Pool Chlorine Hypothesis

The pool chlorine hypothesis is the hypothesis that long-term attendance at indoor chlorinated swimming pools by children up to the age of about 6–7 years is a major factor in the rise of asthma in rich countries since the late twentieth century. A narrower version of the hypothesis, i.e. that asthma may be induced by chlorine related compounds from swimming pools, has been stated based on a small numbers of cases at least as early as 1995. An empirically motivated statement of the wider form of the hypothesis is first known to have been published on the basis of tests of the effects of nitrogen trichloride above chlorinated water on the lung as well as epidemiological evidence by a group of medical researchers led by Alfred Bernard of the Department of Public Health in the Catholic University of Louvain in Brussels, Belgium in 2003. In the epidemiological studies, the association between chlorinated swimming pools and asthma was found to be more significant than factors such as age, sex, ethnic origin, socioeconomic status, exposure to domestic animals and passive smoking (in a study in Brussels), and independent of altitude, climate, and GDP per capita (in a Europe-wide study of 21 countries).