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

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

78 Evaluation

Data on human toxicity of propylene glycol (PG) are scarce. The toxicological data on experimental animals indicate that PG has a low order of toxicity.

PG has a very low acute oral toxicity in several species with LD₅₀-values of 18-33.5 g/kg b.w.. At high oral doses, central nervous system depression occurs as demonstrated in dogs treated with 8000 mg/ kg b.w.

No effects on the respiratory tract have been reported from human exposure to PG used as a vehicle for medical purposes. No systemic effects in rabbits and dogs were reported from short-time inhalation exposure of 10% PG. However, no details on exposure conditions or particle size of the aerosol were given in the reference. Local effects in the respiratory tract involving goblet cells have been reported in rats and rabbits. Haemorrhage from the nose and hyperaemia of the intestines is probably related to the highly hygroscopic character of PG and the effects are probably due to dehydration of the tissues.

PG is a mild irritant to rabbit skin. No data on sensitisation to PG in animals were found. Contact dermatitis in humans from PG has been reported. The majority of these reactions are of irritative nature. However, a few may be of allergic nature. On basis of the low number of persons sensitised to PG in comparison with widespread exposure due to extensive use of the substance, the sensitising potential of PG is considered to be low.

Effects on the erythrocytes with decreased erythrocyte counts and formation of Heinz bodies was described at high doses in dogs treated orally with 5000 mg PG/kg b.w./day over 2 years, and more consistently and at lower doses in cats exposed to PG by the oral route for 2-17 weeks to doses as low as 1100 mg/kg b.w./day. Cats thus appear to be more sensitive to PG, which could be explained by a different metabolism in cats possibly yielding a higher level of the parent compound in the blood. No haematological signs have been reported in humans from exposure to PG. Therefore, the effect is considered of lesser relevance to humans.

Short-term studies in rats and dogs showed no adverse effects at levels of around 10 % of the diet (equivalent to approximately 13200 mg/kg b.w. in rats). The NOAEL from long-term feeding studies in rats and dogs was 2000 mg/kg b.w./day. PG is considered of low toxicity following repeated exposure.

No effects on reproduction were reported from fertility and developmental studies in mice, rats, hamsters and rabbits.

Several negative in vitro assays for different mutagenicity end-points are available. One in vitro chromosome aberration test showed a positive result without metabolic activation. However, 3 in vivo tests were negative. On basis of all the evidence available, PG is evaluated not to be a mutagenic substance.

No carcinogenic effect has been reported.

Based on the available data, the critical effects of PG are considered to be the effects on the skin and its dehydrating potential to mucous membranes.