Let’s Talk Science! Technology behind monitoring fine particle pollution

By Brook Beeler, environmental educator, Office of Communication and Education

Why do we monitor air quality in Washington state? Why, it’s a little thing called the Clean Air Act. We have an extensive network of monitors across the state to help us keep tabs on the seven air pollutants outlined by the federal Environmental Protection Agency. These standards for carbon monoxide, nitrogen dioxide, sulfur dioxide, lead, fine particles, larger particles, and ozone are set to protect health.

Unhealthy air is a big problem for public health. A mountain of scientific evidence has shown that fine particle pollution aggravates and causes heart and lung disease and can even result in death in some instances. While fine particle pollution can result in serious health problems for anyone, the people most sensitive to air pollution include:

• Infants and children
• Older adults (those 65 and older)
• People with lung and heart disease, stroke, diabetes, or those with a current respiratory infection.

Extensive network monitors particle pollution

Our air monitoring network is large, with more than 60 monitoring stations across the state. Because particle pollution represents the single biggest air pollution health threat, the vast majority of our network monitors measure those fine particles. Other pollutants, such as ozone, are also measured, but our main focus is fine particles. The large number of monitors that we are able to operate across the state is primarily due to an investment that we’ve made into a cost-effective, accurate surrogate for measuring fine particles known as nephelometers.

Yakama Nation station operator Terry Ganuelas services theYakama Nation station operator Terry Ganuelas services the nephelometer (the cream-colored instrument) at Toppenish.

The national standard for measuring particle pollution is a labor-intensive and operationally expensive process that uses filters. A sample of air is run through a filter with a pump. After sampling, the filter is collected and sent to a laboratory for analysis. This can take weeks or even months for the lab to analyze the filter and determine what pollution levels were like on the day the sample was run.

In contrast, the vast majority of our near “real time” monitoring data comes from an instrument that actually measures visibility, called a nephelometer. Nephelometers measure the amount of light that bounces off fine particles in units called back scatter (bscat). Generally, the less light that “scatters,” the cleaner the air.

“We have found that in most areas of Washington state, our nephelometers report bscat levels that closely track fine particle concentrations,” said Sean Lundblad, quality assurance specialist. In other words, when bscat is high fine particle pollution is high. When particle pollution is high the air is unhealthy.

Low-tech solution to provide real time data

In the Pacific Northwest, the types of particles in our air allow the nephelometer to work well. Over time, we have tracked monitoring trends and we have been able to correlate the nephelometer data to deliver near real-time air quality information to the public.

Technology for monitoring air is changing. Filter-based monitor sampling is labor intensive and operationally expensive even though the instruments are not necessarily very costly. More importantly, filter-based sampling provided no information to the public about current air pollution to help people protect their health. Newer monitors are equipped with digital outputs so the data can be polled, stored in central databases, and distributed to public websites in near real time. Ecology and its partners have purchased several of these newer monitors. However, these instruments are still very expensive. Therefore, we continue to rely primarily on our nephelometers to provide data on air pollution levels.

“The benefits of technology can’t be overstated,” Lundblad said. “The use of cheaper, near real time monitors has allowed us to operate a much larger network than was once possible given the same number of station operators. And, because nephelometers are easier to maintain, our operators don’t need to visit the monitoring sites as often so their time is freed up to do other important air quality work.”

Our monitoring network is the best of both worlds. In order to save tax-payer dollars we employ nephelometers in areas that are generally low in pollution. They are inexpensive and allow us to directly distribute the data to websites in near real time.

In a world where technology is rapidly changing how we do our work, sometimes the best technology is still the simplest one.

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