Chlorine contamination of drinking water

Anthony Amis

More attention should be paid to the elephant in the room in terms of drinking water quality − chlorine. More specifically, chlorine disinfection byproducts, which are created when organic molecules in the water distribution system interact and react with chlorine.

For some time, I have been researching the impacts of pesticides and heavy metals on drinking water. Much of the information is buried in the appendices of scientific reports, or on computers in various water authority offices, or in the bowels of governmental departments. It was often a painstaking process, piecing together tiny fragments of a jigsaw puzzle that could never be properly put together, because very often the information just wasn't there in the first place.

Through my research it is evident that many Australian drinking water supplies are exposed to pesticides, yet few instances occur when the levels recorded go over the generous drinking water guidelines set by the National Health and Medical Research Council or the World Health Organisation (WHO). I have collated a list of almost 2000 pesticide detections in domestic water supplies across Australia and there have been 24 instances which have breached the Australian Drinking Water Guidelines.

It is little wonder that regulators have been slow to react when there have been few detections of breaches of drinking water guidelines. Nonetheless, there are a host of ecological and health problems associated with even very low levels of pesticides. But in terms of human health, drinking water breaches from pesticides pale into insignificance when one looks at chlorine disinfection byproducts.

In July, Friends of the Earth submitted a Freedom of Information application to SA Water. We asked for all substances that SA Water tests for in relation to health criteria. In August, SA Water replied with over 9000 pages of information, including over 600,000 individual test results. The documents reveal 9358 breaches of Australian Drinking Water Guidelines and World Health Organisation guidelines.

Of the breaches, 35 were for heavy metals, four for ecoli and the rest (over 99.5%) for chlorine and its disinfection byproducts. Chlorine was first used as a disinfectant in the early 20th century as a means of controlling water borne diseases such as cholera and typhoid which had killed hundreds of thousands of people. Chlorine disinfection byproducts weren't discovered until 1974 and have been linked with bladder cancer and adverse reproductive outcomes. Approximately 700 chlorine disinfection byproducts have now been identified.

Approximately 90% of the breaches revealed in the Freedom of Information documents occurred in country South Australia, with the largest number of breaches between 2000−12 recorded at Kingscote (Kangaroo Island) 435, Loxton 325, Burra North 302, Port Pirie 259, Port Augusta 257, Maitland 232, Morgan 224, Willunga 205, Crystal Brook 178 and Whyalla 173. In terms of the greater Adelaide region, the highest number of breaches were recorded at Craigmore 54, Happy Valley 30, Seaford Rise 27, Blakeview 23, Elizabeth Downs 22, Andrews Farm 21, Enfield 19, Blackwood 18, Chandlers Hill 16 and Glenalta 15.

The highest number of breaches were for monochloramines (5165). There are concerns that chloramines can cause various health problems and aggravate existing ones, primarily skin, digestive and respiratory ailments.

The second highest number of breaches were for dichlorobromoform − 2382 breaches of the WHO Guidelines. Dichlorobromoform has commonly been detected in Adelaide drinking water above WHO guidelines for the past decade, at least. According to the WHO, dichlorobromoform is possibly carcinogenic to humans, and there have been both positive and negative results in a variety of in vitro and in vivo genotoxicity assays.

Trihalomethanes were the next most commonly detected substance (581). These were concentrated mainly on Kangaroo Island, however detections have increased significantly since 2010, particularly in locations in the lower Murray such as Hindmarsh Island.

Levels of N-Nitrosodimethylamine − a suspected carcinogen − breached guidelines levels regularly in the SA Lower Lakes, with the highest level recorded at Keith.

Water authorities are making a trade off between the risk of people being exposed to dangerous diseases such as typhoid if chlorine was not used, and the lower risk of people developing bladder cancers and the like if chlorine continues to be used. It is unlikely that authorities will reduce the amount of disinfectant being used for fear of being responsible for a waterborne disease outbreak.

Chlorine does not have to be used at all as a disinfectant. Ultraviolet light works well as a disinfectant and is commonly used in Europe. However the cost of converting water facilities over from chlorine to UV treatment may be prohibitive. People concerned about consuming chlorine disinfection byproducts can reduce levels with a good quality water filter. Filters using reverse osmosis or activated carbon would probably be the best option and can be fitted under kitchen sinks.

Anthony Amis is the pesticides spokesperson for Friends of the Earth, Australia.