Identifying key environmental factors to model Alt a 1 airborne allergen presence and variation.

Fungal spores, commonly found in the atmosphere, can trigger important respiratory disorders. The glycoprotein Alt a 1 is the major allergen present in conidia of the genus Alternaria and has a high clinical relevance for people sensitized to fungi. Exposure to this allergen has been traditionally assessed by aerobiological spore counts, although this does not always offer an accurate estimate of airborne allergen load. This study aims to pinpoint the key factors that explain the presence and variation of Alt a 1 concentration in the atmosphere in order to establish exposure risk periods and improve forecasting models. Alternaria spores were sampled using a Hirst-type volumetric sampler over a five-year period. The allergenic fraction from the bioaerosol was collected using a low-volume cyclone sampler and Alt a 1 quantified by Enzyme-Linked ImmunoSorbent Assay. A cluster analysis was executed in order to group days with similar environmental features and then analyze days with the presence of the allergen in each of them. Subsequently, a quadratic discriminant analysis was performed to evaluate if the selected variables can predict days with high Alt a 1 load. The results indicate that higher temperatures and absolute humidity favor the presence of Alt a 1 in the atmosphere, while time of precipitation is related to days without allergen. Moreover, using the selected parameters, the quadratic discriminant analysis to predict days with allergen showed an accuracy rate between 67 % and 85 %. The mismatch between daily airborne concentration of Alternaria spores and allergen load can be explained by the greater contribution of medium-to-long distance transport of the allergen from the major emission sources as compared with spores. Results highlight the importance of conducting aeroallergen quantification studies together with spore counts to improve the forecasting models of allergy risk, especially for fungal spores.

Effect of prevailing winds and land use on Alternaria airborne spore load.

Alternaria spores are a common component of the bioaerosol. Many Alternaria species are plant pathogens, and their conidia are catalogued as important aeroallergens. Several aerobiological studies showing a strong relationship between concentrations of airborne spore and meteorological parameters have consequently been developed. However, the Alternaria airborne load variation has not been thoroughly investigated because it is difficult to assess their sources, as they are a very common and widely established phytopathogen. The objective of this study is to estimate the impact of vegetation and land uses as potential sources on airborne spore load and to know their influence, particularly, in cases of long-medium distance transport. The daily airborne spore concentration was studied over a 5-year period in León and Valladolid, two localities of Castilla y León (Spain), with differences in their bioclimatic and land use aspects. Moreover, the land use analysis carried out within a 30 km radius of each monitoring station was combined with air mass data in order to search for potential emission sources. The results showed a great spatial variation between the two areas, which are relatively close to each other. The fact that the spore concentrations recorded in Valladolid were higher than those in León was owing to prevailing winds originating from large areas covered by cereal crops, especially during the harvest period. However, the prevailing winds in León came from areas dominated by forest and shrubland, which explains the low airborne spore load, since the main Alternaria sources were the grasslands located next to the trap. Furthermore, the risk days in this location presented an unusual wind direction. This study reveals the importance of land cover and wind speed and direction data for establishing potential airborne routes of spore transport in order to improve the Alternaria forecasting models. The importance of conducting Alternaria aerobiological studies at a local level is also highlighted.

How to select the optimal monitoring locations for an aerobiological network: A case of study in central northwest of Spain.

Airborne pollen concentration varies depending on several factors, such as local plant biodiversity, geography and climatology. These particles are involved in triggering pollinosis in a share of worldwide human population, and adequate monitoring is, therefore, important. However, the pollen traps in aerobiological monitoring networks are usually installed in cities, and the features of the whole territory are not taken into account. The aim of this study was to analyze what environmental parameters are more suitable as regards setting up monitoring stations throughout a territory in order to obtain an aerobiological network that can represent environmental diversity. The analysis was carried out in 13 locations in Castilla y León over an 8 year period. This is a favorable territory in which to conduct this type of study owing to its climatic features, orography and biodiversity. The ten most abundant pollen types in the region were analyzed, and a clustering analysis was calculated with different distances so as to obtain homogeneous groups of stations. Moreover, the clusters obtained were analyzed in combination with altitudinal and different bioclimatic parameters, which derived from temperature and precipitation. The result here shows that the Castilla y León aerobiological network RACYL represents most of the environmental variability of the territory. Furthermore, it can be divided into two clusters and five sub-clusters for which the start of the main pollen season is different. This corresponds with the division of the territory as regards bioclimatic conditions. The most important bioclimatic parameters were the seasonality of the precipitation and the maximum temperature of the warmest month, although orography must also be taken into account. All of these help discover the optimal places in which to install traps and could reduce the number of monitoring stations. This study additionally provides data for unmonitored areas with similar bioclimatic conditions to those monitored.

Towards a model of wet deposition of bioaerosols: The raindrop size role.

Bioaerosols play a major role in the plant life of ecosystems. In addition, they have a profound impact on human health, since they may cause lung diseases or allergies. The key objective of this study is to assess the below cloud scavenging effect of rainfall on pollen concentration. The analysis is based on a sampling carried out in León, Spain, between 2015 and 2018. The rainfall variables and the pollen concentrations have been obtained with a disdrometer and a volumetric Hirst type spore-trap, respectively. In order to evaluate the scavenging, three parameters have been calculated: scavenging efficiency (through the concentration-weighted average (%ΔC)), the scavenging coefficient (λ) and the percentage of events with a decrease in pollen concentration (%ES) also called events with effective scavenging. 71% of rain events presented an effective scavenging that affected all types of pollen. The %ΔC mean value of total pollen was 24 ± 18% (positive values indicate an effective scavenging) and the types of pollen with the highest values were Castanea and Cupressaceae (71 and 40%, respectively). A linear model (R2 = 0.94) to estimate the pollen concentration after rain was built with variables such as pollen concentration before rain and other variables from a weather station and a disdrometer. Furthermore, we have shown the possibility of knowing in real time the probable Cupressaceae pollen concentration, from the initial pollen concentration and the physical parameters of rain (such as raindrop size, rain intensity or volume swept by raindrops in their falling path).

Molecular aerobiology - Plantago allergen Pla l 1 in the atmosphere.

INTRODUCTION: Exposure to airborne pollen from certain plants can cause allergic disease, but allergens can also be found in non-pollen-bearing fractions of ambient air. This may explain why the allergic response in susceptible patients does not always coincide with the presence and magnitude of airborne pollen counts. Plantago pollen is an important cause of pollinosis in northern Mediterranean countries, but it is difficult to determine its incidence in allergies because Plantago pollen appears in the atmosphere at the same time as grass pollen. OBJECTIVE: The study aimed to investigate the relationship between the atmospheric concentration of Pla l 1 aeroallergen and Plantago pollen, and its incidence in a population group. MATERIALS AND METHOD: Pollen was sampled using a Hirst-type volumetric trap (Burkard) and Burkard Cyclone sampler (Burkard) for Pla l 1 allergen. Allergen was determined with a Pla l 1-specific ELISA. Serum-specific IgE levels to several plant allergens were measured with the EAST system. RESULTS: The aerobiological dynamics of Plantago pollen grains and Pla l 1 did not follow the same trend, whereas the sum of Plantago with some other pollen types showed a more similar behaviour. Of the 118 subjects tested, sera from 52 contained IgE to Plantago pollen, but only 5 were monosensitized. CONCLUSIONS: The presence of Pla l 1 in the atmosphere depends not only on Plantago pollen but also on the pollen of other species from the Oleaceae family. Knowledge of the behaviour of allergen Pla l 1 in the atmosphere can help understand better asthma exacerbations associated with aeroallergens.

The weak effects of climatic change on Plantago pollen concentration: 17 years of monitoring in Northwestern Spain.

Plantago L. species are very common in nitrified areas such as roadsides and their pollen is a major cause of pollinosis in temperate regions. In this study, we sampled airborne pollen grains in the city of León (NW, Spain) from January 1995 to December 2011, by using a Burkard® 7-day-recording trap. The percentage of Plantago pollen compared to the total pollen count ranged from 11% (1997) to 3% (2006) in the period under study. Peak pollen concentrations were recorded in May and June. Our 17-year analysis failed to disclose significant changes in the seasonal trend of plantain pollen concentration. In addition, there were no important changes in the start dates of pollen release and the meteorological parameters analyzed did not show significant variations in their usual trends. We analyzed the influence of several meteorological parameters on Plantago pollen concentration to explain the differences in pollen concentration trends during the study. Our results show that temperature, sun hours, evaporation, and relative humidity are the meteorological parameters best correlated to the behavior of Plantago pollen grains. In general, the years with low pollen concentrations correspond to the years with less precipitation or higher temperatures. We calculated the approximate Plantago flowering dates using the cumulative sum of daily maximum temperatures and compared them with the real bloom dates. The differences obtained were 4 days in 2009, 3 days in 2010, and 1 day in 2011 considering the complete period of pollination.

Changes to airborne pollen counts across Europe.

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[Formula: see text]) 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[Formula: see text] levels may be influential.

Distribuição de esporos de Cladosporium sppno ar atmosférico de Caxias do Sul, RS, Brasil,durante dois anos de estudo / Cladosporium spp spores distribution in the atmospheric air of Caxias do Sul-RS, Brazil, during a two-year study

Os esporos de fungos estão distribuídos em grande quantidade naatmosfera e, alguns deles, apresentam capacidade de causar doençasem seres humanos, animais e vegetais. Dentre os variados táxons destaca-se Cladosporium spp, um dos fungos mais cosmopolitas e de maiorconcentração no ar. Esporos de Cladosporium spp têm sido caracterizadoscomo importantes alérgenos.Objetivos: Medir as concentrações de esporos de Cladosporium sppna atmosfera de Caxias do Sul, RS, Brasil, durante os anos de 2001 e2002 e avaliar a relação destas, com parâmetros meteorológicos.Métodos: Amostras diárias foram coletadas, utilizando um aparelhotipo Hirst (Burkard®).Resultados: Os resultados mostraram que Cladosporium spp tempresença constante no ar. Em 2001 foram contabilizados 133.586 esporos/m3, com valor máximo diário de 3.265 esporos/m3 e mensal de24.912 esporos/m3, no mês de março. Em 2002 o número total foi de118.766 esporos/m3 com máximo diário de 4.470 esporos/m3 e mensalde 29.816 esporos/m3, em janeiro. A análise com os parâmetrosmeteorológicos mostrou correlação positiva com temperatura média enegativa com a umidade. Os períodos de maior concentração ocorreramcom temperaturas médias mais elevadas, no entanto, a umidade altatem um efeito negativo na distribuição destes esporos por favorecer ahidratação dos mesmos, que sedimentam ao solo.Conclusão: Os dados obtidos podem ser úteis nas áreas da patologiahumana, especialmente nos processos alérgicos, na patologia animal evegetal, em trabalhos com finalidades de preservação de acervo cultural,no controle de infecções e na ecologia.

Fungal spores are distributed in large amounts in the outdoor air, andsome of them may cause diseases in human beings, animals, and plants.Among several taxa, Cladosporium spp is one of the most ubiquitous andmost widely distributed, being found in high concentrations in the air.Cladosporium spp spores have been classified as important allergens,and are, therefore, important to the study of allergies.Objectives: To measure the concentrations of Cladosporium sppspores in the outdoor air of Caxias do Sul, Southern Brazil, during 2001and 2002, and to evaluate the association of these concentrations withmeteorological parameters.Methods: Daily samples were collected using a Hirst sampler(Burkard®).Results: The results showed that Cladosporium spp spores are oftenpart of the air. In 2001, the total amount was 133,586 spores/m3; withmaximum daily and monthly concentration of 3,265 spores/m3, and24,912 spores/m3 in March, respectively. In 2002, the total amount was118,766 spores/m3; with maximum daily and monthly concentration of4,470 spores/m3 and 29,816 spores/m3 in January. The meteorologicalparameters showed a positive correlation with the temperature averageand a negative one regarding humidity. The highest levels were found athigher temperature averages, however, elevated humidity has a negativeeffect on the distribution of these spores, contributing to their hydrationand deposition on the soil.Conclusions: The data obtained can be useful in human pathologyarea - especially in allergy - animal and plants pathology, in studies ofcultural inventory preservation, infection control and ecology.

Alternative statistical methods for interpreting airborne Alder (Alnus glutimosa (L.) Gaertner) pollen concentrations.

This paper reports on the behaviour of Alnus glutinosa (alder) pollen grains in the atmosphere of Ponferrada (León, NW Spain) from 1995 to 2006. The study, which sought to determine the effects of various weather-related parameters on Alnus pollen counts, was performed using a volumetric method. The main pollination period for this taxon is January-February. Alder pollen is one of the eight major airborne pollen allergens found in the study area. An analysis was made of the correlation between pollen counts and major weather-related parameters over each period. In general, the strongest positive correlation was with temperature, particularly maximum temperature. During each period, peak pollen counts occurred when the maximum temperature fell within the range 9 degrees C-14 degrees C. Finally, multivariate analysis showed that the parameter exerting the greatest influence was temperature, a finding confirmed by Spearman correlation tests. Principal components analysis suggested that periods with high pollen counts were characterised by high maximum temperature, low rainfall and an absolute humidity of around 6 g m(-3). Use of this type of analysis in conjunction with other methods is essential for obtaining an accurate record of pollen-count variations over a given period.

Variações anuais do conteúdo polínico de mimosa scabrella na atmosfera de Caxias do Sul, Brasil / Annual variation of the pollinic content of Mimosa scabrella in the atmosphere ofCaxias do Sul, Brazil

A família Mimosaceae está representada no município de Caxias do Sul por 10 gêneros e 37 espécies. O tipo polínico de maior representatividade na atmosfera é Mimosa scabrella, árvore de porte médio, muito indicada para reflorestamento. O monitoramento polínico atmosférico vem sendo realizado desde o ano de 2001, utilizando-se o captador volumétrico de sucção do tipo Hirst, modelo Burkard®, instalado no topo do Hospital Geral. A concentração total do tipo polínico Mimosa scabrella durante os anos de 2001 a 2006 foi 17.804 grãos de pólen, o que o situa em segundo lugar no espectro polínico da cidade. Em 2001, foram registrados 3.656 grãos de pólen, 2.087 grãos em 2002 e 4.379 em 2003, 1.928 em 2004, 1.524 em 2005 e 4.230 em 2006. Os picos mensais ocorreram no mês de agosto, com exceção do ano de 2003 que foi em setembro. Por sua elevada concentração, seria conveniente que estudos epidemiológicos futuros testassem extratos com antígenos desse pólen.

The Mimosaceae family is represented in the city of Caxias do Sul by ten genera and 37 species. The most representative pollinic type in the atmosphere is Mimosa scabrella, an average sized tree, between 10 and 12 m high, well suited for reforestation managing. The monitoring of atmosphere pollen is been held since the year of 2001 using a Hirst volumetric spore trap sampler, Burkard® model, placed on the roof of the citie´s General Hospital. The total pollen concentration of Mimosa scabrella from the year of 2001 to 2006 was 17,804 pollen grains/m³, which makes it the second most common in the city pollen specter. In 2001, 3,656 pollen grains/m³ were recorded, 2,087 in 2002, 4,379 in 2003, 1,928 in 2004, 1,524 in 2005, 4,230 in 2006. The monthly peaks occurred in August, except in the year of 2003 (September, in that case). For its high concentration, it should be convenient to future epidemiologic studies to test antigens extract of such pollinic type.

Concentração do pólen de Urticaceae na atmosfera de Caxias do Sul, RS, no período de 2001 a 2005 / Urticaceae pollen concentration in the atmosphere of Caxias do Sul, RS, in the period from 2001 to 2005

Objetivo: Este trabalho objetivou apresentar os resultados dos registros polínicos da família Urticaceae, durante o período de 1° de janeiro de 2001 a 31 de dezembro de 2005, e sua relação com os fatores meteorológicos. Método: O monitoramento polínico foi realizado utilizando-se o captador volumétrico de sucção modelo Burkard®, instalado no telhado do Hospital Geral da Universidade de Caxias do Sul, à altura de vinte metros aproximadamente. Resultados: A família Urticaceae apresenta plantas de porte arbustivo e herbáceo, e está representada na cidade de Caxias do Sul por cinco gêneros e sete espécies. Os grãos de pólen de Urticaceae considerados altamente alergênicos são liberados de forma explosiva na atmosfera, devido a seu pequeno tamanho e forma esferoidal. Durante o período de estudo as concentrações máximas registraram-se nos meses de outubro e novembro. O tipo polínico Urticaceae ficou em primeiro lugar no espectro polínico da cidade, representando 25,6% do total de grãos contabilizados. Conclusão: Do ponto de vista clínico, sendo o tipo polínico Urticaceae o mais representativo na atmosfera do município de Caxias do Sul, nos anos de 2001 a 2005, faz-se necessário realizar pesquisas utilizando extratos de pólen de espécies como Boehmeria Jacq e Urera Gaudich.

Effect of air temperature on forecasting the start of Cupressaceae pollen type in Ponferrada (Leon, Spain).

In order to survive periods of adverse cold climatic conditions, plant requirements are satisfied by means of physiological adaptations to prevent cells from freezing. Thus, the growth of woody plants in temperate regions slows down and they enter into a physiological state called dormancy. In order to identify the chilling and heat requirements to overcome the dormancy period of Cupressaceae pollen type in the south of Europe, we have carried out our study with aerobiological data from a 10-year (1996-2005) period in Ponferrada, León (Spain). For the chilling requirements the best result was with a threshold temperature of 7.1 degrees C and an average of 927 CH. Calculation of heat requirements was carried out with maximum temperature, with 490 growth degree days (GDD) needed, with a threshold temperature of 0 degrees C. We have used the 2002-2003, 2003-2004 and 2004-2005 periods in order to determine the real validity of the model. We have not used these years in developing the models. The dates predicted differ in only a few days from those observed: in 2002-2003 there was a difference of 11 days, in 2003-2004 predicted and observed dates were the same, but in 2004-2005 the difference obtained was of 43 days.

Allergenic proteins in Urtica dioica, a member of the Urticaceae allergenic family.

BACKGROUND: Allergy to the pollen of flowering plant species significantly affects the health of people in many parts of the world. Pollens of related genera usually share common antigens and are often, but not always, cross-reactive. Several studies have shown that Parietaria pollen is one of the most common causes of pollinosis in the Mediterranean area, whereas Urtica has no allergenic significance. OBJECTIVES: To report on the localization of Parietaria judaica major allergen in Urtica dioica pollen grains and on the detection of allergenic proteins in U. dioica pollen grains during the hydration-activation process. METHODS: A combination of transmission electron microscopy and immunocytochemical methods was used to locate allergenic proteins in U. dioica pollen grains after different periods of hydration-activation using the anti-Par j 1 (4.1.3.) monoclonal antibody and serum samples from allergic patients. RESULTS: No significant labeling was noted for Parj 1 allergen after 10, 15, and 20 minutes in the walls and cytoplasm. Slight labeling was observed for allergic proteins in the walls of U. dioica after 10 minutes of hydration, and no significant labeling was found after 15 and 20 minutes of hydration. CONCLUSIONS: Immunocytochemical methods confirmed the absence of cross-reactivity between 2 related genera, Parietaria and Urtica, and the lowest allergenic potential of U. dioica.

Prediction of airborne Alnus pollen concentration by using ARIMA models.

To take preventative measures to protect allergic people from the severity of the pollen season, one of aerobiology's objectives is to develop statistical models enabling the short- and long-term prediction of atmospheric pollen concentrations. During recent years some attempts have been made to apply Time Series analysis, frequently used in biomedical studies and atmospheric contamination to pollen series. The aim of this study is to understand the behaviour of atmospheric alder pollen concentrations in northwest Spain in order to develop predictive models of pollen concentrations by using Time Series analysis. The prediction line proposed for Oviedo and Ponferrada are similar (Arima 2,0,1) while in Vigo a more accurate model founded by Arima (3,0,1) and in Leon (1,0,1) was used. The results suggest that Ponferrada and Oviedo are the cities in northwest Spain where Alnus pollen allergic individuals should to take preventive measures to protect themselves from the severity of the pollen season. Alnus pollen values higher than 30 grains/m3, a quantity considered sufficient to trigger severe allergy symptoms of other trees of the Betulaceae family, could be reached during 25 days in some years. The predicted lines conformed with the observed values overall in the case of Leon and Ponferrada. Time Series regression models are especially suitable in allergology for evaluating short-term effects of time-varying pollen appearance in the atmosphere.

Dinâmica aeropalinológica da Gramineae na cidade de Caxias do Sul, RS / Aeropalynological dynamics of Gramineae in the city of Caxias do Sul, RS

Objetivo: Determinar a dinâmica aeropalinológica da familia Gramineae, na cidade de Caxias do Sul-RS, e proporcionar esta informação aos alergologistas e pessoas afetadas por polinose. Método: Para a obtenção das amostras de pólens aéreos, foi utilizado o captador volumétrico de sucção (modelo Burkard), instalado no telhado do Hospital Geral, a altura aproximada de 20 metros. Este trabalho refere-se às coletas realizadas nos anos de 2001 e 2002. Resultados: O grão de pólen de Gramineae foi encontrado na atmosfera de Caxias do Sul ao longo de todo o ano, apresentando maior incidência na primavera, sendo o mês de novembro de maior concentração polínica desta família. O tipo polínico Gramineae foi o que apresentou maior concentração de pólen na atmosfera, registrando 3269 grãos/m³ em 2001 e 2543 grãos/ m³ em 2002, totalizando 5812 grãos/ m³ durante o período de estudo. Conclusão: Gramineae apresentou os valores mais elevados no espectro polínico desta cidade. Há relação entre a concentração polínica de Gramineae com os dados metereológicos. Os resultados obtidos sobre este tipo polínico no ar atmosférico, bem como a época de incidência, são dados importantes para os especialistas que se ocupam do diagnóstico e tratamento da polinose.

Lipid transfer proteins in Parietaria judaica L. pollen grains: immunocytochemical localization and function.

Parietariajudaica L. (Urticaceae) pollen is considered one of the most common causes of allergic respiratory symptoms in the Mediterranean area. The localization of lipid transfer proteins (LTPs) in P. judaica mature and hydrated-activated pollen grains was investigated applying a combination of transmission electron microscopy (TEM) with immunocytochemical methods. Our results show that the content of LTPs in P. judaica pollen grains changes during the process of hydration. The localization of judaica LTPs in the cytoplasm and in the lipid bodies associated with vacuoles demonstrated that LTPs represent primarily intracellular proteins. On the other hand, exposure of the pollen grains to germination medium induced the release of LTPs from the pollen grain. Thus, LTPs are cytoplasmic proteins that are secreted to become available for pollen-stigma interactions and probably induce the IgE antibody responses in allergic patients.

Urticaceae pollen concentration in the atmosphere of North Western Spain.

Plants of the Urticaceae family can develop into a pest on soils enriched with nitrogen. Urticaceae pollen is a biohazard because it elicits severe pollinosis. Pollen grains were sampled by using a Lanzoni seven-day-recording trap from February 1995-December 2000 in the atmosphere of the city of Ponferrada (Leon, North Western Spain). The Spearman test was used to analyse the statistical correlation between Urticaceae pollen and certain meteorological factors in different main pollination periods. Maximum values are reached in June and July, minimum levels are recorded in January and December. The parameters bearing the greatest positive influence on the occurrence of Urticaceae pollen grains are: temperature (maximum, minimum and mean), humidity (absolute, wet-bulb temperature, dew point and mixing ratio) and south western wind direction; negative parameters are: relative humidity, rainfall and period without wind. The highest correlation coefficients were obtained with temperature and wet-bulb. Absolute humidity and wet-bulb temperature yielded better correlation than relative humidity; hence, these two parameters must be included in this type of study. The use of one main pollination period or another in statistical analysis has an influence on the coefficient value. The behaviour of the pollen grains in the atmosphere during the year also influences the results.

Bioclimatic indices as a tool in pollen forecasting.

The use of bioclimatic indices could be a major step forward in the methodology of pollen forecasting. The basis for this proposal is that simple meteorological parameters do not reflect the global status of the atmosphere, but merely some static measurements. However, pollen dispersal is, above all, a dynamic phenomenon, and this fact should be reflected in the variables we used to explain it. Here, we test the two methodologies for routine pollen forecasting by comparing correlation coefficients using the same daily Poaceae airborne pollen data base from León (6 years, from 1994 to 1999) as the dependent variable and either simple daily meteorological variables or compound daily bioclimatic indices as independent variables. Both simple and compound indices reproduced the same profile of evolution of plant eco-physiological requirements, as the length of the study period during the pollen season increased. However, for time frames larger than the main pollen period, bioclimatic indices gave superior coefficients, which seems to indicate that these could be more valuable for pre-season pollen forecasting. The continentality index produced the highest mean coefficient, higher than those generated by any meteorological variable. Furthermore, at least for a Mediterranean climate, site location and evapotranspiration in relation to precipitation seem to be the most promising factors for increasing success when forecasting Poaceae airborne pollen concentration.