1.What is the purpose of the study?
The purpose of the study was to determine whether potential exposures to the drinking water contaminants at Camp Lejeune are associated with increased risk of death from specific cancers and other chronic diseases among civilian workers employed at the base. The contaminants included trichloroethylene (TCE), tetrachloroethlylene (also known as perchloroethylene or PCE), benzene, and two contaminants formed when TCE or PCE degrade in groundwater: 1,2-dichloroethylene and vinyl chloride.
2. What was studied?
The study evaluated specific causes of death in 4,647 full-time workers who were employed at Camp Lejeune during 1973-1985. ATSDR also evaluated a comparison group of 4,690 full-time workers who were employed at Camp Pendleton during 1973-1985 and were not employed at Camp Lejeune during those years. The Camp Pendleton workers are a comparison group; that is, they were not exposed to contaminated drinking water.
Cause of death data from 1979-2008 were used to study the workers at Camp Lejeune and Camp Pendleton. Information on causes of death was obtained from the National Death Index (NDI) of the National Center for Health Statistics. The study included all underlying causes of death that other studies have shown to be associated with one or more of the chemicals found in the drinking water at Camp Lejeune. Causes of death were selected based on literature reviews conducted by the U.S. Environmental Protection Agency(EPA), the National Toxicology Program (NTP), the International Agency for Research on Cancer (IARC), and Agency for Toxic Substance and Disease Registry (ATSDR).
The study looked at data for these causes of death:
- Amyotrophic lateral sclerosis (ALS)
- Cancers of the bladder, brain, cervix, colon, esophagus, female breast, kidney, larynx, liver, lung, oral cavity, pancreas, prostate, rectum, and soft tissue
- Hematopoietic cancers
- Hodgkin’s Lymphoma
- Multiple myeloma
- Non-Hodgkin’s lymphoma
- Non-cancerous kidney diseases
- Non-cancerous liver diseases
- Multiple sclerosis
- Parkinson’s disease
Also included in the study were three causes of death known to be caused by cigarette smoking but not known to be associated with the drinking water contaminants: cardiovascular disease, chronic obstructive pulmonary disease (COPD), and stomach cancer. These causes of death were included to assess the possible impact of smoking on the findings because information on smoking status was not available for study subjects.
3. Why does this study include only workers employed at Camp Lejeune and Camp Pendleton during 1973-1985?
The timeframe includes the period when exposure occurred and for which data are available. The period ended with the closure of the most heavily contaminated wells. Specifically, the study evaluates civilian workers at Camp Lejeune and Camp Pendleton who were employed at either base any time between the second quarter of 1973 and the end of 1985. Continuous quarterly information on DOD employment from the Defense Manpower Data Center began with the second quarter of 1973. The most heavily contaminated wells at Camp Lejeune were shut down in 1985.
4. Why was Camp Pendleton used for the comparison group?
To determine whether mortality rates were higher for Camp Lejeune civilian workers, ATSDR wanted to compare their mortality rates with those of an appropriate comparison population. The Camp Lejeune civilian worker mortality rates could have been compared with the general U.S. population. However, worker populations usually have lower mortality rates than the general U.S. population because of the “healthy worker effect.” That is, healthy individuals are more likely to be employed and remain employed, while the general U.S. population includes people who are not healthy enough to be employed. To avoid the problem of the healthy worker effect, an appropriate comparison population for a worker cohort is another worker cohort. Camp Pendleton civilian workers have similar occupations as the Camp Lejeune civilian workers, but they were not known to be exposed to contaminated drinking water.
5. Why did ATSDR include smoking-related conditions?
The study included three causes of death known to be caused by cigarette smoking but not known to be associated with exposure to volatile organic compounds: stomach cancer, cardiovascular disease, and chronic obstructive pulmonary disease (COPD). These causes of death were included to assess the possible impact of smoking on the findings. No information was available on smoking status of the study subjects.
6. What did you find?
During 1979-2008, there were 654 deaths in the Camp Lejeune group of civilian workers and 869 deaths in the Camp Pendleton group. The median ages in 2008 for the Camp Lejeune and Camp Pendleton cohorts were 58 years and 60 years, respectively.
Compared with the Camp Pendleton workers, the Camp Lejeune workers had higher mortality rates for the following causes of death:
- Cancers of the female breast, kidney, lung, oral cavity, prostate, and rectum
- Kidney diseases
- Multiple myeloma
- Parkinson’s disease
The higher rates of cancers of the kidney, prostate and rectum, leukemias, and Parkinson’s disease were mainly among the Camp Lejeune civilian workers with higher cumulative exposures to the contaminants.
When civilian workers with higher exposures at Camp Lejeune were compared to Camp Lejeune workers with lower exposures, higher cumulative exposures to the contaminants were associated with increased risks for cancers of the kidney, esophagus, prostate, and rectum, leukemias, and Parkinson’s disease.
The findings for the smoking-related causes of death, such as stomach cancer, cardiovascular disease, and chronic obstructive pulmonary disease suggested that smoking would only slightly increase the risk of any association between cause of death and exposure to the drinking water contaminants at Camp Lejeune.
7. Does this study provide evidence of causation?
This study makes an important contribution to the scientific literature by providing additional information about the health effects of exposure to volatile organic compounds in drinking water. It does not, however, provide definitive evidence that exposure to the contaminants caused any specific health outcome because of the following limitations:
Small numbers of specific causes of death; the resulting wide confidence intervals indicate considerable uncertainty about the actual risk (it could be higher or lower).
Short exposure durations likely reduced the magnitude of the effects.
- Uncertainty about the drinking water use of civilian workers at Camp Lejeune.
- Uncertainty about workplace locations (e.g., during the workday, aworker may have been assigned to multiple locations at the base).
- Disease misclassification bias (a worker may have been misdiagnosed with a disease or may have had a disease that was not diagnosed).
- Lack of information on other exposures or risk factors.
8. Why is ATSDR doing these studies?
People who lived or worked at Camp Lejeune have been concerned about their health since learning that the drinking water was contaminated. Each study ATSDR conducts helps us understand more about the health effects of exposure to the contaminated water at Camp Lejeune. These studies also add to the growing body of scientific information that is available about the health effects of drinking water contaminated with volatile organic compounds and could help us better understand future exposures.