Solvents linked to diminished IQ

Danger: A study suggests that children of women exposed at work to certain organic chemicals may suffer significant damage.

Medicine & Science

October 25, 2004|By David Kohn | David Kohn,SUN STAFF

Children of women exposed to common organic solvents during pregnancy have significantly lower scores on a wide range of cognitive, motor and behavioral tests, according to a new study.

The average IQ of the exposed group was eight points lower than a group of comparable unexposed children - a gap one expert described as "huge."

The study, which appeared in this month's issue of The Archives of Pediatric and Adolescent Medicine, focused solely on solvent exposure at work.

"This has tremendous implications for the female work force," said University of Toronto psychologist Maru Barrera, one of the authors.

The researchers recommend that pregnant women limit exposure to the chemicals, widely used in many industries, including manufacturing plants, hair and nail salons and medical laboratories. "Women who are pregnant should not be exposed to organic solvents during the duration of their pregnancy," Barrera said.

Organic solvents are a huge group of disparate chemicals. Toluene, for example, is an ingredient in polyurethane, as well as in paints, glues and gasoline. Hexane is used in pesticides, wood stains and printing.

The compounds also are found in a variety of home products, but the researchers said exposure at home is likely to be sporadic and much more limited than at work.

"The study is very interesting and potentially important," said Herbert Needleman, a University of Pittsburgh pediatrician and psychiatrist who has shown that prenatal and childhood lead exposure can permanently damage the brain.

Needleman said that the IQ decrease was potentially significant. For most children, the loss of eight IQ points might not make an obvious difference. But in previous studies on the effects of lead, Needleman found that a four-point drop in average IQ creates a fourfold rise in the number of children with severe mental deficits.

"If you move that curve eight points down, you greatly increase the number" of such children, he said.

Exposure during pregnancy

Researchers examined the children of 32 women who were exposed to organic solvents during pregnancy. They included factory workers, lab technicians, embalmers and a science teacher. They worked with solvents that including hexane, trichloroethylene, acetone, toluene and phenol.

The scientists compared their children to 32 offspring of unexposed mothers. Both groups, ages 3 to 9 years old, took a range of cognitive and motor tests. Parents also answered a questionnaire about their children's behavior.

The exposed children had lower scores in almost all the tests. Though not enormous, the differences were significant, researchers said. The largest gap was in verbal ability, but the exposed children also performed worse on tests of memory, dexterity, visual acuity and color perception. Youngsters in the solvent group also displayed greater hyperactivity and had more trouble paying attention. But Gideon Koren, a University of Toronto pediatrician and co-author, said the data did not show a link to attention deficit disorder.

In an e-mail response to questions about the study, a spokesman for the American Chemistry Council, the industry's trade group, wrote: "Protecting the health and well-being of children is a fundamental value the chemical industry shares with society. ... The [study's] authors themselves acknowledge that this study is not a `refined risk assessment' and conclude that `further evaluation' is necessary."

Several experts expressed similar caution. "We need a larger study to confirm these findings," said Tina Lawson, an epidemiologist at the National Institute for Occupational Safety and Health. Lawson is working on a national study of 9,000 women and children to examine the relationship between birth defects and a wide range of chemicals, including solvents.

Researchers have long known that high doses of some solvents can cause cancer and neurological ills in adults. Animal studies have shown that solvents can cause birth defects, but there is little research involving human fetuses and children.

Different thresholds

In recent years, scientists have realized that children are often much more vulnerable to the effects of chemicals than adults. But most workplace regulations set chemical safety standards by hazard to adults.

Koren said the finding showed that, as a class, solvents are more hazardous than previously understood: "Safety levels for adults are not necessarily safety levels for the developing brain."

While no one knows exactly how many women are exposed to organic solvents at work, Koren estimates that the number is in the millions. Because the study subjects worked with a variety of solvents, and exposures weren't measured, researchers said there's no way to know whether some solvents are more hazardous than others.

The chemicals bind to oils, so they're used for cleaning everything from industrial machinery to clothing. All organic solvents are volatile, which means molecules constantly escape into the air.

The volatility allows the chemicals to infiltrate the body with relative ease, primarily through the mouth and lungs, as well as by contact with the skin.

Solvents are also ingredients in many household products, including cleaners, polishers and deodorizers. But Koren said he was less worried about the risks of home use because such exposures do not typically occur repeatedly over days or months.

Some scientists said the study underscored the particular vulnerability of fetuses and children. Solvents might be the latest widely disseminated chemicals - a list that includes lead and mercury, among others - that turn out to be especially dangerous during development.

Said Needleman: "We don't know how smart our children could be if we didn't poison them."

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