A Historical Review of the Benefits and Hypothetical Risks of Disinfecting Drinking Water by Chlorination

Abstract

This review examines the benefits and alleged risks associated with the disinfection of drinking water by chlorination, through critical appraisal of the historical saga of chloroform as the main disinfection by-product (DBP). The author maintains that the provision of clean drinking water is a survival issue for humankind and supports unreservedly the recommendation by the World Health Organization (WHO) of the United Nations to disinfect by chlorination, for the reasons stated herein. The author aims to lead water professionals to a deeper understanding of the public health issues concerning chloroform and how the corpus of knowledge was attained by colossal multi-disciplinary effort on a global scale.

Origins of the alleged risks of chlorination are traced and the assumptions behind these allegations are questioned. The author welcomes and encourages innovations for improved methods of water treatment insofar that the standards of potability set out by the WHO are met in the very least, but argues that the commencement point of research into new techniques should be an acknowledgment of the development of disinfection up to contemporary times, on the part of water engineers and policy makers. There must be a clear recognition of the horrific consequences of failure to eliminate pathogens and toxic substances. To this effect, landmark tragedies are described to emphasize the point.

Significantly, this work addresses topics which are sine quo non to the debate over chlorination but which are often lacking in public discourse, namely: differences in the way cytochrome P450 enzymes oxidize carbon tetrachloride which is not normally a product of chlorination, and chloroform, which is a disinfection by-product; the role of free radical scavengers in protecting the human body; the difficulties of extrapolating experimental results from rodents to humans; the awareness of the complex relationship between governments, chemical industries, special interest groups and the public. Also introduced are the aetiologies of some cancers (e.g., Hepatitis B and C viruses as the instigators for hepatocellular carcinoma) to juxtapose claims that chloroform in drinking water is the sole culprit responsible for liver, bladder, colorectal cancers and birth defects etc. Other well known human carcinogens and a few inorganic compounds known to cause harm are also depicted. Lastly, a structured approach towards integrating the overarching concepts in the analysis of alleged carcinogenicity is applied to chloroform and the inferences discussed.

The literature reviewed spanned the years 1848 – 2017.