Low-cost sensors can point to solutions for world's most polluted cities

In the megacity of Dhaka, Bangladesh, the air quality on some days can get downright dangerous. Levels of PM2.5, fine particulate matter linked to heart, lung and cognitive issues, often exceed safe health standards. 

"In Bangladesh, we have a national standard, it's about 65 micrograms per cubic metre [µg/m3] for 24 hours," said Riaz Hossain Khan, assistant scientist at BRAC University in Dhaka. But during the dry season, it's much worse.

"If you measure something during December or January, these months, you'll find close to 250 or 300." 

Experts say that's resulting in kids struggling to breathe on smoggy days, and more middle-aged people developing cough-variant asthma, which can be persistent and chronic. 

While the daily concentrations are bad, the picture for the whole year is no better. Bangladesh topped recent global rankings by IQAir, an air quality technology company, for the highest annual average concentrations of PM2.5, at 79.9 µg/m3. The World Health Organization's guidelines recommends five µg/m3. 

Of the top 100 cities in the rankings by IQAir, all but one of them are in Asia, with 83 of them in India alone. (Canada, with its record breaking wildfire season, jumped up in the same rankings of the risky pollutant.)

Experts say it highlights a need not just for pollution reduction measures — but for more affordable monitoring and measurement tools to figure out what's causing the problem in the first place. 

"You can't make an informed policy decision about air quality without having data," says Jill Baumgartner, who studies air quality and health at McGill University and has worked in low- to middle-income nations.

"The vast majority of countries  — that are some of the most polluted places — don't have anything close to what we have in the city of Montreal." 

Typically, ground-based air quality monitoring can use a variety of methods, including: 

The more expensive monitoring tends to be used by government regulators, costing "between $20,000 and $30,000 US for each monitoring station," explains Glory Dolphin Hammes, North American CEO of IQAir. Lower-cost sensors, by comparison, can be around $500. 

Hammes's company sells air quality monitoring products and manages a platform using regulatory and low-cost sensors around the world. The data gets verified and feeds into real-time online reports as well as those yearly pollution rankings. Cheaper sensors, she says, provide broader coverage and give people actionable information. 

"They are given the power of choice to mask up or to do other means to mitigate the air quality that they're breathing," Hammes told CBC News from Los Angeles. 

Progress is also being made on bringing sensors up to a higher standard, according to Olorunfemi Adetona, who researches pollutant exposure and health effects at Ohio State University.