The World Health Organization (WHO) estimates that about 90% of people worldwide breathe air that exceeds the recommended level of pollutants. With the rise in city smog and forest fires, air pollution poses a major threat to our health, both indoors and outdoors.
If you're reading this, you are likely concerned about air pollution. Indoor and outdoor pollution sources differ, as does the composition of the compounds that can have a negative effect on our bodies. While most sources of pollutants are man-made (eg. the burning of fossil fuels, agriculture, waste management, or mining operations), non-human activities (eg. from animals and vegetation) also contribute to poor outdoor air quality.
There are over 200 types of regulated pollutants that can cause cancer or have other adverse health effects, but the primary components of outdoor air pollution are as follows:
Particulate Matter (PM)
PM is a common proxy indicator for air pollution and it affects more people than any other pollutant. PM is a mixture of solid particles and liquid droplets that are suspended in the air, such as aerosols, smoke, fumes, dust, ash, and pollen.
PM can be found in various sizes. Particles with a diameter of 10 microns (PM10) or less can be breathed in and lodged deep inside our lungs. Breathing in fine particulate matter with a diameter of 2.5 microns or less (PM2.5) is incredibly health-damaging as it can penetrate the lung barrier and enter our blood system. Prolonged and chronic exposure to fine particulate matter is known to cause serious health problems, such as premature death, lung cancer, and cardiovascular or respiratory disease.
Volatile Organic Compounds (VOCs)
VOCs are compounds that have a high vapor pressure and low water solubility. These compounds are chemicals that can be found in many commonplace household products, such as paints, cleaning supplies, pesticides, and printers. Scented products are often comprised of VOCs.
Many VOCs are human-made chemicals found in industrial solvents, such as tetrachloroethylene, benzene, or formaldehyde, which evaporate quickly at room temperature when released. Products that contain these chemicals can emit VOCs into the air while you are using them or when they are stored. In fact, concentrations of VOCs are consistently higher indoors - often up to 10 times higher than outdoor spaces. Studies show that using products that contain VOCs exposes individuals to high pollutant levels, and elevated concentrations can remain in the air long after the product has been used. Breathing in VOCs may not be harmful in small doses, but chronic exposure can result in long-term health effects.
Nitrogen Oxide (NOx)/Nitrogen dioxide (NO2)
NOx is a group of highly reactive gases. NO2 is a NOx gas and is produced from the reaction of nitrogen and oxygen during combustion (eg. when fossil fuels are burned at high temperatures). These gases react with other chemicals in the air to form PM. Breathing air with a high concentration of NO2 can irritate the airways in our respiratory system and cause inflammation. Short-term exposure can also aggravate asthma and other respiratory diseases, resulting in physical symptoms such as coughing, wheezing, or breathing difficulties. Long-term exposure can result in the development of respiratory diseases.
Sulfur Dioxide (SO2)
SO2 is a sharp-smelling gas composed of sulfur and oxygen. It is created through industrial processes when sulfur-containing fuel is burned and is a contributor to PM levels in the air. Individuals who are located near coal-fired power plants, ports, smelters, or other sources of sulfur dioxide receive the highest exposure; however, once SO2 is in the air, it changes chemically into sulfate particles that can blow hundreds of miles away. SO2 is the primary component of acid rain.
SO2 causes a range of harmful effects on the respiratory system. Symptoms include coughing, wheezing, shortness of breath, and chest tightness. Over time, continued exposure at high concentrations reduces the ability of the lungs to function properly.
Ground-level ozone (O3)
Ozone can be found in the Earth's upper atmosphere as well as at ground level. It can be either innocuous or harmful, depending on where it is located; the stratospheric ozone found in the upper atmospheric is beneficial, as it is a protective layer that shields the earth from the sun's harmful ultraviolet (UV) rays.
However, ground-level ozone, O3, is a harmful air pollutant: a colorless and odorless gas that is the main component of smog. It is the result of chemical reactions between NOx and VOCs in the presence of sunlight. O3 irritates the respiratory tract and eyes. Exposure to high levels can result in physical symptoms such as chest tightness, coughing, and wheezing. Individuals with respiratory and heart problems are more susceptible to risk.
Carbon Dioxide (CO2)
CO2 is the result of combustion - either in industrial processes or metabolic processes in living organisms - and is released into the air as a colorless and odorless gas. Once released, it mixes quickly with the air. Industrial processes that result in CO2 can occur at plants that produce hydrogen or ammonia from natural gas, coal, or large-scale fermentation operations. Metabolic processes are a by-product of farming. Globally, it is estimated that livestock contributes about 3.1 gigatonnes of CO2 into the atmosphere annually through belching as enteric fermentation and combustion occur in their digestive systems.
Overall, outdoor CO2 levels are not high enough to interfere with our respiratory system, but indoor CO2 levels quickly rise without proper ventilation. While carbon dioxide poisoning is rare, a high concentration of it in a confined indoor space can be toxic. Moderate to high levels of carbon dioxide can cause headaches and fatigue, and higher concentrations can produce nausea, dizziness, and vomiting.
Carbon monoxide (CO)
CO is a deadly and odorless gas that can be hazardous to your health when breathed in large quantities. CO is released when something is burned. The greatest sources of CO to outdoor air are cars, trucks, and other vehicles or machinery that burn fossil fuels. Breathing air with a high concentration of CO reduces the amount of oxygen that can be transported in the bloodstream to critical organs like the heart and brain.
Note: CO can be released from any source that burns fuel. Breathing in air with a high concentration of CO can result in carbon monoxide poisoning; symptoms may include headaches, dizziness, nausea, confusion, drowsiness, fast breathing, fast heartbeat, chest pain, vision problems, or seizures.
If you believe that you may be experiencing carbon monoxide poisoning, please leave the area immediately and dial 9-1-1 for assistance.
Indoor pollutants are easier to recognize and control. The following household items are known to produce PM, VOCs, and other harmful compounds. Take extra care when exposed to the following items, such as wearing personal protective equipment (PPE) and/or ventilating the affected area:
Cigarettes or other sources of tobacco smoke
Stoves, Heaters, fireplaces, and chimneys
Unvented space heaters
Paints and thinners
Hobby and craft supplies
Dry cleaning fluids
Cleaners and disinfectants
Building materials and furnishings
Copy machines and printers