Estimating the hazards of "less hazardous" cigarettes. III. A study of the effect of various smoking conditions on yields of hydrogen cyanide and cigarette tar.

A brand of cigarette with nominal tar and nicotine yields of 4.0 mg and 0.4 mg, respectively, was examined under various machine-smoked conditions that reflect the wide range of human smoking behavior. Three levels of each of five smoking parameters--butt length, puff duration, puff interval, puff volume, and ventilation occlusion--were examined, and the effects on puff number and total particulate matter (TPM) as well as gas phase, particulate phase, and total HCN yields were estimated. Yields of hydrogen cyanide (a ciliatoxic agent) and TPM varied significantly under different smoking conditions. Ventilation occlusion had the most pronounced effect, accounting for 34% of the response variation of TPM yields and 42% of the response variation for total hydrogen cyanide yields. In the survey of available brands, total hydrogen cyanide yields varied from 2 to 233 micrograms/cigarette for the 115 brands tested, a range less than that observed for a single brand smoked under various nonstandard conditions, providing a possible explanation for the previously noted lack of correspondence between HCN yields under standard conditions and levels of thiocyanate in samples of smokers' plasma and saliva. In addition, hydrogen cyanide yields and efficiency of filters in removing HCN were examined under standard smoking conditions. Acetate filters, the most common variety, were found to remove an average of about 14% of the hydrogen cyanide from the mainstream smoke.