External considerations It is well known that certain chemicals. for example chlorinated pesticides and other chlorinated hydrocarbons, will be stored in the tissues of a wide range of living organisms and may accumulate to toxic level This phenomenon is exacerbated by the fact that the lower forms of life or the organism at lower trophic stages are subsequently ag consumed as food by fish, mammals and his birds These species in turn may be consumedly human 四大学化学学院 2002年7月26日四川大学化学学院 2002年7月26日 12 External considerations ◼ It is well known that certain chemicals, for example chlorinated pesticides and other chlorinated hydrocarbons, will be stored in the tissues of a wide range of living organisms and may accumulate to toxic level. ◼ This phenomenon is exacerbated by the fact that the lower forms of life or the organism at lower trophic stages are subsequently consumed as food by fish, mammals and birds. ◼ These species in turn may be consumed by human