In the present work we studied: (a) biochemical changes; (b) serum immunoglobulins (IGs); and (c) mitogenecity of peripheral blood lymphocytes (PBL) in workers directly exposed to high concentrations of pollutants in several sectors of a major copper company in Alexandria. These sectors included the aluminum utensils refining of copper semicontinuous aluminum casting, brass foundries, and steel furnaces. Toxicants in these sectors included aluminum, hexachloroethan, silica, cadmium, copper, mercury, lead, abestos, nickels, zinc, silver, carbon iron, and sulfate present in high concentrations in the sectors where workers are directly exposed. Administrative personnel (indirectly exposed) were included as positive controls; negative controls were people living in areas of Alexandria where the concentrations of these toxicants are extremely low. All personnel of the aluminum utensils area showed reduction in serum levels of IgG, IgA, and IgM assayed by enzyme-linked immunosorbent assay (ELISA) while workers directly exposed in the other sectors showed elevated Igs. Mitogenic activity in cultured PBL assayed by 3H-thymidine uptake was impaired in all plant personnel. However, experimentals showed increases in the interleukins IL-2, IL-4, IL-6, interferon-gamma (IFN-gamma), tumour necrosis factor-alpha and-beta (TNF-alpha and beta) assayed by ELISA. Changes were directly related to duration of exposure. Some workers showed autoimmune symptoms such as arthritis and spondylitis. Allergic manifestations were also recorded. Thus, abnormalities were greatest in directly exposed workers, while other plant personnel showed some form of toxicity in the parameters studied. Clinical significance of the immunologic abnormalities seen is under further study.