Manganese exposure and association with hormone imbalance in children living near a ferro-manganese alloy plant

Abstract

It has been suggested that manganese (Mn) plays a fundamental role in the reproductive system through interference with the regulation of the secretion of hormones related to puberty. The objective of this study was to evaluate the environmental exposure to Mn and its effects on the endocrine regulation of hormones related to puberty in school-aged children living near a ferro-manganese alloy plant. Toenails, occipital hair, and blood samples were collected from 225 children, between 7 and 12 years of age, in four elementary schools in Simões Filho, Bahia, Brazil, who were exposed to different Mn levels owing to different Mn dust deposition rates. The Mn content was determined in the toenails (MnTn), hair (MnH), and blood (MnB), in addition to blood lead levels (PbB), by using graphite furnace atomic absorption spectrometry. Luteinizing hormone (LH), prolactin (PRL), estradiol (E2), testosterone (T), and thyroid stimulating hormone (TSH) levels were determined by using a chemiluminescence method. Of the total participants, 50.2% were boys, with an average age of 9 years. PRL values were higher in children attending the school with a higher Mn deposition rate (p < 0.004). We observed that MnTn was positively correlated with PRL levels and exhibited a non-linear association with LH levels. None of the tested Mn biomarkers were associated with E2, T, or TSH levels. To date, despite several animal studies that have focused on the correlation between Mn exposure and the endocrine regulation of hormones and pubertal development, very few studies have reported a similar relationship between environmental Mn effects and the human endocrine system. Our findings support the hypothesis that elevated exposure to Mn in children may be associated with hormonal imbalances that might trigger the early onset of puberty.