The Little Known Dangers of Swimming Pools


Extracts from “Is Your Water Safe” by Dr. Mercola.


If you have a swimming pool and use chlorine as a sanitizer – or if you and your family swim in a chlorinated pool regularly — you’ll want to pay particular attention to the following information.

The chlorine byproduct trihalomethanes (THMs) abound in swimming pools, forming when chlorine reacts with organic matter like skin and hair.  Pool chlorine and DPBs are rapidly absorbed through your skin and can disrupt your biochemistry. In fact, you can absorb more chlorine and DBPs in one hour in your pool than from a
week of drinking tap water.

So, just how bad is that?

Worse than you’d think, actually. A recent study published in the Journal of Environmental Sciences found that swimming in a chlorinated pool presented an unacceptable cancer risk.

They concluded that the cancer risk of trihalomethanes from various routes in descending order was:

1. skin exposure while swimming
2. gastrointestinal exposure from tap water intake
3. skin exposure to tap water
4. gastrointestinal exposure while swimming

But the cancer risk from skin exposure while swimming was 94 percent of the total cancer risk resulting from being exposed to THMs!

THMs formed in chlorinated swimming pools have also been linked to spontaneous abortion, stillbirths and congenital malformations, even at lower levels.

This information clearly demonstrates just how much more dangerous it can be to immerse yourself in a chlorinated body of water. But the toxic dangers of swimming pools don’t end there.

The chlorine in your swimming pool also reacts with organic matter such as blood, feces and urine, sweat, and skin cells to form another dangerous byproduct: chloroform (also called trichloromethane).

In scientific experiments conducted on laboratory animals, results indicate that the health effects of chloroform are similar whether you inhale or ingest it. These effects include damage to the liver, kidneys, and the central nervous system of rats. Moderate amounts (300,000 parts per billion) have been found to affect reproduction.

Similar health effects are seen in humans. In large amounts, chloroform may damage your central nervous system, liver and kidneys. Breathing high levels in the air (900,000 ppb) – such as in an indoor pool area – even for a short time, can cause tiredness, dizziness, or headaches.

After just one hour in a chlorinated pool, chloroform concentrations in your blood can range anywhere from 100 to 1,093 parts per billion (ppb). Indoor pools expose you to 70 to 240 times greater amounts of chloroform than outdoor pools.

This is an important point to remember, especially if you or your children suffer from asthma or other breathing difficulties. Asthma has increased 50 percent in developing countries in the last 25 years. It is thought that the chlorine byproducts in the air around indoor pools could be a contributing factor in the rapidly escalating increase in cases of childhood asthma.

It’s interesting to note that the Environmental Protection Agency (EPA) used to have a maximum contaminant level goal (MCLG) of zero for chloroform in drinking water due to its potential toxicity. They list it as a “probable human carcinogen,” and the U.S. Department of Health and Human Services has determined that chloroform may reasonably be anticipated to be a carcinogen.

However, the EPA was forced to remove the zero standard – effective as of May 30, 2000 — after the MCLG was successfully challenged in court by the Chlorine Chemistry Council and the Chemical Manufacturers Association.