A systematic comparison of the actual, potential, and theoretical health effects of cobalt and chromium exposures from industry and surgical implants.

Humans are exposed to cobalt (Co) and chromium (Cr) from industry and surgical devices, most notably orthopedic joint replacements. This review compares the potential health effects of exposure to Co and Cr contaminants from these two different sources, both in the locally exposed tissues and at sites distant to the primary exposure. Surgical implantation results largely in exposures to ions, corrosion products, and particles of Co and Cr. Industrial exposures are predominantly to metal compounds and particles. Although there are large literatures on industrial and surgical exposures to these metals, there has yet to be a systematic comparison of the two to test whether more general lessons might be learned about the human toxicology of Co and Cr. Both industrial and surgical exposures cause inflammatory and other immune reactions in the directly exposed tissues. In the lung there is a well-established risk of cancer following long-term exposures to hexavalent Cr; however, the development of sarcoma in the connective tissues adjacent to implants in response to metal particles is rare. Both types of exposure are associated with changes in the peripheral blood, including evidence of oxidative stress, and altered numbers of circulating immune cells. There is dissemination of Co and Cr to sites distant to the orthopedic implant, but less is known about systemic dissemination of these metals away from the lung. The effects of industrial exposures in the reproductive, renal, and cardiac systems have been investigated, but this has yet to be explored after surgical exposures. The form of the metal (and associated elements) in both instances is key to the toxicological effects arising in the body and further characterization of debris released from devices is certainly recommended, as is the impact of nanotoxicology on the health and safety of workers and patients. Biomonitoring schemes currently used in industry could be translated, if required, into suitable programs for orthopedic out-patients. Cross-communication between experts in industrial and occupational medicine and regulatory agencies may be useful.