Women who were exposed to the banned bug spray chemical DDT during pregnancy are more than twice as likely to have children with autism, a new study suggests.
Chemicals seem to be everywhere and their dangers are becoming clearer.
An Environmental Working Group report revealed Wednesday that the same Roundup weedkiller that a jury ruled last week gave a man terminal cancer is in many cereals.
Now, an an unprecedented study of one million Finnish women, scientists used a biomarker for DDT in the blood of pregnant women to show the effects of the insecticide for the first time.
The potent bug-killing chemical was banned in most countries more than 30 years ago because it takes so long to break down in the environment that people get exposed to dangerous levels of it.
DDT was once used worldwide to kill pests that ruin crops. It was banned more than 30 years ago, but children exposed to it in the womb are still at double the risk of autism, study suggests
At high concentrations, exposure to DDT has been known to cause tremors, seizures and nausea and may be carcinogenic to humans.
But the new Columbia University research is the first to establish such a concrete link between DDT and autism.
About one in every 59 people born in the US will be on the autism spectrum, yet we remain unsure of what causes it.
The prevailing theory is that some people may be more genetically vulnerable to the developmental disorder, but that other factors, including environmental ones, play an equally important role.
Autism has also been on the rise in the US, where 15 percent more people are thought to be diagnosed annually than were back in 2004.
Many analysts suspect that this is largely a reflection of more widespread awareness of the condition – the prevalence of which the Centers for Disease Control and Prevention only started tracking in 2000.
But there are certainly more man-made chemicals in our environment today than there were a century ago, and studies like Columbia’s suggest these substances may be having a measurable effect on our health.
And those chemicals are sticking around.
‘In spite of the fact that [chemicals like DDT and PCBs] were banned in the 1970s, they remain prevalent in the environment,’ lead study author Dr Alan Brown told Daily Mail Online.
‘Now we know it stays around a decade or two, rather than a few years, so it will probably remain in the environment for some time longer.’
Dr Brown and his team in the Epidemiology department Columbia’s Mailman School of Public Health analyzed an unusually comprehensive data set the covered nearly every Finnish woman that had a child between 1987 and 2005.
Each woman had blood drawn and tested for metabolites of DDT and PCBs (a group of potentially toxic industrial chemicals) early in her pregnancy.
The women who had high level in their blood were more than twice as likely to be a mother to one of the 778 children who developed autism and an intellectual disability.
PCBs did not seem to have this effect, but the substantial increase in risk linked to the bug killer was cause for serious concern to the study authors.
Those children were all born long after the DDT ban.
It isn’t clear how DDT might lead to autism, but Dr Brown says it could have to do with inhibiting the male sex hormone or epigenetic effects.
Regardless of how the mechanism works, the new study makes it clear that the chemicals stick around to wreak havoc for much longer than previously thought.
‘We’re stuck with it. It can’t be removed from the environment, though it might be possible that we can limit our exposure by eating more organic fruit and vegetables or not living near toxic waste sites.’
We know that DDT is hardly the only chemical lingering in our environment, but we need to be paying attention to what we come into contact with and what those substances do, Dr Brown cautions.
‘This study suggests that we need to be testing additional chemicals that are related to autism,’ like flame retardants and BPA, found in can lining, Dr Brown says.
‘It can take 10 years to develop autism, so we need to be paying attention to longer term effects, rather than assuming that chemicals like these are safe.’