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IFST Advisory Statement --Contamination of Water: Boil Water Advice

January 30, 2004

The Institute of Food Science & Technology, through its Public Affairs and Technical & Legislative Committees, with advice from its Professional Food Microbiology Group, has authorised this Advisory Statement, dated January 2004.

Introduction

In the event of microbiological contamination of mains water supplies, water utilities in the area(s) concerned would, in most instances, issue advice to the public to boil water before use. This Advisory Statement summarises science-based advice as it affects water for drinking, for use in the home and for other uses in connection with the handling and preparation of food.

Meaning of "Boil water"

"Boil water" means bringing water to the boil in a kettle or saucepan, allowing it to boil for at least one minute and then letting it cool (covered in the case of an open saucepan).. This should inactivate all major waterborne bacterial pathogens (for example, Vibrio cholerae, pathogenic Esherichia coli, Salmonella, Shigella sonnei, Campylobacter jejuni, Yersinia enterocolitica and Legionella pneumophila) and waterborne protozoa (for example, Cryptosporidium parvum, Giardia lamblia, and Entamoeba histolytica). It should also be effective for waterborne viral pathogens such as hepatitis A virus, which is considered one of the more heat-resistant viruses. However, if the water is cloudy, it is recommended to boil for ten minutes.

Care must be taken to keep the boiling process out of the reach of children.

While we are aware of the efficacy of chemical water treatment kits used in camping, caravanning, boating, etc, for the vast majority of people these would not be readily available at short notice, nor the experience in how to use them. Both the Centers for Disease Control (CDC) in the USA and UK Boil Water Advice specifically advise against the use of purification tablets in the circumstances that give rise to a "Boil Water Advisory". For example in http://www.healthprotection.org.uk/communicable/BoilWaterAdvice.html
"Water purification tablets are not recommended as an alternative to boiling."

Water for use in food manufacturing premises

Water supplied to any premises by a water undertaker (water authority in Scotland) is subject to the quality and safety provisions of the Water Industry Act 1991 and the Water (Scotland) Act 1980 as amended. This would apply to abattoirs and associated premises as well as factories. Water sold as a "food" or used as an ingredient of a food, whether supplied by a water undertaker (authority) or from a private supply, is subject instead to the requirements of the Food Safety Act 1990.

In-plant filtration/purification/chlorination systems are designed to deliver effectively contamination-free water for bottling or for use as an ingredient or for the purposes of the washing of equipment, hands, fruit and vegetables, etc. Such systems should be carefully maintained as part of the food hygiene procedures of the factory. For very small factories that do not possess such systems, see requirements under "institutions and catering establishments", below.

Water for use in institutions and catering establishments

Most such establishments will not possess purification systems and would need to boil and cool any water that is to be used for food that is not otherwise going to be cooked. This includes water for drinking and for washing raw fruits and vegetables, especially leafy vegetables that are to be used in salads.

Boiled water should also be used for cleaning food preparation surfaces and for washing the hands before handling food that will not be cooked, in order to avoid cross contamination of the food.
Washing up should be carried out in water which has previously been heated to at least 70°C for 5 minutes and allowed to cool to the desired temperature; or in a dishwater which heats the water to at least 70°C.

Ice previously prepared for use in drinks should be discarded and fresh ice made from boiled-and-cooled water.

Cold drinks dispensers supplied with mains water should not be used.

Water used in the home

Domestic filters are not normally capable of adequate microbiological purification.
In the home, therefore, boiled-and-cooled water should be used for drinking and for the washing of fruit and vegetables, particularly leafy vegetables to be used in salads. Boiled-and-cooled water should also be used for cleaning food preparation surfaces and for washing the hands before handling food that is not to be cooked, in order to avoid cross contamination of the food. Washing up should be carried out in water which has been brought to the boil and allowed to cool to the desired temperature, or in a dishwater which heats to at least 70°C. Alternatively, washing-up could be carried out in the home's normal hot water supply and rinsed with boiled-and-cooled water before drying.

Ice previously prepared for use in drinks would need to be discarded and fresh ice made from boiled-and-cooled water.

Cleaning of teeth should be carried out with boiled-and-cooled water

Bathing and washing can be carried out with mains water, taking care to avoid any ingestion of the water. However, hands should washed with boiled-and-cooled water before handling any food that is not otherwise to be cooked. This is to avoid cross-contamination of the food.

Institute of Food Science & Technology