Association of Prenatal Phthalate Exposure With Language Development in Early Childhood
Authors: Carl-Gustaf Bornehag, PhD; Christian Lindh, PhD; Abraham Reichenberg, PhD; Sverre Wikström, PhD; Maria Unenge Hallerback, PhD; Sarah F. Evans, PhD; Sheela Sathyanarayana, MD; Emily S. Barrett, PhD; Ruby H. N. Nguyen, PhD; Nicole R. Bush, PhD; Shanna H. Swan, PhD
Phthalates are a group of chemicals used to make plastics more flexible and harder to break, increase the longevity and projection of scent in fragrances, and extend the life of nail polish, among other uses. Phthalates are used in many products including vinyl flooring, adhesives, detergents, clothing (e.g., raincoats), food packaging, personal care products (e.g., soaps, shampoos, hair sprays, nail polish), inflatable toys, medical tubing, and some children’s toys .
Children are often exposed to phthalates by eating and drinking foods and liquids that have been in contact with containers made with phthalates. Exposure can also occur from breathing in air that contains phthalate vapors or dust with phthalate particles. Children’s risk of exposures are increased because proportionately, they eat and drink more and breathe in more air than adults, and they also exhibit behaviors such as crawling and frequent hand-to-mouth actions . When phthalates are in a person’s body, they are converted into breakdown products (metabolites) that then pass through and can be measured in the urine to determine a person’s exposure level. Centers for Disease Control and Prevention (CDC) researchers determined that there is widespread human exposure to phthalates in the U.S. Adult women tend to have higher levels of phthalates in their bodies than men because of their increased use of cosmetics, perfumes, lotions, and other personal care products . This is of concern, especially with regard to women of childbearing age. Research indicates that maternal exposure to phthalates can expose the unborn child, and that phthalates can also pass into breast milk and present another source of exposure to a newborn. In addition, children were found to have the highest exposures to phthalates of all groups monitored by CDC .
The human health effects of low levels of phthalate exposure are unknown; however, animal studies indicate that low levels of exposure correlate with a disruption in hormonal functions and may have an adverse effect on development ,. Exposure has been linked to neurodevelopmental disorders in children, including autism, attention-deficit hyperactivity disorder, and other cognitive issues. Neurodevelopmental disorders in children have increased over the past several decades in the U.S. CDC monitoring estimates that 1 in 68 children have autism, and the National Center for Learning Disabilities states that 1 in 5 children in the U.S. have learning and attention issues.
To examine the relationship between prenatal phthalate exposure and language development of children who were involved in two pregnancy studies, the Swedish Environmental Longitudinal Mother and Child, Asthma and Allergy (SELMA) and The Infant Development and the Environment Study (TIDES).
Female participants enrolled in SELMA or TIDES in the first three months of their pregnancy and were included in this study about phthalates if both full data on pregnancy phthalate levels and on child language delay were collected.
Phthalate exposure was assessed from several urine metabolites.
The mothers in this study completed a language development sheet with the number of words their children could understand or use at 30 months (SELMA) and 37 months old (TIDES). After the language development sheet was completed, the responses were put into categories of children who could understand or speak fewer than 25 words, 25 to 50 words, and more than 50 words. If the child could not understand or speak more than 50 words they were classified as having a language delay.
Of the children analyzed in both the SELMA and the TIDES populations, 10% had language delay. There were higher rates of language delay in boys than in girls. Two phthalates, dibutyl phthalate (DBP) and butyl benzyl phthalate (BBP), were found to be significantly associated with language delay for both SELMA and TIDES. When mothers were exposed to double the amount of either of these phthalates, there was a 25% to 40% increase in the chance of language delay in children in the SELMA study. When there is a doubling of pregnancy exposure to another type of phthalate, monoethyl phthalate, there is a 15% increase in the chance of language delay according to the SELMA study. The TIDES study did not find this same association.
Exposure to two types of phthalates, DBP and BBP, was found to be associated with language delay in children in both the SELMA and TIDES studies. These findings--considered along with the potential widespread prenatal exposure to phthalates in the U.S. and the critical importance of language development for the trajectory of a child’s life--may warrant a precautionary approach towards regulation of phthalates in order to best protect children’s health and development.
Federal policy and regulation focused on phthalates is limited, and center around limiting concentrations of a few compounds in very select consumer products, as well as limiting the release of some compounds into US waters and ambient air and exposure limits for workplace settings.
The U.S. Consumer Product Safety Commission (CPSC) permanently banned the use of eight phthalates (including DBP and BBP) in children’s toys and child care products. The term “ban” means that any children’s toys and child care products should contain no more than a 0.1% concentration of any of the eight phthalates. A children’s toy is defined as a toy produced for children 12 years and younger, and in this case specifically targets toys that can be easily lifted and put into the child’s mouth. Child care products are any items that are not toys that can be used to comfort a child, specifically products used for feeding, sleeping or teething in children under the age of three. For example, an infant’s pajamas are not supposed to have any of the eight banned phthalate compounds, but that infant’s shoes may have them.
Historically, phthalate levels have been regulated in sources of drinking water through the Clean Water Act. This law requires that U.S. waterbodies are regulated by the Environmental Protection Agency (EPA) to limit pollution by potential contaminants, including both BBP and DBP. However, there are no National Primary Drinking Water Regulations for DBP and BBP under the Safe Drinking Water Act.
Three phthalates, including DBP, are listed as hazardous air pollutants, and EPA regulates their emissions under the Clean Air Act. DBP can also contaminate indoor air and is of particular concern in workplace settings, especially those in which women of childbearing age are often employed, such as nail salons. Four phthalates, including DBP, are regulated under the Occupational Safety and Health Administration with a permissible air exposure limit of 5 mg/m3 (b)1, but there is no mention of BBP.
Phthalates are also a common product in cosmetics, which are primarily used by women and therefore pose the threat of being passed in utero when a woman is pregnant. The U.S. Food and Drug Administration (FDA) regulates the development and distribution of cosmetics in the U.S.; however, FDA does not currently regulate phthalates in cosmetic products before they are placed on the market.
Food and drink contaminated with phthalates is a major source of human exposure. Yet FDA considers BDP and BBP to be “indirect additives of food contact substances”, and thus currently allows their use in food packaging products,.
Women of reproductive age and children could experience increased cumulative exposures to DBP or BBP due to identified gaps in current phthalate regulations. When developing or updating regulations, consideration of the following are paramount to better safeguarding children’s health and development:
- the latest scientific findings, such as this highlighted study
- multiple routes of exposure, including prenatal exposures,
- children’s exposures to other environmental hazards, including stress and other factors associated with poverty, and their nutritional and overall health status
- children’s unique vulnerabilities (increased risk of exposure, bodies still developing)
It is also critical that workplace exposure standards and other regulatory standards are reviewed critically, and informed by the most recent science (such as this study), on a regular and frequent basis.
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