Document ZJ6vQ7kBwzxzD61Y0V6LRmjrd

INDUSTRIAL HYC1ENE slant, that the physiological effects pro duced are proportional to this product, and that peaks are not disproportionately above the accepted limit This may not always be valid because of variations and differences in factors such as rates of absorption and elimination and the type of effects produced Tune-weighting does not consider the chron ological sequence m which these peaks oc cur the response from two or three peaks occurring withm a short time can be much more serious than if these peaks occur at widely spaced intervals It is most important to emphasize the im portance of sampling procedures Spot sam pling too is a poor way to assess total ex posure--it is easy to mum peak exposures Conversely, in the hands of the untramed investigator, it may be too easy to sample only obvious peak exposures Samples taken over a long penod may be adequate for esti mating total exposure, but they only give the average concentration over the sampling penod This may be adequate only when one employs continuing sampling procedures which record the concentration at successive short intervals over this prolonged penod of time Measuring the Hazard To determine exposure levels to chemical and biological atmosphenc contaminants, as well as to measure physical energy stresses, the industrial hygienist uses either directreading instruments or laboratory analyti cal methods The limitations and applications of the vanous instruments and techniques used to measure environmental stresses are dis cussed m this section, which is adapted from a paper0 presented by H F Schulte at the 1963 National Safety Congress Sampling techniques What must be measured and evaluated in industrial hygiene sampling is usually the dosage the worker receives--the amount of toxic material he takes into his body Dura tion of exposure and concentration and type of material are important For the concen tration measurement, a test can be made on the air m the worker's breathing zone In some cases, the measuring instrument can be attached directly on the worker and he can carry rt throughout the working day (this is done with a film badge for measur ing radiation exposure). Relatively few samplers are available at the present time for taking continuous samples in the breath ing zone The other technique is to measure concentration in the breathing zone over carefully selected intervals, then average the results and weight each measurement ac cording to the length of exposure The re sult is a tune-weighted average concentra tion. A satisfactory averago exposure measure ment during a particular time penod, is af fected by changes from day shift to night shift, from winter to summer, routine changes in process operations, or daily changes m rate and direchon of air move ment, temperature, or altitude Then too, will the presence of the sampler alter the routine of the operation in any maimer? Is the contaminant soluble or insoluble m bod ily fluids'* What is its particle size distribu tion and m what portion of the respiratory tract is it likely to deposit? What is its chemical nature? Organic mercury acts quite differently from mercury vapor, which, in turn, is quite distinct from mercury oxide. Finally, are there limitations on the peak dose rates as there are for beryllium and some other compounds7 If the samples are collected at the right places and combined with a time study of the worker s activity, they can give a meas ure of the worker's intake of the toxic sub stance Methods of collection are given in Table 39-D Whether direct-reading or laboratory techniques are to be used is a matter of pro fessional judgement The results obtained must be compared with a threshold limit value with a full knowledge of its limita tion and consideration of other factors in the situation Unne assays add to the facts available for making an evaluation of ex posure These, in turn, must be combined with knowledge obtained by the physician directing an adequate medical program All this serves to emphasize the basic teamwork approach of the industrial health program National Safety Council Transactions, - ,12 37 42 1963 39-28