Airborne pollen allergen quantification or pollen grain counts?

Abstract

There is a generalized consensus about the need to know the local aeropalynology in order to be able to properly understand pollinosis and make a correct etiological diagnosis. On the other hand, the aerobiological data provided by monitoring networks allow effective measures to be taken to prevent exposure.

The aeropalynological characterization of the atmospheric aerosol is traditionally carried out by sampling by volume the particles suspended in the atmosphere and subsequently counting the pollen and fungus types present in the samples. One of the most commonly used sampling methods is based on the one proposed by Hirst in 1952. The correct identification of the pollen and fungus types present in the samples requires an important, previous education and training so as to be able to recognize the morphological features that would lead to a correct identification of the former.

In the last decades of the 20th century data began to appear in scientific publications that drew the interest of researchers to the quantification of pollen allergens. In addition, the lack of a link between pollen grain counts and pollinosis symptoms (rhinitis, conjunctivitis and asthma) has been pointed out. On the other hand, there is controversy around the size of pollen grains and their likelihood to penetrate deeply into the respiratory tract. All this evidence led to the introduction of the concept of allergen load and the need to quantify it in the atmospheric aerosol.

A lot of work has been done in this regard. In this paper we will supplement our experience in the subject matter with a review of the published literature in an attempt to determine whether we can answer the question posed by Beggs back in 1998: do we have to take pollen or pollen allergens into account? The analysis of the subject matter shows that there is not always a close correlation between pollen grain counts and the allergen load. In some cases, this behavior was expected and can be explained easily; in others, the reasons are not as clear. However, it has not been possible up until now to quantify all of the airborne allergens that are present in the bioaerosol. Thus, we are not ready to replace traditional aeropalynological counts yet and need to keep researching in this field to be able to develop a airborne allergen sampling and quantification methodology that can be implemented in aerobiological atmosphere monitoring networks. Based on the literature review we have conducted, we propose other possible avenues for aerobiological studies and voice our opinions about their future prospects.