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Study finds rainwater safe to drink -

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Study finds rainwater safe to drink

Nance Haxton reported this story on Wednesday, November 4, 2009 12:34:00

ELEANOR HALL: In one of the first studies of its kind, researchers have found that rainwater from
tanks is safe to drink.

Scientists from Monash University and Water Quality Research Australia studied 300 households in
Adelaide and found that there was no higher rate of disease for those using rainwater than for the
rest of the population.

The finding has important ramifications for health departments around the country, which have long
recommended that rainwater not be used for drinking, cooking or even showering, as Nance Haxton
reports.

NANCE HAXTON: Adelaide has the highest use of rainwater tanks in Australia.

Three hundred households with rainwater tanks were chosen for the study. All were given a filter to
treat the rainwater but only half had a real filter inside.

Over a year the volunteers were asked to keep a diary of any illnesses.

Associate professor Karin Leder says the results showed that the rates of gastroenteritis between
both groups were very similar and the same as for the rest of the population.

KARIN LEDER: Overall there were just under 770 episodes of gastroenteritis reported during the
study period which equated to a rate of gastro of 0.77 episodes per person per year. And
interestingly this rate is very similar to the rate of gastro that's been reported in other studies
both in Australia and in other industrialised countries amongst non-rainwater drinkers.

NANCE HAXTON: The varying microbial quality of rainwater has led many health authorities to
recommend that it not be used for drinking or cooking.

But associate professor Leder says their study shows that while there may be different microbes in
rainwater to mains water, they do not necessarily affect human health.

KARIN LEDER: As you can imagine, birds and small animals that might deposit droppings on the roofs
of houses as the rain passes down, those bugs can get washed into the rainwater tanks. That's why
there is a higher level of microbes and more variability in the quality of rainwater than of tap
water.

But the issue has been, or the unanswered question has been the fact that you can find bugs doesn't
necessarily mean that those bugs have any human health effects. So this study was really to
determine whether the variability in microbial quality equated to problems with human health.

NANCE HAXTON: Associate professor Leder admits that the study has its limitations, as people with
problems with their immune systems were not included and the study involved people already drinking
rainwater who may have built up their immunity.

The researchers also didn't look at chemical contaminants as those effects generally build up over
a longer period of time.

But she says they are confident that health authorities and the public can be assured that
ingesting rainwater when bathing or showering is unlikely to cause any health problems.

KARIN LEDER: I'd still caution that I think the main outcome of this is that I think we can safely
say that rainwater can be used for other household purposes, like in the bathroom, which again most
health departments don't actively encourage if there is a tap water supply. Whether or not it
should be used for drinking is perhaps not so important in terms of water conservation because the
amount of water used in the kitchen is relatively small.

NANCE HAXTON: So what recommendation will you be giving to health departments? Is it just that
rainwater can be used for household purposes or what sort of qualifiers will you be putting on
that?

KARIN LEDER: We would be concluding that rainwater used for non drinking household purposes is
safe. We would conclude that the potential for inadvertent or accidently ingestion of small amounts
of rainwater in other... in the non drinking uses of rainwater in the house can be encouraged. But
we wouldn't go so far as to say that health departments should change their recommendation with
regards to rainwater for drinking when there is an alternative tap water supply.

Because it cannot be guaranteed that all householders will comply with the recommended maintenance
measures, there will be ongoing variability in the quality of rainwater. So it will not necessarily
always be safe for drinking and as I say, if people have problems with their immune system they may
be more susceptible to illness. Because of these qualifications we would caution against just
generalising or saying that it's always safe to drink rainwater.

ELEANOR HALL: That's researcher Karin Leder speaking to Nance Haxton in Adelaide.