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From the Centers for Disease Control and Prevention
February 11, 1998

Filter Ventilation Levels in Selected US Cigarettes, 1997

JAMA. 1998;279(6):424-425. doi:10.1001/jama.279.6.424-JWR0211-4-1

MMWR. 1997;46:1043-1047

1 figure, 1 table omitted

CIGARETTE BRANDS that deliver ≤15 mg of tar in official smoking-machine tests accounted for 72.7% of total cigarette sales in 1995.1 Many of these brands use ventilated filters—a system with small perforations around the filter that are designed to draw in additional air during smoking. In brands with ventilated filters, air introduced through the vents dilutes the amounts of tar, nicotine, carbon monoxide (CO), and other hazardous constituents of cigarette smoke.2 This report summarizes results of tests conducted by researchers at The Pennsylvania State University during July 1997 to measure the percentage of air drawn through the filter vents of 32 brands of U.S. cigarettes that have tar yields rated by the Federal Trade Commission (FTC) as ranging from 1 mg-18 mg; the report also examines the correlation between the degree of filter ventilation and tar yield. The findings indicate that 30 (94%) of 32 brands tested were ventilated and that percentage filter ventilation varied inversely with standard tar, nicotine, and CO yields.

Testing conditions simulated consumer use of a freshly opened pack of cigarettes. One pack each of 32 commercially available cigarette brands was purchased from retail stores in State College, Pennsylvania, during July 1997. Each pack was opened, and 20 unlit cigarettes were tested within 10 minutes with an FDT Ventilation Tester (Fidus Instrument Corporation, Richmond, Virginia)*, which measured the percentage of additional air drawn into a puff through the filter vents (i.e., percentage filter ventilation†). The testing conditions were maintained at an ambient air temperature of 72 F (22 C) (range: 68 F-75 F [20 C-24 C]) and a relative humidity of 60% (range: 55%-65%). Because of the potential for smokers to knowingly or inadvertently block filter ventilation holes with their lips or fingers,3 the location of these holes was determined for each of the 32 brands by selecting one cigarette from each pack to be measured to the nearest 0.5 mm by two technicians.

The ventilation percentage for the 32 brands ranged from 0 to 83%. Based on four categories of tar yield, there was a linear association between ventilation percentage and tar yield. Standard tar yields varied inversely with percentage filter ventilation (r=−0.93 [degrees of freedom=31]). In addition, ventilation percentage varied inversely with nicotine yield (r=−0.90) and CO yield (r=−0.95 [degrees of freedom=29]). The distance of filter vents from the mouth end of the filter ranged from 11 mm-15 mm.

Reported by:

LT Kozlowski, PhD, NY Mehta, CT Sweeney, Dept of Biobehavioral Health, College of Health and Human Development, The Pennsylvania State Univ, University Park. Office on Smoking and Health, National Center for Chronic Disease Prevention and Health Promotion, CDC.

CDC Editorial Note:

From 1954 to 1994, sales-weighted tar yields of cigarettes declined from an estimated average of 37 mg tar to 12 mg tar, respectively.2,4 Despite this decline in tar yields—attributable, in part, to the increased use of filter ventilation—the relative risk for lung cancer has increased, even when accounting for the delayed onset of mortality from tobacco-linked lung cancer.5 Factors potentially associated with the increase in smoking-related mortality are an increase in the number of cigarettes smoked (and therefore, tar exposure) by persons who use reduced-tar brands, inhaling more deeply, and an increased frequency of puffing.2 In addition, smokers who use reduced-tar cigarettes may be blocking some of the filter vents with their fingers or lips, therefore increasing their exposure to the carcinogens in cigarette smoke.3 Compensatory changes in smoking behaviors among persons who smoke reduced-tar cigarettes could be associated with changes in the risk, histology, and site of lung cancers.6

Blocking even a portion of the filter vents can markedly increase a smoker's exposure to the harmful components of cigarette smoke. Smokers can inadvertently block filter vents because filter vents often are invisible to the unaided eye and the filters do not include a marking (e.g., a colored band) to indicate the presence of vents. Blocking with the lips would more likely occur with the brands with filter vents closer to the mouth end of the filter7 and blocking with the fingers would more likely occur with brands with filter vents further away from the mouth end of the filter. One study has estimated that 58% of persons who smoke cigarettes with ≤4 mg tar are blocking some filter vents.3 In tests conducted on cigarette smoking machines, blocking half of the ventilation holes on a cigarette with standard yields of 4 mg tar, 0.5 mg nicotine, and 5 mg CO increased FTC-rated tar yields by 60%, nicotine by 62%, and CO by 73%.8 In addition, one study by the tobacco industry7 estimated that, when smoking an ultra-light cigarette (2.2 mg tar), 45% of smokers blocked vents to some degree with their lips: 21% of smokers (or nearly half of those who blocked vents) increased tar yields to at least 3.3 mg tar (i.e., by ≥ 50%); overall, approximately one in 10 smokers (approximately 25% of those who blocked vents) were estimated to at least double their tar yields from blocking with their lips alone.

This study is subject to at least four limitations. First, although the cigarette brands tested reflected the range of tar yields for filter cigarettes, the analysis did not use a sales-weighted or representative sample of all available brands. For example, although cigarettes with <3 mg of tar were included in this study, such cigarettes accounted for only approximately 2% of sales in 1995.1 Second, the findings for any specific brand could have been affected by factors unique to the sample of cigarettes delivered to the State College area, including, for example, manufacturing dates and retailers' storage conditions (e.g., temperature and humidity). Third, cigarettes were not maintained at standard temperature and humidity conditions for 24 hours before testing; this was done to simulate use of a freshly opened pack of cigarettes by a consumer. Finally, although the analysis used 1994 data on tar yields1,4 (the most recent available), brand formulations may have changed since 1994.

Many smokers who block filter vents probably are exposed to substantially higher levels of hazardous smoke than the FTC-rated levels for those brands. The FTC recognizes that their machine-measured yields of tar and nicotine are poor predictors of exposure to toxic smoke products by smokers2 and invites comments (until January 20, 1998) on proposed changes to its testing and reporting system (FTC file number P944509; additional information is available from the FTC's Bureau of Consumer Protection by contacting C. Lee Peeler, telephone [202] 326-3090, or Shira Modell, telephone [202] 326-3116). To identify cigarette brands in which vent-blocking probably is a problem, all cigarette testing should include measurement of filter ventilation.

An estimated two thirds of U.S. smokers either are unaware of the presence of vents on cigarettes or do not know that tar yields increase when vents are blocked.9 Filter vents can be difficult to see, which may account for the high proportion of smokers (80%) of "light" (6-15 mg tar) and "ultra-light" (1-5 mg tar) cigarettes who are unaware of the presence of vents on the brands they smoke.10 These findings underscore the need for intensified efforts to educate smokers about the risks associated with smoking reduced-tar cigarettes.

*Use of trade names and commercial sources is for identification only and does not imply endorsement by CDC or the U.S. Department of Health and Human Services.
†The percentage of a standard puff (35-mL volume and 2-second duration) that is air taken into the puff through the filter vents. A cigarette with no filter ventilation would produce a puff undiluted by air from filter vents; a cigarette with 80% filter ventilation would produce a puff that is 80% air from vents and 20% smoke undiluted by air from vents.
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