Study: Chlorine in pools linked to asthma

September 14, 2009 The study found that teenagers who spent more than 1,000 hours swimming in chlorinated pools, either indoors or out, had more than eight times the risk of having asthma than teens who primarily swam in pools using a copper-silver disinfecting method.

The risk of allergies also increased significantly when teens spent more than 100 hours swimming in chlorinated polls. In fact, the risk of hay fever and other allergies more than doubled with significant chlorinated pool exposure.

The study appears in Pediatrics.