Substances or agents capable of producing or causing cancer are known as:

Substances or agents known as carcinogens are specifically characterized by their ability to produce or cause cancer through various mechanisms, which may include altering cellular processes, initiating mutations in DNA, or promoting the growth of cancer cells. The classification of a substance as a carcinogen often arises from extensive research and evidence linking its exposure to an increased risk of developing cancer in humans or animals.

In contrast, mutagens refer to substances that cause mutations in the genetic material of organisms; while some mutagens can also be carcinogens, not all of them necessarily lead to cancer. Toxins are harmful substances produced by living organisms (such as bacteria or plants), and while they can cause various health issues, they are not exclusively linked to cancer. Pathogens are microorganisms that can cause disease, and although some pathogens may be associated with certain cancers (like human papillomavirus and cervical cancer), they are not classified as carcinogenic agents in the same context as carcinogens.

Thus, recognizing the specific function of carcinogens in the context of cancer development distinguishes them from the other types of substances mentioned. This is why carcinogens are the correct choice in identifying agents that cause cancer.