Final answer:
Biological agents, which pose a risk to human health, can include microbes like bacteria and viruses. These are classified into Biosafety Levels based on their risk to human health and the environment. While they present certain dangers, biological agents also contribute beneficially as biological barriers and in biological control practices.
Step-by-step explanation:
Biological agents are indeed natural organisms or products of organisms that can pose a risk to humans, which is a true statement. These biological agents include bacteria, viruses, protozoa, and fungi, among other pathogenic microorganisms. They are categorized into different Biosafety Levels (BSLs) based on the risk they present to human health and the environment. The formation of these categories takes into consideration factors like the agents' ability to cause disease, their mode of transmission, and the potential impact of an exposure to the agent.
Pesticides can also be biological agents, such as viruses or bacteria used to control pests. The use of DDT, a chemical agent, shows how over time, pests can develop resistance to control methods, leading to renewed risks to human health. On the other hand, biological barriers, like the harmless bacteria residing in the human body, exemplify a natural defense against pathogenic organisms by preventing their growth and colonization.
In summary, while biological agents can be significant factors affecting human health, they also play a vital role in maintaining health through biological barriers, and even as part of controlled biological control strategies.