Despite their invisibly small size, ultrafine particles have become a massive concern for air pollution experts. These tiny pollutants — typically spread through wildfire smoke, vehicle exhaust, industrial emissions and airplane fumes — can bypass some of the body’s built-in defenses, carrying toxins to every organ or burrowing deep in the lungs.����

New research from the ����Ӱ�Ӵ�ý found that those effects aren’t 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’s decades-old racial and economic divides. ��

The study, ��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).��

The study used mobile monitoring — a car loaded with air pollution sensors driving around the city for the better part of a year — 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. ��

Disparities in concentrations of ultrafine particles — which are less than 0.1 micron in diameter, or 700 times thinner than the width of a single human hair — 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.����

“We found greater disparities with this pollutant of emerging interest, a pollutant that hasn’t been well-characterized. That’s very interesting,” said senior author , a UW professor in the Department of Environmental and Occupational Health Sciences. “Our 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.”��

The study also found that modern-day air pollution disparities mirror Seattle’s 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 “desirable” areas. The practice shaped American cities throughout the early 20th century, building a foundation of segregation and environmental racism.��

Today, neighborhoods once classified as “hazardous” are still exposed to higher concentrations of pollution than those once labeled “desirable,” 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.��

In those previously industrial areas, ultrafine particle concentrations were 49% above average.����

“These 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,” said , the study’s lead author, who graduated from the UW in 2022 with a degree in industrial and systems engineering. “Notably, 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.”��

Bramble said the results didn’t 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.����

“In 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,” Bramble said. “Instead, I hope we can have conversations about how past policies affect us today, to drive efforts toward a healthier, sustainable society.”��

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’s mentorship.����

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.����

For more information, contact Sheppard at sheppard@uw.edu.��

Using data from two large, long-running study projects in the Puget Sound region — one that began in the late 1970s measuring air pollution and another on risk factors for dementia that began in 1994 — ����Ӱ�Ӵ�ý researchers identified a link between air pollution and dementia.

In the , a small increase in the levels of fine particle pollution ( or particulate matter 2.5 micrometers or smaller) averaged over a decade at specific addresses in the Seattle area was associated with a greater risk of dementia for people living at those addresses.

“We found that an increase of 1 microgram per cubic meter of exposure corresponded to a 16% greater hazard of all-cause dementia. There was a similar association for Alzheimer’s-type dementia,” said lead author , who conducted the research as a doctoral student in the UW Department of Environmental & Occupational Health Sciences.

The study, in the journal Environmental Health Perspectives, looked at more than 4,000 Seattle-area residents enrolled in the run by Kaiser Permanente Washington Health Research Institute in collaboration with UW. Of those residents, the researchers identified more than 1,000 people who had been diagnosed with dementia at some point since the ACT Study began in 1994.

“The ACT Study is committed to advancing dementia research by sharing its data and resources, and we’re grateful to the ACT volunteers who have devoted years of their lives to supporting our efforts, including their enthusiastic participation in this important research on air pollution,” said Dr. Eric Larson, ACT’s founding principal investigator and a senior investigator at KPWHRI.

Once a patient with dementia was identified, researchers compared the average pollution exposure of each participant leading up to the age at which the dementia patient was diagnosed. For instance, if a person was diagnosed with dementia at 72 years old, the researchers compared the pollution exposure of other participants over the decade prior to when each one reached 72. In these analyses, the researchers had to account for the different years in which these individuals were enrolled in the study, since air pollution has dropped dramatically in the decades since the ACT study began.

In their final analysis, the researchers found that just a 1 microgram per cubic meter difference between residences was associated with 16% higher incidence of dementia. To put that difference into perspective, Shaffer said, in 2019 there was approximately 1 microgram per cubic meter difference in PM2.5 pollution between Pike Street Market in downtown Seattle and the residential areas around Discovery Park.

“We know dementia develops over a long period of time. It takes years —even decades — for these pathologies to develop in the brain and so we needed to look at exposures that covered that extended period,” Shaffer said. And, because of long-running efforts by many UW faculty and others to build detailed databases of air pollution in our region, “we had the ability to estimate exposures for 40 years in this region. That is unprecedented in this research area and a unique aspect of our study.”

In addition to extensive air pollution and dementia data for the region, other study strengths included lengthy address histories and high-quality procedures for dementia diagnoses for the ACT Study participants.

“Having reliable address histories let us obtain more precise air pollution estimates for study participants,” said senior author , a UW professor of environmental and occupational health sciences and of biostatistics. “These high-quality exposures combined with ACT’s regular participant follow-up and standardized diagnostic procedures contribute to this study’s potential policy impact.”

While there are many factors such as diet, exercise and genetics associated with the increased risk of developing dementia, air pollution is now recognized to be . The new UW-led results add to this body of evidence suggesting air pollution has neurodegenerative effects and that reducing people’s exposure to air pollution could help reduce the burden of dementia.

“How we’ve understood the role of air pollution exposure on health has evolved from first thinking it was pretty much limited to respiratory problems, then that it also has cardiovascular effects, and now there’s evidence of its effects on the brain,” said Sheppard, who this year was awarded the Rohm & Haas Endowed Professorship of Public Health Sciences.

“Over an entire population, a large number of people are exposed. So, even a small change in relative risk ends up being important on a population scale,” Shaffer said. “There are some things that individuals can do, such as mask-wearing, which is becoming more normalized now because of COVID. But it is not fair to put the burden on individuals alone. These data can support further policy action on the local and national level to control sources of particulate air pollution.”

Co-authors include Magali Blanco, Joel Kaufman, Timothy Larson, Marco Carone, Adam Szpiro and Paul Crane at UW; Ge Li at the VA Puget Sound Health Care System and UW; Sara Adar at the University of Michigan; Eric Larson at the UW School of Medicine and Kaiser Permanente Washington Health Research Institute. This research was funded by multiple supporting grants from the National Institute for Environmental Health Sciences, National Institute on Aging, UW Retirement Association Aging Fellowship, the Seattle chapter of the Achievement Rewards for College Scientists Foundation and others.

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To speak with the UW researchers, contact Jake Ellison at JBE3@uw.edu or 206-713-6420.

For information related to the ACT Study and its researchers, contact Jonathan Rabinovitz at Jonathan.X.Rabinovitz@kp.org or 206-512-7356.

For nearly 50 years, a statistical omission tantamount to data falsification sat undiscovered in a critical study at the heart of regulating one of the most controversial and widely used pesticides in America.

Chlorpyrifos, an insecticide created in the late 1960s by the Dow Chemical Co., has been linked to serious health problems,��. It has been the subject of many lawsuits and banned in and . The EPA itself nearly banned the chemical, but in 2017 the Trump administration backtracked and rejected to take chlorpyrifos off the market. The EPA plans to reconsider the chemical’s use by 2022.

In February, the largest producer of chlorpyrifos, Corteva Agriscience (which owns Dow), said it would stop making the chemical because of slumping sales, not out of safety concerns. Corteva has kept up of the chemical.

So, while chlorpyrifos can still be used on some agricultural products, the chemical appears to be approaching the end of its long run.

However, ����Ӱ�Ӵ�ý researchers that decades of exposure to chlorpyrifos and all the political wrangling and lawsuits surrounding it might have been averted if a 1972 study had been adequately reviewed by the EPA, itself newly established in the early 1970s. The EPA also did not re-analyze the study data when new statistical techniques became available a few years later, the UW researchers added.

, a professor of biostatistics and environmental health in the UW School of Public Health and the study’s lead author, explained that the 1972 “” established erroneously how much of the chemical a human could be exposed to before adverse effects showed up in a body’s chemistry.

When Sheppard re-ran the study data using the same longhand statistical analysis as the original, she discovered that key data used in two other level-of-exposure tests in the same study had been left out of the central exposure question — inexplicably. Consequently, the safe exposure limit, called the “no observed adverse effect level,” that the EPA used was wrong.

As the uses for chlorpyrifos expanded in the 1970s and became approved for in-home uses in the 1980s and ’90s, the EPA set allowable human exposure levels at the one described as safe in the Coulston study — .03 mg/kg per day.

“This has huge public health implications,” said Sheppard. “This study was the basis of policy for over 15 years and because it concluded that the ‘no observed adverse effect level’ was more than twice as high as it should have been, the standard was a lot less protective than it should have been.”

In the new study, UW researchers stated: “Such an omission of valid data without justification is a form of data falsification that violates all standard codes of ethical research practice and is classified as outright research misconduct. It is tragic that an omission of valid data from the analysis of the Coulston study may have adversely impacted public health.”

Sheppard pointed out two other critical problems with this study that made its results more susceptible to producing a higher level of “safe” exposure.

In short, because of how the Coulston study was designed, investigators were not able to compare the test results of the three groups treated with different doses of chlorpyrifos within the same analysis. “This meant that their original analysis was much less powerful than it could have been if it had put all the dose groups together in one analysis,” Sheppard said.

Secondly, Sheppard points out, better statistical methods and software tools became available in the 1980s — well within the window when the EPA was using the Coulston study to set acceptable exposure limits for chlorpyrifos — and those would have shown that the study did not find a “safe” level of exposure. These ‘longitudinal data analysis’ tools allow a more direct assessment of how accumulation of the chemical would affect the body’s chemistry over time, while also being able to accommodate the poor study design.

Had the Coulston data been put through the more modern technique, as was done by the UW researchers in their new study, EPA’s reviewers would have seen that chlorpyrifos’ effect on the body’s chemistry accumulated over time and that the study had not discovered the “no observed adverse effect level” used by regulators to set safe levels of exposure.

“All kinds of approvals were allowed for uses that never should have been allowed and quite well wouldn’t have been allowed if the Coulston study authors had properly reported their results,” said Sheppard.

Why the 1972 Coulston study was not thoroughly examined even as the maturing EPA began reviewing these kinds of studies more rigorously through its inaugural 2006 Human Studies Review Board is a mystery, said co-author , emeritus professor in the UW School of Public Health’s Department of Environmental & Occupational Health Sciences.

But when the EPA formally set out to review human-subject studies like the Coulston study, the maker of chlorpyrifos (Dow) specifically removed the study from that process, said Fenske, who was a member of that initial review board.

“You can speculate why they did,” said Fenske, “but they formally asked the Human Studies Review Board not to review this study and so it was never reviewed.”

Fenske, whose decades-long work involving insecticides includes a 1990 study of chlorpyrifos residue left behind after an in-home spray treatment (finding the treatment could expose children to unsafe levels of the chemical), said that while the Coulston study could be old news now, “it is a cautionary tale that data being submitted for pesticide registration may not have undergone proper review, and that could be happening today.”

Sheppard added that “at a minimum,” studies funded by companies developing a chemical that’s under study must be opened to outside scrutiny. “I’m not sure industry should be doing these studies at all. I don’t think the fox should be guarding the hen house.”

Co-authors include Seth McGrew, who worked on the study while a graduate student in the UW Department of Environmental and Occupational Health Sciences, School of Public Health.

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For more information, contact Jake Ellison at Jbe3@UW.edu or 206-713-6420

Various reviews and international assessments have come to different conclusions about whether glyphosate leads to cancer in humans.

The research team conducted an updated meta-analysis — a comprehensive review of existing literature — and focused on the most highly exposed groups in each study. They found that the link between glyphosate and Non-Hodgkin Lymphoma is stronger than previously reported.

Their findings were published this month in the online journal .

“Our analysis focused on providing the best possible answer to the question of whether or not glyphosate is carcinogenic,” said senior author , a professor in the UW departments of Environmental & Occupational Health Sciences and Biostatistics. “As a result of this research, I am even more convinced that it is.”

By examining epidemiologic studies published between 2001 and 2018, the team determined that exposure to glyphosate may increase the risk of Non-Hodgkin Lymphoma by as much as 41 percent. The authors focused their review on epidemiological research in humans but also considered the evidence from laboratory animals.

“This research provides the most up-to-date analysis of glyphosate and its link with Non-Hodgkin Lymphoma, incorporating a 2018 study of more than 54,000 people who work as licensed pesticide applicators,” said co-author Rachel Shaffer, a UW doctoral student in the Department of Environmental & Occupational Health Sciences.

“These findings are aligned with a prior assessment from the International Agency for Research on Cancer, which classified glyphosate as a ‘probable human carcinogen’ in 2015,” Shaffer said.

Glyphosate first was introduced as an herbicide in 1974. Usage in the agricultural industry has soared, particularly since the mid-2000s when the practice of “green burndown” was introduced, in which glyphosate-based herbicides are applied to crops shortly before harvest. As a consequence, crops now are likely to have higher residues of glyphosate.

Researchers say more studies are needed to account for the effects of increased exposures from green burndown, which may not be fully captured in the existing studies reviewed in this new publication.

Co-authors include Luoping Zhang and Iemaan Rana in the Division of Environmental Health Sciences at the University of California, Berkeley, and Emanuela Taioli in the Icahn School of Medicine at Mount Sinai, New York.

Funding was provided by the National Institutes of Environmental Health Sciences award����and the������Ӱ�Ӵ�ý Retirement Association Aging Fellowship.

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For more information, contact Sheppard at 206-616-2722 or sheppard@uw.edu.