Editor:

Please excuse my temerity in writing from so far away, but I had heard about your issue in Chilliwack (the Internet is an amazing vehicle) and thought it might be useful to provide some historical information that could reduce some concerns about the benefits of chlorination of drinking water.

Even occasional detections of E.coli in public drinking water demonstrate that animal or human fecal matter is entering the water that people are drinking, and it is a serious public health matter, and could be the trigger for a boil water notice. Fecal contamination is the primary path for disease organisms entering drinking water.

Chlorine readily kills bacteria and viruses in water. It does not affect Cryptosporidium protozoa that sometimes occur and are also of mammalian fecal origin, but they are well eliminated by filtration or UV light.

Some E.coli (e.g., 0157-H7) are killer pathogens in themselves, but mostly they are considered to be indicators for the potential presence of other pathogens that can be transmitted from infected persons via sewage. Waterborne diseases are not easy to detect in a community, and they seldom result in deaths in our countries, but they can still occur, as in Walkerton, Ont. in May 2000 when seven consumers died from untreated contaminated drinking water. They could be occurring occasionally without being identified as an outbreak, but they should not be occurring at all in North America.

Historically, chlorine began to be used in England and parts of Europe in the late 19th century and it was first used in the U.S. in Jersey City, N.J. in 1908, and not without controversy. After the dust settled, chlorination was quickly introduced in many other cities and the data show that the incidence of deaths due to typhoid fever began to drop immediately and eventually disappeared. Today chlorine is used in some form in about 90 per cent of U.S. waters. Chlorination and filtration are credited with essentially eliminating waterborne disease in the western world, especially. Public health officials consider it the major advance and benefit to public health in the 20th Century.

In the mid 1970s tri-halomethanes (THMs) were shown to be byproducts of chlorination. In my position as Director of the Drinking Water Standards Division at USEPA, we regulated THMs as a means of driving the introduction of technologies that would preserve the benefits of chlorination while minimizing the byproducts.

That regulation has been successfully implemented in both large and small communities. Almost all countries have THM standards and the World Health Organization has international guidelines.

The chlorination technology is very effective. I chair the Water Quality Committee of the Board of Directors of the Washington, DC, USA Water Authority. We are a city of about 650,000 with a relatively old distribution system. Our water comes from a good but non-pristine river source. It is chlorinated as primary disinfection, and then ammonia is added to suppress formation of byproducts and maintain a disinfectant residual during distribution, and it also virtually eliminates the chlorine taste. Very occasionally we get a positive total coliform result out of the hundreds of samples that we collect each month in the distribution system. Total coli-forms are usually not of fecal origin. They are transient and caused by distribution system issues. I do not recall any positive E. coli tests in the years that I have been there.

Appropriate disinfection of drinking water by several techniques is very inexpensive on a per gallon basis and very cheap insurance. The residual disinfectants are easily detected with simple testing, and that allows everyone to rest more easily, knowing that there are no pathogen risks to be concerned about.

Joseph A. Cotruvo, PhD Washington DC