Smokers of low-yield, ventilated-filter cigarettes sometimes defeat the purpose of the smoke-dilution holes by occluding them with fingers, lips, or tape. Blocking the holes is shown to have large effects on the delivery by these cigarettes of toxic products (nicotine, tar, and carbon monoxide). Techniques for detecting this misuse of "less hazardous" cigarettes are discussed, with particular emphasis on the distinctive signs of hole-blocking which are left in the spent filters. (Am J Public Health 1980; 70:1202-1203 low-tar smokers have blocked the holes with their fingers, lips or with tape.* Lipstick marks on the holes have proven to be clear-cut indicators of hole-blocking; holding the cigarette between the teeth appears to facilitate the practice of covering the holes with one's lips. A few smokers confess to having held their cigarettes with two hands (the tips of four fingers over the holes) to block the perforations. A simple "'pinch" of the perforations with opposing fingers is a more common method of blocking the holes. The present study reports the extent to which hole-blocking can increase the delivery of tobacco smoke to the smoker. MethodsMost of the apparently least-hazardous of the 'less-hazardous' low-tar, low-nicotine, low carbon monoxide (CO) cigarettes,' achieve their low yields of toxic products by means of ventilation holes in the filters. In 1979, about 25 per cent of all cigarettes sold in the United States had perforated filter tips.2 The rings of perforations cause inhaled tobacco smoke to be diluted with air and thereby decrease the amount of smoke per puff delivered to the smoker.The effects (and frustrations) of ventilated filters can be illustrated by making a ring of small holes about 10 mm from the proximal end of a drinking straw. A desired beverage can still be drunk, but it is adulterated with air and much harder to suck through the straw. Although smoking machines which measure tar and nicotine deliveries do not occlude the perforations, we have found in systematic interviews that 32 per cent to 69 per cent (95 per cent confidence interval) of

No abstract

A group of 22 volunteers who smoked daily more than 20 'high' nicotine (0.8 to I.I mg) Canadian cigarettes were switched to lower yield brands in two stages over an eight-week period. The control group (six subjects) switched brands with nicotine yields within ± O.I mg of their usual brand while the treatment group smoked reduced yield brands (first stage, 33% reduction; second stage 61% reduction).Overall averages for levels of blood carboxyhemoglobin, plasma thiocyanate and serum cotinine were found to change significantly from week to week but there was no discernible difference between the treatment and the control group in week to week pattern. Although the majority of smokers in this study did not increase their exposure to cigarette smoke by smoking low yield cigarettes, it can not be said that the switch resulted in 'safer' smoking.

Cigarettes deliver drugs; at root smoking is drug taking.' Scientific work has confirmed nicotine as a powerfully reinforcing, psychoactive drug.2 For the consumer, then, ultra-low-yield cigarettes raise the simple issue of drug "cutting" or adulteration. The unsatisfactoriness ofultra-low-yield cigarettes is seen in the scarcity of customers for these products even in health-conscious California. As noted by Maron and Fortmann in this issue of the Journal,3 only 3.8 per cent of smokers in a population-based sample smoke cigarettes in the range of 0.1 to 0.2 mg nicotine, 1 to 2 mg "tar". Despite the publicity about disease risks of smoking and the widespread belief that ultra-low-yield cigarettes are less hazardous, most smokers will not cross the street for these cigarettes, let alone walk the advertised mile.No doubt smokers have routinely tried ultra-low-yield cigarettes and just as routinely have rejected them as unsatisfying. A 1 mg "tar", 0.1 mg nicotine cigarette delivers about 80 per cent diluting air in each pufftaken by official smoking machines. 4 Those smokers who learn the tricks of compensatory smoking are more likely to persist in smoking these cigarettes than are those smokers who do not develop satisfactory compensation techniques. For ultra-low-yield cigarettes, the main "oversmoking" techniques are blocking the diluting air vents on filters with lips or fingers,5 taking larger puffs, and, as Maron and Fortmann3 remind us, simply smoking more cigarettes per day. A smoker self-selection bias (compensators remain, noncompensators leave) may cause much of the discouraging pattern found in and reviewed in the current report.3Experimental Evidence-Recent experiments show a more encouraging picture of what might be gained from the widespread use of ultra-low-yield cigarettes by smokers who refuse to quit smoking. West, et al,6 randomly assigned 14 smokers to remain with their own brand (average 1.3 mg nicotine, 14.2 mg "tar") and 12 smokers to switch to an ultra-low yield brand (0.1 mg nicotine, 1 mg "tar"). Over 10 days of smoking, the ultra-low yield group had plasma nicotine levels that were only 40 per cent of the own brand group (9.4 vs 22.8 ng/ml); carbon monoxide levels differed by 30 per cent (10.5 vs 33.2 ppm). (Although not noted in the Method, smokers were explicitly instructed not to block filter vents [R. West, Personal Communication]). Similarly, in the experimental component of their report, Benowitz, et al,7 found partial compensation in smokers who were forced to smoke ultra-low-yield cigarettes. (Behavioral blocking offilter vents was not forbidden in this study, but may have been discouraged by details of the procedure.8)The combined lesson of the cross-sectional surveys and the forced switching experiments is that, if there is to be maximal progress with the current style ultra-low yield cigarette, its use needs to be encouraged more forcefully. One of the reasons smokers don't put up with ultra-low-yields is that higher yield cigarettes are only an easy purchase away. Imagine a c...

The sales of the lowest yield cigarettes (1-3 mg tar) seem to have been particularly resistant to the effects of promotion and advertising, while the sales of other low-yield cigarettes (4-9 mg tar) seem to have been increased by promotional efforts. This finding is consistent with the existence of a boundary of tar and nicotine acceptability below which consumers in general are not prepared to go. Use of lower tar cigarettes may be helpful for those who cannot stop smoking, but, since 1979, the percentage of cigarettes under 16 mg tar has changed little.