Vehicle exhaust linked to children's ADHD

Study finds womb exposure led to much higher risk of attention problems by age 9.

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      The following article was originally published by Environmental Health News

      New York City children exposed in the womb to high levels of pollutants in vehicle exhaust had a five times higher risk of attention problems at age nine, according to research by Columbia University scientists published Wednesday.

      “Our research suggests that environmental factors may be contributing to attention problems in a significant way,” said Frederica Perera, an environmental-health scientist at Columbia’s Mailman School of Public Health who was the study's lead author.

      The study adds to earlier evidence that mothers' exposures to polycyclic aromatic hydrocarbons (PAHs), which are emitted by the burning of fossil fuels and other organic materials, are linked to children's behavioural problems associated with attention deficit hyperactivity disorder (ADHD).

      Ten percent of kids diagnosed with ADHD

      About one in 10 U.S. kids is diagnosed with ADHD, according to the Centers for Disease Control and Prevention. Children with ADHD are at greater risk of poor academic performance, risky behaviors, and lower earnings in adulthood, the researchers wrote.

      “Air pollution has been linked to adverse effects on attention span, behavior, and cognitive functioning in research from around the globe. There is little question that air pollutants may pose a variety of potential health risks to children of all ages, possibly beginning in the womb,” said Dr. Andrew Adesman, chief of developmental and behavioral pediatrics at Steven & Alexandra Cohen Children’s Medical Center of New York. He did not participate in the new study.

      In addition to PAHs, a variety of other pollutants have been linked to ADHD or ADHD-like behaviors. Included are organophosphate pesticidespolychlorinated biphenyls(PCBs), phthalates, and perfluorinated compoundsPrevious studies by the Columbia University researchers linked prenatal PAHs to reduced IQsanxiety and depression, attention problems, and developmental delays in children between the ages of three and seven.

      Mothers with high PAH levels most at risk

      For the new study, the researchers followed the children of 233 African-American and Dominican women in New York City. They measured the amount of benzo[a]pyrene bound to DNA—a biological marker for PAHs—in the mothers' blood at the time of birth. Forty-two percent had detectable levels in their blood.

      When the children were about nine years old, parents filled out a questionnaire commonly used to screen for ADHD behavior problems. The researchers found that children whose mothers had the highest amounts of the PAH at the time of birth were five times more likely to show more behaviors associated with inattention than children whose mothers had the lowest levels. They were three times more likely to exhibit more total behaviors (inattention, hyperactivity and impulsivity) associated with ADHD.

      The levels of PAHs were “quite typical of other urban areas that have been monitored,” Perera said.

      It’s not known how many of the children had an ADHD diagnosis.

      Behaviours not solid ADHD diagnosis

      The questionnaires indicated some behaviours involved in ADHD, but they do not mean that the child necessarily has ADHD, said David Bellinger, a Harvard professor of neurology who studies effects of environmental exposures on kids’ developing brains.

      “The diagnosis of ADHD involves much more extensive information-gathering and ruling out of other diagnoses,” he said.

      The researchers were the first to measure PAHs directly in people’s bodies rather than using air pollution levels as a proxy for their exposures.

      “Having these individual measures of exposure reinforces the possibility that there is a causal connection,” said Jonathan Chevrier, an environmental-health scientist at McGill University in Montreal.

      The scientists tested the children’s urine samples to distinguish prenatal from postnatal air-pollution exposures. They also controlled for other factors in the child’s genetics and early life experiences, such as tobacco smoke and stress, that could contribute to ADHD-like symptoms.

      Lead and mercury exposure not tested

      The researchers, however, did not account for children’s exposures to lead or mercury, two contaminants that also have been linked to attention problems. “It’s possible that exposure to one of these substances is highly correlated with PAH exposure,” Bellinger said.

      It’s not clear how PAHs might affect developing brains. “We know that these chemicals damage DNA. They also mimic natural hormones and may interfere with placental growth,” which could deplete oxygen and nutrients for the developing fetus, Perera said.

      Since the Columbia team started tracking air pollution levels in 1998, PAHs have declined, which Perera attributes to stricter anti-idling laws and phaseout of older diesel buses in New York City.

      “Air pollution knows no boundaries. These involuntary exposures are largely the provenance of policy makers,” Perera said.




      Dec 9, 2014 at 9:11am

      The great irony here is that so much automobile exhaust is contributed by parents who routinely drive their children to school. Drive by any school in Vancouver's west side (especially the private schools) and you will see (and be caught in) a major traffic jam of massive SUVs idling in wait of their precious cargo. At present, the problem is so great that a through-driver must go out of their way to avoid the twice-daily congestion that has traffic blocked for a good 3/4 hour. Yet, with the exception of HASTE BC, little attention is paid to this massive cluster-f*#k of carbon and congestion.


      Dec 9, 2014 at 9:29am

      Anyone who is not mentally deficient is able to conclude that smoke is not good for cognition. For how much longer is our method of governance going to be using "science" top argue conclusions that people who are not mentally challenged understand intuitively? Is it my duty, as an intelligent pereson, who has a good idea of who to be ecologically responsible, to dedicate my life to arguing "scientifically" with mentally challenged people? Anyone who isn't convinced by the smog residue in his nostrils but is convinced by a table of numbers is a seriously deformed organism.


      Dec 9, 2014 at 4:09pm

      It's well established that the bulk of pollution is caused by mature, responsible, working adults. Thankfully they're now spending a portion of their idiotic working hours trying to fix the problems they created by instituting work in the first place. God bless them!