Human exposure to 3-carene by inhalation: toxicokinetics, effects on pulmonary function and occurrence of irritative and CNS symptoms.

Terpenes, especially 3-carene, may irritate the skin and mucous membranes and prolonged exposure may result in allergic contact dermatitis or chronic lung function impairment. The toxicokinetics of 3-carene were studied in human volunteers exposed by inhalation (2 hr 50 W) in an exposure chamber on three occasions. The exposure concentrations were approximately 10, 225, and 450 mg/m3 3-carene. The relative pulmonary uptake was high, approximately 70% for the higher exposure levels. Total uptake increased linearly with increasing exposure. The blood clearance of 3-carene observed in this study, 0.9 liter.kg-1.hr-1, indicates that 3-carene is fairly readily metabolized. About 3% of the total uptake was eliminated unchanged via the lungs while less than 0.001% was eliminated in the urine after the end of exposure. A long half time in blood was observed in the terminal phase which indicates a high affinity to adipose tissues. A statistically significant divergence between ratings of irritation during the high exposure level and during the medium and control levels was observed. The difference in airway resistance after exposure to a high concentration of 3-carene compared to control level was not significant (P = 0.02).