Phosphoric acid, phosphorus pentoxide, phosphorus oxychloride, phosphorous pentachloride, phosphorus pentasulphide
Payne, MP; Shillaker, RO; Wilson, AJ
Phosphoric acid. No significant toxicokinetic information is available. Although the reliability of the very low inhalation LC50 value in mice is open to question, the substance would appear to be toxic by this route. It is also moderately toxic to rodents via the oral route. The acute dermal toxicity in rabbits is low. The substance is corrosive to rabbit skin and severely irritating to the eye. In a poorly reported study, "chronic" inhalation of phosphoric acid aerosol was claimed to cause irritation of the respiratory tract. The substance has yielded negative results in bacterial mutagenicity assays, the only genotoxicity data available. There are no adequate reproductive toxicity or carcinogenicity investigations in animals. No clearly reliable human acute inhalation data are available. As in other species the substance is corrosive, with moderate to severe subjective stinging responses being recorded following dermal or ocular application of very dilute solutions. Widespread corrosion of the gastrointestinal tract has been reported in one case of oral ingestion. No useful human data are available on the effects of repeated inhalation exposure. Consumption of moderate amounts of phosphoric acid in the diet failed to indicate any toxicity. No reliable human data on the carcinogenic potential of phosphoric acid are available. In addition no human data are available on its potential to cause genotoxicity or reproductive toxicity. Phosphorus pentoxide. Data on the toxicity of phosphorus pentoxide to animals are available only from studies of exposure to smokes produced by burning red or white phosphorus. Phosphorus pentoxide is the predominant combustion product when oxygen is not limited. Variable amounts of hydrolysis products are subsequently formed. No toxicokinetic studies were located. Acute inhalation of phosphorus smokes is moderately toxic to several laboratory species and very toxic to guinea pigs. Marked respiratory tract irritation was commonly observed and in one study slight eye irritation was noted. Phosphorus pentoxide is expected to be corrosive because of its rapid exothermic reaction on contact with water to generate phosphoric acid. Repeated inhalation of phosphorus smokes causes respiratory tract irritation. Pulmonary fibrosis has been observed in one study in rats exposed to a smoke concentration of 300 mg/m3; a no-effect level of 50 mg/m3 was claimed but no supporting data were provided to support the claim. In another study there was evidence of toxicity in rats and mice following repeated exposure to phosphorus smoke at a concentration approximately equivalent to 37 mg/m3 phosphorus pentoxide. The information available from genotoxicity and animal reproductive toxicity studies of phosphorus smokes is too limited to enable useful conclusions to be drawn. No animal carcinogenicity studies are available. Phosphorus pentoxide concentrations of 3.6-11.3 mg/m3 have been claimed to cause coughing amongst inexperienced workers and 100 mg/m3 to be unendurable except to hardened workers, but the reliability of this data is questionable. In contrast, phosphorus smokes would appear to be tolerated at significantly higher exposure levels, 1000 mg/m3 being reported to be the minimum harassing level in resting men. It is assumed that these reports refer to the response to a single exposure, but the duration of exposure is not known. No useful human data on the effects of repeated exposure to phosphorus pentoxide are available. No human data are available on the genotoxic or carcinogenic potential of phosphoric acid or on its potential to cause reproductive toxicity. Phosphorus oxychloride. No toxicokinetic studies were located. Phosphorus oxychloride is acutely very toxic when inhaled by rats and guinea pigs, causing extensive irritation of the respiratory tract. It is also acutely toxic to rats via the oral route. The substance is corrosive to rabbit skin and causes severe eye damage. Little reliable information is available on the effects of repeated inhalation in animals. Irritation of the respiratory tract would be expected and has been claimed in one poorly reported rat study, although no reliance can be placed on these data, particularly as it is not clear if continuous or repeated exposure was used. No reliable genotoxicity or animal reproductive toxicity data are available. No animal carcinogenicity study was located. Single exposure of humans to airborne material has been reported to cause conjunctivitis, pharyngitis and respiratory tract irritation, including pulmonary oedema. No reliable threshold concentration for these effects is available. Similar effects were seen following repeated exposure including asthmatic bronchitis and, in severe cases, emphysema. Exposure levels were 10-20 mg/m3, rising to 70 mg/m3, and sometimes to higher levels. Workers who suffered respiratory effects were reported to show increased respiratory tract sensitivity to phosphorus oxychloride and to other irritant substances, particularly phosphorus bichloride and pentachloride. No human data are available on the genotoxic or carcinogenic potential of phosphorus oxychloride or on its potential to cause reproductive toxicity. Phosphorus trichloride. No toxicokinetic studies were located. The substance is very toxic to rodents following acute inhalation exposure. The main effects reported in acute inhalation studies are irritation and/or corrosion of the respiratory tract, eyes and skin. The substance is also acutely toxic to rats via the oral route and is corrosive when applied to the skin as a liquid. Phosphorus trichloride has been reported to be negative in a modified Ames test. No other genotoxicity information was located. No repeat dose, reproductive toxicity or carcinogenicity studies in animals are available. Single exposure of humans to airborne material has been reported to lead to ocular and respiratory tract irritation. No reliable threshold concentration for these effects is available. Repeated exposure to levels of 10-20 mg/m3, with intermittent peaks of 80-150 mg/m3 has been reported to cause pharyngeal irritation, coughing, catarrh and pronounced asthmatic bronchitis. These effects tended to recur and, following one to two years' exposure, could develop into pulmonary emphysema. No human data are available on the genotoxic or carcinogenic potential of phosphorus trichloride or on its potential to cause reproductive toxicity. Phosphorus pentachloride. Very little information is available on phosphorus pentachloride. One poorly reported study indicates that it is very toxic to rodents following acute inhalation exposure. The substance is also acutely toxic via the oral route. Phosphorus pentachloride would be expected to be corrosive because of its hydrolysis products. A report of tissue necrosis when the substance is applied to rabbit skin supports this view. Phosphorus pentachloride is reported to cause irritation to the respiratory tract and eyes in humans. No reliable threshold concentration for these effects is available. No other useful animal or human data are available. Phosphorus pentasulphide. There is virtually no information on the toxicity of phosphorus pentasulphide. The substance is reported to be acutely toxic to rats following oral administration and to be a moderate skin and eye irritant. Irritancy of the respiratory tract would be expected because the sustance is rapidly hydrolysed to phosphoric acid and hydrogen sulphide. No good human data on the effects of phosphorus pentasulphide are available.