Meteorological factors affecting daily urticaceae pollen counts in southwest Spain

The influence of meteorological factors on daily Urticaceae pollen counts were studied in Córdoba (southwest Spain) in 1996 and 1997. The daily Urticaceae pollen concentrations were obtained by using a Hirst-type volumetric sampler, and meteorological data were obtained from the Córdoba airport, located near the sampling site. The highest correlation between pollen concentration and meteorological parameters was obtained during non-rainy seasons. Temperature was found to be the most important meteorological parameter influencing pollen counts in spring, as temperature is the main reason for the increase of pollen concentration in the atmosphere. In autumn, humidity was another important parameter influencing pollen counts. Rain, however, did not appear to be significant. The influence of the pollen concentration of the 2 previous days and the pollen concentration of the previous day has been studied. During periods with low precipitation, the pollen concentration of the previous day was a useful predictor of Urticaceae pollen concentrations for the following day. Received: 4 January 1999 / Revised: 26 July 1999 / Accepted: 6 September 1999     

Assessment of the daily ragweed pollen concentration with previous-day meteorological variables using regression and quantile regression analysis for Szeged,Hungary

Time-varying parametric linear and time-varying nonparametric regression models as well as a time-varying nonparametric median regression model are developed to predict the daily pollen concentration for Szeged in Hungary using previous-day meteorological parameters and the daily pollen concentration. The models are applied to rainy days and non-rainy days, respectively. The most important predictor is the previous-day pollen concentration level, and the only other predictor retained by a stepwise regression procedure is the daily mean global solar flux for rainy days and the daily mean temperature for non-rainy days. Although the variance percentage explained by these two predictors is higher for non-rainy (55.2%) days than for rainy (51.9%) days, the prediction rate is slightly better for rainy than for non-rainy days. Nonparametric regression yields substantially better estimates, especially for rainy days indicating a nonlinear relationship between the predictors and the pollen concentration. The explained variance percentage is 71.4 and 64.6% for rainy and non-rainy days, respectively. Concerning the mean absolute error, the nonparametric median regression provides the best estimate. The quantile regression shows that probability distribution of daily ragweed concentration is much more skewed for non-rainy days, while the more concentrated probability distribution for rainy days exhibits relatively stable ragweed pollen concentrations. The possible lowest limits of concentrations are also calculated. Under highly favorable conditions for peak concentrations, the pollen level reaches at least 350 grains m⁻³ and 450 grains m⁻³ for rainy and non-rainy days, respectively. These values again underline the excessive ragweed pollen load over the area of Szeged.     

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.     

Seasonal fluctuations of the airborne pollen spectrum in Murcia (SE Spain)

During six consecutive years (1993–1998), aBurkard volumetric pollen trap was continuouslyoperated to sample pollen from the air of thecity of Murcia. The aim of the study was toelucidate the spectra of airborne pollen andthe variations during the year, and toelaborate a pollen calendar. This time spanincludes the end of the period with severedrought from 1990–1995, which particularly affected the south-eastern region of Spain.The total sum of daily average pollenconcentrations amounted to 148,645 pollen grainsbelonging to 93 different taxa. A daily averageof 74 pollen grains/m³ and 11 taxa wererecorded, with maxima of 1157 and 27respectively. The total pollen amountregistered in a year correlated with yearlyrainfall, but there was no relation with meanannual temperature. As for annual fluctuations,there seemed to be no influence by totalrainfall or temperature. Spring and winter werethe seasons with the highest pollen counts andpollen diversity.From the 93 identified taxa, 36 are included inthe pollen calendar. Noteworthy findings are:(i) the presence of Thymelaeaceae,Robinia, Betula, Castanea,Zygophyllum, Caryophyllaceae andCannabis, (ii) a long pollen season ofChenopodiaceae/Amaranthaceae, Urticaceae,Poaceae, Arecaceae and Plantago, (iii)the occurrence of summer, autumn and winterflowering of Artemisia, (iv) the lateappearance of Corylus pollen, and (v) theminor presence of Casuarina pollen duringthe mid winter and late spring.     

Aprpaoches to airborne pollen in SE spain. First survey in murcia: one year of pollen monitoring (1993–94)

First data from a pollen survey carried out in the city of Murcia (SE Spain) are given in this paper. Using a Burkard Volumetric Spore Trap, daily slides were prepared and 80 pollen types belonging to 51 families andAlternaria spores were identified and counted. Special attention was paid to 14 relevant taxa: Cupressaceae,Pinus, Genisteae,Olea, Morus, Acer, Platanus, Plantago, Quercus, Urticaceae, Poaceae, Chenopodiaceae,Artemisia andAlternaria. The main sources of airborne particles wereAlternaria (27.7%), Cupressaceae (13.5%),Olea (9.36%), Chenopodiaceae (8.31%) and Urticaceae (5.8%). Annual variations in pollen abundance and length of the flowering seasons are given for individual species and are related to environmental factors. Results indicate a main pollen season from March to June and a second minor season in September to October. The relatively high concentrations of Genisteae and the appearance of anArtemisia winter season were noted.     

Aerobiological and clinical aspects ofParietaria officinalis in the area of Thessaloniki,Greece

Summary We collected the daily pollen samples during a 3-year period (Febr '87–Dec '89), using a Burkard volumetric trap, located on a high level area in the center of the city.Parietaria officinalis pollen was not differentiated under microscope from the other Urticaceae but through phenological criteria. The patients included in the detection of the sensitivity toP. officinalis pollen came from the Out-patient Clinic of Bronchial Asthma of the General Hospital «G. Papanikolaou». They had a seasonal pollinosis and they were submitted to Pricktest using a battery of 22 groups and aP. officinalis pollen extract. The Urticaceae pollen appears first in the atmosphere of Thessaloniki in the end of March, shows a peak in the beginning of May and continues to be present till the end of August. We detectedP. officinalis pollen sensitivity combined with other allergens in 24.1% of the patients and in 1.4% a monosensitivity toP. officinalis.     

Precision of the daily pollen count. Identifying sources of variation using variance component models

Summary During the pollen season, a daily account of airborne pollen is reported by radio and newpapers in Denmark as «Today's pollen count». The Aerobiological Group under the Danish Asthma and Allergy association is responsible for the daily identification and counting of pollen. In 1984 the Group set up a trial to investigate the reproducibility of the pollen count.Three trained pollen counters independently examined the same specimens from two Burkard pollen traps. The traps were located on the roof of the Meterological Institute in Copenhagen 15 meters above ground level in the northern outskirts of central Copenhagen. This is the usual sampling site. Specimens from each trap from 20 days during the grass pollen season were selected. Four species groups were identified in sufficient numbers for statistical analysis. These were, in order of occurrence, spruce/pine (Picea/Pinus), grass (Poaceae), nettle (Urtica) and mugwort (Artemisia).Identification of sources of variation and assessment of their relative importance were carried out using variance components models. A detailed account of the method is given.Qualitatively equivalent conclusions were reached for each group: i) The expected seasonal variation was identified; ii) The counters contributed significantly to the variation of pollen counts; iii) The traps did not contribute to the variance, but a day-trap interaction was identified. This interaction was interpreted. as a problem of instrumental variation over time of traps of variation in meteorological conditions; iv) The total variance was larger than originally expected. The relative uncertainty was greater than 50 per cent.The variance of the daily pollen count cannot be reduced much by reducing counter variation or day-trap interaction. The variation among pollen counters is small, and the day-trap interaction is difficult to fully comprehend. The basic measurement error can be reduced by examining a larger area of each specimen. Although this implies a greater cost, it is probably the most effective method of reducing the uncertainty of «Today's pollen count».     

Risk of pollen allergy in Nerja (southern Spain): a pollen calendar

An aeropalynological study was carried out in the atmosphere of the city of Nerja (southern Spain) during a period of 4 years (2000–2003), using a Hirst type volumetric pollen trap. An annual pollen index of 59,750 grains, on average, was obtained with 80–85% of the total pollen recorded from February to May, with Pinus, Olea, Urticaceae, Cupressaceae, Quercus and Poaceae being the principal pollen producers in abundance order. A total of 29 pollen types that reached a 10-day mean equal to or greater than 1 grain of pollen per m³ of air is reflected in a pollen calendar. The results were compared with those obtained for nearby localities and a correlation analysis was made between the daily fluctuations of the main pollen types and total pollen, and meteorological parameters (temperature, rainfall and hours of sun). The daily, monthly and annual values reached by the most important pollen types from an allergenic point of view (Olea, Urticaceae and Poaceae) confirms Nerja as a high-risk locality for the residents and the numerous tourists who visit the area.     

A long-term study of winter and early spring tree pollen in the Tulsa, Oklahoma atmosphere

Since 1986 the atmosphere in Tulsa, Oklahoma has been monitored for airborne pollen and spores with a Burkard 7-day spore trap situated on the roof of a building at The University of Tulsa. The present study specifically examined the early spring tree pollen season for several local taxa and the occurrence of pre-season pollen during December and January. Knowledge of the local pollen season will help identify the presence of out-of-season pollen and possible long distance transport (LDT) events. Average daily concentrations of airborne pollen for species ofBetula, Quercus, Ulmus, and Cupressaceae were determined for each year from 1987 to 1996. The data showed that during the early spring the precise pollination periods for these allergenic tree species are highly variable. There were considerable variations in start date, season length, peak concentration, date of peak, and cumulative season total. The start dates forUlmus, Betula, andQuercus varied by 30 days or more, while the early spring Cupressaceae pollen showed the least variation in start date (only 23 days). More research is needed to understand the mechanisms which govern the onset and magnitude of pollen release. Although several reports have documented episodes of long distance transport (LDT) of pollen, the actual contribution of out-of-season or out-of-region pollen to local air spora is poorly known. The current study also re-examined the LDT ofJuniperus ashei pollen in Oklahoma.Juniperus pollen appeared in the Tulsa atmosphere on 40% of the days in December and January with concentrations as high as 2400 pollen grains/m³ of air; however, no local populations ofJuniperus pollinate at this time of the year. High concentrations occurred on days with southerly winds suggesting thatJuniperus ashei populations in southern Oklahoma and Texas were the pollen source. Since no local pollen is present in the Tulsa atmosphere in December and January, this example of LDT has been easy to document.     

Annual,daily and diurnal variations of Urticaceae airborne pollen in Málaga (Spain)

In the Mediterranean area, Urticaceae pollen, together with the pollen of olive and grasses, are the aeroallergens with the highest incidence in the population. From October 1991 to September 1993, with the aid of a Burkard spore-trap, we carried out a study on the Urticaceae pollen content in the atmosphere of Málaga, a seaside resort situated in the Costa del Sol (southern Spain). In Málaga, the Urticaceae pollen season is very long and their pollen grains are detected throughout the year. However, peaks were recorded in March and April and the variables most influencing concentration were maximum air temperature, sunshine hours and relative humidity. Diurnal patterns show that peaks occur generally from 10:00 h to 16:00 h when the temperature reaches its highest values.     

Annual,daily and dirunal variations of Urticaceae airborne pollen in Málaga (Spain)

In the Mediterranean area, Urticaceae pollen, together with the pollen of olive and grasses, are the aeroallergens with the highest incidence in the population. From October 1991 to September 1993, with the aid of a Burkard spore-trap, we carried out a study on the Urticaceae pollen content in the atmosphere of Málaga, a seaside resort situated in the Costa del Sol (southern Spain). In Málaga, the Urticaceae pollen season is very long and their pollen grains are detected throughout the year. However, peaks were recorded in March and April and the variables most influencing concentration were maximum air temperature, sunshine hours and relative humidity. Diurnal patterns show that peaks occur generally from 10:00 h to 16:00 h when the temperature reaches its highest values.     

A new weather factor predicting airborne pollen concentration: Péczely’s macrosynoptic weather types

In the present study determinative factors for ragweed (Ambrosia elatior) pollination were studied in Budapest between 1991 and 1996. The aim was to create a model to predict the day-to-day pollen count variation. The pollen concentration is determined mostly by the potential concentration and the mean concentration of the three previous days. These two variables can explain 56% of the total variance. Daily mean and maximum temperature, daily temperature fluctuation and the number of hours of sunshine in the previous day have a significant positive effect on the pollen count. The amount of precipitation on the previous day, relative humidity on the actual and on the previous day influence it negatively. When a cyclone prevails, pollen concentration is usually lower than the seasonal average. Some anticyclonal situations have a similar effect, while other anticyclonal types promote pollination. A predictive model was then created by multiple regression using the potential concentration, the mean concentration of the three previous days, the daily temperature fluctuation and the synoptic type as independent variables. This model can explain more than 68% of the total variance, and its accuracy is >71%. The model seems to predict accurately the trends during the pollen seasons, thus it will probably be a good tool in the practical prediction in Budapest, and the methodology will hopefully be applicable to other sites of the Carpathian Basin too.     

Intradiurnal fluctuation of pollen in La Plata, Argentina. Part I, herbaceous pollen types

A pollen analysis was carried out on six herbaceous pollen types whose annual concentration represents a percentage higher than 0.3% in the atmosphere of the city of La Plata, Argentina, from July 1998 to June 2001. They are: Ambrosia, Cyperaceae, Chenopodiaceae-Amaranthaceae, Plantago, Poaceae and Urticaceae. Hourly patterns of the pollen types analysed with the intradiurnal daily index (IDI) could be grouped into three categories account the percentage that represent of pollen concentration registered during five hourly periods of the day. Group I includes pollen types that show a sharp peak in abundance gust one at hour of the day. Group II is formed by pollen types that show high concentrations in more than one hourly band during the daylight. Group III is characterized by the pollen types that show lower concentrations over a broad hourly band during the day.     

<Emphasis Type="Italic">Betula</Emphasis> pollen: One of the most important aeroallergens in Ourense,Spain. Aerobiological studies from 1993 to 2000

This study presents the results obtained for airborne Betula pollen between 1992 and 2000 in Ourense, Spain, sampled by volumetric spore-trap (LANZONI VPPS2000). Annual and year-on-year variations were analyzed, and a statistical study of the correlation between daily counts and several meteorological parameters was performed. Birch pollen is present in the atmosphere during March and April in Ourense. Significant differences were observed among the different years. Values obtained for the correlation coefficient between Betula pollen counts and the various meteorological parameters studied indicate, for Ourense, a positive correlation between pollen count and both temperature and sunlight. A negative correlation was recorded for relative humidity. Temperature is thus the determining factor for flowering onset and intensity. Regression equations included values for the days prior to pollen concentration measurement in order to optimize results.     

Annual pollen spectrum variations in the air of Bratislava (Slovakia): years 2002–2009

Pollen grains in the atmosphere of Bratislava were quantitatively and qualitatively analysed during an 8-year period (2002–2009) using a Burkard volumetric pollen trap. The mean annual total pollen grain count recorded during this period was 36,608, belonging to 34 higher plant taxa (22 trees and/or shrubs and 12 herbaceous species). The maximum annual total pollen grain count (50,563) was recorded in 2003 and the minimum (14,172) in 2009. The taxa contributing the highest concentration of pollen grains were Betula, Urticaceae, Cupressaceae-Taxaceae, Populus, Pinus, Poaceae and Ambrosia. During the study period, there was a remarkable increase in the number of pollen grains from February to April, with the highest daily mean pollen counts recorded in April. Total pollen concentration began to decrease markedly in May, but there was a second increase between July and August, followed by a decrease in September. The timing and length of the pollen seasons varied. Betula and Poaceae showed a rather constant 2-year fluctuating rhythm. The relationships between airborne pollen concentration and meteorological variables were assessed. Based on these results, the first pollen calendar in Slovakia has been constructed for the area of Bratislava, which provides a great deal of useful and important information.     

Trends in atmospheric concentrations of weed pollen in the context of recent climate warming in Poznań (Western Poland)

A significant increase in summer temperatures has been observed for the period 1996–2011 in Poznań, Poland. The phenological response of four weed taxa, widely represented by anemophilous species (Artemisia spp., Rumex spp. and Poaceae and Urticaceae species) to this recent climate warming has been analysed in Poznań by examining the variations in the course of airborne pollen seasons. Pollen data were collected by 7-day Hirst-type volumetric trap. Trends in pollen seasons were determined using Mann–Kendall test and Sen’s slope estimator, whereas the relationships between meteorological and aerobiological data were established by Spearman’s rank correlation coefficient. Significant trends in pollen data were detected. The duration of pollen seasons of all analysed taxa increased (from +2.0 days/year for Urticaceae to +3.8 days/year for Rumex), which can be attributed to a delay in pollen season end dates rather than earlier start dates. In addition, the intensity of Artemisia pollen seasons significantly decreased and correlates with mean July–September daily minimum temperatures (r?=??0.644, p?Rumex pollen seasons. The results of this study show that observed shifts in weed pollen seasons in Poznań, i.e. longer duration and later end dates, might be caused by the recorded increase in summer temperature. This influence was the strongest in relation to Artemisia, which is the taxon that flowers latest in the year. The general lack of significant correlations between Rumex and Urticaceae pollen seasons and spring and/or summer temperature suggests that other factors, e.g. land use practices, could also be partially responsible for the observed shifts in pollen seasons.     

Study of the pollen emissions of Urticaceae, Plantaginaceae and Poaceae at five sites in western Spain

A comparative study is presented of the pollen emissions of Urticaceae, Plantaginaceae and Poaceae, collected during 1995 with Hirst samplers (Burkard or Lanzoni) at five sites in western Spain: two Mediterranean sites located in the south (Huelva and Seville) and three Atlantic sites in the north (Orense, Vigo and Santiago). The annual pollen of Poaceae and Plantaginaceae collected in the Atlantic cities was found to be twice that in the Mediterranean sites, and the total amount of Urticaceae was higher at sites with an urban environment and subject to sea influence (Vigo, Huelva and Seville). At all the sites, the start of the main pollination periods (MPP) took place in the following order: Urticaceae, Plantaginaceae and Poaceae. It was also observed that the MPP of these three pollen types began earlier in Huelva and Seville, where the mean temperatures necessary for the beginning of pollen emissions are recorded very early. Regarding the variation in pollen concentrations throughout the year, Urticaceae presented peaks of maximum concentration in March (Huelva, Seville, Vigo and Orense) and June (Santiago); Plantaginaceae in March (south) and June (north); and Poaceae in May (south) and June–July (north). At northern sites, pollen emissions of Urticaceae and Plantaginaceae continued throughout the summer, while in the south they decreased considerably from May onwards. From the allergenic point of view, the indices of reactivity described for Urticaceae and Poaceae were exceeded more often at northern sites, in particular at Vigo. The meteorological conditions associated with periods of highest pollen emission of these three herbaceous types are a rise in mean temperature, light or absent rainfall, and abundant sunshine. The statistical correlations between pollen emissions and meteorological factors were not well-defined, either for the stations or for all the taxa, although they were clearer for the Atlantic cities and for Urticaceae.     

Gramineae hay fever,and aerobiological and clinical investigation in Palermo; Sicily

Summary Epidemiological and aerobiological observations (1987;1989) have been carried out for three years in order to search the existing relationship between the Gramineae's daily pollen concentration in Palermo's atmosphere and the number of hay fever cases due to such pollen.The aerobiological data were obtained with a 2000 VPPS volumetric sampler. Clinical research was performed on 555 hay fever patients treated in our ambulatory over a three-year period (1987–1989).These data, elaborated by a seven day running mean method and correlated with epidemiological data, evidenced that three of the pollen families in our territory are clinically important: Urticaceae,Parietaria prevailing among them, Gramineae and Oleaceae,Olea europaea prevailing among them.The Gramineae are the second most important allergenic pollen (32,08% of all the pollinosis) whereas, as far as its concentration in the atmosphere is concerned; it ranks third followingParietaria and Oleaceae.     

Comparison between categorical pollen data obtained by Hirst and Cour sampling methods

Two methods of aerobiological collection, the Burkard(Hirst-based) and the Cour, were compared using datafrom pollen collected at Bellaterra (Barcelona, Spain)between 1994 and 1996. Results for three pollen taxaof allergenic relevance (Urticaceae, Poaceae andOlea) are presented. This study confirmed thedifficulty of finding a reliable conversion formulabetween these sampling methods, as has been found byseveral other authors.An alternative statistical analysis was carried outusing categorical data, the pollen concentration databeing first converted into an ordinal scale with fivelevels based on local records. Our analysis shows thatboth methods provide essentially the sameinformation.     

Twenty years of aerobiological monitoring in Trentino (Italy): assessment and evaluation of airborne pollen variability

The aim of the study is to report a reliable airborne pollen spectrum composition and seasonal timings for the monitored area as a basis for allergy management and to ascertain possible modifications through the detection of trends during the 20-year time series (1989–2008). Pollen was collected at San Michele all’Adige (Trento, Italy) by means of a Hirst-type spore trap. Sampling and counting of airborne pollen grains were carried out according to a national standard. Pollen concentration data for the period were processed in order to characterize the main pollen seasons for a subset of taxa, selected on the basis of their allergenicity and local representativeness. Variations in the pollen data over the years surveyed were analyzed using non-parametric tests. The results showed the presence of 63 pollen taxa, 40 of which belonged to tree and shrub species and 23 to herbaceous species. The local pollen spectrum was characterized by the presence of highly allergenic taxa, such as Urticaceae, Graminaceae, Ostrya sp., and Cupressaceae, in terms of percentage contribution as well as mean daily pollen count or peak values over the years surveyed. A significant upward trend was observed for daily mean pollen amount, mainly due to pollen from woody species and probably ascribable to a temperature-driven increase in pollen production. Evaluation of the results presented will form the basis of further research focussed on the climate change-related causes of modifications to vegetational dynamics as well as on the phenology of flowering and on pollen production.