Environmental drivers of the seasonal exposure to airborne Alternaria spores in Spain.

Alternaria conidia have high allergenic potential and they can trigger important respiratory diseases. Due to that and to their extensive detection period, airborne Alternaria spores are considered as a relevant airborne allergenic particle. Several studies have been developed in order to predict the human exposure to this aeroallergen and to prevent their negative effects on sensitive population. These studies revealed that some sampling locations usually have just one single Alternaria spore season while other locations generally have two seasons within the same year. However, the reasons of these two different seasonal patterns remain unclear. To understand them better, the present study was carried out in order to determine if there are any weather conditions that influence these different behaviours at different sampling locations. With this purpose, the airborne Alternaria spore concentrations of 18 sampling locations in a wide range of latitudinal, altitudinal and climate ranges of Spain were studied. The aerobiological samples were obtained by means of Hirst-Type volumetric pollen traps, and the seasonality of the airborne Alternaria spores were analysed. The optimal weather conditions for spore production were studied, and the main weather factor affecting Alternaria spore seasonality were analysed by means of random forests and regression trees. The results showed that the temperature was the most relevant variable for the Alternaria spore dispersion and it influenced both the spore integrals and their seasonality. The water availability was also a very significant variable. Warmer sampling locations generally have a longer period of Alternaria spore detection. However, the spore production declines during the summer when the temperatures are extremely warm, what splits the favourable period for Alternaria spore production and dispersion into two separate ones, detected as two Alternaria spore seasons within the same year.

Urban atmospheric levels of allergenic pollen: comparison of two locations in Salamanca, Central-Western Spain.

In this paper, differences in the pollen levels detected in two parts of Salamanca (a city in central-western Spain) have been revealed using two volumetric samplers. One sampler was located in the city centre and the other in a semi-natural zone. The two sampling devices were separated by a distance of 1.4 km. During the two-year study period, the most abundant allergenic pollen type was Poaceae, with peak values being detected in May. Maximum values were registered between April and June. The values obtained in both zones with regard to pollen seasonality were similar during the peak day, but the abundance of pollen grains detected in the semi-urban was higher, except for Olea pollen type. The atmospheric pollen season was similar in duration, except for some types belonging to the genera Plantago and Urticaceae, which showed divergent values most probably due to the influence of climatic conditions. The meteorological parameter most significantly correlated to pollen concentration was temperature, being negative for winter species and positive for plants preferring warmer climates. In addition, rainfall showed a negative correlation in most cases due to the influence of precipitation on the behaviour of atmospheric airborne pollen.

Near-ground effect of height on pollen exposure.

The effect of height on pollen concentration is not well documented and little is known about the near-ground vertical profile of airborne pollen. This is important as most measuring stations are on roofs, but patient exposure is at ground level. Our study used a big data approach to estimate the near-ground vertical profile of pollen concentrations based on a global study of paired stations located at different heights. We analyzed paired sampling stations located at different heights between 1.5 and 50 m above ground level (AGL). This provided pollen data from 59 Hirst-type volumetric traps from 25 different areas, mainly in Europe, but also covering North America and Australia, resulting in about 2,000,000 daily pollen concentrations analyzed. The daily ratio of the amounts of pollen from different heights per location was used, and the values of the lower station were divided by the higher station. The lower station of paired traps recorded more pollen than the higher trap. However, while the effect of height on pollen concentration was clear, it was also limited (average ratio 1.3, range 0.7-2.2). The standard deviation of the pollen ratio was highly variable when the lower station was located close to the ground level (below 10 m AGL). We show that pollen concentrations measured at >10 m are representative for background near-ground levels.

Assessing allergenicity in urban parks: A nature-based solution to reduce the impact on public health.

Urban parks play a key role in the provision of ecosystem services, actively participating in improving the quality of life and welfare of local residents. This paper reports on the application of an index designed to quantify the allergenicity of urban parks in a number of Spanish cities. The index, which records biological and biometric parameters for the tree species growing there, classifies parks in terms of the risk they pose for allergy sufferers, graded as null, low, moderate or high. In this initial phase, the index was applied to 26 green areas in 24 Spanish cities; green areas varied in type (urban park, historical or modern garden, boulevard, square or urban forest), size 1-100 ha), geographical location, species richness, number of trees and tree density (number of trees / ha.). The data obtained were used to calculate the percentage of allergenic species in each park, which varied between 17-67%; density ranged from 100 to 300 trees/ha. The index values recorded ranged from a minimum of .07 to a maximum of .87; a significant correlation was found between index value and both number of trees and tree density. Taking an index value of .30 as the threshold considered sufficient to trigger allergy symptoms in the sensitive population, 12 of the parks studied may be regarded as unhealthy at any time of the year. Corrective measures to mitigate the impact of pollen emissions include the implementation of nature-based solutions at various levels: planning and design, handling and management, and strengthening of urban green-infrastructure elements. The index proved to be a useful tool for environmental analysis, and complies with the principles of portability and scalability central to current and horizon scientific research.

Effects of meteorological factors on airborne bracken (Pteridium aquilinum (L.) Kuhn.) spores in Salamanca (middle-west Spain).

Temporal variation of airborne bracken (Pteridium aquilinum) spores concentration in Salamanca during 10 years from January 1998 to December 2007 were studied by using a Burkard spore trap, and correlations with some meteorological parameters were analyzed. The number of spores that were counted was very low, due probably to the distance between the spore trap and the main bracken populations which were located 70 km away from the city. Long-range transport caused by winds coming from the Second Quadrant (IIQ) is supposed to be responsible for the appearance of bracken spores in Salamanca. The season period from August to late October shows the most intense spore dispersal process, with an early morning distribution along the day. Years 2002 and 2007 with a low quantity of airborne spores were also characterized by low mean temperatures, always under 18 degrees C from May to June. Daily spore concentration shows positive correlation with temperature and sun hours but negative with IVQ winds and with relative humidity. No correlation between daily spore concentration and rainfall was found. Also, a positive correlation between number of spores and IIQ winds was observed during the main spore season (MSS) and prepeak period (PRE).