For the first time, an order to take a look at indoor air pollution has surfaced in the debate over the Clean Air Act.

The latest draft of the administration's rewrite of the law, now circulating on the Hill, would order the Environmental Protection Agency to study the problem for two years.

It is the first sign of official attention to a spate of scientific reports expressing concern that the air inside homes, schools and offices may be much more foul and cause much more illness than the air outdoors. Some studies blame indoor air pollution, particularly by radioactive radon gas, for as many as 10,000 cancer deaths every year.

The pollution is radiation from building materials and vapors from household solvents that clean ovens and dissolve grease. It is cooking and heating gas and the by-products of burning that gas, as well as formaldehyde and other chemicals that leak from insulation, wallboard, fiberboard and synthetic fabrics. It is pesticides on the philodendrons and cigarette smoke everywhere.

In all, it is drawing new attention as a possible cause for everything from workers' Monday-morning blahs, headaches and winter colds to miscarriages and death from cancer.

The Aug. 20 draft legislative language would instruct EPA to report within two years on indoor air pollutants--their sources, strengths and health effects--and the costs and benefits of options in reducing those risks. EPA officials have refused to admit that any of several current drafts represent the language they will ultimately push, but agency spokesman Byron Nelson said regular pollutant research could easily be modified to include studies of indoor buildup.

Most Americans spend 70 to 90 percent of their time indoors, but rooms full of murk only became a problem recently as people began sealing up drafty buildings to save energy. Before that, most homes and workplaces changed air every hour. Now it may be five to 10 hours or more before open doors and the remaining cracks provide a new air supply, according to most of the studies.

Building standards, which generally date from the 1930s, were set up to deal with accumulating body odors and stuffiness rather than chemical pollutants. They also assumed construction technology that left a few leaks.

Now, however, new buildings and most renovations are all but hermetically sealed with triple-glazed windows, doubled insulation and weatherstripping, and paradoxically may be saving fuel at the expense of public health.

The National Association of Home Builders Research Foundation built just such a snug home in rural Mount Airy, Md., last year and bragged that the one-story building could be heated with a hair dryer. But the air inside soon began making visitors' eyes water.

Tests found high levels of formaldehyde gas and radioactivity approaching 100 times the outside background level. Formaldehyde compounds--used in plywood, fiberboard and some kinds of insulation--were evaporating into the house and staying there. The gases cause dizziness, watery eyes and noses, difficulty breathing and headaches for sure, and some disputed studies have linked formaldehyde to cancer in laboratory animals.

Foamed-in urea formaldehyde insulation went into more than 125,000 homes last year, but the ensuing wave of health complaints led to its being banned in Massachusetts. Cautionary labels on other formaldehyde construction products are already required there and in Colorado and Minnesota.

Radioactivity in the model home was coming from the decay of a gas called radon, which results from the decay of minute particles of uranium that are everywhere on earth. Radon 220 and 222 seep out of the earth in foundations, from brick walls and from ordinary water, occurring more in some places than others. Usually the radon blows away before it decays much further.

In the Mount Airy home, however, the radon was trapped and built up long enough to begin decaying into its "daughters," which are what cause the problem. The radon daughters cling to dust motes in the air and put out short-range alpha particles, which can damage lung tissue if the dust is inhaled.

"According to standard EPA risk estimates for radiation, if the U.S. population lives and works in buildings with one air change per hour, the radon decay products in the air will cause about 10,600 fatal lung cancers per year," alleges a working document on radon circulating within EPA. That would equal about 10 percent of known lung cancers in 1979, the paper said.

It added that the number of cancers could jump to 70,000 if all the buildings had an air change only every five hours.

A tightly sealed solar-heated home in Maine that used high-radon granite for heat storage was measured at radon levels so high, the study said, that "if four people lived in such a home their whole lives, there is more than a 90 percent chance that at least one of them would die from lung cancer caused by radon."

But most people do not live or work in such tightly sealed buildings, even those who have weatherstripping and storm windows. In addition, some authorities question the research figures.

The National Academy of Sciences reported after a two-year study recently that indoor air quality is a matter of "immediate and great concern," but noted that firm data relating indoor pollution to actual illness are lacking.

The studies on radon effects particularly need reinforcement, but the fact of radon buildup is clear, the report said. "Codes for new construction may be necessary to prevent the occurrence of high radon concentrations in modern or refurbished dwellings," it said.

Three of the seven pollutants that EPA regulates outdoors may be more of a hazard indoors than out, even without super-tight construction: carbon monoxide, soot particles and nitrogen dioxide. All are products of the burning of fossil fuels, and they come out of kitchen stoves and home furnaces, space heaters, wood stoves and gas clothes dryers.

As people turn down thermostats to save energy, heaters work less efficiently and produce more pollution, just at the wintry moments when ventilation is least welcome. A 1978 study of 5,800 children in Britain found more colds and bronchitis and weak lung action among children living in homes with gas stoves. And, of course, smokers--33 percent of the population--provide most buildings with additional doses of all three pollutants.

Buildings above underground garages have been linked to headaches and fainting from carbon monoxide. Rates of it four times higher than the law allows outdoors have been reported at several indoor ice skating rinks that use gasoline-powered ice resurfacing machines, the NAS study said.

A workshop of the Society for Clinical Ecology found last year that office air is frequently full of metal and paper bits, motor fumes, copier and ink vapors and cleaning fluids, as well as smoke. The legendary Monday-morning office slump, in other words, may be less a product of stiff weekends at home than the fact that pollutants built up in the office while nobody was around to open and shut the doors.

Many of the problems can be solved with simple fresh-air ventilation, which ought to be provided in modern air-conditioning and heating systems but sometimes is not. Heat exchangers often cure the trouble: they pump incoming fresh air one way and stale air out the other way through channels that share a common wall, allowing the fresh air to become the temperature of the stale air.

That worked at the Mount Airy home, where a $300 heat exchanger cleared up the pollution.

Some pollutants like radon and pollen dusts, however, may also be present outdoors and might require air cleaning as well as simple exchange, the NAS study said. Some pesticides are used indoors when they should not be, and many solvents, paint thinners and household cleaners are used in closed spaces despite labels limiting their use to well-ventilated areas.

The EPA study is expected to check which agencies might best deal with indoor air pollution, as well as with the headache of enforcing any new rules. But any regulation would have to involve local building inspectors, and the current regulatory climate is such that few people predict much chance for any other federal action for the time being.