We studied the pharmacologic properties of water soluble extracts of paper dust (PDE) using isolated guinea pig trachea. Dose response relationships between PDE's and contractions of guinea pig tracheal smooth muscle were established. Paper dust was obtained from separate sites in a paper re-cycling mill, early in the process (PD1) and late in the process (PD2). The effects of pre-treatment with mediator blockers (pyrilamine, atropine) arachidonic acid metabolite inhibitors (indomethacin, NDGA, LY 171883) and an intracellular calcium antagonist (TMB8) were examined and compared to results with similar experiments using cotton bract extracts. The effect of pre-treatment with capsaicin a neuropeptide releasing agent was also assessed. PD1 induced contraction was partially inhibited by all the mediator inhibiting agents as well as the receptor blocking agents with the exception of LY 171883. Similar findings were seen for PD-2 except that pyrilamine and indomethacin failed to block the bronchoconstrictor effect. Pretreatment with capsaicin enhanced the effects of PD-1 and 2. These studies suggest that water soluble extracts from the paper re-cycling industry cause airway smooth muscle constriction via mediator release.