BACKGROUND: In 1999, the Montgomery County Health Department (MCHD) discovered a groundwater plume from an unknown source when they sampled residential wells in Harleysville, Pennsylvania during their permit process. The Pennsylvania Department of Environmental Protection (PADEP) immediately provided bottled water to affected residences for drinking and cooking, and maintained carbon filtration systems at each affected residence. During the monitoring process, PADEP detected the following contaminants in the post-filtered water: 1,1-dichloroethane, 1,1-dichloroethene, 1,1,1-trichloroethane, and 1,4-dioxane. The site was referred to the Environmental Protection Agency for further investigation and was added to the National Priorities List in 2014. At the request of MCHD and PADEP, the Pennsylvania Department of Health (PADOH), under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR), evaluated environmental data on the post-filtered water samples to determine if the filtration systems effectively protect the health of the residents who use contaminated well water for showering and bathing.
METHODS: PADOH and ATSDR determined the exposure pathway during showering and bathing with contaminated water to be inhalation as dermal absorption of the chemicals of concern was determined to be very low. The inhalation exposure while showering and bathing was estimated by using a shower model. PADOH and ATSDR estimated cancer risks and non-cancer hazard quotients due to inhalation of 1,4-dioxane from showering based on the calculated inhalation exposure concentrations. Evaluation of contaminants other than 1,4-dioxane detected in the post-filtered water was not performed since they were either below the ATSDR health comparison values or near the PADEP residential groundwater medium-specific concentration.
RESULTS: The estimated inhalation exposure concentration of 1,4-dioxane was below the ATSDR health comparison values; therefore, non-cancer health effects are unlikely to occur and the estimated cancer risk, which ranged from 6x10-5 to 7x10-6, is considered low.
CONCLUSIONS: PADOH and ATSDR concluded that using the post-filtered water for showering and bathing is safe for adults and children and recommend that residents continue to use the supplied bottled water for drinking and cooking until a permanent remedy is in place. The main limitations in the analysis include incorporating multiple conservative assumptions, which may overestimate the calculated cancer risks.