The Sacramento region is making dramatic gains in improving its historically poor air-quality levels, with the amount of dangerous particulate matter declining over the past decade.
The results come by way of the American Lung Association’s 2016 State of the Air study, a yearly report card on air quality across the country. It shows that levels of both ozone and particulate matter pollution have fallen since the early 2000s, said Bonnie Holmes-Gen, policy director for the American Lung Association of California.
The region has struggled with air quality because the bowl-shaped Central Valley collects particulate matter, while ozone emissions are spurred by the region’s intense heat.
The most significant reductions involve particulate matter, with the Sacramento region seeing a 76 percent drop in the pollutant since 2004. That year saw 25 unhealthy days of particulate matter pollution, while 2015 had only six such days, the report found.
Pollution involving particulate matter weighing 2.5 micrograms or less – known as PM 2.5 – is a key indicator of a region’s air quality. Such small particles present a health risk because they can travel deep into the lungs. Exposure to PM 2.5 has been linked to increased risks of heart disease, lung cancer and asthma attacks. Particulate matter usually emanates as fine soot from fossil-fuel-powered vehicles and agricultural equipment such as tractors.
“We attribute the marked improvement to a combination of the state’s emissions standards that ratchet down pollution from vehicles and fuels,” Holmes-Gen said.
She said the decline came after the California Air Resources Board required filters be installed on diesel trucks and the use of new, less polluting diesel truck fleets as well as cleaner fuel regulations. Wood smoke controls have also made a big difference in cutting down short spikes in PM 2.5 in the winter, when such pollution reaches its worst levels, Holmes-Gen said.
“As new diesel trucks enter the fleet, they are over 85 percent cleaner than the trucks they replace, resulting in improved PM 2.5 air quality throughout the state,” said Melanie Turner, an Air Resources Board spokeswoman.
Despite the improvements, the seven U.S. urban areas with the worst year-round particulate pollution levels in 2015 were in California, with Bakersfield topping the list, the American Lung Association report said. Fresno-Madera ranked third, while Modesto-Merced tied with the Bay Area for sixth.
The board estimates that 9,000 people die prematurely in California each year from exposure to particulate matter. High air-pollution levels are a health risk for roughly 150,000 adults and 52,000 children in the Sacramento metropolitan area diagnosed with asthma, according to the American Lung Association report.
High ozone levels, which are aggravated by summer heat, continue to plague the Sacramento region, which had the sixth-worst ozone readings in the country in 2015, according to the report.
Still, ozone levels have dropped locally. Last year saw 41 days when ozone in the region exceeded the U.S. Environmental Protection Agency’s eight-hour standard, compared with 89 days in 2000, when the ozone standard was less stringent.
Ozone levels were higher in foothill regions such as El Dorado County, where pollution often gets trapped at higher elevations.
Exposure to ground-level ozone, which forms when vehicle pollutants react with sunlight, can spur respiratory problems. Ozone found in the upper atmosphere, however, shields people from ultraviolet radiation.
The lung association report found that climate change may undo some air-quality gains because higher temperatures generate higher ozone levels.
The annual average temperature in the Sacramento region has risen by 0.2 degrees Fahrenheit each decade since 1950, according to the National Climatic Data Center.
“We expect climate change to slow clean-air progress in our region, and that’s why we’re working so hard to cut greenhouse gases and ‘super pollutants’ like black carbon that accelerate climate change,” Holmes-Gen said.