The first study to examine the link between thyroid development/function and phthalate exposure in children has just been published, and the results are quite concerning.
Measures of five phthalates and two thyroid hormones were collected from 229 women during pregnancy and 229 children at age 3 enrolled in the Mothers and Newborns Study at the Columbia Center for Children’s Environmental Health.
In girls, lower levels of the active thyroid hormone free thyroxin (FT4) were associated with metabolites of mono-n-butyl phthalate (MnBP), mono isobutyl phthalate (MiBP), monobenzyl phthalate (MBzP), and monoethyl phthalate (MEP).
Previous Mailman School studies have found links between prenatal exposure to phthalates and risk for lower IQ at age 7, childhood asthma, and mental and motor development problems in preschool children.
“The thyroid acts as the master controller of brain development,” says senior author Pam Factor-Litvak, professor of Epidemiology at the Mailman School. “Thyroid hormones set the schedule, and if the timing is out of synch, there may be later consequences in the brain. The thyroid disruptions we see in this study, although they fall within the normal range, could explain some of the cognitive problems we see in children exposed to phthalates and we are currently investigating that. As we know from lead, even small exposures can make a big difference.”
Thyroid hormone disruptions are more common in females, and the study noted that maternal thyroid function could affect fetal thyroid development. Families with young children at home are encouraged to avoid products with phthalates such as nail polish, vinyl flooring, and some shampoos.