How can a chemical be classified as "hazardous"?

A chemical is classified as "hazardous" primarily based on its potential to pose risks to human health or the environment. This assessment involves considering factors such as toxicity, reactivity, corrosiveness, and environmental impact. Hazardous chemicals can cause adverse health effects in humans, such as causing illness or injury, or they can have detrimental effects on ecosystems, including pollution and harm to wildlife.

The other options focus on characteristics that do not necessarily relate to the safety or environmental impact of a chemical. For example, the cost of disposal does not inherently determine whether a chemical is hazardous; a non-hazardous chemical could also be costly to dispose of. Similarly, being a liquid at room temperature does not automatically classify a substance as hazardous, as many benign liquids exist. Lastly, the source of a chemical (commercial or otherwise) does not define its hazard status; many chemicals from commercial sources are safe, whereas others from non-commercial sources can be highly hazardous. Thus, the key factor in determining whether a chemical is "hazardous" is its potential to pose risks to health or the environment.