Airborne pollen flora of Jabalur – the central India

The fortnightly aerobiological survey of pollengrains at five different sites at two differentheights (ground level and at 10 m) was carriedout at Jabalpur city during January toDecember, 1996. Air sampling was done for 30minutes at each sampling point by using aRotorod air sampler. A total of 84 pollen typesbelonging to 34 families of Angiospermae andone family of Gymnospermae were identified. Themaximum mean concentration (1.04/m³ air) ofpollen was contributed by Asteraceae followedby Amaranthaceae/Chenopodiaceae (0.77/m³ air)and the minimum (0.001/m³ air) byCucurbitaceae, Convolvulaceae and Sapotaceae.Maximum numbers of pollen grains werecontributed by herb species (62.07%) followedby shrubs (18.47%) and trees (14.96%). Asmall fraction, i.e., 4.50% of total pollenflora remained unidentified. Morphologicalanalysis revealed maximum concentration(1.81/m³) of triporate pollen grains. There wasa significant difference in the pollenconcentration at ground level and at 10 mheight. The ratio observed was 1.7 : 1.0.There was non-significant negative correlation(r = –0.196) between mean pollen concentrationand mean atmospheric temperature. May, thehottest month, showed minimum mean pollenconcentration (1.65/m³ air), whereas October,with moderate temperature, the maximum(10.86/m³ air).     

The partial contribution of specific airborne pollen to pollen induced allergy

The air that we inhale contains simultaneously a multiple array of allergenic pollen. It is well known that such allergens cause allergic reactions in some 15 of the population of the Western World. However little is known about the quantitative aspect of this phenomenon. What is the lowest concentration of pollen that might trigger allergic responses? As people are exposed to heterogeneous and variable environments, clarification of the partial contribution of each of the major airborne pollen allergens and determination of its role in invoking allergy are of prime importance. Objectives: (1) Assessment of a possible correlation between the concentration of airborne pollen and incidence of allergy. (2) Estimation of the lowest average concentrations for various species of airborne pollen that elicit allergic symptoms when exceeded. (3) Determination of the extent of the variations in manifestation of allergy symptoms that can be explained by fluctuations in the concentration of individual species of airborne pollen. Methods: The study was conducted during 14?months with a rural population in Israel. The participants completed a detailed questionnaire and were skin prick tested with the common airborne allergens. The appearance of clinical symptoms, i.e. nasal, bronchial, ocular or dermal, were reported daily by the patients. Concentrations of the airborne pollen and spores were monitored in the center of activity of the residents during one day every week, using three ‘Rotorod’ pollen traps. The pollen grains were identified by light microscopy. Results: The pollen spectrum was divided into time-blocks presenting the main pollination periods of the investigated species. The correlation between the concentration of airborne pollen of the relevant species and the clinical symptoms of the patients was determined for each time block. The correlation differed for different clinical symptoms and for different pollen allergens. Highest correlation with airborne pollen counts was found for patients with nasal and bronchial symptoms. The onset of the clinical symptoms by sensitive patients started, in each of the relevant groups, once the weekly average concentration of the airborne pollen crossed a threshold level. Under the limitations of the present study, this level was estimated to be 2–4 pollen m^?3 air for olive, 3–5 pollen m^?3 air for grasses, 4–5 pollen m^?3 air for Artemisia, 10–20 pollen m^?3 air for pecan and 50–60 pollen m^?3 air for cypress. Conclusions: Fluctuations in specific airborne pollen grains explained up to 2/3 of the variation in clinical allergy responses. Those were: 69 of the variation for cypress (March–April), 66 for the grasses (March–April), 49 for the pecan (May–June) and 62 for Artemisia (Autumn).     

The partial contribution of specific airborne pollen to pollen induced allergy

The air that we inhale contains simultaneously a multiple array of allergenic pollen. It is well known that such allergens cause allergic reactions in some 15 of the population of the Western World. However little is known about the quantitative aspect of this phenomenon. What is the lowest concentration of pollen that might trigger allergic responses? As people are exposed to heterogeneous and variable environments, clarification of the partial contribution of each of the major airborne pollen allergens and determination of its role in invoking allergy are of prime importance. Objectives: (1) Assessment of a possible correlation between the concentration of airborne pollen and incidence of allergy. (2) Estimation of the lowest average concentrations for various species of airborne pollen that elicit allergic symptoms when exceeded. (3) Determination of the extent of the variations in manifestation of allergy symptoms that can be explained by fluctuations in the concentration of individual species of airborne pollen. Methods: The study was conducted during 14months with a rural population in Israel. The participants completed a detailed questionnaire and were skin prick tested with the common airborne allergens. The appearance of clinical symptoms, i.e. nasal, bronchial, ocular or dermal, were reported daily by the patients. Concentrations of the airborne pollen and spores were monitored in the center of activity of the residents during one day every week, using three Rotorod pollen traps. The pollen grains were identified by light microscopy. Results: The pollen spectrum was divided into time-blocks presenting the main pollination periods of the investigated species. The correlation between the concentration of airborne pollen of the relevant species and the clinical symptoms of the patients was determined for each time block. The correlation differed for different clinical symptoms and for different pollen allergens. Highest correlation with airborne pollen counts was found for patients with nasal and bronchial symptoms. The onset of the clinical symptoms by sensitive patients started, in each of the relevant groups, once the weekly average concentration of the airborne pollen crossed a threshold level. Under the limitations of the present study, this level was estimated to be 2–4 pollen m^–3 air for olive, 3–5 pollen m^–3 air for grasses, 4–5 pollen m^–3 air for Artemisia, 10–20 pollen m^–3 air for pecan and 50–60 pollen m^–3 air for cypress. Conclusions: Fluctuations in specific airborne pollen grains explained up to 2/3 of the variation in clinical allergy responses. Those were: 69 of the variation for cypress (March–April), 66 for the grasses (March–April), 49 for the pecan (May–June) and 62 for Artemisia (Autumn).     

Ragweed (Ambrosia) pollen presence in Livorno,Central Italy: Aerobiological and sensitization data

We have studied Ragweed pollen concentration in the atmosphere of Leghorn (Livorno). where Ragweed is not widespread. Our data, from 1991 to 1995, confirm the presence of Ragweed pollen in the atmosphere of Leghorn in low concentrations (highest value of 11 pollen grains/m³) from August to the end of September. Even if the sensitization level in our area is 6.76%, the clinical significance of Ragweed pollinosis is still very low.     

Ragweed (Ambrosia) pollen presence in Livorno,Central Italy: Aerobiological and sensitization data

We have studied Ragweed pollen concentration in the atmosphere of Leghorn (Livorno), where Ragweed is not widespread. Our data, from 1991 to 1995, confirm the presence of Ragweed pollen in the atmosphere of Leghorn in low concentrations (highest value of 11 pollen grains/m³) from August to the end of September. Even if the sensitization level in our area is 6.76%, the clinical significance of Ragweed pollinosis is still very low.     

Using meteorologic data to predict daily ragweed pollen levels

Pollen-related allergy is a common disease resulting in symptoms of hay fever and asthma. Control of symptoms depends (generally) on avoidance and pharmacological treatment. Both of these approaches could benefit from accurate predictions of pollen levels for future days. We have constructed a model that uses meteorological data to predict ragweed pollen levels based on air samples collected daily in Kalamazoo, MI from 1991 to 1994. Ragweed pollen counts were converted to pollen grains/m³ of air (24-h average). We used Poisson regression, which appropriately handles the heterogenous variance associated with pollen data. Using standard statistical model selection procedures, combined with biological considerations, we selected rainfall, wind speed, temperature, and the time measured from the start of the season as the most significant variables. Using our model, we propose a method that uses the weather forecast for the following day to predict the ragweed pollen level. This approach differs from most previous attempts because it uses Poisson regression and because this model needs to be fit iteratively each day. By updating the coefficients of the model based on the information to date, this method allows the fundamental shape of the pollen distribution curve to change from year to year. Application to the Kalamazoo data suggests that the method has good sensitivity and specificity for predicting high pollen days.     

Pollen and Mould Allergy in Southern Sardinia (Italy): Comparison of Skin-Test Frequencies and Air Sampling Data

A study was carried out to investigate the influence of atmospheric pollen and fungi in determining allergic diseases by comparing the frequency of skin reactions to air sampling data over a 6-year period.

48% of our population reacted to at least one of the pollen and fungal extracts used. Among pollen, Gramineae gave the most frequent positive reactions, followed by Parietaria, Olea and Compositae. The most common positive skin tests in fungus sensitive patients were by extracts of Alternaria, Cladosporium, Aspergillus and Candida

As for the aerobiological survey, the general trend of pollen and molds was similar during the sampling period. The annual pollen catch did not show remarkable differences during the years sampled, whereas the total fungal spore count was highest in 1988 and 1990.

A comparison between aerobiological and clinical data revealed a good degree of concordance between total pollen counts and positive skin test frequencies for Urticaceae, Gramineae and Oleaceae but not for Compositae (high positive skin reactions and very low counts) and Cupressaceae (high counts and few skin reactions).

A less marked correlation has been found between fungal spore counts and positive skin-test frequencies as compared to pollen. Spores such as Cladosporium, which are present in large number in the air, appear to be less sensitizing, while certain spore types (e.g. Alternaria), seem to be able to sensitize patients in spite of their low atmospheric concentrations.     

Ragweed and mugwort pollen in Szczecin, Poland

Ragweed (genus Ambrosia) and mugwort (Artemisia vulgaris) pollen grains are known to be very potent aeroallergens, often noted to enter into cross reactions. The aim of the study was to analyse ragweed and mugwort pollen release in Szczecin (western Poland) during the period 2000–2003. Measurements were performed by the volumetric and gravimetric method. Pollen seasons were defined as the periods of 90% of the total catch. Of the 4 years studied, the lowest concentration of ragweed pollen was observed in 2000. In 2000, the annual ragweed pollen count was very high, threefold higher than in 2001. There was a high Ambrosia pollen count in 2003, with the highest daily value of 84 grains/m³. The mugwort pollen season started in the third 10-day period of July and lasted to the end of August in all of the years studied. Analysis of pollen deposition from different Szczecin city’s districts showed that the highest exposure to ragweed pollen allergens occurred in the Majowe district, which is related to the presence of numerous plants of Ambrosia in that district. The mugwort pollen deposition was more abundant in the Żelechowa district, which is an area with villas and gardens. Statistically significant correlations were found between the ragweed pollen count in the air and the maximum wind speed, air temperature and relative humidity and between the mugwort pollen count in the air and air temperature and relative humidity.     

Environmental analysis of airborne pollen occurrence,pollen source distribution and phenology of <Emphasis Type="Italic">Fraxinus angustifolia</Emphasis>

Narrow-leafed ash (Fraxinus angustifolia) is a common polygamous tree growing on the banks of rivers in the western Mediterranean region. Pollination occurs during winter, and the tree’s pollen is among the most abundant during that season. This work aims to relate the phenology of pollen shedding, source tree distribution, meteorology and airborne pollen occurrence for the species. Aerobiological sampling was conducted in Badajoz (south-western Spain) using a Hirst volumetric sampler over 24 years (1993–2016). Trees were geo-localized in a circle 500 m in diameter surrounding the pollen sampler. During the last two periods, pollination phenology was studied in 10 specimens, five in the surroundings of the pollen station and five 3 km apart, at a frequency of 3–4 days on average. Moreover, a detailed analysis of pollen occurrence was conducted for these two periods. Daily data for the whole period and hourly data over the last 2 years were used, including pollen monitoring and meteorology. A comparison was made between pollen occurrence and source distribution. The main pollen season lasted on average 53 (28–75) days. Average values were less than 10 grains m^?3, except for two periods of 23–24 grains m^?3. Daily data and hourly data correlation with meteorology showed different signs in correlation analysis. Hourly analysis showed that the maximum concentration occurred just after noon. Most pollen was recorded at an average temperature of 9 °C. Analysis of pollen sources and pollen occurrence showed a close relationship between predominant wind directions and tree distribution. Peaks of phenology were not coincident with pollen peaks. No trends in pollination were found. Non-homogeneous distribution of pollen sources for Fraxinus angustifolia provided a suitable tool to demonstrate that wind direction plays a relevant role when aerobiological data are interpreted according to source distribution. A limitation in phenology analysis and aerobiological data was noted in the narrow-leafed ash species.     

The relationships between the concentrations of airborne pollen and allergic symptoms in Trieste (Northern Italy) in 1989

Summary Concentrations of airborne pollens recorded in Trieste in 1989 are evaluated in relation to allergic complaints in 113 patients with skin prick tests positive to one pollen species. Analysis of the result enable the two most important allergens to be confirmed as: Poaceae in 70.7% of patients and Parietaria in 18.6%. Few people had monosensitation to Compositae (Artemisia), Corylaceae and Fagaceae.Sympotoms are related to the flowering period when pollen levels climbed to daily averages of 15–20 grains/m³ but they started later than airborne peak concentrations and finished later than pollen decline. Pollen concentration recording can be a useful way to predict the clinical manifestation in sensitive patients but other factors are involved in determining symptoms like subjective mucosal reactions, polysensitization, patients living and working environment.     

Intrusion of airborne pollen through open windows and doors

The importance of the transport of pollen by air movement into houses was evaluated using six to eight simultaneously collecting rotorod-type samplers, creating either a sampler line from outdoors to inside the room, or a sampler grid inside a room. The number of incoming pollen grains was highly dependent on the outdoor concentration. The highest concentrations inside (1–2 m distance) and outside (1 m) the room were 600 and 3,250 grains/m³, respectively, in the Betula pollen season and 1,980 and 5,080 grains/m³ in the Pinus season. The pollen concentration and the indoor/outdoor (I/O) ratio decreased as the distance from the ventilation opening increased. Inside the room at a distance of 1–2 m 28%, and at a distance of 3–5 m 12%, of the outside concentration was recorded. In the lower part of the opening the mean proportion was 63% and in the upper part of the opening it was 40%. Efficient ventilation with two open windows increased the I/O ratio and enabled the pollen to spread throughout the room. During the Pinus pollen season 3–35% of the outdoor concentration was simultaneously recorded at six locations inside the room with two open windows and only 0.1–3.6% with one open window. At the same point in the room the I/O ratio varied from <1 to 35%, depending on the sampling conditions. Only a minor effect on the I/O ratio was found between small and large ventilation windows and the door, although it was expected that more air and pollen grains would come indoors through a larger opening.     

Airborne pollen concentration in Seville (Spain), 1993–1996. First results obtained with Hirst’s method

The data presented constitute the longest historical series of results obtained in Seville with a Hirst-type sampler, and are a further contribution to earlier aerobiological studies carried out in the city with a Cour trap. This work supplies an updated pollen calendar of the city, together with pollen counts and other aerobiological parameters for the 14 most important types in the 4-year period of sampling. These werePlatanus hispanica, Olea europaea, Quercus, Cupressaceae, Poaceae, Urticaceae, Moraceae, Chenopodiaceae/ Amaranthaceae,Plantago, Pinaceae,Rumex, Myrtaceae, Compositae, andCasuarina.     

Threshold values of grass pollen (Poaceae) concentrations and increase in emergency department visits,hospital admissions,drug consumption and allergic symptoms in patients with allergic rhinitis: a systematic review

Airborne grass (Poaceae) pollen measurements are used in public warning systems to inform people about the risk of allergic symptoms. However, there is no consensus about which exact thresholds of pollen concentrations provoke the allergic symptoms. The aim of this study was to review the relevant scientific information on the relationship between grass pollen concentrations and the occurrence of emergency department (ED) visits, hospital admissions (HA), drug consumption and allergic symptoms. Literature search was conducted by experts’ consultation and snowball strategy. Studies meeting the criteria for inclusion were assessed regarding their risk of bias (RoB). A high RoB resulted in exclusion of the study from data synthesis. Extensive data were extracted and qualitatively compared. The review is registered in PROSPERO. 32 Studies were eligible while 18 showed a low RoB and were qualitatively synthesised. Emergency department visits and hospital admissions were mostly investigated. Threshold values of 10 grains/m³ and 12 grains/m³ were reported for ED visits and HA. Evidence exists that an increase of 10 grains/m³ of air leads to a significant increase in adverse health outcomes. Especially at a three-day lag, adverse health effects were shown. Variations in exposure and outcome measurement make the definition of pollen thresholds difficult. As a consequence, no defined pollen threshold values could be identified. Studies with uniform exposure measures and statistical methods are necessary to gain a better understanding of the impact of grass pollen on human health. Determining personal thresholds could be beneficial for affected people.

     

Comparison between Urticaceae (Parietaria) pollen count and hay fever symptoms: assessment of a «threshold-value»

Summary A comparison betweenParietaria pollen count and allergic symptoms of rhino-conjunctivitis in the early season was used in utilized to determine a «threshold-value» for this pollen. Clinical data were obtained from diary-cards of 34 allergic patients and pollen data from a volumetric sampling, carried out by means of a Hirst-Burkard pollen-trap. A significant correlation (r=0.98) was found between pollen count and symptom scores. Mild symptoms were registered with concentrations above 10–15 pollens/m³. Severe symptoms occurred when pollen count exceeded 80/m³/24 h., and over 90% of patients recorded symptoms. The importance of the late reactions and of the total allergenic airborne content are emphasized.     

Parietaria pollen a new aeroallergen in the city of Valparaiso, Chile

Parietaria pollen has never been considered as a significant cause of pollinosis in Chile; therefore, the sensitization to Parietaria study has never been included in the study of patients with clinical suspicion of pollinosis in this region. The objective of this study was to describe the clinical characteristics of pollinosis caused by Parietaria in the Valparaíso region, related to air concentrations of this kind of pollen. A cross-sectional study was performed in the city of Valparaíso. It consisted of two stages: In the first, pollen grains were counted between 1999 and 2001. In the second, a sensitization profile on a patient population diagnosed with ARC (allergic rhinoconjunctivitis) was evaluated. Parietaria judaica (P. judiaca) presented pollination all year long, with aggravation in the spring and summer, and with values reaching 80 grains/m³ (weekly average). These findings determined the transience of the symptoms in this population, which is mainly perennial with seasonal aggravations. A total of 72 atopic subjects were obtained during the whole sample recollection period. P. judaica was the second most frequent cause of sensitization (60 %) after Dermatophagoides in the sample overall. Also, in monosensitized subjects, it was the first cause of pollen sensitization. P. judaica represents the second cause of allergy in Valparaíso and the first cause of pollinosis. These findings suggest the importance of quantifying Parietaria in Valparaíso and near cities, plus investigating the presence of sensitization and symptoms to allergies in a significant proportion of patients in this region.     

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.     

Predicting the grass pollen count from meteorological data with regard to estimating the severity of hayfever symptoms in Melbourne (Australia)

In Melbourne, Australia, grass pollen is the predominant cause of hayfever in late spring and summer. The grass pollen season has been monitored in Melbourne, using a Burkard spore trap, for 13 years (1975–1981, 1985 and 1991–1997). Total counts for grass pollen were highly variable from one season to the next (approximately 1000 to >8000 grains/m³). The daily grass pollen counts also showed a high variability (0 to approximately 400 grains/m³). In this study, the grass pollen counts of the 13 years (12 grass pollen seasons, extending from October to January) have been compared with meteorological data in order to identify the conditions that can determine the daily amounts of grass pollen in the air. It was found that the seasonal total of grass pollen was directly correlated with the rainfall sum of the preceding 12 months (1 September–31 August): seasonal total of grass pollen (counts/m³)=18.161 × rainfall sum of the preceding 12 months (mm) −8541.5 (r _s=0.74,P<0.005,n=12). The daily amounts of grass pollen in the air were positively correlated with the corresponding daily average ambient temperatures (P<0.001). The daily amount of grass pollen which was to be expected with a certain daily average temperature was linked to the seasonal total of grass pollen: in years with high total grass pollen counts, a lower daily average temperature was required for a high daily pollen count than in years with low total grass pollen counts. As the concentration of airborne grass pollen determines the severity of hayfever in sensitive patients, an estimation of daily grass pollen counts can provide an indication of potential pollinosis symptoms. We compared daily grass pollen counts with the reported symptomatic responses of hayfever sufferers in November 1985 and found that hayfever symptoms were significantly correlated to the grass pollen counts (P<0.001 for nasal,P<0.005 for eye symptoms). Thus, a combination of meteorological information (i.e. rainfall and temperature) allows for an estimation of the potential daily pollinosis symptoms during the grass pollen season. Here we propose a symptom estimation chart, allowing a quick prediction of eye and nasal symptoms that are likely to occur as a result of variations in meteorological conditions, thus enabling both physicians and patients to take appropriate avoidance measures or therapy.     

Airborne pollen, spores, and dust across the East Mediterranean Sea

Airborne pollen and spores, as well as airflow directions, were continuously monitored during a cruise across the East Mediterranean from Tel Aviv, Israel, to Istanbul, Turkey. In spite of the fact that a high-altitude dust cloud moved, at that, time from North Africa, across the East Mediterranean, only a few dust particles were monitored on the boat. The numbers of counted airborne pollen along the cruise path were rather small. This is, in part, because the trip was taken after the main flowering season in the East Mediterranean region. Nevertheless, airborne pollen grains were still found, either as a result of remnant pollen releases by late-flowering plants or because of secondary lift-up of previously settled pollen. The presented pollen counts are average pollen counts /m³ air /6 h. The counts ranged between ∼5 pollen/m³ of air in mid-sea (July 16th–July 17th) or ∼6 pollen/m³ of air on the Israeli coast (July 16–July 17th), and 30 pollen/m³ of air near the coasts of Turkey and of the Greek Islands (July 18th–July 19th) and some 18 taxa of pollen were identified, most of them at the family level. Some 30 taxa of different spores were recorded. The numbers of airborne spores were relatively low in mid-sea (300–750 spores/m³ air), but were high near the coasts of Turkey (1,200–2,400 spores/m³ air) and of Israel (340–1,695 spores/m³ air).     

Pinus pollen in the atmosphere of Vigo and its relationship to meteorological factors

The Pinus genus has an elevated pollen production and an anemophilous nature. Although considered to be hypoallergenic, numerous cases of allergies caused by Pinus pollen have been cited and different authors believe that its allergenicity should be studied in more depth. In the city of Vigo several patients have tested positive for Pinus pollen extracts in skin tests, some of them being mono-sensitive to such pollens. In order to ascertain the behaviour of Pinus pollen and its correlation to the main meteorological factors, we carried out an aerobiological study in the city of Vigo from 1995 to 1998 by using a Hirst active-impact volumetric sporetrap, model Lanzoni VPPS 2000, placed on the left bank of the Vigo estuary (42°14’15’’N, 8°43’30’’W). Pinus has high quantitative importance in the airborne pollen spectrum of the city. It is one of the best represented taxa constituting 13%–20% of the total annual pollen levels. The quantity of Pinus pollen present in the atmosphere of the city of Vigo throughout a year is 5751 grains (as the average for the sampled years), with a very long pollination period, from the middle of January until May. The maximum concentration was recorded in 1998 with 1105 grains/m³ on 3 March, a much greater value than those for the previous years. At the end of its pollination period there is usually a final increase in Pinus pollen concentrations coinciding with the pollination of Pinus silvestris, which are more abundant in mountainous areas far from the city. Received: 17 March 1999 / Revised: 20 December 1999 / Accepted: 20 December 1999     

Indoor and outdoor pollen concentrations in private and public spaces during the <Emphasis Type="Italic">Betula</Emphasis> pollen season

Although the number of studies of pollen concentrations inside and outside buildings is increasing, little is known about the efficiency of penetration of pollen from outdoor to indoor air, and further. We studied indoor and outdoor pollen concentrations in the town of Lappeenranta and in the municipality of Rautjärvi in SE Finland from May 3–23, 2004, i.e. throughout the Betula pollen season, and assessed the risk of exposure to pollen grains. Pollen concentrations were measured inside and outside a block of flats, a detached house, and the regional central hospital, using rotorod-type samplers; in the town of Joutseno data were compared with Burkard counts. Outdoor concentrations of Betula pollen grains ranged between low and abundant (0–855 grains m^?3). The corresponding indoor concentrations near the main front doors varied from low to moderate (0–17 grains m^?3) in the central hospital and were low (<10 grains m^?3) in both residential buildings. Indoor concentrations further from the main front door were low (<10 grains m^?3) at all study sites. The concentrations of Betula pollen decreased substantially from outdoors to indoors, and further toward the centre of the building, probably indicating relatively poor penetrating properties of the pollen grains and/or the short-lived presence of pollen grains in indoor air. The concentrations of Betula pollen inside the buildings during the peak flowering period were mostly at a level barely inducing reactions even in the most sensitive persons.