Exposure to phthalates, chemicals commonly used in plastics, is estimated to be a leading cause of premature birth in one in 10 babies, according to a new study led by researchers at NYU Grossman School of Medicine. For about a century, a group of chemicals called phthalates have been used in a variety of household products, primarily as a way to soften plastics. This chemical has become so common that almost everyone in the Western world probably has some trace amount of phthalates in their system.
In recent years, scientists have begun to link phthalate exposure to adverse health outcomes, from finding links to childhood cancer risks to reduced fertility. A 2021 survey estimated that 100,000 premature deaths in the United States may be related to phthalate exposure.
The new study, published in the journal The Lancet Planetary Health, builds on a decade of research pointing to a link between premature birth and phthalates. More than 5,000 mothers participated in the survey, with urine samples collected at three points during pregnancy. The study examined levels of 20 different metabolites.
Unlike previous studies examining this association, the new study looked at a number of different phthalates in the most diverse group of mothers ever investigated. This allowed researchers to discover new differences between different types of phthalates.
Studies have found that the most commonly used phthalate, DEHP (di-2-ethylhexyl phthalate), is closely linked to premature birth. Mothers with the highest levels of DEHP in their urine were about 50 percent more likely to give birth prematurely compared with mothers with the lowest levels.
Perhaps most concerning, though, studies have found that several chemicals recently used to replace DEHP are associated with higher rates of preterm birth. Researchers believe that the rise in preterm birth rates in the United States over the past decade is related to a shift away from DEHP and toward alternatives based on concerns about its safety.
"The association pattern suggests that DEHP substitution is responsible for the increase in preterm births," the researchers wrote in the study. "This finding is concerning because DiNP, DiDP, and diisononyl 1,2-cyclohexanedicarboxylate are replacing DEHP in food packaging."
Leonardo Trasande, the study's lead author, said the findings should send a strong appeal to regulators. His research shows that there are safer production alternatives to phthalates, but companies tend to shy away from these alternatives because of their higher costs. As a result, companies end up tweaking compounds slightly to circumvent regulations for problem chemicals.
"These results demonstrate the need to regulate phthalates as a category rather than trying to tackle one problem at a time," Trasande said. "Otherwise, in a few years, investigators are likely to find the same findings on the next group of chemicals used as alternatives."
The new research is published in the journal The Lancet Planetary Health.