About one in every 10 U.S. children is living with asthma — that’s closing in on 7 million kids. And while we have a good handle on what triggers asthma attacks and exacerbates respiratory symptoms, exactly what causes asthma in the first place is still somewhat of a mystery. However, new research points to some possible new culprits that are difficult, if not nearly impossible, to avoid.

Those culprits are phthalates, ubiquitous chemicals found in just about everything, from food packaging to shower curtains to vinyl flooring to personal care products such as fragrances and shampoos. (Phthalates are a group of chemicals that make plastics flexible and hard to break and are also used to help cosmetic products cling to the skin.) Just this week, researchers from the Columbia Center for Children’s Environmental Health at the Mailman School of Public Health published findings that children born to mothers who experienced high levels of exposure to two particular phthalates during pregnancy had a significantly higher risk of developing asthma. Specifically, they found that high maternal exposure to butylbenzyl phthalate (BBzP) and di-n-butyl phthalate (DnBP) resulted in a 72 percent and 78 percent increase, respectively, in the risk of a child developing asthma between ages 5 and 11 years old when compared to mothers with lower levels of exposure.

“Everyone from parents to policymakers is concerned by the steep rise in the number of children who develop asthma,” Robin Whyatt, study co-author and co-deputy director of the Columbia Center for Children’s Environmental Health, said in a news release. “Our goal is to try and uncover causes of this epidemic so we can better protect young children from this debilitating condition. Our study presents evidence that these two phthalates are among a range of known risk factors for asthma.”

To conduct the study, which is the first of its kind, Whyatt and her colleagues followed a group of 300 pregnant women and their children in New York City. All of the women were either African American or Dominican. Researchers measured the exposure to four different phthalates via urine samples taken during the woman’s third trimester and when the children were ages 3, 5 and 7. To control for confounding variables, the study excluded women if they used tobacco or illicit drugs or were living with diabetes, hypertension or HIV.

Phthalates were detected in 100 percent of maternal prenatal urine samples. Among the children, 154 had a history of reporting asthma-like symptoms and 94 were diagnosed with asthma. Since pretty much everyone tests positive for phthalates exposure, researchers compared women with the highest levels to those with lower levels. They found a significant association between concentrations of BBzP and DnBP metabolites during the third trimester of pregnancy and an asthma diagnosis among children ages 5 to 11 years old. However, the researchers reported their results with caution. Authors Whyatt, Matthew Perzanowski, Allan Just, Andrew Rundle, Kathleen Donohue, Antonia Calafat, Lori Hoepner, Frederica Perera and Rachel Miller write:

These findings may imply that prenatal exposure to some phthalates has effects on transient wheeze and/or nonspecific airway hyper-responsiveness. It is possible that the respiratory consequences of prenatal exposure to phthalates mimic what has been observed following prenatal exposure to cigarette smoke, where several large cohort studies have essentially established its role in recurrent wheeze in very young children. Alternatively, prenatal phthalates exposure may induce a nonspecific airway hyper-responsiveness, manifested as report of wheeze, use of asthma medication, cough or other breathing problems, that develops into clinical asthma during childhood only in a subset of children. The development of airway hyper-responsiveness is believed to have an environmental component, and develops at a very early age. Further prospective studies are needed to resolve these important clinical questions.

On the preventive side, avoiding phthalates is quite difficult, both because the chemicals are pretty much everywhere and because they’re rarely listed as an ingredient in the products we buy. The news release announcing the study results notes that several phthalates, including BBzP and DnBP, have been banned from many children’s products, but steps haven’t been taken to warn pregnant women about the possible health risks to their fetuses. This newest study builds on the researchers’ previous findings that child and prenatal exposure to certain phthalates is associated with a higher risk of asthma-related airway inflammation and childhood eczema. Like many environmental exposure risks, limiting exposure to phthalates in an effective way will likely take action from policy-makers and regulators.

“While it is incumbent on mothers to do everything they can to protect their child, they are virtually helpless when it comes to phthalates like BBzP and DnBP that are unavoidable,” said study co-author Rachel Miller, co-deputy director of the Columbia Center for Children’s Environmental Health. “If we want to protect children, we have to protect pregnant women.”

According to the American Lung Association, asthma is the third leading cause of hospitalization among children younger than 15 years old. Every year, the chronic respiratory disease results in about $50.1 billion in direct health care costs.

To read the full study, which was published this week in Environmental Health Perspectives, click here.

Kim Krisberg is a freelance public health writer living in Austin, Texas, and has been writing about public health for more than a decade.