Preterm birth attributable to exposure to chemicals used in plastic materials: a global estimate

Phthalates, widely used as plasticizers, have been associated with adverse pregnancy outcomes, including preterm birth (PTB). This analysis quantifies the global burden of PTB associated with exposure to di (2-ethylhexyl) phthalate (DEHP) and diisononyl phthalate (DINP).

A disease burden model was constructed using 2018 exposure estimates from available population-level biomonitoring surveys and meta-analyses in regions lacking such surveys. Hazard ratios (HRs) for PTB associated with phthalate exposure were derived from a previous cohort study and applied to regional exposure distributions, and a search from 2016 to 2026 was completed to identify uncertainty intervals for effect estimates. PTB-attributable outcome estimates were obtained from the Institute for Health Metrics and Evaluation's. Phthalate-associated PTB outcomes were calculated using a population attributable fraction approach.

In 2018, 1.97 million DEHP-attributable PTBs (8.74% of global PTBs) were estimated, alongside 74,000 deaths, 6.69 million years of life lost (YLLs) and 1.22 million years of life lived with disability (YLDs). 1.93 million of these incident PTBs, 72,500 deaths, 6.56 million YLLs, and 1.20 million YLDs could be linked to plastics. The highest absolute burden was estimated in the Middle East and South Asia, representing over 54% of estimated attributable PTBs, followed by Africa at 26%. Attributable morbidity and mortality trends differed in accordance with underlying regional patterns of burden. Estimates were similar for DiNP (64,000 deaths, 1.88 million PTB cases, 5.77 YLLs, 1.35 YLDs, and PAF of 8.32%). To account for uncertainties in extrapolating effect estimates from the US, effect estimates from four previous global meta-analyses were also used to calculate uncertainty intervals. Uncertainty intervals revealed as low as 4 times lower estimates for DEHP, and 10 times lower DiNP estimates, highlighting the need for further investigation to refine DiNP associated morbidity and mortality.

This model presents the first global estimate of the PTB burden linked to exposure to certain phthalates. Burden was estimated to be disproportionate in South Asia, the Middle East, and Africa. Implementing regulatory measures to limit exposure to phthalates as a class could help reduce the global PTB burden, particularly in and areas with high PTB risk, limited regulations, and growing plastics industries.

Funding was provided by Beyond Petrochemicals and National Institutes of Health grant number: P2CES033423.