Benzene contamination in sunscreen: Not worth getting burned
Unprotected exposure to solar radiation is a major cause of skin cancer. Approximately 80-90% of skin cancers are believed to be attributable to skin damage from solar radiation. Skin cancer is the most common type of cancer in Canada, with over 80,000 Canadians diagnosed each year. It can also be deadly if not detected early, especially in the case of melanoma, which causes over 900 deaths in Canada each year. Skin cancer is also a growing concern in the face of climate change, which is believed to be contributing to increased incidence of skin cancers around the world due to ozone depletion and increased global temperatures.
Sunscreen is an effective method of protection against skin damage from solar radiation and has been shown to reduce the development of skin cancer. Sunscreen is particularly beneficial when other methods of sun protection, such as clothing or shade, are not practicable, such as during outdoor recreation or outdoor work. Sunscreen, in conjunction with other sun safety practices, provides a significant public health benefit.
Recently, independent laboratory testing of some sunscreen products identified the presence of benzene, a human carcinogen. The results of this analysis had significant media uptake, leading to concern and misunderstanding among members of the public. This blog will describe the health effects of benzene exposure, discuss the current findings of benzene contamination in sunscreen products, and present opportunities for public health messaging around sunscreen use in the context of the potential risk of benzene exposure.
What is benzene?
Benzene is an organic chemical compound that is a colourless, flammable liquid at room temperature. The primary use of benzene is as a starter material to make a wide range of other chemicals and materials, including those used in plastics, resins, nylon and synthetic fibers, lubricants, rubbers, dyes, detergents, drugs, and pesticides. Historically, benzene has also been used as an industrial solvent, although its use in this application has been declining. Benzene is a natural component of crude oil, and is therefore found in gasoline and diesel engine exhaust. Along with polycyclic aromatic compounds, benzene can be produced by the incomplete combustion of organic materials, and can be found in trace amounts in in wood fire smoke, gas furnace emissions, and cigarette smoke.
What are the health effects of benzene exposure?
Benzene is a known human carcinogen. It can cause acute myeloid leukaemia and acute non-lymphocytic leukaemia, and has also been associated with acute lymphocytic leukaemia, chronic lymphocytic leukaemia, multiple myeloma, and non-Hodgkin lymphoma. Much of the research on the health effects of benzene exposure has occurred in occupational groups, including workers in manufacturing, those involved in the transport and dispensing of gasoline and crude oil products, and workers exposed to vehicle exhaust such as drivers and maintenance workers.
Why is benzene in some sunscreen products?
Benzene is not a standard ingredient of sunscreen. The U.S. Food and Drug Administration (FDA) states that due to its known toxicity, benzene should not be used in the manufacture of drugs (including sunscreen) unless it is unavoidable in a product of “significant therapeutic advance”. If that is the case, benzene may be present in the product at concentrations up to two parts per million (ppm).
However, an independent laboratory investigation published in May 2021 detected benzene in various sunscreen and after-sun products sourced from the U.S. This independent testing of sunscreen products included 294 unique batches of sunscreen and after-sun products representing 69 brands. Out of those 294 batches, 78 contained detectable levels of benzene (27%), 14 of which were over the 2-ppm limit for drug products set by the FDA (4.7%). After this initial testing, a further 368 sunscreen and after-sun product samples from the U.S. and Canada were gathered for testing through consumer crowd-sourcing, with the results of this analysis published in March 2022. This updated study found that out of 661 product samples, 192 had detectable levels of benzene (29%), 72 of which were over 2-ppm (11%).
The testing found significant variability in the presence and levels of benzene detected from batch to batch, even within a company. This variation suggests that benzene was unintentionally introduced during the manufacturing process of these products. However, the exact mechanism for this contamination is unknown and the subject of ongoing investigation.
One hypothesis for these findings is that inactive ingredients used in the manufacturing process may be introducing benzene contamination. In particular, some inactive ingredients such as carbomers (used as a thickening agent) and isobutene (used as a spray propellant) are made from hydrocarbons, which may be manufactured with benzene. Chemical spray propellants are of particular interest in this investigation, as high levels (greater than 2-ppm) of benzene were most frequently found in chemical spray formulations of sunscreen and after-sun products. The contamination does not appear to be correlated with any particular active ingredient in sunscreens, including avobenzone, oxybenzone, octisalate, octinoxate, homosalate, or octocrylene.
What is the risk of benzene exposure from sunscreen?
While the identification of benzene in detectable levels in sunscreen and after-sun products is concerning, the majority of tested products (71% in the March 2022 analysis) did not contain benzene. Most products also contained concentrations of benzene below 2-ppm. While there is no safe level of benzene exposure, these levels of benzene are thought to be relatively low risk.
There is little evidence that skin can absorb benzene in the application of contaminated sunscreen. One retroactive analysis of the blood concentrations of benzene among U.S. adults did not find any evidence of elevated benzene levels among those who used sunscreen. While it is known that benzene can enter the bloodstream through skin contact, this mechanism of exposure is less studied than exposure by inhalation, which is believed to be the primary mechanism of exposure in most public and occupational settings. While the evidence is lacking, it is also possible that inhalation may be a possible route of exposure to benzene for those using chemical spray sunscreens, especially considering the findings that higher levels of benzene contamination were found in these products.
What key points are relevant to communicating risks of potential benzene exposure from sunscreen?
Due to the media uptake of the recent findings of benzene in sunscreen products, members of the public may be concerned about the potential of carcinogenic chemicals in their sunscreen products. While this concern is justified, it should be presented in the context of the known health impact of solar radiation and the greater risk of skin cancer without sunscreen use. Public health organizations including the FDA and the Canadian Dermatology Association (CDA) emphasize that sunscreen should be used as normal, despite the recent findings of benzene contamination.
Public health practitioners providing information about sunscreen use can:
- Emphasize that benzene is not a normal component of sunscreen and that the recent findings are due to a contamination issue that is currently under investigation
- Acknowledge that while benzene was detected in some sunscreens, the majority of tested products did not contain benzene
- Highlight that the risk of health effects from potential benzene exposure is believed to be low, while the risk of health effects resulting from exposure to solar radiation is known to be high
- Direct concerned individuals to use CDA-approved sunscreens
- Promote the use of sunscreens that do not use an aerosol or other chemical spray, as chemical propellants are hypothesized to be a source of benzene contamination
- Provide education on other methods to reduce exposure to solar radiation, including:
- Limiting sun exposure, especially at mid-day (11 am to 3pm) when solar radiation is highest
- Staying in the shade as much as possible
- Wearing a wide-brimmed hat, sunglasses, and clothing that covers your skin when possible
- Applying broad-spectrum sunscreens with a sun protection factor (SPF) of 30 or higher to exposed skin frequently throughout the day
- Checking the UV Index forecast
Kelsey James is an Environmental Health and Knowledge Translation Scientist at NCCEH.