Water glassA new study that was published in the renowned journal Science this week set out to investigate how qualitative and safe the tap water is in the United States, Great Britain and the Netherlands. In both Great Britain and the United States, the use of disinfectant residual is required in drinking water, while in the Netherlands such disinfectants are absent when the water is distributed to consumers. The researchers of the study wanted to investigate if and how this affected waterborne disease outbreaks.

The United States and the United Kingdom add disinfectants such as chlorine to the water supply to prevent microbial growth and to safeguard consumers from pathogens from other sources. Unfortunately, there are some downsides to the usage of disinfectants in drinking water. Disinfectants are suspected to lead to the formation of carcinogenic (i.e. cancer-inducing) by-products and can lead to corrosion of water distribution pipes. Furthermore, the drinking water can get a distinctive taste and scent of disinfectant. 

Some European countries (e.g. the Netherlands, Germany, Switzerland, Austria) opt to deliver drinking water to consumers without a residual disinfectant. As long as there is adequate source protection, treatment, and maintenance of the distribution system to prevent growth of pathogenic bacteria this seems to be a safe and responsible practice.

Does the absence of disinfectant lead to a greater incidence of waterborne disease outbreaks in western Europe?

The researchers of the study conclude that there is little direct evidence that disinfectant residuals have prevented drinking water–related disease outbreaks in the United States and the United Kingdom. Of the three countries, the risk of contracting a waterborne disease from drinking tap water is lowest in the Netherlands, despite the absence of disinfectants.

The researchers do remark there might be an additional important factor which contributes to the Netherlands’ good performance: the robustness of the water distribution system. In the Netherlands, more than half of the water pipelines have been replaced since the 1970s, and on average pipe networks are around 35 years old. In the United States, a substantial proportion of the pipes (+- 22 %) are more than 50 years old, while the average age of a pipe at failure is 47 years. Due to the “antiquity” of the pipe network, the majority of the pipes in the United States are considered not to be in good condition. In the United Kingdom, the pipe network is also very old compared to the Dutch pipe network; it is estimated that the average water distribution pipe in the UK is around 75 to 80 years old. Due to their age, the pipe networks in the United Kingdom and the United States are far more vulnerable for leakage than the pipe system in the Netherlands. Leaks in the network are a serious safety hazard, as harmful substances can enter the water supply, which in turn further increases the urgency of adding disinfectants.

The main conclusion following the comparison of the three countries is that a well-maintained distribution system is a pivotal component in ensuring water safety. At the same time it can make the usage of disinfectants obsolete if additional quality measures are in place.

Remaining issues with water quality in western Europe

The drinking water system in the Netherlands performs well, but it is far from perfect. Professor Jan Peter van der Hoek of the University of Delft in the Netherlands states that there still is a relatively high presence of drug residue and pesticides in the Dutch potable water supply. Similar issues are also prevalent in most other European countries. Professor van der Hoek argues that additional efforts have to be undertaken to address these issues.

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