Polluted Drinking Water Linked to Low Birth Weight
By Keith Mulvihill
NEW YORK (Reuters Health) - Certain groups of women may be at risk for having a smaller-than-average size baby if their tap water is contaminated with organic chemicals, researchers report.
In a study of women exposed to PCE (perchloroethylene), 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 when exposed to the chemical.
"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 that were preterm--born before 37 weeks gestation--and infants who were small for gestational age (SGA). Such infants are carried to term (about 40 weeks) but tend to be smaller than other babies due to a number of factors.
Both SGA and preterm infants are at risk for poor health outcomes, although they are different types of health risks to the infant, Sonnenfeld noted in an interview with Reuters Health.
In general, there were no differences in the babies born to women who drank the contaminated water and those who did not.
"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," Sonnenfeld told Reuters Health.
"However, we also compared some potentially susceptible subgroups of women," she added.
Women with a history of two or more fetal losses, who had contaminated drinking water, were 2.5 times as likely to give birth to an SGA infant as women with similar pregnancy histories whose water was not contaminated.
Also, women who were 35 years or older and had contaminated drinking water were twice as likely to give birth to an SGA infant as women of the same age who did not have contaminated drinking water.
"Other researchers would have to observe similar findings before one could say that such an association was causal," she said. In other words, the study could not conclusively prove that the PCE was the cause of the lower birth weights seen in the study.
The PCE concentrations in the drinking water were estimated to be between 80 and 210 parts per billion (ppb), according to 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. So PCE levels were between 16 and 40 times the EPA standard, while TCE levels were around this level.
Notably, the level in drinking water at which EPA would issue a health advisory for PCE in drinking water is 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," 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 living with people who work in these industries may be exposed to higher levels of PCE.
This is because the workers may bring the PCE home on their clothes, or expose others by exhaling their own contaminated breath, Sonnenfeld explained.
Pregnant women may be exposed to PCE in the environment, but exposures 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," 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.
SOURCE: American Journal of Epidemiology 2001;154:902-908.