Authors
Eskenazi B, Mocorelli P, Warner M, Chee W, Gerthoux PM, Samuels S, Needham LL, Patterson DG.

Title:
Maternal serum dioxin levels and birth outcomes in women of Seveso, Italy

Source:
Environmental Health Perspectives 60(7):947-953.2003.

Summary:
Chlorinated dioxins, furans, and some polychlorinated biphenyls encompass a group of chemicals referred to as dioxins. These chemicals are not produced intentionally and they have no known use. However, numerous animal studies have reported that exposure to low levels of dioxins result in adverse health effects. In particular, 2,3,7,8-tetratchlorodibenzo-p-dioxin (2,3,7,8-TCDD), the most toxic compound in the group, has been associated with endocrine disruption, reproductive damage, and developmental defects in animals. It has been hypothesized that TCDD may affect development by crossing the placenta thereby modulating the stimulatory effect of epidermal growth factor. In addition, TCDD has been shown to induce DNA damage in fetal and placental tissues. However, limited evidence exists with respect to the effects of maternal exposure to TCDD and pregnancy outcomes in humans.

In 1976, an explosion occurred in a TCP (2,4,5-trichlorophenol) plant near Seveso, Italy. A toxic cloud containing 30 kg of TCDD was released into the environment contaminating a densely populated area. Twenty years after the disaster, Eskenazi et al. initiated a historical cohort study to determine the relationship between maternal serum TCDD levels and the risk of spontaneous abortion (SAB), congenital disorders and abnormalities, low birth weight, and shortened gestational age. The contaminated area was divided into two exposure zones based on TCDD measurements in surface soil; zone A represented the most heavily contaminated area and zone B the next heaviest contaminated area. Portions of blood serum samples that were collected from residents soon after the explosion for immediate health assessment were used in the present study for TCDD measurement analysis. In addition, information related to personal, work, and medical history was gathered during an interview performed by a nurse blinded to the details of the woman's residence zone and TCDD levels.

An association between TCDD and adverse pregnancy outcomes was not observed in the present study. These results differ from those of previous studies that have reported increased rates of fetal loss and low birth weight in rodents and monkeys. However, a limited number of studies have documented the exact make-up and levels of dioxin exposure among the studied populations. Therefore, the differences in study results may be explained by the different mixtures of dioxins, furans, and PCBs to which individual populations were exposed. In addition, since the youngest women at follow-up were the most heavily exposed and were less likely to have had a post-explosion pregnancy, the possibility that an association between TCDD and birth outcomes exists, remains. One limitation to this study was the inability to confirm all pregnancy outcomes with medical records; all reports were provided by the mothers themselves. Thus, the possibility that some women may have under- or over-reported certain conditions is plausible.