Which of the following is not classified as a man-made toxic substance?

Asbestos is a naturally occurring mineral that has been used in various industrial applications due to its desirable properties, such as heat resistance and tensile strength. Although it can pose serious health risks when inhaled—leading to diseases like asbestosis and mesothelioma—it is not synthesized through human activities.

In contrast, polychlorinated biphenyls (PCBs), dioxins, and cadmium are all associated with industrial processes or human activities. PCBs were manufactured for various uses, including electrical equipment and insulation, dioxins are often byproducts of combustion processes and certain chemical manufacturing, and cadmium is produced primarily through mining, metal refining, and as a byproduct of zinc production.

Understanding the distinction between naturally occurring substances and those that are synthesized or manufactured by humans is crucial in environmental health and safety. This classification helps to inform regulatory measures and public health initiatives aimed at mitigating exposure to hazardous materials.