LEAD IS among the ugliest and most damaging of pollutants. Some pollutants -- ozone, for example -- cause irritations that are temporarily unpleasant but generally lift when the wind changes. The effects of lead in the air and water are insidious and irreversible. Among other consequences, it can cause sharp reductions in the intelligence of growing children.

The chief source of lead in the air, and in most places the only source, is gasoline. The Environmental Protection Agency has been considering whether to ban leaded gasoline altogether. New standards going into effect Jan. 1 will squeeze the volume of lead in motor exhausts down to less than 1 percent of the volume before the attack on it began 15 years ago.

The EPA argues that leaded gas will soon fade out of most markets. The agency has decided to allow refiners to continue to sell it with the lead restricted to a tenth of a gram per gallon, because some engines still in use, especially in farm machinery, depend on the lead for valve lubrication. With the coming restrictions, leaded gas will cost more than unleaded and will begin to disappear from most filling stations.

That's a reasonable argument, but not quite good enough. While leaded gasoline is disappearing as a danger to the general population, there are still circumstances in which it will threaten some people -- children and pregnant women, for example -- who may live near old engines as they still chug away. Leaded gasoline is a real menace, and it ought to be banned outright.

Lead gets into drinking water chiefly as it is leached out of the pipes through which it travels. The present maximum permissible for drinking water is 50 parts per billion of lead. The EPA intends to reduce that standard to no more than 20 parts per billion, and probably less than that, by the middle of next year. But the quarrel now is over the responsibility for the substantial costs of replacing lead plumbing. Some of the EPA's critics want it to put that responsibility on local water authorities. The EPA replies that it doesn't clearly have the authority to make a municipal water department, or a private water company, correct the faults in plumbing in other people's buildings.

At several schools in Washington, for example, preliminary tests show that water in the drinking fountains contains 90 parts per billion of lead. That's intolerable. But who is going to bear the cost of the cleanup -- the city as water supplier or the school board as owner of the buildings? And what about private houses and apartments? Is it the city's responsibility to replace pipes, or the owner's? Those questions may have to go back to Congress for an answer.