A synonym for "leaden" is "dull," but the problem of lead in the environment is fascinating. It is a childhood health problem that illustrates how society's hazards are often distributed regressively -- persons lowest on the social ladder have special handicaps for climbing.

Recently the Reagan administration moved to strengthen restrictions on lead additives in gasoline. Although different refiners have different interests, this was basically a victory for environmentalists over industry. One refinery blamed the decision on "politics." Well, yes: politics is the assignment of social values and costs in accordance with a concept of equity. The Republican role in God's plan may generally be to lighten regulations, but this case illustrates how strong government can serve conservative values.

America uses 1.3 million tons of lead annually; 600,000 tons of this useful, ubiquitous and toxic metal are released into the environment. Because of high metabolism rates, children are especially susceptible to lead poisoning, which can cause retardation, brain damage, anemia, seizures, hyperactivity and death. Analysis of polar ice layers suggests that lead in the environment has increased 200-fold since industrialism began.

People are exposed to lead from food, household dust and the air. Burning a tankful of gasoline emits, according to one study, up to two ounces of lead. Upwards of 28 million buildings have lead-based paint, which tastes sweet to children. A flake the size of a fingernail can be damaging. Some pre-1950 houses have paint with 100 times more lead than is now permitted. Lead in paint is the most dangerous source, but reduce lead in gasoline and you will reduce lead in children. The mean blood-level of lead in children has declined 25 percent since the beginning of restrictions on lead in gasoline.

According to one study, 4 percent of preschool children have excessive levels of lead in their blood. That would be dismaying enough even if the distribution were geographically, and hence socially, even. But high lead concentrations are among the things that, say, Shaker Heights and downtown Cleveland do not share equally. The percentage of black preschoolers with excessive lead levels is six times that of white preschoolers. Other studies indicate excessive levels in one-fifth of black children from low-income families.

Children often are deficient in iron, calcium and zinc. Poor children are especially apt to be deficient. The more deficient children are, the more apt they are to absorb lead. Federal budget cutting and recession-related reductions of local revenues have reduced programs for screening for lead poisoning in children, and for removing lead-based paint from old buildings. Philadelphia's health commissioner says that if the city loses 10 percent of its lead-poisoning detection funds, that means 200 fewer homes visited, and five more cases of retardation. Studies have found correlations between even relatively low elevations of lead blood-levels and measurable reductions of IQ.

Any childhood disease that threatened affluent children as lead poisoning threatens poor children would produce public action faster than you can say "swine flu." As things are, government spends upwards of $1 billion annually on children with lead poisoning, 80 percent on special education for the learning-disabled.

Conservatives dissolve in admiration for this insight: "There is no free lunch." It means: someone must pay for anything that has costs. That, although hardly a sunburst, is true enough. So is this: society shall pay (for example, with slightly higher energy costs) for reducing lead use; and society shall continue to pay a lot (for injuries to its human capital) if it does not reduce lead use.

In Saul Bellow's most recent novel, "The Dean's December," a scientist offers "the real explanation of what goes on" in slums: "Millions of tons of intractable lead residues poisoning the children of the poor. . . . Crime and social disorganization in inner-city populations can all be traced to the effects of lead. It comes down to the nerves, to brain damage."

The dean thinks: "Direct material causes? Of course. Who could deny them? But what was odd was that no other causes were conceived of." The dean is properly dubious about thoroughgoing materialism, that neglects society's cultural, spiritual ingredients. But the body is not just a temple in which the mind rattles about; the mind is not a ghost in a machine.

Mind is grounded in matter, woven into our physical constitutions. Conservatives, who rightly prefer equality of opportunity to equality of outcome as a social goal, have yet to come to terms with how complex and elusive their goal is, in light of all that we are learning about social influences on human capacity.