Pascal Renn, a 71-year-old dairy farmer, sold 500 prime agricultural acres 15 years ago to an aluminum smelting firm, thinking it would be a boon to his native county. Now, he says, he prays "every night I can do something to protect the community from this selfish company."

Renn's current concern is a proposed landfill in which the aluminum company, Eastalco, wants to dump brick that is laced with fluoride and cyanide residues from the smelting process. With citizens charging coverup, and the company hinting jobs are at stake, the battle over the landfill has been raging for months in this county of rolling dairy farms, Appalachian foothills and town house developments inhabited by Washington commuters.

It is the latest in a series of disputes over the years between Frederick County's largest private employer and its rural neighbors. In 1978, three families were awarded $65,000 in litigation arising from air pollution that they charged was poisoning their cows with fluoride gases.

"We want to be good citizens," Eastalco President Peter Aylen asserted here today. "We intend to fulfil our obligations."

County officials, who want industry but not controversy, have barred Eastalco wastes from the public county landfill, but say it's up to the state whether the company can operate its own landfill.

State officials held up approval of the landfill permit after citizens complained about possible effects on the environment and public health. Today, after several weeks of testing and analysis, they gave qualified approval to the company plan, describing as "innocuous" most of the waste the firm wants to dump.

Citizens attending a briefing here were assured that the plastic-lined landfill would contain all waste or, at worst, allow seepage that would contaminate wells no farther than 80 feet from the site, within Eastalco boundaries.

Officials limited their qualified approval to "old" brick that once coated the electrolysis cells where the aluminum smelting takes place. The material has been sitting uncovered on concrete pads for as long as eight years. The approval for now excludes fresh bricks and carbon residues, which also coat the cells or "pots," and sludges from settling ponds into which the chemicals now wash.

"We can't sit back in our aluminum lawnchairs, drinking out of aluminum cans, next to houses with aluminum siding" and refuse to handle the waste, said Ron Nelson, Maryland waste management administrator. The landfill, he said, represents the state of the art, but he refused a citizen's request to provide a "signed guarantee" that it would never leak.

Typical of toxic waste disputes nationwide, the Eastalco controversy is complicated by a lack of definitive answers to questions about the effects of chemicals and how much exposure humans can take without harm.

Against this backdrop, there is a "general mistrust between citizens, government and industry," Nelson said. The mistrust bubbled to the surface as Nelson reported the state's findings in the Eastalco case.

"I just don't believe them; it's just a lot of hogwash," Pascal Renn said after the two-hour presentation. His 84-year-old brother, Austin, also was skeptical. "There's a lack of confidence in anything Eastalco does in any part of our county, and in the state health department," he said.

The battle of Eastalco has brought together deeply rooted dairy farmers, such as the Renns, and newcomers such as Christy Carton, who moved here five years ago from Arlington to an old farmhouse on 20 acres three miles south of the plant. Carton, whose husband, Robert, works for the toxics section of the U.S. Environmental Protection Agency, has been spearheading the campaign at home.

She formed Concerned Citizens of Adamstown, which obtained 650 signatures opposing the landfill, and she consulted attorneys and environmental activists elsewhere in Maryland. "I've learned a lot about politics," said Carton, who came here, she says, to escape urban ills.

She learned of the landfill plans in January, almost by accident, and, all sides agree, was instrumental in forcing the state to take another look. "I doubt we would have made as full a report if the citizens hadn't asked some good questions," Nelson said after today's briefing.

Nelson was unable, however, to answer all the questions. He could not say that fluoride levels in the waste would not harm humans. Nor could he explain to everyone's satisfaction why the state hadn't moved more quickly to analyze the contents of other landfills that Eastalco has operated here for years, without any permit but apparently within the law.

"We're looking into four or five hundred sites" of all companies around the state, Nelson said. "You have to set your priorities. We're trying to catch up," he said.

Admittedly without proof, residents of the Frederick valley, where the 960-employe plant is located, suggest that Eastalco is directly or indirectly responsible for all manner of ailments. Eleven people, it is widely noted, have died from brain tumors, and three children from separate families in the vicinity suffer from bone diseases. Ponies and cows are said to have suffered.

"You go out and talk to the neighbors, you'll get all kinds of stories from us," said John Carnochan, Eastalco's community relations manager and former Frederick County school superintendent. "There's never been any evidence, but these stories persist in the minds of the people."