Atmospheric transportation of marihuana pollen from North Africa to the Southwest of Europe

As a result of aerobiological samples taken on the Costa del Sol (S. Spain), Cannabis sativa L. (marihuana) pollen was detected from May to September 1991–1996, always sporadically and usually during the afternoons. Sampling was by two volumetric spore traps set up in Malaga and Estepona, two coastal towns approximately 90 km apart. A study of the days when this pollen was recorded points to the movement of air masses from North Africa to southern Spain. Furthermore, the isentropic air trajectories calculated for these days reinforce the possibility of the pollen originating in marihuana plantations in northern Morocco (Rif). This study demonstrates the application of aerobiology to the control of the source, quantity and phenology of the crop.