Document xzgz3ak1NdJ1aaOkpMB3GgbMy

Iti cr od CoHidl *i**S of ru/>Ot Llailin] fina liftco oad vetor undti prty u'l or vW. CofciWi mint hi maintained M o Itokav of mill doit no' OCC*/. loco/ niAoin' rmtihib* o/ loUming optrlioau tmvntal carrier* rho are adering ilc Con or yoo ygieniil rganiio-' This discussion will l*c limited to |u*ic principles of industrial hygiene j< they relate to fume and dust cx|M'.-ures, to indicate what control measure* are available or used to protect the employee'a health, and to call attention to operations nnd mstcnals which are commonly used in industry, at the same time indicating generally accepted opinion as to their etlrct on health. Many conditions are improved for reasons other than their effect upon health. Better products, better em ployee relationship, reduction in maintenance of equipment may be cited as justification fee inanagemrnt's decisions for such correction. Dsfinitions . I-aymen frequently designate as 'fiunr" any vapor, fog. gas, etc., they may encounter. In industry, the plat ing mist over a chrome lank, the va por or gases, at a metal-cleaning operation or the exhaust gases from a truck arc frequently referred to as "fumes.'' To the industrial hygienist, the term has a more definite mean ing. Tor this-discussion, fume may he considered to be particulate matter formed by the condensation of u va por. A molten bath of lead nl a high temperature causes the racial o vola tilize and form"a vapor. Upon contact with the cooler surrounding atmospbere condensation occurs and the physical state changes from vapor to a solid metallic particle. While duM is also a rolid particle, it is formed by the disintegration of solid materials by grinding, crushing, abrasion, or similar action. Fume particles arc generally small in diameter, w ith the sue dependent upon the type of fume, tire extent of flocculation, and other factors. Dust particles of hygienic significance are those betcweoi one and ten microns in size. (25,400 microns are equiva lent to one inch). Generally speaking, there are two mc-sns of entrance of toxic com pounds into the human body--by in- gcation or via 'he respiratory tract through inhalation of fumes, dust*, mills or gases. Ingestion is of im portance if toxic materials wliich * have a systemic effect are used and adequate washing facilities are not provided, or, where the employees are slovenly in personal habits. Inhalation U considered the xaost important portal of entry ok' fumes or dustn and llie particle size, therefore. Incomes significant in evaluat ing exjKwure. The particles wliich ca;.se the physiological changes are ... those which arc small enough to re main suspended in the air and not those which immediately tall to the floor. Flying particles, which may cause eye injuries are not of hygienic significance since they are not of respirable sie. To judge the serious ness of an exp<*urc by the quactity of detritus adjacent to an operation is often misleading. This is especially true where mechanical ventilation re moves the' fine material but is inade quate to trap or convey the larger particles. In evaluating an exposure it is nec essary to consider the toxicity of the niaierial, the duration of the expo sure, the average concentration cf the contaminant with special attention being paid to those operations which produce high concentrations st some phese of an operating cycle, and the measure' which have been provided --To page 52 Safety Hiwc. Fairmot,. It4f 21