March 24, 1999
Exposure to organic solvents during pregnancy causes birth defects
TORONTO — Researchers at The Hospital for Sick Children (SickKids) have concluded that occupational exposure during pregnancy to organic solvents increases the chances of major birth defects. While solvents had previously been shown to cause birth defects in laboratory animals, it is the first proof that humans can be affected as well.
The study, published in the March 24 issue of The Journal of the American Medical Association, demonstrates that pregnant women exposed in their jobs to organic solvents have a 13-times greater risk of major malformations in their babies as well as increased risk for miscarriages than women not exposed to solvents.
"Previous studies, in which women were asked after giving birth about their exposure to solvents during pregnancy, showed conflicting results regarding the link between solvent exposure and birth defects," says lead author Dr. Sohail Khattak, staff physician in the Division of Clinical Pharmacology and Toxicology and department of Emergency Medicine. "This study is important because it is the first in which women were assessed after exposure to solvents and before giving birth."
Organic solvents to which women reported being exposed to included vinyl chloride, acetone, phenols and aromatic hydrocarbons. Exposure to such solvents occurs either by absorption through the skin or by inhalation. Risk is decreased if adequate safety guidelines are followed, i.e. use of gloves and fume hoods. Although organic solvents are used in household products, the low levels of exposure associated with home use are not considered dangerous.
The study, led by researchers at the Hospital’s Motherisk program, involved 250 pregnant women, half of whom had been exposed in the workplace to organic solvents. The women in the study were counselled by the Motherisk program between 1987 and 1996. Each mother who reported occupational exposure to organic solvents was paired in the study with a woman who was exposed to an agent known to not cause birth defects. Factors such as smoking, alcohol intake, age, and stage of pregnancy were taken into consideration. All exposed women worked for at least the first trimester with organic solvents.
Among those women who reported being exposed during pregnancy to solvents, the risk of having a baby with birth defects was highest among those who also reported symptoms associated with solvent exposure, such as eye irritation, respiratory irritation, headaches, and difficulty breathing.
The mothers were followed up between six and nine months after the expected delivery date. All reports of birth defects were corroborated by a written report from the physician caring for the child. Birth defects were defined as any anomaly that has an adverse effect on either the functioning or the social acceptability of the child, and included spina bifida and other neural tube defects, heart malformations, and deafness. The rate of such malformations in the normal population is between one and three per cent.
The most common occupations dominated by females with potential exposures to solvents are health care and the clothing and textile industries. The most common occupations of the women who participated in the study were factory worker, laboratory technician, professional artist/graphic designer and printing industry worker.
"Given the results of this study, I think it’s important that women who are exposed occupationally to organic solvents take appropriate safety measures to reduce their risk," says Dr. Gideon Koren, the study’s principal investigator and head of SickKids’ division of Clinical Pharmacology and Toxicology and Motherisk program, and a Professor of Paediatrics, Pharmacology, and Medicine at the U of T. "Proper ventilation and protective clothing should be worn."
This research was funded by Physician Services Inc. and The Hospital for Sick Children Foundation.|
The Hospital for Sick Children is a health care, teaching and research centre dedicated exclusively to children; affiliated with the University of Toronto.
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