Arsenic and disinfection by-products (DBPs) in drinking water in Canada

Abstract

OPS 25: Drinking water contamination and adult health, Room 411, Floor 4, August 26, 2019, 10:30 AM - 12:00 PM Introduction: People are exposed to Arsenic and DBPs (Trihalomethanes (THMs) and Haloacetic acids (HAAs) by drinking contaminated water. Arsenic is a naturally occurring element and known as a strong carcinogen. DBPs are formed by chlorination of water containing organic substances and considered possible human carcinogen. Water quality reports demonstrate the presence of high level of arsenic and DBPs in some areas of Newfoundland and Labrador (NL). However, there is no population level data on any association between the exposure to arsenic and DBPs and related cancer. Aim: To explore any association between Arsenic and DBPs present in drinking water and relevant cancers at the community level. Methods: High and low risk communities were identified based on water quality reports of provincial surveys. Cancer data were extracted from the NL Cancer Registry for cases diagnosed between 2007 and 2016. Certain disease information such as histology and topography and demographic information like sex, year of birth and residence at time of diagnosis were extracted. An ecological analysis was then conducted comparing cancer incidence rates between high risk and low risk communities. Results: Relative risk (RR) of arsenic induced cancers (a combination of renal cell, squamous cell of lung, skin, basal cell and Merkel cell of skin, adenocarcinoma of colon and bile ducts, hepatocellular and angiosarcoma of liver, cholangiocarcinoma, transitional cell carcinoma of urinary bladder) was 3.8 (95% CI, 1.09, 1.58). For DBPs, RR of THMs and HAAs induced cancer (a combination of urothelial cell carcinoma of urinary bladder, adenocarcinoma of rectum, colon and esophagus, malignant mesothelioma of lungs, and acute and chronic myeloid leukemia) was 2.1 (95% CI 0.67, 0.82). Discussion: Population level data showed that arsenic in drinking water was significantly associated in cancer incidences. However, despite the high relative risks, DBPs were not significantly associated with relevant cancer.