What is defined as anything that is known or reasonably believed to cause disease in humans or animals?

The definition of an infectious substance specifically pertains to materials that are known or reasonably believed to contain pathogens capable of causing disease in humans or animals. This includes bacteria, viruses, and other microorganisms that can lead to infections. Infectious substances are classified as dangerous goods within transportation regulations because they pose a significant risk to public health and the environment if not handled properly.

The other options do not align with the definition provided in the question. Hazardous waste typically refers to waste materials that can be harmful to human health or the environment but do not necessarily have to contain infectious agents. Biohazard material is a broader term that encompasses any biological substance that poses a threat to the health of living organisms, but it isn’t as specific to infectious agents as the term infectious substance. Radioactive substances pertain to materials that emit radiation and can be harmful due to their radioactive properties, but they do not necessarily relate to diseases caused by infectious agents. Hence, the identification of infectious substances directly aligns with the risk they pose in terms of causing disease, making it the most accurate choice.