Which chemical compound, formerly used in pesticides, poses a risk to human health?

Chlordane is the correct answer because it is a chemical compound that was widely used as a pesticide to control termites and other pests until it was banned in the United States due to its harmful effects on human health and the environment. Chlordane is a persistent organic pollutant that can accumulate in the environment and in human tissues, leading to various health risks, including cancer and endocrine disruption.

In contrast, while chlorofluorocarbons (CFCs) and carbon monoxide are indeed hazardous substances, they are not classified as pesticides. CFCs are primarily known for their role in ozone depletion, and carbon monoxide is a toxic gas that can cause suffocation, but they were not specifically used as pesticides. Dichlorvos is another pesticide that has been associated with health risks, but chlordane is more well-known for its historical usage and specific health implications.