CLADOSPORIUM SPORES IN THE AIR OF SZCZECIN

Moulds are common aeroallergens and Cladosporium is considered to be the most prevalent of them. The objective of the studies was to determine the seasonal variation in concentrations of Cladosporium spores due to meteorological parameters. The meteorological parameters analysed were maximum air temperature, relative humidity, amount of precipitation and wind speed. The greatest threat from Cladosporium allergens was posed from the middle of May (2004, 2006) and June (2005) till the middle of October (2005) and in the end of October (2004) till the middle of November (2006). Statistically significant correlations were found among the Cladosporium spore count in the air and maximum air temperature in all the analysed seasons, and amount of precipitation only in one season. The spore count of Cladosporium was determined by weather conditions, especially by air temperature.


INTRODUCTION
Cladosporium spores are reported to form a majority of airborne spores in the temperate zones (D a v i e s 1969, S o l o m o n 1978). Cladosporium species live as saprophytes or as parasites on many kinds of plants. Dry spores produced in excessive quantities can be transported over wide areas, even oceans. Recordings from all parts of the world show that with a few exceptions Cladosporium is the most frequently encountered mould in the air. Its temperature optimum ranges 18-28º C, but growth down to -6º is also possible (G r a v e s e n , 1979).
There is a great seasonal variation in the concentration of Cladosporium conidia in the air; the highest concentrations occur during the summer from June Generally, conidial production and dispersal in Cladosporium depend on precipitation, temperature, and the amount of available growth medium. High atmospheric spore concentrations can develop only when dead plant material, e.g decidous trees, freshly cut branches or twigs, are present as a medium (K u r k el a , 1974) or dense vegetation continuously provides suitable media for conidial production (H a l a w a g y , 1989).
Even though mould spores are present in the air in concentrations considerably greater than those of pollen grains, the frequency of allergic respiratory diseases due to moulds is usually much lower than due to pollen grains of vascular plants (D ' A m a t o and S p i e ks m a , 1995).
The aim of the study was to analyse the Cladosporium season in Szczecin (western Poland) in [2004][2005][2006] and to establish a relationship between meteorological conditions and the Cladosporium spore amounts.

MATERIALS AND METHODS
The results of investigation are based on aerobiological monitoring performed in Szczecin in 2004--2006. The Lanzoni 7 Day Recording Trap was installed on the roof top in Szczecin city district Śródmieście, at the height of 21 m above ground level (52 m above sea level).
Meteorological data covering three years of study were provided by the Automatic Weather Station (Vaisala, Finland). The meteorological parameters taken into regard in the assessment of the effect of meteorological conditions on airborne fungal spores were as follows: daily level of precipitation, wind speed, relative humidity and air temperature.
The degree of correlation between particular meteorological parameters and the concentration of Cladosporium spores was described by the Pearson's correlation coeffi cient r (statistical error risk was estimated at the signifi cance level of 95%, α = 0.05) (O k t a b a , 1980).
The spore data were analysed to determine the start, end and duration of the season using the 90% method.

RESULTS
Spores of Cladosporium were found in the air in Szczecin practically throughout the whole year, with the exception of periods when temperature drops below 0ºC (usually January-February and sometimes December).
Spores of Cladosporium were recorded every day during the years 2004, 2005 and 2006. The concentration during the spore season ranged from 177 spores m -3 on 23 May to the annual peak of 31098 spores m -3 on 8 July in 2004, from 24 spores m -3 on 6 July to the annual peak of 22 737 spores m -3 on 28 July in 2005, and from 63 spores m -3 on 17 June to the annual peak of 19 560 spores m -3 on 6 August in 2006 (Fig. 1).
The lowest total number of sporomorphs (39 6063) was noted in 2006, while in the other seasons its values were markedly higher (Tab. 1). The highest maximum spore count was noted in 2005 and it was equal to 675286 spores m -3 per 24 h (Tab. 1, Figs 1, 2).
During the three years analysed, the maximum Cladosporium spore count was noted more or less in the middle of the spore season. The differences (a few days in every year) were caused by weather conditions. The vegetation season in 2004 and 2006, in comparison with 2005, started later because of frosty winter and cold spring. In 2005 the spring was dry and warm, and the spore season was the shortest and most intensive.
Based on the results of analysis of spore season duration, a conclusion may be drawn that shorter spore seasons are characterised by higher annual sums of sporomorphs.
Starting from the third decade of May and the second decade of June in 2006 to the fi rst decade of October, the spore count was high in the air over Szczecin. In 2004 and 2005 the period in which the Cladosporium spore count exceeded the threshold value of 2800 spores m -3 per 24 h in Szczecin lasted 78-79 days. In 2006 it was shorter and lasted only 43 days (Tab. 1).
In 2004 and 2005 climatic conditions were favourable for Cladosporium growth and dispersal. The annual total count for both years was over 62 0000 spores · m -3 which is ca. 40% higher than in 2006.
The growth, sporulation and dispersal of Cladosporium seem to be sensitive to changes in the climatic situation. In some of the seasons studied, the Cladosporium spore count was statistically signifi cantly correlated with the weather factors analysed (Tab. 2).
In all the seasons, the Cladosporium spore count was positive and statistically signifi cantly correlated with maximum air temperature. Only in one out of the three seasons studied, a positive and statistically signifi cant correlation was noted between the Cladosporium spore count and rainfall (Tab. 2).
Cladosporium as dry airspora is favoured by high temperature. If the temperature rises above 18º C, the Cladosporium concentration increases. Table 1 Results of aerobiological study of Cladosporium spores counts. ss -spore season established by the 90% method (with number of days), tn -total number of Cladosporium spores collected in the spore season established by the 90% method, max -maximum number of spores per 24 h, tsc -the number of days with spores count above 2800 spores in 1 m 3 threshold of spores count at which allergy symptoms develop (R a piejko e t a l. 2004).  (1993) noted that the increase of atmospheric concentrations after the rainfall is generally long lasting, with the peak observed some hours after the rain. M i t a k a k i s et al. (1997) reported a negative correlation with rain for Cladosporium.
During the analysed seasons, the correlation between the Cladosporium spore concentration and wind speed did not show a statistically signifi cant correlation. The same results were noted by L e v e t i n and D o rs e y (2006), H a s n a i n (1993), L o p e z and S a lv a g g i o (1983).
The wind speed was clearly associated with spore dispersal in Finland (K u r k e l a , 1997). The long distance dispersal of spores depends on wind conditions, but the detachment of spores dispersed in dry conditions is also strongly infl uenced by wind (M a l l a i a h and R a o , 1982).
Similar results occurred regarding relative humidity in Szczecin, 2004Szczecin, -2006. K u r k e l a (1997), S t ęp a l s k a and W o ł e k (2005) found a negative correlation between Cladosporium spore and relative humidity. During a rainy period, the level of spore concentration was low. Fernandez et al. (1998) reported that relative humidity, coupled with minimum temperature, was a factor affecting spore release. H a s n a i n (1993) did not observe any infl uence of relative humidity on Cladosporium spore concentration, contrary to other ascospores.
The high concentration and long lasting presence of Cladosporium in the air may cause and intensify clinical symptoms in people suffering from sensitivity and extend the period of presence of allergens in the atmosphere after the fl owering season of vascular plants.
The presented results refl ect the necessity of widening the spectrum of factors, e.g. weather variables, which may determine the level of spore concentrations.

CONCLUSIONS
• The higher Cladosporium spore concentration in Szczecin occurred in summer with peak periods in July (2004,2005) and August (2006), and from June to October its concentration exceeded threshold values provoking allergy symptoms.
• The analysis of duration and dynamics of the Cladosporium spore seasons revealed that in the shorter spore seasons the annual sums of sporomorphs were high, while in the longer spore seasons these sums were lower.
• During all the seasons studied, the spore count of Cladosporium was positively statistically signifi cantly correlated with maximum air temperature. A positive statistically signifi cant correlation was also observed regarding rainfall during one spore season studied.
• The Cladosporium spores count in the air of Szczecin did not show a tendency to increase or decrease; however, this observation needs to be confi rmed by long-term studies.