Chlorinated swimming pool increases the risks of asthma and hay fever

	Recent studies in Europe showed that regular visits to chlorinated swimming pools are related to higher rates of asthma and hay fever. Scientists suggested that the chlorination by-products, both in the water and the air, may damage the linings of the lung. This allows closer contact to allergens, resulting in asthma, hay fever and exercise-induced coughing.

	A better alternative is to swim in beaches with good water quality. There are an increasing number of swimming pools using other means of disinfection, such as ozone or hydrogen peroxide. However, ground level ozone is also harmful to health.

What are chlorination by-products

Chlorine is a colourless and pungent gas. It has been commonly used to disinfect water since the beginning of the 20th century. However, chlorine will form a few cancer-causing chemicals (called by-products) in water.

The main chlorination by-products are trihalomethanes (THMs) and chlorinated acetic acids. THMs are formed when chlorine interacts with tiny particles of decaying organic matter in the water. Chloroform is one of the THMs found in many water supplies.

These chlorination by-products are responsible for most of the bacterial genetic mutations found in drinking water. Some studies found that high levels of THMs in drinking water were related to cancers in organs such as the bladder, kidney, and stomach etc.

A German Research found higher risks of hay fever from chlorinated pool

A research on chlorinated swimming pool was conducted in 2006 by the GSF-National Research Centre for Environment and Health in Neuherberg of Germany. The medical history and swimming pool attendance of 2,606 adults from 35 - 74 years old were surveyed through personal interviews and questionnaires.

Researchers found the following results:

	Those people who attended chlorinated swimming pool 3 to 11 times each year at school age were 74% more likely to develop hay fever than those who never attended a pool at school age.

	Recent exposure to chlorinated pool also increased the risk of hay fever. Those who visited chlorinated pools more than once a week in the last 12 months were 32% more likely to have hay fever than those with no exposure.

	Those who reported any lifetime exposure to chlorinated swimming pools were 65% more likely to have hay fever than those with no exposure at all.

The scientists remarked that the causes of hay fever involved multiple factors. Although the chlorination by-products in swimming pools might not be the leading cause of hay fever, especially among adults, they might be an important contributor to it.

Their research results were published in the Nov 2006 issue of the journal Allergy. (Related News: Nov 24, 2006)

A study on 21 European countries showed higher asthma risks with chlorinated pools

A research was conducted by scientists at the Catholic University of Louvain, Belgium. The team studied the rates of asthma, hay fever, allergic rhinitis and atopic eczema for almost 190,000 children, aged 13-14, from 21 European countries.

The key findings were:

For each extra chlorinated pool per 100,000 people, childhood wheezing rates in that area rose by 3.38%, while childhood asthma rates rose by 2.73%. Even after factoring out differences in wealth, climate and altitude, the link was still there.

In Eastern Europe, many countries had one indoor pool for every 300,000 people, while in Western Europe the average was about one for every 50,000 people. From the research findings, the scientists suggested that the much higher rates of asthma in Western Europe than the eastern side could be partly explained by more exposure to the chlorination by-products in swimming pools.

Their research results were published in the journal Occupational and Environmental Medicine. (Related News: July 18, 2006)