Lifetime excess cancer risk due to carcinogens in food and beverages: Urban versus rural differences in Canada.

OBJECTIVES: To explore differences in urban versus rural lifetime excess risk of cancer from five specific contaminants found in food and beverages. METHODS: Probable contaminant intake is estimated using Monte Carlo simulations of contaminant concentrations in combination with dietary patterns. Contaminant concentrations for arsenic, benzene, lead, polychlorinated biphenyls (PCBs) and tetrachloroethylene (PERC) were derived from government dietary studies. The dietary patterns of 34 944 Canadians from 10 provinces were available from Health Canada's Canadian Community Health Survey, Cycle 2.2, Nutrition (2004). Associated lifetime excess cancer risk (LECR) was subsequently calculated from the results of the simulations. RESULTS: In the calculation of LECR from food and beverages for the five selected substances, two (lead and PERC) were shown to have excess risk below 10 per million; whereas for the remaining three (arsenic, benzene and PCBs), it was shown that at least 50% of the population were above 10 per million excess cancers. Arsenic residues, ingested via rice and rice cereal, registered the greatest disparity between urban and rural intake, with LECR per million levels well above 1000 per million at the upper bound. The majority of PCBs ingestion comes from meat, with values slightly higher for urban populations and LECR per million estimates between 50 and 400. Drinking water is the primary contributor of benzene intake in both urban and rural populations, with LECR per million estimates of 35 extra cancers in the top 1% of sampled population. CONCLUSION: Overall, there are few disparities between urban and rural lifetime excess cancer risk from contaminants found in food and beverages. Estimates could be improved with more complete Canadian dietary intake and concentration data in support of detailed exposure assessments in estimating LECR.

Risk-based indicators of Canadians' exposures to environmental carcinogens.

BACKGROUND: Tools for estimating population exposures to environmental carcinogens are required to support evidence-based policies to reduce chronic exposures and associated cancers. Our objective was to develop indicators of population exposure to selected environmental carcinogens that can be easily updated over time, and allow comparisons and prioritization between different carcinogens and exposure pathways. METHODS: We employed a risk assessment-based approach to produce screening-level estimates of lifetime excess cancer risk for selected substances listed as known carcinogens by the International Agency for Research on Cancer. Estimates of lifetime average daily intake were calculated using population characteristics combined with concentrations (circa 2006) in outdoor air, indoor air, dust, drinking water, and food and beverages from existing monitoring databases or comprehensive literature reviews. Intake estimates were then multiplied by cancer potency factors from Health Canada, the United States Environmental Protection Agency, and the California Office of Environmental Health Hazard Assessment to estimate lifetime excess cancer risks associated with each substance and exposure pathway. Lifetime excess cancer risks in excess of 1 per million people are identified as potential priorities for further attention. RESULTS: Based on data representing average conditions circa 2006, a total of 18 carcinogen-exposure pathways had potential lifetime excess cancer risks greater than 1 per million, based on varying data quality. Carcinogens with moderate to high data quality and lifetime excess cancer risk greater than 1 per million included benzene, 1,3-butadiene and radon in outdoor air; benzene and radon in indoor air; and arsenic and hexavalent chromium in drinking water. Important data gaps were identified for asbestos, hexavalent chromium and diesel exhaust in outdoor and indoor air, while little data were available to assess risk for substances in dust, food and beverages. CONCLUSIONS: The ability to track changes in potential population exposures to environmental carcinogens over time, as well as to compare between different substances and exposure pathways, is necessary to support comprehensive, evidence-based prevention policy. We used estimates of lifetime excess cancer risk as indicators that, although based on a number of simplifying assumptions, help to identify important data gaps and prioritize more detailed data collection and exposure assessment needs.