Last week, a man drove 84 miles from his home in Bloomington, Ind., to the Country General Store run by Dottie McCord in Milton, Ky., a border town of 800 people on the Ohio River. His mission, McCord said, was to buy a big box of home laundry detergent containing phosphates -- a product banned in Indiana but perfectly legal in neighboring Kentucky.

Retailers in the District and Virginia may find a similar stream of Maryland customers seeking phosphate detergents, McCord predicted yesterday, when a ban in Maryland on the sale and use of detergents containing phosphates takes effect in December.

A Chevy Chase resident who swears his clothes get cleaner with phosphates will be able to walk a few blocks into the District where he can legally buy phosphate detergents.

Similarly, a Glen Echo resident will be able to make a quick trip over the Cabin John or Chain bridges into Virginia, where lawmakers earlier this year opted to study the effect of outlawing phosphate detergents rather than ban them.

The Maryland law carries a fine of up to $1,000 for using phosphate detergents. But environmental officials in Maryland, who lobbied for the measure as a means of restoring the health of the Chesapeake Bay, say they won't attempt to police lawbreakers, and they doubt there will be that many.

"Will we have a large force of inspectors at the state line? The answer is 'no,' " said William H. Eichbaum, assistant secretary for environmental programs for the Maryland Department of Health and Mental Hygiene.

"We are not going to be inspecting people's homes. It's unlikely that people are going to leave their neighborhood just to buy one item," he added.

Giant and Safeway, two of the area's largest grocery retailers, say they will pull their phosphate detergents off the shelves in Maryland by December. Doing so will cost Giant an estimated $250,000 in labor, computer and stock costs, according to Barry Scher, director of public affairs.

Of the 38 detergent products Giant sells, 25 contain phosphates, according to Scher. There is no difference in cost between phosphate and nonphosphate detergents of the same brand.

Phosphates are mineral nutrients added to detergent and cleaning materials for their cleansing properties, as well as to toothpaste, food products and agricultural fertilizers.

When they are found in sewage, however, they can cause excessive growth of vegetation in lakes and bays. The vegetation dies, decaying and depleting the water of oxygen, smothering fish and other aquatic life.

In the 1970s, six states -- Minnesota, Michigan, Wisconsin, Indiana, Vermont and New York -- along with the cities of Chicago and Akron, Ohio -- banned the sale of detergents containing phosphates. Like Maryland, Indiana also banned their use.

In Maryland, soap and detergent manufacturers' lobbyists swarmed over Annapolis this year to oppose the ban, arguing that phosphates are the only true answer for "ring around the collar."

Without the cleaning catalyst, they argued, homemakers would have to spend an additional $13 a year on fabric softeners, bleaches and energy for hotter wash water.

Advocates of nonphosphate detergents contend such claims are not true, and the proof is in consumer reaction in states where phosphate bans exist.

"The ban does not cause the people of Wisconsin to be unhappy," said Dr. Manfred Wentz, a professor of textile science at the University of Wisconsin.

Wentz, who has talked on dozens of radio shows about the phosphate ban in Wisconsin over the last five years, said, "Alternatives that do not contain phosphates do a very good job. Otherwise, all of Wisconsin would be up in arms."

Environmentalists also say that if clothes are less clean, that's not too high a price to pay for a healthy bay.

"No one can predict what a ban will do in terms of absolute specific results. But what millions and millions of dollars in research has shown is that controlling phosphorous discharges improves estuaries," said Will Baker, a lobbyist with the Chesapeake Bay Foundation, a nonprofit group dedicated to protecting the bay.

"The phosphate that comes from a farmer's field, the phosphate that comes from a factory pipe, the phosphate that comes from a sewage treatment plant . . . , there are controls on all of those," Baker said.

"This the ban is a mechanism to remove another major source of phosphorous," he said.

Under the new ban, about 30 percent of the phosphates now being discharged from Maryland's 350 sewage treatment plants will be eliminated, according to Baker.

By 1987, federal standards that take effect in Maryland will assure that 80 percent of the state's sewage flow will be treated to remove phosphorous before the effluent is discharged.

The Maryland ban exempts hospitals, veterinary clinics, laboratories and dairy food processors.

Phosphate-rich detergents, containing about 7 percent of the mineral, tackle dirt with vigor, according to the industry. The nutrient softens water, buffering it and maintaining the proper PH balance.

Dirt and other solids bond to phosphates like metal to magnets, its supporters maintain, and the dirt is flushed out with rinse water rather than being redeposited on clothes.

Robert Singer, a representative of the New York-based industry group, the Soap and Detergent Association, said that washing with a nonphosphate detergent, "may cause you to use more bleach, more fabric softener. And you may have to wash more often."

But Maryland environmentalists, noting that none of the state bans on phosphate detergents have been repealed, say consumers have adjusted to liquid detergents and other cleaning agents without phosphates.

"All you need to do is look at a box of Tide from New York, where phosphates are banned, and compare it with a box of Tide in Virginia, where they are not. The directions are the same -- the amount and temperature of the water, the detergent used," Baker said.

But there will always be people who swear by phosphates, said country store owner McCord.

She said that she sells the detegents to regular customers who travel 93 miles from Indianapolis and to an occassional phosphate junkie from Muncie, Ind., 110 miles from Milton.

"I'm a believer," she added.

"I had a smock top I thought was white, until I washed it with phosphates -- it about knocked my eyes out it was so white," McCord said.