Rainwater Users Warned Of Lead Risk
Nicky Phillips Original ⇒ HERE
PEOPLE who drink from their rainwater tanks may be consuming unacceptable levels of lead, a study says.
Scientists from the University of Technology, Sydney, assessed the quality of water stored in household tanks around the city and found that five of the 11 tanks contained lead levels exceeding 0.01 milligrams a litre – the amount considered safe in drinking water by the Australian Drinking Water Guidelines.
They also found the turbidity, or murkiness, of the water exceeded acceptable levels, as did the pH levels in some tanks.
A lead researcher, Benjamin Kus, said the results of their study confirmed past research that had also found rainwater tanks could accumulate higher than acceptable levels of lead and other pollutants.
According to the Australian Bureau of Statistics, 16 per cent of households use rainwater tanks, and more than three-quarters of them use the tanks as their main source of drinking water.
The scientists believe high levels of lead and murky water were making their way into rainwater tanks because not enough of the initial roof run-off was being discarded before water entered the tank.
The roof run-off, or first flush, was often the most polluted water and was collected in a pipe attached to the tank, they said.
Mr Kus said most first-flush devices collected about 12 litres to 20 litres of roof run-off but there were no exact calculations on how much first flush should be collected. He also said the exact source of the lead was not known.
In an additional study Mr Kus and his colleagues collected water that flowed into the tank from the roof to determine how much water needed to be bypassed before it was safe to drink.
They found that for an average roof – about 250 square metres – the first 1250 litres of water needed to be bypassed before the levels of lead and the turbidity of the water were acceptable for drinking.
According to drinking water guidelines, published by the National Health and Medical Research Council, lead that is absorbed into the body can make its way to the kidney, liver and bone marrow.
Lead is a cumulative poison that can severely affect the central nervous system, and can persist in bone for up to 30 years.
The implications of the study are especially relevant to people living outside metropolitan areas, where rainwater tanks are often the principal source of water.
More than 30 per cent of non-capital city households use rainwater tanks, according to the Bureau of Statistics.
In NSW there are no restrictions against the use of rainwater for drinking.
However, NSW Health recommends that, where available, people should use the public water supply for drinking and cooking because it is filtered, disinfected and generally fluoridated.
Maintenance of tanks is the responsibility of the owner or user of the tank.
A civil engineer and co-author of the studies, Jaya Kandasamy, said bypassing large amounts of roof run-off water was not ideal in drought-affected countries such as Australia, especially when households were installing rainwater tanks to conserve water.
Tank water should be treated or filtered, Dr Kandasamy said.
The study, published in the journal Water Science and Technology, found the levels of other heavy metals, salts and minerals in the tank water were acceptable for drinking.
Thanks Nicky Phillips
Old rainwater tanks used lead solder joints.
Many old metal roofs used lead headed roofing nails.
Fluorides and lead are a bad combination.
See also our site on ⇒ Lead in Aircraft fuel.