Environmental issues received international attention on two fronts yesterday with release of an eight-year study by the North Atlantic Treaty Organization of hazardous waste and a gathering of environmental activists from 28 countries.

Friends of the Earth International, which claims 95,000 members worldwide, announced agreement on its member organizations' five top issues. Not surprisingly, the delegates said the most pressing is the possibility of nuclear war.

Next on the list are pressures on worldwide air and water from the burning of fossil fuels, extinction of plant and animal species, decline in agricultural production because of deforestation and topsoil loss and health dangers in food from pesticides and chemical additives.

Denouncing the spread of nuclear power and weapons, the group said three major antinuclear demonstrations are planned Saturday in Bonn, Oct. 21 in Amsterdam and Dec. 6 in Brussels to pressure NATO and the United States against planned deployment in Europe of Pershing II medium-range ballistic missiles, cruise missiles and neutron warheads.

The NATO symposium on hazardous waste, which involved 300 European and U.S. participants, applauded its new 12-volume study as a technical resource and planning guide for all of the member governments.

Dr. Bernd Wolbeck, a West German nuclear physicist who directed the research team, said there was general agreement on the need for stringent regulation of wastes and for detailed notification whenever toxic wastes crossed international boundaries.

The U.S. system requires waste exporters to provide four weeks' notice to the State Department, which then notifies the receiving country. Wolbeck said the report did not recommend that any nation curtail exports on grounds that would infringe national sovereignty.

The study's 84 recommendations and 55 conclusions included a call for cradle-to-grave waste management, tight regulations on siting and construction of disposal facilities and a trip-ticket system spanning all of Europe.

The report also advocated restricting underground disposal in mines or salt domes to the most toxic wastes for which there is no possible use. It said recycling materials extracted from waste chemicals should be a top research priority. "One man's waste is another man's feedstock," Wolbeck said.

NATO already has set up a permanent committee to track developments and provide information to member nations on waste disposal methods.

The environmental groups said evidence is accumulating that the "global commons" of the oceans and air is threatened worldwide by acid rain and a buildup of carbon dioxide, both side effects of widespread carbon fuel burning.