While conversations surrounding air pollution have largely centred on outdoor pollution, indoor air pollution also poses a threat to public health.

A study led by Douglas Collins, former postdoctoral fellow in the Abatt Group in the U of T Department of Chemistry, explored the effects of nitrous acid on indoor air quality.

In an email interview with The Varsity, Collins, now an Assistant Professor at Bucknell University, identified nitrogen dioxide, ozone, and particulate matter as examples of indoor pollutants.

To simulate nitrous acid chemistry in a realistic environment, Collins and his peers brought lab instruments to an inhabited home and set up experiments to observe the effects of combustion, a known source of nitrous acid and nitrogen oxide.

They compared their measurements to a computational model designed to approximate indoor concentrations of nitrous acid combustion based on a variety of factors.

This is one of the first studies on the effects of nitrous acid composition on indoor environemnts to take place in an inhabited house, as previous studies used lab environments to measure nitrous acid concentrations.

Collins explained that while nitrous acid is one of the lesser known pollutants, it is nevertheless one of the most hazardous. Its reactive nature allows it to act “as a source for other chemically reactive compounds that shape the chemical composition of indoor air.” He added that nitrous acid can also “chemically react with tissues in the respiratory tract and cause adverse health effects.”

Other indoor pollutants include some organic chemicals widely used in plastics, flame retardants, and other common household products.

Indoor air pollution is particularly hazardous to humans because the concentration of air pollutants in enclosed environments can quickly accumulate, and lead to severe health problems like respiratory diseases and cancer.

To make matters worse, many homes now lack sufficient ventilation for air circulation for pollutants to escape, due to new energy-saving regulations.

Other sources of indoor air pollution include asbestos, common in older buildings but universally banned in recent years, tobacco smoke, which clings to clothes and furniture, and chemicals released from space heaters, stoves, and certain cleaning products.

There are several types of indoor air quality meters on the market designed to measure the concentrations of nitrous acid and other air pollutants.

“If you’re interested in monitoring your indoor air, be sure to do your research on which mode is best for your purposes — not all sensors are created equal,” Collins wrote.

Popular air quality sensors include volatile organic compound (VOC) sensors which can pick up organic compounds such as formaldehyde and ketones, carbon dioxide meters, and combined sensors, which can measure a variety of particulate matter, VOCs, and gases. Professional labs are used for exhaustive air quality screening.

A major problem with indoor air pollution is that hazardous pollutants are in nearly all household products and are emitted through common tasks, such as cooking.

However, there are ways to improve air quality, including opening windows to improve ventilation and using ventilation fans in the house.

“The fan above the kitchen stove can be an effective way to remove polluted air from your home, especially when cooking, which is one example of an activity that makes lots of pollutants including HONO [nitrous acid] if you have a gas stove,” Collins wrote. “Refraining from using scented candles or incense is another way to stop pollutants from being introduced to your indoor air. Purchasing a good-quality HEPA air cleaner is also a good idea.”

The National Human Activity Pattern Survey reports Canadians spend almost 90 per cent of their time indoors. It is therefore imperative that we understand the effects of indoor pollution and find ways to improve indoor air quality.