The gritty, eye-stinging, headache-producing air that enveloped the Washington area over the weekend has been superseded for the moment by a relatively breathable mixture. But the outlook, both near-term and long, is not good.
Temperatures for the next three weeks will be normal or above, according to the National Weather Service. High barometric pressures are likely and chances of rainfall are undetermined.
If the rain and clouds stay away those are precisely the conditions required for high concentretions of pollutants, mainly resulting from automobile emissions.
The long-term problem, however, is not weather.. It is the amount of potentially polluting material blown out through motor vehicle tailpipes daily.
According to Dennis Bates, environmental director of the Metropolitan Washington Council of Governments (COG), "There is a problem every day. Weather conditions only exacerbate it."
Bates' point is that there are always high levels of hydrocarbons and carbon monoxide being pumped into the air by cars, trucks, buses and motorcycles. But it takes the right weather conditions, including sunlight and heat, to convert the hydrocarbobs to photochemical oxidants, the major pollutant in the Washington area, which has not heavy industry.
Bates said the long-term outlook is bad because the number of miles driven by motor vehicles in the metropolitan area is rising each year and so is the number of individual trips.
The trip figure is important because more than 50 per cent of the air pollution caused by auto emissions results from cold starts and "boiling down" after the engine is shut off, Bates said.
Miles driven in the Washington area have increased from 38 million in 1972 to 41.8 million projected for 1977, an increase of 10 per cent. The number of trips in 1972 was 4.5 million and it is estimated at 4.7 million for 1977, an increase of about 4.5 per cent.
Pollution control devices on automobiles are part of the solution. Bates said, but these are not scheduled to go into full effect before 1983 nad then it would take nine or ten years for the fleet of cars in the area to turn over completely.
In the meanwhile, Bates added, COG is looking for ways to reduce pollution by controlling the use of cars in the area, but no decisions on how to do this have been reached.
The highest pollution reading in the area as of 3 p.m. yesterday was 34 at Suitland. It takes a reading of 100 from at least two of 11 recordinf stations plus the likehood that readings of at least 100 will continue for 24 hours for an alert to be called.
Last weekend's alert was the 26th since COG began measuring pollution in 1970. It was the 25th caused by photochemical oxidation of hydrocarbons. The other alert resulted from high carbon monoxide levels in the air.
The National Weather Service extended its air stagnation advisory until noon today, but cloudy skies have prevented the sunlight from oxidizing the trapped hydrocarbons so that pollution levels have remained relatively low.