In metalworking, the temperature of the cutting edge can reach 700 degrees C, which can adversely affect either the surface of the metal processed or the cutting edge itself. To reduce the heat and friction, the metalworking fluids and coolants are used. The most common are the oil-in-water emulsions, which are a mixture of concentrated mineral oils, different additives, and water. The presence of water and organic substrates generates conditions for microbial growth. Bacterial endotoxins can also be frequently detected in metalworking fluids. Rapid rotation of the metalworking tools makes various biological agents to be released as droplet bioaerosols that can be inhaled by the workers, thus producing adverse health effects, mainly on the respiratory system. More than 130 species of bacteria (including pathogens), moulds and yeasts have so far been found in the metalworking fluids and coolants. This paper summarizes the outcomes of projects on the impact of biological agents present in metalworking fluids. Exposure to oil mist, bacteria and endotoxins as well as the variety of health effects resulting from that exposure have been discussed. The findings indicate that the most frequent symptoms reported by the workers include cough with phlegm, wheezing breath, chest tightness and throat irritation. The most common among the diagnosed diseases are chronic allergic bronchitis, asthma, hypersensitivity pneumonitis and acute respiratory dysfunction indicated by decreased FEV1 values. The main skin diseases include oil acne, bacterial infections, dermatomycosis and allergic reactions. The review made the authors conclude that the problem of occupational exposure to biological agents released with coolants during metalworking has not been well recognized in Poland.