# Mortality Among Workers at the Savannah River Nuclear Fuels Production Facility

**Donna L. Cragle and Janice P. Watkins, Center for Epidemiologic
Research;**

**Kathryn Robertson-DeMers, Bechtel Hanford, Inc.**

#### Donna Cragle, Oak Ridge Associated Universities, P.O. Box 117, Oak Ridge, TN 37831-0117

**Key Words:** mortality study, radiation exposure, leukemia,
occupational cohort, trend test

### Introduction

Since 1952 the Savannah River Site (SRS), located in Aiken, South
Carolina, has operated as a Department of Energy (DOE) production
facility for nuclear fuels and other materials. A previous study^1^
through 1980 of 9,860 white males employed at least 90 consecutive days
at the SRS between 1952 and 1974 found an increased number of leukemia
deaths among hourly employees compared to expected numbers from the U.S.
white males (13 observed versus 7.95 expected). The current
investigation of the same cohort included six additional years of
follow-up and radiation dosimetry data for 99% of the cohort.

### Methods

Vital status was ascertained through 1986 using a combination of sources
including the Social Security Administration, Pension Benefits
Incorporated, and the National Death Index. Death certificates were
coded to the eighth revision of the International Classification of
Diseases, Adapted for Use in the United States.

Radiation monitoring files provided by the plant included yearly and
accumulated shallow dose equivalent, deep dose equivalent,
tritium-effective dose equivalent, and neutron dose equivalent. Of the
9,860 cohort members, 9,757 had external radiation doses available from
1943 to 1986. External doses obtained at other DOE facilities were
included in calculating the annual dose estimates.

Standardized Mortality Ratios (SMRs) were stratified by paycode as a
surrogate for socioeconomic status. Person-years were calculated from
the hire date plus 90 days. Dose response analysis consisted of both
trend tests and Poisson regression using time-dependent cumulative
external dose stratified into nine groups with mSv ranges as follows: 0,
\>0 -, 5 -, 10 -, 20-, \..., 160 -, 320 or greater. The person-years
weighted mean dose in each cell was used in analysis, which approximated
modeling dose as continuous. Poisson trend tests^2^ stratified by age,
calendar period, and paycode for 14 selected cancer causes of death used
radiation doses lagged ten years (two years for leukemia) to screen for
possible dose-response relationships. Dose-response analysis for
leukemia excluded chronic lymphocytic leukemia (CCL) and included two
cases where leukemia was the non-underlying cause of death. Poisson
regression modeling based on maximum likelihood methods produced
parameter estimates based on an excess relative risk (ERR) model in
which relative risk has the form 1 + x, with the change in ERR per Sv.
The regression used an internal comparison group of unexposed workers at
the reference level of all possible confounders included, which were
calendar period (before 1970, 1970-79, 1980-86), paycode (hourly,
salaried), and age (natural log of age/52.5). Confidence intervals were
likelihood based.

**Results**

We obtained and coded death certificates for 1,686 (97.9 %) of the 1,722
deaths ascertained (17.5 % of the cohort) with 376 occurring among the
2,561 salaried workers (14.7 %) and 1,346 occurring among the 7,299
non-salaried workers (18.4 %). Table 1 shows that few SMRs are greater
than one and at the five-percent significance level none were
significantly elevated. There were significant deficits in several
categories, including: all causes, all cancers, cancer of the digestive
organs and peritoneum (salaried only), lung cancer (salaried only),
brain cancer (hourly only), all diseases of the circulatory system,
arteriosclerotic heart disease, all respiratory diseases, all diseases
of the digestive system, and all external causes of death (salaried
only). Both salaried and non-salaried groups exhibited a slight, but not
statistically significant, increase in deaths attributable to leukemia.

Total population dose with no lag was 399 Sv with the mean, median, and
maximum final cumulative doses 40.5, 7.4, and 475.6 mSv, respectively.
The skewed distribution is due to many doses being zero. For a two-year
lag the mean and median drop to 40 and 7.2, and for a ten-year lag they
drop to 35.8 and 6.1.

Table 2 presents trend test statistics for selected cancers, and
observed and expected deaths by external dose group. Only leukemia
results indicate a trend of rising mortality with increasing radiation
dose. This trend is significant for the ten-year lag and the two-year
lag with nonunderlying causes of death included; one occurred in the 0-5
mSv category and the other in the 80-160 mSv category.

The parameter estimate for increased risk per Sievert for leukemia
mortality was 13.61 \[90% confidence interval (0.61,50.62)\]. The
likelihood ratio test statistic, which is the differences in the
deviance of the models with and without dose, was 3.64 and may be
compared for statistical significance to a chi-square distribution with
one degree of freedom whose 90th percentile is 2.71 and 95th percentile
is 3.84.

### Discussion

Studies of two other cohorts of workers in the radiation industry have
found increases in the rate of leukemia when compared to standard
national populations but did not identify a significant dose-response
relationship between leukemia and dose.^3,9^ Other studies^5,7,8,12^
found no increase in leukemia deaths but did identify a significant
dose-response when controlling for age, calendar period and the
exclusion of chronic lymphocytic leukemia. However, recent analyses of
the Hanford population^6^ do not indicate increased risks.

Table 3 presents characteristics reported in recently published studies
of populations occupationally exposed to ionizing. Generally, the five
studies^5,7,8,12^ (including the present study) that show positive
dose-response relationships for leukemia are those that have the highest
average cumulative dose per radiation worker. There does not appear to
be a similar relationship between positive risk estimates for cancer and
average cumulative dose. Comparison of ERR estimates for these
populations show the estimate for SRS (13.61 per Sv) is commensurate
with the estimates derived for the Atomic Energy of Canada^12^ (19.0 per
Sv) and Sellafield^9^(13.92 per Sv) populations. The SRS estimate is
much higher than those for the International Combined population^10^
(2.18 per Sv) and the A-bomb survivors^12^ (3.67 per Sv). Highest
estimates are based on the fewest number of deaths while lowest
estimates are based on the most deaths. Confidence intervals for all
estimates overlap. Since leukemia is a relatively rare disease, there
will be few deaths in small population studies, leading to uncertainty
in the risk estimates.

Modeling of prostate cancers was not attempted because the dose
distribution among the individuals who died with prostate cancer or who
were known to have prostate cancer but actually died of another cause,
revealed that 19 of the 22 individuals had a total cumulative dose of
less than 20 mSv. With additional years of follow-up, examination of the
prostate cancers with respect to radiation exposure, particularly
tritium, should be undertaken, particularly in light of findings in
Atomic Weapons Establishment^9^ workers and the potential for exposure
to tritium at the Savannah River Site.

### REFERENCES

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    nuclear fuels production facility. Am J Ind Med 1988;14:379-401.

2.  Breslow, NE and Day, NE. Statistical Methods in Cancer Research.
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3.  Wing S, Shy CM, Wood JL, *et al*. Mortality among workers at Oak
    Ridge National Laboratory: evidence of radiation effects in
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4.  Beral V, Fraser P, Carpenter L, *et al*. Mortality of employees of
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5.  Kendall GM, Muirhead CR, MacGibbon BH, *et al*. Mortality and
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    Registry for Radiation Workers. Br Med J 1992;304:220-25.

6.  Gilbert ES, Omohundro E, Buchanan JA, *et al*. Mortality of workers
    at the Hanford Site: 1945-1986. Health Phys 1993;64:577-90.

7.  Douglas AJ, Omar RZ, and Smith PG. Cancer mortality and morbidity
    among workers at the Sellafield plant of British Nuclear Fuels. Br J
    Cancer 1994;70:1232-1243.

8.  Carpenter L, Higgins C, Douglas A, *et al*. Combined analysis of
    mortality in three United Kingdom nuclear industry work forces,
    1946-1988. Radiat Res 1994;138:224-38.

9.  Fraser P, Carpenter L, Maconochie N, et al. Cancer mortality and
    morbidity in employees of United Kingdom Atomic Energy Authority,
    1946-1986. Br J Cancer 1993;67:615-624.

10. Cardis E, Gilbert ES, Howe G, et al. Effects of low dose rates of
    external ionizing radiation: cancer mortality among nuclear industry
    workers in three countries. Radiat Res 1995;142:117-132.

11. Gribbin MA, Weeks JL and Howe GR. Cancer mortality (1956-1985) among
    male employees of Atomic Energy of Canada Limited with respect to
    occupational exposure to external low-linear transfer ionizing
    radiation. Radiat Res 1993;133:375-380.

12. Shimizu Y, Kato H and Schull WJ. Studies of the mortality of A-bomb
    survivors. 9. Mortality, 1950-1985: Part 2. Cancer mortality based
    on the recently revised doses (DS 86). Radiat Res 1990;121:120-141.

+-------------------------------+---+----+---------+----+----+-------+
| # Table 1. SMRS fo            |   |    |         |    |    |       |
| r Salaried and Hourly Workers |   |    |         |    |    |       |
+-------------------------------+---+----+---------+----+----+-------+
|                               | * |    |         | *  |    |       |
|                               | * |    |         | *[ |    |       |
|                               | [ |    |         | Ho |    |       |
|                               | S |    |         | ur |    |       |
|                               | a |    |         | ly |    |       |
|                               | l |    |         | (N |    |       |
|                               | a |    |         | =7 |    |       |
|                               | r |    |         | ,2 |    |       |
|                               | i |    |         | 99 |    |       |
|                               | e |    |         | )] |    |       |
|                               | d |    |         | {. |    |       |
|                               | ( |    |         | un |    |       |
|                               | N |    |         | de |    |       |
|                               | = |    |         | rl |    |       |
|                               | 2 |    |         | in |    |       |
|                               | , |    |         | e} |    |       |
|                               | 5 |    |         | ** |    |       |
|                               | 6 |    |         |    |    |       |
|                               | 1 |    |         |    |    |       |
|                               | ) |    |         |    |    |       |
|                               | ] |    |         |    |    |       |
|                               | { |    |         |    |    |       |
|                               | . |    |         |    |    |       |
|                               | u |    |         |    |    |       |
|                               | n |    |         |    |    |       |
|                               | d |    |         |    |    |       |
|                               | e |    |         |    |    |       |
|                               | r |    |         |    |    |       |
|                               | l |    |         |    |    |       |
|                               | i |    |         |    |    |       |
|                               | n |    |         |    |    |       |
|                               | e |    |         |    |    |       |
|                               | } |    |         |    |    |       |
|                               | * |    |         |    |    |       |
|                               | * |    |         |    |    |       |
+-------------------------------+---+----+---------+----+----+-------+
| # Cause of Death              | # | #  | **95%   | #  | #  | **95% |
|                               |   |  S | CI**    |  O |  S | CI**  |
|                               | O | MR |         | bs | MR |       |
|                               | b |    |         |    |    |       |
|                               | s |    |         |    |    |       |
+-------------------------------+---+----+---------+----+----+-------+
|                               |   |    |         |    |    |       |
+-------------------------------+---+----+---------+----+----+-------+
| All causes (001-998)          | 3 | 0. | (0.5    | 1  | 0. | (     |
|                               | 7 | 60 | 4,0.67) | ,3 | 85 | 0.80, |
|                               | 6 |    |         | 46 |    | 0.90) |
+-------------------------------+---+----+---------+----+----+-------+
| All cancers (140-209)         | 1 | 0. | (0.5    | 3  | 0. | (     |
|                               | 0 | 71 | 8,0.87) | 11 | 86 | 0.76, |
|                               | 2 |    |         |    |    | 0.96) |
+-------------------------------+---+----+---------+----+----+-------+
| Cancer of buccal cavity and   | 3 | 0. | (0.1    | 11 | 0. | (     |
| pharynx (140-149)             |   | 69 | 4,2.01) |    | 97 | 0.48, |
|                               |   |    |         |    |    | 1.74) |
+-------------------------------+---+----+---------+----+----+-------+
| Cancer of digestive organs,   | 2 | 0. | (0.3    | 72 | 0. | (     |
| peritoneum (150-159)          | 2 | 62 | 9,0.94) |    | 82 | 0.64, |
|                               |   |    |         |    |    | 1.04) |
+-------------------------------+---+----+---------+----+----+-------+
| > Cancer of stomach (151)     | 3 | 0. | (0.1    | 11 | 0. | (     |
|                               |   | 54 | 1,1.58) |    | 82 | 0.41, |
|                               |   |    |         |    |    | 1.46) |
+-------------------------------+---+----+---------+----+----+-------+
| > Cancer of large intestine   | 9 | 0. | (0.3    | 27 | 0. | (     |
| > (153)                       |   | 74 | 4,1.40) |    | 90 | 0.60, |
|                               |   |    |         |    |    | 1.32) |
+-------------------------------+---+----+---------+----+----+-------+
| > Cancer of rectum (154)      | 1 | 0. | (0.0    | 5  | 0. | (     |
|                               |   | 30 | 0,1.65) |    | 61 | 0.20, |
|                               |   |    |         |    |    | 1.43) |
+-------------------------------+---+----+---------+----+----+-------+
| > Cancer of pancreas (157)    | 5 | 0. | (0.2    | 19 | 1. | (     |
|                               |   | 68 | 2,1.59) |    | 04 | 0.62, |
|                               |   |    |         |    |    | 1.62) |
+-------------------------------+---+----+---------+----+----+-------+
| Cancer of respiratory system  | 3 | 0. | (0.4    | 1  | 1. | (     |
| (160-163)                     | 2 | 59 | 0,0.83) | 44 | 03 | 0.87, |
|                               |   |    |         |    |    | 1.22) |
+-------------------------------+---+----+---------+----+----+-------+
| > Cancer of lung (162)        | 3 | 0. | (0.4    | 1  | 1. | (     |
|                               | 1 | 60 | 1,0.85) | 44 | 08 | 0.91, |
|                               |   |    |         |    |    | 1.28) |
+-------------------------------+---+----+---------+----+----+-------+
| Cancer of skin (172-173)      | 4 | 1. | (0.3    | 8  | 0. | (     |
|                               |   | 26 | 4,3.24) |    | 90 | 0.39, |
|                               |   |    |         |    |    | 1.77) |
+-------------------------------+---+----+---------+----+----+-------+
| Cancer of prostate (185)      | 9 | 1. | (0.5    | 9  | 0. | (     |
|                               |   | 27 | 8,2.41) |    | 64 | 0.29, |
|                               |   |    |         |    |    | 1.21) |
+-------------------------------+---+----+---------+----+----+-------+
| Cancer of bladder (188)       | 4 | 1. | (0.3    | 6  | 0. | (     |
|                               |   | 24 | 3,3.18) |    | 85 | 0.31, |
|                               |   |    |         |    |    | 1.85) |
+-------------------------------+---+----+---------+----+----+-------+
| Cancer of brain and other CNS | 6 | 1. | (0.4    | 5  | 0. | (     |
| (191-192)                     |   | 22 | 5,2.66) |    | 36 | 0.12, |
|                               |   |    |         |    |    | 0.84) |
+-------------------------------+---+----+---------+----+----+-------+
| Leukemia and aleukemia        | 6 | 1. | (0.4    | 19 | 1. | (     |
| (204-207)                     |   | 10 | 0,2.40) |    | 34 | 0.80, |
|                               |   |    |         |    |    | 2.09) |
+-------------------------------+---+----+---------+----+----+-------+
| Other lymphatic tissue (202,  | 6 | 1. | (0.4    | 12 | 1. | (     |
| 203, 208)                     |   | 34 | 9,2.93) |    | 05 | 0.54, |
|                               |   |    |         |    |    | 1.84) |
+-------------------------------+---+----+---------+----+----+-------+
| All lymphopoietic cancer      | 1 | 0. | (0.5    | 34 | 0. | (     |
| (200-209)                     | 4 | 98 | 4,1.64) |    | 90 | 0.62, |
|                               |   |    |         |    |    | 1.25) |
+-------------------------------+---+----+---------+----+----+-------+
| Benign neoplasms (210-239)    | 1 | 0. | (0.0    | 6  | 1. | (     |
|                               |   | 54 | 1,3.01) |    | 22 | 0.45, |
|                               |   |    |         |    |    | 2.66) |
+-------------------------------+---+----+---------+----+----+-------+
| All diseases of circulatory   | 1 | 0. | (0.5    | 6  | 0. | (     |
| system (390-458)              | 8 | 62 | 3,0.72) | 27 | 89 | 0.82, |
|                               | 0 |    |         |    |    | 0.97) |
+-------------------------------+---+----+---------+----+----+-------+
| All respiratory diseases      | 1 | 0. | (0.2    | 45 | 0. | (     |
| (460-519)                     | 5 | 42 | 3,0.69) |    | 55 | 0.40, |
|                               |   |    |         |    |    | 0.74) |
+-------------------------------+---+----+---------+----+----+-------+
| All diseases of digestive     | 1 | 0. | (0.2    | 50 | 0. | (     |
| system (520-577)              | 3 | 40 | 1,0.69) |    | 57 | 0.42, |
|                               |   |    |         |    |    | 0.75) |
+-------------------------------+---+----+---------+----+----+-------+
| > Cirrhosis of liver (571)    | 7 | 0. | (0.1    | 34 | 0. | (     |
|                               |   | 35 | 4,0.73) |    | 60 | 0.42, |
|                               |   |    |         |    |    | 0.84) |
+-------------------------------+---+----+---------+----+----+-------+
| All external causes of death  | 3 | 0. | (0.3    | 1  | 0. | (     |
| (800-998)                     | 2 | 45 | 0,0.63) | 97 | 90 | 0.78, |
|                               |   |    |         |    |    | 1.04) |
+-------------------------------+---+----+---------+----+----+-------+

<table style="width:100%;">
<colgroup>
<col style="width: 33%" />
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 6%" />
</colgroup>
<tbody>
<tr class="odd">
<td colspan="11"><h1
id="table-2.-trend-test-statistics-for-specific-types-of-cancer">Table
2. Trend Test Statistics for Specific Types of Cancer</h1></td>
</tr>
<tr class="even">
<td></td>
<td></td>
<td colspan="9"><strong>Observed and Expected<sup>1</sup> Deaths by Dose
Category in mSv (obs/exp)</strong></td>
</tr>
<tr class="odd">
<td><h1 id="cause-of-death-1">Cause of Death</h1></td>
<td><strong>TT<sup>2</sup></strong></td>
<td><strong>0</strong></td>
<td><strong>0-5</strong></td>
<td><strong>5-</strong></td>
<td><strong>10-</strong></td>
<td><strong>20-</strong></td>
<td><strong>40</strong>-</td>
<td><strong>80-</strong></td>
<td><strong>160-</strong></td>
<td><strong>320</strong></td>
</tr>
<tr class="even">
<td>Doses Lagged 10 Years</td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
<tr class="odd">
<td><blockquote>
<p>Esophagus</p>
</blockquote></td>
<td>0.92</td>
<td>3/2.06</td>
<td>2/1.18</td>
<td>0/0.43</td>
<td>0/0.32</td>
<td>0/0.30</td>
<td>0/0.28</td>
<td>0/0.29</td>
<td>0/0.13</td>
<td>0/0.01</td>
</tr>
<tr class="even">
<td><blockquote>
<p>Stomach</p>
</blockquote></td>
<td>0.35</td>
<td>2/1.89</td>
<td>4/4.83</td>
<td>2/1.68</td>
<td>3/1.36</td>
<td>0/1.33</td>
<td>2/1.26</td>
<td>1/1.03</td>
<td>0/0.60</td>
<td>0/0.03</td>
</tr>
<tr class="odd">
<td><blockquote>
<p>Colon</p>
</blockquote></td>
<td>0.09</td>
<td>7/6.14</td>
<td>15/13.8</td>
<td>5/4.79</td>
<td>6/3.29</td>
<td>1/3.36</td>
<td>1/3.55</td>
<td>2/3.32</td>
<td>3/1.68</td>
<td>0/0.10</td>
</tr>
<tr class="even">
<td><blockquote>
<p>Rectum</p>
</blockquote></td>
<td>0.60</td>
<td>3/1.26</td>
<td>1/1.89</td>
<td>0/0.61</td>
<td>0/0.54</td>
<td>2/0.52</td>
<td>0/0.57</td>
<td>0/0.50</td>
<td>0/0.10</td>
<td>0/0.01</td>
</tr>
<tr class="odd">
<td><blockquote>
<p>Pancreas</p>
</blockquote></td>
<td>0.16</td>
<td>5/4.98</td>
<td>7/8.87</td>
<td>5/2.42</td>
<td>3/2.03</td>
<td>0/2.20</td>
<td>1/1.96</td>
<td>3/1.66</td>
<td>1/0.84</td>
<td>0/0.04</td>
</tr>
<tr class="even">
<td><blockquote>
<p>Lung</p>
</blockquote></td>
<td>1.28</td>
<td>31/29.6</td>
<td>62/63.4</td>
<td>30/23.7</td>
<td>19/16.2</td>
<td>15/16.1</td>
<td>9/17.03</td>
<td>19/15.5</td>
<td>5/8.07</td>
<td>0/0.44</td>
</tr>
<tr class="odd">
<td><blockquote>
<p>Bone</p>
</blockquote></td>
<td>0.26</td>
<td>1/1.39</td>
<td>1/1.53</td>
<td>2/0.54</td>
<td>0/0.34</td>
<td>0/0.26</td>
<td>1/0.32</td>
<td>0/0.34</td>
<td>0/0.24</td>
<td>0/0.03</td>
</tr>
<tr class="even">
<td><blockquote>
<p>Prostate</p>
</blockquote></td>
<td>0.77</td>
<td>2/2.17</td>
<td>10/8.97</td>
<td>4/2.87</td>
<td>3/2.80</td>
<td>0/1.90</td>
<td>2/1.53</td>
<td>1/1.23</td>
<td>0/0.51</td>
<td>0/0.02</td>
</tr>
<tr class="odd">
<td><blockquote>
<p>Bladder</p>
</blockquote></td>
<td>0.00</td>
<td>2/2.22</td>
<td>5/4.56</td>
<td>1/1.73</td>
<td>0/1.23</td>
<td>2/0.75</td>
<td>1/0.73</td>
<td>1/0.53</td>
<td>0/0.22</td>
<td>0/0.03</td>
</tr>
<tr class="even">
<td><blockquote>
<p>Kidney</p>
</blockquote></td>
<td>0.01</td>
<td>1/0.96</td>
<td>1/2.38</td>
<td>1/0.78</td>
<td>0/0.50</td>
<td>2/0.44</td>
<td>1/0.39</td>
<td>0/0.36</td>
<td>0/0.19</td>
<td>0/0.01</td>
</tr>
<tr class="odd">
<td><blockquote>
<p>Non-Hodgkins lymphoma</p>
</blockquote></td>
<td>0.38</td>
<td>4/2.30</td>
<td>2/3.84</td>
<td>1/1.29</td>
<td>0/0.88</td>
<td>1/0.87</td>
<td>2/0.77</td>
<td>0/0.67</td>
<td>1/0.36</td>
<td>0/0.02</td>
</tr>
<tr class="even">
<td><blockquote>
<p>Multiple myeloma</p>
</blockquote></td>
<td>0.04</td>
<td>1/0.50</td>
<td>2/1.93</td>
<td>1/0.70</td>
<td>0/0.59</td>
<td>0/0.50</td>
<td>0/0.36</td>
<td>1/0.31</td>
<td>0/0.10</td>
<td>0/0.00</td>
</tr>
<tr class="odd">
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
<tr class="even">
<td>Doses Lagged 2 Years</td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
<tr class="odd">
<td><blockquote>
<p>Leukemia excluding CLL</p>
</blockquote></td>
<td>2.47</td>
<td>1/2.33</td>
<td>6/6.12</td>
<td>1/2.19</td>
<td>2/1.68</td>
<td>2/1.62</td>
<td>2/1.61</td>
<td>2/1.47</td>
<td>1/0.90</td>
<td>1/0.09</td>
</tr>
<tr class="even">
<td><blockquote>
<p>Leukemia excluding CCL, nonunderlying</p>
<p>cause included</p>
</blockquote></td>
<td>3.86</td>
<td>1/2.60</td>
<td>7/6.62</td>
<td>1/2.43</td>
<td>2/1.81</td>
<td>2/1.78</td>
<td>2/1.79</td>
<td>3/1.73</td>
<td>1/1.12</td>
<td>1/0.11</td>
</tr>
</tbody>
</table>

^1^Expected deaths calculated based on person-years distribution of age,
calendar year, and paycode of entire cohort such that observed =
expected.

^2^Trend test statistic calculated using average dose per cell,
stratified by 15 age groups, 8 time periods, and 2 paycodes. Maybe
compared to a Chi-square distribution with one degree of freedom (95^th^
percentile = 3.84; 90^th^ percentile = 2.71)

<table>
<colgroup>
<col style="width: 22%" />
<col style="width: 9%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 8%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 6%" />
</colgroup>
<tbody>
<tr class="odd">
<td colspan="11"><h1
id="table-3.-characteristics-of-recently-published-studies-of-occupationally-exposed-populations">Table
3. Characteristics of Recently Published Studies of
Occupationally-Exposed Populations</h1></td>
</tr>
<tr class="even">
<td></td>
<td><strong>1</strong></td>
<td><strong>2</strong></td>
<td><strong>3</strong></td>
<td><strong>4</strong></td>
<td><strong>5</strong></td>
<td><strong>6</strong></td>
<td><strong>7</strong></td>
<td><strong>8</strong></td>
<td><strong>9</strong></td>
<td><strong>10</strong></td>
</tr>
<tr class="odd">
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
<tr class="even">
<td>Number of study subjects</td>
<td>95,217</td>
<td>8,318</td>
<td>14,327</td>
<td>39,546</td>
<td>22,552</td>
<td>75,006</td>
<td>44,154</td>
<td>8,977</td>
<td>95,673</td>
<td>9,860</td>
</tr>
<tr class="odd">
<td>Population dose (Sv)</td>
<td>3,198</td>
<td>144</td>
<td>1,259</td>
<td>660</td>
<td>73</td>
<td>2,303</td>
<td>861</td>
<td>135</td>
<td>3,843</td>
<td>399</td>
</tr>
<tr class="even">
<td>Leukemia Dose-response?</td>
<td>Yes</td>
<td>No</td>
<td>Yes</td>
<td>No</td>
<td>No</td>
<td>Yes</td>
<td>No</td>
<td>Yes</td>
<td>Yes</td>
<td>Yes</td>
</tr>
<tr class="odd">
<td><p>Mean dose (mSv) for all workers/</p>
<p>radiation workers only</p></td>
<td><p>33.6/</p>
<p>71.9</p></td>
<td><p>17.3/</p>
<p>23.2</p></td>
<td><p>87.9/</p>
<p>124.0</p></td>
<td><p>16.7/</p>
<p>34.4</p></td>
<td><p>3.3/</p>
<p>7.8</p></td>
<td><p>30.7/</p>
<p>56.5</p></td>
<td><p>19.5/</p>
<p>23.3</p></td>
<td><p>15.0/</p>
<p>52.1</p></td>
<td><p>40.2/</p>
<p>45.4</p></td>
<td><p>40.5/</p>
<p>46.2</p></td>
</tr>
</tbody>
</table>

^1^ National Registry of Radiation workers (1992) ^6^ U.K. Nuclear
Industry (1994)

^2^ Oak Ridge National Laboratory (1991) ^7^ Hanford (1993)

^3^ Sellafield (1994) ^8^ Atomic Energy of Canada (1993)

^4^ U.K. Atomic energy Authority (1993) ^9^ International Combined
(1995)

^5^ Atomic Weapons Establishment (1988) ^10^Current Study

This report concerns work undertaken as part of the Health and Mortality
Study of U.S. Department of Energy workers conducted by the Oak
Institute for Science and Education, Oak Ridge, Tennessee, under
contract No. DE-AC05-76OR00033 between the U.S. Department of Energy and
the Oak Ridge Institute for Science and Education. This study was
completed with the oversight of the National Institute for Occupational
Safety and Health. The authors acknowledge the vital statistics offices
of the individual States as the source of death record data and
appreciate the offices' technical support of this research. The authors
are solely responsible for the data analyses and the interpretation of
the results.