harmful

Harmful is an adjective used to describe something that has the potential to cause harm, injury, or damage to people, property, or the environment. The term is often used in health, safety, environmental, and policy contexts to distinguish things that may pose a risk from those that are benign. In risk assessment, harmfulness depends on exposure, dose, duration, and context; a substance, action, or information may be considered harmful under certain conditions but not others.

In health and safety, harmful substances include toxic chemicals, pathogens, or materials that can cause illness or injury. In the environment, pollutants and destructive practices can have harmful impacts on ecosystems, biodiversity, and resources. Socially and psychologically, activities such as harassment or misinformation can be described as harmful because they cause distress, stigma, or poor decisions.

Classifications sometimes appear on labels or safety data sheets, using terms such as "harmful" or "toxic" to indicate risk levels. The absence of harm in everyday use does not guarantee safety; effective mitigation depends on exposure control, engineering controls, protective equipment, and education. Regulations may require warning labels, usage restrictions, or remediation measures to reduce harmful effects.

Because harm is context-dependent, what is harmful in one setting may be harmless in another. Assessing harmfulness involves evaluating potential outcomes, likelihood, and the values at stake. See also harm, toxicity, hazard, risk, safety.