Children exposed to organophosphate pesticide residues found in fruit are at increased risk of developing Attention-Deficit Hyperactivity Disorder (ADHD), according to a US study.
Scientists from the University of Montreal and Harvard University measured pesticide levels in the urine of 1,139 children, aged 8-15, 119 of whom had ADHD. They found those with higher amounts of pesticide residue were twice as likely to be diagnosed with the disorder compared to children with undetectable levels.
Previous studies have focused on populations with high levels of exposure, such as agricultural workers, but this is the first to suggest a risk to the general population from low-level exposure to pesticide residues.
'A key point of our paper is that it was among a generally representative sample of the US, so these kids had lower exposure levels than what one might find among those at high risk from exposure (such as those using sheep dips),' said co-author Marc Weisskopf.
The study said children in particular were considered to be at greater risk from organophosphate toxicity because the developing brain is more susceptible to neurotoxicants and the dose of pesticides per body weight is likely to be larger for them.
The main source of exposure for infants and children is diet. The US Pesticide Residue Program Report 2008 found detectable concentrations of the organophosphopate malathion, an insecticide, in 28 per cent of frozen blueberry, 25 per cent of fresh strawberry and 19 per cent of celery samples.
In the UK, surveys from the Pesticides Residue Committee have found residues of four organophosphorus pesticides in peppers and residues of malathion in pears, grapes, grapefruit and citrus fruits.
The US Environmental Protection Agency (EPA) has also said drinking water and residential pesticide use are potential sources of exposure.
Previous research has shown that exposure to some organophosphate compounds cause hyperactivity and cognitive deficits in animals, but this study is one of the first to find that exposure may also have similar effects on the developing neurological systems of children.
'What is really needed is a prospective study, where mothers are enrolled when pregnant and measurements of organophosphate exposure taken over the course of the child's life (and during the mother's pregnancy), and relating those to the likelihood of subsequent development of ADHD. Our study measured exposure and ADHD at the same time,' said Weisskopf.
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