Mercury in first-cut baby hair of children with autism versus typically-developing children

Abstract

Children with autism were examined to determine amounts of mercury (Hg) in their baby hair and the factors that might affect Hg body burden. US children with autism (n = 78) and matched controls (n = 31) born between 1988 and 1999 were studied. Hg in first-cut baby hair was determined using cold vapor atomic fluorescence spectrometry (CVAFS). Twenty samples were split and also measured with Neutron Activation Analysis (NAA). Logistic regression analysis showed that compared to children with higher levels of mercury (above 0.55 mcg g⁻¹), children with lower levels of mercury in their hair (below 0.55 mcg g⁻¹) were 2.5-fold more likely to manifest with autism. Children with autism had similar mercury exposure as controls from maternal seafood and maternal dental amalgams. Children with autism also had 2.5-fold higher incidence of oral antibiotic use during their first 18 months of life. Their mothers were possibly more likely to use oral antibiotics during pregnancy or nursing. The amount of Hg in the baby hair of children with autism showed a significant correlation with the number of maternal dental amalgams. The lower level of Hg in the baby hair of children with autism indicates an altered metabolism of Hg, and may be due to a decreased ability to excrete Hg. This is consistent with usage of higher amounts of oral antibiotics, which are known to inhibit Hg excretion in rats due to alteration of gut flora, and may exert a similar effect in humans. Higher usage of oral antibiotics in infancy may also partially explain the high incidence of chronic gastrointestinal problems seen in individuals with autism.

Keywords:

• autism
• mercury
• baby hair
• antibiotics
• amalgams

Acknowledgements

First and foremost, we thank the many autism families and their friends who volunteered as participants in this research study. We thank the Autism Research Institute for partial financial support of this study. We thank NIEHS for contracting with RTI International to have the hair samples tested. We thank Xianchen Liu and Barry Grushkin for their help with the statistical analysis. We thank Amy Holmes, Mark Blaxill, and Boyd Haley for sharing their results with us and for useful discussions. We thank Eva Gehn for her help with the data analysis.