deleterious

This term describes harm that is often insidious, occurring slowly or invisibly rather than through a sudden, violent impact. It is frequently employed in scientific, medical, or legal contexts to describe the negative consequences of a substance, a habit, or a policy. Compared to "harmful," which is a general term, "deleterious" carries a more formal tone and suggests a cumulative degradation of quality or health. It implies a process of wearing down or spoiling the integrity of a system over time.