Phosphoryl trichloride. Documentation of proposed values of occupational exposure limits (OELs)

Abstract

Phosphoryl trichloride is a clear, colorless or yellowish liquid with an unpleasant, pungent odor. In contact with water or steam, it rapidly hydrolyses by releasing hydrogen chloride and phosphoric(V) acid. Phosphoryl trichloride is used in industry primarily for the production of alkyl and aryl triesters of phosphoric(V) acid. It is also used in the production of plasticizers, flame retardants, hydraulic fluids, insecticides, pharmaceuticals, gasoline additives and dye intermediates. Phosphoryl trichloride is also used as chlorinating agent, pH regulator, catalyst, solvent in cryoscopy, dopant for semiconductor grade silicon, and as reagent in laboratories. Phosphoryl trichloride is classified for acute toxicity as category 2 with inhalation (inhalation may lead to death) and as category 4 if swallowed (harmful if swallowed). In addition, it is classified as corrosive category 1A (causes severe skin burns and eye damage) and toxic to target organs due to repeated exposure, category 1 (causes damage to organs through prolonged or repeated exposure). Both in acute and chronic cases of inhalation exposure, the primary effect was irritating to the respiratory tract and eyes (burning eyes and throat, feeling of breathlessness, tearing, coughing, bronchospasm, pain behind the sternum, pleurisy). In exposed workers, deterioration of pulmonary spirometric parameters was observed. The late effects of exposure were asthmatic problems and obstructive respiratory disease. Available animal studies are poorly documented. Phosphoryl trichloride did not show any mutagenic effects. There is no information on the carcinogenic, embryotoxic or teratogenic effects of this substance in the available literature. The critical effect of the action of phosphoryl trichloride is a strong irritation on the mucous membranes of the eyes and upper respiratory tract. A concentration of 0.48 mg/m3 constituting the threshold for toxic effects of phosphoryl trichloride in studies in rats and guinea pigs was taken as the LOAEC value. After applying the uncertainty coefficients, the MAC value of phosphoryl trichloride calculated on this basis is 0.06 mg/m3. It is proposed to adopt the MAC value in accordance with the SCOEL and ACSH recommendation, i.e., 0.064 mg/m3. Phosphoryl trichloride is a strongly irritating substance, in order to prevent peak concentrations of this substance it is proposed to set the maximum allowable short-term concentration (MAC-STEL) at level 2 x MAC value, i.e., 0.13 mg/m3. There are no substantive foundations to determine the permissible biological exposure indices to phosphoryl trichloride (DSB). Due to the corrosive effect of phosphoryl chloride, it is proposed to label it with the letter "C" (a substance with a corrosive effect). This article discusses the problems of occupational safety and health, which are covered by health sciences and environmental engineering.