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| Scientists' Contributions | ||
Ragweed pollen concentration and its meteorological components in Szeged, Hungary
by
László Makra 1, Miklós Juhász 2, Emőke Borsos 1 and Rita Béczi 1
1 Department of Climatology and Landscape Ecology, University of Szeged,
H-6701 Szeged, P.O.B. 653, Hungary;
2 Miklós Juhász, Department of Botany, University of Szeged,
H-6701 Szeged, P.O.B. 657, Hungary;
ABSTRACT
About 30 % of the Hungarian population has some type of allergy, 65 % of them have pollen-sensitivity, and at least 60 % of this pollen-sensitivity is caused by ragweed. The air in the Carpathian basin is the mostly polluted with ragweed pollen not only in Europe but in the world, too. The number of ragweed pollen shows, with fluctuations, significant increasing trend.
Pollen measurements in Szeged started in June 1989. The study represents ragweed pollen characteristics for Szeged and other Hungarian and foreign cities. Most serious period of ragweed pollen load, demonstrated by the Makra-test is shown. Connection between, on the one hand, the ragweed pollen concentration and, on the other hand, the examined meteorological variables is analysed by factor analysis. Rank of the variables influencing ragweed pollen concentration is determined by special transformation.
Key words: pollen allergy, ragweed pollen concentration, Makra-test, factor analysis, special transformation
POLLEN ALLERGY
Pollen allergy has become a widespread disease in recent years. Nowadays, every 5th or 6th person, as an average, suffers from this immune system disease in Europe. Pollinosis involves unpleasant symptoms and can become asthma. It has been proved that persons fallen ill with pollen allergy, cannot concentrate on their work, feel unwell and can be on sick leave many times.
The aim of our study is to give a short survey of the history of ragweed and of its pollen’s effects on humans, then to analyse the connection of ragweed pollen counts with meteorological elements in Szeged city.
ORIGIN AND DISTRIBUTION OF RAGWEED
This unpleasant weed has its probable origin in Southern North America. This is a plant that has evolved in reaction to a dry climate and open environment. Among 42 species of the Ambrosia genus, only seaside ragweed (Ambrosia maritima) is native in Europe, namely in the Mediterraneum. Its earliest colonisation occurred in Dalmatia (Croatia), where it was an endemic plant on sandy seashores in the Ragusa (recent name: Dubrovnik, Croatia) and Budva (Montenegro) area and on the islands, firstly described in 1842. (Járai-Komlódi and Juhász, 1993).
Distribution of ragweed in Europe started after the First World War. Recently, there are three main regions infected by ragweed in Europe: the Rhône valley (France), Northern Italy and, the most infected region, the Carpathian Basin.
RAGWEED IN HUNGARY
In Hungary, its appearance was noticed at the beginning of the 20th century at Orsova, near the southern border of the country, along the bank of the Danube. One of the popular names of ragweed in Hungary is „Serbian grass”, which also refers to its place of origin. Ragweed with mugwort leaves (short ragweed) got acclimatised most rapidly; only this species lives here widely. Samples of short ragweed were found in the southern part of Transdanubia in the 1920s, and gradually – within 30 years – they occupied the whole region. Since then, having been spread all over the country, it has become the most common weed in Hungary. However, when airborne pollen composition in Szeged (southern part of the Great Hungarian Plain) was analysed in 1968, no ragweed pollen was found there (Simoncsics et al., 1968). In the southern part of the Great Hungarian Plain there have been more favourable habitats, therefore all stages of the life-cycle (germination, growth, flowering, seed production) start earlier and last longer than those in other parts of the country.
CLIMATIC CHARACTERISTICS OF SZEGED
Szeged (20°06'E; 46°15'N) lies near the confluence of the Tisza and Maros Rivers. It is the largest city in the south-eastern part of Hungary. The number of inhabitants of the city is up to 168,000 and the surface of its built-up area is about 46 km2. Though Szeged and its surroundings is flat and open region, the city has the lowest elevation in Hungary. In addition, the country lies in the Carpathian Basin. Hence, Szeged is a so-called double-basin situated city, which strengthens the effects of anticyclonic circulation patterns in accumulating pollutants together with pollen concentrations. The mean annual temperature is 11.2°C and the mean annual precipitation is 570 mm.
DATA
In Szeged, pollen content of the air has been examined with the help of a high volume pollen trap (Lanzoni VPPS 2000) since 1989. The air sampler is found in the city, on the roof (20 m height from the city surface) of the building of Faculty of Arts, University of Szeged. Meteorological data were obtained from the monitoring station located 2 km from the sampling site in the downtown, which is operated by the ATIKÖFE (Environmental Protection Inspectorate of Lower-Tisza Region, Branch of the Ministry of Environment).
Fig. 1. Geographical position of Szeged, Hungary and built-in types of the city
[a: city centre (2-4-storey buildings); b: housing estates with prefabricated concrete slabs (5-10-storey buildings); c: detached houses (1-2-storey buildings); d: industrial areas; e: green areas; (1): monitoring station]
The data basis consists of diurnal ragweed pollen counts and averages of 13 meteorological parameters for not only the main pollination periods (MPP), but the whole data basis of the years 1997-2001, as well. The meteorological parameters are as follows: mean air temperature [Tmean (°C)], maximum air temperature [Tmax (°C)], minimum air temperature [Tmin (°C)], diurnal temperature range [Δ T (°C)], relative humidity [RH (%)], irradiance [I (Wm-2)], wind speed [WS (ms-1)], vapour pressure [VP (mb)], saturation vapour pressure [E (mb)], potential evaporation [PE (mm)] dew point temperature [Td (°C)], diurnal sum of precipitation [P (mm)] and intensity of precipitation [PI (mm/min)]. The criterion of MPP was introduced by Nilsson and Persson (1981), which takes into account 90 % of the annual total pollen concentration, eliminating the initial 5 % and the final 5 %.
The ragweed pollen count and the mean air temperature of the previous day as well as those of the preceding 2 nd and 3 rd days are also taken into consideration. Furthermore, average diurnal pollen counts for the analysed period 1997-2001 are also used.
RAGWEED POLLEN COUNTS IN EUROPE, THE UNITED STATES AND SZEGED
Table 1 shows the list of some highest counts on peak days (as a comparison, data of some sites in Pennsylvania, USA are also presented), while Table 2 displays annual totals of ragweed pollen grains.
All the highest counts are reported from the Carpathian Basin, Serbia and Hungary. Novi Sad (Serbia-Montenegro), the southern part of the Great Hungarian Plain (Szeged) and Southwest Hungary (Pécs) are the regions most polluted with ragweed pollen not only in the Carpathian Basin itself but in Europe, too. No higher count than 3247 pollen grains per m3 of air (Novi Sad) has been measured in Europe or in the United States on peak days (www.dep.state.pa.us/dep/deputate/airwaste/aq/pollen/sites). The highest values observed in Novi Sad and Szeged on peak days are about one order of magnitude higher than those in other cities of Europe and the United States, which are considered to be rather polluted. On the reported peak days, there is more ragweed pollen even in the air of Budapest, having the lowest value among the listed Hungarian cities, than the total amount for the cities listed from Europe and the United States having highest values (Table 1.). When considering annual totals, the highest ragweed pollen counts in Novi Sad and Szeged are many times as much as the total amount for the most polluted cities listed from the rest of Europe (Table 2.).
| City | Country | Year | Counts on peak days |
| Novi Sad | Serbia-Montenegro | 2001 | 3,247 |
| Szeged | Hungary | 1991 | 2,003 |
| Szeged | Hungary | 1994 | 1,899 |
| Szeged | Hungary | 1992 | 1,658 |
| Pécs | Hungary | 1994 | 1,394 |
| Budapest | Hungary | 1996 | 1,254 |
| Novi Sad | Serbia-Montenegro | 1999 | 723 |
| Pozsony | Slovakia | 1995 | 391 |
| Pozsony | Slovakia | 1997 | 267 |
| Easton | USA | 2001 | 213 |
| Erie | USA | 2001 | 174 |
| Ljubljana | Slovenia | 1997 | 118 |
| Pittsburgh | USA | 2001 | 90 |
Table 1. Ragweed pollen count on peak days (list of some highest reported counts), pollen grains / m3 air
Characteristics of the main pollination period of ragweed pollen for the examined five-year data set, as well as their averages are shown in Table 3a. These characteristics highly depend on the meteorological background (Makra et al., 2002).
The starting date of the pollination period varies widely, between 20 June and 13 July, whereas the finishing date (between 11 – 29 October) show a much more limited range. The duration, average diurnal count and total count, except for 1998, show definite increasing trends.
| City | Country | Year | Annual total count |
| Novi Sad | Serbia-Montenegro | 2001 | 20,559 |
| Szeged | Hungary | 1994 | 17,142 |
| Szeged | Hungary | 1991 | 16,781 |
| Szeged | Hungary | 1992 | 16,111 |
| Pécs | Hungary | 1994 | 15,092 |
| Pécs | Hungary | 1993 | 13,625 |
| Novi Sad | Serbia-Montenegro | 1999 | 11,246 |
| Szekszárd | Hungary | 1994 | 9,938 |
| Zalaegerszeg | Hungary | 1994 | 8,478 |
| Budapest | Hungary | 1993 | 6,753 |
| Debrecen | Hungary | 1993 | 3,202 |
| Bécs | Austria | 1992 | 1,869 |
| Brno | Czeh Rep | 1995 | 1,685 |
| Pozsony | Slovakia | 1994 | 1,569 |
| Lugano | Switzerland | 1994 | 932 |
| Szófia | Bulgaria | 1993 | 179 |
Table 2. Annual total count of ragweed pollen (list of some highest re-ported counts), pollen grains / m3 air
It is noted that the threshold value for clinical symptoms for the majority of sensitised patients is considered to be 20 pollen grains per m3 of air (Jäger, 1998). According to some authors, 50 pollen grains per m3 of air is the threshold value at which 60-80 % of patients suffering from pollinosis are sensitive to ragweed pollen (Juhász, 1995). On the other hand, at the Hungarian National Health Centre this value is 30 pollen grains per m3 of air. At the same time, the lowest threshold value is 10 pollen grains per m3 of air. Ragweed pollen counts for the examined five-year period and the number of days with higher pollen grains than the threshold values, are found in Table 3b.
| Characteristics | 1997 | 1998 | 1999 | 2000 | 2001 | Average |
| Starting date | 9 July | 13 July | 6 July | 20 June | 7 July | 5 July |
| Finishing date | 29 October | 14 October | 23 October | 22 October | 11 October | 20 October |
| Duration (days) | 113 | 94 | 110 | 95 | 97 | 102 |
| Average diurnal count (pollen grains / m3) | 61 | 29 | 67 | 88 | 93 | 68 |
| Total count (pollen grains / m3) | 7,994 | 3,859 | 8,847 | 11,592 | 12,277 | 8,914 |
Table 3a. Characteristics of ragweed pollen in Szeged for their main pollination period, according to Nilsson and Persson (1981)
During the examined period, both the total counts and counts on peak days increase with fluctuations. Diurnal ragweed pollen counts are over 50 pollen grains per m3 of air for 24-50 days of its 3-months long season, which means severe pollen load of the air. According to the data, the number of days with higher than the threshold values increase, too.
Comparing results of the two periods (1990–1996, annual data; 15 July – 15 October, 1997–2001), latest values seem to be less extreme. However, the number of days with higher than 30 pollen grains per m3 of air increased definitely in the recent period.
| Year | Counts on peak days (pollen grains / m3) | *Number of days with higher than 20 pollen grains / m3 | **Number of days with higher than 30 pollen grains / m3 | ***Number of days with higher than 50 pollen grains / m3 |
| 1997 | 848 | 41 | 37 | 34 |
| 1998 | 332 | 37 | 31 | 24 |
| 1999 | 571 | 41 | 37 | 32 |
| 2000 | 608 | 61 | 57 | 50 |
| 2001 | 1,125 | 56 | 50 | 43 |
| 1average | 697 | 47 | 47 | 37 |
| 2values | 301-2,003 | 16-43 |
**Threshold value for clinical symptoms after the Hungarian National Health Centre
***Threshold value for clinical symptoms after Juhász and Gallowich (1995)
1main pollination period, 1997–2001
21990–1996, annual data
Fig. 2. Sub-periods with significantly different averages of ragweed pollen counts from the mean of the entire data series, i.e. the “breaks”, diurnal average pollen counts, Szeged, 15 July – 15 October, 1997-2001
OTHER CHARACTERISTICS OF RAGWEED POLLEN CONCENTRATION
We determined whether or not significant differences can be found between the average of an arbitrary sub-sample of the mentioned time series and that of the whole sample. It was found that averages of the sub-samples with periods between 15 July – 14 August and 17 September – 10 October are significantly lower than that of the whole sample, while the average of the period between 16 August – 13 September is significantly higher than that of the whole sample. This means that, according to the examined data set, the period between 16 August – 13 September can be considered to be the most polluted one by ragweed pollen in the air; hence, the most dangerous one for pollinosis (Fig. 2.). The result received by this method confirms data of traditional pollen calculations.
| Parameters | Factor 1 | Factor 2 | Factor 3 | Factor 4 |
| pollen | 0,226 | -0,005 | 0,232 | 0,740 |
| Tmean | 0,973 | 0,184 | 0,012 | 0,108 |
| E | 0,973 | 0,183 | 0,001 | 0,095 |
| Td | 0,961 | -0,209 | -0,044 | 0,116 |
| VP | 0,960 | -0,210 | -0,056 | 0,100 |
| Tmax | 0,929 | 0,222 | 0,216 | 0,070 |
| Tmin | 0,830 | 0,053 | -0,517 | 0,090 |
| PE | 0,738 | 0,626 | 0,072 | 0,066 |
| RH | 0,014 | -0,954 | -0,140 | 0,029 |
| I | 0,054 | 0,889 | 0,058 | -0,029 |
| DT | 0,006 | 0,193 | 0,943 | -0,035 |
| WS | 0,018 | -0,036 | -0,319 | 0,749 |
| Eigenvalue | 6,145 | 2,470 | 1,163 | 1,018 |
| Explained variance, % | 51,209 | 20,580 | 9,690 | 8,486 |
| Cumulative variance, % | 51,209 | 71,789 | 81,479 | 89,965 |
Table 4. Factor loadings of the rotated component matrix. Loadings higher than are written by bold
CONNECTION OF RAGWEED POLLEN CONCENTRATION WITH METEOROLOGICAL ELEMENTS
In order to analyse the connection between ragweed pollen concentration and meteorological elements, multivariate statistical analysis was applied (SPSS 9.0 version).
| Variables | Factor 1 | Rank |
| pollen | 0,740 | – |
| Tmean | 0,102 | 3 |
| E | 0,089 | 5 |
| Td | 0,109 | 2 |
| VP | 0,093 | 4 |
| Tmax | 0,065 | 7 |
| Tmin | 0,081 | 6 |
| PE | 0,062 | 8 |
| RH | 0,028 | 11 |
| I | -0,029 | 9-10 |
| ΔT | -0,029 | 9-10 |
| WS | 0,747 | 1 |
Table 5. Effect of variables on daily pollen concentration and rank of them on the basis of factor loadings specially transformed to Factor 1
Factor analysis makes it possible to represent connections among the original 12 variables by far less number of so called “theoretical variables” so that these factors together explain as much information of original variable, as possible. Using this procedure, connections among many variables can be interpreted and evaluated more easily. According to this method, information obtained on the original 12 variables was condensed into 4 theoretical variables; namely, into 4 factors, which together explain 90 % of information of the original variables. Connections among variables within each factor can be explained by the so called factor loadings belonging to the variables (Table 4). In order to rank effects of meteorological variables on ragweed pollen concentration (namely, to classify variables partly as essential and partly as unimportant ones), special transformation of the 2 nd 3 rd and 4 th factors to Factor 1 was required. Results are shown in Table 5.
Of all meteorological variables, only wind speed (WS) indicates significant (and positive) connection with ragweed pollen concentration. Though the other variables were also ranked, their effect – according to their factor loadings – cannot be measured. When wind is strengthening, a vast amount of ripe ragweed pollen come to the air and – according to our result – only this meteorological element modifies substantially the concentration of ragweed pollen.
SUMMARY
Parameters of ragweed pollen [maximum daily concentration per year; total number per year; first observation day; last observation day; duration (day); average daily number; number of days exceeding threshold value of clinical symptoms (20-30-50 pollen grains per m3 per day)], with slight fluctuations, show increasing trends.
Ragweed pollen load of Szeged is most serious between 16 August – 13 September. Hence, this is the most dangerous period for hay-fever. The above-mentioned period of highest pollen concentration, established by the Makra-test, confirms results of empirical pollen calculations.
Application of factor analysis reduced dimension of the original data set (daily ragweed pollen concentration and the examined 11 meteorological variables) in order to detect connections among them more easily. After performing factor analysis, 4 factors were retained according to the Guttmann-criterion. These 4 factors explain 90,0 % of the total variance of the original 12 variables. Connections among variables, within each factor, can be well interpreted on the basis of their significant factor loadings. After performing special transformation, we concluded that among all the 11 meteorological variables only wind speed (WS) modifies substantially ragweed pollen concentration.
ACKNOWLEDGEMENT
The authors are indebted to Szilvia Horváth (Department of Climatology and Landscape Ecology, University of Szeged, Hungary) and Predrag Radisic (University of Novi Sad, Laboratory of Palinology and Ecology, Serbia-Montenegro) for fruitful discussions. The authors thank Zoltán Sümeghy for his contribution with digital maping. This research was supported by the grants from the Hungarian Academy of Sciences, OTKA (T-34765).
REFERENCES
Jäger, S., 1998: Global Aspects of Ragweed in Europe. Satellite Symposium Proc.: Ragweed in Europe. 6th Int’l Congress on Aerobiology, p. 6-8. Perugia, Italy, 31.08. – 05.09. 1998
Járai-Komlódi, M. and Juhász, M., 1993: Ambrosia elatior (L.) in Hungary (1989-1990). Aerobiologia, 9, 75-78.
Juhász, M., 1995: New results of aeropalynological research in Southern Hungary. Publications of the Regional Committee of the Hungarian Academy of Sciences, Szeged, 5, 17-30.
Makra, L., Horváth, Sz., Pongrácz, R. and Mika, J., 2002: Long term climate deviations: an alternative approach and application on the Palmer drought severity index in Hungary. Physics and Chemistry of the Earth, 27, 1063-1071.
Nilsson, S. and Persson, S., 1981: Tree pollen spectra in the Stockholm region (Sweden), 1973-1980. Grana, 20, 179-182
Simoncsics, P., Osváth, P. and Balázs, I., 1968: Qualitative analysis of pollen composition in the air. Rheumatologia, Balneologia, Allergologia, 9, 117.
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