organochlorine pesticides ( oc ) and polychlorinated biphenyls ( pcbs ) were measured in samples of breast milk taken from 92 donors representative of regional populations in southern kazakstan . the world health organization protocol for assessing levels of chlorinated contaminants in breast milk 
 was followed . 
 the most prevalent oc residues were beta - hexachlorocyclohexane ( beta - hch ) , p , p'-dde , p , p'-ddt , hexachlorobenzene , and alpha - hch . the measured levels of beta - hch were among the highest reported in the published literature . 
 data from aralsk , near the aral sea , indicated continuing ddt exposure . 
 overall pcb - toxic equivalent levels ( 22 pg / g fat ) were similar to those reported in industrialized european countries . 
 pcbs were highest in atyrau in the caspian oilfields.imagesfigure 1 .