Experimental exposure to propylene glycol mist in aviation emergency training: acute ocular and respiratory effects

Propylene glycol (PG) (1-2 propanediol; CAS No 57-55-6) is a low toxicity compound widely used as a food additive, in pharmaceutical preparations, in cosmetics, and in the workplace-for example, water based paints, de-icing fluids, and cooling liquids. Exposure to PG mist may occur from smoke generators in discotheques, theatres, and aviation emergency training. Propylene glycol may cause contact allergy, but there is sparse information on health effects from occupational exposure to PG.

Non-asthmatic volunteers (n=27) were exposed in an aircraft simulator to PG mist over 1 minute, during realistic training conditions. Geometric mean concentration of PG was 309 mg/m3 (range 176-851 mg/m3), with the highest concentrations in the afternoon. The medical investigation was performed both before and after the exposure (within 15 minutes). It included an estimate of tear film stability break up time, nasal patency by acoustic rhinometry, dynamic spirometry, and a doctor's administered questionnaire on symptoms.

After exposure to PG mist for 1 minute tear film stability decreased, ocular and throat symptoms increased, forced expiratory volume in 1 second/forced vital capacity (FEV1/FVC) was slightly reduced, and self rated severity of dyspnoea was slightly increased. No effect was found for nasal patency, vital capacity (VC), FVC, nasal symptoms, dermal symptoms, smell of solvent, or any systemic symptoms. Those exposed to the higher concentrations in the afternoon had a more pronounced increase of throat symptoms, and a more pronounced decrease of tear film stability. In four subjects who reported development of irritative cough during exposure to PG, FEV1 was decreased by 5%, but FEV1 was unchanged among those who did not develop a cough. Those who developed a cough also had an increased perception of mild dyspnoea.

Short exposure to PG mist from artificial smoke generators may cause acute ocular and upper airway irritation in non-asthmatic subjects. A few may also react with cough and slight airway obstruction.