Probabilistic Approach For Health Hazard Assessment of Trihalomethanes Through Successive Showering Events

Abstract

Trihalomethanes (THMs) are common disinfection byproducts in chlorinated tap waters. They can cause various cancers and non-cancerous health hazards. Ingestion, dermal contact, and inhalation are the three exposure routes considered in the THM hazard/risk assessments. Among these, inhalation hazard is generally calculated by assuming the initial concentration as zero. This assumption fails to address the case of continuous showers that can happen in shared showering facilities such as student hostels or gymnasiums. In the present study, the leftover THM concentration from the previous bath was considered to assess the chronic daily intakes (CDI) and hazard index (HI) of the successive showers. For this, tap water of a university campus was analyzed to understand the extend of THMs at consumer points and the result obtained was used for the hazard assessment. Total THM concentration varied from 0.51 to 68.9 µg L-1. To address the variability of the model input parameters, 50,000 iterations of Monte Carlo simulation were carried out. A maximum HI of 7.94E-02 ± 3.63E-02 and 6.69E-02 ± 3.08E-02 was observed for 1st shower for females and males. This value was found as exponentially increasing up to the 5th shower and thereafter the rate was decreasing. The methodology followed in the present study successfully determines the risk and hazard of THMs through successive showers.