Document peO2vwn41KdwxokmdbjpYejGj
FILE NAME: National Safety Council (NSC)
DATE: 1936 Dec
DOC#: NSC217
DOCUMENT DESCRIPTION: NSC News Article - Air Contaminants That Affect Health
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A Department for Physicians and Laymen
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B y H. B. M ELLER'
URING the develop,men 1 of
1 present knowledge ol the. in*
' Ihjoisce of air contaminants oh
liea.Ill naturally many theories were ad-
v&ticed that: later scientific work has
mollified or displaced. However, nuL al
ways has the correction been as widely
and thoroughly disseminated as was the
original theory; this condition, perhaps,
has led to scUrte eon fusion.
Then?, are available different pub
lished classifications of dusts. Included
in such classifications are dusts the ex
posure to inhalation of which is, or is
likelv to be, occupational. Of dusts
which are inherently toxic when inhaled
oi oilier,vise absorbed and Which cause
syrtenuY: poisoning, examples are lead,
arsenic, mercury, manganese,. Examples
of dusts which have the ability to pene-
P'.rte, the deep lung tissues and to be re-
limed there are quart;/,, flint, chert., as
bestos, laic, coal, Irony day, slate, and
other types of rock dust'.'
go
`in order too far
that afield
the at
discussion tention wil
may l be
-cnenot
tered upon this hist group and upon
pneumoconiosis, the general terth. used
to designate lung1conditions caused by
dust. Silicosis, .which is caused by the
inhabition of free .silica, lias been prom
inent recently InThe public press, some
times in a way that made misunder
standing possible,, if not probable.. ?
yjff tat Dusts C ause Injury? H has been established that the po-:
tentlaHfv of silicious dusts to cause lung damage hi. with, very few exceptions, dependent upon their content of free Silica (Si(>). The development of sili-
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cosis depends, therefore, upon the con centration of dust containing free silica in the air brehthed. In other Words, the total amount of free silica breathed and retained seems to be the primary fac tor; the length of time necessary for a sufficient accumulation is important, but less so than the total load.
Silica occurs also in chemical Combi nation in silicates. Some of these com pounds have been proved definitely to be relatively harmless to health, some are still in the realm of doubt, and one, asbestos, may cause the disease called asbeslosis, which is the result of lung damage similar to, but not identical with nor as serious as, that produced by free silica.
The size of dust, particles in the'-air which an individual may breathe is im portant, Not often are particles larger than 10 or 12 microns found in the deep lungs, except in the case of asbestos dust, Where fibres as long as 200 microns havUenwcoomrkpeldicathteedirSwilaicyosdios.wnSilleicnogstihsw, uisne. complicated by an infection, is more of an impairment than a disability, ft is not seriously disabling until it reaches an advanced stage, and does not of it self greatly shorten the life of a silicotic. vIteloipss itnhactatshees wwohrkereer mtuubste,rbceulroesmisovdeed froSmilkhoi-sToiicbceurpcautlioosni.s. When a silicotic dies, the immediate cause of death is usually some type of intervening lung infection, as tuberculosis. It is not known just why the presence of silica in the lungs increases susceptibility to tuberculosis, but when an adult with silicosis is exposed to tuberculosis, an active infection may occur, regardless of the previous state of health. It is thought probable that silica dust can
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reactivate healed ' tuberculosis lung lesions of the adult type; how long after such lesions have healed the reactivation is possible is not certain, Exposure of silicotics to tuberculosis or of tuber culous individuals to silica dust is serious and should be avoided.
After silicosis 'has become well estab lished in the lungs, medical science has not found a way.to arrest Ihe progress of the silicotic pi oress toward the stage of disablement except through limiting or preventing further exposure to silica dust. Nor has medical science found a way to prevent tuberculosis from being superimposed upon silicosis, except through control of contact. The course of silico-tuberculosis is chronic and is very difficult to iinfluehce by treatment according to phthisiologists.
Medical Control
As a basis for intelligent determina tion of the physical fitness of a man for :a job in a, dusty trade, physical exam ination, with stereoscopic roentgeno gwriathmtsh-oisf stthuedychgeoset,s,insanteucreaslslya,ryt.heAplroenpg aration of an occupational history with detail as to the exact nature of previous work and of exposure to industrial dust --not a valueless recording of occupa tions as ``laborer," "machinist," etc, Dr, Sayers of the U, S. Public Health Ser vice, has developed a method of securing information for a proper occupational history; among others, Cummings, of Saranac Laboratory, also has worked out a useful history blank.
Standards have been developed for athesuditiaabglneotseischonficsifloicrostiask. inTgherroeenitsgeanlsoo grams of the chest in order lo bring out the characterisin'lung changes.
Periodic physical examinations, in cluding roentgenograms,- are essentia! if employers are. to be enabled accurately taondlearinntethlleigeefnftelcyt otfoIndtriavnidsufearl eaxfpfoescuterde workmen to lower dust concentrations before serious injury has been done, or to work out a system of rotation where indicated as desirable in order that ex-
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posure may be intermittent. Such examin! ion;- are helpful also in showing the
whole story, but in both cases it may be possible to secure the information
effi' iericy of engineering control methods. necessary for the purpose.
The ability to place responsibility in case of claim fur jury is no small part
In one report this statement occurs: "There-is no doubt: in the mind of any
of the value of such initial and periodic examinations.
one familiar with the present dustsampling and dust-estimating methods
Asimstosis. Clinical experience has shown i.hal. the inhalation of a sufficient
that they will be, amended and changed from time to time. At the present writ
ammuil. of asbestos dust, causes a serious type of ill noses, which is rtot accompan
ing we W'ould advise the use of the sim plest possible procedures where dust con
ied by an unduly high incidence.of tUlKTClliosh.
trol alone is in question. If one wishes to obtain values which can be compared
Other dusts and silicate compounds so far studied produce, at most, only a
with published data, it is generally neces sary to copy with considerable care the
mild non--progressive reaction in the lungs, provided there is no significant
technic used in the original case. This is another way of admitting the annoying
atimono.unWt hofilefrneoetsisleirciaousin; ctlhineiirca'lclqyt,n.p.souscih-
fact that results by one method are usu ally not comparable to those obtained
cliotingdaittiioonn.s may give rise to considerable,
by another method." In another place, the report says:
"It
Adequate statistics on morbidity and mortality hum occupational disease, to
is very doubtful if any useful purpose is served by determining accurately ex
serve as a basis for effectively focussing the efforts fo study and control dust
tremely dense dust concentrations--the only excuse for such data is to show the
diseases of the lungs are non-existent.
skeptic that the workplace is much dustier than it should be . . . . .
Preventive Engineering
"It is probable that any sampling pro cedure which fixes concentrations in
It would be needless repetition to at groups 100 per cent apart is sufficient
tempt to discuss ih a technical way the and that the results of any attempts to
einntgeirneesetreidng aprheaseresfeorfreddust':toconIntrdoul.strAialll
come closer to the concentration al the moment of sampling are simply mis
Dust, by Diinker and Hatch, issued in leading. Thus ranges such as G-S, 5-10,
August of this year, which deals compre hensively with the subject; IJ. S. Bureau
10 20, 20-40, etc,, suffice for dust con trol."
of Mines Information Circulars 6840 . Particle Size. As dust particles in the
and mvift, by port, a review
Harrington and of literature on
PDraevveenn
lungs are of the order of 1 micron, with rarely a particle over 10 microtis, dust,
tion of ihtsi Diseases; U, S. Public control for hygienic reasons should be
Health Service Bulletin field and iTdlsVaik, on
T21h7e,
DbeyteBrmlooinma
aimed at particles in the size range found
tion arid Control of Industrial Dust; >
Report ZO of the American Standards
Association; and to the IJ. S. Bureau of
Mines 1or a list of approved protective ,
devices.
It may he said that, in general, the
engineering specialist can and will devise
the necessary equipment to meet: the
conditions specified to him. But the set-- '
ting o! limits of permissible dust concen
tration is not his bill the physician's re-,
spcmsibilhy. 'The engineer is concerned'
with keeping dustiness to or below the ;
limits at present considered satisfactory. .
Methods of Detefrrufung Dust
Some dusts (ns lead) are determined by chemical meihods and the concentra tion in Tr an: -coorded gravimetric-ally as milliiumns {.cr cubic meter. Others (as nil a, when- Txe is a factor in deter mining d-ony-i me; particles), are given by ennui, v liber method gives the
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to have been breathed and retained, Again quoting: " * . , . if one could avoid use of the dusts of 1 micron or less or exclude them from the dust which passes a 325-mesh icreen, nearly all dust diseases would be eliminated," But to avoid the use of or fo exclude these dusts involves very practical limitation. The thought here is to stress the desir ability of study and experimentation in the direction indie: ted by the commit tee making the report..
Dust Elimination
Obviously, it is better, when possible, to purchase eqitiprotmt already supplied with exhaust hood, rather than to have to worry to fit one to equipment not de signed to be hooded . Thus the respons ibility for potential efficiency is upon the manufacturer.
There is available comparatively little information upon which to base the scientific design of hoods. The Preven tive Engineering Committee of Air Hy giene Foundation includes in its recent report a table of minimum air velocities
tuosecaipntugrreancietertaciunttiinndgu,s-tgrriaailndeulsetvsato(fror,
paint spraying, sand pulverizing, electric welding, electric plating, quarrying and mining, and hatters' fur.)
For protective equipment such as dust respirators, air supplied masks, sand blast helmets, and goggles, very com plete information is available, because of the work of the . S. Bureau of Mines, the Bureau of Standards, and the American Standards Association in preparing and issuing specifications to be met if the equipment is to be used under conditions where approval Is nec essary.
Of course, al! agree that, where poss ible, dust should be coni rolled at the source, ahd protective equipment used where this action cannot, be accom plished.
Permissible Dustiness
There are various figures that have been and are bejng used as guides to per missible dustiness where free silica is present. 11 should be noted that many of the data were not determined as tin' medical requirement, but as being at tainable in good practice and apparently satisfactory from a safety standpoint,
In South Africa the figure Is 1 milli gram per cubic nieter (e 3 piP.1i.rie per cubic centimeter, or, approximately 8.3 million per cubic foot). .
Dr. "Lanza found in i'917 in the Jop lin, Mo,, district that, with good engi-
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