Young kids who were exposed to Bisphenol A (BPA) before birth are more likely than others to have a wheeze before age five, according to a new study that found no connection to BPA exposure after birth.

Many plastic and aluminum consumer products contain BPA, and most Americans have detectable BPA concentrations in their urine, the authors write. Some studies have suggested that exposure to the chemical may contribute to the development of asthma.

Animal studies are still going on to clarify the association between BPA and lung function, said lead author Dr. Adam J. Spanier of the pediatrics department at the University of Maryland School of Medicine in Baltimore.

In 2012, the U.S. Food and Drug Administration banned BPA from baby bottles, but said there was not enough evidence for a more widespread ban.

Researchers began by testing urine samples from nearly 400 expectant mothers in the Cincinnati, Ohio area at 16 and 26 weeks into their pregnancies.

After the children were born, the researchers asked parents every six months for the next five years if the child had wheezing in his or her chest, and at ages four and five tested how much air the children could exhale during a forced breath at age.

Researchers also collected urine samples from the children annually.

The higher the BPA concentration in the mother’s urine during pregnancy, the lower the child’s lung function tended to be at age four, the researchers found. There was no association with lung function at age five.

For wheezing, the mother’s BPA concentrations at 16 weeks’ gestation was linked to the child’s risk of persistent wheeze.

The level of BPA in the children’s urine was not related to their own wheeze or lung capacity.

The results suggest a relationship between the exposure to BPA during early pregnancy and the likelihood of developing early wheeze, said Dr. Randall M. Goldblum, director of the Child Health Research Center Lab and Children’s Asthma Program at the University of Texas Medical Branch in Galveston.

He was not involved in the new study.

“It is difficult to say if this is the cause, because the development of asthma is complex and includes genetic predisposition as well as environmental exposures like the one documented,” he told Reuters Health by email.

If children get over their early wheeze by age five there is a good chance they will not have it again later in life, he noted.

“Some of the children will have asthma and they will continue to have wheezing episodes,” Goldblum’s colleague Dr. Terumi Midoro-Horiuti added.

While not all children who wheeze before age five go on to develop asthma or long term lung problems, the results demonstrate that the children with higher prenatal BPA exposure were more likely to be in the category of wheeze that persists, he told Reuters Health by email.

“I would advise pregnant women (and women of child bearing age) to avoid BPA sources such as canned foods,” Spanier said. “Unfortunately, the actions we take as consumers are limited, and ultimately the resolution might be at a regulatory level to help minimize our exposures.”