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Appendices 1-18 to: Report on the Health Effects of Selected Pesticide Coformulants

77     Summary

77.1     Description

Propylene Glycol (PG) is a colourless viscous liquid. PG is soluble in water and hygroscopic and has a low vapour pressure.

77.2     Toxicokinetics

PG has been shown to be rapidly absorbed form the gastrointestinal tract and following dermal absorption through damaged skin. It is metabolised to lactic acid and pyruvic acid, which enter the energy production, or for pyruvic acid is further metabolised to CO₂ and water. 20- 45% PG is found unchanged in urine.

77.3     Human toxicity

77.3.1     Single dose toxicity

No reports of deaths caused by PG were found. Acute effects included CNS depression and acidosis was reported from exposure to very high doses.

77.3.2     Irritation and sensitisation

Numerous patch tests have been performed to examine the incidence and nature of PG skin reactions. However, the results were difficult to interpret. PG showed weak irritative and none to slight allergenic response.

77.3.3     Repeated dose toxicity

No effects were seen from repeated exposure to up to 94 mg PG/m³ over several weeks. Ingestion by a child of 114-228 mg/kg b.w./day for 13 months resulted in CNS-depression with seizures and unconsciousness.

No further data regarding effects in humans were found.

77.4     Animal toxicity

77.4.1     Single dose toxicity

Rabbits exposed to aerosol concentrations of 10% PG showed degeneration of the goblet cells in the trachea, and the ciliated cells were affected.

Reported oral LD₅₀-values for rats and mice range from approximately 20 to 30 g/kg b.w., while the LD₅₀-values for rabbits and guinea pigs ranged from 18 to 20 g/kg b.w.; an LD₅₀-valus of 22 g PG/kg b.w. in dog was reported. Signs of toxicity include CNS-depression and respiratory depression and reversible haematological effects. Slight hyperaemia or the gastrointestinal tract and one case of haemorrhagic enteritis in rats have also been reported.

A dermal LD₅₀-value in the rabbit was reported to be 20.8 g/kg b.w.

77.4.2     Irritation and Sensitisation

Various reports describe PG as not irritating to mildly irritating to the skin and eyes of rabbits. No sensitisation studies in animals were found.

77.4.3     Repeated dose toxicity

Nose bleeding was reported from inhalation exposure of rats to aerosols at  concentrations of 160, 1000 and 2200 mg PG/m³ over 90 days.

Repeated inhalation exposure of rats to aerosols with 1000 or 2200 mg PG/m³ over 90 days caused multiplication and enlargement of the goblet cells and their mucous content in the nasal epithelium.

Rats exposed by inhalation to 2200 mg PG/m³ as an aerosol over 90 days showed an effect (not dose-related) on haematological parameters.

Dogs treated via the diet with 5000 mg PG/kg b.w/day over 2 years and cats treated for shorter periods of time (2, 3, 5, 13 or 17 weeks) with doses of 1100 to 8000 mg PG/kg b.w./day showed haematological changes with decreased erythrocyte count and Heinz body formation.

No effects were seen in rats and in dogs treated with 2000 mg/kg b.w./day for 2 years. An ADI for PG from food of 25 mg/kg b.w/day has been defined on basis of this NOAEL.

77.4.4     Toxicity to reproduction

PG did not cause fertility effects in rats by inhalation or oral administration. No developmental effects in rats, mice, hamsters or rabbits treated by the oral route. No dermal data were available.

77.4.5     Mutagenic and genotoxic effects

PG was tested in in vitro bacterial assays and in mammalian cells for chromosome aberrations, DNA-damage and repair and cell transformation. All tests but one, a chromosome aberration assay in Chinese hamster lung cells conducted without metabolic activation, were negative.

An in vivo chromosome aberration test in rats and two dominant lethal in vivo tests, in rats and mice, were negative.

77.4.6     Carcinogenic effects

No carcinogenic effect was reported from PG in a 2-year oral study in rats or a 120-week dermal study in mice.

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