A Community-Based Health Risk Assessment Following the Gold King Mine Spill: Results from the Gold King Mine Spill Diné Exposure Project

Abstract

The Gold King Mine Spill (GKMS) disaster resulted in three million gallons of acid mine drainage-containing arsenic and lead being released into a tributary of the San Juan River. The San Juan River flows through the Navajo Nation and the Diné (Navajo) rely on this river for a variety of purposes lending to unique exposure pathways. We administered questionnaires in three Navajo communities in collaboration with the Navajo Nation Community Health Representatives to obtain frequency and duration data on 43 activities (e.g., praying with river water, fishing from the river). These activities were utilized to conduct a community-based probabilistic risk assessment from exposure to arsenic (As) and lead at three different time points (i.e., pre-GKMS, peak-GKMS, and post-GKMS) for four different exposure scenarios: (1) recreational, (2) cultural, (3) dietary, and (4) aggregate. The aggregate scenario combines exposure from engaging in recreational, cultural, and dietary related activities. Utilizing the Lifeline Community-Based Assessment Software ™ distributions were incorporated for different exposure factors (e.g., hand-to-mouth contacts, transfer efficiency) along with Diné-specific activities (e.g., using the sediment as sunscreen) to estimate dose. The estimated lead and arsenic (As) hazard quotients (HQs) for the recreational, cultural, and dietary scenario for all time points were less than one, indicating no excess non-cancer risks. Only the dietary scenario resulted in an excess cancer risk, with less than 1% of the simulated estimates exceeding the 1 × 10–04 cancer risk guideline from exposure to arsenic through the dietary scenario (e.g., consuming fish from the San Juan River) at all time points. This risk assessment is the first to incorporate the unique exposure pathways of the Diné people following the GKMS and highlights the need to incorporate community-specific pathways during the risk analysis process.