A new study published in December 2014 is the first of its kind to evaluate the effect of prenatal phthalate exposure and children’s IQ at the age of seven.

Previous studies had found preschoolers intelligence were negatively affected with prenatal exposure to phthalates.  This is the first study to find the negative results of prenatal chemical exposure on intelligence to persist once children have reached school age.

Because phthalate exposures are ubiquitous and concentrations seen here within the range previously observed among general populations, results are of public health significance.

What are phthalates?

Phthalates are plasticizers, a chemical group used to make plastic more flexible and durable.

According to the Centers for Disease Control (CDC):

They are used in hundreds of products, such as vinyl flooring, adhesives, detergents, lubricating oils, automotive plastics, plastic clothes (raincoats), and personal-care products (soaps, shampoos, hair sprays, and nail polishes).

As the authors of “Persistent Associations between Maternal Prenatal Exposure to Phthalates on Child IQ at Age 7 Years” wrote, exposure to phthalates is “ubiquitous”. It is hard to avoid. We have all been exposed.  We exposed all of our babies in utero.

Exposure in personal care products is of great concern, as the phthalates can be directly absorbed into the body through the skin.

In this study, researchers followed 328 mothers and children growing up in the inner-city.  In late pregnancy, the mother’s phthalate levels were measured in their urine.  Specifically, levels of  “di-n-butyl phthalate (DnBP), butylbenzyl phthalate (BBzP), di-isobutyl phthalate (DiBP), di-2-ethylhexyl phthalate and diethyl phthalate” were tested.  Seven years later, these children were evaluated using the The Wechsler Intelligence Scale for Children to determine intelligent quotient. This is the same test used by school when evaluating students with special needs.  Researchers found:

Significant inverse associations were also seen between maternal prenatal metabolite concentrations of DnBP and DiBP and child processing speed, perceptual reasoning and working memory; DiBP and child verbal comprehension; and BBzP and child perceptual reasoning.

The higher the concentration of these phthalates in the mother’s urine, the lower the scores were for children in these areas of the Weschler.  The test is designed not to measure what a child already knows.  According to Purdue University, “Wechsler defined intelligence as an individual’s ability to adapt and constructively solve problems in the environment.”

The specific areas of intelligence prenatal phthalate exposure negatively affects school age children’s intelligence are:

1. Perceptual reasoning is “children’s ability to examine a problem, draw upon visual-motor and visual-spatial skills, organize their thoughts, create solutions, and then test them. It can also tap preferences for visual information, comfort with novel and unexpected situations, or a preference to learn by doing.”
2. Working memory is “children’s ability to memorize new information, hold it in short-term memory, concentrate, and manipulate that information to produce some result or reasoning processes. It is important in higher-order thinking, learning, and achievement. It can tap concentration, planning ability, cognitive flexibility, and sequencing skill, but is sensitive to anxiety too. It is an important component of learning and achievement, and ability to work effectively with ideas as they are presented in classroom situations.”
3. Processing speed is “children’s abilities to focus attention and quickly scan, discriminate between, and sequentially order visual information. It requires persistence and planning ability, but is sensitive to motivation, difficulty working under a time pressure, and motor coordination too.”
4. Verbal comprehension is “children’s ability to listen to a question, draw upon learned information from both formal and informal education, reason through an answer, and express their thoughts aloud. It can tap preferences for verbal information, a difficulty with novel and unexpected situations, or a desire for more time to process information rather than decide ‘on the spot.'”

Every expecting parent wants the most for their child. Most do not know how the chemicals they are exposed to are harming their children’s physical and mental health.  The results of this study is consistent to what researchers found previously when comparing prenatal exposure to phthalates and intelligence of preschoolers.  In fact, researchers found post natal exposure may play a role in perceptual motor and working memory for school age children when they compared the results between the two studies.

Phthalates have been linked to a host of human health problems.  From juvenile high blood pressure, weakened bones, preterm birth, to lowered intelligence, this chemical group should be avoided. It has been banned in many products, but as the researchers stated, it poses a significant public health risk.   Advising pregnant women to avoid  products, such as nail polish, that contain phthalates should be part of prenatal education.

To answer the question in our title, “Will using nail polish while pregnant make your child stupid?” it depends.  There are safer nail polishes out there that do not contain phthalates, but even if you keep your nails bare, you may still be exposed though other beauty and plastic products.