Incidence and toxicological aspects of cannabis and ethanol detected in 1394 fatally injured drivers and pedestrians in Ontario (1982-1984).

A comprehensive epidemiological study of the involvement of cannabis and ethanol in motor vehicle fatalities in the Province of Ontario, Canada, is described. The study is based on toxicological analyses of blood and, when available, urine specimens. Ethanol was determined by headspace gas chromatography (GC). For cannabis, the methods employed were radioimmunoassays (RIAs) for screening and gas chromatography/mass spectrometry (GC/MS) for the determination of delta-9-tetrahydrocannabinol (THC) in blood. The study sample consisted of 1169 drivers and 225 pedestrians. THC was detected in the blood of 127 driver victims (10.9%) in concentrations ranging from 0.2 to 37 ng/mL, with a mean of 3.1 +/- 5.0 ng/mL. Ethanol was found in 667 driver victims (57.1%), in concentrations ranging from 9 to 441 mg/100 mL, with a mean of 165.8 +/- 79.5 mg/100 mL. For pedestrians, the incidence of THC and ethanol in the blood was 7.6 and 53.3%, respectively. The incidence of THC in the driver victims in this study constitutes an approximately threefold increase over the results of an Ontario study completed in 1979. At least a part of the increase may be attributed to interstudy differences in analytical methodology for cannabinoids.