With a single sweep of the regulatory hand, the Environmental Protection Agency has cut in half the amount of toxic chemicals that are released into the air, soil and water from industrial plants.

It's not that the volume of chemical pollutants is any less, but as of Thursday some 12 billion pounds - nearly 54 percent of all toxic chemicals released in 1987 - no longer are considered toxic.The EPA on Wednesday officially declared sodium sulfate as not posing health concerns that warrant it being in the company of such toxic chemicals as sulfuric acid, chlorine, lead and a variety of carcinogens.

The chemical, which is widely used as an agent and byproduct in a variety of manufacturing processes including the production of paper, glass and detergents, dominated the statistics announced recently on toxic chemical releases from industrial facilities.

It was the reason that chemical discharges released into water dwarfed releases into the air and soil; it was why California was ranked as the state with by far the greatest amount of toxic chemical releases; and it was why the total volume of releases nationwide exceeded 22.5 billion pounds instead of closer to 10.5 billion pounds.

The reclassification of sodium sulfate may be only the first of several such actions. The EPA also is reviewing whether two other chemicals high on the toxic release list - aluminum oxide and ammonium sulfate - should be taken off the list.

Aluminum oxide accounted for 2.4 billion pounds of toxic chemical releases by industry in 1987, nearly 11 percent of the total, and ammonium sulfate accounted for 918 million pounds, about 4 percent of the total, according to the EPA.