Pollen Calendar

The ultimate aim of an aerobiologist is to compile a pollen/spore calendar, which will be useful to allergologists and the patients suffering from allergy. The aerobiological survey of an area involves aeropalynological surveys, identification of airborne pollen and spores, and determination of atmospheric pollen count. Although the atmosphere consists of an array of pollen and fungal spores, only a few of them are responsible for allergic manifestations. The knowledge of the occurrence and concentration of these allergenic pollen and spores, which can be inferred from a pollen calendar, is of great help to the clinicians. A detailed pollen calendar of a region is a prerequisite for the immunological treatment of pollen allergies (Caulton et al, 1997).

Atmospheric surveys conducted in France and a comparative study from Montpellier and Font-Romen provided pollen calendars for Alder, Cupressaceae, Pinus, Poaceae, Rumex and Urticaceae. The pollen calendar for Switzerland is provided by Leuschner (1974). From Germany, Stix (1974) provided pollen calendars for Darmstadt and a pollen calendar for Huddinge (Nilsson and Palmberg Gotthard 1982) was formulated on a five years survey. Pollen calendars have also been published for Turin (Caramiello et al, 1989), Alexandria (Ghazaly and Fawzy 1988) and Stockholm (Nilsson and Praglowski 1974; Engstrum and Nilsson 1979), Sweden, Scotland, United Kingdom (Caulton et al, 1997). In India, pollen calendars have been complied for Secunderabad (Nayar and Ramanujam 1989), Bombay (Tripathi et al, 1982b), Allahabad, U.P. (Nautiyal and Midha, 1984), Nagpur (Deshpande et al., 1976), Chennai (Vittal et al, 2001) and for Delhi (Singh 1987). Pollen calendar of Bangalore city was compiled for two years, 1982-83 and 1983-84 (Agashe and Abraham 1988, 1990), which showed the count and relative abundance of 12 major pollen types.

A sizeable number of residents in Bangalore, India suffer from allergic manifestations. Reports claim that 1.31% of the population suffers from asthma (Asthma Research Society 1979). From a retrospective statistical study done for three years on the number of cases of asthma admission in Victoria Hospital, Bangalore, India it was found that most of them showed symptoms during August to October, which correlated to the peak of pollen season of Parthenium, Casuarina, Ricinus and Amaranth-Chenopod (Agashe and Philip 1990).

The main objective of the continuous air sampling was to get the qualitative and day-to-day variations in the concentration of different pollen and fungal spore types. These data enabled compilation of the pollen calendar, which depicts the duration and concentration of various pollen types in the atmosphere.

Pollen calendars compiled by aerobiologists provide knowledge of the occurrence and concentration of the allergenic pollen, which is of great help to the clinicians for proper diagnosis. Hence, proper interaction among the aerobiologists and allergologists is essential to tackle the problems of suffering patients. The pollen types which are most significant in the atmosphere and in considerable concentration are selected for testing on the patients. The tests include skin prick tests and evaluation of serum IgE levels in the patients. In addition, nasal, conjunctival and bronchial provocation tests are also done. Once the offending allergens are detected by using the above procedures, the patients suffering from allergic manifestations are treated by subjecting them to immunotherapy. Thus, allergy patients get sufficient protection from the effects of airborne pollen and spores if they undergo immunotherapy.

As a prerequisite to the evaluation of allergencity by an allergologist, knowledge of a pollen calendar of the local region, is essential on two basic counts. First, only the relevant antigens need to be tested on the patients, the pollen of which is most predominant in the atmosphere. There are many antigen kits available in the market and most of them will not be specific to the locality. Hence, selection of the right antigens is ensured by consulting a pollen calendar. Second, many patients suffer from seasonal allergic manifestations to the seasonal occurrence of the pollen types. It is evident from the work known earlier that the magnitude as well as quality of the annual pollen load in the atmosphere vary significantly. Therefore, it is essential that an aerobiological survey of an area is conducted continuously over a number of years (Agashe 1993).

Pollen calendars should be compiled and updated every year. The annual pollen calendars give a picture of the change in trends of the peak and concentrations over the years. Figs. 13.9 a and b show the change in peak seasons for the pollen types over the period of 1981 to 1990 for Bangalore city, India, was recorded by Agashe (1994). The six most dominant pollen types, which are also allergenically significant have been studied. These are Parthenium, Casuarina, Poaceae, Eucalyptus, Amaranth-Chenopod and Holoptelia. Parthenium, an anemophilous pollen, exhibited maximum concentration during September to December and peak incidence was observed in July and August. Casuarina pollen was present throughout

Parthenium Pollen Spreading Through Air

EXPOSED TAPE WITH THE CATCH

POLLEN GRAINS BLOWN TOWARDS THE WIND

EXPOSED TAPE WITH THE CATCH

POLLEN GRAINS BLOWN TOWARDS THE WIND

Flow Chart Pollen Grain
Flow Chart No. 13.2: Showing various steps involved in atmospheric pollen monitoring.

the year but showed two peak seasons. The main season was from February to March and the second peak was observed from September to November. The monthly maxima were observed mainly in February and September and occasionally in October, during the 10 years of survey. The Poaceae is a heterogenous group and the pollen was dominant between October and January. But the monthly peak differed over the years and was observed in July (1982), April (1983) and May (1984). Otherwise, the peak was observed in November or December. Eucalyptus pollen was also present throughout the year although the maximum concentration was noticed between October and December. The pollen of Amaranth-Chenopod was recorded throughout the year as different species of Amaranthus, flower at different times of the year. The prevalence of this pollen was maximum between July and October. Holoptelia pollen was dominant in the atmosphere between January and April.

The need for updating the pollen calendar is further substantiated by Figs. 13.9 a, b and 13.10 a, b which show the pollen calendar of Bangalore, India for 1982-1983 and 1983-84 respectively (Agashe and Abraham 1990). It can be observed that the atmospheric pollen peak over the years have not varied considerably. But during 1989-1990, the occurrence of atmospheric pollen was prolonged for most of the pollen types. Eucalyptus, Peltophorum,

APRIL MAY JUNE JULY AUG SEPT OCT

Parthenium

Syzygium

Casuarina

Grass

Eucalyptus

Ricinus

Pongamia

Amaranth chenopod

Typha

Cocos

Holoptelea

Dodonaea

Cyperaceae

Pettophorum

Mimosa pudica

Fig.13.9a Pollen calendar of Bangalore City, India for the year 1982-1983.

Parthenium Casuarina

APRIL MAY JUNE JULY AUG SEPT OCT NOV DEC JAN FEB MAR i i i i i i -i

Eucalyptus * I I Q

Syzygium ยป

Amaranth t I chenopod 1

Mimosa pudica >

Peltophomm -

Holoptelea *

Pongamia > I I

Dodonaea > I I

Fig. 13.9b Pollen calendar of Bangalore City, India for the year 1983-1984.

Cocos, Dodonaea, Mimosa, Cyperaceae and Typha had wider atmospheric pollen occurrence during 1989-1990 compared to 1982-1983. It was more pronounced in the case of Mimosa and Dodonaea. Mimosa was dominant only in June during 1982-1983 but was recorded from August to April in 1989-1990. The pollen of Dodonaea a fast-spreading weed in Bangalore was dominant only during June-July and February-March in 1982-1983 but was prevalent throughout the year except for a month of May during 1989-1990.

It is evident from the above-mentioned account that the magnitude and the quality of annual pollen load in the atmosphere can vary significantly.

As such, it is necessary that the aerobiological survey of an area be a continuous process over the years. It is imperative for an allergist to update the pollen calendar every year and to keep track of the variations in airspora. Updating of the pollen calendar every year also gives a clear picture of the duration of occurrence of pollen in the atmosphere. The prolongation of occurrence of allergenically significant pollen in the atmosphere influences the prolongation of allergy symptoms in patients. This will help in a better correlation of allergy symptoms of patients with atmospheric pollen and proper diagnosis. Another practical use of a long-term survey of an area can be the construction of statistical models for prediction of the start and intensity of pollen season.

It is necessary to make a distinction between a pollen calendar and a pollination calendar.

Pollen calendars differ from Annual calendars, in that they are concerned with events relevant only to plant flowering and the release of pollen to the atmosphere from the source.

Pollen calendars and pollination calendars are very closely linked. In fact data generated from pollination calendars precede pollen calendars. Pollination calendars deal with flowering of plants leading to pollination in different months of a calendar year. Various aspects are studied in it. They are: initiation (or onset) of flowering, peak flowering, and duration and termination of flowering.

The pollen count on the other hand concerns the occurrence, abundance and decline of pollen and spores in the atmosphere. Pollination calendars are compiled by botanists, particularly taxonomists, based on physical observations. In contrast, Pollen Calendars are compiled by aerobiologists operating pollen traps or air samplers continuously, i.e., round the clock and round the year.

Pollen often remains floating in the atmosphere for a long period even after the pollination period is over. Thus, some of these pollen grains may cause allergy outside the known pollination period. Compilation of Pollen Calendars requires a lot of effort, patience, a thorough knowledge of plants in the field and analysis of pollen data in the laboratory. In fact, compilation of pollen calendars is the ultimate aim of an aerobiologist. Pollen calendars have great significance in pollen allergy as they serve as important guidelines to allergy practitioners with respect to the onset of allergenically significant pollen season, their peak and decline in the atmosphere. In this context Pollen Calendars serve as a bridge between aerobiologists and allergists, as both are dependent on each other and equally benefit from each other.

The pollen and fungal spore spectrum keeps changing in the atmosphere depending on several parameters, including weather factors. Recently Agashe (2005) has suggested that ideally, one has to aim for a four-way correlation, that is, correlation between flowering, pollen count, weather factors and allergic manifestations. Aerobiologists should concentrate on compiling four-way correlation as depicted below.

Flowering (Pollination calendar)

Pollen count (Pollen calendar)

Weather factors (meteorology)

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    What is pollen spore calander of India?
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