In the U.S. we are facing degradation of our waterways by pollutants and microbial contaminants, resulting in an average of one million cases of waterborne disease per year. Microbial contaminants, such as Giardia, Cryptosporidium, and the new Cyclospora, are causing major outbreaks across the nation.
In the 1960's Giardia became a prevalent contaminant of health concern that prompted the enactment of the Surface Water Treatment Rule that stated that all surface water that may potentially be used for drinking water must be filtered. Unfortunately, problems with Giardia, viruses, newer protozoans (like Cyclospora), and, especially, Cryptosporidium are still occurring.
Chlorination has little effect on cysts and protozoans like Cryptosporidium. We are also finding that merely filtering surface water isn't solving the problem since most microbial outbreaks of this sort are occurring in ground water sources (of all the waterborne outbreaks between 1991-92, 77% occurred in wells). Even pristine water sources (which are closed to human activity) are not safe from microbial contamination since sources of microbial contaminants are not only human waste products, but also animal feces.
Giardia can be killed by long contact with chlorine, but Crypto is much more resistant. Filtration is the only effective way to get Crypto out of the water. Often, unfortunately, "rapid filtration" at the public utilities water treatment plants doesn't do the job, and Crypto makes it through to the public's tap water.
Recently, a new cyst, Cyclospora, has made its presence known. Like Crypto, it produces intestinal disorders and is resistant to disinfection. Unlike Crypto, Cyclospora oocysts must be mature before they are infectious (so, if the body clears the cysts before maturation, there will be no infection). It is also larger in size than Crypto and is, therefore, easier to filter out of the water.
Although most of the intestinal disorders caused by microbial infection affect a large segment of the population only like a stomach flu or traveler's diarrhea, over 5 million Americans (the immunocompromised, the aged, infants, and pregnant women) are at a much greater risk (possibly even of death). Emerging patterns of rainfall, sewage overflows, and animal excrement are leading experts to believe that microbial outbreaks are going to continue and probably worsen.
Filtration has become the focus for control of these microorganisms. Disinfection had always been the major barrier for control, but we are finding microorganisms that are resistant to disinfection. Filtration has got to be the focus here.
Contaminants that are causing widespread concern as of late are Disinfection By-Products (DBP's). Many believe that DBP's are the single greatest health threat in water supplies. DBP's are contaminants, some of them cancer-causing, that are left behind by the very chemical (chlorine) that utilities use to make their water potable.
Since the early 1900's chlorine has been added to drinking water to control the spread of typhoid, cholera, and other diseases. About 15 years ago scientific testing identified chlorine as a potential health hazard, but it is not the chlorine in itself that is dangerous. Scientists discovered that chlorine reacted with organic material in water, such as decaying leaves, to produce hundreds of chemical by-products, several of which have been proven to be carcinogenic (Trihalomethanes make up the bulk of the cancer-causing DBP's). Other disinfection by-products may cause adverse effects on the liver, and nervous and reproductive systems.
The use of chlorine for water treatment to reduce the risk of infectious disease may account for a substantial portion of the cancer risk associated with drinking water. Trihalomethanes are associated with increased risk of bladder and rectal cancer, possibly accounting for 5,000 new cases of bladder cancer and 8,000 new cases of rectal cancer per year in the U.S. Given the large number of people who consume chlorinated drinking water, the number of cases of cancer potentially attributable to this exposure is substantial. Obviously, something needs to be done.
To stop chlorination of drinking water to eliminate the elevated cancer risks from disinfection by-products would be foolhardy. Nonetheless, these findings support expanded efforts in research and development of alternatives to chlorination for the disinfection of drinking water.
There are several alternatives in reducing DBP's in our drinking water. The first is to keep the organic matter out of the source water. We can also find different methods of disinfection (chloramination, for example, produces fewer by-products). Since a large percentage of the DBP's are developed after leaving the treatment plant, an alternative may be to protect the water delivery system from organic matter.
In the meantime, our only viable course of action is point-of-use filtration using an activated carbon filter. Currently carbon filtration is the only known way to get cancer-causing Trihalomethanes and other dangerous disinfection by-products out of our nation's drinking water.