— -a

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April, }$70

Industrial Hygiene Engineering and the
Process-Environment System

tubing to a
ive nominal
). An elec*
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J. E. MUTCHLER*

imber walls
t vapor or
>. The test
ate of 3540
the solvent,
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both singly
: adsorption
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: sealed and
analysis. To
and volume
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*f 0.5.1,1.5,

Environmental Rtstarch Laboratory, Tht Dow Chemical Company, Midland, Michigan

£ K systems approach to industrial health would help integrate the concepts applied
by engineers, industrial hygienists, toxicologists, and physicians, and organize them
into a strategy for health maintenance that b compatible and measurable along com­
mon lines. The advantages of a systems approach to industrial health are viewed in
terms of the application and refinement «{ industrial hygiene standards, participation
of the engineering professions, communication amoag all members of the occupational
health team, and transition we are enjoying with the increasing use of automation,
process control and computer technology.

Introduction

I

to one sec-

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ith Parafilm.
as injected
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—concepts and methods which we have in

N HIS INTRODUCTION to Industrial common, and which can be reduced to quan­
Hygiene Highlights, Professor Theodore tities measurable along common lines.
One concept that relates to all the disci­
Hatch1 reminds us that “it is the responsibility
of industrial hygienists, toxicologists and phy­ plines within the field of occupational health
sicians constantly to review the adequacy of is that of an “acceptable exposure level" or
the methods they employ to demonstrate an “industrial hygiene standard” for inhala­
health maintenance." This is a challenge to tion of materials in the work place.
We are familiar with threshold limit values
all of us who have sensed the broadening
horizons of our profession. For if we are to (TLVs), maximum acceptable concentrations
(MACs), and, in more recent years, the mul­
apply the principles of industrial hygiene suc­
tiple guidelines of the Z-37 Committee of the
cessfully in this time of rampant technological
change, we must keep abreast of new develop­ America National Standards Institute (AN­
ments in the basic disciplines that comprise SI). Much attention has been given to
the development of these standards, but it ap­
our multidisciplinary profession.
Effective management of occupational pears that there has been less concern for the
health programs requires—more than ever— validation and refinement of those guidelines,
coordination and teamwork among those spe­ and clearly, even less concern for the applica­
tion of industrial hygiene standards in the
cialties that function within this broad field.
We need to know and understand how each work place.
Specifically, two aspects of the application
discipline that deals with occupational health
can complement and interact with other mem­ of standards are glossed over to our disad­
vantage. First is the fact that TLV’s and
bers of the occupational health team.
One measure of the compatibility of an other hygienic standards are not easy to use
interdisciplinary' approach to occupational properly. Second, many of the engineers in
health is the emphasis we place on the con­ industry who could be, are not using the con­
cepts and methods applied to industrial hy­ cept of an industrial hygiene standard in their
giene by several specialties—by engineers, in­ decision making. Therefore, we do not benefit
dustrial hygienists, toxicologists and physicians as fully as we could from the assistance the
engineering profession could give us in the
overall control of industrial health hazards.
•Present address: George D. Clayton and An delates.
What can be done to improve this situation?
25711 Southfield Road, Southfield, Michjpn 48075.

I

taterials was
.-arbon disul-

233

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T

AP00001036

234

Mareh-April, 1970

NEW
EMPLOYEES'^

EXPERIENCED
^•WORKERS,
_______________ X RETIREES

ENER6Y

INDUSTRIAL
OPERATION

RiW
MATERIALS

- WASTE
EFFLUENTS
>W.SALA8LE
PRODUCTS

Figure 1. An industrial operation.

The Need for e Systems Approach
Clearly, the application of knowledge from
engineering and medical research, industrial
toxicology, and field experience in environ­
mental control requires some communication
system for the essential interplay to exist
among the various parent disciplines within
our field. If the communication is effective,
that interaction can thrive.
On the other hand, if each discipline inter­
ested in occupational health attacks a parti­
cular problem independently, we likely will
not meet the total need. Thus, we should
adopt an integrated approach in organizing
ourselves to deal with our common concerns.
In the integration of interdisciplinary inter­
est which focuses on a complex problem, one
promising technique is “systems analysis.”
Webster defines a system as a “regularly inter­
acting or interdependent group of items form­
ing a unified whole.”* In simplest terms, a
system consists of a set of components which,
when combined, produce a useful result.
A “system” in terms of industrial health
might be an organizational framework that
defines the strategy for assuring the heaithfulness of a worker population. To that end, the
system might be composed of certain subsys­
tems which could be examined and treated
separately.
If we step back and look at an industrial
operation and examine the various inputs and
outputs from that industrial unit, we observe
an interesting fact: From a larger viewpoint
an industrial operation takes three inputs—
new employees, raw materials, and energy—
and converts them into three distinguishable
products (see Figure 1). First, there are the
salable products which are sold in the market­
place for profit. Second, there are waste
effluents which take the form of solid, liquid,
or gaseous materials—and in turn may contrib­

American

ute to the total environmental burden of air,
water and soil pollution. Third, there is an
output from the system which is of direct con­
cern to those of us interested in occupational
health—the exposed workers and retirees.
We have implied, then, that the work en­
vironment is only part of a larger system.
Specifically, every work situation has three ele­
ments: a process (perhaps a limited operation
or function task), a work environment, and a
worker. Within an industrial unit the process,
the work environment, and the worker are not
totally independent entities. Each is affected,
or could be affected, by the other two de­
ments. In many cases, one cannot alter a
process or even change a job procedure with­
out changing the quality of the work environ­
ment A worker often has enough latitude in
his work procedure to create differences in
the degree of exposure he will encounter on
his job. All three of these items—the process,
the work environment, and the worker—must
receive attention in an occupational health
program.
It is at this point that some of the func­
tional differences within the occupational
health team become important and necessary.
Clearly, the physicians, the nurses, and the
supportive role of toxicology must deal with
the worker and his health; the industrial
hygienists must deal primarily with the work
environment; and the logical extension of this
approach would have the engineers dealing
with the process—which, after all, is causing
the environmental stress in the first place.

back to o
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The Need for Feedback
Control of health hazards in the work en­
vironment can be neither comprehensive nor
complete unless we systematically use the in­
formation that such considerations yield. In a
self-regulated system the key element for con­
trol is "feedback.” This refers to a circularity
of the flow among two or more parts of the
system structure. Such an arrangement assures
that the output of the system is maintained at
a desired level. Typically, this requires con­
stant monitoring of the system output, a com­
parison of thfc output with standards, evalua­
tion of any discrepancies, and a flow of infor­
mation concerning the abnormal deviations

The Proce:
Figure System. T
control nr
application
Most engi

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APOOOOf037

(

f

/, 1970

American. Industrial Hygiene Association Journal

I of air,
re is an
retconpalional

back to other elements in the system structure
so that the procedures may be changed if
necessary. Figure 2 shows an example of a
simple closed-loop system with feedback.
Likewise, in industrial health we have a
critical need for feedback information. We
must know the adequacy of specific environ­
mental control techniques. We also must have
feedback concerning our industrial hygiene
standards. Useful standards should be con­
tinually verified or modified as our knowledge
and experience grow.*
Figure 3 shows a system both for assuring
environmental control—in eluding feedback on
the control techniques employed—and for val­
idating industrial hygiene, standards through
systematic documentation of exposure togeth­
er with systematic medical surveillance of the
exposed worker. This combination industrial
hygiene and medical survey is a simple appli­
cation of a “systems analysis” because it inte­
grates several functional specialties in our
field into a unit that moves toward the same
goal.
This particular approach centers upon the
industrial hygiene standard that could be a
basis but by no means the only basis for effec­
tive interaction among the parent disciplines
represented in the overall system. Here then
we have a strategy for harnessing the toxi­
cological feedback that is available from the
exposed worker in terms of the effect, if any,
on his health at the levels of exposure mea­
sured in the work environment.
The engineering function is represented in
that part of the overall system that deals with
the Process and the Work Environment—as
opposed to that part of the system which deals
with the Worker.
If we separate out the Process-Environment
portion of the overall system we notice a strik­
ing similarity with the typical engineering
control network.

n'V

,ork cnsysirm.
liioc clc|M’ial»on

it, and a
process,

r arc not
affected,

two clealtcr a
ire withcnviion-

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rnri-s in
unter on
. process,
rr—must
ll health
die func-

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necessary'.

and the
deal with
ndustrial

dre work
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place.

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ise the in.•ield. In a
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iris of the
ent assures
intamed at
piircs connit, a comd*. evaluaiv of infordeviations

,

235

Yet, effective communication on how engi­
neering techniques can be utilized is an essen­
tial need and deserves more attention In
practice.
The advantage we have in this respect is
that engineers in general tend to deal with as
large a system as they can handle from a com­
putational standpoint. Therefore, the indus­
trial hygiene standard could be used as an
engineering standard in a larger system that
includes the work environment.
Specifically, the design of a process should
be directly related to the acceptable degree of
environmental contamination by materials
used or produced by the process. Environ,
mental problems, unfortunately, are often
created by poor engineering design. In other

vi

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I

The Process-Environment System

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j
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1
1

Figure 4 depicts the Process-Environment
System. This is represented as a closed-loop
control network that stresses the engineering
application of industrial hygiene standards.
Most engineers are not primarily concerned
with the requirements of industrial hygiene.

v*
>

AP00001038

March-April, 1970

236

Fiouhe 4.

The Protest-Environment Syitem.

words, environmental control must start on
the drawing board.
Second, the operation of the process can
vary in a manner that will cause fluctuations
in the level of contamination of the work en­
vironment Again the acceptable exposure
level serves as a guidepost toward which all
future changes and improvements in the op­
eration of the processes should be directed.
Third, the industrial hygiene standard di­
rectly affects the measurement ol contamina­
tion in a particular work environment—such
measurements to be used for judging accept­
ability of control, following comparison with
the standard that applies in that particular
case. With airborne chemical X, for example,
there may be several ways to measure and
monitor airborne concentrations of that con­
taminant in the work room air. The level of
the threshold limit will often govern what
type of instrument is used, and thereby the
accuracy of the resulting information.
Fourth, we often think of a threshold limit
value as the standard against which the esti­
mate of the exposure is judged, but it is not
enough to take such judgment for granted, for
often the comparison of the measurement and
the standard is made with inadequate infor­
mation. Especially in the use of multiple
guidelines, such as those of the Z-37 Commit­
tee of ANSI, we need a carefully planned
approach—both to gather the proper infor­
mation and then to use it meaningfully.

Finally, the measured deviation from the
industrial hygiene standard frequently points
the way to the type of engineering control or
improvement that results when the measured
concentration exceeds the standard. In other
words, how far must we journey to arrive at
the desired degree of contaminant control?
If the deviation from the TLV is near zero,
there is a different set of alternatives available
than if the measured exposure exceeds the
TLV by a gross amount.
Today’s technological advances have
brought us closer to the day when we can
control the work environment just as we
routinely control a manufacturing process.
First we have seen the development of con­
tinuous monitoring, which can be an effective
diagnostic tool for the identification of pre­
dominant sources of contamination in the
work environment, the proper selection of
contaminant control methods, and the docu­
mentation of occupational exposures.
The second development in this respect is
the digital computer. When coupled to an en­
vironmental monitor the computer provides
an effective means of reducing voluminous
amounts of information into manageable form.
These data, in turn, can be used to show both
short-term and long-term trends of exposure.
When correlated with day-to-day plant oper­
ation such information can result in even
lower exposures.4'* In addition, such data can
be used to describe the exposures of workmen
in what is in effect a continuing industrial
hygiene survey.
These two developments parallel the trend
in the process industries where “on-stream
process analyzers” and “computer applica­
tions” have mushroomed into prominence.
Automatic regulation of product quality is
commonplace—and the marriage of instrujnentation and the computer has provided the
engineering profession with some powerful
new techniques.
This is important to our field because our
allies in the engineering profession are in­
creasingly well-versed in such techniques, and
to the extent that engineers become engaged
in environmental control, we can expect to
take advantage of these and other technologi­
cal advances in controlling the quality of the

*

APOOOOf039

•April, 1970

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American Industrial Hygiene Association ''Journal
work environment.
Advantages of Process-Environment System
Adequate Surveillance
A new process or facility should never be
considered acceptable from our point of view
until studies have proved the environmental
control to be adequate. In view of the im­
portance of process operation and its effect on
the quality of the work environment, environ­
mental surveillance often must be repeated
regularly or, better yet, made a permanent
feature of the Process-Environment System.
frequency of environmental sampling is an
important question, especially where we are
confronted with variable concentrations or
cyclic operations. A continuous monitor can
be invaluable when we try to characterize the
environment in such a way that our measure­
ments are truly comparable with accepted
hygienic standards. Also, the use of multiple
guidelines in the control of the environment
requires that a large number of regularly
spaced samples be used to estimate the inten­
sity of exposure.
Figure 5 shows a schematic representation
of a multipoint continuous monitor that
could be used to document exposures, and to
aid in the control of air concentrations.* The
several sampling probes extend into work
areas where the worker spends his time during
normal work activity. The concentrations at
each of his work areas—or sampling locations
—must be weighted according to the time
spent there to estimate the time-weighted av­
erage concentration, the basis of most of the
threshold limit values.
In addition, continuous monitors, if ap­
propriately used, offer other important ad­
vantages. Among these are: (1) diagnostic
air sampling, including time-dependent and
location-dependent patterns, (2) efficient
documentation, and (3) reduced material loss.
While controlling the air concentrations of
a contaminant in the work room it is often
possible to achieve an important savings from
reduced material loss, especially if the con­
taminant is a raw material or product. Here
is one area where it is very easy to enlist the
help of the engineer. His prime concern with
the economics of the operation of his process

237

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Ficvm 5. Schematic diagram of a continuous
environmental monitoring system.

may help us to achieve our objective of limit­
ing emissions into the work room. Sometimes
it is possible to pay for a continuous monitor­
ing system in a short time with the savings
realized by its use.
Figure 5 indicates that the information
from the schematic environmental monitor
flows through a “computer.” This again is in­
dicative of the changing technology that bears
on our field and at the same time opens new
doors of opportunity for us to do a better job.
A continuous analyzer generates a great
volume of information, and the full use of the
data coming from such a device depends on
how well we can reduce the output to mean­
ingful terms. The digital computer offers us
great help at this point because it can quickly
translate a flood of concentration data into a
comprehensive summary, including several
parameters that may be of importance.
Proper Application of Standards
In a typical control system the error-detect­
ing mechanism is critical. In the case of en­
vironmental surveillance, we are interested in
comparing the estimated worker exposure with
the appropriate industrial hygienic standards.
Whenever volatile substances are present in
the work room, the concentrations will likely
fluctuate so widely that it will be advantageous
to monitor the environment continuously and
test it repeatedly against the various standards
that can be applied. In addition, the applica­
tion of hygienic standards as they are defined
virtually requires the use of continuous or
semicondnuous sampling procedures, reduc­
tion of the measurements to the appropriate
parameters, and then comparison with each
of the appropriate guidelines.
For example. Table I shows the various in-

i

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i

AP00001040

i

March-April, 1970

A

ronment concept is that adequate environ­
mental surveillance allows the use of feedback
to provide a check on our environmental con­
trol efforts—to the extent that we correlate
the environmental information with medical
findings on the same worker population, we
can use that feedback information to validate
or refine our hygienic standards.

l

238
Table I
Industrial Hygiene Standard for Carbon
Tetrachloride
TLV or "acceptable Mir TWA”

10 ppm

Acceptable celling concentration
Acceptable Bisiaum concentration lor
peaks above acceptable ceiling

25 ppm
200 ppm

Acceptable number of peak concentration!
of 5-minute duration for Mu period

2

dustrial hygiene standards that are available
for carbon tetrachloride. To judge the ac­
ceptability of a particular work environment
using these parameters, we would need a mea­
surement in the worker’s breathing zone at
least even- 5 minutes for 8 hours. This mini­
mum of 96 samples would then have to be
reduced to the various sampling statistics that
could be compared with the standards.
Relatively little attention has been given to
this problem of characterizing the work en­
vironment in a manner that will allow proper
application of hygienic standards; it must re­
ceive more attention in the future. Table II
shows one exposure summary that could be
used to judge the intensity of exposure along
several guidelines, both short-term and long­
term. This exposure summary covers a 7-day
period and reduces over 100,000 measure­
ments to an informative, compact table. The
information comes from a continuous environ­
mental monitor linked directly to a digital
computer.
Documentation and Feedback
The third advantage of the Process-Envi­

w

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nl
c<

As the problems of concern in the work
room from environmental stresses become
more subtle and complex, the need for sys­
tematic studies on the relationship between
exposure and consequence increases, and we
need more than ever to complement the re­
sults from laboratory studies with planned
systematic findings on groups of people ex­
posed to the suspected agent under real
conditions.*-*-1

c;»
\vt

Summary
Progress in our field—occupational health
—will continue to depend on a "team ap­
proach.” As Professor Hatch1 pointed out,
we must continually examine the methods we
use to achieve results. Surely we must go
beyond that and be willing to apply new
techniques to our field whenever it can be
demonstrated that such application will en­
able us to do a better job in conserving the
health of the worker in the industrial environ­
ment. The development of our profession will
depend on how well we integrate the common
interests that each discipline brings to the field
of occupational health. Our progress will also

Tabus II ;

I

Data Summary from a Continuous Environmental Monitor
Department—-chemical plant
Material —methyl chloride
Date
—2/17/59 to 2/23/69
•

Sampling Location
(raw data)

i

2

5

4

s

i

Mean concentration

14.3

29.5

35.S

42.5

61.3

79.3

Standard deviation
Frequency distribution
25 ppm
50 ppm
100 ppm
200 ppm
300 ppm

IS.}

M

19.4

9.1

22.4

21.0

19.5

8.5
1.9
0.5
0.2
0.1

49.4
9.1
0.2
0.0
0.0

60.5
*14

100.0
16.4
n

100.0
100.0
14.5
0.3
0.0

39.6
13.S
11

0.0

100.0
% 51.4
6.7
1.1
0.1

93.5
74.9
45.7
30.7
17.3

66.2
62.7
51.1
43.0
33.4

107.0
98.8
96.1
75.7
47.8

91.6
12.2
63.0
34.9
45.6

164.7
145.0
109.7
94.9
69.8

170.5
150.2
121.4
107.9
87.8

76.2
(7.6
S1.0
41.5
30.5

Maximum concentration
5 minutes
10 minutes
30 minutes
1 hour
4 hours

0.4
0.3

Job Classification

v

A
26.8

0.0

AP00001041

American Industrial Hygiene Association Journal
be measured by how well we find compatible,
systematic methods of using the newest tools
available to each basic discipline in our field.
A systems approach to industrial, health
would help us to take advantage of the tran­
sition we will enjoy with increasing use of
automation, process control, and the digital
computer. From a systems engineering point
of view there is really little difference between
controlling the process and controlling the
work environment associated with it. A logi­
cal point of reference for the transition ahead
would be the Process-Environment System.

239

References
1. Hjmk, T.

In Crellty, L. V.s Miuliul Hytir»«

HighUghU, Vol. I., d, 2, Industrial Hygrieet fousdatioa

®{ America, Inc., Pittsburgh, F*. (limit).

2. Winner’s S*z*ntk New ColUgimlt Dictionary, O, £ C.
Mtrriam Company. Springfield, Matt. (1967).
S. wish, D. D.: Evolution of Our Concept! ot Standards.
Arch. Environ. Htelth 10; >46 (2965),
4. ftmsoM, J. E.» H. R. KoviX, »od E. J. SocKusca:
Hie Appiicaiioo ot Computer Science to Industrial
Hygiene. Amer. 7*4. Hyg. Asia*. J. 27i 180 (1966).
5. Bkarrr.v. E. D., R. D. yuwA»r, and J, E. Mctchlxk:
Monitoring Expoturet to Vinyl Chloride Vapor; Breath
Analysis ana oCntimious Air Sampling. Amcr. 7*4.
Hyg. Aat>c. J. 30; 537 (1969).
6. Hatch, T. F.: Significant Dimension* of the Dose-Re*
Ipome Relationship* Attk. Environ. Httltk 16: 571
(1968).
J. SroKiNOBR, H. E.l Industrial Contribution to Threshold
Limit Values. Arch. Environ. Health 10; 609 (1965).
Received June 9,1969

Gordon Research Conference
The 1970 Gordon Research Conference on Toxicology and Safety Evaluations
will be held at Kimball Union Academy, Meriden, New Hampshire, July 2731. This conference has been of considerable interest to industrial hygienists
for a number of years because of the close relationship of problems encountered
in industrial health work. This year the Chairman is J. Wesley Clayton, Jr. and
Vice-Chairman is Edward D. Palmes. The program is as follows:
July 27. (R. A. Scala, discussion leader): H. H, Cornish, “Serum isozymes
and organ damage”; J. L. Radomski, “The metabolism of 1- and 2-naphthylamine as related to carcinogenesis.” (S. L. Fries*, discussion leader): J. M.
Barnes, “Toxic substances and the nervous system.”
July 28.
(S. Epstein, discussion leader): C. Jacobson, “Test systems for
the reproductive evaluation of mutagens”; D. J. Kllian, "The role of CVtOgeniCS

in evaluating the toxicity of chemical compounds.” (H. V. Mailing, Discussion
leader): C. Valenti, “Effects of psychotropic drugs on mammalian chromosomes
in vitro and in vivo observations."
July 29. (C. H. Hine, discussion leader): R. E. Hodges, “The role of human
studies in evaluating potentially hazardous agents”; L. H. Schmidt, “What
nonhuman primates have taught us relative to the action of chemicals on living
systems.” (Sidney Leskovitz, discussion leader): B. Pemis, “Immunological
problems in toxicology.”
July 30. (W. B. Ennis, discussion leader): D, O. King, “Rational Manage­
ment of the environment”; K. C. Barrons, “Benefits of agricultural chemicals.”
(J. P. Frawley, discussion leader): L. Cole, “The chemical threat to our en­
vironment.”
_ July 31. (E. D. Palmes, discussion leader): T. Foin, “Technology, popula­
tion and the environment.”
Attendance at the Conference is by application only. Application forms and
full information regarding requirements for attendance may be obtained by
writing to Dr. Alexander M. Cruickshank, Director Gordon Research Confer­
ence, Pastore Chemical Laboratory, University of Rhode Island, Kingston,
Rhode Island 02881 (Telephone: 401-783-4011). Applications for this Con­
ference should be submitted before June 1,1970.