Trace Element Exposures and Blood Pressure along the Interoceanic Highway, Madre de Dios, Peru

Abstract

Urbanization and economic development in lower and middle income nations (LMICs) have facilitated epidemiologic and nutritional transitions. Cardiovascular disease is the leading cause of death worldwide and prevalence of hypertension, a main risk factor, is projected to grow 80% by 2025 in LMICs. The completion of the Interoceanic Highway in 2011 in the Amazonian Department of Madre de Dios (MDD), Peru spurred rapid development, leading to population health concerns over environmental contamination due to gold mining. In addition to lifestyle exposures, elevated levels of lead, mercury, cadmium, and arsenic have been associated with hypertension in both animal studies and epidemiological analyses, although some population-based studies have failed to measure a statistically significant association. The essential element selenium potentially exerts a protective influence on hypertension. To gain insight into these potentially complex relationships, we analyzed joint arsenic, cadmium, mercury, lead, and selenium exposures in nails and systolic and diastolic blood pressure (SBP, DBP) of 389 adults in the Investigacion de Migracion, Ambiente, y Salud (IMAS) (Migration, Environment, and Health Study) conducted in MDD. Relationships were analyzed using linear mixed models with a household random intercept, and Bayesian kernel machine regressions (BKMR) to capture potential interactive and non-linear effects with trace elements. Visual inspection of the exposure-response surface estimated under BKMR, and estimation of parameters quantifying potential interaction, did not reveal evidence of interactive effects. In the linear mixed model, SBP was significantly associated with age (B=0.19, SE=0.06, p=.0025), female sex (B=-14.08, SE=4.2, p=.0011) and BMI (B=.48, SE=0.15, p=0017). Positive associations were observed between DBP and BMI (B=0.34, SE=0.10, p=.0010) and log mercury (ng/g) (B=1.08, SE=0.56, p=.0586). When stratified by sex there were additional suggested inverse associations between SPB and Western diet and selenium among men. The prevalence of artisanal gold mining and resultant mercury contamination in the region warrants further investigation.