In relation to children:
The Children Act 1989 introduced Significant Harm as the threshold that justifies compulsory intervention in family life in the best interests of children.
Physical Abuse, Sexual Abuse, Emotional Abuse and Neglect are all categories of Significant Harm.
Harm is defined as the ill treatment or impairment of health and development. This definition was clarified in section 120 of the Adoption and Children Act 2002 (implemented on 31 January 2005) so that it may include, "for example, impairment suffered from seeing or hearing the ill treatment of another".
Suspicions or allegations that a child is suffering or likely to suffer Significant Harm should result in an Assessment incorporating a Section 47 Enquiry
There are no absolute criteria on which to rely when judging what constitutes significant harm. Sometimes a single violent episode may constitute significant harm but more often it is an accumulation of significant events, both acute and longstanding, which interrupt, damage or change the child's development.
In relation to adults:
A key concept in adult safeguarding work is 'Significant Harm'.
The impact of harm upon a person will be individual and depend upon each person's circumstances and the severity, degree and impact or affect of this upon that person.
The concept of Significant Harm is therefore relative to each individual concerned.