Exposures and Health Risks of the Diné Communities Impacted by the Gold King Mine Spill

Abstract

On August 5th, 2015, an abandoned gold mine near Silverton, CO was accidentally disturbed, resulting in 3 million gallons of acid mine drainage containing arsenic and lead being released from the Gold King Mine, eventually reaching the San Juan River. The Diné (Navajo) people have a deep spiritual connection to the natural environment and rely heavily on the San Juan River for agricultural, spiritual and cultural practices. The initial risk assessment conducted by the U.S. EPA only considered a recreational scenario (i.e., a hiker drinking from the river) and concluded that there would be no adverse effects from exposure. This U.S. EPA risk assessment did not take into account the cultural, residential or dietary pathways of the Diné. While the environmental impacts of the Gold King Mine Spill (GKMS) have been investigated by various governmental agencies, the Diné-specific impacts as a result of the GKMS are unknown. Understanding the community-specific impacts of the GKMS is necessary to develop effective recovery programs. Through the Gold King Mine Spill Diné Exposure project, twelve focus groups were held on the Navajo Nation to identify interactions between the Diné and the San Jun River. A total of 43 unique activities were identified and grouped into one of five distinct categories: livelihood, recreational, cultural and spiritual, dietary, and arts and crafts activities. Within one year of the GKMS, Navajo Nation Community Health Representatives administered the questionnaire to adults living on the Navajo Nation in communities along the San Juan River. A total of 63 adults and 27 children were recruited for participation in this study. On average there was a 56.2% decrease in the number of activities that participants engaged in with the San Juan River following the GKMS. The GKMS was a traumatic event for the Diné, which may lead to long-term mental health effects. Additionally, the significant reduction in all activity categories following the GKMS indicates that Diné adults may refrain from passing down their teachings, which may negatively impact future generations to come. We conducted a community-based probabilistic risk assessment from exposure to arsenic and lead at three different time points (i.e., pre-, peak-, and post-GKMS) for three exposure pathways: 1) recreational, 2) cultural, and 3) dietary, that were potentially impacted by the GKMS. These three pathways are referred to here as “San Juan River pathways” (i.e., certain recreational, cultural, and dietary pathways). Utilizing the Lifeline Community Based Assessment Software (CBAS), we incorporated distributions for different exposure factors (e.g., hand-to-mouth contacts, transfer efficiency) along with Diné-specific activities (e.g., putting Chii (red earth found near rivers) on face for prayers) to simulate a dose estimate. The estimated hazard quotients (HQs) from the arsenic and lead dose estimates were less than one for all time points and for the three exposure pathways potentially impacted by the GKMS (i.e., San Juan River recreational, San Juan River cultural, and San Juan River dietary pathways), indicating no excess non-cancer risk. In addition to the pathways potentially impacted by the GKMS, we integrated exposure pathways that were thought not to be impacted by the GKMS referred to here as “non-San Juan River pathways” (i.e., certain recreational, cultural, dietary, and residential pathways) to estimate the potential aggregate non-cancer and cancer risk from exposure to arsenic and lead. The dietary pathway unaffected by the GKMS (i.e., consumption of food and water) was the main contributor to arsenic and lead. For arsenic, approximately 58% of the scenarios exceeded an HQ of one via the non-San Juan River dietary pathway, and 85% were above the 1 x 10-04 acceptable cancer risk guideline. The added dose from exposure through pathways impacted by the GKMS was relatively low and does not significantly contribute to overall non-cancer or cancer risk estimates. As dose estimates vary by orders of magnitude between the recreational, cultural, and dietary pathways, it is still important to consider them in the risk assessment process. To ensure community concerns stemming from the Gold King Mine Spill disaster are addressed, continued dissemination of results in a culturally-appropriate manner, collaboration with governmental agencies, and community partnerships are key. This risk assessment provides the first documentation of incorporating unique exposure pathways of the Diné people and raises the need to incorporate community-specific pathways during the risk analysis process.