The air-quality police are at it again, this time lashing out at Mother Nature.

The Environmental Protection Agency says that oak trees in the Ozarks may be contributing to high levels of cancer-causing pollution in the St. Louis area. Trees haven't been under this kind of indictment since President Reagan, 20 years ago, stated that trees were worse polluters than smokestacks.

What happens, according to EPA, is this: Oak trees emit isoprene, which reacts with sunlight and moisture to create formaldehyde, a toxic gas blamed as a carcinogen. This, says the federal agency, may be why St. Louis air has among the higher levels of formaldehyde in the country. Of course, smog from auto exhaust and industrial emissions don't help.

To find out just how badly oak trees contribute to air pollution, researchers have installed air monitors in the woods southwest of St. Louis. The Ozarks forests of Missouri and northern Arkansas have some of the highest densities of oaks in the United States. Oak trees in the densely wooded Ozarks may produce up to 300 tons of isoprene per day, say scientists. They just don't know yet how much of that stuff gets turned into formaldehyde or how far formaldehyde will travel. But it makes for an ill wind in the St. Louis metropolitan area, scientists believe.

Scientists also don't know what to do about it, and here's where we may be able to help with a few suggestions:

• Invite chip mills back, with the provision that they clear-cut every oak tree south of the Missouri River.
• Replace the trees with other crops. Marijuana, although a top cash crop, probably should not be considered, because of the special kind of air pollution that weed causes.
• Move St. Louis to Arizona, where there aren't so many oak trees. After all, the St. Louis football Cardinals moved to Arizona a few years back.
• Install huge fans to blow the formaldehyde back into the Ozarks woods.

Meanwhile, until the EPA has time to determine exactly how much formaldehyde Ozarks oaks produce and develops a plan to deal with it, maybe St. Louisians should try not to breathe too much.