Climate change effect on Betula (birch) and Quercus (oak) pollen seasons in the United States

Climatic change is expected to affect the spatiotemporal patterns of airborne allergenic pollen, which has been found to act synergistically with common air pollutants, such as ozone, to cause allergic airway disease (AAD). Observed airborne pollen data from six stations from 1994 to 2011 at Fargo (North Dakota), College Station (Texas), Omaha (Nebraska), Pleasanton (California), Cherry Hill and Newark (New Jersey) in the US were studied to examine climate change effects on trends of annual mean and peak value of daily concentrations, annual production, season start, and season length of Betula (birch) and Quercus (oak) pollen. The growing degree hour (GDH) model was used to establish a relationship between start/end dates and differential temperature sums using observed hourly temperatures from surrounding meteorology stations. Optimum GDH models were then combined with meteorological information from the Weather Research and Forecasting (WRF) model, and land use land coverage data from the Biogenic Emissions Land use Database, version 3.1 (BELD3.1), to simulate start dates and season lengths of birch and oak pollen for both past and future years across the contiguous US (CONUS). For most of the studied stations, comparison of mean pollen indices between the periods of 1994–2000 and 2001–2011 showed that birch and oak trees were observed to flower 1–2 weeks earlier; annual mean and peak value of daily pollen concentrations tended to increase by 13.6 %–248 %. The observed pollen season lengths varied for birch and for oak across the different monitoring stations. Optimum initial date, base temperature, and threshold GDH for start date was found to be 1 March, 8 °C, and 1,879 h, respectively, for birch; 1 March, 5 °C, and 4,760 h, respectively, for oak. Simulation results indicated that responses of birch and oak pollen seasons to climate change are expected to vary for different regions.     

A systematic review of the effects of temperature and precipitation on pollen concentrations and season timing,and implications for human health

Climate and weather directly impact plant phenology, affecting airborne pollen. The objective of this systematic review is to examine the impacts of meteorological variables on airborne pollen concentrations and pollen season timing. Using PRISMA methodology, we reviewed literature that assessed whether there was a relationship between local temperature and precipitation and measured airborne pollen. The search strategy included terms related to pollen, trends or measurements, and season timing. For inclusion, studies must have conducted a correlation analysis of at least 5 years of airborne pollen data to local meteorological data and report quantitative results. Data from peer-reviewed articles were extracted on the correlations between seven pollen indicators (main pollen season start date, end date, peak date, and length, annual pollen integral, average daily pollen concentration, and peak pollen concentration), and two meteorological variables (temperature and precipitation). Ninety-three articles were included in the analysis out of 9,679 articles screened. Overall, warmer temperatures correlated with earlier and longer pollen seasons and higher pollen concentrations. Precipitation had varying effects on pollen concentration and pollen season timing indicators. Increased precipitation may have a short-term effect causing low pollen concentrations potentially due to “wash out” effect. Long-term effects of precipitation varied for trees and weeds and had a positive correlation with grass pollen levels. With increases in temperature due to climate change, pollen seasons for some taxa in some regions may start earlier, last longer, and be more intense, which may be associated with adverse health impacts, as pollen exposure has well-known health effects in sensitized individuals.

     

Atmospheric pollen season in Zagreb (Croatia) and its relationship with temperature and precipitation

The number of individuals allergic to plant pollen has recently been on a constant increase, especially in large cities and industrial areas. Therefore, monitoring of airborne pollen types and concentrations during the pollen season is of the utmost medical importance. The research reported in this paper aims to determine the beginning, course and end of the pollen season for the plants in the City of Zagreb, to identify allergenic plants, and to assess the variation in airborne pollen concentration as a function of temperature and precipitation changes for the year 2002. A volumetric Hirst sampler was used for airborne pollen sampling. Qualitative and quantitative pollen analysis was performed under a light microscope (magnification ×400). In the Zagreb area, 12 groups of highly allergenic plants (alder, hazel, cypress, birch, ash, hornbeam, grasses, elder, nettles, sweet chestnut, artemisia and ambrosia) were identified. Birch pollen predominated in spring, the highest concentrations being recorded in February and March. Grass pollen prevailed in May and June, and pollen of herbaceous plants of the genus Urtica (nettle) and of ambrosia in July, August and September. Air temperature was mostly higher or considerably higher than the annual average in those months, which resulted in a many days with high and very high airborne pollen concentrations. The exception was April, when these concentrations were lower because of high levels of precipitation. This also held for the first half of August and the second half of September. Pollen-sensitive individuals were at high risk from February till October because of the high airborne pollen concentrations, which only showed a transient decrease when the temperature fell or there was precipitation.     

Effect of meteorological parameters on Poaceae pollen in the atmosphere of Tetouan (NW Morocco)

Poaceae pollen is one of the most prevalent aeroallergens causing allergenic reactions. The aim of this study was to characterise the grass pollen season in Tetouan during the years 2008–2010, to analyse the effect of some meteorological parameters on the incidence of the airborne Poaceae pollen, and to establish forecasting variables for daily pollen concentrations. Aerobiological sampling was undertaken over three seasons using the volumetric method. The pollen season started in April and showed the highest pollen index in May and June, when the maximum temperature ranged from 23 to 27 °C, respectively. The annual pollen score recorded varied from year to year between 2,588 and 5,404. The main pollen season lasted 114–173 days, with peak days occurring mainly in May; the highest concentration reached 308 pollen grains/m³. Air temperature was the most important meteorological parameter and correlated positively to daily pollen concentration increase. An increase in relative humidity and precipitation was usually related to a decrease in airborne pollen content. External validation of the models performed using data from 2011 showed that Poaceae pollen concentration can be highly predicted (64.2–78.6 %) from the maximum temperature, its mean concentration for the same day in other years, and its concentration recorded on the previous day. Sensitive patients suffering allergy to Poaceae pollen are at moderate to highest risk of manifesting allergic symptoms to grass pollen over 33–42 days. The results obtained provide new information on the quantitative contribution of the Poaceae pollen to the airborne pollen of Tetouan and on its temporal distribution. Airborne pollen can be surveyed and forecast in order to warn the atopic population.     

Pollen season and climate: Is the timing of birch pollen release in the UK approaching its limit?

In light of heightened interest in the response of pollen phenology to temperature, we investigated recent changes to the onset of Betula (birch) pollen seasons in central and southern England, including a test of predicted advancement of the Betula pollen season for London. We calculated onset of birch pollen seasons using daily airborne pollen data obtained at London, Plymouth and Worcester, determined trends in the start of the pollen season and compared timing of the birch pollen season with observed temperature patterns for the period 1995–2010. We found no overall change in the onset of birch pollen in the study period although there was evidence that the response to temperature was nonlinear and that a lower asymptotic start of the pollen season may exist. The start of the birch pollen season was strongly correlated with March mean temperature. These results reinforce previous findings showing that the timing of the birch pollen season in the UK is particularly sensitive to spring temperatures. The climate relationship shown here persists over both longer decadal-scale trends and shorter, seasonal trends as well as during periods of ‘sign-switching’ when cooler spring temperatures result in later start dates. These attributes, combined with the wide geographical coverage of airborne pollen monitoring sites, some with records extending back several decades, provide a powerful tool for the detection of climate change impacts, although local site factors and the requirement for winter chilling may be confounding factors.     

Regional and seasonal variation of airborne pollen and spores among the cities of South China

The composition and relative abundance of airborne pollen in urban areas of south China are strongly influenced by geographical location, vegetation, climate, and sampling device. This paper summarizes the latest reports on air pollen for 12 major cities in southern China from 1986 to 2017. The most significant taxa across all sites are Pinaceae, Poaceae, Cupressaceae, and Platanus, making up over 50% of the total airborne pollen in urban environments throughout the years. Clear shifting has been observed from long pollen seasons in the tropics to shorter periods in the south middle and north subtropical regions. There is also a discernible shift in the initiation and length of the pollen season towards higher latitudes. Both reflect the strong influence of solar radiation incidence on pollen production during spring and summer months in the southern urban areas. In this study, the comparison between airborne pollen and meteorological data indicates that the airborne pollen concentration was positively related to temperature but negatively related to precipitation and relative humidity. This study reveals that the consistent wind speed over the year had a very little but positive effect on pollen and spore concentration. The active sampler (volumetric method) in Guangzhou and Zhanjiang collected more spore and pollen species than the passive sampler (gravity method) in other cities. Understanding the future potential impacts of climate change on the phenological cycles and range of allergenic species is a critical step in the advancement of aerobiology studies in south China.     

Climate change lengthens southeastern USA lightning‐ignited fire seasons

Trends in average annual or seasonal precipitation are insufficient for detecting changes in the climatic fire season, especially in regions where the fire season is defined by wet–dry seasonal cycles and lightning activity. Using an extensive dataset (1897–2017) in the Coastal Plain of the southeastern United States, we examined changes in annual dry season length, total precipitation, and (since 1945) the seasonal distribution of thunder‐days as a correlate of lightning activity. We found that across the entire region, the dry season has lengthened by as much as 156 days (130% over 120 years), both starting earlier and ending later with less total precipitation. Less rainfall over a longer dry season, with no change in seasonal thunderstorm patterns, likely increases both the potential for lightning‐ignited wildfires and fire severity. Global climate change could be having a hitherto undetected influence on fire regimes by altering the synchrony of climatic seasonal parameters.     

Monitoring biogeographical response to climate change: The potential role of aeropalynology

To test models predicting biological reponse to future climate change, it is essential to find climatically-sensitive, easily monitored biological indicators that respond to climate change. Routine monitoring of airborne pollen, now undertaken on a near-global basis, could be adapted for this purpose. Analysis of spatial and seasonal variations in pollen levels in New Zealand suggests that the timing of onset and peak abundance of certain pollen taxa should be explored as possible bio-indicators of climate change. The onset of the airborne grass pollen season during the summer of 1988/89 varied consistently with latitude, and hence temperature, with the season in Southland commencing 8--9 days after Northland. However, these patterns were only apparent after sampling sites were separated into two groups reflecting predominantly urban or rural pollen sources. A less consistent north to south trend was apparent in the frequency of high (30 grains/m³) grass pollen levels, with high levels frequent in North Island localities in November, December and January and in southern localities during December and January. The successive onset of pollen seasons for the principal tree species during the spring-to-early summer warming interval may also be a useful bio-indicator of climate change. As well as assisting forecasts of the onset of the pollinosis season, these biogeographical patterns, reflecting climatic variation with latitude, suggest that routine aeropalynological monitoring might provide early signals of vegetation response to climate change. These conclusions are supported by recent investigations of long-term aeropalynological datasets in Europe that indicate earlier onset of pollen seasons in response to recent global warming.     

天山雪岭云杉大气花粉含量对气温变化的响应

对中国东天山天池自2001年7月至2006年7月连续5a收集的雪岭云杉大气花粉含量进行统计分析,结果表明:1)一年四季大气中都有雪岭云杉花粉,但花粉数量变化比较大,超过全年90％的大气花粉集中在5、6月份的花粉高峰期,之后花粉浓度逐渐下降,至翌年1月份浓度降至最低,2月开始花粉浓度有升高的趋势;2)5a平均花粉浓度是42.66粒/m3,最高年是2005年,花粉浓度可达99.54粒/m3,最低年2003年,仅为2.13粒/m3;3)雪岭云杉大气花粉高峰期出现在5月22至6月2日,高峰日出现在5月28至6月6日,结束日是在6月18至6月25日,平均持续时间为27 d.观测时段雪岭云杉大气花粉高峰期出现日、高峰日逐年提前,2006年出现日期比2002年提前了7d、高峰日提前9d,结束日期滞后,2006年比2002年滞后6d,花粉高峰期持续时间逐年延长,2006年比2002年延长了12d.分析显示,影响雪岭云杉大气花粉高峰期变化的主要因素是春季气温的升高;4)粗略估算每年新疆的雪岭云杉林带内由大气中降落到表土的花粉量达61 kg/hm2,新疆现有雪岭云杉52.84×104hm2,全年由大气降落到林带内表土的花粉多达3223 t,一部分降落到戈壁、荒漠以及沙漠等一些极端气候区的花粉为一些先锋种植物提供必要的营养物质,具有重要的生态意义.     

Airborne pollen of Betula,Corylus and Alnus in Zagreb,Croatia. A three‐year record

The aim of this study was to construct a picture of the influence of meteorological conditions on the start and duration of the airborne Betulaceae pollen season and the pollen concentrations in the atmosphere of Zagreb, Croatia. The study during three seasons (2002–2004) used a 7‐day Hirst‐type volumetric pollen and spore trap. Total annual airborne pollen of Alnus, Corylus and Betula greatly varied from year to year. The differences in the dates of onset of airborne pollen presence of Alnus, Corylus and Betula noted in Zagreb in 2002–2004 were controlled by weather conditions, particularly temperature and precipitation. In all years studied, airborne pollen peaks were recorded on days with temperature above 0°C and without or minimal precipitation. The mean number of days with airborne pollen concentrations exceeding levels which provoke symptoms of an allergic reaction was 15, 16 and 29 days for alder, hazel and birch, respectively. The results of the present study may provide useful data for allergologists to reach accurate diagnoses, and timely information on concentrations of airborne pollen types and concentrations for individuals with pollen hypersensitivity.     

Long distance pollen transport cause problems for determining the timing of birch pollen season in Fennoscandia by using phenological observations

The male flowering and leaf bud burst of birch take place almost simultaneously, suggesting that the observations of leaf bud burst could be used to determine the timing of birch pollen release. However, long‐distance transport of birch pollen before the onset of local flowering may complicate the utilization of phenological observations in pollen forecasting.

We compared the timing of leaf bud burst of silver birch with the timing of the stages of birch pollen season during an eight year period (1997–2004) at five sites in Finland. The stages of the birch pollen season were defined using four different thresholds: 1) the first date of the earliest three‐day period with airborne birch pollen counts exceeding 10 grains m^?3 air; and the dates when the accumulated pollen sum reaches 2) 5%; 3) 50% and 4) 95% of the annual total. Atmospheric modelling was used to determine the source areas for the observed long‐distance transported pollen, and the exploitability of phenological observations in pollen forecasting was evaluated.

Pair‐wise comparisons of means indicate that the timing of leaf bud burst fell closest to the date when the accumulated pollen sum reached 5% of the annual total, and did not differ significantly from it at any site (p<0.05; Student‐Newman‐Keuls test). It was found that the timing of leaf bud burst of silver birch overlaps with the first half of the main birch pollen season. However, phenological observations alone do not suffice to determine the timing of the main birch pollen season because of long‐distance transport of birch pollen.     

北京主要气传致敏花粉年浓度峰值日期预测

花粉是我国北方引发过敏性鼻炎最主要过敏原,花粉症发病期与花粉浓度高峰期吻合。基于北京地区2012至2020年花粉季多站、逐日分类花粉浓度观测数据分析,得出北京地区花粉浓度在3月上旬至5月中旬(可进一步划分为3月中旬至4月上旬和4月下旬至5月上旬两个高峰期)和8月中旬至9月中旬分别存在两个高峰期,第一个高峰期内优势致敏花粉种类为柏科、杨柳科和松科,第二个高峰期内优势致敏花粉种类为桑科、菊科蒿属和藜科。根据优势致敏花粉年浓度峰值日期观测数据,使用与花粉采样站点位置相匹配的逐日气象观测数据累积值,基于作物模型概念和模糊逻辑原理建立了北京地区主要气传致敏花粉年浓度峰值日期预测模型。经检验,柏科、杨柳科、松科、桑科、菊科蒿属和藜科花粉模型预测准确率分别为87.8%、80.0%、64.4%、86.7%、78.8%和81.8%。基于北京地区主要气传致敏花粉年浓度峰值日期预测模型可为本地花粉症防治提供理论参考。     

Atmospheric invasion of non-native pollen in the Mediterranean region

Most research on the impacts of plant invasion focuses on native plant performance, community structure, and ecosystem functioning. Some non-native species can also pose a risk to human health. One such risk is the allergenic nature of the pollen of some introduced plants. We examined whether patterns of airborne pollen differed between non-native and native taxa by summarizing data from seven Spanish Mediterranean localities monitored over 13 yr. The pollen spectra contained 27 native pollen taxa and 18 non-native taxa. Even though pollen from native taxa were more diverse and were present longer in the atmosphere than the non-native, in some years neither the prevalence of the two nor their weekly maximum pollen values differed significantly. However, maximum values for non-native taxa were found earlier in the season than for native pollen. A small percentage of non-native pollen includes pollen from introduced taxa that have not invaded natural habitats (e.g., ornamental plants). Non-native pollen has a larger proportion of allergenic pollen than native pollen. Therefore, the results reveal that the presence of non-native airborne pollen from naturalized and non-naturalized plant species increases the total amount of airborne allergenic pollen grains and the period of allergenic susceptibility.     

Airborne pollen parameters and their relationship with meteorological variables in NE Iberian Peninsula

The present study explores the role of the meteorological variability in the pollen production and the timing of the airborne pollen season by analysis of the correlation between precipitation, insolation and temperature and the main standardised airborne pollen parameters of 22 taxa collected at 6 localities in Catalonia (NE Spain). The pollen parameters included in the study were: Annual Pollen Integral and the Start, End and Length of the Main Pollen Season. Considering that the Main Pollen Season of most of the taxa in Catalonia lasts from spring to summer or autumn, correlations between the pollen parameters and winter (from December to March) values of meteorological variables were calculated. Correlations between Monthly Pollen Integral and monthly values of the meteorological variables were also calculated. The results obtained report the synchronism registered in the variations of pollen concentration with precipitation (negative), insolation (positive) and temperature (positive). Temperature was the meteorological variable that showed a greater influence in the pollen production and the timing of the pollen season, being insolation the least one. The Start of the Main Pollen Season was the pollen parameter more correlated with the meteorological variables, especially with winter temperatures.     

Automated pollen monitoring system using laser optics for observing seasonal changes in the concentration of total airborne pollen

The development of a simple and automatic pollen measurement methodology is required to manage allergic problems caused by airborne pollen. We developed a device and algorithm to automatically monitor airborne pollen by using basic laser optics technology. The device measures the sideward and forward scattering intensities of laser light from each particle. Because this device provides detailed temporal variation in the pollen concentration, the dispersal dynamics of airborne pollen can be effectively analyzed. We compared the pollen counts obtained with the automated method and standard Hirst-type method. Scatter-plot graphs were constructed of the forward and sideward scattering intensities of the observed particles. An extract window methodology was used to estimate the concentrations of the major allergenic pollens. The extract window parameters were obtained for major types of allergenic pollen. The results suggest the possibility of developing a device for monitoring several types of airborne pollen simultaneously. We determined the standard extract window to be used for estimating the concentration of all types of airborne pollen together. A field experiment was performed to evaluate the automated monitoring system with the standard extract window. The estimated temporal variation pattern of the total airborne pollen concentration agreed well with the observed temporal variation pattern for the whole pollen season. The pollen monitor was able to estimate the overall features of seasonal changes in the total airborne pollen concentration.     

Models for forecasting airborne Cupressaceae pollen levels in central Spain

The influence of meteorological variables on airborne Cupressaceae pollen levels in central Spain was analyzed, and prediction models based on polynomial and multiple regressions were used to predict pollen counts throughout the pollen season. The Cupressaceae pollen type was selected in view of both its abundance in the atmosphere of the central Iberian Peninsula (particularly from January to March) and its allergenic importance. Sampling was performed uninterruptedly over a 5-year period, using a Hirst volumetric sampler and the sampling method established by the Spanish Aerobiology Network. Temperature displayed the strongest (positive) correlation with Cupressaceae pollen counts. Polynomial and multiple regression analysis showed that maximum temperature was the most influential variable included in prediction models. The prediction equations obtained for the study period were reasonably satisfactory, accounting for 48% and 59% of the variation in airborne pollen levels.     

空气致敏花粉污染研究进展

对空气致敏花粉污染概念的提出 ,空气致敏花粉污染的特点和影响因素 ,花粉采集方法的改进以及空气致敏花粉污染的研究进展等方面进行了总结 ,指出了研究中存在的问题 ,并对研究前景进行了展望     

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

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

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.