reduced.

In its recently published criteria document, NIOSH reviews the studies that have examined the association between metal removal fluid exposure and cancer. NIOSH's conclusions are mixed:

Substantial evidence exists for increased risk of cancer at several sites (larynx, rectum, pancreas, skin, scrotum,and bladder) among workers exposed to MWFs before the mid-1970s. . . .The evidence is equivocal for an association between MWF exposure and cancer at several other sites, including the stomach, esophagus, lung, prostate, brain, colon, and hematopoietic system.

Over the last several decades, substantial changes have been made in the metalworking industry, including changes in MWF composition, reduction of impurities, and reduction of exposure concentrations. These changes have likely reduced the cancer risks.

NIOSH further notes that there is not enough data to conclude that these changes have eliminated all carcinogenic risks.

Scientists and health professionals continue to debate how to interpret the results of the many studies and the significance of the reported findings. The existing literature is of particular concern, because it reflects exposures that occurred before the mid-1970s. How useful is that evidence for us today? Fluid formulations have changed greatly, impurities and contaminants in MRF have been reduced, and industrial and personal hygiene practices have improved in the past twenty to thirty years. There is debate about how much we can depend on these older studies in reaching any conclusions. For more information, see More on Health.