Researchers are trying to tease apart why chronic stress may make some pollutants more harmful to children. Both human and animal studies suggest that it can throw key systems of the body out of whack. At a young age, it may create hormonal shifts that permanently alter the way the body responds to future stresses, including chemical exposures. It also may weaken the immune system or trigger inflammation.
“Inflammation is central to a lot of chronic diseases we worry about today,” including respiratory diseases such as asthma, Clougherty said.
In one study, young male laboratory rats exposed to chronic stress showed a rapid, shallow breathing pattern when inhaling polluted air – unlike rats exposed only to the pollution.
The researchers created a stressful environment by placing the young male rat in the home cage of an older, dominant male twice a week. The rats exposed to both pollution and stress showed higher levels of molecules associated with inflammation in their blood.
Also, in East Boston, children who were previously exposed to community violence were more likely to show signs of asthma in response to traffic-related air pollution than children not exposed to violence. “This suggests a model where stress impacts the child’s susceptibility to pollution,” said Clougherty.
In addition to asthma, this may make low-income children more predisposed to diabetes, heart disease and even dementia later in life.
Kids living with violence also may experience more wear and tear on their DNA, damage that has been linked to disease later in life, according to a Duke University study published in April.
Susceptibility starts in the womb. Exposure to stress and pollution before birth and during early childhood may be particularly harmful because “both may alter development of the brain, lungs and nervous system during these critical periods,” said Rosalind Wright.
This raises an important question: Are people protected by policies that just consider their chemical exposures without looking at their living conditions, too? Many scientists think not.
Increased risks due to social status are “a critically important but neglected area within risk assessment, and should be incorporated in the future,” Harvard epidemiologists Joel Schwartz and David Bellinger and Johns Hopkins’ Thomas Glass wrote in a 2011 report.
Schettler said “this new understanding has the potential to change the way we think about interventions for low-income children.”
Some scientists already are working on ways to intervene to protect children. Enrichment – exploring, interacting and playing – may reduce the effects of pollution.
Improving kids' lives
Tomas Guilarte, a neurotoxicologist at Columbia University in New York, showed that it was possible to reverse cognitive effects of lead poisoning in rats by improving their environment.
Rats that had been lead-poisoned during early development and had cognitive deficits as young adults were removed from their solitary laboratory cages and housed in groups of eight in enrichment cages, which included multiple levels, a running wheel and toys.
Every week Guilarte's team put new toys in the cage. “There was a constant novelty that they would explore each week,” he said.
The lead-exposed rats in the enriched cages performed equally well on learning tests as those that had never been exposed to lead, indicating that that their learning deficits had been reversed.