Assessment of neural networks and time series analysis to forecast airborne Parietaria pollen presence in the Atlantic coastal regions.

Pollen forecasting models are a useful tool with which to predict episodes of type I allergenic risk and other environmental or biological processes. Parietaria is a wind-pollinated perennial herb that is responsible for many cases of severe pollinosis due to its high pollen production, the long persistence of the pollen grains in the atmosphere and the abundant presence of allergens in their cytoplasm and walls. The aim of this paper is to develop artificial neural networks (ANNs) to predict airborne Parietaria pollen concentrations in the northwestern part of Spain using a 19-year data set (1999-2017). The results show a significant increase in the length of time Parietaria pollen is in the air, as well as significant increases in the annual Parietaria pollen integral and mean daily maximum pollen value in the year. The Neural models show the ability to forecast airborne Parietaria pollen concentrations 1, 2, and 3 days ahead. A developed model with five input variables used to predict concentrations of airborne Parietaria pollen 1 day ahead shows determination coefficients between 0.618 and 0.652.

Fraxinus pollen and allergen concentrations in Ourense (South-western Europe).

In temperate zones of North-Central Europe the sensitization to ash pollen is a recognized problem, also extended to the Northern areas of the Mediterranean basin. Some observations in Switzerland suggest that ash pollen season could be as important as birch pollen period. The allergenic significance of this pollen has been poorly studied in Southern Europe as the amounts of ash pollen are low. Due to the high degree of family relationship with the olive pollen major allergen (backed by a sequence identity of 88%), the Fraxinus pollen could be a significant cause of early respiratory allergy in sensitized people to olive pollen as consequence of cross-reactivity processes. Ash tree flowers in the Northwestern Spain during the winter months. The atmospheric presence of Ole e 1-like proteins (which could be related with the Fra a 1 presence) can be accurately detected using Ole e 1 antibodies. The correlation analysis showed high Spearman correlation coefficients between pollen content and rainfall (R(2)=-0.333, p<0.01) or allergen concentration and maximum temperature (R(2)=-0.271, p<0.01). In addiction CCA analysis showed not significant differences (p<0.05) between the component 1 and 2 variables. PCFA analysis plots showed that the allergen concentrations are related to the presence of the Fraxinus pollen in the air, facilitating the wind speed its submicronic allergen proteins dispersion. In order to forecast the Fraxinus allergy risk periods, two regression equations were developed with Adjusted R(2) values around 0.48-0.49. The t-test for dependent samples shows no significant differences between the observed data and the estimated by the equations. The combination of the airborne pollen content and the allergen quantification must be assessed in the epidemiologic study of allergic respiratory diseases.

Airborne pollen trends in the Iberian Peninsula.

Airborne pollen monitoring is an effective tool for studying the reproductive phenology of anemophilous plants, an important bioindicator of plant behavior. Recent decades have revealed a trend towards rising airborne pollen concentrations in Europe, attributing these trends to an increase in anthropogenic CO2 emissions and temperature. However, the lack of water availability in southern Europe may prompt a trend towards lower flowering intensity, especially in herbaceous plants. Here we show variations in flowering intensity by analyzing the Annual Pollen Index (API) of 12 anemophilous taxa across 12 locations in the Iberian Peninsula, over the last two decades, and detecting the influence of the North Atlantic Oscillation (NAO). Results revealed differences in the distribution and flowering intensity of anemophilous species. A negative correlation was observed between airborne pollen concentrations and winter averages of the NAO index. This study confirms that changes in rainfall in the Mediterranean region, attributed to climate change, have an important impact on the phenology of plants.

Oleaceae cross-reactions as potential pollinosis cause in urban areas.

It is worth noting the allergological problems induced by a not accurate design of the ornamental vegetation in the parks and streets of the cities. Usually, in the Oleaceae family, only the olive pollen is considered an important aeroallergen but other species of the family could be an important source of airborne pollen allergens. Pollen from Fraxinus, Olea and Ligustrum and its main aeroallergens were sampled in the atmosphere of an urban area in North-Western Spain during 2011. The allergen bioaerosol content was quantified by using specific 2-site ELISA and Ole e 1 antibodies. The Fra e 1 and Lig v 1 allergens were detected by means Ole e 1 antibodies. This fact demonstrates the cross-reactivity between the main allergens of Fraxinus, Olea and Ligustrum, plants widely species used as ornamental in the cities. Therefore, the urban allergenic people sensitized to Olea pollen could present allergenic reactions during the winter (due to ash pollen allergens), the spring (caused by olive pollen allergens) and the early summer (triggered by the privet flowering). As a consequence, sensitivity to the pollen of one species may favour development of sensitivity to all three species as consequence of the priming effect. The combination of pollen count and the allergen quantification must be assessed in the epidemiologic study of allergic respiratory diseases.

Assessment of Quercus flowering trends in NW Spain.

This paper sought to chart airborne Quercus pollen counts over the last 20 years in the region of Galicia (NW Spain) with a view to detecting the possible influence of climate change on the Quercus airborne pollen season (APS). Pollen data from Ourense, Santiago de Compostela, Vigo and Lugo were used. The Quercus airborne pollen season was characterized in terms of the following parameters: pollen season start and end dates, peak pollen count, pollen season length and pollen index. Several methods, dates and threshold temperatures for determining the chill and heat requirements needed to trigger flowering were applied. A diverse APS onset timing sequence was observed for the four cities as Quercus flowers few days in advance in Vigo. The variations observed could be related to differences in the meteorological conditions or the thermal requirements needed for flowering. Thermal requirements differed depending on local climate conditions in the study cities: the lowest values for chilling accumulation were recorded in Vigo and the highest in Lugo, whereas the lowest heat accumulation was achieved in Vigo. Differences in APS trends between cities may reflect variations in weather-related trends. A significant trend towards rising Quercus pollen indices and higher maximum daily mean pollen counts was observed in Ourense, linked to the more marked temperature increase across southern Galicia. A non-uniform trend towards increased temperatures was noted over the study period, particularly in late summer and early autumn in all four study cities. Additionally, an increase in spring temperatures was observed in south-western Galicia.

Pollen Raman spectra database: application to the identification of airborne pollen.

Raman microspectroscopy allows a non-destructive identification of airborne particles. However, the identification of particles such as pollen is hindered by the absence of a spectral library. Although reference spectra of pollen have been published before, they have always been limited to a certain number of species. In this work, Raman spectra of 34 pollen types are presented and were used to build a pollen spectra primary library. Afterward, the applicability of this database for detecting and identifying pollen in airborne samples was tested. Airborne pollen samples collected during April, May and August were compared with blank pollen spectra by means of Hit Quality Index. Although a much larger library would be required, our results showed that all first hits correspond to the same blank pollen species of the questioned sample from the air. This possibility is an innovative idea and a promising line of investigation for future RAMAN technology development in the area of aerobiology.

Influence of pollen level on hospitalizations for asthma.

The effect of pollen level on asthma hospitalizations is still under debate. The aim of this study was to analyze hospital admissions due to asthma and its relation with environmental pollen and meteorological factors. During 13 years, we included every patient admitted with asthma as primary or secondary diagnosis. For this purpose, we used a case-crossover analysis to compare pollen concentrations at the time of admission with values of the same variables 2 to 6 days before admission. We included 6,687 hospital admissions. High maximum temperature and low humidity were associated with lower risk of asthma admissions. High mean pollen levels exerted a moderate effect and high maximum pollen levels led to a dramatic increase of hospital admissions due to asthma, especially among females. In conclusion, environmental pollen level increases the risk of asthma hospital admissions.

Evaluation of atmospheric Poaceae pollen concentration using a neural network applied to a coastal Atlantic climate region.

In the South of Europe an important percentage of population suffers pollen allergies, being the Poaceae pollen the major source. One of aerobiology's objectives is to develop statistical models enabling the short- and long-term prediction of atmospheric pollen concentrations to take preventative measures to protect allergic patients from the severity of the atmospheric pollen season. The implementation of a computational model based on supervised MLP neural network was applied for the prediction of the atmospheric Poaceae pollen concentration. There is a good correlation between the values predicted by the ANN for the training cases in comparison with the real pollen concentrations. A high coefficient of linear regression (R(2)) of 0.9696 was obtained. The accuracy of the neural network developed was tested with data from 2006 and 2007, which was not taken into account to establish the aforementioned models. Neural networks provided us a good tool to forecasting allergenic airborne pollen concentration helping the automation of the prediction system in the aerobiological information diffusion to the population suffering from allergic problems.

Modelo de predicción para Botrytis cinerea en un viñedo de Galicia (España) / Predictive model for Botrytis cinerea in a vineyard of Galicia, Spain

Se realizó un recuento de las esporas de Botrytis cinerea en la atmósfera de un viñedo de la comarca del Ribeiro (Galicia, España), durante tres años consecutivos. Para explicar su abundancia, dicha información se ha relacionado con las fases fenológicas de la vid y con la influencia que los principales parámetros meteorológicos ejercen sobre el contenido fúngico. Tras el estudio estadístico de los datos se ha elaborado un modelo predictivo (regresión polinomial) de la concentración de dichas esporas en la atmósfera.

During three consecutive years, the counting of Botrytis cinerea spores in the atmosphere of a vineyard in the region of Ribeiro (Galicia, Spain) has been carried out. To explain their abundance, such information has been related to the phonological stages of the vine and to the influence that the main meteorological parameters exert on the fungal content. Taking into account the statistical analysis of data, a predictive model (polynomial regression) for the concentration of these spores in the atmosphere has been prepared.

Poaceae pollen in Galicia (N.W. Spain): characterisation and recent trends in atmospheric pollen season.

Airborne Poaceae pollen counts are greatly influenced by weather-related parameters, but may also be governed by other factors. Poaceae pollen is responsible for most allergic reactions in the pollen-sensitive population of Galicia (Spain), and it is therefore essential to determine the risk posed by airborne pollen counts. The global climate change recorded over recent years may prompt changes in the atmospheric pollen season (APS). This survey used airborne Poaceae pollen data recorded for four Galician cities since 1993, in order to characterise the APS and note any trends in its onset, length and severity. Pollen sampling was performed using Hirst-type volumetric traps; data were subjected to Spearman's correlation test and regression models, in order to detect possible correlations between different parameters and trends. The APS was calculated using ten different methods, in order to assess the influence of each on survey results. Finally, trends detected for the major weather-related parameters influencing pollen counts over the study period were compared with those recorded over the last 30 years. All four cities displayed a trend towards lower annual total Poaceae pollen counts, lower peak values and a smaller number of days on which counts exceeded 30, 50 and 100 pollen grains/m(3). Moreover, the survey noted a trend towards delayed onset and shorter duration of the APS, although differences were observed depending on the criteria used to define the first and the last day of the APS.

Aeromicota de ambientes internos: comparación de métodos de muestreo / Aeromycota in indoor environment: sampling methods comparison

El procedimiento de muestreo utilizado para determinar el grado de contaminación fúngica en ambientes internos, difiere según los autores. Por ello, con el fin de conocer si el método utilizado por nuestro grupo de investigación, es comparable con otras metodologías, se ha realizado un estudio comparativo con varios sistemas de captación de esporas del aire, incluyendo equipos volumétricos (Aeroscope Chirana, System Air Sampler, Burkard Personal Culture) así como el método tradicional por sedimentación. Los resultados obtenidos muestran que apenas existen diferencias cuando se utilizan los sistemas volumétricos, sin embargo, el método por sedimentación ha sido menos eficaz, tanto desde el punto de vista cuantitativo como cualitativo. Mientras, el método directo por hisopado, resulta un buen complemento para determinar la fuente de contaminación. También se ha determinado la hora del día con mayor carga fúngica, que se localiza al mediodía y tras el análisis de varios medios de cultivo, se concluye que el Agar Glucosa de Sabouraud resulta adecuado para este tipo de investigaciones.

The sampling method used to determine the degree of fungal contamination in indoor environment differs, according to some authors. Therefore, with the purpose of knowing if the method used by our research team is comparable to other methodologies, a comparative study with various systems used to capture air spores has been carried out which include volumetric equipment (Aeroscope Chirana, System Air Sampler, Burkard Personal Culture) as well as the traditional method by sedimentation. Results have revealed that there is fairly some difference when volumetric systems are used; as to the sedimentation method, it has proved to be less effective both in the quantitative and qualitative point of view. On the other hand, direct method through sprinkling becomes a suitable tool to establish the source of contamination. Moreover it has been recorded the time of day when the greatest fungal load occurs, this being at noon so after the analysis of several culture media it has been concluded that Sabouraud Agar Glucose is suitable for this kind of research.

El género Aspergillus en la atmósfera de La Habana (Cuba) / The Aspergillus genus in the atmosphere of La Habana, Cuba

Se ha realizado un estudio de la contaminación fúngica ambiental en la atmósfera de la ciudad de La Habana (Cuba), durante el período de lluvias de los años 2001 y 2002, utilizando un método volumétrico viable, que ha permitido conocer la concentración de unidades formadoras de colonias (ufc/m3) totales y caracterizar los géneros y especies más abundantes, en especial del género Aspergillus. Durante el año 2001 las concentraciones más elevadas de hongos se obtuvieron en agosto y septiembre y las más bajas en julio, mientras que en el año 2002 destacan los niveles de septiembre y octubre frente a los escasos niveles del mes de agosto. Al analizar la densidad relativa de los géneros identificados se observa que Aspergillus es el género más abundante en la atmósfera seguido de Penicillium y Cladosporium. Las especies más abundantes en el año 2001 y relativamente constantes en el tiempo fueron A. japonicus, A. niger y A. flavus, mientras en el año 2002, los más abundantes fueron: A. japonicus, A. fumigatus y A. niger, siendo A. niger el único constante en el tiempo.

A study on environmental fungal contamination in the atmosphere of the City of La Habana (Cuba), during the rainy period in 2001 and 2002 was carried out. A viable volumetric method was used, making it possible to ascertain the concentration of units comprising total colonies (ufc/m3), and to characterize the most abundant genera and species, especially Aspergillus. Throughout 2001, the highest concentrations of fungi were collected in August and September, and the lowest in July; while in 2002, the highest levels were in September and October, compared to the minimal levels for the month of August. On analyzing the relative density of the genera identified, it was found that the most abundant genus in the atmosphere was Aspergillus, followed by Penicillium and Cladosporium. The most abundant species and relatively constant over time in 2001 were A. japonicus, A. niger and A. flavus while in 2002 A. japonicus, A. fumigates and A. niger; this specie was the only constant in time.

Análisis cuantitativo y cualitativo de la aeromicota aislada de la Catedral de Santiago de Compostela (Galicia, España) / Quantitative and qualitative analysis of the airborne fungi isolated in the Cathedral of Santiago de Compostela (Galicia, Spain)

Mediante un estudio de la presencia de mitosporas fúngicas atmosféricas en el interior y exterior de la Catedral de Santiago de Compostela (España) durante un año, a través de un sistema de captación volumétrico viable, se identificaron 28 taxa, principalmente: Alternaria, Aspergillus, Cladosporium y Penicillium. Desde el punto de vista cuantitativo no existen diferencias significativas entre interior/exterior, y en ambos casos las concentraciones son ligeramente más elevadas en primavera-verano. Las especies más abundantes fueron: Penicillium purpurogenum Stoll, con un 94 por ciento en la atmósfera interna y un 82 por ciento en el exterior y Aspergillus fumigatus Fres., con un 65 por ciento y un 63 por ciento respectivamente.

A study was carried out on the atmosphericfungal content in the Cathedral of Santiago deCompostela (Spain) and its exterior during a year, usinga viable volumetric collecting system. A total of 28 taxawere identified, the most abundant of which were:Alternaria, Aspergillus, Cladosporium and Penicillium.In quantitative terms there were no significant indoor/outdoor differences, and the concentrations were slightlyhigher in Spring-Summer in both cases. The mostabundant species were Penicillium purpurogenum Stoll,with 94 percent in the indoor atmosphere and 82 percent outdoors,and Aspergillus fumigatus Fres., representing 65 percent inthe indoor and 63 percent outdoors.

Comportamiento temporal de las mitosporas de Cladosporium en la atmósfera de Galicia (España) / Temporary behaviour of Cladosporium mitospores in the atmosphere of Galicia, Spain

Se ha realizado el recuento de las mitosporas de poblaciones de Cladosporium en la atmósfera de ocho ciudades de Galicia (España), mediante un sistema de captación volumétrica no viable, obteniéndose un total de 40 registros anuales. Los valores promedio de los años de estudio oscilaron entre 96.726 mitosporas en Coruña y 326.898 en Trives, destacando en todas las localidades una mayor abundancia de las mismas durante la época estival. El máximo diario de Cladosporium cladosporioides se registró en Ourense (7.556 mitosporas/m3 el 8 de septiembre de 2004) mientras que el de Cladosporium herbarum correspondió a Trives (7.130 mitosporas/m3 el 8 de julio de 2003). El modelo de comportamiento intradiario varió según la localidad, pero en general se observó una mayor concentración de mitosporas a partir de las 13h.

By using a non viable volumetric capturing system it was possible to count populations of Cladosporiummitospores in the atmosphere of eight cities of Galicia (Spain), yielding a total of 40 annual records. Average values of the examined years ranged from 96.726 mitospores in Coruña and 326.898 in Trives, the highest abundance occurring during summer in all the localities. The daily maximum of Cladosporium cladosporioides was recorded in Ourense (7.556 mitospores/m on September 2004) while that of Cladosporium herbarum was detected in Trives (7.130 mitospores/m on july 8 2003). The intradaily model of behaviour varied according to the locality yet in general a major mitospore concentration could be observed sinceone o´clock p.m.

Concentraciones atmosféricas de propágulos fúngicos en viñedos del Ribeiro (Galicia, España) / Atmospheric concentrations of fungal propagules in vineyards of Ribeiro valley (Galicia, Spain)

Con el fin de conocer la incidencia de la podredumbre gris, el oidio y el mildiu y contribuir a paliar sus efectos en la vid mediante la aplicación de un tratamiento fitosanitario adecuado, se ha realizado un estudio de la concentración atmosférica de los conidios de Botrytis y Uncinula y los esporangios de Plasmopara, en un viñedo de la provincia de Ourense (Galicia, España), durante la época vegetativa del cultivo en el año 2004. De los tres fitopatógenos estudiados, se han encontrado cantidades importantes de Botrytis, con un total de 6.519 conidios y Uncinula con 1.554 conidios, ambos presentes en la atmósfera preferentemente entre las 19-20 h. La concentración de esporangios de Plasmopara, ha sido inferior, con un total de 311 esporangios, registrándose los picos más elevados entre las 17-18 h. A partir de los datos de las concentraciones diarias de estos propágulos, se ha analizado estadísticamente la influencia de las variables meteorológicas sobre su presencia en la atmósfera, destacando positivamente la humedad absoluta y la temperatura de rocío, sobre la concentración de conidios de Botrytis y esporangios de Plasmopara y la temperatura máxima para los conidios de Uncinula. Se han desarrollado modelos de predicción de los niveles de estos propágulos, que podrían ser de gran utilidad para la valoración del riesgo de infección.

With the purpose of knowing the incidence of grey mould, powdery mildew and downy mildew and thusminimize their effect on vineyards through the application of a suitable fungicide treatment, we studied the atmospheric concentrations of conidia of Botrytis and Uncinula together with the sporangia of Plasmopara in a vineyardlocated in the province of Ourense (Galicia, Spain), in the year 2004, during the vegetative stage of the growing. Among the three topathogenous examined, a high number of Botrytis, with a total of 6.519 conidia and Uncinula, with 1,554 conidia was detected, both being present in the atmosphere mainly within 19 -20 h. Theconcentration of Plasmopara sporangia has been lower, with a total of 311, the highest peak being recorded within 17-18h. Based on data collected from dailyconcentrations of these propagules, the influence of meteorological fluctuations on their presence in the atmosphere has been statistically analysed, and it hasbeen concluded that absolute humidity as well as temperature of dew have positive effects on the concentration of Botrytis conidia and Plasmopara sporangia whereas maximum temperature shows similar results in the case of Uncinula conidia. Predictive models regarding the levels of these propagules were developed in order to ascertain risk of infection.

Artificial neural networks as a useful tool to predict the risk level of Betula pollen in the air.

An increasing percentage of the European population suffers from allergies to pollen. The study of the evolution of air pollen concentration supplies prior knowledge of the levels of pollen in the air, which can be useful for the prevention and treatment of allergic symptoms, and the management of medical resources. The symptoms of Betula pollinosis can be associated with certain levels of pollen in the air. The aim of this study was to predict the risk of the concentration of pollen exceeding a given level, using previous pollen and meteorological information, by applying neural network techniques. Neural networks are a widespread statistical tool useful for the study of problems associated with complex or poorly understood phenomena. The binary response variable associated with each level requires a careful selection of the neural network and the error function associated with the learning algorithm used during the training phase. The performance of the neural network with the validation set showed that the risk of the pollen level exceeding a certain threshold can be successfully forecasted using artificial neural networks. This prediction tool may be implemented to create an automatic system that forecasts the risk of suffering allergic symptoms.

Comportamiento temporal de mitosporas de Alternaria en la atmósfera de Santiago de Compostela (Galicia, España) / Temporary behaviour of Alternaria mitospore in the atmosphere of Santiago de Compostela (Galicia, España)

Mediante un sistema de captación volumétrico no viable, se presenta el recuento de mitosporas de poblaciones de Alternaria en la atmósfera de Santiago de Compostela (Galicia, España) durante el período 1997-2003. Los totales de mitosporas anuales variaron entre 439/m3 en el año 2001 y 3.107/m3 en 1997, localizándose los máximos mensuales en julio o septiembre según el año. El máximo diario fue de 653/m3 (9 de julio de 1997) y el comportamiento intraordinario señala una mayor abundancia de estas entre las 17h y las 20h. Las correlaciones con los parámetros metereológicos señalan una influencia negativa de la lluvia y la humedad y positiva del grado de insolación y la temperatura, siendo ésta última la más influyente en el contenido atmosférico de mitosporas.

Incidence of pollinosis in the city of A Coruña: correlation with aerobiological data.

An atmospheric pollen count was carried out in the city of A Coruña during 1999 using two pollen traps located at two different points in the city. A total number of 6979 and 3536 pollen grains, respectively, were identified, the majority during the Spring and Summer. Further, patients living near the pollen traps were selected from among those diagnosed as suffering from respiratory allergies by the Allergy Department of A Coruña's Juan Canalejo Hospital. The patients had at least one positive skin test for some pollen type, had not received immunotherapy in the last year, and were willing to fill in a symptoms booklet during the study period. The results obtained reveal the pollen types that produce the greatest number of skin sensitization cases (Poaceae, Plantago, Chenopodium and Parietaria), with a positive correlation between the atmospheric pollen concentration of such taxa and the frequency of allergy symptoms. This has enabled the setting of pollen values, above which A Coruña's inhabitants are considered to be at risk.

Phenological behaviour of Quercus in Ourense (NW Spain) and its relationship with the atmospheric pollen season.

Knowing the beginning of the pollen season is of particular importance to people allergic to a given pollen. Phenological studies in combination with aerobiological studies enable us to observe the relationship between the reproductive phenology of the species and their airborne pollen curves. They also enable us to study the relationship between the release of pollen from anthers and its presence in the atmosphere. The objectives of this study are (1) to determine chill and heat requirements for different phenological phases in the Quercus species present in Ourense (Spain), (2) to verify the synchronization between the flowering event and the presence of Quercus pollen in the air, (3) to select the best criterion for determining the onset of the pollen season according to phenological data, and finally, (4) to obtain models enabling us to determine the onset of the pollen season. Pollen monitoring was carried out from 1993 to 2001, by means of a 7-day Lanzoni VPPS pollen trap and, in order to characterize the floral phenophase of different Quercus species, a sampling method was applied from February to June 2001. We observed that climatic and biotic factors can produce a delay in the onset of the pollen season. Temperatures above 8 degrees C and between 6 degrees C to 8 degrees C are good threshold temperatures for estimating chill and heat requirements respectively. Medium-distance transportation of Quercus robur and Quercus pyrenaica pollen from areas 10-30 km away influences the concentrations of Quercus pollen registered in Ourense.

Parietaria pollinosis in an Atlantic area: clinical and palynological data.

BACKGROUND: Parietaria pollen is considered as one of the most common causes of allergic respiratory symptoms in the Mediterranean area but its presence is limited in the Atlantic area. Some leading patients from Muros, a small town on the Spanish Atlantic coast, complaining of nearly all year round respiratory symptoms happened to be allergic to Parietaria pollen. AIM OF THE STUDY: To evaluate the prevalence of Parietaria sensitization among patients from this Atlantic town, and its correlation with aerobiological data (concentration of Urticaceae pollen). PATIENTS AND METHODS: Eighty-nine patients suffering from rhinoconjunctivitis and/or asthma from the area of Muros between January 1998 and January 1999 were included. Skin prick tests and serum-specific IgE (CAP Pharmacia) to Parietaria judaica and a battery of perennial or seasonal allergens were performed. Information about the seasonal and hourly rhythm of symptoms was obtained in each patient sensitized to Parietaria pollen. Atmospheric pollen was collected, using a Hirst-type volumetric pollen sampler, during 1998. RESULTS: Parietaria allergy was detected in 22 patients (25%) and represented the second most important aeroallergen after mites and along with grass pollen. The total atmospheric pollen recorded in Muros during the study period was 27,515 pollen grains, Urticaceae being the most important one (18,554 grains, 67% of the total). The proportion of Urticaceae pollen found in Muros was the highest among all samplers belonging to the Spanish Aerobiology Network. Maximum values of Urticaceae pollen were recorded during May and June. Intradiurnal variation of pollen counts showed maximum values between 11 a.m. and 1 p.m. A parallelism was observed between the rate of symptomatic patients and Parietaria type grain pollen count. CONCLUSION: The prevalence of Parietaria pollen sensitization seems to be very important in this Atlantic area. The presence of very high levels of this pollen in its atmosphere explains this fact. Such sensitization should be taken into account concerning specific diagnostic tests.