Organochlorines and bone : Effects of organochlorines on bone tissue morphology, composition and strength

Abstract: From results presented during the last decade, it is obvious that the skeleton is a targetorgan for a number of persistent organochlorines. So far, however, little attention hasbeen paid to this subject.This thesis examines the effects of one such compound, the ubiquitous PCB-congener, 3,3',4,4',5-pentachlorobiphenyl (PCB126), on rat bone morphology, composition and strength. The impact of a cocktail of persistent organic pollutants (POPs) on bone mineral density in Baltic grey seal and in a small population of Swedish males was also studied.It was found that PCB 126 induced profound alterations in the long bones of the rat;including increased cortical thickness, increased trabecular mineral density, decreasedmarrow cavity, decreased collagen content, structural changes of the collagen molecule and impairment of mechanical characteristics, such as decreased maximum torqueand decreased stiffness. The mechanisms underlaying these effects are not known, butthe effects obtained cannot be explained either by changes in vitamin C and vitamin Alevels, or by disturbances of the sex endocrine system.By peripheral quantitative computed tomography (pQCT) of grey seal bone specimens, thissis also shows that mineral density of trabecular bone was reduced, as in human osteoporosis, during the period of maximum PCB and DDT contamination of the Baltic (1965 - 1985).An epidemiological study on Swedish males indicated a negative relation between bonemineral density and blood levels of the DDT metabolite p,p'-DDE. This implies the possibility that organochlorines may act as skeleto-toxic agents in humans, even at low exposure levels.