Document zdXMqoXQRjzp2bjDw0eYEOJL0

158 INDUSTRIAL HYGIENE AND OCCUPATIONAL MEDICINE This discussion has covered briefly some of the methods which may be employed in determining the concentrations of atmospheric contaminants in the workroom atmosphere. A sufficient number of samples should be collected at each significant exposure of the worker to permit a reasonable interpretation of the environmental conditions. After an average or representative concentration has been determined for each exposure, and the length of time involved has also been considered, it is Fig. 6.--Electron micrograph of air-borne metal fume and dust collected with the thermal precipitator.. then possible to calculate the over-all or "weighted" value of the worker's exposure for the entire work day. This value may then be compared with the maximum allowable concentration for the particular substance in question to obtain the degree of hazard associated with the worker's exposures. Such evidence may be used not only as an aid in the interpretation of clinical findings but as the basis for any medical and engineering control measures which are found necessary to promote a healthful working environment.