Despite their invisibly small size, ultrafine particles have become a massive concern for air pollution experts. These tiny pollutants 鈥� typically spread through wildfire smoke, vehicle exhaust, industrial emissions and airplane fumes 鈥� can bypass some of the body鈥檚 built-in defenses, carrying toxins to every organ or burrowing deep in the lungs.听听
New research from the 天美影视传媒 found that those effects aren鈥檛 felt equitably in Seattle. The most comprehensive study yet of long-term ultrafine particle exposure found that concentrations of this tiny pollutant reflect the city鈥檚 decades-old racial and economic divides. 听
The study, 听in Environmental Health Perspectives, also found that racial and socioeconomic disparities in ultrafine particle exposure are larger than those observed in more commonly studied pollutants, like fine particles (PM 2.5) and nitrogen dioxide (NO2).听
The study used mobile monitoring 鈥� a car loaded with air pollution sensors driving around the city for the better part of a year 鈥� to examine long-term average levels of four pollutants: soot (or black carbon), fine particles (PM 2.5), nitrogen dioxide (NO2) and ultrafine particles. Researchers found the highest concentrations of all four pollutants on census blocks with median household incomes under $20,000 and those with proportionately larger Black populations. 听
Disparities in concentrations of ultrafine particles 鈥� which are less than 0.1 micron in diameter, or 700 times thinner than the width of a single human hair 鈥� were especially stark. Blocks with median incomes under $20,000 had long-term UFP concentrations 40% higher than average. Blocks where median incomes are over $110,000, meanwhile, saw UFP concentrations 16% lower than average.听听
鈥淲e found greater disparities with this pollutant of emerging interest, a pollutant that hasn鈥檛 been well-characterized. That鈥檚 very interesting,” said senior author , a UW professor in the Department of Environmental and Occupational Health Sciences. 鈥淥ur work has shown the highest ultrafine particle concentrations are north of the airport and below common aircraft landing paths, downtown, and south of downtown where there are port and other industrial activities.”听
The study also found that modern-day air pollution disparities mirror Seattle鈥檚 history of redlining, the racist practice that denied racial minorities and low-income residents access to bank loans, homeownership and other wealth-building opportunities in more 鈥渄esirable鈥� areas. The practice shaped American cities throughout the early 20th century, building a foundation of segregation and environmental racism.听
Today, neighborhoods once classified as 鈥渉azardous鈥� are still exposed to higher concentrations of pollution than those once labeled 鈥渄esirable,鈥� the study found. This was true for all sizes of particles. The spatial disparities were largest, however, in Seattle neighborhoods that received no label because they were once considered industrial areas.听
In those previously industrial areas, ultrafine particle concentrations were 49% above average.听听
鈥淭hese results are important because air pollution exposure has been shown to lead to detrimental health effects, and these health effects disproportionately impact racialized and low-income communities,鈥� said , the study鈥檚 lead author, who graduated from the UW in 2022 with a degree in industrial and systems engineering. 鈥淣otably, air pollution is just one factor, and there are plenty of other examples of how systemic racism is detrimental to people’s health and well-being.鈥�听
Bramble said the results didn鈥檛 surprise her. She was raised in Tacoma, in a neighborhood near Interstate 5, where the constant crush of cars and diesel trucks spewed pollution into the air. And as a student journalist at the UW, she researched the relationship between redlining, green spaces, heat and air pollution.听听
鈥淚n the case of air pollution exposures, these policies affect the health of real people. I think at a time where the teaching of systemic racism is a controversial topic in this country, being ignorant is not going to reduce the number of children who suffer from asthma due to air pollution,鈥� Bramble said. 鈥淚nstead, I hope we can have conversations about how past policies affect us today, to drive efforts toward a healthier, sustainable society.鈥�听
Bramble proposed and carried out this study for the grant program, which provides National Institute of Environmental Health Sciences funding and mentorship to undergraduates from underrepresented backgrounds to pursue research. She joined the program in June 2020 under Sheppard鈥檚 mentorship.听听
Other UW authors are Magali Blanco, Annie Doubleday and Amanda Gassett of the Department of Environmental and Occupational Health Sciences, Anjum Hajat of the Department of Epidemiology and Julian Marshall of the Department of Civil and Environmental Engineering.听听
For more information, contact Sheppard at sheppard@uw.edu.听