Children who start swimming before the age of 2 may be at increased risk of a common infant lung infection, and possibly asthma and respiratory allergies later in life, a new study suggests.

The findings, reported in the European Respiratory Journal, add to evidence that exposure to chlorinated pools may affect children’s respiratory health — particularly if they have a family history of asthma or respiratory allergies like hay fever.

Experts have suspected that the air quality around pools, particularly indoor ones, is to blame. When the chlorine used to disinfect pools combines with swimmers’ sweat, saliva or urine, irritating chlorine byproducts are formed, and over time these chemicals may damage the airways.

In the new study, Belgian researchers found that infant swimming — whether in indoor or outdoor pools — was linked to a heightened risk of bronchiolitis.