A Prince George's County police officer who disposed of thousands of used buoy batteries containing poisonous mercury for the Coast Guard was indicted yesterday by a county grand jury for allegedly violating state environmental laws by transporting the hazardous materials without a license.

Charles Edward Lanier, a 13-year member of the force, was charged with violating state law that requires certain security precautions when handling such materials. Lanier's company, C&G Services, was charged with unlawful transportation of about 6,500 batteries containing corrosive contents, toxic mercury and other hazardous materials.

Elizabeth Volz, supervising attorney for the Maryland attorney general's environmental crimes unit, said the charge against Lanier is a misdemeanor carrying a maximum penalty of one year in jail and a $25,000 fine. Lanier's company can be fined up to $100,000, Volz said.

Lanier, 35, could not be reached for comment yesterday. Lanier, whose company was hired by the Coast Guard to dispose of the batteries, told The Washington Post late last year that he did not initially know the batteries were hazardous.

Cpl. Bruce Gentile, a county police spokesman, said that Lanier, who works in the burglary prevention section at Seat Pleasant, would not be reassigned and the department would conduct its own investigation, Gentile said.

Lanier dumped the batteries between April 1984 and January 1985 in a yard between his father's house and his former wife's house in Cheltenham, a community in southern Prince George's County, according to the indictment. Lanier was not licensed by the state to dispose of hazardous waste, Volz said.

After the state discovered the dump site last December, health officials advised families in the area to have their children tested for mercury poisoning, a condition that is usually not fatal but can result in loss of memory, insomnia, headaches and muscle tremors.

Assistant Attorney General David Li, who presented the case to the grand jury, said that none of the children tested positive for mercury poisoning. Li also said that water wells in the area "came up clean" when tested for mercury and other hazardous materials.

But soil in the area where Lanier dumped the batteries had abnormally high traces of metal, Li said, and the Coast Guard removed about 140 cubic yards of soil.

The Coast Guard paid Lanier $15,024 to dispose of the batteries, which he hauled from the Coast Guard industrial yard at Curtis Bay in Baltimore to his father's property at 10800 Frank Tippett Rd. The Coast Guard later paid $150,000 to clean up the site.