Abstract
While epidemiologic studies clearly demonstrate drinking water with high levels of arsenic as a significant risk factor for lung cancer, the evidence at low levels (≤50 μg/L) is uncertain. Therefore, we have conducted an ecological analysis of recent lung cancer incidence for US counties with a groundwater supply of <50 μg/L, the historical limit for both the EPA and WHO. Data sources used included USGS for arsenic exposure, NCI for lung cancer outcome, and CDC and US Census Bureau forcovariates. Poisson log-linear models were conducted for male, female, and total populations using for exposure median county arsenic level, maximum arsenic level ≤50 μg/L, and ≥80% population groundwater dependency. Statistically significant negative associations were found in each of the six models in which the exposure was limited to those who had major exposure (≥80% dependency) to low-levels of arsenic (≤50 μg/L). This is the first large ecological study of lung cancer risk from drinking water arsenic levels that specifically examined the dose-response slope for populations whose exposure was below the historical limit of ≤50 μg/L. The models for each of the three populations (total; male; female) demonstrated an association that is both negative and statistically significant.
Highlights
Arsenic levels naturally found in groundwater range from μg/L to mg/L throughout the world.Major epidemiological studies from areas with very high arsenic exposures measured in hundreds of μg/L to a few mg/L, in Taiwan, Southeast Asia, and South America, have been conducted and have demonstrated increased cancer risk at exposure levels of 300–2000 μg/L
This study uses two US governmental datasets in the public domain to assess the dose-response relationship between lung cancer incidence and arsenic levels of groundwater wells used as drinking water, using data aggregated at the county level
Our analysis demonstrates the observation that was predicted by the Lamm meta-regression, which is that the dose-response relationship for lung cancer incidence at low arsenic exposure is statistically significantly negative [26]
Summary
Major epidemiological studies from areas with very high arsenic exposures measured in hundreds of μg/L to a few mg/L, in Taiwan, Southeast Asia, and South America, have been conducted and have demonstrated increased cancer risk at exposure levels of 300–2000 μg/L. The first showing for lung cancer excess was from the Blackfoot-Disease endemic area of Southwest Taiwan [1,2] with increased risk for the villages with median exposures between 300 μg/L and 600 μg/L and still higher for those with median exposures above 600 μg/L. Studies from Chile showed that their increased risk was among those with arsenic exposures of 800 μg/L or greater [3]. Some studies purportedly showed an increase at exposures in the 100–300 μg/L range [4,5]. Some studies reported a positive relationship [6,7], some no relationship [8], and some a negative relationship [9]
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