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Clearing the Smoke: Assessing the Science Base for Tobacco Harm Reduction
1997; Kabat and Hebert, 1991; McCarthy et al., 1995; Sidney et al., 1995; Women who smoke menthol cigarettes have greater nicotine exposure, 1999).
Cigarette paper is second to tobacco as the most variable component in producing cigarettes. The degree of ventilation allowed by the paper can be manipulated in the production process. More porous cigarette paper has been shown to reduce smoke yields of CO and tar as well as volatile nitrosamines, TSNAs, and BaP through dilution. Increased permeability does not reduce the low-molecular-weight gas-phase components in smoke however (NIH, 1996). For a more detailed discussion of the toxicology of smoke, see Chapter 10.
A new paper has been introduced for Merit cigarettes, which claimed to decrease the smoldering of cigarettes when dropped onto fabric. The new technology consists of a modified wrapping paper that reduces the amount of oxygen entering the cigarette, therefore slowing the rate at which it burns. This could decrease the 25% of fatal residential fires started by smoldering cigarettes (Meier, 2000). New York became the first state to pass legislation imposing fire safety standards on cigarettes (Cigarettes-fire bill, 2000).
The procedure for measuring the tar and nicotine yields of mainstream smoke (i.e., the “smoking machine”) is standardized for consistency between laboratories and from product to product. There are two methods in widespread use: the Federal Trade Commission (FTC) method and the International Standards Organization (ISO) method. Differences between these two are minor, and puff volume, duration, and interval are common to both standards. Particulate matter is collected on Cambridge filter pads as what is called “wet total particulate matter” (Davis and Nielson, 1999). Tar is a generic term for the total particulate matter minus the nicotine and water. The material that passes through the filter is called the vapor phase. This is described in more detail in Chapters 10 and 11.
Tar yields are influenced primarily through filtration, ventilation (tip ventilation holes and paper porosity), and the choice of tobacco processing and blend. As with any agricultural product, there is natural variation from year to year. In the interest of manufacturing a consistent product, prepared tobacco is blended with stock of crops from previous years to maintain a uniform product line. Finally, the burn rate of cigarettes has been proven to influence smoke yields. The faster the burn rate, the lower the tar yields will be, according to FTC measurements. Shredded tobacco can facilitate a faster burn rate (Davis and Nielsen, 1999), as can the use of accelerants.