Exposição pré-natal aos metais potencialmente tóxicos, determinantes sociais e crescimento fetal no Recôncavo Baiano, Brasil.

Abstract

Introduction: During pregnancy and childhood, children are more vulnerable to the toxicity of potentially toxic metals (PTM). Social conditions influence exposure to MPTs, and impact child development; for example, neurodevelopment (ND) and fetal growth (FG). Considering this social aspect of environmental pollution, a growing body of literature recommends a multidimensional and integrated perspective to investigate the toxicity of pollutants such as MPTs. It also encourages further research in low- and middle-income countries (LMICs). Objectives – For the three independent studies: Paper 1) Present a conceptual model that allows integrating the social and biological characteristics of children during pregnancy and childhood to explain the neurotoxicity of MPTs better; Paper 2) Investigate the exposure to MPTs of pregnant women recruited from the DSAN cohort and the factors associated with such exposures; Paper 3) to investigate the association between exposure to each metal and the birth weight of children, in addition to investigating possible combined effects of these metals on birth weight. Methods: Paper 1) From the perspective of Bronfenbrenner's Bioecological Model (BBM) extended to the physical world, a conceptual model was developed to integrate social and biological characteristics in the study of the neurotoxicity of MPTs; Paper 2) Sociodemographic data and general habits were collected through questionnaires applied to 163 pregnant women in the municipalities of Aratuípe and Nazaré das Farinhas, recruited by the DSAN-12M cohort. We investigated the determinants of exposure to lead (Pb), cadmium (Cd), arsenic (As), and manganese (Mn). We measured levels of these metals in the blood (PbS and CdS), hair (AsC and MnC), toenails (MnUp), and Pb Dust Loading Rate (RtPb) in their homes by graphite furnace atomic absorption spectrophotometry (GFAAS). Paper 3) We investigated the relationship between maternal exposure to lead (Pb), cadmium (Cd), manganese (Mn), and birthweight (BW) of 74 newborns. Blood was collected during the second trimester of pregnancy to determine Pb (PbS) and Cd (CdS) levels, while hair (MnC) and toenails (MnUp) were used for Mn. The samples were analyzed by graphite furnace atomic absorption spectrophotometry (GFAAS). Sociodemographic data, gestational age (GA), and BW were collected from questionnaires and maternity records. Results Paper 1) The concept of BBM, which structures the social context into four levels (micro, meso, exo and macrosystem) which influence development through the gene-social relationship, was extended to the physical environment, where PTMs operate. Considering the biological plausibility of gene-environment interactions (social and physical), we present how biological and social factors can jointly influence child neurodevelopment with PTMs. Paper 2) Cd presented a worrying situation, with up to 61.1% (95% CI: 52.4–69.3) of pregnant women presenting levels of CdB above the references suggested in the literature. However, As was not detected in nearly 97% of the participants, while few had elevated levels of PbB (5.1; 95% CI: 2.1–10.1%) and MnH or MnTn, (4.3; 95% CI: 2.3–10.1%). Low socioeconomic status, burning household waste, being passive smokers, multiparity, and renovating their homes were factors associated with the participants' high Mn, Pb, and Cd levels. Paper 3) Considering the newborns included in the analysis, the medians (25th percentile – 75th percentile) of PbB, CdB, MnH, and MnTn were, respectively, 0.9 (0.5–1.8) μg/dL; 0.54 (0.1–0.8) μg/L; 0.18 (0.1–0.4) μg/g and 0.65 (0.37–1.22) μg/g. Girls and boys presented 3,067 (426.3) and 3,442 (431) grams of BW, respectively, as means (standard deviation). We found an influence of PTMs on BW according to sex; since the inverse correlation between MnTn and the BW/GA ratio was only in girls (rho= –0.478; p=0.018). Although the relationship between BW and CdB was not statistically significant, hierarchical linear regression (Beta= –2.08; 95%CI -4.58 to 0.41) Suggested a foetotoxic effect. Conclusion: The theoretical part of this work presented an environmental health perspective based on theoretical models of human sciences to have a broader approach to studying pollutant toxicity in human beings. This look is even more critical in developing countries like Brazil. Regarding the exploratory investigation, we found low exposure to Pb and Mn besides a high level of Cd in pregnant women recruited by the study DSAN-12M. We confirm the threat these PTMs represent to fetal growth, thus demonstrating the urgency of implementing biomonitoring, especially in vulnerable populations.