Chlorine Disinfection of Drinking Water
Approximately 75% of Canadian citizens rely on municipal water supplies. Chlorine is the disinfectant used predominantly in these
systems. Chlorine is an effective disinfectant (effectively kills germs), however treatment of water with chlorine can produce chemicals known as Disinfection By-Products (DBPs). Over 600 DBP chemicals have been identified. (Chowdhury et al 2011; Richardson et al. 2007). Many DBPs are toxic to cells and can cause DNA mutations and birth defects (cytotoxic, genotoxic, mutagenic, and teratogenic) (Pals et al 2011).
Chlorine and DBPs
The environment contains substantial organic material (plants, animals, soil etc.). During disinfection, these organic materials react with chlorine to produce chemicals known as Disinfection By-Products (DBPs). DBPs include: trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), haloketones (HKs), N-nitrosodimethylamine (NDMA), iodo THMs and others. All chlorine-related DBPs may not be identified yet. THMs and HAAs are the most commonly formed DBPs. (Chowdhury et al 2011; Richardson et al. 2007).
Health Effects of DBPs
DBPs in chlorinated water can enter the body by ingestion (e.g. drinking, eating), inhalation, and through the skin (e.g. in the shower or the swimming pool). The amounts of DBPs that enter the body via each route have been estimated by researchers. (Chowdhury et al 2009; Xu et al 2005; Jo et al 1990a; Jo et al 1990b; Backer et al 2000).
Some DBPs are of concern due to possible cancer risks to humans. The risk that a particular chemical can cause cancer in humans is
assessed using calculations based on animal data (bio-assay data) and estimates of the amount of chemical intake by humans (by
ingestion and inhalation and through the skin; chronic daily intake; CDI). The cancer risks associated with many different chemicals have been assessed using the Integrated Risk Information System (IRIS). In specific, DBPs are associated with bladder and colo-rectal cancer. (Chowdhury et. Al. 2011; King et al.).
Based on epidemiological evidence, for instance, King and Marrett reported that approximately 14–16% bladder cancers in Ontario, which is equivalent to 232–265 bladder cancer incidents per year, might be attributed to the drinking water containing higher
concentrations of DBPs. Data from Chowdhury et. Al. were consistent with the King and Marrett study. (King and Marrett 1996).
Based on IRIS assessment, approximately 700 cancer cases may be caused by exposure to THMs in drinking water in Canada every year. This does not factor in other DBPs such as HAAs. The rates of occurrence (incidence) and prevalence of THM-associated cancer are expected to vary across Canada based on population and regional DBP levels. (Chowdhury et. al. 2011)
Evidence also exists for causal association between DBP exposure and other health effects, including cardiac anomalies, stillbirth,
miscarriage, low birth weight and pre-term delivery (King et. al. 2000; Mills et. al. 1998; Villanueva et. al. 2004; Wigle et. al. 1998)
Recent evidence that HAAs can inhibit an important nervous system enzyme called GAPDH has possible implications in the pathogenesis of neurodegenerative disorders such as Alzheimer’s disease (Pals et al. 2011)
Health Canada has set guideline concentrations for some groups of DBPs in drinking water: namely, THMs (0.10 mg/L), HAAs (0.08 mg/L), bromate (0.01 mg/L) and chlorite (1 mg/L). Some provinces have established guidelines for THMs based on Canadian
guidelines or U.S. EPA regulations. Generally speaking, accepted limits for these DBPs are lower in Europe. Accepted limits for DBPs are being lowered in various parts of North America. Because each DBP is assessed individually, it is not fully understood how DBPs interact with each other or with other carcinogens in the human body (e.g. air pollution, pesticides).
Medical Costs of DBPs
Chowdhury et al. estimated the costs of bladder and colorectal cancers associated with THMs exposure for some cities in Canada. The average costs for typical bladder and colorectal cancers were estimated to be $208,000 and $187,000, respectively. Using an
average value of $200,000 for each cancer incident, medical expenses were estimated. Total medical costs of treating 703 cancer
patients in all provinces were estimated to be $140.7 million. The highest additional costs of treatment were predicted for Ontario ($47.1 million/year) followed by Quebec ($25.3 million/year).
In addition to cancer risks, chronic and sub-chronic exposure effects such as cardiac anomalies, stillbirth, miscarriage, low birth weight and pre-term delivery could also be attributed to chlorinated drinking water. The cost of dealing with these effects may be high. For
example, a low birth weight baby may need a total of $600,000 for special care, education, grade repetition and medical treatment for a full lifetime of 75 years and a cardiac anomaly patient may need $300,000 for his/her lifetime treatment (Chowdhury et al 2011).
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Dr. David Barnes is Vice-President Product Development and Regulatory Affairs for SanEcoTec Ltd. and AVIVE™. Dr. Barnes is a physician-scientist with expertise in product development, clinical R&D, regulatory approvals and commercial operations for a wide range of consumer products. He is a former Health Canada advisor and has executive-level experience with publicly traded pharmaceutical, biotechnology and health products companies around the world.