The diurnal variation of Poaceae pollen concentrations in a rural area

Records of Poaceae pollen concentration from three years of sampling in a rural area of West Wales have revealed distinctive circadian patterns of variation. Maximum pollen concentrations are typically recorded between 14.00 and 16.00 hours, on days both above and below an average daily Poaceae pollen count of 50 grains m^-3, although later peaks in concentration may be recorded during periods with no precipitation. Variations in the periodicity of Poaceae pollen are analysed in relation to meteorological conditions, phenological patterns of pollen release, pollen source area, and the magnitude of the average daily pollen count. The time of peak pollen concentration in West Wales is generally earlier than in other studies and this is explained by this study being conducted closer to Poaceae pollen source areas than most urban-based studies.     

Diurnal variation of pollen concentration in the air of north-central london

Pollen concentrations recorded during three years sampling in north-central London have shown distinctive diurnal variations. This paper identifies these patterns for three pollen taxa and attempts to account for the variations observed. The diurnal variations identified are interpreted in relation to meteorological conditions, pollen source area and phenological patterns of pollen release. A hypothesis of pollen dispersal to the sampling site is suggested.     

Differences in atmospheric emissions of Poaceae pollen and Lol p 1 allergen

The allergens of different grass species share similar physicochemical and immunological features that account for the high incidence of allergenic cross-reactivity. We aimed to gain more information on the correlation between Poaceae airborne pollen and allergen concentration and hence make a reliable assessment of true pollen exposure in different bioclimatic areas. The release of Lol p 1 allergen from grass pollen differs between years and areas depending on variables like meteorological factors, biological sources, and cross-reactions with homologous allergens. This study monitored airborne pollen concentrations of grasses and Lol p 1 aeroallergen in León and Ourense, two cities with different climatic conditions located in northwestern Spain. Lol p 1 content in aerosol samples was quantified using specific ELISA antibody plates. Some our results show that Lol p 1 concentration increases when the atmospheric relative humidity is below 70%. This could explain the appearance of protein peaks at times when little or no grass pollen is present, especially after a short and heavy storm.     

Evidence of long-distance transport of mountain cedar pollen into Tulsa, Oklahoma

 Previous study of Cupressaceae pollen in the Tulsa atmosphere during December and January suggested that the source of this pollen is the Juniperus ashei (mountain cedar) populations that occur mainly in southern Oklahoma and central Texas. The present investigation examined the evidence of long-distance transport of pollen from these populations during the 1996/1997 season at three sites in Oklahoma using Burkard traps. Two of the pollen-monitoring stations were operated in conjunction with Mesonet meteorological stations. It was found that the December and January Cupressaceae pollen occurs outside of the local season at Tulsa. Pollen concentrations are intermittent and correspond to days of peak concentrations at sites nearer the mountain cedar populations. Peak concentrations are associated with winds coming from the south over the mountain cedar areas. Diurnal rhythms show night-time peaks with a delay in timing at the northern-most site. These results are all consistent with the hypothesis that pollen is being transported over long distances from the mountain cedar populations to Tulsa, Oklahoma. These findings are important as they represent one of the few incidences of long-distance transport of pollen in significant concentrations to an area where the source vegetation is not present. Pollen-monitoring sites located in conjunction with Mesonet meteorological stations provide a unique opportunity to further examine atmospheric conditions during long-distance transport events. This will aid future studies of the spatial modeling of long-distance dispersal of pollen. Received: 20 October 1997 / Revised: 24 June 1998 / Accepted: 26 June 1998     

Micro-regional hypersensitivity variations to inhalant allergens in the city of Zagreb and Zagreb County

Depending on the geographic and climatic region and vegetation, allergenic plants are characteristic for certain areas and the pollen concentrations of various plant species depend on the fenophase of each single species and most of all on the climatic and meteorological conditions of a certain area. It is precisely because of these specific characteristics that the hypersensitivity of patients to various types of pollen allergens differs according to the geographic regions. The aim of this paper is to determine the frequency of inhalation allergies in adult population (> 19 years of age) caused by single types of allergens according to the defined space units (micro-regions) with special emphasis on the rural and urban areas. A number of 2,192 patients have been tested for allergy skin prick tests over a period of four years. Every patient was asked to fill in the questionnaire which contained 29 questions. The results of skin prick testing show that out of a total of 2,192 patients 86.72% were sensitized to pollen, 36.45% to mites, 2.46% to spores of fungi and mould and 5.1% of patients to other allergens which include the allergens of cockroaches, feathers and animal hair (p < 0.001). The largest number of poly-sensitized persons allergic to pollen allergens was sensitized to allergens from the pollen of plants that belong to the botanical family of grass. There were 25.36% patients mono-sensitized to individual allergens. In the northern and western parts of the city and the county, the majority of persons were sensitized to the birch pollen allergens, and this is statistically much more than the share of patients with the place of residence in the southern and eastern parts of the city and the county. In the southern and eastern locations prevails the share of sensitized persons to ambrosia which is statistically much more than the share of patients with the place of residence in the northern and western part of the city and the county.     

Factors affecting pollination ecology of Quercus anemophilous species in north-west Spain

Pollination ecology of Quercus is influenced by meteorological, biotic and genetic factors. This study was undertaken to ascertain the effect induced by these factors on pollen production, release and dispersion. Aerobiological data have been used in recent years as phenological information, because the presence of pollen in the air is the result of flowering across a wide area. The onset of the Quercus pollen season and the atmospheric pollen concentrations during the pollination period in two localities of north-west Spain (Ourense and Santiago) were determined from 1993 to 2001. There were important variations in total annual pollen as a result of meteorological conditions, lenticular galls produced by Neuropterus on catkins and biennial genetic rhythms of pollen production. In order to determine the beginning of flowering, a thermal time model has been used. Chill requirements were around 800 chilling hours (CH) and heat requirements were 953 growth degree days (GDD in °C) in Santiago and 586 GDD in Ourense. Pollen in the air show positive correlation (99% significance) with daily thermal oscillation, maximum and minimum temperatures, and hours of sunshine. Regression analysis with previous days' pollen concentrations explained the high percentage of pollen concentration variability, as meteorological variables do not, on their own, explain pollen production and release.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 149 , 283–297.     

An assessment of predictive forecasting of <Emphasis Type="Italic">Juniperus ashei</Emphasis> pollen movement in the Southern Great Plains,USA

Juniperus ashei pollen, a significant aeroallergen, has been recorded during December and January in Tulsa, Oklahoma, over the past 20 years. The nearest upwind source for this pollen is populations growing in southern Oklahoma and central Texas, at distances of 200 km and 600 km respectively. Long-distance dispersal of J. ashei pollen into the Tulsa area shows a strong correlation with the trajectories of wind blowing across southern populations before traveling north towards eastern Oklahoma. The strong tie between climatic conditions and the occurrence of this aeroallergen within the Tulsa, Oklahoma, atmosphere provided a unique opportunity to forecast the dispersal, entrainment, and downwind deposition of this significant aeroallergen. Forecasts of long-distance J. ashei pollen dispersal began during the winter of 1998/1999. Each forecast uses defined climatic parameters to signal pollination at each source site. Coupled to these estimates of pollen release, forecast weather conditions and modeled wind trajectories are used to determine the threat of dispersal to downwind communities. The accuracy of these forecasts was determined by comparing the forecast "threat" to aerobiological records for the same period collected in the "Tulsa region". Analysis of the two seasons revealed only a single occurrence of "high" or "very high" pollen concentrations in Tulsa not directly linked to "moderate" or "severe" forecast threats from the southern source areas.     

Cumulative temperatures for prediction of the beginning of ash (Fraxinus excelsior L.) pollen season

The aim of this study is the analysis of the meteorological conditions leading to the release of ash pollen in order to predict the beginning of the pollen season in Zurich, Switzerland. For 12 years over a period of 14 consecutive years, it appears that ash pollen release begins when the cumulated mean daily temperatures starting on January 1 reach 220.7°C, admitting a variation of ±30°C that more or less corresponds to 3 consecutive days at 10°C.     

The combination of airborne pollen and allergen quantification to reliably assess the real pollinosis risk in different bioclimatic areas

Exposure to allergens represents a key factor among the environmental determinants of asthma. The most common information available for pollinosis patients is the concentration of pollen grains in the bioaerosol and their temporal distribution. However, in recent years, discordance between pollen concentrations and allergic symptoms has been detected. The purpose of this research is to evaluate the relationship between pollen counts and the atmospheric aeroallergen concentrations in different Spanish bioclimatic areas. For the monitoring of allergen content in the air, a quantitative antigen–antibody technique combined with the Cyclone sampling methodology was used. The study was conducted during 2007 by considering some of the most common allergens that induce pollinosis in each area: Platanus and Urticaceae in Ourense and Cartagena, and Poaceae in Ourense and León. In Ourense, pollen counts and aeroallergen concentrations coincided for the three pollen types studied, and the pollen and allergen data associated with the meteorological factors were highly significant for the pollen counts. In Cartagena (for Platanus and Urticaceae) and León (for Poaceae), the low correlations between pollen counts and allergen concentrations obtained could be due to the specific bioclimatic conditions. In contrast, the higher allergen concentrations found in the atmosphere in Cartagena and León compared to Ourense could be related to the existing pollutant levels there, inducing a higher expression of plant pathogenesis-related proteins in the plants of polluted cities. The combination of pollen counts and allergen quantification must be assessed to reliably estimate exposure of allergic people to allergens in different bioclimatic areas.     

Urban airborne pollen in a semiarid environment

The present investigation was conducted to determine the pollen types and their quantities in the atmosphere of Obregón City (a semiarid region) and establish the relationship with meteorological parameters in 2008 and 2011. A bimodal pattern with peaks in dry warm (spring) and late rainy (autumn) seasons was observed. The highest monthly pollen indexes were observed in October 2008 and September 2011. Precipitation in 2008 was 2.6 times higher than in 2011, beginning in June in both years, and ending in November (2008) and September (2011). Main pollen types were Poaceae, Chenopodiaceae/Amaranthaceae, Asteraceae and Parkinsonia (the latter was dominant in the dry warm season). Statistical correlations (Spearman’s rank-order correlation p < 0.05) with meteorological parameters were performed. In both sampling years, relative humidity caused adverse effects on the atmospheric pollen content, while temperature, solar radiation and wind speed in the dry season were associated with increased pollen indexes. Compared to other studies of semiarid areas, the pollen index at Obregón is low, which is attributed to a relatively high humidity and to the large area of grain crops surrounding the city.     

Airborne behaviour of <Emphasis Type="Italic">Echium</Emphasis> pollen

Species of Echium are clearly entomophilous, but they release great amounts of pollen into the atmosphere with its consequent anemophilous transport, because their high pollen production, the smallness of the grains, and the exserted position of their anthers. Using three volumetric airborne sporetraps in Extremadura (SW of Spain) between 1994 and 1998, we found that Echium pollen reached pollen concentrations similar to or greater than other anemophilous plants. The main pollination period appeared from April to June. The maximum peak daily concentration reached 35.9 grains/m³ and the annual recorded totals showed interannual variations between 64.2 and 614.4. Correlations were calculated between the daily pollen concentrations and the meteorological parameters rain, temperature, wind direction and velocity and relative humidity. Wind direction seems to be significant, warm dry air seems to facilitate the release of pollen into the atmosphere and increase its concentrations. Hourly pollen concentration reached a maximum between 11:00 and 12:00 and a minimum at 07:00, and the patterns were very similar in the three localities studied. This would indicate that the presence of Echium pollen in the atmosphere is related to the processes of anthesis of the populations near the traps, and would not correspond to a model of transport from distant zones.     

Multivariate statistical forecasting modeling to predict Poaceae pollen critical concentrations by meteoclimatic data

Forecasting pollen concentrations in the short term is a topic of major importance in aerobiology. Forecasting models proposed in the literature are numerous and increasingly complex, but they fail in at least 25 % of cases and are not available for all botanical species. This work makes it possible to build a forecast model from meteorological data for estimating pollen concentration over a certain threshold of Poaceae, an allergenic family. In Italy, about 25 % of the population suffer from allergies, these in 80 % of cases being caused by airborne allergens, including taxa of agricultural interest such as Poaceae. The pollen dispersion in air is determined by both the phenological stage of plants and the meteorological conditions; the pollen presence varies according to the year, month and even the time of the day. There is a correlation between environmental factors, pollen concentrations and pollinosis. A partial least squares discriminant analysis approach was used in order to predict the presence of Poaceae pollen in the atmosphere with a time lag of 3, 5, 7 days, on the basis of a data set of 14 meteorological and pollen variables over a period of 14 years (1997–2010). The results show a high accuracy in predicting pollen critical concentrations, with values ranging from 85.4 to 88.0 %. This study is hopefully a positive first step in the use of a statistical approach that in the next future could have clinical applications.     

Enhanced airborne radioactivity during a pine pollen release episode

 A single episode of pine pollen release in the highly contaminated area of Novozybkov, Russian Federation, which led to enhanced atmospheric concentrations of ¹³⁷Cs is discussed. The pollen grains were sampled by a rotating arm impactor and analysed by gamma-spectrometry for ¹³⁷Cs activity and by image analysis for their size. In the vicinity of a forest, a maximum concentration of 4.5±0.4 mBq m^–3 was measured, and a mean activity per pollen grain of 260±80 nBq was determined. The emission rate of the Novozybkov mixed pine forest was estimated to be approximately 400 Bq m^–2 per year. Because of the large size of pine pollen grains (about 50 μm) and the short emission period of 5–8 days per year, the estimated potential annual inhalation doses are very low. Biological emissions including pollen release may be a source of increased airborne radionuclide concentrations at larger distances from the source areas as well. Received: 2 October 1998 / Accepted in revised form: 30 January 1999     

Correlation between meteorological conditions and Parietaria pollen concentration in Alassio,north-west Italy

The pollen grains in the atmosphere in different geographical areas differ according to the species present, the pollination seasons and pollen grain concentrations, but possibly the greatest contributors to this variability are the meteorological conditions. The aim of our research is to establish a possible correlation between Parietaria pollen concentration and meteorological conditions during the period from 1991 to 1995 in the town of Alassio (north–west Italy). As far as vegetation is concerned, the Mediterranean climatic conditions support the blooming of extensive grasslands in the environment surrounding the town; these grasslands mainly comprise Urticaceae and shrubs. The study demonstrates that the most influential parameters affecting the Urticaceae grain concentration upsurge are the absence of rainfall, a maximum daily temperature of about 21 °C, and a diurnal temperature range of about 5 °C. Moreover, our aeropalinological study indicates that this last parameter has the greatest influence on Urticaceae pollination. In fact, an increase in diurnal temperature range could be responsible for a dehydration of pollens resulting in a loss in mass. This grain lightness and volatility would ultimately permit atmospheric dispersion if there is a significant wind speed. On the other hand, days with rain or high relative humidity make pollens heavier, preventing them from flying long distances and therefore partially explaining the decline in airbone pollen concentration.     

Airborne grass pollen in Granada (Spain)

We have carried out a study on the annual and daily pollen concentrations from Gramineae over four consecutive years in the atmosphere of Granada (Spain). Samples of pollen grains were collected by the volumetric method with the aid of a Burkard sporetrap. Gramineae, according both to their high sensitizing capacity and to data from allergologists, are responsible for many pollinoses diagnosed in this area. In this work, daily pollen levels from April to July are monitored and the variations identified are interpreted in relation to meteorological conditions. Results indicated that the highest airborne concentrations of Gramineae pollen were found in May and June, although the beginning and intensity of pollination have been variable during these 4 years.     

Assessment between pollen seasons in areas with different urbanization level related to local vegetation sources and differences in allergen exposure

Pollen data recorded by a single sampler in any given city often fail to reflect particular events occurring in surrounding areas. This is frequently overlooked when interpreting aerobiological results, and therefore pollen data obtained in urban areas may not necessarily be representative of the situation in more rural areas of the same city. Our purpose is to assess differences between allergenic pollen concentrations recorded in an urban area (Eskulap) and a rural/suburban (Morasko) of the same city from 2005 to 2007. Anova-Manova Scheffe, Spearman correlation and Mixed-design ANOVA whitin-subjects effects tests were applied. The results obtained have showed longer pollen seasons, earlier starts of flowering and later conclusion in the urban area. The participation of arboreal pollen in the pollen fall of both sites had enough significative similarities to determine that is linked to regional conditions, while differences in the atmospheric pollen content of herbaceous plants between sites should be due to local conditions.     

Biometeorological characterization of the winter in north‐west Spain based on Alnus pollen flowering

The timing of pollen appearance in the atmosphere provides a general idea of the flowering onset of plants over a wide area. Woody plants in temperate regions have evolved mechanisms to preserve cells from the risk of frost during adverse weather conditions in the period prior to flowering regulated mainly by temperature. A number of indices have been developed to quantify the rest and heat requirements of temperature, which will enable the plant to adapt to environmental conditions. However, flowering is a dynamic and complex phenomenon and it is difficult to separate individual effects of different meteorological parameters. The use of modified bioclimatic indices could be a major step forward. In this study the Alnus glutinosa flowering in four different areas in north‐western Spain in the period 1995–2003 is examined, and trends identified by means of information gathered by Hirst pollen traps. Temperature plays an important role in the maturation of reproductive organs and pollen production. Comparison with bioclimatic indices showed that temperature during the 25–55 days preceding pollen release was the main controlling factor, and that relationship between flowering time and bioclimatic indicator values differs according to local conditions. In colder areas, rest and heat temperature requirements are greater because the trees need protection over a longer period; in the Mediterranean region of north‐western Spain, the rest temperature requirement and the threshold temperature are both higher than in Eurosiberian areas. Ombrothermic, Continentality and Thermicity indices are thus useful tools for characterizing the various bioclimatic areas of north‐western Spain.     

Estimating the beginning day of Japanese cedar pollen release under global climate change

This study examined the effects of snowfall on the beginning day of Cryptomeria japonica pollen release and predicted it under global climate change. We used a statistical method in order to investigate when the pollen release would start and how much sooner it would be, by using data on predicted meteorological conditions under global warming in Yamagata City, Japan. Estimation accuracy was improved by multiple regression by using the mean air temperature from January to February and snowfall depth in February. Adding snowfall depth yielded more accurate estimates of the beginning day of pollen release than using air temperature alone. It is possible that the effects of heat insulation and cooling by snow delay the flowering day. Under the predicted global climate change, we expect the beginning day of pollen release to become earlier in Yamagata City. The date would be 8 February in approximately 100 years, compared with 20 February at the earliest now. Eighty years from now the date could be earlier than any date recorded so far.     

The importance of interactions between meteorological conditions when interpreting their effect on the dispersal of pollen from homogeneously distributed sources

The interaction between different meteorological conditions recorded in Badajoz (SW Spain) over a 13-year period has been studied. The results were used for analysis of the effect of these conditions on atmospheric concentrations of Plantago and Brassicaceae pollen grain. For both types of pollen there was a positive effect of NE winds and a negative effect of SW winds which could not be explained by the location of the sources, because these species are very abundant all around the sampling station. The two effects were interpreted on the basis of the action of these winds on temperatures and relative humidity, because these conditions physically and biologically directly determine the concentrations of these types of pollen. Wind from the west is associated with an increase of wind speed and a decline in calm periods; wind from the south is associated with increased rainfall and humidity; wind from the opposite directions is associated with a decrease in these meteorological conditions. These main associations can explain the variation in pollen concentration, although there are also variations in seasons and years. These types of pollen also behave differently, so wind speed reduces the concentration of pollen from Plantago but increases it from Brassicaceae. Beyond the immediate application of the analysis to this specific case, there is a clear interest in observing the interaction between meteorological factors to gain a broader perspective for interpretation of the results of aerobiological studies aimed at determining the effect of these factors on the release and transport of particles into the air.     

Mesoscale Transport of Corylus Pollen Grains in Winter Atmosphere

Measurements of atmospheric pollen concentration were made at different sites of the Po Valley, Italy, during the winter of 1978. The concentration was determined with volumetric samplers both near the ground and at different heights up to 500 m. Only Corylus and Alnus pollen grains were found during the experimental period. Due to the large quantity of grains released and the detailed information available about the source areas, the Corylus pollen was used to investigate the features of atmospheric transport. It was found that the three-dimensional patterns of pollen concentration are strongly influenced by meteorological conditions. Moreover, it appears that pollen is present in the atmosphere for a longer time with respect to the emission period, due to the relevant effect of the resuspension of the deposited pollen grains. This effect is detectable at all the sampling points, and not only near the sources.