Written by Angeline A. De Leon, Staff Writer. The one hundred children with autism spectrum disorder had significant higher hair levels of mercury, lead, and aluminum compared with the 100 healthy children.

autism - brain healthAutism refers to a range of conditions involving difficulty with social skills, communication challenges, and in some cases, cognitive impairment 1. Emerging evidence suggests that the rise in the prevalence of autism may be linked to certain environmental factors, particularly prenatal exposure to toxic agents 2. A recent meta-analysis reported that almost 75% of investigated studies detected a significant association between a diagnosis of autism and exposure to at least one toxic heavy metal 3. Chemical exposure to metals is pervasive and may involve various sources, including fertilizers, industrial paints, silver dental fillings, and lead. In pregnant women, the accumulation of toxic heavy metals in the tissue is transferable to the fetus 4, where its disturbance of normal developmental progression may incur damaging, long-lasting effects on the brain and nervous system of the infant. As a result, a range of neurological, behavioral, sensory, and motor abnormalities, representative of the symptoms of autism, gradually develops 5. To better understand the etiology of autism and the role of environmental risk factors, researchers at Ains Shams University in Cairo, Egypt (2015) examined levels of mercury, lead, and aluminum exposure in children with autism spectrum disorder (ASD).

A total of 200 children (aged 2.5-15 years) carrying a diagnosis of ASD according to the DSM-IV TR were recruited for participation in a case control study. 100 children with ASD were age- and gender-matched to a control group of 100 healthy children. All patients underwent a detailed history assessment examining maternal history of metal exposure, developmental history, and potential environmental toxic exposures. Hair mineral analysis was used to measure long-term metal exposure to mercury, lead, and aluminum.

The comparative analysis revealed that mean levels of mercury, lead, and aluminum were significantly higher in the hair samples of ASD children vs. controls (p = 0.015, p = 0.023, p = 0.0001, respectively). A significant positive correlation was also observed between heavy metal exposure levels and maternal intake of fish (with high mercury levels), dwelling in close proximity to gasoline stations, and usage of aluminum pans (p = 0.026, p = 0.047, p = 0.04, respectively). Unexpectedly, however, no significant association was found between levels of heavy metal exposure and severity of autism.

Overall findings provide evidence confirming the damaging effects of toxic heavy metal exposure on the normal neurological development of infants. The etiology of ASD appears to be associated with vulnerability to environmental insults, with prenatal factors such as mothers’ dietary habits playing a role. Primarily limited by its use of a smaller sample size, the present study should be replicated in the future, potentially using a longitudinal design.

Source: Mohamed FEB, Zaky EA, El-Sayed AB, et al. Assessment of hair aluminum, lead, and mercury in a sample of autistic Egyptian children: Environmental risk factors of heavy metals in autism. Behavioral Neurology. 2015. DOI: 10.1155/2015/545674.

Copyright © 2015 Farida El Baz Mohamed et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Posted October 30, 2017.

Angeline A. De Leon, MA, graduated from the University of Illinois at Urbana-Champaign in 2010, completing a bachelor’s degree in psychology, with a concentration in neuroscience. She received her master’s degree from The Ohio State University in 2013, where she studied clinical neuroscience within an integrative health program. Her specialized area of research involves the complementary use of neuroimaging and neuropsychology-based methodologies to examine how lifestyle factors, such as physical activity and meditation, can influence brain plasticity and enhance overall connectivity.

References:

  1. Association AP. DSM-5 Autism spectrum disorder fact sheet. Arlington, VA: American Psychiatric. 2013.
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  5. Austin D. An epidemiological analysis of the ‘autism as mercury poisoning’hypothesis. International Journal of Risk & Safety in Medicine. 2008;20(3):135-142.