The Occupational Safety and Health Administration has cited Dow Chemical Co. for two "serious" violations in the production of phosgene, one of the most dangerous chemicals made, at its La Porte plant.

In one violation, a "quick-opening" valve was improperly in use. If it had been closed accidentally with a quarter-turn, it could have caused an explosion and lethal release of chlorine, the federal agency charged. Chlorine is an ingredient of phosgene.

The citations are the first local results of a continuing series of special inspections by OSHA at chemical plants that handle highly toxic substances.

The program was launched early this year in response to concerns about toxic gas leaks after more than 2,000 people died in one incident at a Union Carbide plant in Bhopal , India, and another leak at a Union Carbide plant at Institute, W.Va., sent 135 residents to hospitals.

In contrast with OSHA's usual routine of regular plant-wide examinations and accident investigations, the special inspections involve close attention to all aspects of the handling of selected chemicals that can pose serious immediate hazards.

The chemicals are being investigated one at a time. Phosgene was picked as the first for study in the Houston area because it is the most hazardous substance produced here, according to a ranking system being used by the agency, said Gerald Baty, OSHA area director.

The inspection at Dow's La Porte plant lasted from Jan. 29 to March 5, Baty said. Besides the "quick-opening" valve, it found one other violation that OSHA rates as "serious" - inadequate safety showers for workers to wash off toxic chemicals after accidents. The agency is proposing fines totaling $980.

OSHA also said Dow failed to comply with a number of "right-to-know" requirements for providing workers at the plant with access to their medical records and information about chemical hazards.

Dow spokesman Tim Scott said the company questions the classification of the two violations as "serious," but has already corrected both. The company has requested a conference with OSHA officials to present its view of the regulations, Scott said.