CONAMAD: Birth cohort to quantify the effects of in-utero metals exposure on child development in an artisanal and small-scale gold mining region of the Amazon

Abstract

Research quantifying in-utero trace metals exposure and health effects have been conducted primarily in developed regions. Given the global increase of artisanal scale gold mining (ASGM), there is a critical need to quantify in-utero exposure to trace metals and related health risks in populations living in ASGM environments, characterized by high prevalence of malnutrition, infectious disease, and poverty. We describe the design and initial results of CONAMAD, a birth cohort of multiparous women (18 and over) living in an ASGM region of Madre de Dios (MDD), Peru, whose long-term goal is to quantify in-utero toxic metals exposures and subsequent child health effects during the first two years of life. 270 mothers were enrolled during pregnancy across four zones representing differential economic and development activities in MDD. At enrollment, women averaged 28 years of age, 20 weeks gestational age, and 17% were of short stature (<1.45m). Half of all mothers lived near a major road and ~20% lived near mining or a gold shop, which varied by location (p<0.001). We obtained biomarkers from 215 mothers and their newborns at birth, including maternal and cord blood, hair samples, and placenta for exposure assessment. The median levels of mercury and lead in cord blood were 5.8 μg/L and 10.0 μg/L, respectively, while median levels in maternal blood were 3.4 μg/L and 13.3 μg/L, respectively (USEPA BMDL is 5.8 μg/L for blood Hg, 5 μg/dL for lead). USEPA assumes cord:maternal blood mercury ratio (Hgc:Hgm) to be equal when estimating reference doses for risk quantification; however, we find higher median Hgc:Hgm of 1.67 (10th to 90th percentile: 1.13-2.42) with 93% of cord blood Hg samples exceeding maternal blood levels. Results indicate that the developing fetus may have increased health risks if standard public health recommendations are followed by pregnant women in ASGM regions.