Risk Assessment for Livestock in the Oriente Region of Ecuador

Abstract

Abstract Potential risks to livestock may occur if they are exposed to releases of petroleum hydrocarbons at or near oil production facilities. In 2004, the American Petroleum Institute (API) published Risk Based Screening Levels for the Protection of Livestock Exposed to Petroleum Hydrocarbons [1]. The API framework, conceptual site model, and screening-level procedures were used in a case study to evaluate potential risks to livestock at the oilfield sites in northeastern Ecuador. API's toxicity reference values (TRVs) as well as their drinking water and soil risk-based screening levels (RBSLs) for livestock were used to evaluate whether levels of hydrocarbons in soil and water could pose a health risk to cattle, calves, sheep, goats, or horses. RBSLs are threshold concentrations in site media (e.g. soil, water, and air) below which no significant unacceptable risks to livestock are expected. Since pigs, chickens, and ducks are also commonly raised in northeastern Ecuador, new TRVs were calculated for them based on a review of all published toxicity values. RBSLs for pigs, chickens, and ducks were then calculated using exposure assumptions aligned with API's conceptual site model. The evaluation presented herein was a screening-level risk assessment using a conservative approach to evaluate potential risks to livestock from exposure to petroleum at the oilfield sites. The RBSLs and TRVs were conservative because they are based on non-lethal endpoints protective of individual livestock, and the mammalian RBSLs for TPH were based on fresh crude oil rather than on the weathered, less toxic oil that is typically found in soils in tropical climates. In this case study, data from over 300 surface soil and 100 surface water samples from seven oilfields in northeastern Ecuador were collected during field inspections conducted from 2004 through 2006. Potential hydrocarbons of concern included: crude oil or total petroleum hydrocarbons (TPH); benzene, toluene, ethylbenzene, and xylene (BTEX); and polycyclic aromatic hydrocarbons (PAHs).