Pollen, Allergens, and Human Health

Allergenic pollen is produced by the flowers of a number of trees, grasses, and weeds found throughout the world. Human exposure to such pollen grains can exacerbate pollen-related asthma and allergenic conditions such as allergic rhinitis (hay fever). While allergenic pollen comes from three main groups of plants—certain trees, grasses, and weeds—many people are sensitive to pollen from one or a few taxa only. Weather, climate, and environmental conditions have a significant impact on the levels and varieties of pollen grains present in the air. These allergenic conditions significantly reduce the quality of life of affected individuals and have been shown to have a major economic impact. Pollen production depends on both the current meteorological conditions (including day length, temperature, irradiation, precipitation, and wind speed/direction), and the water availability and other environmental and meteorological conditions experienced in the previous year. The climate affects the types of vegetation and taxa that can grow in a particular location through availability of different habitats. Land-use or land management is also crucial, and so this field of study has implications for vegetation management practices and policy. Given the influential effects of weather and climate on pollen, and the significant health impacts globally, the total effect of any future environmental and climatic changes on aeroallergen production and spread will be significant. The overall impact of climate change on pollen production and spread remains highly uncertain, and there is a need for further understanding of pollen-related health impact information. There are a number of ways air quality interacts with the impact of pollen. Further understanding of the risks of co-exposure to both pollen and air pollutants is needed to better inform public health policy. Furthermore, thunderstorms have been linked to asthma epidemics, especially during the grass pollen seasons. It is thought that allergenic pollen plays a role in this “thunderstorm asthma.” To reduce the exposure to, or impact from, pollen grains in the air, a number of adaptation and mitigation options may be adopted. Many of these would need to be done either through policy changes, or at a local or regional level, although some can be done by individuals to minimize their exposure to pollen they are sensitive to. Improved aeroallergen forecast models could be developed to provide detailed taxon-specific, localized information to the public. One challenge will be combining the many different sources of aeroallergen data that are likely to become available in future into numerical forecast systems. Examples of these potential inputs are automated observations of aeroallergens, real-time phenological observations and remote sensing of vegetation, social sensing, DNA analysis of specific aeroallergens, and data from symptom trackers or personal monitors. All of these have the potential to improve the forecasts and information available to the public.