A toxicologist discusses the research and common misunderstandings.
Many media stories have falsely claimed that carbon black is a carcinogen. Similar misleading assertions are frequently made by companies promoting alternative products. The claims are often based on misinterpretations of the most current research, which admittedly can be complex and difficult to understand for people without a technical background.
Let’s ask an expert to answer the question: Is carbon black a carcinogen? As a toxicologist at Orion S.A., Dr. Yufanyi Ngiewih has spent much of his career reviewing the research, and he has a special talent for explaining it in plain language. In the following Q&A, he discusses the most common questions about carbon black’s safety and classification.
Q: How does the International Agency for Research on Cancer (IARC) – the specialized cancer agency of the World Health Organization – classify carbon black? Which studies did the IARC cite when making this classification?
Dr. Ngiewih: In 2010, the IARC classified carbon black as Group 2B – possibly carcinogenic to humans. The classification was based on two inhalation studies in rats published in 1994 and 1995. The studies involved subjecting laboratory rats to “high lung burdens” – excessive amounts of inhaled carbon black over extended periods of time – that led to the formation of tumors in the lungs – but not in other organs. In the same study, mice and hamsters did not develop lung tumors under similar testing conditions.
It is important to note that testing conditions in the rat studies deviated from established guidelines for conducting such toxicological assessments. The rat studies created experimental conditions in the animals that are not representative of real-world occupational environments. For example, the rats were exposed for up to 18 hours per day for a lifetime, compared to an average 8-hour working day over 40 years for workers.
Q: Were similar results ever found in humans?
Dr. Ngiewih: No, human data do not support this classification, and the relevance of the rat model to human exposure scenarios remains scientifically debated.
Q: What kind of epidemiological studies have been done on humans exposed to carbon black?
Dr. Ngiewih: Three major studies have been done at carbon black plants in the UK, Germany and the U.S. These are retrospective “cohort studies” that follow groups of workers in manufacturing to assess how exposures to carbon black affect health outcomes, including cancer occurring anywhere in the body. The studies found no association of carbon black exposure and cancer risk in humans. After reviewing the studies, the IARC concluded that the human evidence is inadequate, meaning that there isn’t enough evidence from human data to say carbon black can cause cancer in humans. More recent studies since the IARC evaluation have confirmed this lack of risk between exposure to carbon black and cancer risk. (Find links to the studies in the Further Reading section below.)
Q: Is carbon black safe to use in materials coming in direct contact with food, despite the IARC classification recommendation?
Dr. Ngiewih: While IARC’s classification is based on high-dose inhalation studies with free airborne particles of carbon black, real-world consumer exposure is negligible due to the way carbon black is used and regulated. In everyday applications, carbon black is embedded in solid or liquid materials — such as plastics, rubber or inks — where it remains locked in place throughout the product’s life cycle. This means consumers are not exposed to carbon black particles in a free or airborne form. Additionally, strict regulations across different sectors set clear limits on the amount of carbon black and impurities like polycyclic aromatic hydrocarbons (PAHs) allowed in products. These rules help ensure that items like cosmetics, food packaging, and household goods are safe for consumer use.
Q: Recently, the Court of Justice in the EU upheld a decision by the General Court to annul the classification of titanium dioxide for carcinogenicity in the EU. Why is this judgement relevant for carbon black and other similar substances?
Dr. Ngiewih: Like carbon black, titanium dioxide has been classified as a Group 2B carcinogen by IARC based on similar rat-inhalation studies involving high lung burdens. Also, human epidemiological studies for titanium dioxide, like for carbon black, have shown no association between exposure to titanium dioxide and cancer. The mode of action in laboratory rats also involves excessive lung burdens causing a condition toxicologists call “lung particle overload.” This means that both substances seem to share similar toxicological profiles, especially regarding their behavior in the lungs due to their poorly soluble particulate nature.
The General Court of the EU (GCEU) annulled the classification of titanium dioxide as a carcinogen, a decision upheld in August 2025 by the Court of Justice in the EU (CJEU). The GCEU ruled that the observed lung tumors in rats were not due to an intrinsic property of the substance, but rather to particle overload caused by its insoluble particulate nature.
This distinction is crucial. For a substance to be classified as a carcinogen under the Classification, Labeling and Packaging Regulation, which is the EU’s implementation of the Globally Harmonized System of Classification and Labelling of Chemicals (GHS), it must possess intrinsic carcinogenic properties.
The IARC classification of carbon black as “possibly carcinogenic” is predicated on a rat-based mode of action (lung overload) involving high lung burdens of particulate matter, which is not an intrinsic hazard and therefore cannot – in alignment with the reasoning used by the General Court in the case for titanium dioxide – be the basis for classifying carbon black as a carcinogen.
In light of this, the CJEU’s ruling, upholding the decision of lower court, reinforces the requirement for intrinsic hazard in classification decisions. It supports the view that carbon black should not be classified as a carcinogen based on effects that are not applicable to human exposure scenarios.
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Dr. Yufanyi Ngiewih is a seasoned professional in chemical regulation and toxicology, currently serving in a senior role as Global Manager for Chemical Regulation and Toxicology at Orion S.A. He holds a Ph.D. in Natural Sciences from the Technical University of Kaiserslautern.
With more than 15 years of experience, he plays a pivotal role in ensuring product safety and regulatory alignment across global markets. He has coordinated toxicological studies, led complex REACH registration processes and represented company and industry interests before national and international regulatory bodies. His expertise spans REACH-like regulations worldwide, nanomaterial compliance and scientific contributions to industry associations such as International Carbon Black Association (ICBA) and Eurocolour.
Dr. Ngiewih is Vice Chair of the Scientific Advisory Group (SAG) of the International Carbon Black Association and a member of the Scientific Working Group of Eurocolour, where he provides expert toxicological input on regulatory developments and industry standards.
Dr. Ngiewih is also a published researcher with contributions to peer-reviewed journals and scientific books, focusing on the toxicological evaluation of carbon black. He is a skilled project manager and communicator, contributing to international conferences and leading cross-industry projects, including worker exposure studies and regulatory advocacy initiatives.
Further reading:
Studies with rats
Studies with humans
EU rulings
European Union General Court. Judgment of 23 November 2022 in Joined Cases T-279/20, T-283/20, and T-288/20, CWS Powder Coatings GmbH and Others v European Commission. CURIA.
Court of Justice of the European Union. Judgment of 1 August 2025 in Joined Cases C-71/23 P and C-82/23 P, France and European Commission v CWS Powder Coatings GmbH and Others. CURIA.
