Chemical Exposure Linked to Attention Deficit Disorder in ChildrenChildren exposed in the womb to chemicals in cosmetics and fragrances are more likely to develop behavioral problems commonly found in children with attention deficit disorders, according to a study of New York City school-age children published Thursday.
Scientists at Mount Sinai School of Medicine reported that mothers who had high levels of phthalates during their pregnancies were more likely to have children with poorer scores in the areas of attention, aggression and conduct.
Children were 2.5 times more likely to have attention problems that were “clinically significant” if their mothers were among those highest exposed to phthalates, the study found. The types of behavior that increased are found in children with Attention Deficit Hyperactivity Disorder and other so-called disruptive behavior disorders.
“More phthalates equaled more behavioral problems,” Stephanie Engel, a Mount Sinai associate professor of preventive medicine and lead author of the study, said in an interview Thursday. “For every increase of exposure, we saw an increase in frequency and severity of the symptoms.”
The connection was only detected for the types of phthalates used in perfumes, shampoos, nail polishes, lotions, deodorants, hair sprays and other personal care products. No behavioral effects were found for the phthalates used in vinyl toys and other soft plastics.
A federal law that went into effect a year ago bans phthalates in children’s vinyl toys and other products. But there are no U.S. restrictions on phthalates in cosmetics and other personal care items. They are, however, banned in cosmetics sold in Europe. Manufacturers of the products maintain that the chemicals are safe after being widely used for about 50 years.
Scientists said the study has uncovered a new problem that could be related to phthalates - effects on a child’s developing brain. Until now, most research has focused on their potential to block male hormones and feminize boys or contribute to male reproductive problems.
“Clearly environmental toxicants play a role in child neurodevelopment, and phthalates, in particular, have been understudied in this area,” Engel said.
Dr. Philip Landrigan, a pediatrician at Mount Sinai and director of the Children's Environmental Health Center, called it “a new area of concern” about phthalates.
“Clearly it needs to be replicated, as does any study that breaks new ground, but the study itself is very well done and very credible,” he said.
The research involved 188 children between the ages of 4 and 9 who were born between 1998 and 2002, according to the study published online in the journal Environmental Health Perspectives. Most were from East Harlem or the Upper East Side of Manhattan, and three-quarters of them were low-income.
The children’s scores were based on the answers that their mothers provided to standardized questions commonly used by psychiatrists and other clinicians to help diagnose attention deficit disorders. The mothers responded to 130 questions designed to detect problematic behaviors on a 4-point scale ranging from “never” to “almost always" and to 86 questions on another test designed to measure cognitive function, such as memory.
Some effects were stronger in boys than girls, but the associations to the chemicals were still considered significant in the girls, Engel said.
The researchers did not use doctors or other clinicians to evaluate the children. Instead, the findings were based on the mothers’ evaluations.
"A parent's report about a child's behavior is certainly subjective,” Engel said. But she added that mothers have been found to be very accurate in assessing poor conduct, aggression and attention problems.
The mothers were tested for phthalates during pregnancy, the most sensitive time for a child’s brain development. In a study published last year, Korean researchers linked childhood exposure to phthalates to ADHD.
Shanna Swan, a University of Rochester epidemiologist whose research linked phthalates with feminized genitalia in baby boys, called phthalates a “complicated picture” for scientists to unravel because there are many different compounds and so many potential effects to look for. But she said she found it “very interesting” that Engel and her team found “so many negative associations” for the phthalates with low molecular weights – the ones used in personal care products.
Swan was surprised that most of the effects were correlated with a phthalate metabolite, called MMP, that is found in the lowest concentrations in people.
“It is not a metabolite usually thought of as toxic,” said Swan, director of the Center for Reproductive Epidemiology at the University of Rochester School of Medicine and Dentistry.
The researchers said they do not know how prenatal exposure to phthalates may lead to behavioral problems. But they theorize that it may be because the chemicals disrupt thyroid hormones, which are critical to an infant’s brain development.
In April, the Mount Sinai team reported effects in the same group of children when they were newborns. The girls - but not the boys - with high exposure to phthalates had differences in alertness and orientation, two indicators of neurodevelopmental effects in infants, according to that study published in the journal Neurotoxicology.
The new study raises the question of whether phthalates and other hormone-disrupting chemicals could be playing a role in the increasing rate of attention deficit disorders diagnosed in children. Phthalates have been around for about 50 years, and it is unknown whether people’s exposure has increased.
“The percentage of kids diagnosed with behavioral problems has increased over time and it’s not clear why,” Engel said. “It would be a stretch to attribute it all to endocrine disruptors. There are probably multiple different causes.”
Nearly every human tested has traces of phthalates in his or her body, and women are most highly exposed.
“There is sufficient evidence to be concerned about phthalates, and it’s prudent to reduce exposure as much as possible,” Engel said. “But they are so ubiquitous right now it’s hard to eliminate exposure without regulatory action.”
Engel said people should “press legislators” to restrict phthalates in adult, as well as children's, personal care products.
Fetuses are “uniquely vulnerable, particularly for endocrine disruptors,” she said. “But we are very concerned about the problem of post-natal exposure as well. The kids continue to be exposed as they grow up.”
Consumers who want to learn more about the ingredients of their brands of cosmetics can use a database compiled by the Environmental Working Group at http://www.cosmeticsdatabase.com/index.php. However, manufacturers don't always list phthalates on their labels.
Phthalates are solvents that are often used in cosmetics because they help retain fragrances and help lotions penetrate the skin. Many nail polish manufacturers have already eliminated phthalates, which had been commonly used to make the polish flexible and durable.
The principal author of the study was Mary Wolff, director of Mount Sinai’s Center for Environmental Health and Disease Prevention Research. The team also included two researchers from the U.S. Centers for Disease Control and Prevention and a Cornell University scientist.