Lifetime Cancer Risk from Drinking Water Exposure in Noncompliant Rural Systems in Northeast Tennessee: Preliminary Probabilistic Findings
Abstract
Small and rural drinking water systems in Northeast Tennessee often struggle to meet Safe Drinking Water Act (SDWA) requirements due to limited staffing, aging infrastructure, and complex monitoring requirements. Disinfection by-products (DBPs), particularly trihalomethanes (THMs), have been identified as primary contributors to health-based violations in some of these systems. THMs are formed when chlorine reacts with natural organic matter during drinking water disinfection and have been associated with increased cancer risk following long-term exposure. To better understand community-level health implications, a probabilistic quantitative risk assessment was conducted using Safe Drinking Water Information System (SDWIS) monitoring data from utilities in Northeast Tennessee to estimate lifetime cancer risk related to THM exposure. While the full analysis will include the multiple exposure pathways ingestion (drinking), inhalation (aerosols generated during showering and other household water use), and dermal contact (skin exposure), the present analysis presents preliminary results from the ingestion pathway only. Initial ingestion-based Monte Carlo simulations indicate that long-term THM exposure may result in lifetime excess cancer risks in the mid-10⁻⁵ range (mean risk: 3.72 × 10⁻⁵; 95% uncertainty interval: 2.32 × 10⁻⁵ to 5.43 × 10⁻⁵). These estimates exceed the 10⁻⁶ benchmark commonly used to define minimal risk but remain below the 10⁻⁴ level often considered unacceptable. Sensitivity analysis suggests that variation in THMs concentration contributes most to overall risk variability, followed by body weight and exposure duration. Risk estimates from the initial ingestion-based model are preliminary and potentially conservative, as total THMs were evaluated using the chloroform slope factor. These findings represent preliminary estimates based on currently available SDWIS data in Northeast Tennessee. Further refinement of model parameters and the addition of inhalation and dermal exposure pathways, multi-contaminant aggregation, spatial analysis, and demographic integration are planned to provide a more complete cumulative risk profile for affected populations.
Start Time
15-4-2026 9:00 AM
End Time
15-4-2026 12:00 PM
Room Number
Culp Ballroom 316
Poster Number
38
Presentation Type
Poster
Presentation Subtype
Posters - Competitive
Presentation Category
Health
Student Type
Graduate and Professional Degree Students, Residents, Fellows
Faculty Mentor
Md Rasheduzzaman
Lifetime Cancer Risk from Drinking Water Exposure in Noncompliant Rural Systems in Northeast Tennessee: Preliminary Probabilistic Findings
Culp Ballroom 316
Small and rural drinking water systems in Northeast Tennessee often struggle to meet Safe Drinking Water Act (SDWA) requirements due to limited staffing, aging infrastructure, and complex monitoring requirements. Disinfection by-products (DBPs), particularly trihalomethanes (THMs), have been identified as primary contributors to health-based violations in some of these systems. THMs are formed when chlorine reacts with natural organic matter during drinking water disinfection and have been associated with increased cancer risk following long-term exposure. To better understand community-level health implications, a probabilistic quantitative risk assessment was conducted using Safe Drinking Water Information System (SDWIS) monitoring data from utilities in Northeast Tennessee to estimate lifetime cancer risk related to THM exposure. While the full analysis will include the multiple exposure pathways ingestion (drinking), inhalation (aerosols generated during showering and other household water use), and dermal contact (skin exposure), the present analysis presents preliminary results from the ingestion pathway only. Initial ingestion-based Monte Carlo simulations indicate that long-term THM exposure may result in lifetime excess cancer risks in the mid-10⁻⁵ range (mean risk: 3.72 × 10⁻⁵; 95% uncertainty interval: 2.32 × 10⁻⁵ to 5.43 × 10⁻⁵). These estimates exceed the 10⁻⁶ benchmark commonly used to define minimal risk but remain below the 10⁻⁴ level often considered unacceptable. Sensitivity analysis suggests that variation in THMs concentration contributes most to overall risk variability, followed by body weight and exposure duration. Risk estimates from the initial ingestion-based model are preliminary and potentially conservative, as total THMs were evaluated using the chloroform slope factor. These findings represent preliminary estimates based on currently available SDWIS data in Northeast Tennessee. Further refinement of model parameters and the addition of inhalation and dermal exposure pathways, multi-contaminant aggregation, spatial analysis, and demographic integration are planned to provide a more complete cumulative risk profile for affected populations.
