1. Barbara MacKinnon PhD New Brunswick Lung Association
How Pollen, Air Pollution and Climate Change Interact to Exacerbate Asthma
Barbara MacKinnon PhD
New Brunswick Lung Association

2. Key Points
The incidence of asthma worldwide is increasing and people living in urban areas have higher rates of asthma than those in rural areas.
Exposure to air pollution exacerbates asthma.
Air pollutants interact with pollen to make pollen more allergenic.
Climate Change is increasing pollen production in some plants and is increasing certain types of air pollution.
Farinas Sedghy et al. Rep Biochem Mol Biol Apr 6(2):
D’Amato,G. et al. J Investig Allergol Clin Immunol. 2010; 20 (2):
Zang, Q Et al. J. Thoracic Disease (1):14

3. Pollen Season in Canada

4. The Pathway from Pollen to Asthma
Airborne allergens including pollen are a major cause of asthma and allergic rhinitis.

5. (More About T Cells)
Functions of T cells in asthma: more than just TH2 cells
Clare M. Lloyd* and Edith M. Hessel Nat Rev Immunol Dec; 10(12): /nri2870.

7. (More about T Cells)
Asthma is characterized by airway hyperresponsiveness (AHR), recruitment of inflammatory leukocytes to the lung and tissue remodelling, including mucus production and airway smooth muscle changes.
T cells are thought to influence the nature and magnitude of the allergic immune response by the cytokines that they secrete. T helper 2 (TH2) cells may promote eosinophil recruitment. T helper 1 and 17 cells may be associated with severe, steroid-resistant asthma. Regulatory T cells are able to downregulate pulmonary immune responses and may control immune homeostasis in the lungs.

8. Air Pollution
Particulate Matter PM Sulphur Oxides SOx Nitrogen Oxides NOx Volatile Organic Compounds VOCs Carbon Monoxide CO Heavy Metals
Ground-Level Ozone O3

9. Mechanisms for air pollution exacerbation of asthma
The effect of air pollution on asthma depends on:
1. Exposure level and duration
Types and concentrations of air pollutants
Ventilation, climatic conditions
Human behaviour that determines personal location and breathing rate
2. Chemical interaction between air pollutants and pollen
3. Airway damage by air pollution which predisposes them to the effect of pollen

10. What is an allergen?
An allergen is an antigen that triggers an allergic immune response. An antigen is a cell protein or glycoprotein, often found on the surface of cells but which can also be released by cells, that triggers an immune response. Cell surface identifying chemicals are antigens (think of the A B O blood markers). Cells of invading organisms have these markers and our immune system recognizes them as foreign and attacks them. Although pollen is mostly harmless to us, our immune system sometimes sees them as invaders.

11. Chemical interaction/ association between pollution and pollen:
The allergenic potential of pollen could be enhanced by chemicals. Some components of air pollutants can stick to pollen particles and act as adjuvants, stimulating IgE-mediated responses such as the bursting of mast cells that release histamine. Diesel exhaust has been shown to act in this way.
Adjuvants are chemicals that boost the ability of B Lymphocytes to make antibodies like IgE.

12. Chemical interaction/ association between pollution and pollen:
Pollutants may increase the production of allergens in pollen, leading to a worse asthma attack due to increased production of IgE antibodies. Pollution can damage the pollen cell wall, releasing small allergens into the environment. Because allergens are smaller than pollen grains, this facilitates penetration deeper into the airways.

13. Chemical interaction/ association between pollution and pollen:
Some plants recognize air pollutants as a stressor and increase the production of pollen to produce more individuals in a subsequent generation.

14. Air pollution damages airways and predisposes them to the effect of pollen: We know that pollen can cause asthma and trigger attacks. But some studies suggest that exposure to air pollution can also result in the initial development of asthma. Air pollution probably causes oxidative injury to the airways, leading to inflammation, remodelling, and increased risk of sensitization. Air pollution alone can trigger an asthma attack. Air pollution causes damage to airway mucous membranes and impairs ciliary clearance which traps allergens and brings them in contact with cells of the immune system, increasing sensitization of the airway and the chain reaction of events that lead to an asthma attack. Michael Guarnieri, MD and John R. Balmes, MD Lancet May 3; 383(9928): 1581– Talat Islam, et al. Thorax Nov; 62(11): 957–963

15. Impact of Climate Change
Increased CO2 and global temperatures
Impact on Pollen:
Longer growing and blooming season
Increased pollen counts
Changes in nature of antigenic proteins
Changing distribution of plants and weather patterns creates new exposures for populations
Impact on Air Pollution:
Hotter air can increase formation of ground-level ozone
Drought leads to wildfires and increased wind-blown dust (PM)
Increased number of hot days increases air conditioning which can increase pollution from energy sources (depending on the fuel)

16. Climate Change
Pollen
Air pollution
Asthma