27 April 2000

Worlds first study shows water supply does not contribute to gastrointestinal disease.

A world first research study published on 6 April 2000 suggests that major metropolitan water supplies do not contribute to gastrointestinal illness.

The $3 million study compared the health of people drinking sterilised water with people drinking ordinary tap water in Melbourne. There was no difference in the incidence of gastroenteritis between the two groups over a 16 month period. The researchers said they found no evidence of waterborne disease.

The Water Services Association of Australia (WSAA) said spending hundreds of millions of dollars on higher water treatment standards would have no effect on human health.

"Some people believe we should sterilise water to remove every last trace of bacteria and other organisms," the association's Executive Director, Dr John Langford, said. "We could do that if Australians were willing to pay far more for drinking water, but this new research shows it would not improve public health."

Dr Langford said the research demonstrated how to measure any health benefit from stricter treatment standards. "We should be focussed on improving public health, not producing sterilised water," he said.

The research was carried out by a team from the Department of Epidemiology and Preventive Medicine at Monash University in Melbourne, as a partner in the Cooperative Research Centre for Water Quality and Treatment (CRCWTQ).

It is the first rigorous study anywhere in the world that a major research project has studied the impact of drinking water on people's health. Previous water quality studies have focussed on measuring bacteria levels rather than health effects.

The WSAA, which co funded the research, described the report as a major contribution to debate on the future management of water supplies. The WSAA is made up of 21 urban water businesses and authorities serving approximately 13 million Australians.

"The water industry contributed to this research because we wanted to know if major additional investment in water treatment could be justified on public health grounds," Dr Langford said.

"The Monash University research answers that question and the answer is NO. Melbourne's water is unfiltered because the water supply catchments are highly protected. In most other Australian cities filtration is provided in recognition of the fact that catchments are often less protected. Additional treatment of city water supplies would cost hundreds of millions of dollars. If we have that much extra to spend on public health, we would get a better result putting the dollars into the hospital system.

"In the past three years the cost of building and running water treatment plants in Australia increased by 47 per cent. Water treatment now costs every household $60 of the $365 they spend on average on water supplies each year.

"Higher standards of water treatment would push that figure even higher. It is unlikely that the community would be well served diverting community funds into additional water treatment for no benefit to public health."

Some 600 families in Melbourne's eastern and south eastern suburbs took part in the Monash University study. Each family had a water treatment unit installed in the kitchen. Only half of the units worked - the other half were dummy units delivering normal tap water. The families and the research workers did not know who had the real treatment units and who had the dummies.

Each family kept detailed health diaries recording any cases of gastroenteritis. The research team found 2,669 cases of the disease over 16 months. There was virtually no difference in the level of gastroenteritis between families with the real and dummy units.

In its conclusions, the research team headed by Associate Professor Kit Fairley wrote: "We found no evidence of waterborne disease in a city with a chlorinated unfiltered water supply drawn from a protected catchment".

Dr Langford said the Melbourne research would be closely studied throughout the world because it switched the emphasis from measuring bacteria to measuring health..

"Many cities are looking at their water quality as new testing techniques detect ever smaller numbers of micro-organisms in urban water supplies," he said.

"What Dr Fairley and his researchers have established is that we should be looking at the health benefits of new water treatment technologies, not just what they remove from the water."

The Melbourne study was supported by: The Cooperative Research Centre for Water Quality and Treatment, Water Services Association of Australia, Department of Human Services Victoria, Melbourne Water Corporation, South East Water Limited, Yarra Valley Water Limited and City West Water Limited.

Associate Professor Kit Fairly can be contacted at the Monash University (03) 9903 0550

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