Do toxic chemicals in the environment cause autism? Nicholas Kristof of the NY Times asked that question in his column last week. The number of children with autism spectrum disorders has been rising for several years. Kristof’s concern was provoked by a report last month in the journal Current Opinion in Pediatrics. The article, authored by a professor at Mount Sinai School of Medicine, reviewed evidence that linked autism to substances in the environment. The abstract says:
Indirect evidence for an environmental contribution to autism comes from studies demonstrating the sensitivity of the developing brain to external exposures such as lead, ethyl alcohol and methyl mercury. But the most powerful proof-of-concept evidence derives from studies specifically linking autism to exposures in early pregnancy – thalidomide, misoprostol, and valproic acid; maternal rubella infection; and the organophosphate insecticide, chlorpyrifos. There is no credible evidence that vaccines cause autism.
Late last year, the CDC presented a summary of the results of its Autism Surveillance Survey, which showed a 57% rise in the prevalence of this group of developmental disorders, which may severely impair social, intellectual and behavioral functioning of children.
The surveyors used telephone interviews to sample ten communities nationwide in 2002 and 2006. They asked questions regarding the presence of an autism spectrum disorder (ASD) among 8-year-old children. An average of 9 children per 1000, slightly less than 1%, had an ASD. Comparing the two years, nine of ten communities showed an increased ASD prevalence, ranging from 27% to 95%, averaging 57%.
The increase was found all groups of children—boys, girls, and all races, ethnic groups, and cognitive-function groups. But boys were affected more than four times as frequently as girls, and the increase in prevalence was 25% greater in boys.
Although some of the rise might come from improved detection and recognition of ASD, the agency commented, “A true increase in risk cannot be ruled out. We know there are multiple complex genetic and environmental factors which result in multiple forms of autism and we have much to learn about the causes.”
In a similar vein, last September in the journal Environmental Health Perspectives a report on phthalates appeared. These are substances used in many plastics and cosmetics.
Phthalates have been controversial in recent years because they are thought possibly to disrupt endocrine functions, particularly in young children. Phthalates are not chemically bonded within the products in which they occur, and the chemicals may leach into skin, liquids in plastic containers, and the environment.
The September article in the environmental journal reported correlations between phthalate metabolite concentrations in maternal urine samples taken in third trimester of pregnancy and subsequent poor scores of the children on assessments of variety of behavioral abnormalities—aggression, conduct problems, attention problems and depression.
So many chemicals are used in modern technological societies! In my view, it would not be surprising that some of the medical and behavioral disorders of children that are increasingly prevalent in recent years are caused or exacerbated by toxic effects of some of these chemicals.
The Europeans have made more progress than Americans in investigating the huge variety of synthetic substances used in manufactured products. In 2007, the European Commission began implementation of REACH, a regulation requiring “the Registration, Evaluation, Authorisation and Restriction of Chemical substances.” The law aims to “to improve the protection of human health and the environment through the better and earlier identification of the intrinsic properties of chemical substances.”
If America will not move forward as aggressively as Europe in this regard, we can at least hope that we may have the European data on which to base our decisions.