The pollen of Ambrosia artemisiifolia (ragweed) is an important aeroallergen. The plant originated from North America and, has spread worldwide in recent decades. Air masses can transport pollen grains far from their source region and episodes of long distance transported (LDT) of ragweed pollen have been reported. The allergenic properties of LDT pollen grains can be altered by humidity, temperature and UV radiation. The aims of the study are to detect the major allergen of ragweed (Amb a 1) in the atmosphere of uninfested areas and to compare daily Ambrosia sp. pollen grains with Amb a 1 amount per m(3) of air. Samples for allergen detection were collected by ChemVol (R) sampler. ChemVol (R) collects particles at 800 l/min and contains 2 impaction stages (PM > 10 mu m and 10 > PM > 2.5 mu m). Samples collected on to filters were obtained during a 63 day period in the year 2014. Amb a 1 was recorded on 54 days and pollen grains of ragweed on 43 days. Diurnal average Amb a 1 concentrations ranged between 0.29 and 263.3 pg per cubic meter of air and correlated positively with daily average ragweed pollen concentrations. The average seasonal Ambrosia pollen allergen potency was 2.57 pg Amb a 1/pollen. The air mass movement was simulated using the HYbrid Single-particle Lagrangian Integrated Trajectory (HYSPLIT) model and back-trajectory paths were computed for four episodes. The findings suggest that ragweed pollen allergens still survive after at least 48 h during transport over long distances from allochthonous regions and are therefore a potential trigger of allergic reactions even in areas where ragweed is not widely dispersed.