BPA may increase asthma risk in kids, but tough to avoid

By Deborah Kotz, Globe Staff

Once again, the infamous chemical bisphenol A (BPA) has been linked to an increased risk of a health problem: this time asthma in kids. Excess exposure to BPA, which interferes with the body’s production of certain hormones, has already been linked to increased obesity risks in kids as well as a heightened likelihood of heart disease, diabetes, and kidney disease later in life. It’s been banned from baby bottles and removed from the lining of infant formula cans, but is still used in other hard plastics and to coat metal cans.

The new research, like dozens of previous studies, measured BPA levels in urine and compared those with rates of a particular illness -- in this case, asthma. The study, published Friday in the Journal of Allergy and Clinical Immunology, found a 40 percent increased risk of asthma in inner city children with the highest BPA levels at 3, 5, and 7 years of age. About 1 in 4 of the children in the study were diagnosed with asthma.

The increased risk was modest but consistent with previous studies linking high BPA levels in pregnant women’s urine with their baby’s risk of developing asthma later on, said study leader Dr. Kathleen Donohue, an allergist and immunologist at the Columbia University School of Physicians and Surgeons. Oddly, the current study didn’t find that prenatal BPA exposure affected a child’s later asthma risk, which Donohue called an “unexpected” finding.

The study doesn’t prove exposure to BPA causes asthma risk to rise. While the study took into account certain factors known to affect asthma risk, such as exposure to cigarette smoke, a mother’s history of asthma, and ethnicity, it didn’t control for poor dietary habits and childhood obesity, which may also play a role in asthma risk. For example, children who eat a lot of canned foods -- which often contain added sugars and excess sodium -- may have higher BPA levels as a result but they may also have a higher body weight and be in poorer health overall than those who eat fewer processed foods.

But Donohue said “it’s unlikely that anything else would explain our results” and that animal experiments where everything besides BPA exposure was controlled have yielded similar findings concerning asthma risks.

For this reason, parents may want to take certain measures to limit their child’s exposure to BPA in foods. The National Institute of Environmental Health Sciences has a list of tips on its website to reduce BPA such as:

-- Don’t microwave polycarbonate plastic food containers because polycarbonate may break down at high temperatures, causing BPA to leach into foods.

-- Avoid foods packaged in containers marked with recycle codes 3 or 7, which may be made with BPA.

-- Reduce your use of canned foods.

-- When possible, opt for glass, porcelain or stainless steel containers, particularly for hot food or liquids.

These tips sound sensible, but do they really work to reduce BPA levels in the body?

“That’s a challenge to determine,” Donohue told me. But she e-mailed me a study published on Thursday that addressed this very question. University of Washington researchers recruited 10 families to test whether certain interventions could reduce BPA levels in their urine over a five-day period.

What they found was that families that avoided foods packaged in cans and plastic containers and were provided with meal replacements experienced a dramatic rise in their BPA levels -- because of unexpectedly high levels of BPA in the milk and dried spices they were consuming. Those that simply followed written recommendations like those I listed above wound up with no change in their BPA levels.

“It may be difficult to develop effective interventions that are feasible in the general population,” the researchers concluded, and government regulation of the chemical may be warranted to lower exposure from foods.