Associations between Environmental Exposures and Health Outcomes in Yuma County, Arizona

Abstract

We used community-engaged research principles to investigate environmental exposures and health outcomes in Yuma County, Arizona, focusing on perchlorate and metals contamination. Working with an underrepresented population, and addressing community-identified concerns, we outlined methods for community-engaged research. Using a case-control design, we enrolled 323 adult participants recruited by local organizations. We conducted health questionnaire interviews and collected data from analyses of urine samples, blood samples, hair samples, and electronic medical records. Urine samples were analyzed for perchlorate and creatinine, blood for thyroid hormones (TSH, free and total T4, free and total T3, and cortisol), and hair samples for cadmium, copper, mercury, manganese, lead, and uranium. Perchlorate was detected in all urine samples, and the average concentration of our sample was higher than the national average, although the estimated doses were below EPA reference values. Using logistic regression models, we found positive, though not statistically significant, associations between urinary perchlorate and thyroid disorders. Small discrepancies between self-reported data and medical records for thyroid conditions highlighted the importance of using multiple data sources in health assessments. Analysis of hair revealed measured concentrations exceeding estimated exposure thresholds for all tested metals. Farmworkers had higher hair concentrations of all metals except U, although differences were only significant for Pb (p = 0.007) and nearly for Mn (p = 0.076). We used classification and regression trees (CART) to identify demographic, environmental, or physiological factors that were associated with hair concentrations. The CART analysis indicated that most metal concentrations were most associated with recruitment site, weight/BMI, self-reported general health status, and some social determinants of health (e.g., birthplace, education level). Farmworking status and pesticide exposure were important factors for Hg, Mn, and U. Our findings underscore the need for continued environmental monitoring, further research into exposure pathways and related health effects, and targeted interventions to reduce exposures, particularly among susceptible populations. Overall, this study provides a foundation for addressing environmental health disparities and promoting community resilience in Yuma County and similar communities facing environmental pollution challenges.