In eastern Spain, studies combining the tracking and meso-scale circulations of air pollutants with the evaluation of their effects on plants have been undertaken since 1994. Meso-scale processes are very important from the point of view of how and where forest ecosystems are affected by point sources and regional air pollution in the Mediterranean area. The first results of these field surveys show that in 1994, 1995 and 1996, the distribution pattern of ozone visual injury (chlorotic mottle) in Pinus halepensis correlated with the penetration of pollutants transported by the sea-breeze into coastal valleys of Castellón (eastern Spain). In this tree species, longer needles are associated with higher chlorotic mottle, and ozone injury seems to be among the factors affecting needle retention and crown transparency.