Abstract
A progressive global increase in the burden of allergic diseases has affected the industrialized world over the last half century and has been reported in the literature. The clinical evidence reveals a general increase in both incidence and prevalence of respiratory diseases, such as allergic rhinitis (common hay fever) and asthma. Such phenomena may be related not only to air pollution and changes in lifestyle, but also to an actual increase in airborne quantities of allergenic pollen. Experimental enhancements of carbon dioxide (CO) have demonstrated changes in pollen amount and allergenicity, but this has rarely been shown in the wider environment. The present analysis of a continental-scale pollen data set reveals an increasing trend in the yearly amount of airborne pollen for many taxa in Europe, which is more pronounced in urban than semi-rural/rural areas. Climate change may contribute to these changes, however increased temperatures do not appear to be a major influencing factor. Instead, we suggest the anthropogenic rise of atmospheric CO levels may be influential.
Highlights
Many factors have been proposed to explain the 20th century increase [1,2,3,4] in the burden of allergic respiratory diseases, the causes are still not fully understood [5]
In the present analysis of 1221 European pollen time series at 97 stations, we focus on yearly trends of the annual pollen index (API), a quantity universally defined as the sum of average daily pollen concentrations over the year
Our Spanish data cover a wider geographic range with varied water availability which may be more influential on API, of grasses, in Spain compared to more northern countries
Summary
Many factors have been proposed to explain the 20th century increase [1,2,3,4] in the burden of allergic respiratory diseases, the causes are still not fully understood [5]. Air pollution can influence both allergens and allergic subjects in many ways, making the former more potent and increasing the immune reaction of the latter [6]. These phenomena are insufficient to explain completely the increased rate of allergic diseases in humans [6]. It can be reasonably supposed that global change affects pollen timing and production [10,11]. These may contribute to the increasing trend in allergic diseases. Single studies on pollen quantities in recent years have been inconclusive, e.g. inconsistent trends for five pollen types at five sites in Western Europe [12], or a more consistent increase for many taxa in Thessaloniki, Greece [13]
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