Which of the following is a key characteristic of hazardous materials?

A key characteristic of hazardous materials is that they can have harmful effects on human health or the environment. This defines their hazardous nature, as they pose a risk through exposure, whether it be through inhalation, ingestion, or direct contact. Hazardous materials are categorized based on their potential to cause harm, which can manifest as toxicity, flammability, reactivity, or corrosiveness. Understanding this characteristic is essential for safe handling, storage, and disposal, as it underscores the necessary precautions that must be taken to protect individuals and the surrounding ecosystem from their detrimental effects.

The other choices do not align with the defining characteristics of hazardous materials. Non-toxicity contradicts the essence of what makes a material hazardous. Being always solid is not accurate, as hazardous materials can exist in various states, including liquids and gases. Finally, while some hazardous materials may be recyclable, the recycling process is often complicated by the risks they pose, making them challenging to recycle and not a defining characteristic.