Air pollution linked to autism

Exposure to diesel particulates, heavy metals doubles the risk

By Soundaram Ramanathan
Published: Wednesday 31 July 2013

imageA MOTHER-TO-BE exposed to high levels of air pollution is at a higher risk of giving birth to a child with autism, say researchers at Harvard School of Public Health (HSPH) in the US.

Autism is a neuro-development disorder that manifests by the age of three. An autistic child typically has difficulties in communication, has trouble learning, adjusting to changes and does the same thing over and over, like repeating a word. “So far there is no cure for autism and the disorder has to be managed so that the child can lead an independent life,” says Praveen Suman, pediatrician at Sir Ganga Ram Hospital in Delhi. Though scientists are yet to determine what causes autism, there is increasing evidence that environmental factors affecting the womb could be behind the developmental disorder.

To look at associations between autism and pollutants, HSPH researchers crunched data from Nurses’ Health Study II, a long-term study at Brigham and Women’s Hospital in the US, that began in 1989. Of the 116,430 nurses involved in the study, the authors studied 325 women who had a child with autism and 22,000 women with children without the disorder.

They used air pollution data from the US Environmental Protection Agency to estimate the women’s exposure to pollutants during pregnancy. The results show that women who live in locations with the highest levels of diesel particulates or mercury in the air are twice as likely to have a child with autism as those who live in less polluted areas. Other types of air pollutants—lead, manganese and methylene chloride—are also associated with higher autism risk, notes the study published online in Environmental Health Perspectives on June 18.

The researchers now plan to measure individual women’s exposure to air pollution, possibly by collecting blood while they are pregnant. “This will give us better evidence for which of these pollutants are responsible for autism and help develop interventions to reduce pregnant women’s exposure to these pollutants,” says lead researcher Andrea Roberts.

The study holds hope for India, where one in every 100 children suffers from autism. Parasuram Ramoorthi, chairperson of non-profit Velvi trust, says the prevalence rate of autism is high in states with high pollution and industrial clusters. However, it would be difficult to implement findings of the HSPH study in India because the country’s pollution control boards do not measure the concentration of individual pollutants in the ambient air. Besides, the government has no figure on the actual number of autistic children.

“Health and environment ministries should join hands with the social justice ministry and work toward the cause, prevention and treatment of autism,” says Ramoorthi.

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