Bones Breathe Too: Why Indoor Air Quality Matters for Osteoporosis
Table of Contents
FEELING THE CONNECTION BETWEEN BONE AND AIR
In late summer, when wildfire smoke chokes the sky with a copper haze, my neighbor Elena wraps her wrist in a brace before she lifts a grocery bag. After a vertebral fracture last year, even small stumbles set off waves of pain. Her doctor adjusted calcium and vitamin D, urged gentle exercise, and checked her medications. What no one asked about was her air – the days she keeps windows shut against smoke, the gas stove that hisses to life in a small kitchen, the portable purifier she runs on “low” because the “high” setting is too loud during Zoom calls. These details sound incidental. They aren’t. Osteoporosis, a common condition among older adults caused by low bone density that increases the risk of bone fractures, can be exacerbated by common molecules found in air pollution. Improving indoor air quality (IAQ) through source control, ventilation, and filtration can reduce exposure to these pollutants in the indoor spaces where we spend most of our time [1] [2] [3].
What is Osteoporosis and who is most at risk?
Osteoporosis is the most common form of bone disease, affecting over 12% of adults over 50. It is characterized by the weakening and loss of bone tissue and structure, which leads to an increased risk of fractures. Osteoporosis disproportionately affects post-menopausal women, with disease incidence in women over 50 (19.6%) being over four times that of men of the same age (4.4%).
Besides age and gender, multiple environmental factors have been linked to a higher incidence of low bone mineral density – the precursor to osteoporosis. In particular, PM2.5 and Nitric Oxide (NOx) pollution associated with forms of urban pollution such as smog, automotive exhaust, and industrial emissions have been linked to higher rates of bone density loss in older adults. Cohort studies out of China [6] and the UK [4] [31] have linked long-term exposure to PM2.5 to higher rates of osteoporosis, and a 2023 study of postmenopausal women linked higher exposure to NOx and PM2.5 to faster rates of bone loss [32].
Additionally, environmental factors that predispose individuals to pollution exposure – such as being low-income and living near roadways and industrial areas – correlate with comorbid health issues such as hypertension and diabetes and a lack of access to appropriate healthcare. All of these factors can have a synergistic effect on a decline in bone health and the development of osteoporosis.
What we mean by “indoor air quality” OR "Iaq?"
IAQ is the quality of the air inside buildings as it relates to health and comfort; indoors we can encounter particulate matter (especially PM₂.₅, particles ≤2.5 µm), combustion byproducts (tobacco smoke, wildfire smoke), nitrogen dioxide (NO₂) from gas combustion, volatile organic compounds (VOCs) that can form secondary particles, and ozone that infiltrates indoors from outside. Because people spend about 90% of their time indoors and building shells do not perfectly seal against outdoor pollution, most personal exposure occurs indoors [1] [2] [28].
Indoor particles come from cooking, burning candles or incense, smoking or vaping, dust resuspension, and indoor activities.Outdoor particles from traffic, industry, and especially wildfire smoke can infiltrate indoor spaces through cracks and HVAC systems, often elevating indoor PM₂.₅ on smoky days. Field measurements during wildfire episodes show substantial infiltration and demonstrate that HEPA or equivalent portable air cleaners lower indoor PM₂.₅ markedly when used correctly [2] [18] [29] [30].
NO₂ is a reactive gas that can originate from indoor sources, such as gas stoves or unvented heaters; or can infiltrate buildings from outdoor sources such as traffic or industrial pollution.Typical household activities involving combustion, such as cooking, have been shown to elevate indoor NO2 levels. . While this article focuses on particle pollution (ie. PM2.5) for bone-relevant pathways, NO₂ matters both directly and as a marker of combustion exposure [28].
How does air pollution impact bone health?
1) Oxidative stress & body-wide inflammation → faster bone breakdown
Exposure to pollution can increase the prevalence of reactive oxygen particles in the body – contributing to the process of oxidative stress that sets off a cascade of inflammation pathways linked to chronic health issues. In the case of bone health and osteoporosis, this inflammation increases the activity of bone-eating cells (osteoclasts), while simultaneously reducing the creation of bone-building cells (osteoblasts) – resulting in the overall loss of bone tissue. Research into the impacts of particle pollution on the body has linked PM2.5 exposure to increased osteoclast activity and lower levels of bone formation [3] [8] [9].
2) Blood vessels & blood pressure → poorer blood flow to bone
Air pollution can raise blood pressure and harm the delicate lining of blood vessels. High blood pressure and fewer tiny vessels mean less blood reaches bone tissue, which slows repair and remodeling. Human and animal studies connect hypertension with lower bone density and more fragility, while high blood pressure can drive bone loss by pushing the immune system toward osteoclast growth – linking cardiovascular issues with a decrease in bone tissue [10] [11].
3) Pollutant-responsive switches in cells (AhR) → shift toward bone loss
The balance between bone-forming (osteoblast) and bone-eating cells (osteoclasts) can also be upset by environmental disruptions to the the aryl hydrocarbon receptor (AhR), which functions as a sort of control switch between these two cell types. This receptor can be disrupted by compounds such as dioxins and PAHs (polycyclic aromatic hydrocarbons) that are found in smoke, smog, and industrial pollution. Lab studies show that exposure to these compounds can spur osteoclast growth and bone resorption through AhR-dependent signals [12] [4] [5].
4) Heavy metals stored in bone → direct damage
The health effects of heavy metal exposure – such as lead, cadmium, mercury, and arsenic – can accrue over a lifetime, with bones acting as long-term reservoirs. These toxins can have a synergistic effect with bone density loss – accumulation of heavy metals such as lead and cadmium in bone tissue can compromise bone structure, lower bone mineral density, and increase the risks of osteoporosis and fracturing. At the same time, the dissolution of bone tissue can leach even more heavy metals hiding in this tissue into the bloodstream – further accelerating decline. Environmental heavy metal exposures from sources such as industrial pollution, lead paint and pipes in older buildings, and tobacco smoke can lead to toxic heavy metals accumulating in the body over the course of a person’s lifetime [23] [24].
Air pollution is filled with all kinds of pollutants and toxins, including PM2.5, dioxins, PAHs, and heavy metals, each of which can dysregulate the body’s signaling pathways and accumulate in reservoir tissue over the course of a person’s life. This cumulative effect of air pollution exposure exacerbates many chronic health issues that are seen later in life – including osteoporosis and poor bone health. By adopting clean air strategies and technologies to reduce the amount of airborne particle pollution that we are exposed to, we can take a step towards alleviating the burden of some of the most common chronic health conditions facing older adults.
Filtration as part of the solution
Since multiple chemicals and compounds found in air pollution can have an impact on the development of chronic health conditions such as osteoporosis, filtering these compounds out of the air is an important way to reduce exposure. Filtration is an especially important tool for these environmental contaminants because many of them originate from polluted outdoor air. A layered strategy, including source control, ventilation with clean air, and filtration, is the best way to improve indoor air quality.
Outdoor air pollution, such as that from traffic, industry, or wildfire smoke, often infiltrates indoor spaces through a building’s HVAC and ventilation systems. Using HVAC filters with a MERV-13 rating or higher helps filter out these particles and reduces the amount of pollution infiltrating a building from the outside. However, it is important to verify that a building’s HVAC system is compatible with a MERV-13 filter – this can restrict airflow and strain the motors of older ventilation systems if not [1] [29] [30].
In addition to improving HVAC filtration, the use of portable in-room HEPA filters can remove smoke and other airborne particle pollution from indoor spaces [2]. Portable HEPA filters vary in price, CADR, and airflow efficiency – some smaller or cheaper personal units may not be beefy enough to remove heavy smoke from a polluted indoor space. For more resource-constrained spaces, DIY options such as the Corsi-Rosenthal Box (or Air Support Project’s upcoming MERV-13-based purifier Vello) can provide higher airflow and cleaning power for a fraction of the cost [27] [17]. Finally, wearing an N95 and P100 respirator in polluted spaces is an individual-level step that people can take to reduce their personal exposure to airborne particle pollution.
How can you protect yourself?
- Electrify or ventilate cooking. Use a vented hood on high, open a window and run a fan when cooking, or consider switching to a cleaner method such as induction. This can be paired with running a portable HEPA filter, or a MERV-13 based purifier such as a CR Box, during and after cooking [28] [2].
- Upgrade HVAC filtration. Use MERV‑13 or higher filters where your system can handle it (consult a technician if unsure), and replace filters every 60 to 90 days. Sealing leaks around the filter can provide an additional boost to airflow efficiency and reduce strain on the HVAC system’s motor [2]. During periods of high outdoor pollution, run the HVAC system continuously to push more air through the filter.
- Use portable filters. Choose HEPA or equivalently performing units with adequate CADR for the room. During smoke events, high-smog days, and other times where outdoor pollution is high, portable purifiers are a key component of cleaning the indoor air. Read Air Support Project’s guide to Creating a Wildfire Smoke-Free Space to learn how to keep your indoor air safe during a wildfire smoke or other outdoor pollution event.
- Monitor air quality. Stay informed about the Air Quality Index (AQI) in your area to determine the level of pollution in the outdoor air and identify when measures to protect your indoor air should be taken.
CHANGING THE AIR
Elena now keeps a small purifier on her bedroom dresser, and had a technician confirm that her HVAC system can handle a MERV‑13 filter. On bad smoke days, she walks laps in her living room while the purifier runs. Like with most chronic health conditions, osteoporosis and reduced bone density is a complex condition with no single underlying cause. However, research into the health impacts of air pollution have found that there are many different chemicals and compounds that can enter our bodies through the air, and these molecules can disrupt the normal functioning of many of the body’s systems – including exacerbating a decline in bone health. Lowering exposure to airborne particle pollution can help protect against many of the chronic health conditions that impact people as they age. It is a simple, practical, and affordable fix to our built environments that we – as individuals and communities – can do today.
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Courage is the bone marrow of freedom.
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Sarah Masih, MD, MBA
Sarah Masih is the Executive Director of Air Support Project and has extensive experience in project management, fundraising, and communications. Her deep commitment to public health and her collaborative approach with community organizations and health experts make her a vital force in the fight for cleaner air and healthier communities.
S. Riley
S. Riley is a mutlidisciplinary content creator and technology enthusiast with a background in crowdfunding and project management. He holds a BA in English, and is grateful to be able to utilize his unique skill set in service of Air Support Project's humanitarian mission.
Melissa Smallwood
Melissa Smallwood is Science and Technology Policy researcher with a background in neuroscience, psychology, and social science, and the author of The Future of Long COVID: A Threatcasting Approach. They are interested in how disability and healthcare justice intersect with emerging technologies, and are an advocate for COVID mitigation strategies to help end the pandemic.
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