Abundant Pollen Types Research Articles

Comparison of pollen indoor/outdoor ratios during off-peak and peak periods in Japan

Outdoor pollen particles can invade indoor spaces through various pathways, causing hay fever. This study aimed to investigate the effect of pollen diameter and shape on indoor invasion ratio (indoor/outdoor [I/O] ratio) during off-peak and peak pollen periods as well as the pollen types that easily invade indoor spaces. The measurement site was located in an apartment in Tokyo, Japan. Daily pollen sampling was performed from November 2021 to May 2022. The I/O ratios were analyzed for six pollen diameter ranges (0–2.5 μm, 2.5−10 μm, 10−20 μm, 20−30 μm, 30−40 μm, and >40 μm), four pollen shapes (monomer, ruptured, agglomerate, and unknown pollen), and 14 pollen types. The results showed that the total I/O ratio per day during the peak pollen period (0−2.8) was larger than during the off-peak period (0−1.2). The highest I/O ratio values (mean: 0.68, median: 0.47) were observed for pollen >40 μm in diameter during the off-peak period. Regarding their shape, the highest I/O ratio values (mean: 0.70, median: 0.28) were observed for ruptured pollen during the peak period. The most abundant pollen types were Corynespora (off-peak period) and Japanese cedar (peak period) indoors.

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

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

Aeroallergens and Climate Change in Tulsa, Oklahoma: Long-Term Trends in the South Central United States.

Climate change is having a significant effect on many allergenic plants resulting in increased pollen production and shifts in plant phenology. Although these effects have been well-studied in some areas of the world, few studies have focused on long-term changes in allergenic pollen in the South Central United States. This study examined airborne pollen, temperature, and precipitation in Tulsa, Oklahoma over 25 to 34 years. Pollen was monitored with a Hirst-type spore trap on the roof of a building at the University of Tulsa and meteorology data were obtained from the National Weather Service. Changes in total pollen intensity were examined along with detailed analyses of the eight most abundant pollen types in the Tulsa atmosphere. In addition to pollen intensity, changes in pollen season start date, end date, peak date and season duration were also analyzed. Results show a trend to increasing temperatures with a significant increase in annual maximum temperature. There was a non-significant trend toward increasing total pollen and a significant increase in tree pollen over time. Several individual taxa showed significant increases in pollen intensity over the study period including spring Cupressaceae and Quercus pollen, while Ambrosia pollen showed a significant decrease. Data from the current study also indicated that the pollen season started earlier for spring pollinating trees and Poaceae. Significant correlations with preseason temperature may explain the earlier pollen season start dates along with a trend toward increasing March temperatures. More research is needed to understand the global impact of climate change on allergenic species, especially from other regions that have not been studied.

Pollen analysis of honeys from Apis mellifera and Tetragonisca fiebrigi (Hymenoptera: Apidae) in the Upper Paraná Atlantic Forest, Argentina

Abstract Nectariferous and polliniferous resources are key to the survival of social bees, so identifying the origin sources allows the implementation of management actions aimed at a greater supply of nutrients for the colonies. Besides, defining the floral origin of honeys contributes to their characterization and commercialization. The objective of our work was to identify the plants that provide nectar to the bees Apis mellifera and Tetragonisca fiebrigi in northern Misiones, through palynological analysis of honey samples collected between 2006 and 2008. Both bees showed a polylectic foraging habit. Richness of pollen types per sample ranged between 10 and 34 (mean = 20.5 ± 7.7) for A. mellifera, and between 13 and 43 (mean = 24.8 ± 7.1) for T. fiebrigi. The 15 most abundant pollen types in the honeys of A. mellifera were, in decreasing order of importance, Euphorbiaceae, Euterpe edulis, Holocalyx balansae, Calyptranthes concinna-type, Actinostemon, Salix, Ruprechtia laxiflora, Myrcianthes pungens-type, Thinouia mucronata, Allophylus edulis, Ilex, Syagrus romanzoffiana, Gouania latifolia-type, Parapiptadenia rigida, and Baccharis-type, whereas in the honeys of T. fiebrigi the most important pollen types included S. romanzoffiana, Schinus weinmannifolius-type, Baccharis-type, H. balansae, E. edulis, Rhamnaceae, Citrus, Leonurus japonicus, G. latifolia-type, A. edulis, Gomphrena perennis-type, Pouteria gardneriana, P. rigida, Zanthoxylum, and Actinostemon.

Aerobiological notes in the Biosphere Reserve “Sierras de Béjar y Francia” (MW Spain)

Aerobiological studies in urban areas are quite abundant in recent decades, but not in rural areas with a high environmental value. In this work, we analyze the airborne levels of pollen and fern spores in year 2012 collected by means of a volumetric sampler located in an ecological vineyard and in the Biosphere Reserve “Sierras de Bejar y Francia.” The results showed a high atmospheric representation of the natural vegetation of the environment, with almost half of the airborne pollen coming from the most represented tree formations such as chestnut and oak trees. Airborne concentrations of grass pollen reached approximately a 25% of the total, with high levels during 33 days of the year, 18 of them in January, February and March. The seasonal and intradaily behavior of the most abundant pollen types was focused on the months of May, June and July and the central hours of the day, respectively. Temperature had a positive influence on the levels of the main pollen types, while rainfall had a negative effect on pollen types from herbaceous species.

Effect of the Mediterranean crops in the airborne pollen spectrum

The impact of pollen grains as an allergenic factor is an important object of study. Various statistical analyses have been used to describe the behaviour of anemophilous plants, including certain Mediterranean cultivars (Olea europaea, Vitis vinifera, etc.). The main aims of this study are to define the pollen spectrum within an agricultural area and the effects of meteorological parameters and to examine whether Spearman’s correlation and ReDundancy Analysis (RDA) provide similar information. Aerobiological sampling was conducted using a Hirst-type volumetric spore trap from January 2015 to August 2018 in the Montilla mountains, in the south of the province of Cordoba, in an agricultural area close to a small city. In this location, the effect of ornamental plants is reduced and the cultivar effect becomes more important. Taking into account the average percentage for all years, the most abundant pollen types were Olea, Quercus, Poaceae, Urticaceae, Urtica membranacea, Vitis, Plantago, Pinus and Amaranthaceae. Due to the climatic characteristics of the study area, the meteorological parameters with most influence were temperature and dew point. The pollen spectrum in the study zone is caused by the agricultural use of the land, increasing the concentrations of some allergenic pollen types and decreasing the diversity of airborne pollen types. The RDA analysis gives a better explanation of the complex relationship between meteorological parameters and airborne pollen release and dispersion compared with the Spearman’s correlation.

Comprehensive analysis of different adhesives in aerobiological sampling using optical microscopy and high-throughput DNA sequencing

The standardization and unification of the procedures to analyze and quantify the airborne pollen concentrations are very important topics. In this work, the effectiveness of the two most used adhesives in aerobiological sampling, silicone prepared with cyclohexane solvent (Silicone) and petroleum jelly (Vaseline), was compared under outdoor conditions. This comparison was carried out using the traditional method based on the identification and quantification by optical microscopy (OM) of the airborne pollen and the novel methodology by high-throughput sequencing analysis (HTS). Globally, the results from both methods of analysis (OM and HTS) showed a good agreement between the two adhesives tested regarding the abundance of the main pollen types present in the samples: Cupressaceae, Olea, Poaceae, Platanus, Quercus. We concluded that the results from both adhesives are comparable data. Furthermore, the comparisons between methodologies, OM vs. HTS, showed that both techniques can accurately identify the most abundant pollen types in the atmosphere for the studied periods, with a good agreement of their relative abundances especially when the airborne pollen diversity is low but showing some divergences as the number of pollen types increases.

A 1000-year record of centennial-scale cyclical vegetation change from Maar Lake Sanjiaolongwan in northeastern China

To examine possible relationships between regional changes in vegetation and climate and fluctuations in solar activity, we obtained a high-resolution 1000-year pollen record from the Sanjiaolongwan Maar Lake (SJML) in northeastern China. An age model was established using analyses of 210Pb, 137Cs and AMS 14C. The pollen assemblages indicate that during the last millennium the vegetation of the study area was temperate coniferous and deciduous broadleaved mixed forest. Although Pinus is the most abundant pollen type in the record, various lines of evidence suggest that it is not especially temperature-sensitive. However, the analysis of the changes in pollen assemblages over the past 1000 years, and a comparison with pollen records from other lakes in the region, indicate that the Quercus frequencies can be used as a relatively sensitive temperature index for the study area. Several notable cold periods, with lower Quercus frequencies, occurred at approximately 1200 AD, 1410 AD, 1580 AD, 1770 AD and 1870 AD. These centennial-scale cold periods basically correspond to major minima in solar activity, suggesting that variations in solar activity may have been an important driver of climate and vegetation change in the study area during the last millennium.

Pollen in the atmosphere of Mexico City and its impact on the health of the pediatric population

Over a period of eight years, were assessed the main types of airborne pollen in Mexico City (a tropical region). We established the airborne pollen calendar and we evaluated the associations between aeroallergens and allergic diseases in children treated at hospitals. A Hirst-type volumetric spore trap was placed in an open area within the Chapultepec Forest, and pollen records were obtained during the flowering period of the plants. A total of 502 patients between 1 and 17 years old were evaluated. The patients were diagnosed by skin testing with extracts of tree pollen, grass and weeds. During the monitoring period, the airborne pollen grains were dominated by trees (Fraxinus, Cupressaceae, Alnus, Quercus) followed by Poaceae, with the highest average values detected between January and February. Children with positive reactions to pollen aeroallergens were diagnosed with allergic diseases. The predominant airborne allergens were determined. An airborne pollen calendar was established. A close association was found between the most frequent and abundant pollen types and the responses of children produced by exposure to pollen grains. Children with positive reactions to pollen were diagnosed with allergic conjunctivitis, allergic rhinitis, asthma and keratoconjunctivitis.

Aeropalynological study of two selected locations in North-Central Nigeria

Pollen and spores have been found as major biological sources of morbidity among individuals sensitive to respiratory disorders. The aim of the present study was to analyse the deposition rate of atmospheric pollen and fern spores at selected sites in Benue and Plateau states of the North-Central Nigeria between July 2015 and June 2016. This was accomplished by: (1) determining the pollen and fern spore content of each monitoring station; (2) establishing the relationship between total pollen count and meteorological parameters; and (3) comparing the recovered airborne pollen spectra with identified plants in the surrounding vegetation types of the sampling sites. The collection of atmospheric pollen was done using a modified Tauber sampler and plants in the surrounding environment of the sampling sites were enumerated. The residual solution was collected monthly and acetolysed, after which slide preparation and microscopy of the treated residue were done. Meteorological data were obtained from the Nigerian Meteorological Agency, Lagos. The results obtained reveal seasonal distribution patterns of various airborne pollen grains in the study locations. The most abundant pollen types recovered in Plateau State were produced by Syzygium guineense, Tridax procumbens, Alchornea sp., Terminalia sp., Poaceae and Amaranthaceae. Pollen types of Casuarina equisetifolia, Syzygium guineense, Tridax procumbens, Poaceae and Cyperaceae were preponderant in Benue State. Pteris sp., Nephrolepis sp. and a trilete fern spore were also represented in this study. The recovered airborne pollen spectra correspond favourably with some identified plants in the study locations. There was no significant correlation between monthly total pollen count and mean monthly values of meteorological parameters in Benue State. Air temperature and wind speed correlated significantly with monthly total pollen count in Plateau State. It is suggested that the allergenic effect of these abundant pollen types on humans should be further examined.

Variations in airborne pollen in central and south-western Spain in relation to the distribution of potential sources

The present study seeks to compare daily and hourly airborne pollen concentrations at eight different stations in Castilla-La Mancha (central Spain) and Extremadura (south-western Spain) and assess pollen distribution sources. Sampling stations were located 69–440 km apart in a straight line in Albacete, Toledo, Talavera de la Reina and Ciudad Real in Castilla-La Mancha, and in Badajoz, Plasencia, Santa Amalia and Zafra in Extremadura. Airborne pollen was collected using Hirst-type volumetric spore traps. Quercus was the most abundant pollen type at all stations except for Ciudad Real, where Olea pollen predominated. Comparisons of daily data between pairs of stations revealed statistically significant positive correlations in all cases for Poaceae and Olea. Comparisons of hourly data between stations indicated greater differences than daily data. Analysis of correlation coefficients and straight-line distances between stations revealed a strong negative correlation. Analysis of total airborne pollen data for the eight sampling stations suggests that airborne pollen concentrations decrease from west to east and from south to north, partly reflecting dominant wind patterns. A clear correlation was observed between airborne pollen concentrations and the surface area covered by olive crops in a 50 km radius around the sampling stations.

Diurnal variations of airborne pollen concentration and the effect of ambient temperature in three sites of Mexico City.

Pollen is an important cause of allergic respiratory ailments in the Mexico City Metropolitan Area (MCMA). However, very little is known if ambient air temperature correlates with the early blooming of plants observed in other urban areas around the world. A research study was conducted during the dry season of 2012-2013 at three representative sites of the MCMA with different urban characteristics with the aim to understand the relationships between the profusion and diversity of pollen against temperature and other meteorological variables and degree of urbanization. Pollen samples were collected using a Hirst-type trap sampler in the sites: Merced (highly urbanized), Iztapalapa (medium-high urbanized) and Coyoacan (moderately urbanized). Urbanization levels were determined using a composite index based on population density, proportion of surface covered by construction and asphalt, and urban heat island intensity. A set of representative pollen sampling tapes were assayed under a light microscope at magnification of ×1,000 and converted to grains per cubic meter. The most representative pollen types found in the three sites were, regardless of urbanization levels were: Fraxinus, Cupressaceae/Taxodiaceae, Casuarina, Alnus, Myrtaceae, and Pinus. Total pollen concentration was greatest in the moderately urbanized area, although earlier blooming took place at the highly urbanized zone. Total pollen concentration in the medium-high urbanized site has the lowest because the green areas in this zone of MCMA are few. In a diurnal basis, the most abundant pollen types peaked near midday or in the afternoon evening at the three sites. A Spearman test showed a positive correlation among bihourly pollen concentrations, temperature and relative humidity in all sites, but wind speed just correlated in Iztapalapa and Coyoacan. The results obtained suggest that Urban Heat Island Intensity can disturb flowering periods and pollen concentrations, largely in the highly urbanized areas. A principal components analysis established that the concentrations of each pollen type differed across the urbanization gradients. Additionally, it was found that a large number of allergenic pollens are produced by ornamental trees, some only recently introduced by urban planners.

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.

Morphological differentiation of Alnus (alder) pollen from western North America

Increasing the taxonomic resolution of fossil pollen identification is critical for advancing Quaternary paleoecology to a point where species-specific ecologies can be addressed in the fossil record. Here, we determine the critical morphological features that permit species-level differentiation of Alnus pollen, an abundant pollen type in Quaternary records from western North America. We examined over 21,000 pollen grains from the region's three common alder species: Alnus viridis subsp. sinuata Regel, Alnus incana subsp. tenuifolia Nuttall and Alnus rubra Bongard. Modern pollen samples were collected from 27 to 35 individual plants from across the range of each species. Nine morphological traits were measured on 30 pollen grains from each plant, and the number of pores was determined for an additional 200 pollen grains from each individual. Nested ANOVA analyses suggest that for individual Alnus plants, pollen morphology appears relatively stable, compared to variation between species. Statistically significant differences exist between the pollen of all three alder species in most morphological traits, but there is a high degree of within-species variability and between-species overlap in pollen morphology. Since no morphological trait on its own was sufficient for pollen identification to species, classification and regression tree (CART) analysis was used to derive multi-trait classification models. CART analyses show that A. rubra and A. viridis subsp. sinuata pollen can be differentiated into two distinct morphotypes, analogous to species separation, based on annulus width, arci strength, exine thickness and overall diameter. The intermediate pollen morphology of Alnus incana subsp. tenuifolia prevents identification of Alnus pollen to species when all three species are present in the pollen source area. This research lends support to paleoecological studies in western North America that have differentiated Alnus pollen into two morphotypes and revealed distinct postglacial histories that are masked when Alnus pollen are not differentiated.

Atmospheric pollen dynamics in Münster, north-western Germany: a three-year study (2004–2006)

An aeropalynological study was carried out in the atmosphere of Munster, the largest city in the region of North Rhine-Westphalia (north-western Germany), based on the data obtained during a 3 year of air-monitoring study (2004–2006) using a Hirst-type volumetric pollen trap. During the studied period, a total of 34 pollen types were identified in the atmosphere of the city, 20 corresponding to woody taxa and 14 to herbaceous taxa. The mean annual pollen index was 34,737, although there were important fluctuations from year to year. March to August was the period when more than 95% of the annual total was collected. The 10 most abundant pollen types detected were Betula, Urticaceae, Taxus/Cupressaceae, Quercus, Alnus, Poaceae, Pinus, Fraxinus, Platanus and Fagus, in order of abundance, which, together, accounted for 89.15% of the total pollen. To better observe the overall dynamics of the different pollen types in the atmosphere of Munster, a pollen calendar was drawn up. This showed typical features of North European pollen calendars: a winter period with very little pollen, short intense seasonal periods, and a high representation of pollen types from species characteristic of mixed Mid-European and riverside forests, such as Alnus, Betula, Corylus, Fagus, Picea, Pinus, Populus, Salix, Fraxinus and Carpinus.

Scanning electron microscope and light microscope study of selected palynomorphs from late Miocene sediments of Sofia Basin, Southwest Bulgaria

This article is focused on pollen morphology of some of the most abundant fossil pollen types from late Miocene sediments in Sofia Basin (Southwest Bulgaria). The investigation includes detailed morphological characteristic of the pollen types using observations under light and scanning electron microscope. Materials from the C-14 core near the village of Katina are the subject of this study. The age was determined as middle and upper Pontian on the basis of molluscs and mammals. Three pollen types from gymnosperm plants (Glyptostrobus type, Pinus diploxylon type and Tsuga canadensis type) and ten pollen types from angiosperm plants (Alnus sp., Betula sp., Carpinus sp., Corylus sp., Quercus robur type, Ulmus sp., Liquidambar sp., Juglans sp., Carya sp., Chenopodiaceae gen. ind.) have been described.

Pollen and Macrofossil Study of an Interglacial Deposit in Nova Scotia

Overburden removal for quarrying operations at the Milford Gypsum Quarry, East Milford, Nova Scotia, exposed 2 m of compacted and distorted peat and organic clays with abundant plant remains, associated with inorganic and laminated clays and sands. The non-glacial sediments were underlain by a grey till-like deposit and overlain by more than 20 m of red till. Wood (Larix sp.) from the nonglacial sediments produced a radiocarbon date of > 50,000 years BP (GSC-1642). Pollen analysis of the organic sediments shows a basal assemblage characterized by a variety of hardwood pollen genera including Fagus, Ulmus, Acer, Quercus and Tilia. Higher in the sequence Betula pollen increases and becomes the dominant pollen type. Towards the upper part of the organic unit, Picea and Abies balsamea replace the hardwood genera. Alnus is the most abundant pollen type at the top of the sequence. Wood, seeds, moss and Coleoptera remains add to the environmental reconstruction. The evidence as a whole leads to the conclusion that the latter part of an interglacial interval, probably the Sangamon, is represented. Hardwood forests dominated by a variety of thermophilous hardwood genera attest to a climate at least as warm as the present in the area. As the climate deteriorated, Betula became dominant. Continued cooling induced a transition to coniferous forests in which Picea and Abies balsamea predominated.

Airborne pollen sampling in a wildlife reserve in the south of Buenos Aires province, Argentina

The objective of this project was to study the pollen spectrum of the MarahueWildlife Reserve (Central Argentina), the quantity and quality of airborne pollen grains, and to evaluate the contribu- tion of outside sources, to protect a natural habitat with xerophytic shrub vegetation (''monte'') (the term ''monte'' is used for the dominant xerophytic shrub vegetation in the ''partido'' of Villarino) approximately 90 km south of Baho ´a Blanca. Sam- pling was performed weekly throughout a whole calendar year (January-December, 2003) using a volumetric impact sampler. Observations of flower- ing in the field were performed at the same time as the aerial sampling. Herbarium specimens were collected to make pollen collections of the species found in the study area, for reference purposes. The most abundant pollen types were Poaceae (31.3% total annual pollen), Amaranthus/Chenopodiaceae (25.3%), Eucalyptus (5%), Brassicaceae (3.9%), and Plantago (3.9%). This study showed the dispersion dynamics of pollen grains from characteristic species of the ''partido'' (the province of Buenos Aires is divided into partidos which are roughly equivalent to counties) of Villarino, the exotic flora of the surrounding area, and the pollen types from outside the region.

Airborne ragweed (Ambrosia artemisiifolia L.) pollen concentrations in Croatia, 2002–2004

The aim of this study was to determine the onset, length and end of the ragweed pollen season, taking into account diurnal, day-to-day, monthly and annual pollen variations, the effect of some meteorological parameters on atmospheric pollen concentrations and possible differences in the airborne pollen season and concentration due to sampling site. Airborne pollen was collected at three sites in central Croatia (Zagreb, Samobor and Ivanic Grad) during three pollen seasons (2002–2004). Seven-day Hirst-type volumetric pollen traps were used for pollen sampling. Ragweed pollen was the third most abundant pollen type to occur in the atmosphere of central Croatia. Total Ambrosia pollen concentration was the highest in the 2003 pollen season and the lowest in 2004 at all sampling sites. Maximum emissions were restricted to August and September. Intradiurnal periodicity showed a peak from 1000 to 1200 hours. The concentration of ragweed pollen during the pollen season was greatly influenced by temperature and precipitation: on rainy days accompanied by temperature decline, the air pollen concentration decreased abruptly. The results of this study are aimed at helping to alleviate the symptoms of allergic reactions in individuals with ragweed pollen hypersensitivity, thus improving their quality of life.

First volumetric airborne pollen sampling in Montevideo City, Uruguay

A volumetric aeropalynological sampling was carried out for the first time in MontevideoUruguay, from October 2000 to September 2001, using a Rotorod sampler Model 40. During the year 76 pollen types were identified. Airborne pollen was recorded over the year but a maximum pollen period was observed from August to April. For the rest of the months, pollen concentration was below 1% of the total annual pollen (TP). The pollen spectrum was characterized by the dominance of herbaceous pollen (NAP), which represented 68% of the TP and dominates the spectrum from November to March. Poaceae was the most frequent and abundant pollen type accounting for 45% of TP. The pollen spectrum reflected the floristic diversity of the city and most of the sources of airborne pollen are present in local and regional flora. Fourteen pollen types reach more than 1% of the TP and most of them are cited as allergenic pollen in other regions. These results may prove important for future medical research.