Toxic metals and urban oil and gas production in a Latina cohort in South Los Angeles, California

Background

Los Angeles County, California hosts the largest urban oil field in the nation, where wells operate near homes, schools, and parks. Oil drilling can expose nearby residents to pollutants, including toxic metals. Despite evidence linking oil and gas development to adverse health outcomes and elevated metal concentrations, few studies have used biological monitoring to assess exposure in urban settings.

Objective

This study examines how toxic metals cluster and which metals and clusters are associated with urban oil and gas production.

Methods

Using a community-engaged approach, we enrolled Latina women living in South Los Angeles as part of a larger study focused on women’s health. We collected toenail clippings as a biomarker of exposure to seven metals. We administered a survey to collect demographic, health, and dietary data. We used non-negative matrix factorization (NMF), a dimension reduction method, to examine how metals cluster and to identify source signatures. We conducted multivariable linear regression to examine the association between NMF factor and oil production volume during the year prior to toenail collection within 1 km of participants’ homes (no production, low production, high production), adjusting for age, smoking status, distance to highway, and neighborhood risk score for lead in housing and drinking water contaminants.

Results

Among 365 participants, NMF identified four clusters of metals. Factor 1 consisted primarily of arsenic, which may be linked to seafood consumption. The second factor included nickel and manganese, and elevated levels were associated with high oil production (beta = 0.36, 95% CI: 0.02, 0.69). Factor 3 consisted of cadmium and lead, which may be from household paint and dust. Factor 4 included lead, manganese, mercury, and antimony, potentially related to highway traffic.

Significance

This study demonstrates the utility of toenail biomarkers for monitoring metal mixtures and identifies a nickel and manganese factor associated with oil production.

Impact Statement

This study uses toenail biomarkers and mixture analysis to identify a metal cluster linked to oil and gas production in South Los Angeles, California. Findings reveal a nickel-manganese factor associated with high oil production, highlighting a potential exposure pathway in densely populated neighborhoods. The results underscore the importance of continued monitoring and research in urban oil fields to better understand potential exposure pathways and inform strategies that protect community health.