What are the main types of air pollution and how are they impacted by climate change
There are many - CO, SO2, O3, NO, CH4, NO2, Volatile organic compounds (VOCs), particulate matter (PM), CO2
The sources for these include vehicles, industrial factories and power plants, fires, municipal waste & crop burning, dust from industrial construction sites etc.
What are some of the health effects of air pollution?
Air pollution increases the risks of illnesses for many diseases:
- COPD
- diabetes
- Ischemic heart disease & stroke
- Lung infections
- neonatal deaths
What are the predicted effects of air quality on climate change?
The predicted effects include:
- increased ground-level ozone
- increases in ultrafine PM (PM2·5 and others)
- increased CO2 burden
- increases in short-lived climate pollutants (hydrofluorocarbons, methane)
These are predicted to have direct physiological effects and downstream effects on climate, which then has direct physiological effects.
What is PM and why is it important physiologically?
PM are tiny pieces of solid or liquid matter associated with the Earth’s atmosphere. They can be anthropogenic or naturally sourced, (classed based on size/chemical composition) and they can have adverse effects on physiological health as well as climate change:
- eg coarse (PM2.5 - 10) include dust, pollen, can lodge into upper airways
- fine particles (PM2.5 or less) such as emissions from motor vehicles, home heating, outdoor burning, can lodge in lower airways
In perth, the bulk of PM is from industrial practices including mining, vehicular transport, agricultural and wildfires
What are some health effects arising from PM2.5 exposure?
Short term exposure include irritation to the mucus membranes (eyes, nose, throat, respiratory) leading to cough, difficulty breathing, anxiety, headaches, skin irritation and respiratory infections
Long term exposure may lead to cardiovascular and pulmonary diseases, heart disease eg arrythmia, stroke, diabetes
What size diameters do humans in their respiratory system
Trachea ~ 24 mm diameter
Bronchi ~ 12 mm diameter
Bronchioles ~ 11th branch ~ 1 mm
16th branch ~ 0.6 mm
Total effective gas exchange area ~ 75 m^2
The majority of PM2.5 reach the alveoli where they deposit due to gravitational settling, impaction at bifurcations, interception into walls, electrostatic attraction and diffusion/brownian motion collision with alveoli wall
By what mechanism of action does PM cause health effects?
- Oxidation. PM contains components like metals and organic compounds that react with O2 to generate reactive oxygen species (ROS) like superoxide, disrupting DNA, proteins, lipids, and impairing cell function and structure. The cell has antioxidants such as superoxide dismutase and glutathione however these can be overwhelmed
- Inflammation. PM trigger pattern recognition receptors on cells (eg TLR) which stimulate cytokine release activating the infllammatory pathways (NF-κB). Chronic inflammation can trigger tissue remodelling and fibrosis
- Endothelial dysfunction. PMs can enter the plasma where they can trigger adhesion molecules and increase the “leakiness” of the epithelial barrier. This causes endothelial cells to release cytokines, attracting immune cells and monocyte adhesion and migration, starting the process of atherosclerosis.
- Epigenetic changes. Alters methylation etc and affects gene expression. eg may affect mitochondrial health, increasing risks of diabetes, asthma,
- Genotoxic effects. PM is a class 1 carcinogen. PM through ROS and toxic components such as polycyclic aromatic hydrocarbons can damage DNA
Other effects include increased mucus production, increases in allergic immune responses
What are some defense mechanisms against PM?
Key defense mechanisms involve trapping and removign the PM before it can lodge into epithelial barrier of the respiratory system:
- nasal hair, turbinates, mucociliary clearance and phagocytosis by cells of the immune system.
- Antioxidants eg glutathione, SOD,catalase help to neutralise ROS and products of ROS
- Pulmonary surfactant (mix of protein and lipids) help by binding pathogens and PM and aids phagocytosis. Surfactants also aid in modulating the inflammatory response
NB Unlike biological pathogens however, PM cannot be digested by phogocytes, hence these can accummulate in the respiratory system, eventually increasing ROS and inflammation
Describe ground-level Ozone
Result of nitrogen oxides (NOx) and volatile organic compounds (VOCs) reacting together in the presence of heat and sunlight. NOx and VOCsare primarily from vehicular emissions. Today’s levels are ~ 30 - 50ppb, cf 10-15ppb pre-industrial
What effects does it have on health?
- Powerful oxidant. Ozone is a powerful oxidant, and will react with antioxidants, proteins, lipids in a process called ozonolysis, creating ROS. If there is too much O3, then antioxidant levels can be overwhelmed leading to oxidative damage at the molecular level (cell membrane, DNA) and mitochondrial dysfunction.
- Infllammatory triggers. O3 triggers epithelial cells to release cytokines, attracting an immune response. Inflammatory response can result in epithelial remodelling, bronchial thickening, increase in mucus production
- Systemic inflammation. Pulmonary inflammation can trigger a systemic inflammatory response => increased risk of heart attack and stroke.
- Disruption of Epithelial barrier. O3 damages the tight junctions increasing epithelial permeability and increased reactions to inhaled factors such as allergens, pollutants and pathogens => increases asthma risk, respiratory infections. * Health effects pose a greater risk to those with pre-existing lung disease, children and elderly
