Metalworking fluids (MWFs) is the name given to a range of oils and other liquids that are used to cool and lubricate metalwork when being machined. MWFs are classified as either "straight” oils or "neat" oils (not meant to be diluted with water, and may contain highly refined petroleum, animal, marine, vegetable or synthetic oils); soluble oil (highly refined petroleum oils and emulsifiers); semi-synthetic fluids; and synthetic fluids (which may include detergent-like components). The last three classes are diluted with water before use. All MWF classes may contain additives such as stabilizers, biocides, dispersants, dyes, and odorants. When MWFs are used, a primary concern is the presence of contaminants that encourage the growth of bacteria and fungi. Also, there is a potential for oils to be heated high enough where the cutting tool works on metal workpiece to form polynuclear hydrocarbons (PAH's).
While MWFs are used by many workers safely, problems can develop when good hygiene practices are not followed or when fluids are not properly managed or maintained. Major health concerns of improperly managed fluids or when good hygiene practices are not followed include skin irritation, allergic contact dermatitis, irritation of the eyes, nose and throat, and, occasionally, breathing difficulties such as bronchitis and asthma. Although rare, some workers have contacted hypersensitivity pneumonitis (HP) from improperly managed fluids. HP is an allergic type reaction in the lungs that may be caused by exposure to certain microbial products. HP is marked by chills, fever, shortness of breath and a deep cough - similar to a cold that will not go away. Prior to 1985, the use of poorly refined mineral oils had been associated with an increase risk of cancers of the larynx, rectum, pancreas, skin, scrotum, and bladder. The following metalworking fluid references provide more hazard identification and health effects.
- Oil mist (mineral). National Institute for Occupational Safety and Health (NIOSH), (May 1994). Provides an Immediately Dangerous to Life or Health (IDLH) document that includes acute toxicity data for oil mist.
- Criteria for a Recommended Standard: Occupational Exposure to Metalworking Fluids. U.S. Department of Health and Human Services (DHHS), National Institute for Occupational Safety and Health (NIOSH) Publication No. 98-102, (January 1998). Reviews available information about the adverse health effects associated with occupational exposure to metalworking fluids and aerosols.
- PubChem – Mineral Oil. The National Library of Medicine (NLM).
- Report on Carcinogens (RoC). U.S. Department of Health and Human Services (DHHS), National Toxicology Program (NTP). Identifies and discusses agents, substances, mixtures, or exposure circumstances that may pose a health hazard due to their carcinogenicity. The listing of substances in the RoC only indicates a potential hazard and does not establish the exposure conditions that would pose cancer risks to individuals.
- Mineral Oils: Untreated and Mildly Treated. NTP classification: Known to be human carcinogens
- International Agency for Research on Cancer (IARC) Monographs on the Evaluation of Carcinogenic Risks for Humans. World Health Organization (WHO).
- Overall Evaluations of Carcinogenicity: An Updating of IARC Monographs Volumes 1 to 42. IARC Classification: Carcinogenic to humans (Group 1).
- N-Nitroso Compounds in Industry. OSHA Hazard Information Bulletin (HIB), (March 15, 1990). Alerts field personnel of the potential for amine compounds, used in many industrial processes, to be nitrosated with nitrogen oxides from the air.