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Pesticide-Induced Diseases: Learning/Developmental Disorders

Attention Deficit Hyperactivity Disorder ● Autism ● Developmental Delays

Roughly one in six children in the U.S. has one or more developmental disabilities, ranging from a learning disability to a serious behavioral or emotional disorder. Scientists believe that the amount of toxic chemicals in the environment that cause developmental and neurological damage are contributing to the rise of physical and mental effects being found in children. Studies show children’s developing organs create “early windows of great vulnerability” during which exposure to pesticides can cause great damage. In the U.S., requirements for testing pesticides and other chemicals for potential developmental and learning disorders are minimal.

A developing brain is much more susceptible to the toxic effects of chemicals than an adult brain. During development, the brain undergoes a highly complex series of processes at different stages. Interference from toxic substances that disrupt these processes can have permanent consequences. That vulnerability extends from fetal development through infancy and childhood to adolescence. Research has shown that environmental toxicants, such as pesticides, at low levels of exposure can have subclinical effects—not clinically visible, but still important adverse effects, such as decreases in intelligence or changes in behavior.

Attention Deficit Hyperactivity Disorder (ADHD) Autism
  • The Rise in Autism and the Role of Age at Diagnosis.
    Study found that a seven- to eight-fold increase in the number children born in California with autism since 1990. These results suggest that research should shift from genetics to the host of chemicals and infectious microbes in the environment that are likely at the root of changes in the neurodevelopment of California’s children, including pesticides and household chemicals.
    [Hertz-Picciotto, I. and Delwiche, L. 2009. Epidemiology:20(1) - pp 84-90 doi: 10.1097/EDE.0b013e3181902d15]
  • Household Pesticide Use in Relation to Autism
    A population-based study looking at how genes and environmental factors interact shows that pet shampoos containing insecticides may trigger autism spectrum disorders (ASD). The study findings, presented at the International Meeting for Autism Research, show that mothers of children with an ASD are twice as likely to have used an insecticidal pet shampoo during the prenatal and/or postnatal period when compared to mothers of healthy children. The strongest association was during the second trimester of pregnancy.
    [Hertz-Picciotto, et al. Oral Presentation at the International Meeting for Autism Research (ORAL 2899). London, England, May 15, 2008)]
  • Autism: Transient in utero hypothyroxinemia related to maternal flavonoid ingestion during pregnancy and to other environmental antithyroid agents
    Author suggests that substances that interfere with thyroidal activity may produce morphological brain changes leading to autism. Environmental contaminants interfere with thyroid function including 60% of all herbicides, in particular 2,4-D, acetochlor, aminotriazole, amitrole, bromoxynil, pendamethalin, mancozeb, and thioureas. The current surge of autism could be related to transient maternal hypothyroxinemia resulting from dietary and/or environmental exposure to antithyroid agents.
    [Román, G, C. 2007. Journal of the Neurological Sciences; 262(1-2), pp 15-26]
  • Maternal Residence Near Agricultural Pesticide Applications and Autism Spectrum Disorders Among Children in the California Central Valley.
    Study shows that children born to mothers living near agricultural fields where organochlorine pesticides, specifically endosulfan and dicofol, were applied during their first trimester of pregnancy were six times more likely to have children that develop autism spectrum disorders (ASDs). compared to mothers who did not live near the fields.
    [Roberts, E, M. et al. 2007. Environ Health Perspect 115:1482-1489. doi:10.1289/ehp.10168]

Developmental Delays

  • Fetal exposure to propoxur and abnormal child neurodevelopment at 2 years of age
    Study was conducted to determine the effects of fetal exposure to propoxur and pyrethroids on child neurodevelopment at 2 years of age. Prenatal exposure to multiple pesticides was analyzed in maternal hair and blood, infant's hair, cord blood, and meconium. Infants were examined at 2 years of age and their neurodevelopment outcome was assessed by the Griffiths mental developmental scale. Exposure was highest for propoxur and grouped pyrethroids. There was a significant negative relationship between prenatal pesticide exposure to propoxur and motor development at 2 years of age after controlling for confounders. Authors conculde that at 2 years of age, prenatal exposure to propoxur is associated with poorer motor development in children.
    [Ostrea Jr, E., Reyes, A., Villanueva-Uy, E., et al. 2011. NeuroToxicology In Press ]
  • Prenatal Exposure to Organophosphates, Paraoxonase 1, and Cognitive Development in Childhood
    Researchers examine the relationship between biomarkers of organophosphate exposure, PON1, and cognitive development at ages 12 and 24 months, and 6 to 9 years in this Mount Sinai Children’s Environmental Health Study. Prenatal exposurel was associated with a decrement in mental development at 12 months among blacks and Hispanics. In later childhood, increasing pesticide metabolites were associated with decrements in perceptual reasoning, with a monotonic trend consistent with greater decrements with increasing prenatal exposure. Findings suggest that prenatal exposure to organophosphates negatively impacts cognitive development, particularly perceptual reasoning, with evidence of effects beginning at 12 months and continuing through early childhood.
    [Engel SM, Wetmur J, Chen J, Zhu C, Barr DB, Canfield RL, et al. 2011. Environ Health Perspect :-. doi:10.1289/ehp.1003183]
  • 7-Year Neurodevelopmental Scores and Prenatal Exposure to Chlorpyrifos, a Common Agricultural Pesticide
    This is a longitudinal birth cohort study of inner-city mothers and children (Columbia Center for Children’s Environmental Health) to estimate the relationship between prenatal chlorpyrifos (CPF) exposure and neurodevelopment among cohort children at age 7     years. 265 children were sampled and researchers measured prenatal CPF exposure using umbilical cord blood plasma (picograms/gram plasma), and 7-year neurodevelopment. On average, for each standard deviation increase in exposure (4.61 pg/g), Full-Scale IQ declined by 1.4%, and Working Memory declined by 2.8%. These findings are important in light of continued widespread use of CPF in agricultural settings and possible longer-term educational implications of early cognitive deficits.
    [Rauh V, Arunajadai S, Horton M, Perera F, Hoepner L, Barr DB, et al. 2011. Environ Health Perspect. doi:10.1289/ehp.1003160]
  • Prenatal Exposure to Organophosphate Pesticides and IQ in 7-Year Old Children
    Study conducted a birth-cohort study (CHAMACOS) among predominantly Latino farmworker families from an agricultural community in California and assessed exposure to OP pesticides by measuring dialkyl phosphate (DAP) metabolites in urine collected during pregnancy and from children at age 6 months and 1, 2, 3½ and 5 years. Averaged maternal DAP concentrations were associated with poorer scores for Working Memory, Processing Speed, Verbal Comprehension, Perceptual Reasoning, and Full Scale IQ. Children in the highest quintile of maternal DAP concentrations had an average deficit of 7.0 IQ-points compared with those in the lowest quintile.
    [Bouchard MF, Chevrier J et al. 2011. Environ Health Perspect :-. doi:10.1289/ehp.1003185]
  • Trends in the Prevalence of Developmental Disabilities in US Children, 1997–2008
    A new report by the American Academy of Pediatrics reveals that roughly one in six children in the U.S. have developmental disabilities, particularly those that are linked to environmental exposure, which showcases the need for stricter policies to reduce the use of pesticides and other toxic chemicals. The study is based on National Health Interview Surveys of children aged 3 to 17 years over the 12-year period of 1997-2008. Results show that boys have a higher prevalence overall and for a number of select disabilities compared with girls. Prevalence of any developmental disability increased from 12.84% to 15.04% over 12 years. Autism, attention deficit hyperactivity disorder, and other developmental delays increased, whereas hearing loss showed a significant decline. These trends were found in all of the sociodemographic subgroups, except for autism in non-Hispanic black children. Daily News
     [Boyle, C. et al 2011. American Academy of Pediatrics, (doi: 10.1542/peds.2010-2989]
  • Impact of Prenatal Exposure to Piperonyl Butoxide and Permethrin on 36-Month Neurodevelopment
    Research published February 7, 2011 in the online edition of the journal Peditatrics shows that children more highly exposed to pyrethroid insecticides and piperonyl butoxide (PBO), a synergist added to increase the potency of pyrethroids, ar    e three times as likely to have a mental delay compared to children with lower levels. The study measured exposure to pesticides using maternal and umbilical cord plasma samples and in personal air samples, collected using backpack air monitors during pregnancy. Children were then tested for cognitive and motor development (using the Bayley Scales of Infant Development) at three years of age. Children with the highest prenatal exposures scored about 4 points lower on the test. That’s about the same intelligence loss caused by lead, Philip Landrigan, MD, a pediatrics professor and environmental health expert at New York’s Mount Sinai School of Medicine, told USA Today. Pyrethroid pesticides kill bugs by “being toxic to the developing brain,” Dr. Landrigan says. The results are “very believable and should be taken seriously.”
    [Horton, et al. 2011. Pediatrics, Online February 7, 2011 (doi:10.1542/peds.2010-0133)]
  • Neurobehavioral Deficits and Increased Blood Pressure in School-Age Children Prenatally Exposed to Pesticides
    Prenatal exposure to pesticides at levels that do not cause adverse health effects in the mother can lead to delayed brain developmental in the child. A definite negative effect was found in children, whose mother had been exposed to pesticides during pregnancy. The effect was the strongest for motor coordination, spatial performance and visual memory. Children were 1.5 to 2 years behind in the development of these functions, which is a very marked shift at age 6-to-8 years, where brain development is particularly rapid. The researchers also found increased blood pressure, likely a result of adverse effect on brain nuclei responsible for regulation of cardiovascular functions.
    [Harari, R. et al. 2010. Environ Health Perspect, 118:890–896]
  • Chlorpyrifos Exposure and Urban Residential Environment Characteristics as Determinants of Early Childhood Neurodevelopment
    Study found that high concentrations of chlorpyrifos in umbilical cord blood (>6.17 pg/g) corresponds to a 6.5 point decrease in the Psychomotor Development Index, and a 3.3 point decrease in the Mental development index in 3 year olds.The study examined neighborhood characteristics such as poverty levels and dilapidated housing, factors that are also linked to lower test scores. Researchers were able to conclude that neighborhood characteristics and chlorpyrifos exposure were independently associated with children’s neurodevelopment.
    [Lovasi , G. et al. 2010. Am J Public Health. AJPH.2009.168419v1]
  • Mind, Disrupted: How Toxic Chemicals May Affect How We Think and Who We Are
    First-ever biomonitoring report identifying toxic chemical pollution in people from the learning and developmental disability community. Report examines 61 toxic chemicals present in project participants in the context of rising rates of autism, attention-deficit hyperactivity disorder, and other learning and developmental disabilities.
    [Gonzalez, S. et al. 2010. The Learning and Developmental Disabilities Initiative]
  • Prenatal Airborne Polycyclic Aromatic Hydrocarbon Exposure and Child IQ at Age 5 Years.
    A mother’s exposure to urban air pollutants known as polycyclic aromatic hydrocarbons (PAHs) can adversely affect a child’s intelligence quotient or IQ. The Study found that children exposed to high levels of PAHs in New York City had full scale and verbal IQ scores that were 4.31 and 4.67 points lower than those of less exposed children.
    [Perera, F. et al. 2009. Pediatrics, DOI: 10.1542/peds.2008-3506]
  • Prenatal Organochlorine Exposure and Measures of Behavior in Infancy Using the Neonatal Behavioral Assessment Scale (NBAS)
    Findings provide evidence for an association between low-level prenatal PCB and DDE exposures and poor attention in early infancy.
    [Sagiv SK, et al. 2008. Environ Health Perspect 116:666-673. doi:10.1289/ehp.10553]
  • Pesticide Exposure and Stunting as Independent Predictors of Neurobehavioral Deficits in Ecuadorian School Children
    Children in Ecuador whose mothers were exposed to pesticides while pregnant have diminished ability to copy geometric figures as part of a standardized Stanford-Binet test as compared to a control group, according to the epidemiological study. Adjusted regression analysis indicates that the exposed children experience a developmental delay on this aptitude of four years. The researchers also concluded that prenatal pesticide exposure may add to the already deleterious effects of malnutrition.
    [Grandjean, P. et al. 2006. Pediatrics, 117(3) pp. e546-e556]
  • Impact of Prenatal Chlorpyrifos Exposure on Neurodevelopment in the First 3 Years of Life Among Inner-City Children
    A 2006 study linked the insecticide chlorpyrifos, which is used on some fruits and vegetables, with delays in learning rates, reduced physical coordination, and behavioral problems in children.
    [Rauh, V. et al. 2006. Pediatrics, 118(6) pp. e1845-e1859 ]
  • Arrested Development: A study on the Human Health Impacts of Pesticides
    A study found a strong link between pesticide exposure and cognitive abilities among farmers' children in India. The study revealed serious mental development disorders that ranged from severely impaired analytical abilities, motor skills, concentration and memory among the children in the chemical-intensive cotton belts of India (A 2004 study reveals serious mental development disorders that range from severely impaired analytical abilities, motor skills, concentration and memory among the children in the chemical-intensive cotton belts of India.
    [Kuruganti, K. 2003. Greenpeace. Bangalore India.]
  • In Harms Way: Toxic Threats to Child Development.
    Animal studies link pesticides in the organochlorine, organophosphate (OP), and pyrethroid families to hyperactivity. OPs are also linked to developmental delays, behavioral disorders and motor dysfunction in animal studies.
    [Shettler, T., et al., 2000. Greater Boston Physicians for Social Responsibility: Cambridge, MA.]
  • An Anthropological Approach to the Evaluation of Preschool Children Exposed to Pesticides in Mexico
    In a comparative study in Mexico, children exposed to pesticides demonstrated decreases in stamina, coordination, memory, and the ability to draw familiar subjects.
    [Guillette, E., et al. 1998. Environmental Health Perspectives, 106(6):347-353.]
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