Phthalates Exposure and Fine Motor Functions

Phthalates are a group of high production chemicals that are often used to make plastics more flexible and to enhance odors in personal care products. They can be found in multiple household items including food containers, furniture, flooring, plastic shower curtains and plastic toys, as well as in personal care products and cosmetics.  Recent studies focus on the associations between exposure to these chemicals during the in utero and early childhood periods and cognitive and behavior problems.   In this study, the authors examined associations between exposure to several phthalates before birth and fine motor skills, or small movements like picking up objects, in 11-year old children.  Data were from the Mother and Child Study, a prospective cohort study conducted in the Columbia Center for Children’s Environmental Health. This study recruited 18–35 year old pregnant women of African-American or Dominican ethnicity, who had resided in northern Manhattan or the South Bronx for at least 12 months and gave birth between the years 1999 and 2006Urinary concentrations of seven phthalate metabolites were measured in maternal spot urine samples collected from 209 mothers during the third trimester of pregnancy.  Motor functions were evaluated using standardized motor skills proficiency tests in the offspring of these women at age 11.

Using a method to evaluate prenatal exposure to mixtures of phthalate, rather than single chemicals, higher concentrations of phthalates were associated with lower scores on fine motor scores among girls, but not boys.  Further, no associations were found in either boys or girls with gross-motor functions at age 11.

The authors suggest several biological mechanisms for this association, including altered levels of thyroid hormones due to phthalates. Prenatal thyroid hormones are critical for brain development, especially in the cerebellum, which partially accounts for coordination and fine-motor movements.  Phthalates also disrupt neurons associated with the development of motor skills, which may be another explanation for the results found in this study.  In summary, the study found that prenatal exposure to phthalates was associated with decreased fine motor functions in 11-year old girls.

Daniel S, Balalian AA, Whyatt RM, Liu X, Rauh V, Herbstman J, Factor-Litvak P.  Perinatal phthalates exposure decreases fine-motor functions in 11-year old girls: Results from weighted Quantile sum regression. Environ Int. 2020 Mar; 136:105424.