Drinking water purity - a UK perspective

Water purity is a vague term. Applied to drinking water, the emphasis of pure can mean ‘free from all types of bacteria and viruses’ as defined by the United States Environmental Protection Agency, or as being ‘wholesome’ when defined within Great Britain. US and British standards are based on the protection of public health. Strictly enforced values for a broad set of physical, chemical and biological parameters, informed by expert evidence gathered from many countries over a long period of time, are applied in an effort to ensure a minimum purity is achieved regardless of geographical location within those areas. Other countries like Australia, Canada and New Zealand however, do not have such strict legal definitions. Instead, best endeavours under local circumstances, measured against ‘guideline’ values for a narrow set of parameters, are used to judge water quality, and hence purity. These discrepant definitions can lead to confusion so this brief has been created to clarify current understanding of the meaning of ‘water purity’.