Rising carbon dioxide (CO2) emissions have been linked to a rise in pollen counts in European cities in a new study.
A progressive rise in respiratory diseases, such as asthma and hay fever, has occurred across Europe over the last 50 years. Researchers analysed data taken from 97 monitoring stations in 13 different European countries over the last 32 years. The data included pollen counts for 23 different species of tree and plant.
The researchers then compared the pollen count to trends in temperature and geography. The results show an increasing trend in the yearly amount of airborne pollen in Europe, which was more noticeable in urban areas compared with semi-rural/rural areas.
The researchers concluded that increased temperatures could not be linked to this rise in pollen counts. As urban sites demonstrated significantly higher trends than rural areas, the researchers suggest that man-made increases in atmospheric CO2 levels could be responsible as they report higher levels of the pollutant than the countryside.
The study also highlights some elements of urban planning, such as using trees for ornamental purposes in city centre, as a factor contributing to pollen levels in cities. The researchers conclude that as their results do not demonstrate a clear cause, more research is needed to understand the rise in asthma and hay fever in Europe.