Lead is the one contaminant in water that genuinely worries all water scientists. American research, published a decade ago and once regarded as cranky, is now widely accepted. It showed that the intellectual development of young children is harmed by levels of lead in their body that are typical in some parts of both Britain and the US. In 1987, British researchers reached the same conclusion when Dr Mary Fulton of Edinburgh University, in a widely admired study for the Medical Research Council, of 500 typical children in that city, found those with the most lead in their blood did significantly worse in school tests than those with lower levels. 'There is no evidence of a safe level,' the researchers concluded.
Scientists in Britain and round the world have derived from these findings a 'provisional tolerable weekly input' of lead for young children of 25 micrograms per kilogram of body weight, says John Fowell of the Water Research Centre (WRC).
In Edinburgh and many other cities with a lead problem, more than half of the lead that children ingest comes out of the tap, mostly absorbed by water in lead pipes inside their own houses. In such circumstances, says Fowell, bottle-fed babies are at special risk.
Scientists have devised the new WHO limit to safeguard those babies from permanent brain damage - affecting speech, memory, concentration and learning. Unless financial considerations take precedence over the medical, it will be set at around 10 micrograms per litre of water, says Derek Millet of the WRC. The current EC limit is 50 micrograms.
Lead has been a known hazard in tap water for many years. For more than a decade, water authorities in vulnerable areas of Britain have been removing their own lead piping and dosing their water with chemicals to reduce its propensity for dissolving lead from pipes. The campaign has been most intense in Scottish cities such as Ayr and Glasgow, where evidence of acute poisoning has been found in the past. More recently in Blackburn the local authority has publicised grants to remove lead pipes. Scientists think other Lancastrian towns should have done so too.
Many houses in the Manchester area receive soft water from Lake District reservoirs and are served by long lead pipes that deliver water to several houses, which means that the water spends a long time in contact with lead. But now it is clear that, if water is to be safe, much lower levels of lead in tap water are necessary than was previously believed - which can only be achieved if there is a national programme to remove all domestic lead plumbing. There are probably around four million homes in Britain with plumbing made from this metal; the total cost of removal could run to billions of pounds.Reuse content