Oil Extraction in the Amazon Basin and Levels of Metals among Indigenous Populations

Abstract

Between May and August 2016 the Peruvian Ministry of Health conducted a cross-sectional study to assess levels of exposure to metals in the local population and stablish risk factors in Corrientes, Pastaza, Marañón and Tigre river basins (Peru). 1168 people from 39 indigenous communities participated in the study. Information on socio-demographic variables and environmental exposures was collected in questionnaires. Blood and urine samples were collected from each study participant, and environmental samples were collected from each community to measure levels of metals and hydrocarbons. We used atomic absorption spectrophotometry to measure metals concentrations (Pb, As, Ba, Cd and Hg) in biological and environmental samples. We used multilevel mixed-effects linear regression models with a random effect for community and river basin, adjusted for potential confounders to study the association between socio-demographic variables and environmental exposures and levels of metals in biological samples. We used linear regression models to study the association between median concentration of metals on environmental samples and on biological samples at the community level.57% of the study population had blood lead levels above 5 µg/dL and 28%, 13%, 9% and 26% of the study population had urinary levels of As, Ba, Cd and Hg, respectively, higher than those recommended by the Peruvian Ministry of Health (20 µg Cd/g As, 6 µg Ba/g creatinine, 2 µg Cd/g creatinine and 5 µg Hg/g creatinine). There were differences in levels of metals in environmental samples according to river basin. Inhabitants of communities with higher levels of Cd in agricultural soil presented higher levels Cd urinary levels than inhabitants from other communities. The analysis of risk factors at the individual level did not yield clear results. Differences in level of exposure to metals were generally explained by ethnic group, which might reflect geographical differences in levels of exposure.