An annual study of airborne pollen in northern Mexico City

An investigation of airborne pollen in northern Mexico City was carried out for one year. A total of 24 taxa were identified and classified according to the growing form in pollen of trees, weeds and grasses. Pollen grains were recorded all year round with a peak in December. The trees group showed the highest quantity of pollen as well as taxa diversity, although its peak period was in the dry season. The weeds and grasses emitted a larger quantity of pollen in the rainy season. The dominant taxa wereAlnus, Casuarina, Compositae and Gramineae. As for their relation with meteorological parameters, we found that the increase of pollen concentration was related to high temperatures, low relative humidity and high wind speed, the latter causing an increase of airborne pollen with no dilution at all. The hours with the highest pollen concentration where from 16:00 to 18:00.     

An annual study of airborne pollen in northern Mexico City

An investigation of airborne pollen in northern Mexico City was carried out for one year. A total of 24 taxa were identified and classified according to the growing form in pollen of trees, weeds and grasses. Pollen grains were recorded all year round with a peak in December. The trees group showed the highest quantity of pollen as well as taxa diversity, although its peak period was in the dry season. The weeds and grasses emitted a larger quantity of pollen in the rainy season. The dominant taxa wereAlnus, Casuarina, Compositae and Gramineae. As for their relation with meteorological parameters, we found that the increase of pollen concentration was related to high temperatures, low relative humidity and high wind speed, the latter causing an increase of airborne pollen with no dilution at all. The hours with the highest pollen concentration where from 16:00 to 18:00.     

Poaceae pollen in the atmosphere of Aranjuez,Madrid and Toledo (central Spain)

The main aim of this work is to study the aerobiological behaviour of Poaceae pollen in three areas of central Spain (Aranjuez, Madrid and Toledo), all of which are similar from a geographical, climatic and biogeographical point of view, and they are located nearby one another. The samplings were carried out over a period of 4 years (2005–2008) using Hirst-type spore traps. Grass pollen is responsible for most spring allergic reactions in the pollen-sensitive population in central Spain, and they are very abundant in the atmosphere of this part of Iberian Peninsula. The average amount of this pollen type, as a percentage of the annual total pollen amount, is 7.4% in Aranjuez, 9.2% in Madrid and 11.3% in Toledo. Poaceae pollen is present in the atmosphere over a long period of time (February–October), and its maximum concentrations are detected during May and June (weeks 16–25). The city of Toledo has the highest annual concentrations of grass pollen (average 5,797 grains) with a great number of days exceeding the allergy thresholds proposed by the Spanish Aerobiology Network (REA). Madrid and Aranjuez present similar annual concentrations of grass pollen with values of 2,961 grains and 2,751 grains, respectively. The correlation analysis between the daily levels of grass pollen and meteorological variables of temperature and rainfall show a significant correlation, positive with temperature (maximum, mean and minimum) and negative with rainfall.     

A 10-year survey of allergenic airborne pollen in the city of Porto (Portugal)

Airborne pollen calendars are useful to estimate the flowering season of the different plants as well as to indicate the allergenic potential present in the atmosphere at a given time. In this study, it is presented a 10-year survey of the atmospheric concentration of allergenic pollen types. Airborne pollen was performed, from 2003 to 2012, using a 7-day Hirst-type volumetric trap. The interannual variation of the daily mean concentration of the number of pollen grains and the main pollen season was determined as well as the hourly variations and correlation with meteorological parameters. During the study period, 18 different allergenic pollen types were considered based on its representativeness on the total annual airborne pollen concentration. The lowest annual concentrations were sampled in 2006 and the highest in 2007. The highest airborne pollen concentration was found during early spring and early summer. On the contrary, December was the month with the lowest pollen concentration. The major pollen sampled belongs to trees followed by weeds and grasses, being the most representative pollen types in the atmosphere: Urticaceae, Platanus, Poaceae, Pinaceae, Cupressaceae, Acer, Quercus, Castanea, Plantago, Alnus, Olea europaea, Betula, Myrtaceae and Populus. Intradiurnal distribution patterns of the pollen types studied presented differences with some taxa being predominantly sampled in the morning (9–11 a.m.) while others in first night hours (between 9 and 12 p.m.). Significantly correlations were found between the airborne pollen concentration and meteorological parameters.     

Fifteen years' record of airborne allergenic pollen and meteorological parameters in Thessaloniki,Greece

A pollen calendar has been constructed for the area of Thessaloniki and relationships between pollen transport and meteorological parameters have been assessed. Daily airborne pollen records were collected over a 15-year period (1987-2001), using a Burkard continuous volumetric pollen trap, located in the centre of the city. Sixteen allergenic pollen types were identified. Simultaneously, daily records of five main meteorological parameters (mean air temperature, relative humidity, rainfall, sunshine, wind speed) were made, and then correlated with fluctuations of the airborne pollen concentrations. For the first time in Greece, a pollen calendar has been constructed for 16 pollen types, from which it appears that 24.9% of the total pollen recorded belong to Cupressaceae, 20.8% to Quercus spp., 13.6% to Urticaceae, 9.1% to Oleaceae, 8.9% to Pinaceae, 6.3% to Poaceae, 5.4% to Platanaceae, 3.0% to Corylus spp., 2.5% to Chenopodiaceae and 1.4% to Populus spp. The percentages of Betula spp., Asteraceae (Artemisia spp. and Ambrosia spp.), Salix spp., Ulmaceae and Alnus spp. were each lower than 1%. A positive correlation between pollen transport and both mean temperature and sunshine was observed, whereas usually no correlation was found between pollen and relative humidity or rainfall. Finally, wind speed was generally found to have a significant positive correlation with the concentrations of 8 pollen types. For the first time in the area of Thessaloniki, and more generally in Greece, 15-year allergenic pollen records have been collected and meteorological parameters have been recorded. The airborne pollen concentration is strongly influenced by mean air temperature and sunshine duration. The highest concentrations of pollen grains are observed during spring (May).     

Trends and threshold exceedances analysis of airborne pollen concentrations in Metropolitan Santiago Chile

Pollen is one of the primary causes of allergic rhinoconjunctivitis in urban centers. In the present study, the concentrations of 39 different pollens in the Santiago de Chile metropolitan area over the period 2009–2013 are characterized. The pollen was monitored daily using Burkard volumetric equipment. The contribution of each type of pollen and the corresponding time trends are evaluated. The concentrations of the pollens are compared with the established threshold levels for the protection of human health. The results show that the total amount of pollen grains originating from trees, grasses, weeds and indeterminate sources throughout the period of the study was 258,496 grains m-3, with an annual average of 51,699 ± 3,906 grains m-3 year-1. The primary source of pollen is Platanus orientalis, which produces 61.8% of the analyzed pollen. Grass pollen is the third primary component of the analyzed pollen, with a contribution of 5.82%. Among the weeds, the presence of Urticacea (3.74%) is remarkable. The pollination pattern of the trees is monophasic, and the grasses have a biphasic pattern. The trends indicate that the total pollen and tree pollen do not present a time trend that is statistically significant throughout the period of the study, whereas the grass pollen and weed pollen concentrations in the environment present a statistically significant decreasing trend. The cause of this decrease is unclear. The pollen load has doubled over the past decade. When the observed concentrations of the pollens were compared with the corresponding threshold levels, the results indicated that over the period of the study, the pollen concentrations were at moderate, high and very high levels for an average of 293 days per year. Systematic counts of the pollen grains are an essential method for diagnosing and treating patients with pollinosis and for developing forestation and urban planning strategies.     

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.     

Spatial and temporal variations of pollen concentrations in Islamabad (Pakistan): effect of meteorological parameters and impact on human health

This study focuses on the identification and quantification of airborne pollen grains from allergenic plant species and their relationship with meteorological factors, i.e. maximum and minimum daily temperature, relative humidity, rainfall and wind speed in the city of Islamabad, Pakistan. An aerobiological data set (2010–2012), collected using rotorod samplers in five different sectors of the city, was supplied by the Pakistan Meteorological Department. Pollen of eight allergenic species was identified amongst which Broussonetia papyrifera exceeded the highest pollen level and, therefore, likely played a key role in aggravating the symptoms of pollen allergy in the city. The mean weekly pollen counts were next correlated with the weekly number of allergic patients visiting hospitals during 2010–2011. Clinical data were acquired from the Pakistan Institute of Medical Sciences. The highest number of allergic patients visiting hospital was usually observed during weeks with high pollen level. These results suggest a close relationship between the pollen concentration in the air and the allergy symptoms. Spearman’s rank correlation analysis was performed to establish the relationships between meteorological parameters and daily average pollen counts. A pollen calendar for the Islamabad city was also prepared to provide a guide for the timing and duration of season for all encountered pollen types.     

Exploring the spatio-temporal relationship between two key aeroallergens and meteorological variables in the United Kingdom

Constructing accurate predictive models for grass and birch pollen in the air, the two most important aeroallergens, for areas with variable climate conditions such as the United Kingdom, require better understanding of the relationships between pollen count in the air and meteorological variables. Variations in daily birch and grass pollen counts and their relationship with daily meteorological variables were investigated for nine pollen monitoring sites for the period 2000–2010 in the United Kingdom. An active pollen count sampling method was employed at each of the monitoring stations to sample pollen from the atmosphere. The mechanism of this method is based on the volumetric spore traps of Hirst design (Hirst in Ann Appl Biol 39(2):257–265, 1952). The pollen season (start date, finish date) for grass and birch were determined using a first derivative method. Meteorological variables such as daily rainfall; maximum, minimum and average temperatures; cumulative sum of Sunshine duration; wind speed; and relative humidity were related to the grass and birch pollen counts for the pre-peak, post peak and the entire pollen season. The meteorological variables were correlated with the pollen count data for the following temporal supports: same-day, 1-day prior, 1-day mean prior, 3-day mean prior, 7-day mean prior. The direction of influence (positive/negative) of meteorological variables on pollen count varied for birch and grass, and also varied when the pollen season was treated as a whole season, or was segmented into the pre-peak and post-peak seasons. Maximum temperature, sunshine duration and rainfall were the most important variables influencing the count of grass pollen in the atmosphere. Both maximum temperature (pre-peak) and sunshine produced a strong positive correlation, and rain produced a strong negative correlation with grass pollen count in the air. Similarly, average temperature, wind speed and rainfall were the most important variables influencing the count of birch pollen in the air. Both wind speed and rain produced a negative correlation with birch pollen count in the air and average temperature produced a positive correlation.     

Pollen emission from olive trees and concentrations of airborne pollen in an urban area of North Sardinia

In this study the seasonal and daily variations in olive airborne pollen concentrations were measured in the atmosphere of Sassari (Italy) and the olive pollen emission was monitored in the countryside during the flowering period in 1995 and 1996, in order to detect the patterns of change in the atmosphere. The intensity and the timing of pollination was also studied in relation to phenological stages occurrence. In addition, the influence of the main meteorological parameters on pollen emission and airborne pollen dispersal in the city was assessed. Airborne pollen reached its highest concentration a few days before the peak of pollen emission in 1995 but several days after it in 1996 (6 days). Analysis of hourly concentrations shows that the maximum emission and dispersion recorded during the observation period occurred in the middle of the day. Significant regressions were found between hourly temperature and air humidity values and hourly pollen concentrations recorded in the olive grove for almost every day studied, indicating a negative correlation between humidity and pollen concentration and a positive correlation between pollen concentration and temperature. On the other hand, no significant correlation was observed between the meteorological parameters and pollen concentration recorded in the urban area.     

Spring airborne pollen data in two sites in Trentino (Northern Italy): a comparison with meteorological data

In this paper airborne pollen concentration is compared to meteorological data of Trento and S. Michele all’Adige, two sites in the Adige Valley, in Trentino (North Italy). Pollen ofCorylus, Alnus, Betula andOstrya, four winter-spring flowering plants are considered. Pollen sampling was carried out in 1996 by volumetric Hirst-type samplers. For all pollen types considered, maximum pollen concentration coincided in both stations and there was a good overlap of the main pollen season length; the pollen curves of S. Michele a/A and Trento showed a highly positive correlation. The daily airborne pollen concentrations, defined as the number of pollen grains per cubic meter of air (P/m³), were compared to daily meteorological data: minimum and maximum air temperature (°C), average relative humidity (%), precipitation (mm), global incident radiation (cal/cm²), average wind direction (°) and wind speed (m/s). A highly positive correlation was found forCorylus and maximum temperature in both monitoring stations.Betula was positively, whereasOstrya was negatively correlated to relative humidity. With this first analytical approach sharp differences in the atmospheric pollen presence between the stations located at Trento and S. Michele all’Adige were not found.     

Aerobiology of Urticaceae pollen in Trieste (NE Italy)

The aerobiological behaviour of Urticaceae in Trieste and the correlations with the meteorological parameters were examined. Airborne pollen was collected from 1990 to 1999 using a Hirst type spore trap (Burkard) and the data interpretation was performed according to the standard method adopted by the Italian Aeroallergen Network. The main pollen season of Urticaceae in Trieste goes from mid-April to mid-September. The highest values occur in May and June. Although different seasonal patterns are found every year, the main peak occurs on average at the beginning of May, followed by other decreasing peaks until September. Thecumulative counts vary greatly over the years, with a mean value of 18.315 p/m³. The maximum annual total pollen grains was registered in 1996 and the minimum in 1991. Spearman's correlation was used to establish the relationship between the daily pollen counts and the daily meteorological data both considering their original quantitative values and transformed values according to their day by day changes. Daily pollen concentrations present usually positive correlation with temperature, negative with rainfall and wind speed and no correlation with humidity. Better results were obtained with transformed values.     

Allergenic airborne pollen monitoring of Vigo (NW Spain) in 1995–2001

Pollen data from the atmosphere of Vigo, NW Spain was collected using a Hirst type pollen trap over a seven-year period (1995–2001). A total of 56 different pollen types were identified, among which Urticaceae, Poaceae, Betula and Quercus represent the greatest risk for people suffering from allergic rhinitis (hay fever) or other allergic diseases. Although in the atmosphere of Vigo the presence of allergenic pollen is constant throughout the year, the months of March and April account for 40% of the annual total pollen count. Two main risk periods have been identified for asthma and allergies: (1) March – April, and (2) June – July, the latter is of greater importance due to high concentrations of Poaceae pollen. Correlation analysis with meteorological parameters demonstrates that rainfall, relative humidity, maximum temperature, sun hours and north-easterly winds are the main factors influencing the average daily pollen concentrations in the atmosphere.     

Pollen spectrum in Northern Tunis,Tunisia

This study has been focused on airborne pollen concentration in Northern Tunis. Pollen has been detected by a volumetric Hirst-type spore trap. This suction sampler was placed for two hydrologic years in the area of Mornag, northeastof Tunisia (36°40N; 10°17E). Fifty-two taxa were identified with heterogeneous daily pollen concentrations and a dominance of anemophilous plants. The main pollen types detected in the atmosphere were Olea europaea (38.7 and 20.75%), Cupressus (33.57 and 55.4%), Urticaceae (9.22 and 12.24%), Poaceae (3.55 and 3.32%), Mercurialis annua (2.96 and 1.6%) and Amaranthaceae (2.49 and 1.55%). The monthly pollen spectrum indicated a seasonal periodicity of airborne pollen with the main pollen season during spring. Two pollen seasons have been observed during these hydrologic years, due to both Cupressus and Amaranthaceae airborne pollen is represented during winter or spring, and also during autumn and late summer, respectively. Other pollen types represent a long pollen season, i.e., Urticaceae, starting in autumn and following until late spring. Daily pollen concentration showed a different behavior during the flowering season between both years, observing differences related to pollen index. Correlation between daily pollen concentrations of the dominant taxa showed a positive and significant correlation between airborne pollen concentrations of spring-pollinated taxa and mean temperature, but negative with maximum temperature, humidity and rainfall. In the case of minimum temperature, a different response, positive for trees and negative for herbaceous plants, has been observed.     

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.     

Aerobiological study of Fagaceae pollen in the middle-west of Spain

The concentration of airborne Fagaceae pollen in Salamanca and the correlations with some meteorological parameters have been examined. Castanea and Quercus pollen grains were collected from 1998 to 2004 using a Burkard spore trap. No pollen grains of Fagus were found. The main pollen season took place in April and May for Quercus and in June and July for Castanea. Yearly variations on these dates could be related to the influence of meteorological factors such as rainfall, temperature, or dominant winds. The highest values appeared in the year 2004 for both taxa. The Fagaceae airborne content was mainly due to Quercus pollen, Castanea having a scarce pollen content in the city of Salamanca. The highest counts of Fagaceae pollen grains were found from mid May to early June due to the pollen behavior of oaks. The cumulative counts varied over the years, with a mean value of 2,384 pollen grains, a highest total of 6,036 in 2004 and a lowest total of 954 in 2001. No cyclic variations were observed. Daily pollen concentrations presented positive correlation with temperature, negative with relative humidity and slightly negative with rainfall using Spearman's correlation coefficients, only in the case of Castanea, because the particular hourly distribution of rainfall during the spring might affect Quercus airborne pollen.     

Dynamics and behaviour of airborne Quercus pollen in central Iberian Peninsula

Quercus pollen is one of the most abundant pollen types in the atmosphere of central Iberian Peninsula (Spain), as a consequence of the extensive representation of well-preserved forests and shrub communities dominated by species of the genus Quercus in this area. This paper analysed key features of the Quercus pollination season in the central Iberian Peninsula and the influence of weather-related variables on airborne Quercus pollen concentration through statistical techniques of correlation analysis and the use of a decision tree model for predicting pollen concentrations. Quercus species are very common in Spain and Portugal, dominating a number of ecosystems including Mediterranean forests. This gives rise to very high airborne Quercus pollen concentrations, particularly in spring. Sampling was carried out over a 6-year period using a Hirst volumetric sampler, and the sampling procedure established by the Spanish Aerobiology Network. Results show that between 92 and 98.5 % of total annual airborne Quercus pollen was recorded in the April–June period. Annual pollen index were high in all study years, averaging 12,344 grains, but it should be highlighted that pollen production was highly variable between years. Correlations between mean daily Quercus pollen concentration and weather-related variables showed that in the pre-peak period, a significant positive correlation was observed with the mean daily temperature and the hours of sunshine and a negative correlation was observed with the humidity and the rainfall. In the post-peak period, a significant negative correlation was found with the mean daily temperature and the hours of sunshine. The predictions obtained in the decision tree model showed a moderate significant correlation (r = 0.42) with the daily Quercus pollen concentration predicted and the one observed. Temperature is the most influential variable in the release of Quercus pollen.     

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.     

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.     

Pollen production,microsporangium dehiscence and pollen flow in Himalayan cedar (Cedrus deodara Roxb. ex d. Don)

Microsporangium dehiscence, pollen production and dispersal were studied in Himalayan cedar (Cedrus deodara) during 1998 and 1999. Microsporangium dehiscence showed diurnal periodicity and was found to be related to air temperature and relative air humidity, with a strobilus taking 2 d to dehisce completely in warmer conditions and 3 d in cooler ones. The frequency of flowering in C. deodara was highly variable during the two successive years; however, cyclical production of pollen grains was observed in 50% of the trees. The maximum concentration of pollen grains in the air was found between 1200 and 1600 h, and this period was also noted to be the best time for pollination. Studying migration of pollen grains from isolated single trees in three directions showed that migration was not uniform in all directions. Long-distance transport of pollen grains was observed in the downhill direction. However, in the uphill and horizontal directions grains could travel only up to 97.5 and l95.1 m, respectively, and the frequency of pollen grains to the source frequency at these distances was only 1.9 and 2-5%, respectively. The results suggest that an isolation barrier of 190 m may be considered as a minimum for the management of deodar seed orchards.