Most babies born prematurely and one-third of full-term infants are exposed to chemicals found in vinyl “at a potentially harmful level,” according to new research in Finland.

The study of 125 babies from the day they were born to 14 months old is the first comprehensive examination of infants’ exposure to several phthalates. The chemicals, considered hormone disruptors, have been linked to health effects in animal tests and some human studies, including altered male genitalia, attention and learning problems and asthma.

The sources of the phthalates in the babies are unknown. But some researchers suspect that they came from hospital equipment or household materials.

“We were really surprised to see that metabolites of several phthalates were elevated in both preterm and full-term infants,” said Hanne Frederiksen, the lead study author from Copenhagen University in Denmark.

Shanna Swan, an environmental health scientist at Mount Sinai Hospital in New York, said she is concerned by the findings because preterm babies already have “a whole lot stacked against them.”

“Prematurity itself is a known risk factor for neurodevelopmental impacts, so it’s particularly concerning to see preterm infants at the greatest risk and having the highest exposures,” said Swan, who was not involved with the study. Her 2005 research linked feminization of male baby genitalia to phthalates.

Eighty percent of the infants born before 37 week and 30 percent of the full-term infants had levels of four phthalate metabolites in their urine that exceeded adult guidelines, based on hormone effects, set by the European Food Safety Authority.

In animal tests, the chemicals had anti-androgenic effects on offspring, which means they blocked male hormones that guide reproductive development.

But it’s unclear what health outcomes, if any, can be attributed to high exposures to phthalates during infancy.

“We spend a lot of time focusing on the prenatal environment and the mother, but less is known about infancy. It’s a potentially important window of exposure too,” said Joe Braun, an epidemiologist at Brown University who was not involved with the study.

The researchers compared the babies’ risks to the levels that the European agency deemed safe for adults in their daily intake of food. However, infants have immature immune and metabolic systems, so they “may be more susceptible than adults,” Frederiksen said.

Previous research found that pregnant women exposed to high levels have a greater risk of having a preterm baby. That finding, combined with the new findings, may mean these babies are highly exposed before and after birth.

In the new study, at ages of one week and one month, the preterm babies had between five and 500 times higher levels of several of the chemicals (known as DEHP, BBzP and DiNP) than full-term infants. Their levels dropped after they left the hospital, which on average, was 39 days after birth. Those chemicals often are used to soften plastics. Other phthalates used in fragrances were nearly the same in the preterm and the full-term infants.

After the age of two months, the exposures evened out between the two groups, with about 30 percent of all infants exceeding the guidelines for daily intake, according to the study, which was published online in the journal Environmental Health Perspectives.

For adults, food is a major source of phthalates such as DEHP, which may be used in some food packaging or processing equipment.

In the study, however, it made no difference whether infants were breast-fed or bottle-fed, “which points to exposure sources other than diet…such as the general home environment,” the researchers wrote.

Previous studies have suggested that preterm infants may be exposed to DEHP from IV tubing and fluid bags. In 2002, the U.S. Food and Drug Administration advised hospitals to minimize use of medical equipment containing the chemical, especially for male newborns, because studies had shown effects on the male reproductive tract.

As a result, some hospitals have phased out soft plastics containing DEHP. In 2012, Kaiser Permanente, the largest managed care organization in the United States, announced it would no longer buy IV solution bags and tubing containing DEHP or polyvinyl chloride. The phthalate also has been banned in the United States in toys and other children’s products.

Chemical manufacturers have long maintained that the plasticizers are safe.

“There is no reliable evidence that any phthalate has ever caused a health problem for a human from its intended use. A vast body of scientific evidence shows that phthalates break down within minutes and are quickly eliminated from the body,” Lisa Dry, a spokesperson for the American Chemistry Council, which represents manufacturers of phthalates, said in an emailed response.

Swan said infants born today might not have the same patterns of exposure as those in the study, who were born in 2006 through 2008. Chemical formulations have changed in recent years. A study of American adults and children released earlier this year found that average exposures to DEHP decreased by 37 percent between 2001 and 2010.

This article originally ran at Environmental Health News, a news source published by Environmental Health Sciences, a nonprofit media company.