Mercury

Guidelines

Unit of measurement

μg/l

World Health Organisation Standards (1993)

1.0

Standards for private water supplies in England (2016)

1.0

Standards for private water supplies in Scotland (2006)

1.0

Standards for private water supplies in Wales (2017)

1.0

European Union Drinking Water Directive (1998)

1.0

Mercury

Mercury in the environment caused some concern a few years ago when it was found in fish as organic mercury. Organic mercury in the form of methyl mercury has been found to cause neurological problems with a daily intake of as little as 0.25 mg. Mercury is a cumulative poison and so low levels of organic mercury can build up in the body over a period of time. Fortunately, mercury in drinking water is predominantly inorganic, which is poorly absorbed by the body. Nevertheless, a very low limit for mercury is set.