Chlorine: What Are Your Kids Swimming In?

It’s summer, and the kids are at day camp!

Unfortunately, for all the fun he’s having, my son has developed a rash, which my wife and I now suspect might have something to do with chlorine—after all, campers go to the pool twice a day, which is a lot of exposure to this all-but-ubiquitous water purification chemical.

It turns out that using chlorine to purify water has an interesting and controversial history that raises many questions about the price we pay for safety and public health.

Water was first purified with chlorine by the Scottish chemist William Cumberland Cruikshank in 1805. By the turn of the century, British chlorination of drinking water had sharply reduced deaths from Typhoid Fever.

In 1908, chlorine was added to drinking water in the U.S. for the first time in Chicago’s Union Stockyards. According to the American Chemistry Council [PDF],  the stockyard had been watering the animals from a stream “so polluted with meat waste that it bubbled with noxious gases,” and the animals were failing to thrive.

The stockyards were filtering the water, but it still contained high levels of dangerous bacteria, so they hired a New York water filtration expert, who added chlorine, “with the surprising result that the quality of the livestock drinking water was reported to surpass that of city water,” according to the Council.

In an even more interesting case, Jersey City was the first city to chlorinate municipal drinking water for human consumption in 1908, after a long legal battle between the city and its private water supplier. Dr. John Leal, an advisor to the water company, did research to show that water-born illnesses increased after flooding, which, he argued, indicated that water was contaminated from street runoff rather than at the source. As a solution, he proposed adding small amounts of chlorine to water and thereby started a trend that within a decade and a half had come to most American cities.

That these first examples are heralded by American Chemistry Council as heroic feats is in some ways ironic, because, by their own telling, chlorination was an end-use solution to comprehensive (and disgusting) design-flaws in the system: animals forced to drink from a river filled with meat waste, and municipal water that was routinely polluted with surface runoff.

Nonetheless, the widespread introduction of chlorine seems to have all but eliminated water-born illnesses in the developed world, though it is not certain to what degree better sanitation practices alone contributed, or if there are other solutions to achieve consistently clean, pathogen free water.

It’s an important question, because in spite of its apparent benefits, the widespread use of chlorine carries substantial risks as well. In higher concentrations, of course, chlorine is a potent poison, most notoriously used as a chemical weapon in the First World War, where it drifted across the landscape as a green cloud, sinking into trenches and eating away the soldiers’ lungs when they breathed it.

But even in very low does, there’s evidence that chlorine is not entirely benign. According to the United States Health and Services Toxicology program, chloroform, which can be found in the breakdown of chlorinated drinking and swimming pool water, is a known carcinogen. Epidemiological studies have suggested that the consumption of chlorinated water “may be associated with the development of certain cancers in humans.”

Other studies have linked swimming pool chlorine with elevated asthma, with the strongest correlation in young children – stronger than exposure to “all other factors combined” including tobacco smoke. Other sources have suggested that skin absorption of chlorine from hot showers is a serious risk to health. Ecological hazards are also well known.

Nearly two decades ago, the International Join Commission, an independent organization established by the U.S. and Canada to monitor and address water quality issues in the great lakes, issued a report advocating a complete phase out of chlorine and its by-products. And in 1994, President Bill Clinton asked the EPA to draw up a national strategy for “substituting, reducing or prohibiting the use of chlorine and chlorinated compounds” according to the New Scientist. As far as I can tell though, use of chlorine in drinking water and swimming pools is going on strong.

So, what’s the alternative? For drinking water, there are filters; if you’re concerned about showers, they can be installed at the house main, so that all domestic water use is chlorine free. Ozone disinfection is one time-tested alternative, but is potentially more complicated and more expensive than chlorine purification. Ultraviolet light has also been used, but (along with ozone) has been criticized for leaving no trace disinfectant in the water.

More radical is the idea of careful design and biological filtration. The fact that some 40 million Americans get their water from non-treated, private wells would seem to suggest that non-chlorinated water doesn’t automatically equal sickness and death.

In recent years, a number of companies and ecological designers have developed techniques to use artificial wetlands to purify water, and use of natural filtering systems in swimming pools is well established, at least in Europe.

So—chlorine has helped rid the developed world of serious diseases, but has created substantial risks of its own. Can we do better?