Australian researchers have identified a potential biological link between exposure to the plastic additive di-2-ethylhexyl phthalate (DEHP) during pregnancy and later symptoms associated with autism and attention deficit hyperactivity disorder (ADHD).
The study by the Melbourne-based Florey Brain Research Centre examined concentrations of phthalates in the umbilical cords of pregnant women before using artificial intelligence to analyse the children’s DNA.
Researchers found that DEHP exposure was associated with changes in the way certain genes were switched on or off before birth. Those changes were, in turn, linked with a higher risk of autism and ADHD symptoms at the ages of two and four.
Professor Anne-Louise Ponsonby, the Florey’s head neuroepidemiologist, said previous research had found a correlation between high DEHP levels and the two conditions, while the new work suggested a possible biological explanation.
“At the gene-switching level, that pattern was associated with a higher risk of later autism and attention deficit hyperactivity symptoms at ages 2 and 4,” Professor Ponsonby said.
“We call that an epigenetic signature because it seems to be an alteration associated with that high chemical at the gene-switching level.”
She stressed that the children were still too young for firm conclusions to be drawn about the effects of DEHP, and said there could be a wide range of causes behind either condition.
“We also like picking up early life symptoms at (ages) 2 or 4 because that’s closer to pregnancy,” she said. “Obviously, if you get diagnosed with one of these conditions at age 30, you probably had a different type of causes.”
Where DEHP is found
DEHP is used to make plastic more flexible and can be found in products including rainproof clothing, garden hoses, sprinklers, shower curtains and bin liners. Plastic toys containing more than 1 per cent DEHP are banned in Australia.
Professor Ponsonby said people could be exposed to the chemical more widely than they might realise, particularly when plastic is heated or comes into contact with water. She said irrigation systems using DEHP could allow it to spread into homes and across farmland.
The research team will continue to monitor the children as they grow to assess whether the chemical has a longer-term effect. It also found that the gene changes associated with DEHP were more likely to remain in place when a child had a high-nutrition diet in the womb.
Professor Ponsonby said the findings added to calls for greater controls on plastics and manufactured chemicals, both for human health and the environment.
“So we might have to collectively — with all the governments around the world — think about this again,” she said.
