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Wednesday, 28 February, 2018

Putting Air Quality to the Test

Air pollution can have deadly consequences; in fact, it accounts for an estimated 93,000 deaths each year in low- and middle-income countries in the Americas and another 44,000 deaths in high-income countries in the region, according to the Pan American Health Organization. As serious as the problem is, many cities and countries are still not measuring air quality or are measuring it inadequately. Yet as one Costa Rican scientist explained, without a clear picture of the air pollution problem, it’s harder to develop effective policies to combat it.

Some of the larger countries in Latin America and the Caribbean already have rigorous programs in place to scientifically measure air quality, but many places in the region still fall short—perhaps because of outdated technology, lack of training, or shortage of resources.

The lack of precise measurements can make it difficult to understand the scope of the problem and take actions to tackle it, according to Jorge Herrera Murillo of the National University of Costa Rica (UNA). He serves as the university’s Deputy Dean of the School of Earth and Ocean Sciences and coordinates its environmental analysis laboratory, which provides technical support to the air monitoring network run by the Costa Rican Ministry of Health. 

“When we measure, we ascertain the seriousness of the problem,” Herrera said in an interview. But, he added, simply measuring air quality is not enough. Because the data collected will be used to guide public policy, “it’s very important for the results to be reliable,” he said. That challenge will be the focus of a technical workshop that will take place in the Costa Rican capital of San José during the first half of this year. (See box below for more details.)

Costa Rica has monitored its air quality for years, through five monitoring stations in the greater San José metropolitan area, which spans parts of four provinces and has a population of around 2.6 million people.

Until recently, Herrera explained, the system operated on manual technology. Someone had to stop by each monitoring station every day to take a sample of the air and then get it to a lab for testing; results were not available for more than a week. Now, after investing around $1.2 million in new monitoring equipment, the country is implementing a modern system that will soon allow people to check the air quality in their area online, in real time.

That doesn’t solve every problem, Herrera said. For a small country such as Costa Rica, keeping the equipment maintained and calibrated to ensure accuracy requires a serious commitment of resources. He hopes the upcoming workshop will enable Costa Rica and other countries to identify how they can develop greater technical capacity and thus be able to reduce operating costs.

The ABCs of Air Quality 

When scientists measure air quality, they typically look at six so-called “criteria air pollutants” that are known to harm human health: carbon monoxide, lead, sulfur dioxide, nitrogen dioxide, ground-level ozone, and particulate matter. 

The gases that help determine air quality are not the same as greenhouse gases, but both categories share a common source: combustion emissions, such as vehicle exhausts and emissions from electric power plants and heavy industry. In other words, steps that countries take to reduce carbon emissions in these sectors will not only reduce the greenhouse gases that contribute to climate change but will also make the air easier to breathe.

Of course, not every pollutant comes out of vehicles. Particulate matter can also include dust, volcanic  ash, plant pollen, smoke—from chimneys or cookstoves or heavy industry or farm fields—and other inhalable substances. The smaller the particle, the more easily it can become lodged in the lungs and cause serious health effects.

People with certain preexisting health conditions, adults between 50 and 75 years old, and children under 5 are especially vulnerable, as are people who cook indoors using wood- or coal-burning stoves, according to the Pan American Health Organization (PAHO). And, it says, a significant percentage of deaths in the general population from lung cancer, chronic obstructive pulmonary disease, stroke, and ischemic heart disease due to narrowing of arteries are attributable to long-term exposure to ambient air pollution.  

Scientists measure particulates in terms of their size or diameter in units of microns, also known as micrometers. Some cities or countries measure concentrations of particulates that are at least 10 microns in diameter (PM10), but others apply a stricter standard of 2.5 microns (PM2.5). By way of comparison, the average human hair is about 70 microns in diameter—nearly 30 times wider than these fine particulates, according to the U.S. Environmental Protection Agency.

Out of 43 cities in Latin America and the Caribbean with one million or more inhabitants, 56 percent measure PM10 and 37 percent measure PM2.5, according to PAHO. But scientists caution that the accuracy of those measurements could vary widely and depend strongly on the measuring instrumentation and standards used.

Measuring air quality is one area in which metrology—the science of measurement—plays a critical role. The instruments that are used need to be calibrated regularly to make sure they’re accurate, according to Jorge Koelliker Delgado, Scientific Coordinator of the Gas Group in the Metrology of Materials Directorate at Mexico’s National Metrology Center (CENAM).

To calibrate these types of equipment, scientists use special mixtures of gases that have been prepared according to strict protocols and that have known quantities, as well as aerosol generators and other measuring instruments. By passing these gases or particulate streams through the equipment, they can assess the performance of the equipment that is being tested and ensure that it will measure accurately, in line with common reference points that meet regulatory needs. That way, the same measurement of "parts per million" of carbon monoxide or other air pollutants means the same from one city or even one monitoring station to another. 

“It’s simple, really. We want to compare apples to apples and oranges to oranges,” Koelliker said in an interview. Without regular calibration, he said, it’s impossible to say whether the equipment is set properly and therefore whether a city or country is really meeting the standards set by its own laws.

The cylinders of compressed calibration gases used in this process can be expensive and cumbersome to obtain. Costa Rica currently imports them from the United States, but “that is not sustainable,” according to Herrera, who hopes the technology can be developed locally to reduce operating costs.

Koelliker believes the whole region would benefit from much more technical training in this area, adding that there is not enough awareness—even in university science programs—of the need for accurate measurement. Complicating the picture, he said, is that different jurisdictions are often involved. In Mexico, for example, it is up to local governments to operate air quality monitoring stations, and they may not always have the necessary resources.

Koelliker understands that governments have many priorities and that a technical subject like this can get overlooked with all the competing demands for funding. But for him, it all comes down to public health, and there’s nothing more basic than the air people breathe. Even though the human body is made up largely of water, he said, it depends on air to survive. “That’s the medium in which we live.”




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