Men and women exposed to chemicals in the workplace may be increasing their odds of having an infant with a birth defect, two new studies suggest.
In the first report, researchers linked birth defects to fathers who have certain jobs, including mathematicians, physicists, computer scientists, artists, photographers, food-service workers, landscapers, hairdressers and make-up artists, the researchers report.
"Our study provides additional evidence of exposures or risk factors among men that can increase the risk of birth defects in their offspring," said lead researcher Tania Desrosiers, from the Center for Birth Defects Research and Prevention at the University of North Carolina, in Chapel Hill. "In general, most of the associations we observed between occupations and birth defects were modest."
How dad's job can affect foetus
For example, children of photographers and photo-processing workers were about three times as likely to have congenital glaucoma as offspring of men who worked in other occupations, Desrosiers said.
"Although this increased risk may sound alarming, primary congenital glaucoma in the general population is actually quite rare, with approximately one in 10 000 infants affected," she said.
The report was published online in the journal Occupational and Environmental Medicine.
For the study, Desrosiers' team used data from the US National Birth Defects Prevention Study to identify almost 1 000 fathers who had children with a birth defect. They compared these with more than 4 000 fathers whose infant didn't have any birth defects.
The researchers found that about one-third of the jobs they looked at were not associated with birth defects. These occupations included architects, designers, health-care workers, dentists, firefighters, fishermen, car-assembly workers, entertainers, foundry workers, stonemasons, glass blowers, painters, train drivers, soldiers and commercial divers.
The most 'dangerous' jobs
Some jobs appeared to be linked to specific birth defects: artists (problems with the mouth, eyes and ears, gut, limbs, and heart); photographers and photo processors (cataracts, glaucoma, insufficient eye tissue); drivers (glaucoma and insufficient eye tissue); and landscapers and gardeners (gut abnormalities).
"We don't advise men to change jobs, but it may be prudent to avoid unnecessary exposure to chemicals and other potentially dangerous agents in the workplace," Desrosiers said. "One way to reduce exposure is to wear personal protective equipment."
What causes this association isn't clear. More research is needed to identify whether specific exposures, such as exposure to organic solvents or pesticides, for example, might account for the observed relationship between particular jobs and birth defects, she said.
How this might happen is unclear, said Dr Michael Katz, interim medical director of the March of Dimes. "Is it the exposure of the father that might affect sperm?" he said. "Is it exposure to the mother from clothing brought into the house? Is it something they transmit to their partners?"
"I find it extremely hard to figure out why being a mathematician would have any sort of influence, because mostly what they do is think," he said.
These papers will evoke other, more comprehensive studies, Katz said. "What these researchers did was review correlations, which are insufficient in a rational world to prompt doing something," he said.
Solvents tied to birth defects
In the second report, also published in Occupational and Environmental Medicine, researchers found exposure to organic solvents at work seem to be associated with several types of heart defects at birth.
"We are not ready to say solvents cause heart defects, but there seems to be some suggestion that occupational exposure to solvents is a risk factor for some heart defects," said researcher Suzanne Gilboa, an epidemiologist with the US Centers for Disease Control and Prevention.
This is not a definitive finding, and needs to be validated in other studies, she added.
Exposure to these solvents could increase the risk of having a baby with a heart defect by 60% to 70%, Gilboa said. The absolute risk, however, is low.
"The overall risk of having baby with a heart defect is one in 1 000 or less, so exposure might mean going from one case to two cases," she said.
Organic solvents are used for dissolving or dispersing things like fats, oils and waxes, and in chemical manufacturing. They are found in paints, varnishes, adhesives, degreasing/cleaning agents, dyes, polymers, plastic, synthetic textiles, printing inks and agricultural products, according to the report.
Most of these solvents are highly volatile and can be breathed in or absorbed through the skin or mouth.
How the study was done
Gilboa's team collected data on 5 000 women exposed to these solvents in their workplace early in pregnancy. They looked for associations between 15 types of congenital heart defects and exposure to these chemicals.
The researchers found that 4% of women whose babies did not have birth defects - and 5% of those who did -- were exposed to organic solvents at the time they were trying to conceive or early in pregnancy. When they accounted for these findings using other published material, they increased to 8% and 10%, respectively.
"These findings are encouraging," Katz said. The weakness of both of these studies, however, is that the work experience is self-reported, so it is subject to faulty memory of what the actual exposure was at the critical time, he said.
Another caveat about the two studies: while they uncovered an association between parents' occupations and birth defects, they did not prove a cause-and-effect relationship.
Complications in pregnancy
For more on birth defects, visit the March of Dimes.
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