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Cheaper costs, more coverage: Low-cost sensors can help with air quality | CBC News

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

“In Bangladesh we have a national standard which is around 65 micrograms per cubic meter [µg/m3] for 24 hours,” said Riaz Hossain Khan, an assistant researcher at BRAC University in Dhaka. But during the dry season it is much worse.

“If you measure something in December or January, those months, you’ll find about 250 or 300.”

Experts believe this is causing children to have difficulty breathing on smoggy days and causing more middle-aged people to develop cough-induced asthma, which can be persistent and chronic.

40 times higher than WHO guidelines

While daytime concentrations are poor, the picture is no better throughout the year. Bangladesh tops the latest global ranking by IQAir, an air quality technology company, with the highest average annual PM2.5 concentration at 79.9 µg/m3. The World Health Organization guidelines recommends five µg/m3.

From the top 100 cities in the IQAir ranking, all but one of them are in Asia, 83 of them in India alone. (Canada, with its record-breaking wildfire season, has climbed into the same ranking of hazardous pollutants.)

Experts say this highlights the need not only for measures to reduce pollution, but also for more affordable monitoring and measurement tools to find out what’s causing the problem in the first place.

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

“The vast majority of countries – which are some of the most polluted places – don’t have anything close to what we have in the city of Montreal.”

Cheaper and faster air quality measurement

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

  • Gravimetric: sampling the air and weighing the fine dust particles. These are considered the “gold standard” and are collected and analyzed, so they are slower and more expensive.

  • Optical: Shine lasers through particles and observe how light behaves to determine quantities. The advantage here is that it is cheaper and in real time.

The more expensive monitoring is typically used by government regulators and costs “between $20,000 and $30,000 for each monitoring station,” explains Glory Dolphin Hammes, North American CEO of IQAir. In comparison, less expensive sensors can cost around $500.

A McDougall Creek forest fire burns on the mountainside above homes in West Kelowna, BC on Friday, August 18, 2023.
The McDougall Creek wildfire burns on the mountainside above homes in West Kelowna, BC in August 2023 (Darryl Dyck/The Canadian Press)

Hammes’ company sells air quality monitoring products and manages a platform of regulatory and low-cost sensors around the world. The data is checked and fed in real time Online reports as well as these annual pollution rankings. Cheaper sensors, they say, offer broader coverage and provide people with actionable information.

“They have the power to choose whether they want to mask up or otherwise reduce the air quality that they breathe,” Hammes told CBC News from Los Angeles.

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Up to the gold standard

Progress is also being made in improving sensors to a higher standard, according to Olorunfemi Adetona, who researches pollution and health effects at Ohio State University.

“The Environmental Protection Agency has attempted to calibrate these instruments using the gold standard measurements,” Adetona explained. The EPA has developed methods to integrate data from low-cost sensors with that of more expensive sensors.

Vehicles move along the dusty road as air quality declines during the dry season in Dhaka, Bangladesh, February 19, 2024.
Vehicles move along the dusty road as air quality declines during the dry season in Dhaka, Bangladesh in February. (Mohammad Ponir Hossain/Reuters)

Adetona cautioned that these were not perfect comparisons and would not be used as official regulatory data, but could provide public health information.

“The Environmental Protection Agency has attempted to calibrate these instruments using the gold standard measurements,” Adetona explained. These calibrations can help “function as if you were using government monitors.”

Dhaka’s dilemma

That’s what Khan and his colleagues in Dhaka are trying to do. Initially, the city only had three government-installed air quality monitors, which he said were located too close together and at far too high an altitude.

“The entire city of Dhaka is about 306 square meters [kilometres]”Khan explained. “So there is a large portion of the area that is not covered.”

He and his team have installed dozens more as part of the global Pathways to Equitable Healthy Cities partnership. They found that the way the land was used affected air quality: higher concentrations near industrial sites, lower concentrations near more residential areas with green spaces – and times of day when the intensity varied. Source and temporal data, says Khan, are incredibly valuable for improving policy.

But Dhaka is complex, reminds Zahidul Quayyum, a colleague of Khan and an expert in health economics at BRAC University.

“You can’t clearly differentiate between some of these purely residential areas and those [others]” Quayyum told CBC News from Dhaka, explaining that the city’s urban planning is being overtaken by its growth. A network of informal industry, traffic and residential environments makes it difficult to regulate air pollution.

Smoke rises from the chimneys of brick factories on the outskirts of Dhaka, Bangladesh, March 17, 2024.
Earlier this month, smoke rose from the chimneys of brick factories on the outskirts of Dhaka. (Mohammad Ponir Hossain/Reuters)

But something has changed at least when it comes to one of the most well-known sources of air pollution: brick kilns. Many of them operate informally and illegally.

“They made some policy changes that drove the brick kilns out of the city,” Quayyum noted. But politics and economics don’t always get along, he says, and when asked whether data leads to better public health policy, Quayyum is practical.

“Yes, to a certain extent. But more needs to be done.”

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