35 157 123.9 0.005 40 32.2 0.201 117 91.8 0.013 ADAMS 6.22 4 2.7 0.578 2 0.8 0.403 2 1.9 1.000 BANNOCK 4.41 43 41.2 0.815 13 10.9 0.595 30 30.3 1.000 BEAR LAKE 5.10 6 5.0 0.755 2 1.4 0.805 4 3.6 0.960 BENEWAH 3.45 5 6.1 0.854 1 1.8 0.915 4 4.3 1.000 BINGHAM 4.13 23 23.5 1.000 10 6.4 0.230 13 17.1 0.393 BLAINE 3.60 6 7.0 0.888 — 1.9 0.288 6 5.1 0.803 BOISE 5.52 3 2.3 0.805 2 0.7 0.319 1 1.6 1.000 BONNER 3.20 15 19.8 0.339 5 5.7 0.983 10 14.0 0.347 BONNEVILLE 4.35 44 42.7 0.882 8 11.3 0.420 36 31.4 0.459 BOUNDARY 6.62 9 5.7 0.254 3 1.6 0.458 6 4.1 0.459 BUTTE 0.00 — 2.4 0.187 — 0.7 0.990 — 1.7 0.377 CAMAS 0.00 — 0.6 1.000 — 0.2 1.000 — 0.4 1.000 CANYON 4.63 70 63.8 0.472 21 17.1 0.397 49 46.8 0.783 CARIBOU 1.65 2 5.1 0.232 — 1.4 0.494 2 3.7 0.567 CASSIA 3.13 10 13.5 0.422 4 3.7 1.000 6 9.8 0.286 CLARK 0.00 — 0.6 1.000 — 0.2 1.000 — 0.4 1.000 CLEARWATER 3.72 7 7.9 0.922 2 2.3 1.000 5 5.6 1.000 CUSTER 6.79 5 3.1 0.406 3 0.9 0.140 2 2.2 1.000

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Exposure of the American People to Iodine-131 from Nevada Nuclear-Bomb Tests: Review of the National Cancer Institute Report and Public Health Implications     All Cases                                     Male Cases                                   Female Cases                                  Residence Incidence Rate Observed Expected P-Value Observed Expected P-Value Observed Expected P-Value ELMORE 2.56 7 11.6 0.222 — 3.1 0.091 7 8.5 0.781 FRANKLIN 0.00 — 6.4 0.003 — 1.8 0.330 — 4.6 0.021 FREMONT 2.92 5 7.2 0.543 — 2.0 0.261 5 5.2 1.000 GEM 3.82 9 9.9 0.930 3 2.8 1.000 6 7.1 0.864 GOODING 4.28 10 9.9 1.000 3 2.8 1.000 7 7.0 1.000 IDAHO 2.55 7 11.6 0.216 1 3.4 0.298 6 8.2 0.573 JEFFERSON 3.48 8 9.7 0.735 4 2.8 0.598 4 6.9 0.357 JEROME 5.63 15 11.2 0.329 4 3.1 0.770 11 8.1 0.389 KOOTENAI 3.32 38 48.4 0.148 8 13.3 0.176 30 35.1 0.446 LATAH 2.83 12 17.9 0.192 3 4.9 0.562 9 13.0 0.333 LEMHI 4.20 6 6.0 1.000 2 1.8 1.000 4 4.3 1.000 LEWIS 1.24 1 3.4 0.292 — 1.0 0.741 1 2.4 0.610 LINCOLN 1.55 1 2.7 0.490 — 0.8 0.898 1 1.9 0.856 MADISON 7.13 14 8.3 0.087 7 2.2 0.014 7 6.1 0.821 MINIDOKA 3.71 12 13.6 0.790 — 3.8 0.044 12 9.8 0.568 NEZ PERCE 3.51 23 27.6 0.440 7 7.5 1.000 16 20.1 0.425 ONEIDA 3.02 2 2.8 0.943 — 0.8 0.908 2 2.0 1.000 OWYHEE 3.55 5 6.0 0.907 1 1.8 0.948 4 4.2 1.000 PAYETTE 3.18 10 13.3 0.457 1 3.7 0.237 9 9.6 1.000 POWER 4.73 5 4.5 0.923 2 1.2 0.709 3 3.2 1.000 SHOSHONE 3.66 12 13.9 0.746 4 3.9 1.000 8 10.0 0.673 TETON 0.00 — 2.2 0.225 — 0.6 1.000 — 1.5 0.429 TWIN FALLS 5.47 54 41.7 0.076 14 11.2 0.467 40 30.5 0.114 VALLEY 5.66 6 4.5 0.584 2 1.3 0.743 4 3.2 0.784 WASHINGTON 4.27 8 7.9 1.000 3 2.2 0.766 5 5.7 0.997 NOTES: The incidence rate for the state of Idaho is the product of the age adjusted rate for all birth cohorts using the 1970 standard U.S. population (direct age adjustment) and the standardized incidence ratio for this birth cohort compared with all birth cohorts (indirect age adjustment). The incidence rates for the other geographic areas are the products of the standardized incidence ratios for this cohort and the state age-adjusted rate. Expected cases for geography other than state are based upon age- and sex-specific rates for the state of Idaho for this cohort. P-values compare observed and expected cases, are two-tailed, based upon the Poisson probability distribution.

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Exposure of the American People to Iodine-131 from Nevada Nuclear-Bomb Tests: Review of the National Cancer Institute Report and Public Health Implications TABLE D.3  Invasive Thyroid Cancer in Idaho, 1970-1996, Among Birth Cohort Born 1948-1958     All Cases                                     Male Cases                                   Female Cases                                  Residence Incidence Rate Observed Expected P-Value Observed Expected P-Value Observed Expected P-Value STATE OF IDAHO 4.45 271 256.9 0.394 44 45.2 0.932 227 211.6 0.307 HEALTH DISTRICT 1 3.18 27 35.8 0.156 4 5.7 0.654 23 30.1 0.223 HEALTH DISTRICT 2 4.10 24 24.7 0.992 3 4.2 0.804 21 20.6 0.980 HEALTH DISTRICT 3 4.35 36 35.0 0.905 6 5.5 0.950 30 29.4 0.966 HEALTH DISTRICT 4 5.29 87 69.4 0.046 16 11.4 0.227 71 58.0 0.109 HEALTH DISTRICT 5 4.38 37 35.6 0.865 5 5.8 0.948 32 29.8 0.737 HEALTH DISTRICT 6 3.44 30 36.8 0.297 7 6.0 0.775 23 30.8 0.177 HEALTH DISTRICT 7 3.76 30 33.7 0.599 3 5.5 0.413 27 28.2 0.919 ADA 5.39 77 60.3 0.043 13 9.7 0.361 64 50.6 0.078 ADAMS 0.00 — 0.9 0.824 — 0.1 1.000 — 0.7 0.953 BANNOCK 4.20 19 19.1 1.000 4 3.1 0.741 15 16.0 0.930 BEAR LAKE 2.94 1 1.4 1.000 — 0.2 1.000 1 1.2 1.000 BENEWAH 0.00 — 2.2 0.228 — 0.4 1.000 — 1.8 0.329 BINGHAM 1.39 3 9.1 0.040 1 1.5 1.000 2 7.6 0.036 BLAINE 3.59 4 4.7 0.987 — 0.8 0.887 4 3.9 1.000 BOISE 4.15 1 1.0 1.000 — 0.2 1.000 1 0.8 1.000 BONNER 3.90 7 7.6 1.000 1 1.2 1.000 6 6.3 1.000 BONNEVILLE 4.28 19 18.7 1.000 3 3.0 1.000 16 15.7 1.000 BOUNDARY 3.96 2 2.1 1.000 1 0.4 0.594 1 1.8 0.940 BUTTE 11.27 2 0.7 0.346 1 0.1 0.240 1 0.6 0.925 CAMAS 0.00 — 0.2 1.000 — 0.0 1.000 — 0.2 1.000 CANYON 4.53 25 23.3 0.774 5 3.7 0.613 20 19.6 0.988 CARIBOU 4.43 2 1.9 1.000 — 0.3 1.000 2 1.6 0.946 CASSIA 4.46 5 4.7 1.000 1 0.8 1.000 4 4.0 1.000 CLARK 0.00 — 0.2 1.000 — 0.0 1.000 — 0.1 1.000 CLEARWATER 6.78 4 2.5 0.480 — 0.4 1.000 4 2.1 0.311 CUSTER 7.50 2 1.1 0.621 — 0.2 1.000 2 0.9 0.480

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Exposure of the American People to Iodine-131 from Nevada Nuclear-Bomb Tests: Review of the National Cancer Institute Report and Public Health Implications     All Cases                                     Male Cases                                   Female Cases                                  Residence Incidence Rate Observed Expected P-Value Observed Expected P-Value Observed Expected P-Value ELMORE 3.46 5 6.1 0.862 2 1.2 0.645 3 4.9 0.549 FRANKLIN 4.42 2 1.9 1.000 1 0.3 0.550 1 1.6 1.000 FREMONT 3.37 2 2.5 1.000 — 0.4 1.000 2 2.1 1.000 GEM 7.37 5 2.9 0.325 — 0.4 1.000 5 2.4 0.196 GOODING 4.64 3 2.7 1.000 — 0.5 1.000 3 2.3 0.793 IDAHO 2.38 2 3.5 0.626 — 0.6 1.000 2 2.9 0.879 JEFFERSON 2.23 2 3.8 0.541 — 0.6 1.000 2 3.2 0.777 JEROME 4.39 4 3.8 1.000 — 0.6 1.000 4 3.2 0.805 KOOTENAI 3.01 14 19.6 0.240 2 3.1 0.818 12 16.6 0.316 LATAH 5.28 11 8.8 0.541 2 1.6 0.918 9 7.2 0.608 LEMHI 2.25 1 1.9 0.880 — 0.3 1.000 1 1.6 1.000 LEWIS 0.00 — 0.9 0.803 — 0.2 1.000 — 0.8 0.939 LINCOLN 0.00 — 0.8 0.858 — 0.1 1.000 — 0.7 0.997 MADISON 3.70 4 4.6 1.000 — 0.7 0.983 4 3.9 1.000 MINIDOKA 7.05 8 4.8 0.224 — 0.8 0.900 8 4.0 0.101 NEZ PERCE 3.29 7 9.0 0.654 1 1.4 1.000 6 7.6 0.742 ONEIDA 5.84 1 0.7 1.000 — 0.1 1.000 1 0.6 0.909 OWYHEE 2.14 1 2.0 0.829 — 0.3 1.000 1 1.6 1.000 PAYETTE 2.11 2 4.0 0.477 — 0.6 1.000 2 3.4 0.686 POWER 0.00 — 1.9 0.301 — 0.3 1.000 — 1.6 0.411 SHOSHONE 3.94 4 4.3 1.000 — 0.7 1.000 4 3.6 0.970 TETON 0.00 — 0.9 0.821 — 0.2 1.000 — 0.7 0.960 TWIN FALLS 3.98 13 13.8 0.971 4 2.2 0.358 9 11.6 0.556 VALLEY 8.51 4 2.0 0.280 1 0.3 0.569 3 1.6 0.458 WASHINGTON 6.40 3 2.0 0.635 1 0.3 0.544 2 1.7 0.990 NOTES: The incidence rate for the state of Idaho is the product of the age adjusted rate for all birth cohorts using the 1970 standard U.S. population (direct age adjustment) and the standardized incidence ratio for this birth cohort compared with all birth cohorts (indirect age adjustment). The incidence rates for the other geographic areas are the products of the standardized incidence ratios for this cohort and the state age-adjusted rate. Expected cases for geography other than state are based upon age- and sex-specific rates for the state of Idaho for this cohort. P-values compare observed and expected cases, are two-tailed, based upon the Poisson probability distribution.

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Exposure of the American People to Iodine-131 from Nevada Nuclear-Bomb Tests: Review of the National Cancer Institute Report and Public Health Implications TABLE D.4 Invasive Thyroid Cancer in Idaho, 1970-1996, Among Birth Cohort Born After 1958     All Cases                                     Male Cases                                   Female Cases                                  Residence Incidence Rate Observed Expected P-Value Observed Expected P-Value Observed Expected P-Value STATE OF IDAHO 4.35 169 163.9 0.708 27 24.3 0.634 142 139.6 0.859 HEALTH DISTRICT 1 4.57 21 19.4 0.774 1 3.1 0.367 20 16.3 0.416 HEALTH DISTRICT 2 2.92 11 15.9 0.265 2 2.5 1.000 9 13.4 0.282 HEALTH DISTRICT 3 4.41 23 22.0 0.887 2 3.5 0.631 21 18.5 0.615 HEALTH DISTRICT 4 5.20 54 43.8 0.152 10 6.9 0.329 44 36.9 0.279 HEALTH DISTRICT 5 5.20 26 21.1 0.336 7 3.5 0.137 19 17.6 0.793 HEALTH DISTRICT 6 2.74 15 23.1 0.099 — 3.7 0.050 15 19.4 0.375 HEALTH DISTRICT 7 3.39 19 23.6 0.398 5 3.7 0.621 14 20.0 0.213 ADA 4.66 42 38.1 0.565 10 5.9 0.159 32 32.1 1.000 ADAMS 0.00 — 0.5 1.000 — 0.1 1.000 — 0.4 1.000 BANNOCK 3.49 10 12.1 0.678 — 1.8 0.321 10 10.2 1.000 BEAR LAKE 4.92 1 0.9 1.000 — 0.1 1.000 1 0.7 1.000 BENEWAH 3.60 1 1.2 1.000 — 0.2 1.000 1 1.0 1.000 BINGHAM 2.89 4 5.9 0.611 — 1.0 0.747 4 4.9 0.928 BLAINE 10.53 6 2.4 0.072 4 0.4 0.002 2 2.0 1.000 BOISE 0.00 — 0.5 1.000 — 0.1 1.000 — 0.4 1.000 BONNER 3.41 3 3.7 0.984 — 0.6 1.000 3 3.1 1.000 BONNEVILLE 4.23 12 12.0 1.000 3 2.0 0.648 9 10.0 0.922 BOUNDARY 0.00 — 1.2 0.621 — 0.2 1.000 — 1.0 0.759 BUTTE 0.00 — 0.4 1.000 — 0.1 1.000 — 0.3 1.000 CAMAS 0.00 — 0.1 1.000 — 0.0 1.000 — 0.1 1.000 CANYON 5.04 18 15.1 0.514 2 2.4 1.000 16 12.7 0.420 CARIBOU 0.00 — 1.1 0.693 — 0.2 1.000 — 0.9 0.828 CASSIA 2.86 2 3.0 0.867 — 0.5 1.000 2 2.5 1.000 CLARK 0.00 — 0.1 1.000 — 0.0 1.000 — 0.1 1.000 CLEARWATER 0.00 — 1.3 0.566 — 0.2 1.000 — 1.0 0.713 CUSTER 14.82 2 0.6 0.224 2 0.1 0.009 — 0.5 1.000

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Exposure of the American People to Iodine-131 from Nevada Nuclear-Bomb Tests: Review of the National Cancer Institute Report and Public Health Implications     All Cases                                     Male Cases                                   Female Cases                                  Residence Incidence Rate Observed Expected P-Value Observed Expected P-Value Observed Expected P-Value ELMORE 10.58 11 4.4 0.011 — 0.8 0.918 11 3.6 0.003 FRANKLIN 0.00 — 1.3 0.538 — 0.2 1.000 — 1.1 0.671 FREMONT 5.22 2 1.6 0.961 — 0.3 1.000 2 1.3 0.767 GEM 5.11 2 1.7 0.984 — 0.3 1.000 2 1.4 0.796 GOODING 0.00 — 1.6 0.405 — 0.3 1.000 — 1.3 0.539 IDAHO 2.23 1 1.9 0.870 — 0.3 1.000 1 1.6 1.000 JEFFERSON 1.69 1 2.5 0.574 — 0.4 1.000 1 2.1 0.771 JEROME 1.83 1 2.3 0.659 — 0.4 1.000 1 1.9 0.858 KOOTENAI 5.26 14 11.2 0.480 1 1.8 0.950 13 9.5 0.321 LATAH 2.47 4 6.8 0.376 1 1.0 1.000 3 5.8 0.332 LEMHI 9.16 2 0.9 0.471 — 0.1 1.000 2 0.8 0.365 LEWIS 0.00 — 0.5 1.000 — 0.1 1.000 — 0.4 1.000 LINCOLN 18.17 2 0.5 0.159 — 0.1 1.000 2 0.4 0.115 MADISON 0.00 — 5.4 0.009 — 0.6 1.000 — 4.8 0.017 MINIDOKA 4.16 3 3.0 1.000 1 0.5 0.797 2 2.5 1.000 NEZ PERCE 4.69 6 5.4 0.906 1 0.8 1.000 5 4.6 0.957 ONEIDA 0.00 — 0.4 1.000 — 0.1 1.000 — 0.4 1.000 OWYHEE 0.00 — 1.3 0.572 — 0.2 1.000 — 1.0 0.723 PAYETTE 5.22 3 2.4 0.873 — 0.4 1.000 3 2.0 0.668 POWER 0.00 — 1.1 0.643 — 0.2 1.000 — 0.9 0.775 SHOSHONE 5.98 3 2.1 0.710 — 0.3 1.000 3 1.8 0.525 TETON 0.00 — 0.6 1.000 — 0.1 1.000 — 0.5 1.000 TWIN FALLS 6.16 12 8.2 0.258 2 1.3 0.771 10 6.9 0.318 VALLEY 4.82 1 0.9 1.000 — 0.1 1.000 1 0.7 1.000 WASHINGTON 0.00 — 1.1 0.645 — 0.2 1.000 — 1.0 0.772 NOTES: The incidence rate for the state of Idaho is the product of the age adjusted rate for all birth cohorts using the 1970 standard U.S. population (direct age adjustment) and the standardized incidence ratio for this birth cohort compared with all birth cohorts (indirect age adjustment). The incidence rates for the other geographic areas are the products of the standardized incidence ratios for this cohort and the state age-adjusted rate. Expected cases for geography other than state are based upon age- and sex-specific rates for the state of Idaho for this cohort. P-values compare observed and expected cases, are two-tailed, based upon the Poisson probability distribution.

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Exposure of the American People to Iodine-131 from Nevada Nuclear-Bomb Tests: Review of the National Cancer Institute Report and Public Health Implications TABLE D.5 Ratio of Female-to-Male Invasive Thyroid Cancer Cases by Age Group and Birth Cohort   Birth Cohort Born Before 1948    Birth Cohort Born 1948-1958         Birth Cohort Born After 1958            Age Group Female Cases Male Cases Cumulative F:M Ratio Female Cases Male Cases Cumulative F:M Ratio Female Cases Male Cases Cumulative F:M Ratio 0- 4             0 1 0.0 5- 9             2 0 2.0 10-14             5 3 1.8 15-19       7 2 3.5 21 3 4.0 20-24       22 5 4.1 42 3 7.0 25-29 8 1 8.0 37 3 6.6 44 9 6.0 30-34 33 4 8.2 58 9 6.5 25 5 5.8 35-39 34 10 5.0 50 14 5.3 3 3 5.3 40-44 52 20 3.6 42 11 4.9       45-49 70 15 3.9 11 0 5.2       50-54 55 23 3.5             55-59 60 20 3.4             60-64 50 29 3.0             65-69 37 17 2.9             70-74 37 22 2.7             75-79 30 12 2.7             80-84 16 10 2.6             85+ 12 2 2.7             Total 494 185 2.7 227 44 5.2 142 27 5.3

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Exposure of the American People to Iodine-131 from Nevada Nuclear-Bomb Tests: Review of the National Cancer Institute Report and Public Health Implications ascertainment rates across geographic areas, and depends upon the accuracy of the population estimates generated by the U.S. Bureau of the Census and apportionment of 5-year age group data into five equal single-year groups. The analyses did not account for in- or out-migration of cases. Cases among previous Idaho residents who moved to another state prior to diagnosis were not accounted for, but cases among persons who previously resided in other states, but moved to Idaho prior to diagnosis, were counted as Idaho cases. This same limitation exists at the county level for county-specific analyses. Many of the statistics, particularly for the county analyses by birth cohort, are based upon small numbers of cases. Incidence rates based upon 10 or fewer cases (numerator) should be interpreted with caution. None of the four Idaho counties with highest estimated exposure to iodine-131 showed an elevation in thyroid cancer cases from 1970-1996 in the birth cohort born during 1948-1958, which was estimated to have received the highest exposure to iodine-131. Although the overall female-to-male thyroid case ratios differed by birth cohort, this result was confounded by age, as the cumulative age-specific ratios are similar in each birth cohort.