Differential Examination of Bronchoalveolar Lavage Cells in Tobacco Cigarette and Marijuana Smokers1–3

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Abstract
Cells derived from bronchoalveolar lavage (BAL) were obtained from 19 healthy non-smokers (NS) and from 43 healthy smokers of tobacco and/or marijuana. Thirteen subjects smoked tobacco cigarettes only (TS) (mean ± SE: 17.4 ± 5.5 pack-years). Thirty subjects smoked marijuana; of these, 14 smoked marijuana only (MS) (149.1 ± 102.7 joint-years) and 16 smoked marijuana and tobacco (MTS) (43.3 ± 7.2 joint-years and 18.4 ± 3.2 pack-years). Cell counts were expressed as total number recovered and as number of cells per milliliter of BAL fluid returned. Cell differentials were performed on Giemsa-stained cytopreps. Total cell number was significantly increased in the MTS, TS, and MS compared with that in the NS (p < 0.01). Heavy tobacco smoking (> 10 pack-years) was associated with higher total cell numbers in BAL than was light tobacco smoking (< 10 pack-years). The MTS had a higher total BAL cell yield per milliliter than did the TS or the MS (p < 0.004). Marijuana smoking had a significant effect on cell yield independent of the presence or absence of concomitant tobacco smoking (p < 0.05). Macrophages were the predominant cells in the BAL of TS, MS, and MTS, as well as in the BAL of NS (⩾ 90%). The number of neutrophils (as total recovered or per milliliter of BAL fluid) was significantly higher in the BAL fluid of all MTS and TS than in that of NS (p < 0.01). We conclude that (1) smoking of marijuana and tobacco induces an alveolar cellular response; (2) the predominant cells in BAL fluid from either marijuana or tobacco smokers are alveolar macrophages; (3) heavy tobacco smokers appear to have a greater BAL cell yield than do lighter smokers; (4) concomitant smoking of marijuana and tobacco increases cell yield significantly above smoking tobacco alone or marijuana alone; (5) marijuana increases cell yield in both light and heavy tobacco smokers. These findings imply an adverse effect of marijuana smoking on the lungs that is independent of and additive to that of tobacco.