Margaret Karagas

Date: June 14, 2002

Investigating the Risks of Skin and Bladder Cancer at Environmental Levels of Arsenic Exposure in New Hampshire

Drinking water exposure to arsenic is clearly linked to cancer occurrence in highly exposed populations. However, the effects of environmental levels, typical of the USA are less clear. In particular, the health consequences of drinking water with 1 to 50 µg/L of arsenic remain controversial. Drinking water supplies throughout New Hampshire contain detectable levels of arsenic, and in four areas, several water systems exceed 50 µg/L. One of these "clusters" is located near a Superfund site.

We have detected arsenic primarily in private bedrock wells. Thus far, 35% of private wells in New Hampshire contain > 1 µg/L of arsenic and more than 10% contain >10 µg/L. Our ongoing epidemiologic investigation focuses on estimating the dose-response relationship between arsenic exposure and the risk of skin and bladder cancer in the New Hampshire population. Further, we are investigating whether specific subgroups of the population are greater risk of arsenic-induced malignancies due to co-carcinogen exposure, nutritional factors or genetic susceptibility. As part of our investigation, we are testing the reliability of various biological markers of arsenic exposure and are examining the molecular and genetic changes in lymphocytes and tumor tissues of individuals exposed to low levels of arsenic.

New Hampshire has a unique population-based surveillance system for non-melanoma skin cancers, and a rapid reporting cancer registry from which to identify incident bladder cancers. We measure arsenic concentrations both in toenail clippings and in household tap water samples, and urinary arsenic on a subset. An especially challenging aspect of the study involves estimating lifetime drinking water exposure to arsenic by identifying and testing subjects' previous residences with private water systems. A large sample size is needed to detect effects at low levels of exposure and to identify possible interactions. Therefore, our study will include approximately 800 cases of squamous cell carcinoma, 1,100 cases of basal cell carcinoma, 850 cases of bladder cancer and over 1,200 controls. A summary of recent results will be presented.