Saharan Dust, Allergenic Pollen and High Air Pollution: A Detrimental Spring Cocktail for the English Population

Background: In beginning of April 2014 England again experienced “red rain”, which is due to long distant transport of Saharan dust. In 2014 this coincided with the worst air pollution episode in Southern England for more than a decade. We argue here, that when the Saharan dust episodes like this happens during spring in Northern Europe, then there is also a very large risk that this will cause a health damaging cocktail consisting of Saharan dust, aeroallergens and increased air pollution. It mainly depends on the path of the air masses.
Method: We explore observations of pollen from Worcester and coastal monitoring sites in England during the episode of Saharan dust. This is combined atmospheric modelling using the weather forecast model WRF and the particle dispersion model HYSPLIT.
Results: During the episode, southern air masses arrived at Worcester and the coastal sites, thus from the sea. All sites showed large amounts of birch pollen and detailed analysis at Worcester pollen grains from plants native to Southern Europe or North Africa. Foot print modelling with WRF-HYSPLIT shows that air masses pass France during their way from the area around the Mediterranean.
Conclusion: During episodes of Saharan dust, then the atmosphere is in a state that favours long distance transport to an extreme degree. When the air masses pass large continental areas like Central-Northern Europe during spring, there is a good possibility that a fraction of the passed areas will have flowering birch trees. The pollen will therefore enrich the already polluted air masses and also undergo long distance transport. This will cause a cocktail effect of Saharan dust, allergenic pollen and increased air pollution in areas like England.