"Long before it's in the papers"
January 27, 2015


Pesticide robs kids of IQ points, study finds

April 23, 2011
Courtesy of UC Berkeley
and World Science staff

Pre­na­tal ex­po­sure to a class of pes­ti­cides widely used on food crops is re­lat­ed to low­er in­tel­li­gence scores at age sev­en, a U.S. study has found.

Re­search­ers ad­vised con­sumers to thor­oughly wash fruits and veg­eta­bles, us­ing a soft brush if prac­ti­cal—but urged peo­ple not cut down on these nu­tri­tious foods, al­ready too of­ten passed over by Amer­i­cans.

The sci­en­tists at the Un­ivers­ity of Cal­i­for­nia, Berke­ley found that eve­ry ten­fold in­crease in meas­ures of organophos­phate pes­ti­cides de­tected dur­ing a moth­er’s preg­nan­cy cor­re­sponded to a 5.5 point drop in overall IQ scores in the sev­en-year-olds.

“These as­socia­t­ions are sub­stantial, es­pe­cially when view­ing this at a popula­t­ion-wide lev­el,” said study prin­ci­pal in­ves­ti­ga­tor Bren­da Es­ke­nazi. “That dif­fer­ence could mean, on av­er­age, more kids be­ing shifted in­to the low­er end of the spec­trum of learn­ing, and more kids need­ing spe­cial ser­vic­es in school.”

The study is among three pa­pers re­port­ing an as­socia­t­ion be­tween ex­po­sure to the pes­ti­cides and child­hood IQ pub­lished on­line April 21 in the jour­nal En­vi­ron­men­tal Health Per­spec­tives. The oth­er two stud­ies, from Mt. Si­nai Med­i­cal Cen­ter and Co­lum­bia Un­ivers­ity in New York, ex­am­ined popula­t­ions in that ­city, while the Berke­ley study fo­cused on chil­dren liv­ing in Sa­li­nas, an ag­ri­cul­tur­al cen­ter in Mon­te­rey Coun­ty, Cal­if.

“It is very un­usu­al to see this much con­sist­en­cy across popula­t­ions in stud­ies,” said lead au­thor Maryse Bou­chard, who was work­ing as a UC Berke­ley post-doctoral re­search­er with Es­ke­nazi while the study was un­der­way. 

Organophos­phates are a class of pes­ti­cides tox­ic to brain cells, ac­cord­ing to the re­search­ers. In­door use of chlor­pyri­fos and di­azi­non, two com­mon forms of the pes­ti­cides, has been phased out over the past dec­ade, mainly be­cause of health risks to chil­dren. The 329 chil­dren in the UC Berke­ley study had been fol­lowed from be­fore birth. Their preg­nant moth­ers had pre­vi­ously pro­vid­ed urine sam­ples that were tested for break­down prod­ucts of the pes­ti­cides.

The lev­els of pes­ti­cides found in the wom­en in the Berke­ley study were some­what high­er than av­er­age com­pared with the U.S. popula­t­ion, but not ab­nor­mally high, the in­ves­ti­ga­tors said. “These find­ings are likely ap­pli­ca­ble to the gen­er­al popula­t­ion,” said Bou­chard. “In ad­di­tion, the oth­er two stud­ies be­ing pub­lished were done in New York ­city, so the con­nec­tion be­tween pes­ti­cide ex­po­sure and IQ is not lim­it­ed to peo­ple liv­ing in an ag­ri­cul­tur­al com­mun­ity.”

Ac­cord­ing to the U.S. Cen­ters for Dis­ease Con­trol, peo­ple are ex­posed to organophos­phate pes­ti­cides through eat­ing foods from crops treated with these chem­i­cals. Farm work­ers, gar­den­ers, florists, pes­ti­cide ap­pli­ca­tors and ma­n­u­fac­tur­ers of these in­sec­ti­cides may have great­er ex­po­sure than the gen­er­al popula­t­ion.

“Many peo­ple are al­so ex­posed when pes­ti­cides are used around homes, schools or oth­er build­ings,” said study co-au­thor Asa Brad­man at Berke­ley. The re­search­ers rec­om­mended that con­sumers re­duce their home use of pes­ti­cides, not­ing that most home and gar­den pests can be con­trolled with­out those chem­i­cals. If pes­ti­cides are needed, they said bait sta­t­ions should be used in­stead of sprays.

They al­so said con­sumers should thor­oughly wash fruits and veg­eta­bles; go be­yond a quick rinse and use a soft brush, if prac­ti­cal. Con­sumers could al­so con­sid­er buy­ing or­gan­ic pro­duce when pos­si­ble as a way to re­duce pes­ti­cide ex­po­sure from food, they said.

“I’m con­cerned about peo­ple not eat­ing right,” said Es­ke­nazi. “Most peo­ple al­ready are not get­ting enough fruits and veg­eta­bles in their di­et, which is linked to se­ri­ous health prob­lems in the Un­ited States. Peo­ple, es­pe­cially those who are preg­nant, need to eat a di­et rich in fruits and veg­eta­bles.”

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Prenatal exposure to a class of pesticides widely used on food crops is related to lower intelligence scores at age seven, a U.S. study has found. Researchers advised consumers to thoroughly wash fruits and vegetables, using a soft brush if practical—but urged people not cut down on these nutritious foods, already too often passed over by Americans. The scientists at the University of California, Berkeley found that every tenfold increase in measures of organophosphate pesticides detected during a mother’s pregnancy corresponded to a 5.5 point drop in overall IQ scores in the seven-year-olds. Children in the study with the highest levels of prenatal pesticide exposure scored seven points lower on a standardized measure of intelligence compared with children with the lowest levels of exposure. “These associations are substantial, especially when viewing this at a population-wide level,” said study principal investigator Brenda Eskenazi. “That difference could mean, on average, more kids being shifted into the lower end of the spectrum of learning, and more kids needing special services in school.” The study is among three papers reporting an association between pesticide exposure and childhood IQ to be published online April 21 in the journal Environmental Health Perspectives. The other two studies, from Mt. Sinai Medical Center and Columbia University in New York, examined populations in that city, while the Berkeley study focused on children living in Salinas, an agricultural center in Monterey County, California. “It is very unusual to see this much consistency across populations in studies,” said lead author Maryse Bouchard, who was working as a UC Berkeley post-doctoral researcher with Eskenazi while the study was underway. Organophosphates are a class of pesticides toxic to brain cells, according to the researchers. Indoor use of chlorpyrifos and diazinon, two common forms of the pesticides, has been phased out over the past decade, mainly because of health risks to children. The 329 children in the UC Berkeley study had been followed from before birth. Their pregnant mothers had previously provided urine samples that were tested breakdown products of the pesticides. The levels of pesticides found in the women in the Berkeley study were somewhat higher than average compared with the U.S. population, but not abnormally high, the investigators said. “These findings are likely applicable to the general population,” said Bouchard. “In addition, the other two studies being published were done in New York City, so the connection between pesticide exposure and IQ is not limited to people living in an agricultural community.” According to the Centers for Disease Control, people are exposed to organophosphate pesticides through eating foods from crops treated with these chemicals. Farm workers, gardeners, florists, pesticide applicators and manufacturers of these insecticides may have greater exposure than the general population. “Many people are also exposed when pesticides are used around homes, schools or other buildings,” said study co-author Asa Bradman at Berkeley. The researchers recommended that consumers reduce their home use of pesticides, noting that most home and garden pests can be controlled without those chemicals. If pesticides are needed, they said bait stations should be used instead of sprays. They also said consumers should thoroughly wash fruits and vegetables; go beyond a quick rinse and use a soft brush, if practical. Consumers could also consider buying organic produce when possible as a way to reduce pesticide exposure from food, they said. “I’m concerned about people not eating right,” said Eskenazi. “Most people already are not getting enough fruits and vegetables in their diet, which is linked to serious health problems in the United States. People, especially those who are pregnant, need to eat a diet rich in fruits and vegetables.”