P26-03 Application of MOE in Risk Assessment of Genotoxic Carcinogens Detected in Drinking Water

To comply with the England & Wales Water Supply (Water Quality) Regulations 2018, water companies must provide consumers with wholesome high quality drinking water that requires the assurance that chemicals and other harmful substances are not present at harmful concentrations. Controlling unintended exposures to chemicals in drinking water, some of which may be genotoxic and carcinogenic can be challenging. Water companies generally test for non-regulated chemicals after accidental spills or consumer complaints about taste or odour. In recent years, following such testing, water companies have enquired about potential health consequences through WRC's National Centre for Environmental Toxicology (NCET) Toxicology Advisory Service, commissioned by UKWIR Ltd. on behalf of the water suppliers of the UK and Ireland. In such an enquiry, NCET conducted risk assessment following the detection of benzo(a)pyrene; benzo(b)fluoranthene; benzo(k)fluoranthene and indeno(1,2,3-c, d)pyrene; at concentrations of <0.010, <0.020, <0.020 and <0.010 µg/L respectively in drinking water samples collected from a consumers tap. In 2008 evaluations conducted by the European Food Safety Authority (EFSA) concluded that benzo(a)pyrene, benzo(b) fluoranthene; benzo(k)fluoranthene, and indeno(1,2,3-c, d)pyrene were genotoxic carcinogens. Following recommendations from EFSA, a Margin of Exposure (MOE) approach was used by NCET to conduct our risk assessment. EFSA and other competent authorities have recommended the use of MOE for the consideration of safety concerns by risk managers dealing with substances that are both genotoxic and carcinogenic or substances that have limited toxicity data and for which no health-based guidance value (HBGV) may be available. In general, an MOE of 10,000 or higher can be interpreted as being of low concern. Based on the concentrations detected in the drinking water samples, NCET calculated MOEs of 1030303, 507463, 507463, and 1030303 for benzo(a)pyrene, benzo(b) fluoranthene, benzo(k)fluoranthene, and indeno(1,2,3-c, d)pyrene, respectively. NCET concluded that the short-term exposures to these chemicals were unlikely to pose a short-term health risk at the concentrations detected, however, the potential for adverse health effects from long-term exposures cannot be excluded. The water company in this case was advised to reduce or control exposure levels to As Low As Reasonably Practicable to ensure that the long term health risks associated with long-term exposures to the genotoxic carcinogens such as those detected were minimised.