Mutagenicity of smoke condensates from joss sticks.

Smoke condensates obtained from 8 Japanese brands of joss sticks were assayed for mutagenicity on Salmonella typhimurium TA100 and TA98 with and without metabolic activation by S9 mix. An average of 22 mg of smoke condensate was obtained per joss stick weighing about 0.3 g. Smoke condensates obtained from all the joss sticks tested showed definite mutagenicity with a linear dose response on both tester strains of bacteria with metabolic activation. Without S9 mix, the smoke condensates from some of the joss sticks also showed positive mutagenicity on TA100 at 0.15 or 0.3 mg/plate. The revertant numbers over the background counts induced by 1-mg samples of the smoke condensates from joss sticks with S9 mix were 140--310 with TA100 and 90--200 with TA98. These values were one-fifth to half that of cigarette smoke condensate with TA100 and one-fourteenth to one-fifth that with TA98. However, it was calculated that, when joss sticks are burnt continuously in a closed space under the usual conditions, the mutagenicity of their smoke per unit volume of air is similar to that of the smoke produced by the smoking of two cigarettes per hour. Extracts of unburnt joss sticks with methanol, chloroform or dimethylsulfoxide had no mutagenicity, showing that the burning process produces the mutagenic substance(s).