A unique environmental group created by an $8 million donation from Allied Chemical Corp. stemming from Kepone pollution in Virginia, has decided to focus on the issue that begat it - the impact of toxic substances on humans.

Gerald P. McCarthy, executive director of the Virginia Environmental Endowment, said yesterday that the board of the private, nonprofit endowment had concluded after a weekend meeting that a concentration on toxic substances was "consistent with our origins."

The endowment will exclude Kepone-related activities from its grant programs on toxic substances until the state of Virginia and Allied can reach agreement on the cost of cleaning up the pollution caused by the highly poisonous Kepone, an insecticide ingredient. "We are definitely interested in Kepone and we feel we should do what we can, but we will defer any action on Kepone activities until a settlement is reached," McCarthy said.

The endowment was created in an unusual process which saw U.S. District Judge Robert R. Merhige first fine Allied $13.2 million for illegally discharging Kepone and other chemical wastes into the James River at Hopewell, Va.

Merhige later cut the fine to $5 million after Allied, following the judge's suggestion, agreed to donate $8 million to a fund to "enhance the quality of Virginia's environment."

Even with the reduction, it was the largest fine imposed in a federal pollution case and Allied still faces costs which may arise from the negotiations with the state and from civil suits involving injured workers and fishermen.

The Kepone problem was discovered when workers at a small plant owned by Life Science Products Co. Inc., developed severe nerve disorders. Life Science had taken over production of Kepone from Allied in 1974 and continued to make it until July, 1975, Allied which had made Kepone in Hopewell from 1971 until 1974, pleaded guilty to 340 counts of dumping wastes in the river in those years. Life Science and several of its officers have also been fined in the case.

High concentrations of Kepone, which has caused cancer in the test animals forced the closing of about 100 miles of the James River to fishing.

McCarthy said the endowment now plans to use the interest from its $8 million - "a conservative estimate of $400,000 a year - to finance its activities. The money is now invested in U.S. Treasury bills.

The endowment hopes to make its first grants by December, he said. "We want to multiply the money as much as we can so we will be looking for" proposals where matching grants can be obtained, said McCarthy, former chairman of the Virginia Council on the Environment. "I hope as word gets out we will receive a number of proposals."

McCarthy said the endowment had decided to work largely through grants to other groups or individuals, keeping its staff small. He said one area of interest is environmental law and that funds might be provided to law schools in the state or to students for development of that field.

"We will take an active approach and not just sit back and wait for things to come to us," said McCarthy, who is 34.

McCarthy said the endowment will not work like the Arlington-based Nature Conservancy, which buys and protects environmentally endangered land throughout the country. The board considered "everything from wetlands on the Eastern Shore to stripmining in Southwest" Virginia before settling on its present course, he said.

"We want to get the word out to people so that they know what we are interested in. If they are trying to preserve a scenic vista in the Blue Ridge then they would be wasting their time with us," McCarthy said.