High Lead Levels Found in Australian Rainwater Tanks
by Warren McLaren, Sydney on 04.30.08
Australia has been in the grip of a one-in-a-thousand-year drought. A while back we looked at how this was affecting the ability of cities to provide basic drinking water services and what it meant for agriculture. Then we perked up with stories on how individual Australians and their municipalities have again embraced rainwater harvesting. With gusto. (Governments have even being giving rebates for tanks.)
Unfortunately new report somewhat rains on that parade. According to a study released last week a third of the Melbourne suburban rainwater tanks studied had heavy lead levels, above the Australian drinking water guidelines. Researchers from Melbourne Monash University and the CSIRO also found traces of heavy metals such as cadmium. Damn.
At this stage they’re not sure of the source, but several theories are being postulated. Such as residue from the lead that was in car fuel until relatively recently. Maybe lead flashing on roofing or lead solder on pipes.
Rainwater tanks have mostly been encouraged by water utilities for washing clothes, flushing toilets and water gardens but not for drinking.
Although researchers found that those drinking from the high lead content tanks did not have blood-lead levels of concern, they caution householders from such use until they can confirm where the lead is coming from. A warning especially true for families, as lead can lead to developmental delays in children.
However Professor Brian Gulson, head of the Technical Advisory Board of the LEAD Group had this to say on the matter: “Water filter systems can be helpful in removing lead from water, so if people are concerned about lead in rainwater they may wish to consider a filtration system rather than discarding their tanks."
As we've noted previously 20% of Australian homes now have a rainwater tank, and South Australia leads the pack with almost half of all its households sourcing some water from tanks. Via ::ABC
All zinc plated steel is going to leach some lead, as will solder joints as mentioned.
However, ,particulate fallout from coal fired plant emissions is the most likely source. Australia is big on coal right? Do their generating stations have emission limits for lead? Are they even required to report it?
all zinc-plated steel leaches lead? where's the lead come from?
You got me curious about the lead levels in zinc, so I found this:
PDF
Good to know.
Those are some impressive setups in the picture. Very clean and professionally done. Anybody know of companies here in the states that do that kind of work?
Not all rainwater tanks in Australia are of galvanised steel. Of those that are most come with a "food-grade polymer film" lining. Also on the market is large range of high density polyethylene (HDPE) tanks, as well as concrete tanks. There is also a hybrid version which is a steel tank, with a large separate polypropylene (PP) bag suspended inside.
In case you didn't open the PDF noted by 'superbad' above, here is some of the text regarding lead in glavanised steel:
"The first galvanized coatings contained as much as 1% lead. During the past 35 years, the presence of such high lead levels has not been common in galvanized coatings on steel sheet, at least not in North America, Europe, and Japan. Typical concentrations of lead (where it is intentionally used) in most galvanized sheet made during this time has been less than 0.15%, often as low as 0.03 to 0.05%. Even this lower amount of lead is still sufficient to develop dendritic growth behaviour during the solidification process. Today, a typical level of lead in the coating bath on lines where the product requires a well-developed spangle pattern is in the range of
0.05 to 0.10% lead.
As there are now environmental concerns about the use of lead, some galvanized sheet manufacturers have established practices on their older or low speed lines that use lead-free zinc, whereby a small amount of antimony is added to the zinc coating bath. Antimony influences spangle formation in a similar fashion to lead. The final result is a smooth, visibly spangled coating. Typically, the amount of antimony in the coating bath is about 0.03 to 0.10%."
See our recent post on Antimony.