ABSTRACT
There are many kinds of dusts and other airborne particles in the total environment in which humans work and live. They vary from time to time in number and chemical and physical properties. In the work environment, the health hazards resulting from the exposure to them is of particular importance because they are a common feature and their biological effects are often insidious. In order to prevent or minimize impairment of the health of workers, it is essential to know the concentrations and diameters of harmful substances, their chemical and physical characteristics, and their biological actions. We must be aware not only of the biological effects but also of the mechanisms underlying and controlling their occurrence.
