Pool Water Risky During Pregnancy
Swimmers are at great risk because they are exposed for long periods of time and because THMs can be absorbed through the skin and inhaled from the air around the pool, he says.
Studies have shown that a one-hour swim in a chlorinated pool could result in a THM dose 141 times higher than what you get taking a shower, or a dose 93 times higher than drinking a glass of tap water.
Further research is needed to understand the link between THMs and potential health risks, writes Nieuwenhuijsen. In the meantime, he calls for swimming pool owners to reduce THM levels "as far as possible ... while maintaining effective control against waterborne microbiological disease."
The other studies that Nieuwenhuijsen mentions have actually found lower levels of THMs than this study did, Bennett says.
Also, all studies of THMs have been done in Europe, he says. "We don't know whether they chlorinate the same as we do in U.S. pools, whether they maintain pools like we do."
"I see this as more of a water quality problem than a swimming pool problem," Bennett says. "If the chemical is that bad, we need to be looking at how it got into drinking water. I would be much more concerned about that."
Pregnant lifeguards at indoor swimming pools have been known to suffer from different illnesses -- like certain lung problems -- because of the continuous exposure to chlorinated water, he tells WebMD. Whether THMs are a risk for pregnant women who are not lifeguards, "I just don't know," he says. "You can't say from this study that it is."