In his campaign manifesto Dr Millstone says that the "safe" limit set by the British government in 1983, of 25 micrograms of lead per decilitre of blood, is far too high. "Current research shows that a level of only 10 micrograms per decilitre is causing measurable harm to the mental development of young children," he says. Apart from causing behavioural problems, lead can damage the brain and central nervous system, the liver, kidneys, bones and blood. It is particularly damaging for children under seven, whose brains and organs are still developing, and for pregnant women, who can pass the poisoning on to the foetus.
Old lead water pipes are the best-known source of lead pollution - the water flowing through the pipes dissolves the lead and delivers it straight to the kitchen tap. This hazard is most significant in soft water areas such as Glasgow, Edinburgh, Liverpool and Manchester, where high levels of juvenile delinquency have been linked to lead.
Ian Parker, a building surveyor who has studied the problem of lead poisoning and buildings, has compared data on lead intake with crime figures. He has found startling geographical correlations between high lead absorption and civil disorder. "Can it be a coincidence," he asks, "that Glasgow has the most severe inner-city delinquency and vandalism, and also the highest monitored lead levels of any European city?"
In hard water regions, such as London and the South-east, limescale build- up inside water pipes cuts down the amount of lead dissolved. But even in these areas high lead levels can be detected in children's blood, and this despite a dramatic drop in airborne lead following the introduction of unleaded petrol.
Dr Millstone suggests that lead paint, especially in poor or badly maintained housing, is far more of a risk than has been realised. He thinks that around half of all British homes are contaminated.
Professor Ian Thornton, of London's Imperial College, agrees. Most house dust, he points out, is composed of degraded building materials, and the older the house, the greater the proportion of lead there is in the dust. Professor Thornton has studied lead contamination in a sample of 5,000 homes in one London borough, and has found that: "A major contribution, if not the major contribution, was lead derived from paint." He, too, is concerned that existing exposure limits are too high: all "safe" levels, he believes, are arbitrary. "We just don't know for sure what is really safe," he says.
Public awareness of the dangers of lead contamination in housing is much lower here than in the US, where lawyers advertise their services for lead- poisoning compensation claims, and landlords and estate agents issue disclosure notices drawing tenants' attention to the possibility that lead paint is present in their properties. These practices seem likely to cross the Atlantic very soon.
But if lead is so dangerous why was it ever used in the first place, and more importantly why did lead paint continue in domestic use in Britain until 1992? (Lead paint was banned in Australia in 1906 and in the US in 1978.)
The answer is that lead gives qualities to paint that no other material can do. Lead compounds were valued as pigments and for the hard-wearing qualities they gave to the finished paint. Lead carbonate is a white powder, used to give the bright white colour to old gloss paints; it also helped the paint to dry quickly and contributed to its hardness. It comprised up to half of the volume of some paints, and is therefore present in huge quantities on the woodwork of millions of homes. Red lead oxide was used in the traditional pink wood primers and dark red metal primers. It is no longer used, but paint manufacturers still add a pink dye to some wood primers; the red colour of metal primers is now mostly iron oxide, also with a touch of red dye. Lead naphthanate was used in many types of paint as a drying agent - without it, the paint would remain sticky and soft.
Paradoxically, although the health dangers of lead have been known for more than a century, increased appreciation of its qualities by the paint manufacturers over the years meant that lead became used more rather than less. So, although Victorian houses may have accumulated the greatest amount of lead from paint over time, the highest actual lead content in paint occurred between 1930 and 1955, so many post-war homes contain significant levels. It is the presence of all this lead in crumbling paint layers in old houses which is now a major source of poisoning for many children.
Apart from lead in water, danger to children comes from three main sources:
q "Pica", the habit that babies and children have of chewing objects and surfaces. In a building with loose or flaking paint, a child may easily swallow a paint flake weighing 10 milligrams and thus ingest five mg of lead, a very high dose.
q Burning-off or sanding paintwork while the child is present. High levels of lead can be absorbed by breathing in the fumes or dust.
q In old buildings with high lead-laden dust levels, children may be contaminated by contact with dust on floors or other surfaces.
Dealing with lead paint depends very much on individual circumstances. The first step is to find whether lead paint is present. The Paintmakers Association produces a test kit, which can be bought from branches of McDougall Rose, the decorating chain. It costs pounds 14.99 and can be used for 20 tests. B&Q sells a smaller kit for pounds 2.89, which can be used for two tests. Both kits use a simple swab method, a colour change indicating the presence of lead. It is important to scratch through the surface of recent paint to expose older layers underneath.
If a test shows your home does contain lead paint you will then have to choose between removing it or sealing it in. Removal can be costly, since the paint can neither be burned off nor dry-sanded. Chemical paint strippers such as Nitromors are the preferred option, but low-temperature hot-air guns and wet abrasives can be used with care.
The British Coatings Federation, a paint industry trade body, produces two leaflets advising on the safe removal of lead paint; one is for householders and the other for professional painters. Despite publishing the leaflets, though, the BCF does not generally encourage removal; it recommends that where the paint surface is in sound condition, it should be sealed in by overpainting. But, as BCF spokesman Ray Leggetter stresses: "The householder then has a responsibility to maintain the paint in good order."
Other experts feel that overpainting is no answer; as with hidden asbestos, it is simply passing on the problem of removal to future generations. If you do choose to overpaint then you may feel you have a responsibility to label the new paint finish, warning future occupants that a dangerous neurotoxin lurks beneath the surface. This is the purpose of the disclosure notices being issued in the US - to guard against legal action from future tenants or owners.
Lead poisoning - the facts
q One-third of British homes receive their drinking water through old lead pipes.
q Half of Britain's homes contain dangerous levels of old lead paint.
q Lead is highly toxic, especially to children under seven.
q Effects include reduced intelligence, reading and learning disabilities, hyperactivity and behavioural problems.
What to do:
q Ask your water supply company and environmental health department if it operates a lead-testing service.
q Let tap water run cold before using for drinking or cooking.
q Contact the campaign to reduce domestic lead pollution at the Science Policy Research Unit, Sussex University. Tel: 01273 877380.
q Obtain a "Lead Test" kit from McDougall Rose decorators' suppliers, or a "Lead Check" kit from B&Q.
q Obtain advice leaflets from the British Coatings Federation. Tel: 01372 360660.
q Families with young children should never dry-sand, power-sand or burn off old paint. Young children and pregnant women should be kept away when old paint is being prepared for repainting.Reuse content