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Wayne State researcher studies damaging effects of fetal pesticide exposure on the neurodevelopment of toddlers

November 10, 2008

DETROIT- Household pesticides have been long-recognized as neurotoxins - substances that can affect the development of brain growth and function, either temporarily or permanently. Now, a new study by a Wayne State University researcher is aiming to vastly expand our understanding of the toxins' damaging effects on the brain during its most important period of development.

Enrique Ostrea, Jr., M.D., professor of pediatrics in Wayne State University's School of Medicine and resident of Farmington Hills, Mich., recently received an R01 grant for more than $2.8 million from the National Institute of Child Health and Human Development (NICHD) to investigate the damages to neurological development caused by pesticides in the fetal environment. The research is a continuation of an earlier R01 NICHD study on a group of children in Malolos, Bulacan, a town in the Philippines, who experienced varying degrees of environmental pesticide exposure while in utero and as toddlers.

The most prevalent pesticides the children were exposed to before birth were propoxur and pyrethroids - two of the most common toxins found in household pesticides worldwide. Neurotoxicants can cause a wide array of damage to developing brains, including areas involved in communication, movement, hearing/language and hand-eye coordination; yet detecting infants who have been exposed has been a largely imprecise science before Ostrea's research. "This has been a major problem, because most of what we previously knew about exposure rates came simply from questionnaires," Ostrea said. "Secondly, if they did screen for the toxicants in biomarkers such as blood and urine, these are only indicators of recent exposure."

In his previous NICHD funded study, Ostrea found a more effective biomarker in meconium - the earliest stools on an infant. Unlike blood and urine, meconium can detect not just recent pesticide exposure, but can indicate exposure starting from the first trimester of pregnancy. Although not as sensitive as meconium, maternal hair also proved an effective biomarker for the two pesticides, which, when combined with measurements taken from meconium, improves detection capabilities almost two fold.

The emergence of these reliable biomarkers facilitated the second goal of Ostrea's previous study - To obtain a better understanding of what exactly propoxur and pyrethroids do to the developing human brain. For babies exposed to propoxur in utero, Ostrea found significant deficits in motor skills and hand-eye coordination once they reached their second year. The pyrethroid-exposed group did not see dysfunctions that were a significantly different from the unexposed group, but this may have been due to small sample size, Ostrea said.

Ostrea's current study will pick up where his previous one left off, testing the children, now four to six years of age, to determine if any of the previously observed neurotoxic effects persist, improve or increase in severity. He will also look for new neurological deficits that may not have been observable by age two but have since become apparent. Finally, he will factor in any post-birth pesticide exposure that has occurred into his analysis. "It's a universal rule in the human body to attempt to repair as much damage as possible," Ostrea said. "But eventually, it comes to a point when compensation can only go so far and eventually, the neurological insults become more evident using more sensitive tests."

Ostrea expects the results of his work will bring to light the neurological damage pregnant women could be causing their unborn children when exposed to toxins as simple as household pesticides. Once the effects are known, it will encourage a standardized screening for pesticide exposure. "Although meconium is the more sensitive biomarker of fetal exposure to environmental pesticides, the advantage of being able to detect the toxicant in maternal hair is that you can intervene during pregnancy," Ostrea said. "That way you can tell her that she's being exposed when she otherwise may not realize it."

Wayne State University is one of the nation's pre-eminent public research universities in an urban setting. Through its multidisciplinary approach to research and education, and its ongoing collaboration with government, industry and other institutions, the university seeks to enhance economic growth and improve the quality of life in the city of Detroit, state of Michigan and throughout the world.