Kids who were exposed to organophosphate pesticides while still in mother's womb are more likely to develop attention disorders later in life, a new study has found.
Researchers at the University of California, Berkeley, found that prenatal levels of the pesticides were related to attention problems at age 5, with the effects apparently stronger among boys.
"We were especially interested in prenatal exposure because that is the period when a baby's nervous system is developing the most," said Brenda Eskenazi.
Organophosphate pesticides act by disrupting neurotransmitters, particularly those which are important in sustaining attention and short-term memory.
The study followed more than 300 Mexican-Americans children and their mothers. Living in an agricultural community, their exposure to pesticides is likely higher and more chronic, on average, than that of the general U.S. population.
"It's known that food is a significant source of pesticide exposure among the general population," said Eskenazi.
"I would recommend thoroughly washing fruits and vegetables before eating them, especially if you're pregnant."
The team also found that children with lower levels of paraoxonase 1 (PON1), an enzyme that breaks down the toxic metabolites of organophosphate pesticides, had more neurodevelopmental delays than those with higher levels of the enzyme.
The researchers then evaluated the children at age 3.5 and 5 years for symptoms of attention disorders and ADHD using maternal reports of child behaviour, performance on standardized computer tests, and behaviour ratings from examiners.
Each tenfold increase in prenatal pesticide metabolites was linked to having five times the odds of scoring high on the computerized tests at age 5, suggesting a greater likelihood of a child having clinical ADHD. The effect appeared to be stronger for boys than for girls.
"Symptoms of attention disorders are harder to recognize in toddlers, since kids at that age are not expected to sit down for significant lengths of time," said Amy Marks.
"Diagnoses of ADHD often occur after a child enters school."
Stephen Hinshaw, one of the country's leading experts on ADHD, said that the research indicated that finding preventable risk factors is a major public health concern.
The new findings will be published Aug. 19 in the journal Environmental Health Perspectives (EHP).