Concentration and particle size distribution in smoke from marijuana cigarettes with different delta 9-tetrahydrocannabinol content.

Particle size and mass concentration are important determinants of site and quantity of respiratory tract deposition of aerosols. Particle concentrations and size distributions of smoke from marijuana cigarettes with different concentrations (as measured in the marijuana leaf) of delta 9-tetrahydrocannabinol (delta 9-THC) were measured using a single particle aerodynamic relaxation time (SPART) analyzer. The SPART analyzer measures aerodynamic diameter of single suspended particles at a rate of 3000/min. Cigarettes were smoked using a 35-cc, 2-sec puffing device attached to a diluter; dilution and analysis were completed within 4 sec of puff generation. The size distribution of smoke from all marijuana cigarettes was similar to that for tobacco cigarettes, ranging from 0.35 to 0.43 micron (count median aerodynamic diameter). The particle number and mass concentration increased as delta 9-THC concentration increased, being, respectively, 2.2- and 3.8-fold higher in the marijuana cigarette leaf with highest delta 9-THC concentration compared to the placebo marijuana cigarette. These data indicate the need for quantitative comparisons of other potentially toxic constituents in marijuana cigarettes of different delta 9-THC concentrations.