Evidence for the role of environmental agents in the initiation or progression of autoimmune conditions

The concordance of autoimmune disease among identical twins is virtually al ways less than 50% and often in the 25-40% range. This observation, as well as epidemic clustering of some autoimmune diseases following xenobiotic ex posure, reinforces the thesis that autoimmune disease is secondary to both genetic and environmental factors. Because nonliving agents do not have gen omes, disease characteristics involving nonliving xenobiotics are primarily secondary to host phenotype and function. In addition, because of individu al genetic susceptibilities based not only on major histocompatibility comp lex differences but also on differences in toxin metabolism, lifestyles, an d exposure rates, individuals will react differently to the same chemicals. With these comments in mind it is important to note that there have been a ssociations of a number of xenobiotics with human autoimmune disease, inclu ding mercury, iodine, vinyl chloride, canavanine, organic solvents. silica, L-tryptophan, particulates, ultraviolet radiation, and ozone. In addition, there is discussion in the literature that raises the possibility that xen obiotics may also exacerbate an existing autoimmune disease. In this articl e we discuss these issues and, in particular, the evidence for the role of environmental agents in the initiation or progression of autoimmune conditi ons. With the worldwide deterioration of the environment, this is a particu larly important subject for human health.