Pesticide Exposure and Neurodevelopment in the Fetus

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Pesticide Exposure and Neurodevelopment in the
Fetus

• Marcel Elizondo
• July 2009 STEER Student
• UTHSCSA-Harlingen

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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 animals4

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Looking at mosquito larvae at the City of
Brownsville lab
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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

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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

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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 dichlorodiphenyltri
  chloroethane (DDT), which was subsequently banned
  in the US in the 70s
• Currently, replacement pesticides for DDT are
  insecticides such as organophosphates.1

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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

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Inhibiting the Acetylcholinesterase
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Inhibiting the Acetylcholinesterase
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Organophosphate Detection

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

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

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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

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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

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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

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Mexican Study

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

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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

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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

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Physical Environmental

• A mothers physical environmental is what most of
  us are familiar with
• Air, water, food, soil and a number of consumer
  products
• A mothers 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
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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

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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 effects3

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Limitations

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

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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.

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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

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You too can be a basketball star without
excessive exposure to pesticides.
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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/p
  esticides.html. Accessed July 25, 2009.

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This presentation was created in memory of Dr.
Kirby K.C. Donnelly
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Questions?