Chemical in Pesticides Linked to Lower IQs in 4th Graders

It is known that pesticides with chemicals like organophosphates can adversely affect nerve development and may lead to long-term toxicity. This study attempted to follow children with organophosphate exposure, prenatally and postnatally, to see if there were any differences in their cognitive development and IQ. The results showed that exposure to these chemicals during pregnancy, as detected by a certain chemical (DAP – dialkyl phosphate) in the urine, is associated with poor school performance and IQ development at 7 years of age. However, the presence of DAP in the children’s urine sample was not linked to low IQ.

Pesticides commonly contain organophosphates. It is known that continuous exposure to these chemicals can harm the brain and the nerves. Children who live near agricultural farms or who are exposed to these chemicals at home, or through ingesting food containing these chemicals, are known to be at the risk of nerve damage. In children, even low doses of exposure to organophosphates can cause serious damage, since their body weight is lower and they have lower levels of enzymes and other agents that can detoxify the chemicals. No studies have followed up exposure to these chemicals in children and checked them for neurological damage and cognitive problems at school. This study attempted to evaluate the connection between exposure to organophosphates and low IQ in school children.

* For this study, 329 seven-year-old children and their mothers were included. The seven-year study began when the mothers were pregnant; it was followed up during the pregnancy and up to the stage when the child reached seven years of age. The children belonged to farming families and resided near agricultural fields.
* Exposure to organophosphates was assessed by measuring urine levels of dialkyl phosphate (DAP).
* The measurements were conducted for the mothers during pregnancy and after delivery. For children, the levels were measured at the age of 6 months, 1, 2, 3.5 and 5 years old. Interviews were also conducted at these ages.
* At the age of 7 years, the IQ of all the children was measured.
* The final analysis took into consideration the mother’s education and intelligence.

Key findings
* The results showed that mean concentration of urinary levels of DAP in pregnant mothers was related to poor working memory, speed of processing information, comprehension of language, reasoning and IQ in the children at school.
* In children whose mothers had the highest level of DAP, the average IQ was found to be at least seven points lower than those whose mothers had low levels of DAP.
* The children’s urine level of DAP, however, was not linked to poor cognitive levels and IQ.

Next steps/shortcomings
The authors agree that studies of this type are difficult to assess, since organophosphates are quickly excreted from the body and do not last more than three to six days in the body. Therefore, it is difficult to quantify the exact level of exposure in the mothers and the children. The authors also suggest that there are many types of organophosphates that are not detected by the DAP measurement. Further detailed studies may aid in understanding the association better.

This study shows that exposure to organophosphates in pesticides, while still within the mother’s womb, is linked to lower cognitive and IQ development in school going children. Exposure to the chemicals after birth was not found to be significantly linked to low IQ and cognitive performance. It was found that the urine DAP levels in the mothers was higher, as compared to the general American population. Therefore, the authors conclude that these mothers are at a higher risk of giving birth to children with poorer intellectual development. The study took into consideration other factors that could have affected IQ in the children, including the mother’s level of intelligence and her educational background. The study sets the stage for further research in the subject.

For More Information:
Prenatal Exposure to Organophosphate Pesticides and IQ in 7-Year Old Children
Publication Journal: Environmental Health Perspectives, April 2011
By Maryse F. Bouchard; Jonathan Chevrier; University of California, Berkeley, Center for Environmental Research and Children’s Health, School of Public Health, Berkeley, California, and Sainte Justine Hospital Research Center & University of Montreal, Quebec, Canada

*FYI Living Lab Reports Are Summaries of the Original Research.

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