Serum dioxin concentrations and time to pregnancy.

Area of Science:

• Environmental Health
• Reproductive Epidemiology
• Toxicology

Background:

• Industrial pollution, specifically dioxins like 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), is suspected to contribute to declining fertility rates and regional variations in time to pregnancy (TTP) in industrialized nations.
• The 1976 Seveso, Italy explosion led to the highest known residential TCDD exposure, providing a unique cohort for health studies.

Purpose of the Study:

• To investigate the association between serum 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) levels and fertility outcomes in women exposed after the Seveso explosion.
• To quantify the impact of TCDD exposure on time to pregnancy (TTP) and infertility.

Main Methods:

• A retrospective cohort study (Seveso Women's Health Study) of 981 participants, focusing on 472 women who attempted pregnancy post-explosion.
• Serum TCDD levels were measured and extrapolated to the time of conception attempt.
• Fecundability was modeled using discrete-time Cox proportional hazards regression, and infertility was modeled using logistic regression.

Main Results:

• A tenfold increase in serum TCDD was associated with a 25% increase in time to pregnancy (fecundability odds ratio = 0.75).
• A tenfold increase in serum TCDD approximately doubled the odds of infertility (odds ratio = 1.9).
• Sensitivity analyses confirmed the robustness of these findings.

Conclusions:

• A clear dose-response relationship was observed between individual serum TCDD levels and increased time to pregnancy and infertility.
• These findings suggest potential adverse implications of TCDD exposure for reproductive health in industrialized populations.