Bornehag CG, Lindh C, Reichenberg A, Wikström S, Unenge Hallerback M, Evans
SF, Sathyanarayana S, Barrett ES, Nguyen RHN, Bush NR, Swan SH. Association of
Prenatal Phthalate Exposure With Language Development in Early Childhood. JAMA
Pediatr. 2018 Oct 29. doi: 10.1001/jamapediatrics.2018.3115. [Epub ahead of
Prenatal exposure to phthalates has been associated with neurodevelopmental outcomes, but little is known about the association with language development.
To examine the association of prenatal phthalate exposure with language development in children in 2 population-based pregnancy cohort studies.
DESIGN, SETTING, AND PARTICIPANTS:
Data for this study were obtained from the Swedish Environmental Longitudinal Mother and Child, Asthma and Allergy (SELMA) study conducted in prenatal clinics throughout Värmland county in Sweden and The Infant Development and the Environment Study (TIDES) conducted in 4 academic centers in the United States. Participants recruited into both studies were women in their first trimester of pregnancy who had literacy in Swedish (SELMA) or English or Spanish (TIDES). This study included mothers and their children from both the SELMA study (n = 963) and TIDES (n = 370) who had complete data on prenatal urinary phthalate metabolite levels, language delay, and modeled covariables. For SELMA, the data were collected from November 1, 2007, to June 30, 2013, and data analysis was conducted from November 1, 2016, to June 30, 2018. For TIDES, data collection began January 1, 2010, and ended March 29, 2016, and data analysis was performed from September 15, 2016, to June 30, 2018.
MAIN OUTCOMES AND MEASURES:
Mothers completed a language development questionnaire that asked the number of words their children could understand or use at a median of 30 months of age (SELMA) and 37 months of age (TIDES). The responses were categorized as fewer than 25, 25 to 50, and more than 50 words, with 50 words or fewer classified as language delay.
In the SELMA study, 963 mothers, 455 (47.2%) girls, and 508 [52.8%] boys were included. In TIDES, 370 mothers, 185 (50.0%) girls, and 185 (50.0%) boys were included in this analysis. The prevalence of language delay was 10.0% in both SELMA (96 reported) and TIDES (37 reported), with higher rates of delay in boys than girls (SELMA: 69 [13.5%] vs 27 [6.0%]; TIDES: 12 [12.4%] vs 14 [7.6%]). In crude analyses, the metabolite levels of dibutyl phthalate and butyl benzyl phthalate were statistically significantly associated with language delay in both cohorts. In adjusted analyses, a doubling of prenatal exposure of dibutyl phthalate and butyl benzyl phthalate metabolites increased the odds ratio (OR) for language delay by approximately 25% to 40%, with statistically significant results in the SELMA study (dibutyl phthalate OR, 1.29 [95% CI, 1.03-1.63; P = .03]; butyl benzyl phthalate OR, 1.26 [95% CI, 1.07-1.49; P = .003]). A doubling of prenatal monoethyl phthalate exposure was associated with an approximately 15% increase in the OR for language delay in the SELMA study (OR, 1.14; 95% CI, 1.00-1.31; P = .05), but no such association was found in TIDES (OR, 0.98; 95% CI, 0.79-1.23).
CONCLUSIONS AND RELEVANCE:
In findings from this study, prenatal exposure to dibutyl phthalate and butyl benzyl phthalate was statistically significantly associated with language delay in children in both the SELMA study and TIDES. These findings, along with the prevalence of prenatal exposure to phthalates, the importance of language development, and the inconsistent results from a 2017 Danish study, suggest that the association of phthalates with language delay may warrant further examination.
Early prenatal exposure to phthalates — the synthetic chemicals commonly found in household items and personal care products — has been tied to language delays in children, new research shows.
In the first study of its kind, the collaboration between investigators from the Icahn School of Medicine at Mount Sinai, New York City, and Karlstad University, Sweden, showed that the risk for language delay was as much as 30% greater in children whose mothers were exposed to twice the levels of dibutyl phthalate and butyl benzyl phthalate, two chemicals commonly found in such everyday items as cosmetics, plastic toys, and food.
"The bottom line here is that the phthalates that a mother is exposed to in early pregnancy can affect the development of the brain in her children, particularly in this area of language development," principal investigator Shanna Swan, PhD, professor of environmental and public health at the Icahn School of Medicine at Mount Sinai, told Medscape Medical News…
Previous research in both animals and humans has demonstrated that phthalates are endocrine disruptors with antiandrogenic properties. Indeed, prenatal phthalate exposure has been associated with male genital defects. Moreover, studies found inverse associations between phthalate metabolite level in prenatal urine and subsequent child neurodevelopment, behavioral outcomes, mental and psychomotor development, and neurologic status.
The researchers used data from two independent pregnancy cohort studies for the analysis — the Swedish Environmental Longitudinal, Mother and Child, Asthma and Allergy study (SELMA; 963 pregnant women and their children) and the Infant Development and Environment Study (TIDES; 370 women and their children). The latter study was conducted in the United States…
After adjusting for potential confounders, a doubling of prenatal exposure to these two metabolites increased the odds ratio of language delay by 25% to 40%. These adjusted findings were significant in the Swedish study but not in the American study. The researchers attribute this difference to the smaller sample size in the US study…
Commenting on the findings for Medscape Medical News, Susan Schantz, PhD, professor of toxicology and neuroscience at the University of Illinois in Urbana, who was not involved in the study, said the findings are very much needed.
"We did a review a couple of years back looking at environmental chemicals and language development, and I was shocked to see how little research there was on this really important aspect of neurodevelopment," said Schantz.
"Phthalates are present in many different consumer products," Schantz added. "So it's very hard to avoid exposure. I think studies like this are important because we need to start phasing phthalates out of products and find better, less toxic solutions."
"I don't know what the answer is," Swan concluded, "but I know we'd be doing pregnant women and their children a service if we could keep some of these chemicals out of their bodies."