Inadequate support: Titanium dioxide was classified as a “possible carcinogen to humans” by inhalation based on studies in rats. However, no conclusive evidence has shown that this compound increases the risk of cancer in people. Furthermore, rats received much higher doses of titanium dioxide than those present in masks, which in addition may only release part of it.
FULL CLAIM: Face masks contain a “cancer-causing compound”; “exposure to titanium dioxide ‘systematically exceeded the acceptable exposure level to TiO2 by inhalation’”
Social media posts claiming that face masks contain a “cancer-causing compound” went viral in early November 2022. The posts (examples here and here) shared an article by osteopath Joseph Mercola that was published on the website Children’s Health Defense on 11 March 2022. The article received more than 3,400 engagements on Facebook and more than 1,600 shares, according to social media analytics tool CrowdTangle.
Mercola has made many inaccurate and misleading health-related claims, including promoting homeopathy, that fluoridated water is unsafe, that COVID-19 deaths have been “vastly overcounted“, and that COVID-19 vaccines cause immunosuppression. Children’s Health Defense has also propagated multiple false and misleading claims about the safety of the COVID-19 vaccines in the past.
Mercola’s claim this time is based on a study published in Scientific Reports in February 2022. The study was conducted by Sciensano, a federal scientific institute that operates under the Belgian Institute for Health, as part of a project that evaluated the quality and safety of different types of face masks. The study’s results, which Sciensiano had already released in an October 2021 report, showed that all the face masks analyzed contained varying amounts of titanium dioxide particles.
But Mercola’s article went one step further, claiming that all face masks analyzed in the study “Contained This Cancer-Causing Compound”, implying that the presence of titanium dioxide is dangerous to mask-wearers.
However, this claim is unsupported and misleading. Below, we will explain why the Sciensano study doesn’t provide sufficient evidence to support the claim that titanium dioxide in face masks is harmful. The review will also analyze current evidence regarding the safety of titanium dioxide.
What is titanium dioxide and why is it present in face masks?
Titanium dioxide is a naturally occurring mineral used as a white pigment and matting agent in paints, paper, and textile products, and as an additive in foods, cosmetics, and medicines. This compound is also an ingredient in sunscreens because it effectively blocks ultraviolet rays.
Titanium dioxide is used in mask fabrics as a whitening agent or to protect the fabrics from ultraviolet light. In addition, textile companies are starting to incorporate titanium dioxide in face masks as a nanomaterial, that is, in the form of tiny particles smaller than 100 nanometers—1,000 times smaller than the diameter of a human hair. Nanoparticles have many applications, including improving face masks’ filtration capacity and antimicrobial activity. However, little is known about their potential effects on human health.
For many decades, titanium dioxide has been considered chemically and biologically inert, meaning that it doesn’t react with other chemicals or with biological tissues. However, recent research raised concerns about potentially harmful effects on human health. Based on that research, the International Agency for Research on Cancer (IARC), part of the World Health Organization, classified titanium dioxide as a “possible carcinogen to humans” (Group 2B) in 2006.
However, this classification doesn’t necessarily imply that titanium dioxide causes cancer in humans. It also doesn’t mean that its presence in face masks is necessarily harmful, as social media posts suggested. As we will explain below, the level of risk in humans isn’t well characterized and depends on many factors, including the dose, amount of time, and route of exposure. To put this classification into perspective, other substances considered as Group 2B carcinogens by IARC are aloe vera and pickled vegetables.
The presence of titanium dioxide in face masks doesn’t demonstrate that masks are harmful
The study from Sciensano evaluated the presence, quantity, and location of titanium dioxide nanoparticles in 12 commercial face masks, including disposable and reusable masks from various suppliers in Belgium and the European Union.
The researchers reported that titanium dioxide nanoparticles were present in at least one layer of each of the 12 face masks, in amounts ranging from 0.8 to 152 milligrams per mask. These nanoparticles were present in nylon, polyester, and non-woven synthetic fibers, but not in cotton fibers.
The authors calculated the amount of titanium dioxide present on the surface of these fibers. Then, they estimated that these levels exceeded their calculated acceptable threshold of exposure by inhalation in all masks analyzed, particularly in reusable masks. However, they didn’t show whether these particles were actually released from the mask and subsequently inhaled by the wearer.
The study defined the threshold for acceptable exposure as the amount of particles per mask that the wearer can inhale without suffering adverse effects. This threshold was set at 3.6 micrograms, based on the limit values of occupational exposure recommended by the French Agency for Food, Environmental, and Occupational Health & Safety (ANSES). All the calculations assumed a hypothetical scenario in which a person wore the mask eight hours per day.
The study determined that the levels of titanium dioxide on the fibers’ surface exceeded the safety threshold. However, it didn’t show whether it could be released from the fibers in the first place. As such, the study couldn’t demonstrate whether the titanium dioxide on the masks could be inhaled by the wearer. Inhalation is the only route of exposure for which there is some evidence suggesting a potential titanium dioxide toxicity. There is no evidence that other routes of exposure, such as skin contact, can cause harm.
Therefore, these results simply mean that “a health risk by inhalation cannot be ruled out when face masks containing polyester, polyamide, thermobonded non-woven and bi-component fibers are used intensively”.
The authors acknowledged the study limitation already in the Abstract, stating, “No assumptions were made about the likelihood of the release of TiO2 particles itself, since direct measurement of release and inhalation uptake when face masks are worn could not be assessed”. The Results and Discussion section also explained that these results didn’t demonstrate that face masks were harmful:
“Face mask have an important role in the measures against the COVID-19 pandemic. So far, no data are available that indicate that the possible risk associated with the presence of TiO2 particles in face masks outweighs the benefits of wearing face masks as protection measure. That is why we do not call for people to stop wearing face masks”.
Therefore, Mercola’s claim that the study showed “exposure to titanium dioxide ‘systematically exceeded the acceptable exposure level to TiO2 by inhalation’” misrepresented the study’s findings.
The authors stated that “The importance of wearing face masks against COVID-19 is unquestionable”, but they also explained that “titanium dioxide isn’t necessary for their production. Therefore they urged regulatory agencies to limit the amount of this compound in face masks to reduce overall exposure to it.
Not only did Mercola’s article not mention the study’s limitations, it further reinforced the false narrative that face masks are harmful by discussing an unproven mechanism by which face masks “can make you sick”.
Specifically, the article cited the “Foegen effect”, which suggests that face masks make COVID-19 more severe by causing a person’s own virions to spread “deeper into the respiratory tract”. But as Health Feedback explained in an earlier review, such an effect has never been demonstrated in the scientific literature for any disease.
Several high-quality studies indicate that the use of face masks is associated with lower rates of COVID-19 cases, hospitalizations, and deaths, particularly when combined with other measures such as physical distancing and frequent handwashing[4-7].
Two 2021 surveys from ANSES and the Danish Environmental Protection Agency also contradict claims that face masks contain toxic chemicals. Although the substances analyzed didn’t include titanium dioxide, these analyses found no health concerns regarding the presence of other chemicals in face masks. None of the chemicals included in the analyses exceeded the safety thresholds established for either adults or children and both studies concluded that such small amounts were unlikely to cause any health risks.
Current evidence on the safety of titanium dioxide nanoparticles in humans
As we discussed above, the toxicity of a compound depends on the route of exposure. And another aspect to consider with respect to nanoparticles is their exceptionally small size. This property is a double-edged sword: it is responsible for both the key advantages and drawbacks associated with nanomaterial use. With respect to human health, nanosized particles can enter the human body through the oral route, through inhalation, and through the skin, potentially accumulating in organs and tissues.
Research about their effects on human health is still very limited, but studies in animals showed that inhaling nanosized particles might pose a greater health risk compared to bigger particles of the same material, because they can reach the lung alveoli, enter the blood, and travel to distant organs where they have the potential to accumulate over time[8-10].
Inhalation appears to be the most relevant and most studied route of exposure when it comes to the toxicity of titanium dioxide. In fact, the IARC decision to classify titanium dioxide as a “possible carcinogen to humans” was mostly based on evidence from animal studies showing that rats exposed to fine particles of titanium dioxide were more likely to develop lung tumors[11, 12].
However, we still don’t know how relevant the results obtained in rats are to humans. One reason is that chronic exposure to titanium dioxide particles doesn’t affect all rodent species in the same way. While such exposure induced lung tumors in rats, a similar exposure didn’t cause tumors or chronic lesions in mice and hamsters. Such different reactions to titanium dioxide exposure even between rodent species means that any attempt to extrapolate these results to humans should be done cautiously[13,14].
In 2011, the U.S. National Institute for Occupational Safety and Health (NIOSH) classified titanium dioxide nanoparticles as a potential occupational carcinogen. This decision was based on data from animal studies, clinical case reports, and epidemiological studies in humans. These studies showed that titanium dioxide particles accumulated in the lung and were associated with mild lung inflammation, although they didn’t demonstrate an association with an increased risk of lung cancer.
But one important limitation of these studies is that they can’t determine whether the effect is due to inhaling fine particulate matter or if the effect is specific to titanium dioxide. In fact, the NIOSH concluded that “the adverse effects of inhaling TiO2 may not be material-specific but appear to be due to a generic effect” of high exposure to that type of particles, regardless of their composition.
Recently, oral exposure to titanium dioxide has also become a matter of public concern. In 2021, the European Food Safety Authority (EFSA) updated its safety assessment of titanium dioxide, concluding that this compound couldn’t longer be used as a food additive.
However, this decision needs to be viewed in light of the fact that the EFSA evaluation didn’t find evidence of carcinogenic effects, general or organ toxicity, and also no adverse effects on fertility and offspring development in experimental animals that ingested titanium dioxide.
The decision to change the safety assessment of titanium dioxide was based on new analyses indicating that a significant proportion of the titanium dioxide in food may be in the form of nanoparticles. As we explained above, nanoparticles have unique properties and adequate carcinogenic studies on food-grade titanium dioxide nanoparticles were lacking. Given the uncertainties, the EFSA stated that it couldn’t rule out potential genetic damage (genotoxicity) from this compound. Therefore, it could also not establish a safe level for daily intake as a food additive.
Posts claiming that face masks contain cancer-causing compounds are unsupported by scientific evidence and misleading. Many of them are based on a study that reported the presence of titanium dioxide in face masks. However, this study didn’t demonstrate that face mask fabrics released titanium dioxide particles in the first place. It also didn’t show that the mask wearer could inhale those particles and do it in a quantity capable of causing harm.
This limitation is relevant because inhalation is the only route which has been associated with an increased risk of tumors in rats. These results in rats led the IARC to classify this compound as a “possible carcinogen” as a precautionary measure, despite the lack of evidence indicating a similar effect in people. There is currently no evidence indicating that the amounts of titanium dioxide found in face masks pose any health risks for the wearer.
- 1 – Verleysen et al. (2022) Titanium dioxide particles frequently present in face masks intended for general use require regulatory control. Scientific Reports.
- 2 – Palmieri et al. (2021) Face masks and nanotechnology: Keep the blue side up. Nano Today.
- 3 – Ophus et al. (1979) Analysis of titanium pigments in human lung tissue. Scandinavian Journal of Work, Environment and Health.
- 4 – Leech et al. (2022) Mask wearing in community settings reduces SARS-CoV-2 transmission. PNAS.
- 5 – Ginther et al. (2021) Association of Mask Mandates and COVID-19 Case Rates, Hospitalizations, and Deaths in Kansas. JAMA.
- 6 – Mello et al. (2022) Effectiveness of face masks in blocking the transmission of SARS-CoV-2: A preliminary evaluation of masks used by SARS-CoV-2-infected individuals. PLoS ONE.
- 7 – Talic et al. (2021) Effectiveness of public health measures in reducing the incidence of covid-19, SARS-CoV-2 transmission, and covid-19 mortality: systematic review and meta-analysis. BMJ.
- 8 – Donaldson et al. (2001) Ambient particle inhalation and the cardiovascular system: potential mechanisms. Environmental Health Perspectives.
- 9 – Nemmar et al. (2001) Passage of intratracheally instilled ultrafine particles from the lung into the systemic circulation in hamster. American Journal of Respiratory and Critical Care Medicine.
- 10 – Ravenzwaay et al. (2009) Comparing fate and effects of three particles of different surface properties: nano-TiO(2), pigmentary TiO(2) and quartz. Toxicology Letters.
- 11 – Chen et al. (2006) Titanium dioxide nanoparticles induce emphysema-like lung injury in mice. The FASEB Journal.
- 12 – Lee et al. (1985) Pulmonary response of rats exposed to titanium dioxide (TiO2) by inhalation for two years. Toxicology and Applied Pharmacology.
- 13 – Bermudez et al. (2004) Pulmonary Responses of Mice, Rats, and Hamsters to Subchronic Inhalation of Ultrafine Titanium Dioxide Particles. Toxicological Sciences.
- 14 – Yamano et al. (2022) No evidence for carcinogenicity of titanium dioxide nanoparticles in 26-week inhalation study in rasH2 mouse model. Scientific Reports.
- 15 – Ramanakumar et al. (2008) Risk of lung cancer following exposure to carbon black, titanium dioxide and talc: results from two case-control studies in Montreal. International Journal of Cancer.
- 16 – Coleman et al. (2020) Fine Particulate Matter Exposure and Cancer Incidence: Analysis of SEER Cancer Registry Data from 1992–2016. Environmental Health Perspectives.