Using an in-home HEPA purifier for one month spurs a small but significant improvement in brain function in adults age 40 and older. That’s the result of a new study we co-authored in the journal Scientific Reports.

HEPA purifiers – HEPA stands for high efficiency particulate air – remove particulate matter from the air. Exposure to particulate matter has been connected to respiratory and cardiovascular illnesses as well as neurological diseases such as Alzheimer’s and Parkinson’s. Environmental health researchers increasingly recommend that people use HEPA air purifiers in their homes to lower their exposure to particulate matter, but few studies have examined whether using them boosts mental function.

We analyzed data from a study of 119 people ages 30 to 74 living in Somerville, Massachusetts. Somerville sits along Interstate 93 and Route 28, two major highways, resulting in relatively high levels of traffic-related air pollution. This makes it an especially good location for testing the health effects of air purifiers.

We randomly assigned participants to one of two groups. One used a HEPA air purifier for one month and then a sham air purifier – which looked and acted like the real thing but did not contain the air-cleaning filter – for one month, with a monthlong break in between. The second group used the real and sham purifiers in reverse order.

After each month, participants took a test that measured different aspects of their mental capacity. The test probed people’s visual memory and motor speed skills by measuring how quickly they could draw lines between sequential numbers, and it tested executive function and mental flexibility by asking them to draw lines between alternating sequential numbers and letters.

We found that participants 40 years and older – about 42% of our sample – on average completed the section testing for mental flexibility and executive function 12% faster after using the HEPA purifier than after using the sham purifier. That was true even when we accounted for factors like differences in the amount of time participants spent indoors, with either filter, as well as how stressful they found the test.

This improvement may seem small, but it is similar to the cognitive benefits that people experience from increasing their daily exercise. While you may not experience a sudden increase in clarity from a 12% boost, preventing cognitive decline is vital for long-term well-being. Even small decreases in cognitive functioning may be associated with a higher risk of death.

Why it matters

Air pollution can negatively affect mental function after just a few hours of exposure. Studies show that air purifiers are effective at reducing particulates, but it’s unclear whether these reductions can prevent cognitive harm from ongoing pollution sources like traffic. Research has been especially lacking in people living near major sources of air pollution, such as highways.

People living near highways or major roadways are exposed to more air pollution and also experience higher rates of air pollution-related diseases. These risks aren’t encountered by all Americans equally: People of color and low-income people are more likely to live near highways or areas with heavy traffic.

Our study shows that HEPA air purifiers may offer meaningful health benefits under these circumstances.

What still isn’t known

Research shows that air pollution begins to affect cognitive function especially strongly around age 40. These effects may become increasingly prominent as people age.

HEPA air purifiers may therefore be especially beneficial for older adults. Our study did not explore this possibility, as fewer than 10 of our 119 participants were over the age of 60.

Also, our participants only used a HEPA air purifier for one month. It’s possible that longer durations of air purification may sustain or even increase the improvement in cognitive function we observed in our study.

Finally, it is unclear exactly how air purifiers improve cognition. Some studies suggest that exposure to particulate matter reduces the amount of the brain’s white matter, which helps brain cells conduct electrical signals and maintains connections between brain regions. The brain regions most harmed by air pollution are the ones that control mental flexibility and executive function, the same domains in which we saw improvements in our study.

We plan to study whether reducing particulate matter by using air purifiers is indeed protecting the brain’s white matter, and whether it could reverse some cognitive decline. We will explore that possibility by studying how levels of molecules called metabolites, which cells produce as they do their jobs, change in response to breathing polluted air and air cleaned by a HEPA filter.

The Research Brief is a short take on interesting academic work.

Nicholas Pellegrino and Doug Brugge received funding from the National Institute of Environmental Health Sciences under Grant ID: R01 ES030289

Doug Brugge receives funding from NIH.

Misha Eliasziw receives funding from NIH.

Once seen as often dry and sometimes intimidating, personal finance advice is a far cry from what it was in your grandparents’ day.

It’s not just the array of new online tools, from banking apps to exotic new investing options, such as cryptocurrency. Social media has created a platform for “finfluencers” – nonprofessional personal finance influencers who have become an increasingly common source of advice for young people, whether it’s accurate or not.

While most Americans over 64 say they turn to professional financial planners for guidance, a 2025 Gallup poll found that 42% of 18- to 29-year-olds seek financial advice on social media. That’s almost double the share among those ages 30 to 49. Many finfluencers have no formal financial credentials. Instead, their credibility is largely built on their social media followings, engagement metrics and relatability.

There’s also another generational shift afoot: Personal finance is increasingly bound up with political and social issues. Young adults are attempting to navigate a precarious economy – and the finfluencers who try to court them often launch critiques at the institutions and policies that they say created these conditions.

This advice ranges from risky trading-centric approaches to holistic financial practices. But a common thread is their positioning against traditional financial advice.

As a scholar who studies how the digital economy is affecting young adults’ well-being, I argue that Americans who still get their financial advice from more conventional sources – as well as the professional adviser class – need to understand there’s been a sea change in how young people understand money. And the legions of online followers need a better grasp of the risks involved.

Personal finance goes political

“Hey, I’m Rachel and I’m not paying my federal income taxes this year,” begins a TikTok video of an attorney who claims she’s skipping out on her US$8,800 tax bill for political reasons.

Rachel Cohen’s videos have racked up millions of views so far this year. Her video series details her reasons for refusal, specifically citing her disagreement with federal immigration policy and the “military-industrial complex.” On April 15, 2026, Cohen updated her viewers – some of whom had threatened to report her to the IRS – that she filed her return. But instead of paying the amount due, she’s parking the money in a high-yield savings account. Her sign-off: “Stay tuned and find out if I get arrested!”

Cohen’s not alone in her public protest. Millions of viewers have watched “tax resistance” or “tax strike” videos on TikTok that offer advice on how to not pay taxes and walk viewers through the potential consequences they might face.

Although my research suggests most of the tax-protest content on TikTok comes from left-leaning users, it draws influencers across the political spectrum. Examples include dissenters citing anti-war sentiments or disapproval of the government’s handling of the Epstein files.

Other personalities are encouraging their followers to treat their finances as a broader political statement. In some cases, these videos issue a call to action.

Vivian Tu, better known by her followers as “Your Rich BFF,” explains why the price of raspberries has gone up, citing a variety of foreign and domestic policy decisions: the war in Iran, tariffs and a shortage of migrant farmworkers. “If this video made you mad,” she says, “share it with a friend and contact a legislator.”

Tori Dunlap, author of “Financial Feminist,” tells her 2.2 million followers on Instagram: “If you’re freaking out about the world right now, GET RICH. That is your best form of protest is to get financially stable.”

However, Dunlap isn’t peddling get-rich-quick schemes. Much of her advice is run-of-the-mill personal finance tips – such as improving your credit score, paying down debt or automating savings contributions.

Political personal finance content has also extended beyond protests into things such as tracking the financial integrity of members of Congress or avoiding investments that could fund things such as private prisons.

Follow the money

These examples underscore how people’s financial lives are bound up with their values. And finfluencers appeal to their most politically charged beliefs to shape their financial decisions – even if they aren’t the best choices for their bank accounts.

One example is conflicts of interest. What many followers may not be fully aware of is that most finfluencers are incentivized to make highly performative content to monetize their accounts. This funding can come through either sponsored content – often from credit card and fintech companies – or through their own materials and “masterclasses.”

Moreover, full transparency is not a given. Although TikTok and Instagram have “paid promotion” designations for sponsored content, it’s not always so easy to identify potential conflicts of interest.

Crypto promoters, for example, routinely fail to disclose their sponsorships – and it’s common for them to boost coins they have a vested interest in.

As Americans’ distrust in financial institutions and regulators grows, many are willing to follow advice that falls into gray areas of oversight. When personal finance tips resonate with a viewers’ values, everyday financial decision-making can become colored with politics and nonconformist sentiments.

Advice, please!

Not everyone turns to finfluencers. Many take advice from anonymous strangers on forums such as Reddit.

The r/personalfinance subreddit alone has 2.8 million weekly visitors who post, respond and read questions posed and answered by everyday people. This is only one of 189 finance-related subreddits my colleagues and I compiled in our recent report.

Unlike finfluencers, Reddit users typically trade tips and opinion in plain text and occasional memes. Users of these forums are rarely monetized. It’s also demand-driven advice – people who post on these forums get to ask questions that directly address their personal financial issues. Credibility is earned though community “upvotes” and endorsements. Rather than one opinion, they can get a variety.

But similar to finfluencers, there’s an anti-institutional sentiment that privileges peer-to-peer learning over credentialed expertise. For example, users on the Bitcoin subreddit harshly criticize the contemporary financial system and advocate for digital currency over conventional forms of money.

Others take aim at the excesses of consumer culture, as seen on the forums for anti-consumption and frugal and simple living.

In this environment, financial education is rarely neutral – it’s deeply intertwined with people’s personal and political lives. As finfluencer Ellyce Fulmore puts it: “The barriers you face, your personal experience, the systems that do or don’t work for you … personal, personal, personal, personal!”

Maximilian Brichta does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.