Which of the following is NOT considered a pathogen?

Pathogens are microorganisms or agents that can cause disease in their host. They typically include viruses, bacteria, and fungi, all of which are capable of infecting a host and leading to various health issues. Each of these categories has distinct characteristics that enable them to invade the body, replicate, and disrupt normal bodily functions.

Chemical pollutants, however, do not fit the definition of a pathogen. While they can have harmful effects on human health, causing sickness or disease through toxicological mechanisms rather than through infection, they are not living organisms. Unlike pathogens, which actively replicate and induce disease by infecting a host, chemical pollutants affect health through exposure to harmful substances that may lead to illness over time but do not themselves propagate like biological agents do. This distinction clarifies why chemical pollutants are categorized separately from pathogens in discussions regarding infectious disease and public health.