A report published in the open-access journal PLoS Medicine finds that maternal exposure to dangerous toxins damages thyroid function of babies. Andrea Baccarelli (University of Milan) and colleagues from the United States and Italy studied a 1976 accident at a chemical factory in Seveso, Italy that exposed several residents of the town to the most dangerous type of dioxin. The researchers found that newborn babies born to mothers who lived in contaminated areas at the time of the accident are over six times more likely to present damaged thyroid function compared to babies born to mothers in non-contaminated areas.
Byproducts of waste incineration, dioxins are toxic chemicals that linger in the environment and build-up people. The toxin released in Seveso – 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) – is the most dangerous type of dioxin, and it was declared a class-1 carcinogen by the World Health Organization in 1997 was declared a class-1 carcinogen by the World Health Organization. Previous studies of animals and people have demonstrated that an offspring’s thyroid gland can be damaged after maternal exposure to dioxins.
This recent study analyzed the continuing effects of TCCD on children born around Seveso, Italy, and the researchers focused on three groups of child-bearing women. The sample included 1,772 women who were living in Zone A – the most contaminated area in Seveso, very near to the factory at the time of the accident – or in Zone B – a nearby area, less but still highly contaminated. These women were compared to 1,772 women from the surrounding non-contaminated area, called Zone Reference. Between 1994 and 2005, these women had 1,014 babies. Baccarelli and colleagues analyzed blood samples to measure the amount of thyroid secreting hormone (TSH) in the children. It is known that high blood TSH levels are correlated with a failing thyroid, and this could lead to body and brain damage to the developing baby.
Children born decades after the accident are still experiencing the harmful effects of the Seveso disaster, according to the researchers. A baby born in Zone A – the most highly TCCD-contaminated area at the time of the accident – was found to be 6.6 times more likely to have a high blood TSH level than a baby born in the Zone Reference, or non-contaminated area. The babies born in Zone B, a less contaminated area than Zone A, had moderate TSH blood levels. Using a subsample of 51 pairs of mothers and children, the researchers compared dioxin levels at the time of birth. They found that high blood TSH levels in babies were more likely to be from mothers who had high levels of dioxins in their blood.
The authors conclude: “Our findings from the Seveso population indicate that maternal exposure to persistent environmental contaminants such as TCDD produces effects on neonatal thyroid function that may occur far apart in time from the initial exposure. To clarify the clinical significance of our findings, further investigation on developmental outcomes after maternal dioxin exposure is warranted.”
Neonatal thyroid function in Seveso 25 years after maternal exposure to dioxin
Baccarelli A, Giacomini SM, Corbetta C, Landi MT, Bonzini M, et al
PLoS Medicine (2008). 5(7): e161.
doi:10.1371/journal.pmed.
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PLoS Medicine is an open access, freely available international medical journal. It publishes original research that enhances our understanding of human health and disease, together with commentary and analysis of important global health issues. For more information, visit http://www.plosmedicine.org
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Written by: Peter M Crosta