"The dose required for neurotoxicity in the fetus is going to be less than that of the adult due to the difference in pharmacokinetics of the fetus. For every dose of toxicant that the adult is exposed to which does not produce any toxic effect, that same dose may be toxic already to the growing fetus due to its difference in pharmacokinetic capabilities."

    So pointed out Dr. Enrique Ostrea Jr., director of the Detroit, Michigan-based Hutzel's University service nurseries and professor at Wayne State University's department of pediatrics.

    More importantly, the fetus is vulnerable to neurotoxicants-natural or man-made substances that can alter the normal activity of the nervous system-since the fetus's brain is undergoing rapid growth and development, stressed Ostrea who, in 2002 was awarded two simultaneous multimillion-dollar grants from the United States National Institutes of Health and the Environmental Protection Agency to study fetal exposure to environmental toxins in the Philippines.

    By the time the fetus is born the proliferation and migration of neurons, synaptogenesis, apoptosis, and gliogenesis are already pretty much in place-a lot of this neuronal growth and development have already occurred by the time of birth. By the time the infant is about two years old, it shall have potentially grown in terms of its brain growth to the fullest.

    "Pesticides or neurotoxicants will affect brain growth and development at these various stages of neuronal development. The effects of toxic agents are not just on one specific process of neuronal development but on multiple steps or stages. That therefore explains the vulnerability of the fetal brain to these neurotoxicants," he noted.

    Compounds like ethanol-plain grog or liquor-methyl mercury, caffeine, and polychlorinated biphenyl (PCB) can cause adverse effects on neuronal migration, that is the migration of neurons from the central canal to the periphery. Infants who have been exposed to ethanol in utero have some degree of mental retardation-the neurons don't migrate normally; they clump together, and that predisposes to mental retardation. Methyl mercury wreaks the same havoc.

    In Taiwan, an industrial accident nine years ago that spilled toxic PCB into cooking oil has spawned an epidemic of birth defects-dark colored heads, faces, and genitals; and abnormal nails that were dark and often ridged, split, or folded. The PCB-affected children also tended to have swollen gums and teeth that chipped readily. They were shorter and lighter on average than children who were not exposed and had developmental delays as measured by standard psychological tests.

    In Iraq, wheat and barley seeds treated with methyl mercury were unwittingly processed into flour and made into bread by peasants-over 400 died and pregnant mothers who survived the poisoning gave birth to severely mentally retarded children.

    Ostrea also cited a 1991 study conducted among children in the Yaqui valley villages and nearby foothills in Obregon, Mexico. Valley farmers apply pesticides 45 times per crop cycle, grow one or two crops per year while local families use household bug sprays daily. Hill dwellers, on the other hand, swat indoor bugs and avoid using agricultural chemicals to control garden pests.

    Researchers asked four- and five-year-olds to jump up and down as long as possible, catch balls, drop raisins into bottle caps, perform memory drills, and draw pictures of people. Outcome: valley children demonstrated significantly less stamina, gross and fine eye-hand coordination, 30-minute recall, and drawing ability than preschoolers from the foothills communities.

    "It is evident from these studies that developing children who are exposed to pesticides could be affected by neurotoxicants in their environment," he remarked.

    In an ongoing study that recruited at the Bulacan Provincial Hospital 936 pregnant women at midgestation, Ostrea and his research team look for traces of pesticides in the matrices they have collected which are "maternal hair, maternal blood, infant hair, infant cord blood, and meconium."

    Ropaxil (an organophosphate that can affect functioning of the nervous system), a major component in the antiinsect spray largely used in households, was detected in maternal hair and blood and infant meconium.

    A pyrethroid called bioalethrin-found in katol or mosquito coil- turned up in maternal hair. Small amounts of the pesticide were also found in the meconium.

    The team found out that propoxur and cyfluthrin are the common pesticides that turn up in either maternal hair or meconium-"the best matrix to analyze for fetal exposure to environmental toxicants as it is the dumping ground for all the compounds that the fetus was exposed to throughout gestation."

    Explained Ostrea: "Cyfluthrin belongs to a class of natural insecticides called pyrethrins churned out by certain plants. Plant marigolds in your garden and you will have less mosquitoes in your house-because marigolds emit pyrethrins and these are contact poisons that can quickly penetrate the insect's nervous system."

    Cyfluthrin merely knocks out insects. It's the propoxur that delivers the coup de grace.

    "In terms of cord-blood chromosomal abnormality, we saw an increased frequency of t8 to 21 translocation, which is a biomarker of leukemia in cord blood of infants exposed to propaxur. Remember propaxur is the major component of Baygon. The presence of this marker of leukemia is 10 percent on the infants who were not exposed, compared to 20 percent in the infants who were exposed, about a two-fold increase," he related.

    "We found that at the age of two years on follow-up, infants who were exposed to propaxur-there was a negative correlation of the concentration of propaxur in meconium to motor development, to social development and to general caution," he added.

    But there are other adverse effects that turned up, among them, "chromosomal and hearing problems, and abnormal neurobe-havioral development in infants at two years who have been prenatally exposed to propaxur and pyrethroids.

    "Further follow-up of infants at school age-which is four to six years-is necessary to test the children with the use of more extensive and sensitive measures designed to [gauge] the developing skills of children at this critical [stage]," he concluded.

    The late well-respected anthropologist Loren C. Eiseley once asserted that "man is an expression of his landscape." He may be right. And we may be horrified to face such human beings who have been expressed in a landscape awash with pesticides-over 10,000 of them-and chemicals that slowly brings ruin to man, woman, and child. M

 

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