Toxic Tuesdays

CHEJ highlights several toxic chemicals and the communities fighting to keep their citizens safe from harm.

Transgenerational Toxicity

While getting cancer, liver disease or central nervous system damage is often associated with exposure to toxic chemicals, one of the most sensitive targets of toxic chemicals is the reproductive system. This has long been recognized for over 50 years (123). In recent years however, research has shown that toxic chemicals can not only directly affect the reproductive system of both women and men, but that these effects can be passed on to the next generation and can even skip a generation. The impact of toxic chemicals on children with no direct exposure to these chemicals is known as a transgenerational effect.

A recent review paper reported that research on chemical toxicity, early life nutrition, smoking and radiation found evidence of harm even in offspring with no direct exposure to specific contaminants. This paper pointed to groundbreaking research at Washington State University that helped establish the principle of transgenerational toxicity by showing that the effects of toxic chemicals can extend even to the third generation of offspring. Other review papers have found a growing body of evidence from epidemiological studies that suggests that environmental exposures early in development have a role in susceptibility to disease in later life and that some of these effects seem to be passed on through subsequent generations (67).

One important study that made this clear was a follow-up study on the residents of Love Canal in Niagara Falls, NY. This study, conducted by the New York State Department of Health (DOH), found that maternal exposure to chemicals from the Love Canal landfill was associated with an elevated risk of bearing a child with an adverse reproductive outcome. The researchers found that women who lived in the designated emergency zone while pregnant prior to the time of evacuation had a higher risk of having a preterm birth compared to women from other regions of the state. This effect was statistically significant.

There was also a greater than expected frequency of congenital malformations among Love Canal boys born from 1983 to 1996. These birth defects occurred in infants born to mothers who previously lived at Love Canal. The rate of these birth defects was about 50% higher than in boys born to mothers who lived in upstate NY. In addition, the ratio of male to female births was lower for children conceived at Love Canal. Lastly, women exposed as children had an increased risk of giving birth to a low weight baby.

These findings are consistent with the initial findings at Love Canal that led to the evacuation of the community in 1978 and 1980. The initial findings identified lower birth weight and increased congenital birth defects in infants, but were limited in defining the risk of adverse pregnancy outcomes because of small sample sizes.

This study is extraordinary because it looked at the reproductive outcomes of women after their exposure had stopped compared to other studies which typically evaluate health effects at the time when exposures were ongoing. In some cases, exposures to Love Canal chemicals occurred only when the women were children! These remarkable findings point out the subtle impact of exposure to toxic chemicals. They are a red flag for health concerns – especially for women of child bearing age – at other contaminated sites across the country. This study also highlights how little we really know about low level exposures to toxic chemicals.

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