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The lead "scare" began in 1974 when Michael Moore, a doctor based at the University of Glasgow, found widespread poisoning of Scottish families from lead plumbing. Children in Glasgow were twice as likely to be mentally retarded if the lead in their home tap water exceeded World Health Organisation limits, which half the city's tap water did. Soon afterwards, American researcher Joseph Needleman of the University of Pittsburgh began to turn up evidence that even low levels of lead pollution appeared to cause poor educational performance and psychological problems among children.

Ministers set up an interdepartmental working group and made palliative statements. It was government policy to "contain and where possible reduce" exposure to lead pollution, whether from tap water or - an increasing concern - lead in petrol fumes.

For two years the issue was sidelined into a DHSS working party, under Professor Patrick Lawther of St Bartholomew's Hospital medical college, which reported in 1980 that there was "no firm evidence that lead from petrol has caused harm". The line held until 1981, when a memo from the Government's chief medical officer, Sir Henry Yellowlees, was leaked. Forget the "no firm evidence", he said. His bestjudgement was that "some hundreds of thousands of children" were having their nervous systems and intellectual development damaged by lead.

The letter caused a public furore and triggered a government half-measure. Under pressure from oil companies, who said lead was essential in petrol to maintain vehicle performance, the government reduced by two-thirds the amount of lead in petrol. And it began a programme of chemical dosing of water supplies to reduce the amount of lead from tanks and pipes absorbed in tap water. Then it emerged that Germans were running their cars on lead-free petrol because lead poisoned the catalytic converters being introduced to reduce acid rain damage to that country's trees.

But it was only when campaigner Des Wilson launched a campaign against lead in petrol that the Government finally climbed down and forced industry to sell lead-free petrol and build cars that ran on it.

What about lead in water, which many experts regard as the main problem for a majority of the nation's children? Well, chemical dosing of water supplies partly worked. But only partly. To meet new tighter EU rules on lead in water may become the ultimate nightmare for ministers. The removal of lead plumbing from millions of British homes would have a price tag of many billions of pounds. It would be the plumbing equivalent of slaughtering the nation's cattle. FP