Pesticide Exposure and Neurodevelopment in the Fetus

1. Pesticide Exposure and Neurodevelopment in the Fetus Marcel Elizondo July 2009 STEER Student UTHSCSA-Harlingen

2. Pesticides • What is a pesticide? • According to the EPA, a pesticide is “any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any pest” • What about pests? • Pests are “living organisms that occur where they are not wanted or that cause damage to crops or humans or other animals”4

3. Looking at mosquito larvae at the City of Brownsville lab

4. Pesticides • Some examples of pests include: • Pests include mosquitoes, beetles, ants • How do pesticides kill pests? • Pesticides attack the nervous system of the pests which in turn leads to their untimely demise5

5. Elimination of Pesticide Use • Stockholm Convention on Persistent Organic Pollutants • This agreement was signed by 90 countries in 2001 to eliminate the use of 12 POPs including DDT • The World Health Organization made an exception in 2006 to back the use of DDT to control malaria in certain countries2

6. Pesticide Use • In the US, our agricultural areas use more than 75% of conventional pesticides • Exposure to pesticides has been linked to preterm birth and reduced fetal growth • A popular pesticide used to be dichlorodiphenyltrichloroethane (DDT), which was subsequently banned in the US in the 70’s • Currently, replacement pesticides for DDT are insecticides such as organophosphates.1

7. Effects of Some Pesticides • Organochlorines (i.e. DDT) • Excitation of central nervous system which leads to tremors, hyperexcitability and convulsions (both tonic and clonic) • Organophosphate (i.e. insecticides) • Act by inhibiting the acetylcholinesterase in synaptic clefts1

8. Inhibiting the Acetylcholinesterase

9. Inhibiting the Acetylcholinesterase

10. Organophosphate Detection • Exposure to organophosphates is usually measured by nonspecific metabolites in urine known as dialkyl phosphate (DAP) metabolites1

11. DO NOT offer your friends pesticides as a home remedy for cough.

12. Human Studies • Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) • Research is funded by NIH and EPA • Four objectives of CHAMACOS • Six hundred and one pregnant woman were recruited in 1999-2000. They were at least 18 years old and were less than 20 weeks in their gestation period2

13. CHAMACOS • Neonatal neurodevelopment was tested using the Brazelton Neonatal Behavioral Assessment Scales (BNBAS) • Maternal serum samples of DDT and DDE were higher than the National Health and Nutrition Examination Survey reference population • A minor negative association was observed between maternal DDE serum levels and abnormal infant reflexes2

14. CHAMACOS • Most other studies conducted had similar results to the CHAMACOS study • One exception was a study in North Carolina with a birth cohort of 912 infants • In utero exposure discovered that higher levels of DDE in the cord serum and breast milk led to hyporeflexia • This exception is noted because a similar (although smaller) cohort in Oswego, NY was conducted and the North Carolina findings could not be replicated2

15. Spanish Study • Cohort of 92 children • Exposed to high levels of DDE • Had lower social, mental and psychomotor development (assessed using Griffiths Scales of Infant Development and BSID-II)2

16. Mexican Study • DDE exposure in utero • Study found a decrease in psychomotor development using BSID-II at 3, 6 and 12 months2

17. Common theme • The common result from the CHAMACOS, Spanish, and Mexican studies suggests that DDE may have a negative effect on psychomotor development in infants less that 12 months of age • Only the North Carolina cohort had a positive association with decreased mental development at 6 months of age2

18. How Bad can Pesticide Exposure Be? • First, we need to determine what the “environment” in relation to pregnancy • One known example of a hazardous environmental toxin is tobacco smoke • The neonatal “environment” can include nutrition, adequacy of prenatal care, smoking, alcohol use, maternal age and socioeconomic conditions • Two or more of these factors might be related or synergistic3

19. Physical Environmental • A mother’s physical environmental is what most of us are familiar with • Air, water, food, soil and a number of consumer products • A mother’s placenta is thought of to protect a fetus against any toxins encountered, however some cases have shown the placenta to actually magnify hazardous maternal exposures3 Santa Ana Wildlife Reserve

20. Physical Environmental • For some persistent and bioaccumulative exposures (i.e. organochlorine pesticides), fetal exposure can occur as a result of maternal body burdens from years of preconceptional exposures • Fathers are just as accountable for exposures since their preconceptional exposures contribute to the risk through a mutagenic mechanism involving the sperm3

21. Neurodevelopmental Effects • Not specifically targeting pesticide exposure, environmental contaminants have been known to have adverse effects on brain and neurological development • Some developmental disabilities include ADHD, learning disabilities, autism, mental retardation and effects on the nervous system • Studies have shown that the window of susceptibility is with prenatal exposures • “Toxicological studies link both prenatal and postnatal exposure to organophosphate pesticides to neurodevelopmental effects”3

22. Limitations • This research focused on prenatal exposure and not on adolescent or adult effects

23. Future Research • Due to limited human population studies of pesticide exposure, more research is needed particularly with preconception exposures. This research should include both maternal and paternal exposures.

24. Recommendations • One recommendation for the detection of pre-exposure to the fetus • Include a questionnaire during prenatal care about possible environmental exposures for the expectant parents • This environmental assessment should be particularly conducted in agricultural communities where pesticide exposure is more prominent

25. You too can be a basketball star without excessive exposure to pesticides.

26. References • Rosas, L.G. and Eskenazi, B. (2008). Pesticides and Child Neurodevelopment. Current Opinion in Pediatrics, Vol. 20, 191-197. • Eskenazi, B., Rosas, L.G., Marks, A.R., Bradman, A., Harley, K., Holland, N., Johnson, C., Fenster, L., & Barr, D.B. (2008). Pesticide Toxicity and the Developing Brain. Basic & Clinical Pharmacology & Toxicology, Vol. 102, 228-336. • Stillerman, K.P., Mattison, D.R., Giudice, L.C., & Woodruff, T.J. (2008). Environmental Exposures and Adverse Pregnancy Outcomes: A Review of the Science. Reproductive Sciences, Vol. 15 (7), 631-650. • US Environmental Protection Agency. About pesticides. 2006. Available at: http://www.epa.gov/pesticides/about/index.htm. Accessed July 25, 2009. • American Pregnancy. Pesticides Exposure During Pregnancy. 2009. Available at: http://www.americanpregnancy.org/pregnancyhealth/pesticides.html. Accessed July 25, 2009.

27. This presentation was created in memory of Dr. Kirby “K.C.” Donnelly

28. Questions?