Summer is coming. It’s the season of barbecues, canoes, lawnmowers, in-line skates, swimming and sunning. It is also the season where weather forecasters stop giving us the wind chill factor and start giving us the air quality index. What is the air quality index? What causes the air quality to decline on some days in the summer? What does it mean to us?
The air quality index in most areas is based on levels of common air pollutants, typically sulfur dioxide, ozone, nitrogen dioxide, total reduced sulfur compounds, carbon monoxide and fine particulate matter.
Sulfur dioxide comes mostly from smelters and from electricity generation. It can cause breathing problems and respiratory illnesses.
Ozone in the ozone layer is a good thing, but at ground surface it is a major component of smog. Ozone is not emitted by any industries, rather it forms from a reaction between nitrogen oxides and volatile organic compounds (often solvents). Ozone irritates the respiratory tract and eyes.
Nitrogen dioxide comes mostly from emissions from vehicles.
Reduced sulfur compounds are compounds that create a rotten egg or cabbage smell. They come mostly from the pulp and paper or steel industries. These compounds are not considered a health hazard but their strong odour gets them into the air quality index.
Carbon monoxide is an odourless poisonous gas that is produced through the burning of fossil fuels. Most of the carbon monoxide in the atmosphere comes from vehicles.
Particulate matter includes aerosols, smoke, fumes, dust, ash and pollen. Most particulate matter in the atmosphere is from combustion (vehicles, power generation and other burning).
In general, people with asthma or chronic heart or lung disease are more sensitive to poor air quality. Particulate matter can have serious health effects and causes hospitalization and even death in sensitive people (asthma, heart or lung disease, children, the elderly).
So why is all this worse in the summer time? There are two reasons.
One is the reaction that forms ozone takes place only in the presence of sunlight. The more sunlight, the more ozone is formed. And there is just more sunshine in the summer.
The other reason is that stagnant air masses are more likely to develop in summer.
Contaminants produced in dense population centres hang over those centres rather than being blown away.
So what can we do to make the air we breathe better? Many of the impacts come from vehicles, so driving better-tuned cars or driving less, car-pooling and avoiding the use of gas-powered lawn mowers can all help.
Electricity generation is another culprit, so the less electricity we use, the less they have to generate, which means less air pollution.
– Sophia Dore is an environmental scientist with Conestoga-Rovers & Associates. Andrew Laursen is an assistant professor at Ryerson University; firstname.lastname@example.org.