Age
The period of childhood may be viewed as a succession of phases or stages with distinguishable anatomical, physiological, and psychological characteristics A child’s exposure and vulnerability to internal, social and physical components vary over developmental phases, ranging from preconception, fetal period, neonatal period, infant, toddler, early childhood, middle childhood and early and late adolescence. Over these time periods children subjected to a wide diversity of physical and social exposures in places and times, exposures over which they have little control. A child’s individual vulnerability varies due to their extensive biopsycho-social development. Children also have a comparatively higher uptake of exposures due to their physiology and less developed detoxification metabolism