Abstract 857: Evaluating the relationship between arsenic exposure and cancer risk in Canada
Authors: Pullella Katherine , Harris Shelley A. , McLaughlin John R. , Lubinski Jan , Narod Steven A. , Kotsopoulos Joanne 
Published: July 2021

Abstract
Background: Arsenic is an established carcinogen for cancers of the skin, bladder and lungs; it is also the most prevalent environmental toxin, resulting in all Canadians being exposed to some extent. In a recent prospective study of a low-exposure population, our team found that women in the highest quartile of circulating arsenic had a significant 13-fold increased risk of developing breast cancer, compared to the lowest quartile. This suggests that even at low-doses, arsenic may be an important risk factor for breast, and potentially other cancers not previously recognized. To date, the sources of arsenic in Canada, a low-exposure population, are unclear.
Objectives: To describe the status of arsenic exposure, identify the key predictors of arsenic status, and evaluate the relationship between arsenic exposure and cancer risk within the Canadian population.
Methods: Using data from Cycles 1-5 (2007-2017) of the Canadian Health Measures Survey (CHMS), exposure data (e.g., diet, water), demographic information, and urinary arsenic biomarkers will be analyzed. The CHMS is an ongoing, nationally representative survey, collecting objective health measures and food intake information from participants in biennial cycles. Data will be described using weighted percentages or means, and arsenic levels (total and speciated urinary arsenic metabolite concentrations) will be reported by percentile. Weighted multivariate regression models will be used to identify predictors of total urinary arsenic. Linkage to the Canadian Cancer Registry will be performed to ascertain incident cancers, and Cox proportional hazards regression used to estimate the relationship between arsenic status and cancer risk (total and site-specific).
Results: This analysis included 15,700 individuals, aged 18-80. The median total urinary arsenic level was 7.5 ug/g of creatinine. Significant predictors of total urinary arsenic levels were found to be weekly intake of fish and seafood (β= 0.3, 95%CI 0.27,0.33, P &lt; 0.001), grains (β=-0.02, 95%CI -0.02, -0.01, P&lt; 0.001) and consumption of well and/or cistern water (β = 0.13, 95%CI 0.04, 0.22, P=0.005). Linkage and data analysis are ongoing.
Impact: This work is the first to ascertain national exposure estimates to an environmental carcinogen. Fish, seafood, grains, and consumption of well and/or cistern water represent significant predictors of total urinary arsenic levels in Canada. Ultimately, this information is needed to develop critical population-level intervention strategies to reduce the Canadian, and global burden of cancer.
Citation Format: Katherine Pullella, Shelley A. Harris, John R. McLaughlin, Jan Lubinski, Steven A. Narod, Joanne Kotsopoulos. Evaluating the relationship between arsenic exposure and cancer risk in Canada [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 857.