What is a carcinogen?

A carcinogen is defined as a substance that causes cancer. This classification encompasses a wide variety of agents, including certain chemicals, physical agents (like radiation), and biological agents (such as certain viruses). The action of a carcinogen can involve various mechanisms, including causing mutations in the DNA, leading to uncontrolled cell growth and the development of cancerous tumors. This definition is crucial for understanding how certain exposures can increase the risk of developing cancer over time.

Other options do not accurately describe what a carcinogen is. For instance, while some carcinogens can promote genetic mutations, not all do so directly or exclusively; therefore, the broader definition of a carcinogen focuses more specifically on its cancer-causing potential. Similarly, while there are many toxic substances, not all toxic substances are carcinogens, since toxicity does not necessarily imply cancer risk. Lastly, being a naturally occurring element does not inherently categorize a substance as a carcinogen, as not all natural elements pose a cancer risk. Thus, the most accurate description is that a carcinogen is a substance that causes cancer.