By Keith Mulvihill

WESTPORT, CT (Reuters Health) – Certain groups of women may be at risk for having a smaller-than-average infant if their tap water is contaminated with organic chemicals, researchers report.

In a study of women exposed to perchloroethylene (PCE), a dry-cleaning chemical, researchers found that women over 35 years of age and those with several past miscarriages were at greater risk of having a small-for-gestational age infant.

"These results suggest that some fetuses may be more vulnerable than others to chemical insult," Dr. Nancy Sonnenfeld of the University of New England in Biddeford, Maine, and colleagues report in the November issue of the American Journal of Epidemiology.

In the study, the investigators looked at data from nearly 12,000 infants born between 1968 and 1985 at the US Marines Corps Base at Camp Lejeune in North Carolina. About half of the infants in the study were born to women exposed to PCE through well water contaminated by a dry cleaner located on the base. The well was disconnected from the water system in 1985.

The researchers looked for infants who were born before 37 weeks gestation and infants small for gestational age (SGA).

"There was no difference in rates of preterm birth to women with exposure to contaminated drinking water, and rates of SGA were comparable between most exposed and non-exposed women," Dr. Sonnenfeld told Reuters Health.

"However, we also compared some potentially susceptible subgroups of women," she added.

Women exposed to contaminated drinking water and who had a history of two or more fetal losses were 2.5 times as likely to give birth to an SGA infant as women who were not exposed to contaminated drinking water and who had similar pregnancy histories.

Also, women who were 35 years or older and who were exposed to contaminated drinking water were twice as likely to give birth to an SGA infant as women of the same age who were not exposed to contaminated drinking water.

"Other researchers would have to observe similar findings before one could say that such an association was causal," she said.

PCE concentrations in the drinking water were estimated to be between 80 and 210 parts per billion (ppb), according to Dr. Sonnenfeld. The level of trichloroethylene (TCE), another organic compound found in the water, was estimated to be about 8 ppb. The US Environmental Protection Agency (EPA) maximum contaminant level for both compounds in drinking water is 5 ppb.

Notably, the EPA would issue a health advisory if PCE in drinking water reaches 500 ppb, which is higher than the levels observed in this study, she explained.

"So our results suggest the possibility that health effects may exist at a level below which a health advisory would be issued," Dr. Sonnenfeld told Reuters Health.

"Because the PCE levels are so much higher than the TCE level, I tend to think that the association is probably with PCE, but if TCE is the more potent toxicant, then one can't rule out that it is the TCE, or a mixture of both compounds that is responsible," she added.

The most common sources of high-level exposure to PCE and TCE are occupational. People working in the chemical manufacture, metal degreasing industry, in the dry cleaning industry or in scientific laboratories, or even those who live with people who work in these industries, may be exposed to higher levels of PCE.

Workers may bring the PCE home on their clothes, or expose others by exhaling their own contaminated breath, Dr. Sonnenfeld explained.

Pregnant women may be exposed to PCE in the environment, but exposure to 200 ppb PCE in drinking water is very rare. Most public drinking water supplies must be routinely tested for [chemicals], so residents can find out how much PCE and TCE are in their drinking water.

"If your drinking water is contaminated with PCE, drinking bottled water is only part of the solution," Dr. Sonnenfeld cautioned.

"Inhaling PCE is so much more [of an] efficient way to get into the body, that showering with contaminated water contributes as much to exposure as ingesting it," she added.

Am J Epidemiol 2001;154:902-908.