Mercury (Hg) Exposure in Breast-Fed Infants and Their Mothers and the Evidence of Oxidative Stress

Abstract

The objective of this work was to assess exposure to mercury (Hg) and its induction of oxidative stress in 155 healthy lactating Saudi mothers and their infants. Samples of breast milk and blood were collected from the mothers, while urine was taken from both infants and mothers. Both urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) and malondialdehyde (MDA) were measured in mothers and infants as biomarkers of oxidative stress. The mean concentration of Hg in breast milk was 1.19 μg/L (range 0.012-6.44 μg/L) with only one mother having Hg >4 μg/L, the upper limit established by the US Agency for Toxic Substance and Disease Registry. However, 57.4 % had Hg ≥1 μg/L, the background level for Hg in human milk. The mean urinary Hg corrected for creatinine (Hg-C) in mothers and infants was 1.47 and 7.90 μg/g creatinine, respectively, with a significant correlation between the two (p < 0.001). Urinary Hg levels over 5 μg/g creatinine (the background level in an unexposed population) were found in 3.3 % of mothers and 50.1 % of infants. None of the mothers had total blood Hg above the US Environmental Protection Agency's maximum reference dose of 5.8 μg/L. No correlation was noted between urinary Hg in infants and Hg in breast milk (p > 0.05). Hg in breast milk, though, was associated with Hg in blood (p < 0.001), suggesting the efficient transfer of Hg from blood to milk. Hg in the breast milk of mothers and in the urine of infants affected the excretion of urinary MDA and 8-OHdG, respectively, in a dose-related manner. These findings reveal for the first time lactational exposure to Hg-induced oxidative stress in breast-fed infants, which may play a role in pathogenesis, particularly during neurodevelopment. This will also contribute to the debate over the benefits of breast milk versus the adverse effects of exposure to pollutants. Nevertheless, breastfeeding should not be discouraged, but efforts should be made to identify and eliminate the source of Hg exposure in the population.

The impact of the use of amalgam in dental treatment on the prevalence of restless legs syndrome in older people

“…This affected their urinary excretion, some become light phobic and had neurological difficulties such as flaccid muscles [34]. Mercury is known to enter breast milk [35] following a mother's exposure to Hg. In addition, Hg may enter the child's body from childhood vaccinations because thimerosal is used as a preservative in vaccinations.…”

Metalloproteomics Approach to Analyze Mercury in Breast Milk and Hair Samples of Lactating Women in Communities of the Amazon Basin, Brazil

“…They take up high amounts of these substances through their gastrointestinal tracts, their brains are at early developmental stages, and their metabolic pathways are immature and can be easily disturbed by toxic elements such as mercury. Other factors, such as low body mass and high food and water uptake in relation to body mass, may also increase susceptibility to environmental toxicants [8,9]. Exposure of both men and women to toxical metals during the reproductive ages, even in relatively small doses, can have impacts on fetal growth and development.…”

“…Human breast milk can contain toxic metals, including mercury, depending on the exposure of the mother. Thus, infants may be subjected to deleterious and neurotoxic effects of mercury, including severe brain damage [8,12,13]. Studies on the toxicodynamics of mercury are therefore of fundamental importance for the health of human populations in the Amazon region.…”

Metalômica aplicada ao estudo de toxicidade do mercúrio em amostras de leite humano coletadas de lactantes residentes em comunidades do alto rio Madeira, Rondônia, Brasil

“…Durante a lactação, as crianças estão sujeitas à exposição ao Hg em suas formas orgânica e inorgânica (BJORNBERG et al, 2005;SUNDBERG et al, 1999), ambas espécies mercuriais podem chegar ao recém-nascido após a passagem da glândula mamaria, inserindo ao colostro e ao leite materno (AL-SALEH et al, 2013;VIEIRA, et al, 2013).…”

“…Ou seja, quanto mais exposta a lactante estiver, maior será a exposição do filho. Contudo, por ainda estarem em desenvolvimento neurológico e possuírem mecanismos de desintoxicação imaturos, crianças são potencialmente mais suscetíveis aos efeitos do Hg quando comparadas aos adultos (AL-SALEH et al, 2013;MOLINA-VILLALBA et al, 2015).…”