Blood Mercury Concentrations in CHARGE Study Children with and without Autism

Environ Health Perspect. 2010 Jan;118(1):161-6.

Blood Mercury Concentrations in CHARGE Study Children with and without Autism.

Hertz-Picciotto I, Green PG, Delwiche L, Hansen R, Walker C, Pessah IN. Department of Public Health Sciences.

Background: Some authors have reported higher blood mercury (Hg) levels in persons with autism, relative to unaffected controls.Objectives: We compared blood total Hg concentrations in children with autism or autism spectrum disorder (AU/ASD) and typically developing (TD) controls in population-based samples, and determined the role of fish consumption in differences observed.

Methods: The Childhood Autism Risk from Genetics and the Environment (CHARGE) Study enrolled children 2-5 years of age. After diagnostic evaluation, we analyzed three groups: AU/ASD, non-AU/ASD with developmental delay (DD), and population-based TD controls. Mothers were interviewed about household, medical, and dietary exposures. Blood Hg was measured by inductively coupled plasma mass spectrometry. Multiple linear regression analysis was conducted (n = 452) to predict blood Hg from diagnostic status controlling for Hg sources.Results: Fish consumption strongly predicted total Hg concentration. AU/ASD children ate less fish. After adjustment for fish and other Hg sources, blood Hg levels in AU/ASD children were similar to those of TD children (p = 0.75); this was also true among non-fish eaters (p = 0.73). The direct effect of AU/ASD diagnosis on blood Hg not through the indirect pathway of altered fish consumption was a 12% reduction. DD children had lower blood Hg concentrations in all analyses. Dental amalgams in children with gum-chewing or teeth-grinding habits predicted higher levels.

Conclusions: After accounting for dietary and other differences in Hg exposures, total Hg in blood was neither elevated nor reduced in CHARGE Study preschoolers with AU/ASD compared with unaffected controls, and resembled those of nationally representative samples.

Editor's Summary: Mercury has been investigated as a possible cause of autism, but its association with autism remains uncertain. Hertz-Picciotto et al. (p. 161) examined blood Hg levels and sources of Hg exposure among participants in the Childhood Autism Risk from Genetics and the Environment (CHARGE) Study, including 2- to 5-year-old children classified as having autism or an autism spectrum disorder (autism/ASD, n = 249), developmental delay (DD, n = 60), and typical development (TD population-based controls, n = 143) based on standardized criteria and clinical examination. Information on household, medical, and dietary exposures was provided by mothers, and blood Hg was measured by inductively coupled plasma mass spectrometry. Fish consumption strongly predicted blood Hg, and lower average blood Hg levels observed in the autism/ASD group were consistent with lower levels of fish consumption in autism/ASD children compared with TD controls. In addition, multiple linear regression model predictions indicated comparable blood Hg levels in autism/ASD and TD children when adjusted for differences in fish consumption. Lower blood Hg levels observed in all analyses for children with DD versus TD or autism/ASD may have been a chance finding, but the authors propose that metabolic differences should also be investigated. The authors also note that findings do not rule out an effect of early Hg exposure on the etiology of autism/ASD because associations were measured after diagnosis.

PMID: 20056569 [PubMed - in process]