Human Health Risk Assessment of Exposure to Emerging Contaminants (Pharmaceuticals and Personal Care Products) in Drinking Water Supply in Non-Sewered Communities

Pharmaceuticals and personal care products (PPCPs) are continuously released into the environment following regular household use. With the improvement in analytical techniques, research addressing the occurrence, fate and effects of these compounds in various environmental media has increased over the last two decades. There is however, a significant knowledge gap regarding environmental exposure to PPCPs for different regions particularly low-to-middle income countries and emissions from sources other than wastewater treatment plants (WWTPs), such as Onsite wastewater treatment systems (OWTSs). A cross-sectional survey of 350 households in southern Nigeria was used as a proxy to estimate the annual household use of personal care products (PCPs) and the mass of active pharmaceutical ingredients (APIs) consumed per capita per year by applying the WHO Defined Daily Dose concept. A risk-based prioritization scheme was developed to pre-select PPCPs with the greatest potential to enter groundwater from septic systems using the risk index (RI) approach. The developed priority list of PPCPs indicates that 14 APIs and 9 PCP active ingredients have RI ≥ 0.01 and are therefore considered high priority compounds for future groundwater monitoring protocols in southern Nigeria. A comprehensive monitoring protocol was developed to characterize the occurrence and concentrations of dichlorvos (a household pesticide) and 61 APIs in domestic water wells impacted by septic systems in southern Nigeria. All sampled wells (53) had detected levels of at least 2 APIs and the six most frequently detected (>50%) APIs included paracetamol, sulfamethoxazole, trimethoprim, carbamazepine, naproxen and caffeine. Dichlorvos was detected in 12 out of 20 sampled wells. Finally, the risk of potential adverse effects from indirect exposure to APIs in drinking water was assessed by benchmarking exposure with the derived acceptable daily exposure (ADE) limits for individual APIs. Hazard quotient (HQ) was less than 1 for all APIs, which suggests that exposure to maximum levels of individual APIs in Nigerian groundwater currently do not pose an appreciable risk to human health. However, long term exposure to trace levels of chemical mixtures in drinking water may result in a relatively greater risk than that posed by individual substances due to potential for cocktail effects and underscores the need for further investigation.