The summer of 2021 has been clouded by negative press about Benzene residues in cosmetic products which have then been followed by product recalls.
What is Benzene?
According to the American Cancer Society, although Benzene is among the 20 most widely used chemicals in the United States, benzene is known to cause cancer and the link between benzene and cancer has largely focused on leukemia and other cancers of blood cells.
Typically, the benzene concentration in cosmetic products is analyzed by methods using headspace sample preparation and gas chromatography (GC/FID) techniques following the United States Pharmacopeia (USP) <467> general chapter. Even when using the significantly more selective and sensitive triple-quadrupole mass spectrometer detectors, high concentrations of benzene were detected in different cosmetic products and confirmed the GC/FID results. All of the aforementioned techniques apply heat to the sample during either sample preparation (headspace process) or analysis (GC inlet, column oven). Using these methods is industry standard and is also suggested by USP.
Where does it come from?
As benzene would never intentionally be used as an ingredient in cosmetic products and would also not be a solvent of choice in the manufacturing process, it poses a question. Why are we seeing high benzene levels in several products? We went a step further and performed additional experimentation consisting of, varying the incubation time, temperature, and sample quantities.
Based on our current results, the data strongly suggests that the ingredient “Benzoyl Peroxide” appears to be the primary source, as it can react and degrade at high temperatures into benzene, as well as during the analysis process itself. Research also confirms this hypothesis. Nevertheless, in the complex matrix of a cosmetic product, it is hard to predict if there are other ingredients present that have either a stabilizing effect on the benzoyl peroxide or alternatively accelerate its degradation.
In other words: the act of analyzing these samples using GC/FID (which requires high temperatures) can artificially contribute to the observation of high benzene levels. This was additionally proven as a viable degradation mechanism by simply heating up a portion of benzoyl peroxide raw material at 85°C for 2 hours, which resulted in a significant increase in benzene concentration.
Another contributing factor could be the fact that residual solvents are commonly only tested in raw materials and finished products right after production, but not in long-term stability studies. The argument is that contamination with residual solvents normally occurs during production or comes from contaminated ingredients, therefore, they generally are not tested over time as they should not change. However, there may be some exceptions.
What do we recommend?
Adamson Analytical Laboratories developed a technique that can analyze benzene residues without the application of any heat to the product, so the “true level” of benzene can be determined.
We also recommend testing stability samples for benzene concentration throughout the study (especially for formulations that contain benzoyl peroxide) with this new method to ensure compliance over the entire shelf life of your product.
________________________________________ K. Tokumaru, K. Horie, O. Simamura, “Decomposition of benzoyl peroxide in benzene in the presence of oxygen”,
Tetrahedron, Volume 21, Issue 4, 1965, Pages 867-870,Source: https://www.adamsonlab.com/benzene-in-cosmetics-where-is-it-coming-from/