Prevalence of allergenic pollen grains in the aerosol of the city of Calcutta, India: a two year study

The role of pollen grains as a causative agent of respiratory allergic disorders such as asthma and allergic rhinitis is common and very well established. The aim of this study was to assess the frequencies of airborne pollen in the Calcutta metropolis and to identify the taxa which cause significant amounts of sensitization. An aeropalynological survey of the atmosphere of Calcutta was carried out from 2004 to 2006. Skin tests were performed with a panel of the most common pollen types on local patients with clinical features of pollinosis. The meteorological factors responsible for the frequency of the pollen types were analysed. The results of monthly visits to the clinic by these patients were correlated with the monthly pollen counts of three dominant and perennial pollen taxa. The dominant pollen types were Trema (19%), Poaceae (12.98%), Casuarina (5.76%), Cocos (5.7%), Azadirachta (4.65%), Peltophorum (3.71%), Cyperaceae (3.68%), Delonix (3.18%) and Areca (2.56%). Total pollen concentration seems to have a significant positive correlation with temperature and wind speed whereas there was a negative correlation with humidity. Skin tests were most frequently found to be positive with the pollen of Poaceae (49%), Azadirachta (46%), Cocos (47%), Cyperaceae (35%), Peltophorum (33%), Areca (29%), Phoenix (26%), and Borassus (23%). A positive correlation occurred between visits to the clinic and monthly pollen count of Areca, Cocos, and Poaceae. This is the first study to design a pollen calendar for Calcutta city; it will provide useful data for enabling allergologists to achieve accurate diagnosis for patients with pollen hypersensitivity.