Estimating Water Supply Arsenic Levels in the New England Bladder Cancer Study
Nuckols, John R., Freeman, Laura E. Beane, Lubin, Jay H., Airola, Matthew S., Baris, Dalsu, Ayotte, Joseph D., Taylor, Anne, Paulu, Chris, Karagas, Margaret R., Colt, Joanne, Ward, Mary H., Huang, An-Tsun, Bress, William, Cherala, Sai, Silverman, Debra T., Cantor, Kenneth P., Environmental Health Perspectives
BACKGROUND: Ingestion of inorganic arsenic in drinking water is recognized as a cause of bladder cancer when levels are relatively high ([greater than or equal to] 150 pg/L). The epidemiologic evidence is less clear at the low-to-moderate concentrations typically observed in the United States. Accurate retrospective exposure assessment over a long time period is a major challenge in conducting epidemiologic studies of environmental factors and diseases with long latency, such as cancer.
OBJECTIVE: We estimated arsenic concentrations in the water supplies of 2,611 participants in a population-based case--control study in northern New England.
METHODS: Estimates covered the lifetimes of most study participants and were based on a combination of arsenic measurements at the homes of the participants and statistical modeling of arsenic concentrations in the water supply of both past and current homes. We assigned a residential water supply arsenic concentration for 165,138 (95%) of the total 173,361 lifetime exposure years (EYs) and a workplace water supply arsenic level for 85,195 EYs (86% of reported occupational years).
RESULTS: Three methods accounted for 93% of the residential estimates of arsenic concentration: direct measurement of water samples (27%; median, 0.3 pg/L; range, 0.1-11.5), statistical models of water utility measurement data (49%; median, 0.4 pg/L; range, 0.3--3.3), and statistical models of arsenic concentrations in wells using aquifers in New England (17%; median, 1.6 pg/L; range, 0.6-22.4).
CONCLUSIONS: We used a different validation procedure for each of the three methods, and found our estimated levels to be comparable with available measured concentrations. This methodology allowed us to calculate potential drinking water exposure over long periods.
KEY WORDS: arsenic, environmental epidemiology, exposure assessment, geographic information systems, water quality modeling, water supply. Environ Health Perspect 119:1279-1285 (2011). http://dx.doi.org/10.1289/ehp.1002345 [Online 21 March 2011]
Ingesting inorganic arsenic in drinking water is recognized as a cause of bladder cancer [International Agency for Research on Cancer (IARC) 2004; Straif et al., 2009; Subcommittee on Arsenic in Drinking Water 1999; Subcommittee to Update the 1999 Arsenic in Drinking Water Report
2001 j. This conclusion is based largely on studies in populations where arsenic levels were relatively high (e.g., [greater than or equal to] 150 [micro]g/L). The epidemiologic evidence is less clear at the low-to-moderate concentrations typically observed in the United States (Baastrup et al. 2008; Bates et al. 1995, 2004; Cantor and Lubin 2007; Karagas et al. 2004; Mink et al. 2008; Steinmaus et al. 2003).
We conducted a population-based case-control study in northern New England [Maine (ME), New Hampshire (NH), Vermont (VT)] in the United States (Baris et al. 2009). Bladder cancer mortality and incidence rates have long been elevated in this region, and the primary objective of the study was to determine the reasons for this excess. Arsenic, found at moderately elevated levels (generally < 100 [micro]g/L) in water supplies in parts of New England, is among several hypotheses under investigation.
Estimating long-term exposure to arsenic in drinking water is a key study element that requires reconstructing residential water supply sources and arsenic concentrations over the lifetime of a person (Marshall et al. 2007). Although we recognize that other sources of arsenic (e.g., dietary intake) might impact cancer risk, this paper describes the methods used to estimate arsenic concentrations in the water supplies at residences and workplaces of the New England Bladder Cancer Study participants over their lifetime.
Materials and Methods
Details of the New England Bladder Cancer Study may be found elsewhere (Baris et al. 2009). In brief, we enrolled 1,193 persons who had been diagnosed with bladder cancer from 2001 through 2004 in ME, NH, or VT; 1,418 controls were randomly selected from state-specific Department of Motor Vehicles records (< 65 years of age) or from the
Centers for Medicare and Medicaid Services ([greater than or equal to] 65 years of age) and frequency matched to cases by state, sex, and age at diagnosis (within 5 years) (Baris et al. …