Metal exposure and obesity in Chile: a cross-sectional analysis of the National Health Survey 2017

Background and Objective: Chile is a low-middle-income mining country with an epidemiological transition. The prevalence of overweight/obesity reached 78%, and a small area analysis revealed a heterogeneous geographic distribution. These finding leads us to consider the population exposed to metals and their role in developing the disease. Methods: From National Health Survey 2017 (NHS-2017), we characterized metal concentrations as measured in spot urine (arsenic, cadmium, and mercury) and blood (lead) samples in 15 administrative regions of Chile. The criterium for the detection of metals used by the NSH-17 was a minimum quantification of 5 µgL for arsenic, 1 µg/dL lead,1 µgL cadmium, and 2 µgL for mercury. We defined metal exposure according to its 50th percentile distributions over the minimum value recordable. Obesity was a body mass index >30 kg/m2. Analyses accounted for the complex sampling design; obesity association was estimated through quasi-binomial models. We report prevalences (%), Odds ratios (OR) with 95% Confidence Intervals. Results: Of 6233 subjects, 3847 (61.7%) had blood/urine samples. Four regions had the highest prevalences of exposure to any of the metals analyzed: Arica (63%, 52-74%) and Atacama (53%, 45-61%) from the north zones; Bio Bio (60%, 49-70%) from the central, and Magallanes (57%, 49-65%) from the south zone. Only a northern region of Chile had the highest prevalence of multiexposure to metals (Tarapacá 25%, 14-35%). OR for lead and obesity was 3.6 (1.18-11.12) in the Valparaíso region and 1.99 (1.04-3.83) in the Tarapacá region. Arsenic was associated with obesity in the Bio Bio (2.41, 1.11-594) and the Maule regions (2.51, 1.03-6.11). Conclusions: This study reveals high-risk areas exposed to metal toxicity in Chile, with different patterns along the territory. This study also explores the external exposome theory in obesity origin, specifically in metal toxicity exposure, proposing the trade-off from curing to preventing obesity.