Epidemiologic studies investigating the cancer risk associated with using metalworking fluids (MWFs) were reviewed. Results of a comprehensive, systemic survey of the epidemiologic evidence for occupational use of MWFs being associated with cancer of the skin and scrotum, larynx, rectum, pancreas, and bladder by NIOSH and which were included in a NIOSH criteria document for MWFs were presented. Specific studies covered included retrospective cohort mortality and cancer incidence studies of MWF exposed cohorts and associated nested case/control studies, proportionate mortality ratio (PMR) studies, and population based (PB) studies. A case/control study and a cancer incidence study and several case reports suggested MWFs, primarily straight oil MWFs, were associated with increased risk of skin and scrotal cancer. None of three PMR studies found an increased risk for skin and scrotal cancer. A number of cohort, PMR, and PB studies found increased risks for laryngeal and rectal cancer, especially for exposure to straight oil MWFs. Several cohort and PMR studies found increased risks for pancreatic cancer among MWF exposed workers. The strongest evidence was for grinding with synthetic MWFs and machining with straight oil MWFS. Some studies were inconsistent; for example, excess cancer risk was found in black, but not white, workers. One of six PMR studies and several PB case control studies found significant excess risks for bladder cancer after controlling for smoking. Neither of two cohort cancers found an elevated bladder cancer risk; however, both were based on small numbers. The route of MWF exposure was generally through dermal contact or inhalation; however, because of the large sizes of many airborne MWF droplets, gastrointestinal exposure may also have occurred. The authors conclude that increased risks for larynx, rectal, pancreatic, skin and scrotal, and bladder cancer were associated with the use of some types of MWFs. Because of the long latency period for solid organ tumors, the MWF exposures probably occurred before the mid 1970s. The risk of cancer from MWF exposures since the mid 1970s is undetermined because a definitive study of workers entering jobs with MWF exposure during this time period has not yet been performed.
Geoggrey M. Calvert, National Institute for Occupational Safety and Health, 4676 Columbia Parkway, R-21, Cincinnati, OH 45226