Air pollution is increasingly recognized as a potential risk factor for dementia. This guide reviews the current state of the science, key findings from recent research, and considerations for building owners and facility managers when evaluating indoor air filtration and occupant well-being.
READ: Preventing Cognitive Decline with Home Air Filters
The evidence linking air pollution to dementia has grown substantially in recent years. While research is ongoing, a growing number of studies suggest a meaningful association. For building owners, facility managers, and others responsible for indoor air quality, these findings may have important implications.
A July 2025 meta-analysis published in The Lancet Planetary Health reviewed 32 studies covering data from approximately 29 million people across multiple countries [1]. The analysis found that for every 10-microgram-per-cubic-meter increase in PM2.5 exposure, the relative dementia risk increased by 17 percent. Similarly, each 10 microgram per cubic meter increase in nitrogen dioxide (NO₂) exposure was associated with a 3 percent increase in risk [1].
These effect sizes are notable, particularly given the scale and scope of the underlying data. The meta-analysis is among the largest conducted on this topic, drawing on decades of longitudinal health records from the late 1980s through the early 2020s.
A separate 2025 study published in Nature Aging applied a Burden of Proof meta-analytic framework to 28 longitudinal cohort studies. It is estimated that long-term exposure to PM2.5 is associated with at least a 14 percent increase in dementia risk [2].
The Scale of the Problem
The State of Global Air 2025 report found air pollution contributed to 7.9 million deaths worldwide in 2023 [3]. Long-term PM2.5 exposure alone accounted for more than 4.9 million of those deaths [3]. The World Health Organization reports PM2.5 shortens the average human lifespan by 2.3 years globally [4].
In February 2026, a study covering nearly 28 million older Americans found long-term fine particle pollution exposure raised the likelihood of developing Alzheimer’s disease. Researchers noted the connection appeared to stem largely from pollution’s direct effects on the brain, not through related conditions like hypertension or depression [5].
PM2.5 is not a future problem. The damage is happening now, in real time, inside the lungs and brains of building occupants everywhere.
How Air Pollution Reaches the Brain
Understanding the mechanism matters because the pathway from polluted air to cognitive decline is more direct than most people assume.
When inhaled, PM2.5 and PM1 particles travel to the deepest areas of the lungs. A significant portion passes through the cell membranes of the alveoli, enters the bloodstream, damages the inner walls of arteries, penetrates cardiovascular tissue, and spreads to organs, including the brain [6].
However, there is a second pathway. Research has shown fine particles and gaseous pollutants enter the brain through the nose, travel along olfactory pathways to the hippocampus (the brain’s memory center), and promote the buildup of toxic amyloid and tau proteins [1], which are among the signature markers of Alzheimer’s disease.
Additional research points to white matter damage and myelin disruption as another mechanism through which pollution degrades cognitive function [1].
Why Indoor Air Quality Affects Your Brain Health
People spend up to 90 percent of their lives indoors [7]. Indoor air concentrations run up to 50 times higher than outdoor levels in poorly ventilated or unfiltered buildings [7]. These two facts, taken together, mean indoor air quality is the primary exposure pathway for most people.
A joint study by Harvard University and Syracuse University found employees in green, well-ventilated environments performed around 60 percent better on cognitive tests than those in standard office environments. When ventilation rates doubled, cognitive performance increased by more than 100 percent [8].
A separate study showed participants scored 15 percent worse on cognitive tests at moderate CO2 levels and 50 percent worse at high CO2 levels [8].
The brain depends on a steady supply of oxygen, and indoor air quality can play a role in supporting that process. When air is polluted, stagnant, or particle-laden, some studies suggest cognitive performance may be affected. Over longer periods, ongoing exposure to poor air quality has been associated in research with increased risk of cognitive decline, including dementia.
Why Standard Filters Are Not Enough
Most commercial HVAC systems run filters selected for dust and pollen. Air filters rated between MERV 8 and MERV 11 do a reasonable job with large particles. They do almost nothing against PM2.5 and PM1, the fractions most strongly linked to brain damage and dementia.
A MERV 13/13A filter continuously captures approximately 69 percent of PM2.5. A MERV 16/16A captures 96 percent. HEPA filters reach 99.97 percent efficiency down to 0.3 microns [9]. For buildings serious about protecting occupant health, MERV 13/13A is the minimum starting point, not the ceiling.
And particle filtration is only half the equation. NO2, the second pollutant now confirmed as a dementia risk factor, is a gas. So are the volatile organic compounds (VOCs) released by traffic, industrial processes, cleaning products, and building materials. Standard particle filters, including HEPA, do nothing to remove gases from the air stream [10].
Molecular filtration using activated carbon or activated alumina is the technology designed to address gaseous contaminants. Activated carbon adsorbs gas-phase molecules onto a matrix of microscopic pores with extremely high surface area [11]. Camfil’s molecular filtration products remove NO2, ozone, VOCs, and other gaseous pollutants from HVAC air streams at commercial and institutional scale.
Improving Indoor Air Quality: Practical Steps for Building Owners
The research increasingly points to a consistent theme: indoor air quality may play an important role in long-term brain health for building occupants. For organizations focused on occupant well-being, this is an area worth careful consideration.
Fortunately, Camfil’s team of air filtration experts has developed a practical, step-by-step approach to help you get started.
Start with an expert assessment.
Before making system-wide changes, it can be valuable to consult with an indoor air quality specialist. A qualified expert can evaluate your building’s current HVAC systems, air filters, ventilation rates, and pollutant sources, and help prioritize interventions based on your specific layout, occupancy patterns, and local outdoor air conditions to help ensure that upgrades are both effective and cost-efficient.
Audit your current filtration.
Pull a filter from every air handler and read the MERV rating on the label. If anything below MERV 13 sits in the housing, replace the filters. A MERV 13/13A-rated filter (tested under ASHRAE Standard 52.2 with Appendix J) maintains its rated efficiency throughout its full service life, not only when new [12].
Assess your gaseous contamination risk.
If your building sits near highways, industrial zones, or in an urban area with elevated NO2 and PM2.5 readings, particle filtration alone is insufficient. Molecular filtration should be part of the HVAC strategy. Camfil’s CamCarb product line provides activated carbon and activated alumina media in configurations ranging from panel filters (CamCarb PM) to cylindrical systems (CamCarb XG) for commercial and industrial HVAC applications [13] [14].
Deploy standalone air purifiers in high-occupancy zones.
Classrooms, patient rooms, conference areas, and open office floors benefit from supplemental HEPA purification. The CamCleaner CC500 runs a pharmaceutical-grade 99.99% HEPA filter and covers up to 13,000 cubic feet per unit [15].
Monitor air quality continuously.
You do not manage what you do not measure. PM2.5 and CO2 sensors placed in occupied zones give facility teams the data they need to respond before air quality degrades. There is a wide range of performance quality in sensors of this kind, so research before purchasing is advised.
Increase ventilation rates where possible.
Higher outdoor air exchange dilutes both particulate and gaseous contaminants. Balance this with filtration to avoid simply importing more outdoor pollution.
Schools and Healthcare: The Highest Stakes
Children and patients are the most vulnerable populations. Their developing or compromised systems absorb more pollution per unit of body weight and have fewer defenses against the damage.
ASHRAE recommends a minimum of MERV 13 for school HVAC systems [17]. The EPA has published specific guidance on indoor air quality in schools and commercial buildings during elevated pollution events [18]. Schools running standalone HEPA purifiers in classrooms during poor air quality events have documented 50 to 70 percent reductions in PM2.5 levels [17].
For hospitals and senior care facilities, the equation is even more direct. Patients with cardiovascular disease, respiratory conditions, or early-stage cognitive decline face amplified risk from PM2.5 and gaseous pollutant exposure. Healthcare facilities already running high-efficiency particulate filtration need to evaluate whether their systems also address the gaseous component, specifically NO2 and VOCs, the pollutants linked to dementia by recent peer-reviewed research [1] [2].
Meeting federal clean air standards would have prevented an estimated 29,808 hospital admissions and emergency room visits throughout California alone, with nearly three-quarters attributable to PM2.5 reductions [19].
The Cost of Doing Nothing
The healthcare costs associated with air pollution exposure are substantial. Less visible, however, are the potential long-term effects on cognitive function among people who spend extended time indoors.
Research suggests that poorer indoor air quality may be associated with reductions in cognitive performance. In workplace settings, even modest declines could influence decision-making, work quality, and overall productivity over time [8]. Across years, these effects may accumulate in ways that are meaningful when compared with the cost of improving filtration and ventilation.
In schools, these impacts may relate to learning outcomes. In healthcare environments, they may influence recovery conditions. In senior living settings, they may intersect with populations already more vulnerable to cognitive decline.
Effective air filtration technologies are widely available, and the body of peer-reviewed research continues to grow. For building owners and operators, the question is less about whether solutions exist and more about how and when to incorporate them into a broader indoor air quality strategy.
About Camfil
The Camfil Group is headquartered in Stockholm, Sweden, and has 29 manufacturing sites, six R&D centers, local sales offices in 35+ countries, and 5,700 employees and growing. We proudly serve and support customers in a wide variety of industries and communities across the world. To discover how Camfil USA can help you protect people, processes, and the environment, visit us at www.camfil.us.
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Footnotes
[1] Khreis, H., et al. “Long-term air pollution exposure and incident dementia: a systematic review and meta-analysis.” The Lancet Planetary Health, July 2025. Reviewed 32 studies covering 29 million participants. https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(25)00118-4/fulltext
[2] “A systematic review with a Burden of Proof meta-analysis of health effects of long-term ambient fine particulate matter (PM2.5) exposure on dementia.” Nature Aging, 2025. Assessed 28 longitudinal cohort studies. https://www.nature.com/articles/s43587-025-00844-y
[3] State of Global Air 2025 Report. Health Effects Institute, October 2025. Air pollution contributed to 7.9 million deaths in 2023; PM2.5 alone accounted for 4.9 million. https://www.healtheffects.org/announcements/new-state-global-air-2025-report-shows-nearly-nine-ten-global-air-pollution-deaths-are
[4] World Health Organization. “Ambient (outdoor) air pollution.” Fact sheet on global health impact of PM2.5, including lifespan reduction. https://www.who.int/news-room/fact-sheets/detail/ambient-(outdoor)-air-quality-and-health
[5] “Air pollution linked to higher Alzheimer’s risk in 28 million older Americans.” ScienceDaily, February 2026. https://www.sciencedaily.com/releases/2026/02/260220010836.htm
[6] Camfil. “PM1: The New Focus to Protect Human Health.” Particle penetration pathways from lungs to bloodstream and organs. https://www.camfil.com/en-us/insights/standard-and-regulations/pm1-is-most-harmful
[7] Camfil. “Why Do We Need a Deeper Connection with the Air We Absolutely Depend Upon.” Indoor air concentration data and time-spent-indoors statistics. https://www.camfil.com/en-us/insights/air-quality/deeper-connection-with-air
[8] Camfil. “How to Improve Indoor Air Quality and Productivity.” Harvard/Syracuse cognitive performance study and CO2 impact research. https://www.camfil.com/en/insights/air-quality/how-to-improve-indoor-air-quality-and-productivity
[9] Camfil. “Wildfire Smoke Air Filters: Camfil’s Solutions and Guide.” MERV rating efficiency data for PM2.5 capture. https://www.camfil.com/en-us/insights/air-quality/wildfire-smoke-filter-solution-guide
[10] Camfil. “Molecular Air Filtration in Life Sciences and Healthcare.” Limitations of particle-only filtration for gaseous contaminants. https://www.camfil.com/en-us/insights/life-science-and-healthcare/molecular-air-filtration-in-life-sciences
[11] Camfil. “The Journey of Activated Carbon.” Activated carbon adsorption mechanism and capability to control over 150 million cataloged chemicals. https://www.camfil.com/en-us/insights/innovation-technology-and-research/journey-of-activated-carbon
[12] Camfil. “MERV vs. MERV A Filter Efficiency Ratings Explained.” ASHRAE Standard 52.2 with Appendix J testing methodology. https://www.camfil.com/en-us/insights/standard-and-regulations/pm1-is-most-harmful
[13] Camfil. “CamCarb PM: High-Efficiency Molecular Panel Filter.” Product specifications for activated carbon panel filtration. https://www.camfil.com/en-us/products/molecular-filters/panel-filters/camcarb/camcarb-pm-_-35067
[14] Camfil. “CamCarb XG Activated Carbon Cylinders.” Product specifications for cylindrical molecular filtration systems. https://www.camfil.com/en-us/products/molecular-filters/cylinders/camcarb/camcarb-xg-_-70341
[15] Camfil. “CamCleaner CC500 Portable Air Purifier.” Pharmaceutical-grade 99.99% HEPA filter; coverage up to 13,000 cubic feet. https://www.camfil.com/en-us/products/air-cleaners–air-purifiers/industrial-range/particulate-air-cleaner
[16] Camfil. “Education Department Protects Students and Staff from Viruses in Their Schools.” City M purifier HEPA H14 classroom performance data. https://www.camfil.com/en-us/insights/case-studies/education-department-protects-students-and-staff
[17] Camfil. “Air Filters in Schools: Everything You Need to Know About Air Quality in K-12 Schools.” ASHRAE MERV 13 recommendation and HEPA purifier PM2.5 reduction data. https://www.camfil.com/en-us/industries/commercial-and-public-buildings/schools-and-universities
[18] U.S. Environmental Protection Agency. “Wildfires and Indoor Air Quality in Schools and Commercial Buildings.” Federal guidance on IAQ management. https://www.epa.gov/indoor-air-quality-iaq/wildfires-and-indoor-air-quality-iaq
[19] Camfil. “Hospital Air Quality Matters.” California hospital admission data attributable to PM2.5 and federal clean air standard compliance. https://www.camfil.com/en-us/insights/life-science-and-healthcare/hospital-air-quality-matters
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