The utilization of metalworking fluids in the metal machining technological process provides, apart from benefits, certain negatives that are mainly associated with air contamination of the working environment. Typical health problems that result from inhalant exposure of metalworking machine operators to the metalworking fluid mist include respiratory diseases (asthma, chronic bronchitis, hypersensitivity pneumonitis), cancer, and skin diseases. Possible health risks posed by the utilization of metalworking fluids, various methods for measuring their concentration in the working environment, and treatment of MWFs are discussed. A typical particle size range of liquid aerosol (oil mist) is in the range from 0.1 to 10 μm and more than 75% of MWF particulate matter is located in the sphere of respirable fraction (particle size less than 5 μm) that poses the highest risk for the human body. MWF aerosol mass concentration in the working atmosphere varies depending on the type of working activity, and MWFs used in a wider range (average exposure in the range of 0.55 to 5.36 mg·m^-3). Attention also should be paid to microbiological contamination of water-based MWFs, when they are used or stored after dilution for longer term. The most often occurring microbial species at considerable concentration is the bacteria Pseudomonas pseudoalcaligenes. Other important species include Mycobacterium, Pseudomonas, Morganella, Citrobacter freundii, Acinetobacter, Bacillus, Fusarium, Trichoderma, Penicillium, etc.