Drinking Water Quality

Description

High-quality, safe and sufficient drinking water is essential for public health and well-being [European Commission].

Impact 

The quality of drinking water is related to the risk of health outcomes. The majority of published studies examining the impact of drinking water on health have largely been conducted in high-income countries.

Disinfection processes to improve the quality of drinking water have been one of the major breakthroughs in public health over the last century [Wigle 1998; Ngwenya 2013]. These processes have had a profound impact on the incidence of water-borne diseases [US Safe Drinking Water Committee]. 

However, unsafe drinking water remains a major source of morbidity and mortality globally [Sobsey 2006]. 

Chloroform and other chlorinated products have largely been used for water disinfection processes. However, results of animal studies have shown that prolonged exposure to water disinfection by-products is associated with an increased risk of bladder cancers [Smith 2022]. But, the WHO recommends that in all circumstances, water disinfection efficiency should not be compromised in trying to meet guidelines for disinfection by-products [WHO 2017].

Results

Two systematic reviews comprising 37 primary articles were identified. One systematic review (n=18 studies) assessed the endemic risk of acute gastroenteritis risk based on drinking water operation conditions in urban areas of developed countries [Beaudeau 2020]. Findings from 17 urban sites were included – 10 in Europe and 7 in North America.

The second systematic review (n=19 articles) examined the relationship between the concentration of disinfection by-products in drinking water and the risk of cancer [Benmarhnia 2018]. The authors also investigated the extent to which effect measure modification (EMM) was used to assess the relationship between disinfection by-products in drinking water and cancer. A total of 19 studies were included: 11 were conducted in North America, 6 in Europe, and 2 in Asia.

Outcome: acute gastroenteritis

• Turbidity (or particle count) in finished water was significantly associated with indicators of acute gastroenteritis in 11/16 (69%) sites [Beaudeau 2020]
• Water temperature, river flow, and produced flow were strongly associated with indicators for acute gastroenteritis [Beaudeau 2020]
• Issues related to water distribution (e.g., leaking pipes, cuts in the water supply) or repair interventions were not strongly associated with the incidence of acute gastroenteritis [Beaudeau 2020]
• Where significant relationships were reported, the interquartile excess of relative risk estimates ranged from 3 to 13% [Beaudeau 2020]

Outcome: cancer

• There was a significant relationship between drinking water disinfection by-products and cancer risk in 14/19 (74%) studies [Benmarhnia 2018]

Strength of the evidence

None of the included reviews reported on the quality of included primary studies, The evidence is therefore rated as low quality.

Resource implications

None of the reviews assessed the financial and/or economic impact of drinking water quality. However, disinfection.

The UN’s declaration of the human right to water (Target 6.1. of SDG 6) states: “To achieve universal and equitable access to safe and affordable drinking water for all.” The UN states that water bills should not exceed 3 percent of a household’s budget.

Recommendations

• The time interval for exposure assessment needs to be standardised
• More longer-term studies should be conducted to investigate the association between drinking water and infectious disease
• Studies assessing the quality of drinking water should be conducted in low- and middle-income countries.
• Subgroup analysis should be better reported to provide a better understanding of which populations or territories are more vulnerable to the impacts of disinfection by-products
• Public health campaigns should promote the provision of access to good quality water, especially in deprived populations.
• Improvements in water distribution infrastructure (plumbing systems, hydraulics, disinfection)

Related Resources

• European Commission. “Drinking water: Improving access to drinking water for all”. Available at: https://environment.ec.europa.eu/topics/water/drinking-water_en 
• Wigle 1998. “Safe drinking water: a public health challenge.” Chronic diseases in Canada vol. 19,3 (1998): 103-7.
• Ngwenya 2013. “Recent advances in drinking water disinfection: successes and challenges.” Reviews of environmental contamination and toxicology vol. 222 (2013): 111-70. doi:10.1007/978-1-4614-4717-7_4
• Smith 2022. “Risk of bladder cancer and lymphoma in dogs is associated with pollution indices by county of residence.” Veterinary and comparative oncology vol. 20,1 (2022): 246-255. doi:10.1111/vco.12771
• National Research Council (US) Safe Drinking Water Committee. Drinking Water and Health: Volume 2. Washington (DC): National Academies Press (US); 1980. II, The Disinfection of Drinking Water. Available from: https://www.ncbi.nlm.nih.gov/books/NBK234590/ 
• Sobsey 2006. “Drinking water and health research: a look to the future in the United States and globally.” Journal of water and health vol. 4 Suppl 1 (2006): 17-21.
• Evans 2020. “Analysis of Cumulative Cancer Risk Associated with Disinfection Byproducts in United States Drinking Water.” International journal of environmental research and public health vol. 17,6 2149. 24 Mar. 2020, doi:10.3390/ijerph17062149
• World Health Organization 2017. “Guidelines for Drinking-Water Quality.” 

References to Reviews

Beaudeau 2020. “A Systematic Review of the Time Series Studies Addressing the Endemic Risk of Acute Gastroenteritis According to Drinking Water Operation Conditions in Urban Areas of Developed Countries.” International journal of environmental research and public health vol. 15,5 867. 26 Apr. 2018, doi:10.3390/ijerph15050867

Benmarhnia 2018. “Heterogeneity in the Relationship between Disinfection By-Products in Drinking Water and Cancer: A Systematic Review.” International journal of environmental research and public health vol. 15,5 979. 14 May. 2018, doi:10.3390/ijerph15050979