§ Mr. Teddy Taylor
asked the Secretary of State for the Environment in how many cases district medical officers of health have agreed to water authorities working to nitrate levels in public water supplies above the level of 50mg per litre in the most recent annual period for which figures are available.
§ Mr. Waldegrave
The agreement of district medical officers of health is not required should nitrate levels in public water supplies be greater than 50mg/litre. However, in these cases they are normally notified so that any appropriate monitoring for, and precautions against, methaemoglobinaemia can be taken. This procedure is in accordance with independent medical advice given to Government in the following termsThe concentration of nitrate in the public water supply should not exceed 100 milligrams of nitrate ion per litre (22.6mg nitrate-nitrogen (NO3-N) per litre), other than in exceptional and transient circumstances.At the same time water undertakings should continue to aim to keep the concentrations below 50 milligrames of nitrate (11.3mg NO3-N) per litre.However, where the concentration in the water supply exceeds:50 milligrams of nitrate (11.3mg NO3 -N) per litre, but is below 100 milligrams of nitrate (22.6mg NO3 -N) per litre, the health authorities and professions in the affected area should be informed so as to encourage monitoring for infantile methaemoglobinaemia.100 milligrams of nitrate (22.6mg NO3-N) per litre, at any time, suitable low-nitrate water should be provided for infant feeding.
Extract from statement of Joint Committee on Medical Aspects of Water Quality, April 1984.