Autism has long been a mystery to scientists and medical practitioners, with direct causes remaining unknown. However, new research suggests that the disorder could be linked to a range of environmental factors, including exposure to certain toxins in areas with high levels of air pollution, which can lead to double the chance of giving birth to a child with autism. The study also found a link between genital malformations at the time of birth, such as micropenis and undescended testicles.
Indeed, a one percent increase in genital malformations was tied to a 283% increase in autism rates, as well as a 94 percent increase in intellectual disability rates. The rates of all three conditions were particularly high in young boys, with male fetuses found to be particularly vulnerable.
The study was compiled from data provided in a 100 million-strong insurance claims database, with genital malformations serving as the prime indicator for parental exposure to hazardous air pollution. "Autism appears to be strongly correlated with rate of congenital malformations of the genitals in males across the country. This gives an indicator of environmental load and the effect is surprisingly strong," said Professor Andrey Rzhetsky, the lead author of the study.
Rzhetsky also points to genetics and geography as contributing factors to autism, cautioning the environment, while crucial, is not the only player. "For future genetic studies we may have to take into account where data were collected, because it's possible that you can get two identical kids in two different counties and one would have autism and the other would not," he said.
Another - though considerably weaker - link in the study was found between income and autism rates, with each additional $1000 in annual income (over the county average) thought to be representative of a further 3 percent chance of autism. More tellingly, state-mandated laws affected rates of autism diagnosis in separate counties, with counties falling under compulsory pediatric screening for inclusion in the special education system contributing to a substantial 99 percent downslide in rates of autism and intellectual disability.
The study, titled Environmental and State-Level Regulatory Factors Affect the Incidence of Autism and Intellectual Disability, was published in PLOS Computational Biology.
