What constitutes a hazardous substance?

A hazardous substance is defined primarily by its potential to cause harm to human health or the environment. This encompasses materials that may have toxic properties, are reactive, or can pose various safety risks when handled improperly. The designation of a substance as hazardous typically involves considerations of exposure, physical and chemical hazards, and the type of health effects it can induce, such as toxicity or corrosiveness.

In this context, the correct choice emphasizes that a hazardous substance is one that can lead to health risks or unsafe outcomes. This includes chemicals that can cause injury or illness, as well as substances that pose risks such as flammability or environmental damage.

The other options do not accurately define a hazardous substance. A product that is readily available may not necessarily be hazardous; many common consumer products are safe when used as intended. Non-chemical additives, generally speaking, would not typically be classified as hazardous because they may not possess inherent risks to health. Similarly, a routine cleaning agent might be safe for use in household settings, but that is not true for all cleaning agents; some can be hazardous depending on their chemical composition and usage guidelines. Thus, the correct definition focuses on the presence of health risks or unsafe outcomes, aligning with regulatory and safety standards.