Current population-level evidence does not show that CPAP machines cause cancer. The concern traces almost entirely to a single massive product recall in 2021, when degraded foam inside certain devices was found to release chemicals classified as potentially toxic or carcinogenic. But the largest studies comparing recalled-device users to other CPAP users have found no independent increase in cancer risk, and the story behind the fear is considerably more nuanced than the headlines suggest.
The Recall That Ignited the Fear
In June 2021, Philips Respironics issued one of the largest medical device recalls in history, covering more than 10 million devices in the United States and 15 million worldwide. The recall affected 14 models of ventilators and positive airway pressure machines, including both CPAP and bilevel positive airway pressure (BiPAP) devices. The reason: a polyester-based polyurethane foam used for sound dampening inside these machines could break down over time, potentially releasing particles and chemical fumes directly into the air users breathe while sleeping.1JAMA Internal Medicine. The Philips Respironics Recall of Ventilators and Positive Airway Pressure Machines—Breakdowns in Medical Device Surveillance
The scale of the recall was staggering. These were machines people used every night, for hours at a time, often for years. The idea that a device prescribed to protect your health might be quietly exposing you to carcinogens was, understandably, terrifying. It triggered lawsuits, congressional scrutiny, and widespread panic among the millions of sleep apnea patients who rely on CPAP therapy.
The Chemicals in Question
When the polyurethane foam inside affected devices degrades, it can release volatile organic compounds including dimethyl diazene, phenol, and two forms of toluene diisocyanate. Several of these are classified as potentially carcinogenic or toxic.2PubMed Central. Health risks related to polyurethane foam degradation in CPAP devices used for sleep apnoea treatment That sounds alarming on its face, and the classification is real. A related compound, 2,4-toluenediamine, has been shown to cause liver tumors and mammary tumors in animal studies at sustained dietary doses.3Journal of the National Cancer Institute. Carcinogenicity and Chronic Toxicity of 2,4-Toluenediamine in F344 Rats
But “classified as potentially carcinogenic” and “causes cancer in humans at the doses actually encountered” are two very different statements. Toxicologists distinguish between hazard (can this substance cause harm under any conditions?) and risk (does it cause harm at the levels people actually experience?). Risk assessments of toluene diamine exposure from newly manufactured polyurethane foam have found that even under worst-case scenarios, the estimated cancer risk falls well within what regulators consider acceptable.4PubMed. Risk evaluation of occupational exposure to methylene dianiline and toluene diamine in polyurethane foam A separate evaluation of consumer-grade polyurethane foam that meets voluntary quality standards calculated a theoretical excess cancer risk at or below about one in seven million, with safety margins for non-cancer health effects exceeding 10,000-fold.5PubMed Central. Risk assessment-based verification of the CertiPUR limit values for toluene diamine and methylene dianiline in flexible polyurethane foam
Those figures come from assessments of foam in mattresses and similar consumer products, not from the specific CPAP-device context where degraded foam may behave differently. The foam in recalled CPAP machines was not simply sitting in a cushion; it was positioned in the airpath of a pressurized device used nightly for years, and degradation could increase exposure beyond what intact foam produces. Still, the numbers provide useful context: these chemicals are not uniquely potent carcinogens, and the doses involved are orders of magnitude lower than those that produce tumors in laboratory animals.
What the Largest Studies Found
The most direct way to answer whether recalled CPAP machines actually caused cancer is to look at what happened to the people who used them. A large population-based study compared cancer incidence between users of recalled Philips Respironics devices and users of other manufacturers’ machines. Over roughly six years of follow-up, about 4.8% of users in the study developed cancer. The raw cancer rate was slightly higher in the recalled-device group, but after adjusting for age, sex, weight, smoking, and other factors that influence cancer risk, the difference vanished. The adjusted hazard ratio came out to 0.97, meaning recalled-device users had no statistically distinguishable increase in cancer compared to people using non-recalled machines.6European Respiratory Journal. Association between a recalled positive airway pressure device and incident cancer: a population-based study
A separate case report noted that despite the theoretical carcinogenic potential of the foam’s breakdown products, studies to date have not found an increased risk of lung cancer among users of these devices.7PubMed Central. There Was Something in the Air: A Case of Interstitial Lung Disease Associated With Continuous Positive Airway Pressure (CPAP) Foam Degradation and Inhalation Syndrome That finding is consistent with what the larger population study showed: if the foam degradation were causing cancer at a meaningful rate, it should show up when tens of thousands of users are tracked for years. It has not shown up.
The Swedish Study and Why Smoking Matters
Not every study has been so clean-cut. A Swedish comparison looked at cancer rates in four counties where polyurethane-foam-containing CPAP devices dominated the market versus ten counties where non-foam devices were more common. At first glance, cancer rates appeared higher in the foam-CPAP counties: 4.5% versus 4.1% for all cancers, with an even more striking gap for lung cancer specifically (0.3% versus 0.1%). That sounds like evidence of harm.8European Respiratory Journal. CPAP recall and cancer risk: should we be concerned?
But the study could not account for smoking status, and when a single county (Skåne, known for higher smoking rates) was excluded from the analysis, the difference in cancer risk between foam-CPAP and non-foam-CPAP regions was no longer statistically significant. This is an important lesson in how confounding variables can create illusions of causation. Smoking is such a powerful driver of cancer that even modest regional differences in tobacco use can swamp a small signal from a device-related exposure. Until a study can properly separate the effect of the foam from the effect of the cigarettes, results like these remain ambiguous at best.
Sleep Apnea Itself and Cancer Risk
Here is a complication that often gets lost in the CPAP-recall conversation: sleep apnea itself may raise cancer risk, regardless of what device you use to treat it. A study of U.S. veterans found that after adjusting for age, sex, smoking, alcohol use, obesity, and other illnesses, people with an obstructive sleep apnea diagnosis had roughly double the hazard of developing cancer compared to those without sleep apnea.9PubMed. The Association of Sleep Apnea and Cancer in Veterans That is a striking association, though the study cannot prove causation on its own.
The leading hypothesis involves oxygen deprivation. People with sleep apnea experience repeated drops in blood oxygen throughout the night, and research from a large Spanish cohort found that the amount of time spent at low oxygen saturation was linked to higher cancer incidence in a dose-dependent way. People spending the most time at low oxygen had more than double the cancer risk of those with minimal oxygen drops. The association was strongest in men and in patients younger than 65.10American Journal of Respiratory and Critical Care Medicine. Association between Obstructive Sleep Apnea and Cancer Incidence in a Large Multicenter Spanish Cohort
Not all studies agree on the magnitude of this link. A nationwide analysis of roughly 5.6 million individuals found that overall cancer incidence was similar between people with and without sleep apnea.11PubMed Central. Sleep-Disordered Breathing Sleep Apnea and Cancer: Analysis of a Nationwide Population Sample The discrepancy may come down to how well each study controlled for confounders, or to the specific populations studied. But even if the association is weaker than some estimates suggest, there is a separate and more consistent finding on mortality: among cancer patients who also have severe sleep apnea or significant nighttime oxygen drops, overall survival appears worse. One study found that a composite measure of overnight hypoxia predicted cancer mortality independently of clinical stage and treatment.12PubMed. The role of obstructive sleep apnea and nocturnal hypoxia as predictors of mortality in cancer patients
This matters for the CPAP question because it flips the concern. If untreated sleep apnea genuinely contributes to cancer development or worsens cancer outcomes through chronic oxygen deprivation, then stopping CPAP therapy out of fear of the foam may carry its own health cost. The treatment you abandon could be more protective than the risk you are trying to avoid.
Non-Cancer Health Effects
While the cancer signal has not materialized in population studies, that does not mean the recalled devices caused no harm. Case reports have documented interstitial lung disease in patients exposed to degraded CPAP foam, involving inflammation and scarring of lung tissue. One clinical review noted that although cancer incidence did not appear to increase among users, evidence for other conditions remained limited, and patients who inhaled degraded foam particles experienced interstitial inflammation and pulmonary fibrosis.7PubMed Central. There Was Something in the Air: A Case of Interstitial Lung Disease Associated With Continuous Positive Airway Pressure (CPAP) Foam Degradation and Inhalation Syndrome
Lung fibrosis is a serious condition in its own right, and the fact that cancer risk appears low does not mean the foam was harmless. The recall was warranted. The question is whether the specific fear of cancer, rather than the broader concern about breathing in degraded industrial foam, is supported by the data. So far, the answer to the cancer question specifically is no.
How the Recall Affected Patients and Clinicians
The emotional and practical fallout from the recall has been immense, and it extends well beyond the question of whether anyone got cancer. A survey of clinicians found that nearly 87% reported their own stress levels were affected by the recall, while over 91% said it affected their patients’ health and well-being. Perhaps most telling, about 83% of clinicians said the recall damaged their patients’ trust in medicine overall.13PubMed Central. Quantifying the impact of the Philips recall on patients with sleep apnea and clinicians
For patients, the recall created an agonizing dilemma. Qualitative research found that people with recalled devices described a forced choice between two bad options: stop using the machine and suffer the consequences of untreated sleep apnea, or keep using a device the manufacturer itself had told them might be dangerous. Those who stopped therapy reported worse sleep quality, daytime functioning, and overall quality of life. Those who continued reported persistent anxiety about the potential exposure. The uncertainty about actual risk levels made both choices feel wrong.14SLEEP Advances. Exploring the impact of a medical device recall on individuals with obstructive sleep apnea and healthcare providers: a qualitative study
This is where the real harm of the recall may ultimately be measured. Millions of people who need nightly pressure therapy to breathe properly during sleep were suddenly scared of the thing keeping them alive. Some stopped using CPAP entirely, exposing themselves to the well-documented cardiovascular, metabolic, and cognitive consequences of untreated sleep apnea. Whether any of them developed cancer from the foam remains unproven; that many of them suffered from abandoning treatment is much harder to dispute.
What About Non-Recalled CPAP Machines
If you use a CPAP machine that was not part of the Philips recall, the cancer question barely applies to you. The concern was specific to the PE-PUR sound abatement foam used in certain Philips Respironics models. Machines from other manufacturers, and newer Philips devices with redesigned foam or alternative sound-dampening materials, do not share the same degradation problem. CPAP therapy itself, delivered through a properly functioning and well-maintained device, has no established link to cancer.
Routine maintenance still matters. Any CPAP machine can harbor mold, bacteria, or mineral buildup if not cleaned according to the manufacturer’s instructions. These are hygiene issues, not cancer risks, but they are worth managing for respiratory health. Replacing filters, cleaning the humidifier chamber, and inspecting tubing and masks on a regular schedule is standard care that protects against irritation and infection.
Where the Science Stands on Polyurethane and Foreign-Body Risk
One question that occasionally surfaces is whether polyurethane itself, as a material class, poses a cancer risk. The International Agency for Research on Cancer has evaluated organic polymeric materials and classified them as Group 3, meaning not classifiable as carcinogenic to humans based on available evidence.15European Journal of Cancer. Evaluation of the carcinogenic risks to humans associated with surgical implants and other foreign bodies – a report of an IARC Monographs Programme Meeting That classification covers polymers as a broad category. Certain physical forms of implanted materials (such as smooth thin films) received a Group 2B classification (possibly carcinogenic), but that relates to the geometry of solid implants, not to airborne chemical exposure from degraded foam. Intact polyurethane in a consumer product is not considered a cancer hazard. The problem in the recalled CPAP devices was the specific foam formulation breaking down and releasing chemical byproducts, not the polymer itself.
This distinction matters because it addresses a common overreaction. Some patients have become wary of any CPAP device containing any polymer component, or have avoided therapy altogether. The evidence does not support that level of caution. The risk, to the extent there is one, was tied to a specific type of foam in specific models degrading under specific conditions. It was not a blanket indictment of the materials used in respiratory equipment.
Making Sense of the Numbers If You Were a Recalled-Device User
If you used one of the recalled Philips machines, you were probably exposed to some level of chemical emission from the foam, especially if the foam had visibly degraded. The relevant question is whether that exposure was large enough, and lasted long enough, to meaningfully increase your personal cancer risk. Based on everything published so far, the honest answer is that population-level data show no detectable increase in cancer. The adjusted hazard ratio of 0.97 from the largest comparative study is about as close to “no difference” as epidemiology gets.6European Respiratory Journal. Association between a recalled positive airway pressure device and incident cancer: a population-based study
That does not mean zero risk in any absolute sense. Cancer is a disease driven by probabilities, and proving that something causes zero excess cancer in a population of millions would require far longer follow-up periods than currently exist. Some cancers take decades to develop after an initial exposure. But the reassuring signal from the studies available so far is that if there is an effect, it is too small to detect against the normal background rate of cancer, which is substantial on its own. About 40% of people will be diagnosed with some form of cancer during their lifetime regardless of CPAP use. A hazard ratio of 0.97 means recalled-device users are not standing out from that baseline.
If you are still concerned, talking to your sleep medicine provider about whether your specific device model was affected, whether the foam showed visible signs of degradation, and what replacement options exist is a reasonable step. What the evidence consistently warns against is stopping CPAP therapy out of cancer fear. The known harms of untreated sleep apnea, from cardiovascular disease to daytime impairment to possible effects on cancer outcomes through oxygen deprivation, are far better documented than any cancer risk from the foam.