Cars and trucks are no longer the only major villains in the Washington area's war against air pollution, according to a new study by the Metropolitan Washington Council of Governments.

The polluters on the area's roads and freeways have been joined over the last decade by such stationary pollution sources as gasoline stations, laundries, and operations using paints and solvents, the study says. Autos in 1980 still produced more than half of the hydrocarbons and nitrogen oxides released into the area's skies, but that share is down from more than two-thirds in 1972.

Officials at the Council of Governments will use the study to prepare a five-year plan by the end of this year to further clean up the area's air. The area is under a federal mandate to reduce ozone pollution -- which is produced by the interaction of hydrocarbons and nitrogen oxide -- by 1987.

The plan may be influenced by study results showing that nearly half of automobile pollution occurs at the beginning and end of a trip rather than during the travel itself. This means that the council may concentrate on strategies to reduce the number of auto trips -- rather than their length -- as the best way of cutting moter vehicle pollution.

The new report focuses on two major pollutants -- hydrocarbons, which include compounds in automobile exhausts as well as evaporated gasoline -- and nitrogen oxides.

The council's researchers obtained their figures by studying traffic flows, incorporating state data on large pollution sources and conducting detailed statistical studies of smaller sites such as gasoline stations.

Total hydrocarbon emissions in the council's member counties went down 36 percent to 383 tons per day in 1980 from 598 tons a day in 1972. Total nitrogen oxide emissions went down less, to 412 tons a day from 477 tons a day. The figure for nitrogen oxides actually represents a 36 percent increase from 1976, when emissions stood at only 327 tons a day.

The jurisdiction of the Council of Governments includes the District as well as Arlington, Fairfax and Loudoun counties in Virginia and Montgomery, Prince George's and Prince William counties in Maryland. The District, with the highest population density, had the lowest figure for pollutants per capita at 0.34 pounds per day. Prince George's County dumps more total pollutants into the air than any other jurisdiction, with Montgomery second and Fairfax third.