The Association Between Drinking Water Quality and Oesophageal Cancer Risk and Mortality: A Systematic Review

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Introduction

Current knowledge of risk factors for oesophageal cancer do not fully account for disparate oesophageal cancer incidence worldwide. Numerous studies have reported conflicting results regarding the association between drinking water quality and oesophageal cancer development, or related mortality, but this evidence has yet to be summarised.

Aims

To conduct a systematic review of evidence investigating the association between the quality of drinking water and oesophageal cancer incidence/mortality risk.

Methods

A search strategy was applied to four databases from inception to June 2018. Observational studies evaluating drinking water quality and oesophageal cancer risk or mortality in adults were included. Studies were categorised according to the measure of drinking water quality investigated (source, nitrogenous compounds, Ca/Mg, heavy metals and other). A random effects meta-analysis was conducted for studies evaluating drinking water source.

Results

Thirty-four studies were included, consisting of 14 casecontrol, four cohort and 16 ecological studies, that examined a variety of exposures relating to drinking water quality. The pooled risk estimate from six case-control studies (five from China and one from Iran) showed a significant increased risk of oesophageal cancer in individuals drinking non-tap water, compared with tap or piped water (relative risk 2.41, 95% confidence interval 1.42-4.08). Too much heterogeneity existed among other studies to enable metaanalyses.

Conclusion

Consuming water from non-piped sources was associated with a 2.4-fold increased risk of oesophageal cancer, comparing with tap water consumption. Further studies are needed to examine the specific contaminants in drinking water that may be involved in oesophageal cancer aetiology.