Survey of atmospheric pollen allergens in Delhi: seasonal periodicity.

Atmospheric pollen surveys were conducted at four different zones within the metropolitan capital city of India, Delhi, for a period of three years (1973-1975). Durham's Gravity Sampling Device was employed for sampling airborne pollen. Altogether 86 pollen types were identified from the atmosphere of Delhi; 22 types are new records for the atmosphere of Delhi. Two major pollen seasons--February to April and August to October--are recognized for Delhi. The atmosphere pollen concentration of different types as well as of the total counts showed significant annual and seasonal variations and also revealed marked differences in the quality and quantity of the pollen from site to site. Habitat factors seem to be the causal agents for the wide range of variations in the pollen content of the atmosphere of Delhi. The results of the survey are discussed in the light of relevant published literature.