Exposure to Cigarette Smoke Constituents in a Population of Adult Cigarette Smokers in the U.S. Who Spontaneously Switched to Cigarettes with Lower or Higher Machine Measured ‘Tar’ Yield

Changes in exposure to cigarette smoke and smoking behavior were assessed in adult smokers participating in a multi-center, cross-sectional study who spontaneously switched to > 3 mg lower or higher machine measured ‘tar’ yield. Of 2,542 consenting smokers only 23 down-switchers (DWNSW) and 68 up-switchers (UPSW) met study eligibility criteria. Biomarkers of exposure (BOE) to selected smoke constituents were measured. Large variability was observed in the BOEs (e.g. CV% for nicotine equivalents (nicotine and five of its metabolites, NE) per day ranged from 59% to 78%). On average, DWNSW smoked two more cigarettes/day (+ 9%) that had ~ 5.9 mg lower ‘tar’ yield. Mean NE/day were 12.0 ± 6.2 mg/day compared to 13.9 ± 8.2 mg/day after down switching. Slightly lower levels of NE/cigarette (-8%), total NNAL/day and per cigarette were observed (-18% and -23%) in the DWNSW's. UPSW smoked two fewer cigarettes/day (-13%) with higher ‘tar’ yield (~ 8.4 mg higher ‘tar’). NE/day was 12.5 ± 9.7 vs. 12.8 ± 9.0 mg/day. Total NNAL values per day and per cigarette were lower (-24% and -17%). Due to the large variability and insufficient power to detect significant differences in exposure based on post-hoc power calculations, no definitive conclusions can be drawn from this study. These results suggest that it might not be feasible to conduct a definitive assessment of changes in exposure among spontaneous switchers.