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ACKNOWLEDGMENTS

This document was prepared by the staff of the National Institute for Occupational Safety and Health(NIOSH). Principal responsibility for this document rested with the Division of Surveillance, HazardEvaluations, and Field Studies (DSHEFS), Lawrence J. Fine, M.D., Director. Brenda Boutin(formerly with the NIOSH Education and Information Division and currently with the U.S.Environmental Protection Agency) was the team leader for the document.

Major NIOSH contributors were Paul A. Baron, Ph.D.; Raymond E. Biagini, Ph.D.; Brenda Boutin;Geoffrey M. Calvert, M.D.; Robert Castellan, M.D.; Lawrence J. Fine, M.D.; William Heitbrink,Ph.D.; Miriam K. Lonon, Ph.D.; Boris K. Lushniak, M.D.; and Dennis O’Brien, Ph.D. AdditionalNIOSH contributors were Robert A. Glaser; Garry Kent Hatfield; Kay Kreiss, M.D.; Bonita D.Malit, M.D.; Leela Murthy, Ph.D.; Patricia A. Sullivan; Eugene M. White, Ph.D.; and Robert W.Mason, Ph.D. (formerly with NIOSH). Critical review of the document was provided by Leslie T.Stayner, Ph.D.; Nelson K. Steenland; and Greg Wagner, M.D.

We also acknowledge the contributions of Winston Dang and Andrea Blaschka of the U.S.Environmental Protection Agency; and Edward Stein, Ph.D., of the Occupational Safety and HealthAdministration.

The following NIOSH staff members are acknowledged for their support, assistance, and advice inpreparing this document:

Penelope ArthurStephen Berardinelli, Ph.D.Shirley CarrThe late Charles V. Cooper Laura DelaneyJohn Fajen Larry Foster Bryan D. Hardin, Ph.D.Daniel M. Lewis, Ph.D.Howie Ludwig Alan R. LunsfordCharlene MaloneyLawrence F. MazzuckelliJudy MeeseVivian K. MorganRichard W. Niemeier, Ph.D.Andrea OkunTong Man Ong, Ph.D.

Evelyn PalassisLarry ReedVicki ReussFaye RiceTeresa M. Schnorr, Ph.D.Lucy SchoolfieldRonald L. SchulerPaul Schulte, Ph.D.Mitchell Singal, M.D.Marie Haring Sweeney, Ph.D.Doris SweetRodger TatkenDavid M. VotawElizabeth Ward, Ph.D.Martha Waters, Ph.D.Joann A. WessRandy YoungRalph D. Zumwalde

Metalworking Fluids

exposure to MWF aerosol at 1 mg/m3 (thoracic fraction). This may be an underestimate of effect,as only current workers were included in the study; workers who may have left these three plantsas a result of their asthma would not have been included in the study.

Basing an analysis on the same population reported on previously by Greaves et al. [1995b],Eisen et al. [1997] used a cohort approach and proportional hazards model to evaluate theassociation of post-hire asthma to MWF aerosol exposures. Among 1,788 active workers(including assembly workers) in the analysis, 29 reported asthma initially diagnosed after hire.Based on MWF exposures during the 2-year period preceding diagnosis (to correlate with likelytime of asthma onset), incidence rate ratios (RRs) were calculated. With adjustment for age andperiod of hire (before or after 1970), RRs were as follows: 2.0 (95% CI=0.9–4.6) for straightMWF; 0.5 (95% CI=0.2–1.1) for soluble MWF; and 3.2 (95% CI=1.2–8.3) for synthetic MWF.Aerosol exposures for the six asthmatics who worked with synthetic MWFs during the 2 yearsbefore diagnosis averaged 0.6 mg/m3 (inhalable fraction); the range was 0.36 to 0.91 mg/m3, andthe median was 0.58 mg/m3.

Kriebel et al. [1994, 1997] studied workers exposed to soluble oil MWFs (142 workers) andstraight oil MWFs (74 workers) along with less exposed assembly workers in a major machineshop complex manufacturing automobile transmissions. These investigators found evidence for anassociation between self-reported physician-diagnosed asthma and work as a machinist. Aftercontrolling for age, race, gender, and smoking, machinists exposed to soluble oil MWF reportedasthma twice as often as nonmachinists (OR=2.1; 95% CI=0.9–4.6; P<0.10); those exposed tostraight MWF also reported more asthma (OR=1.4), but this latter finding was more likely thanthe former to be due to chance (P>0.10). In an analysis stratified by whether the asthma diagnosispredated employment as a machinist, Kriebel et al. [1994, 1997] found that the association wasstronger for asthma with onset following employment than for asthma predating employment as amachinist. Aerosol exposure measurements were made using samplers with a seven-hole cassetteinlet face selected to approximate collection efficiencies of the American Conference ofGovernmental Industrial Hygienists/International Standards Organization (ACGIH/ISO)size-selective criteria for inhalable mass [Kriebel et al. 1994]. At the time of the questionnairesurvey, machinists at this facility who worked with straight oil MWF had a mean aerosol exposureof 0.24 mg/m3 (inhalable fraction), and those who worked with soluble oil MWF had a meanexposure of 0.22 mg/m3 (inhalable fraction).

Robins et al. [1997] provided relevant data from a study of machinists exposed to aerosols ofsoluble MWF and relatively unexposed assembly workers at an automotive transmissionmanufacturing plant. Among workers who reported not having pre-existing asthma, currentasthma was reported and/or a clinically significant cross-shift FEV1 decrement (of at least 12%)was experienced by 11 of 83 machinists compared with 3 of 44 assembly workers (calculatedunadjusted OR=2.1; 95% CI=0.5–12.3).

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RESPIRATORY PROTECTION REQUIRED IN THIS AREA

CHAPTER 9: Recommendations for an Occupational Safety and Health Program

Good housekeeping includes keeping the floors, equipment, and general workenviron- ment clean. Wastes (including floor wash water) should not be dumpedor swept into MWF sumps or coolant return trenches.

9.3.2 Labeling and Posting

Workers should be trained to be aware of labeling practices in accordance with theOSHA hazard communication standards [29 CFR 1910.1200 and 29 CFR 1926.59].Warning labels and signs should be posted on or near hazardous metalworkingprocesses. Depending on the process and MWF exposure concentration, warningsigns should state the need to wear protective clothing or an appropriate respiratorfor exposure to MWF aerosol concentrations exceeding the REL. If respiratoryprotection is required, the following statement should be posted:

All labels and warning signs should be printed in both English and the predominantlanguage of workers who do not read English. Workers unable to read the labelsand signs should be informed verbally about the hazards and instructions printedon the labels and signs.

9.3.3 Engineering Controls

9.3.3.1 Isolation

Skin and inhalation exposures to MWF and MWF aerosol can be minimized by usingmechanical parts handling equipment and machine enclosures to isolate the workers. Simplesplash-guarding may suffice for low-production machines, but complete enclosure (withventilation) is required for high-production machines. Plant layouts should be such thattransfer machines are isolated from other operations. Workers should be provided withisolation booths or fresh air showers. Machine enclosures are an effective method of reducing worker exposures. Johnston andWhite [1995] have described the features that are important in designing effective enclosures.ANSI B11 [1997] contains detailed enclosure and mist control designs as well asconsiderations for installation and use. Hands [1995] examined exposure data collected at anautomobile parts manufacturing plant to determine the effect of enclosures on MWF aerosolexposures. This study suggests that enclosures (particularly manufacturer’s enclosures thatare original equipment) effectively reduce MWF exposures. Retrofitting enclosure structuresmay also reduce exposures.

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