What are polychlorinated biphenyls commonly classified as?

Polychlorinated biphenyls (PCBs) are indeed classified as all of the options presented. They are odorless liquids, which means they do not emit a strong odor and can be difficult to detect without proper equipment. This characteristic contributes to their widespread use in industrial applications, such as in electrical equipment, until they were banned due to health concerns.

As organic compounds, PCBs contain carbon and are structured in a way that classifies them within the larger category of organic chemistry. This classification is fundamental to understanding their chemical properties and behavior in the environment.

PCBs are also recognized as carcinogens, which means they are substances capable of causing cancer in living tissue. This classification is critical for both regulatory purposes and public health considerations, leading to their regulation and the ultimate ban on their use in many countries.

When considered together, these aspects—being odorless, being organic compounds, and being classified as carcinogens—illustrate the multifaceted health and environmental risks associated with PCBs, reinforcing why the combined classification as "all of the above" is accurate.