Background  Information.
m
II Proposed
H National
 1 Emission
• Standards
   Hazardous
   *•
   Air
   Pollutants:
U. S. ENVIRONMENTAL PROTECTION AGENCY

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  BACKGROUND INFORMATION-
             PROPOSED
 NATIONAL EMISSION STANDARDS
FOR HAZARDOUS AIR POLLUTANTS:

              Asbestos
              Beryllium
              Mercury
       ENVIRONMENTAL PROTECTION AGENCY
          Office of Air Programs
    Research Triangle Park, North Carolina
             December 1971

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Office of Air Programs Publication No.  APTD-0753

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                                           CONTENTS

 ,       INTRODUCTION 	    1
        TECHNICAL REPORT NO.  1  - ASBESTOS  	    3
            Summary of Proposed Standards  	    3
 j~           Effects on Health	-	    3
 *           Nature of Asbestos  Air Pollution Problem  	    5
 \j           Development of Proposed Standards  	    5
\           Economic Impact of  Proposed Standards   	    7
 's.          References	    8
 ,<
 X.       TECHNICAL REPORT NO.  2  - BERYLLIUM	    9
 X         Summary, of Proposed Standards	    9
            Effects on Health	   10
 ^          Nature of Beryllium Air Pollution Problem  	   10
            Development of Proposed Standards  	   12
            Economic Impact of  Proposed Standards   	   13
            References	   14
 »      TECHNICAL REPORT NO.  3  - MERCURY	   15
            Summary of Proposed Standards	   15
 /          Effects on Health	   15
            Nature of Mercury Air Pollution Problem  	   16
            Development of Proposed Standards  	   18
 fa        Economic Impact of  Proposed Standards   	   18
 v>>        References	   21
 <•>-    APPENDIX.   ATMOSPHERIC  DISPERSION ESTIMATES	   23
                                                111

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                                INTRODUCTION

This document provides background information on the derivation of the proposed
national emission standards for asbestos, beryllium, and mercury.   The proposed
standards, published in the Federal Register under Title 36 CFR Part 62,  are being
distributed concurrently with this document.  The information presented herein was
prepared for the purpose of facilitating review and comment prior  to promulgation
of the standards.

The proposed national emission standards were developed after consultation with
appropriate advisory committees, independent experts, and appropriate representa-
tives of the Federal government.  The National Air Quality Criteria Advisory Com-
mittee has been consulted on air quality considerations, the assessment of adverse
effects, and the approaches and protective philosophy underlying the proposed
standards.  Members are outstanding scientists and/or administrators concerned with
the quality of the environment and resident in universities, State or local  govern-
ments, research institutions, or industry.  They are selected for  their recognized
expertise and/or interest in the establishment of air quality criteria or for their
recognized expertise in the evaluation and interpretation of scientific evidence
indicative of adverse and preventable effects of atmospheric pollutants.

Review meetings were held with the Federal Agency Liaison Committee and the National
Air Pollution Control Techniques Advisory Committee.  The proposed standards reflect
consideration of comments provided by these committees and by other individuals
having knowledge regarding the control of these pollutants.

The National  Air Pollution Control  Techniques Advisory Committee is made  up  of 16
persons who are knowledgeable concerning air quality, air pollution sources, and
technology for the control of air pollutants.  The membership includes state and
local  control officials, industrial representatives, university professors,  and
engineering consultants.  Members are appointed by the EPA Administrator  pursuant to
Section 117 (d), (e), and (f) of the Clean Air Act of 1970, Public Law 91-604.  In
addition, persons with specific expertise regarding these pollutants participated in
the meeting of the Advisory Committee.

The Federal Agency Liaison Committee includes persons knowledgeable concerning air
pollution control practices as they affect Federal  facilities and  the nation's
commerce.  The committee is made up of representatives of 19 Federal  agencies.

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The promulgation of national  emission standards for asbestos, beryllium,  and mercury
under Section 112 of the Clean Air Act does not prevent state or local  jurisdictions
from adopting more stringent emission limitations for these pollutants.   Further-
more, the promulgated standards themselves may require revision from time to time
because of the development of additional  technical  information.

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                      TECHNICAL  REPORT NO.  1  -
                                  ASBESTOS
SUMMARY OF  PROPOSED STANDARDS
Because routine, standardized  techniques for sampling and analyzing asbestos emissions
are not available,  the  proposed standards for asbestos are not  given  in terms of
numerical values.   Instead,  the standards are expressed in terms  of required control
practices that limit emissions to an acceptable level.  In part,  control of atmos-
pheric emissions would  be  achieved by:

     1.  Utilizing  industrial  fabric filters to clean forced  exhaust  gases from
         asbestos mining,  milling, and manufacturing industries and from fabricating
         operations that involve materials containing asbestos.

     2.  Eliminating visible emissions of particulate matter  from ore dumps, open
         storage areas, external conveyors, and tailing dumps associated with
         asbestos mining and milling facilities as  well as from manufacturing and
         fabricating operations carried out with asbestos-containing  materials in
         areas directly open to the atmosphere.

     3.  Prohibiting certain applications of asbestos fireproofing and insulation
         by spraying processes.

Also, indirect atmospheric emissions of particulate matter would  be controlled at
manufacturing and fabricating  sites where visible emissions normally  result from
operations using commercial  asbestos.  The maximum  allowable  emissions would be
equivalent to those attained by either ventilating  an entire  work space through a
fabric filter or by hooding  emission sources and subsequently passing the required
dust-control  air through a fabric filter.

EFFECTS  ON HEALTH
The inhalation of asbestos fibers has been related  to a number  of human diseases.
Among these is asbestosis, which has been related to occupational exposures and is
characterized by interstitial  fibrosis, pleural fibrosis, and pleural calcificationJ

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It is presently thought that exposure to asbestos concentrations much larger than
those likely to be present in community air is required for the development of
clinically significant asbestosis.1

Calcification of the pleura, which has been noted in asbestos workers, typically
occurs after an extended period of time following exposure and is frequently accom-
panied by pulmonary fibrosis, i.e.,  asbestosis.  The asbestos dosage that causes
pleural calcification has not been established; however, nonindustrially exposed
populations have exhibited substantial incidences of such disease.^>3

It has been recognized since 1947 that among industrial employees asbestos workers
have an increased risk of bronchogenic carcinoma.   For populations exposed to
asbestos only in ambient air, there  are no data that define the excess risk, if any,
of developing this disease.

An association between asbestos exposure and mesothelioma, a fatal malignant tumor
of the pleura and peritoneum, was established in 1960 by a study of 33 cases of
mesothelioma in South Africa.   Seventeen of the patients were occupationally
exposed, and 15 resided in the vicinity of an asbestos mine.  No history of asbestos
exposure was discovered for one patient.  A subsequent study of mesotheliomal
malignancies identified patients with minimal or no known exposure to asbestos. The
existence of a prolonged period, averaging 40 years, between initial exposure and
appearance of a mesotheliomal tumor  complicates the study of this disease.  There
are no data that specify the minimum amount of asbestos exposure associated with
an increased risk of developing mesothelioma.

A quantitative definition of the asbestos air pollution problem can not be formulated
at this time because of the lack of a dose-response relationship between levels of
airborne asbestos and the resulting  human diseases.  Nevertheless, available evidence
clearly implicates asbestos as a serious air pollution threat.  This evidence includes
the discovery of asbestos fibers in lungs of nonoccupationally exposed persons,  the
                                                                          c
qualitative demonstration that asbestos fibers are present in ambient air,  and the
cited epidemiologic studies relating asbestos exposure to disease.

Research efforts directed toward the establishment of a dose-response relationship
for human exposure to airborne asbestos are in progress.  The only measure available
at this time to protect the public health from airborne asbestos is to control
asbestos emissions to the greatest degree practicable for the following reasons:

     1.  A safe exposure level to asbestos has not been established.

     2.  Exposure to asbestos in community air may produce disease.

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     3.  The consequences of asbestos-caused  disease  can  be extremely serious.

NATURE OF ASBESTOS AIR  POLLUTION  PROBLEM
Asbestos fibers enter the atmosphere from a wide  variety  of sources extending from
the weathering and disturbance of natural  deposits  of asbestos-bearing materials to
operations for the ultimate disposal of products  containing asbestos.  Intermediate
emission sources include asbestos mining  and  milling  sites, manufacturing facilities
for asbestos-containing products, and construction  sites  employing asbestos insulat-
ing, fireproofing, and structural materials.   More  than 3,000 products contain
commercial asbestos.  As these products are used, asbestos is frequently emitted to
the atmosphere.  Among these products are automotive  brake linings and asbestos-
asphalt concrete for paving roadways.  Asbestos is  also present as a natural contam-
inant in some widely employed materials,  such as  talc.  The asbestos emissions from
use of these materials can be significant.

Because asbestos is exceptionally resistant to thermal degradation and chemical
attack, settled particles are persistent  in the environment and subject to reentrain-
ment into the atmosphere.  It can readily be  mechanically subdivided into fibers of
submicron diameter, which can remain airborne for long periods of time.  These
factors, coupled with the presence of large numbers of emission sources, as noted
above, would indicate the presence of a background  level  of asbestos in the atmos-
phere.  Semiquantitative data confirm this conjecture and  show that urban background
concentrations are significantly larger than  nonurban ones.

Asbestos emissions are now being controlled to a  limited  extent, primarily from
milling and manufacturing sources to which gas-cleaning devices are readily appli-
cable.  The formulation of recommended codes  of trade practices governing such
operations as the transport,  fabrication,  application, and disposal of asbestos-
containing materials has not proved to be  an  effective emission control technique.
Control of asbestos emissions from some sources,  for  example, spray-applied asbestos
fireproofing, has been made possible by the use of  substitute materials for asbestos.
It is also true, however, that there is interest  in expanding the already vast
number of applications for asbestos fibers.

DEVELOPMENT OF PROPOSED STANDARDS
The intent of these proposed  standards is  to  minimize asbestos emissions into the
atmosphere from all clearly identifiable  stationary sources, subject to the avail-
ability of a sufficiently definitive characterization of  emissions from such sources
and subject to the availability of feasible control techniques.  Where practical,
these control techniques include direct prohibition of activities that generate
asbestos emissions.

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Asbestos mining and milling operations produce much larger total  atmospheric
emissions of asbestos than any other single domestic source category and would be
regulated by these standards.   Several specific manufacturing operations that
incorporate commercial asbestos into products have been identified as significant
emission sources.   These, as well as the numerous manufacturing  facilities for
other asbestos-containing products, would be subject to these proposed standards.
From among the many end uses of asbestos-containing products, a relatively small
number has to date been singled out as contributing significantly to the overall
problem of air pollution.  The field fabrication of asbestos-bearing products,
particularly insulating materials, and the spray application of asbestos fire-
proofing are two specific end uses that would be controlled by the proposed stand-
ards.  The direct limitation of asbestos emissions from mobile sources, such as those
associated with the wearing of automotive brake linings, the transport of asbestos-
containing materials, and the dispersion of powdery asbestos-bearing materials from
vehicles, lies outside the authority of Section 112 of the Clean  Air Act.  A program
for determining the extent and nature of asbestos emissions from  automotive brake
linings is now in progress in the Office of Air Programs.   Other  asbestos emission
sources are now under study for possible inclusion within proposed standards at a
future date.  Included in these studies are roadways paved with asbestos-asphalt
concrete and talc mines, in which asbestos occurs as a natural contaminant.

Current standardized measurement techniques for asbestos, namely those for testing
occupational asbestos exposures, are not designed for isokinetic  sampling, which is
necessary for the determination of the asbestos content of forced-gas streams.
Further, these methods fail to take into account large numbers of asbestos fibers
present in the samples. At least three ambient air sampling and analysis techniques,
which employ electron microscopy to render visible even the smallest asbestos fibers,
are currently undergoing development.  To date, these methods are capable of provid-
ing estimates of asbestos mass concentrations, but not number concentrations of
asbestos fibers in unprocessed samples, and reproducibility of results obtained by
the three methods has not been established.  Until these new techniques are perfected,
emission control must be based upon the best feasible control technology.  Accordingly,
the proposed standards would require the operation of specified control equipment.
Fabric filtering devices have been specified as the mainstay of these standards
because they possess (1) demonstrated high-efficiency collection across a wide
range of solid particulate sizes and (2) reasonable investment and operating costs.
It is prudent to require control techniques that provide high collection efficiency
for submicron-size particulates because research studies have shown that the
largest number of asbestos fibers in emissions generated by some industrial

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operations is concentrated in the range of smallest particle sizes.   Many fabric
filters are already in service at asbestos milling and manufacturing facilities,
and some operations routinely recycle filter-cleaned air for ventilation of work
spaces.  In exceptional operations amenable to emission control  by gas cleaning,
but where technical difficulties preclude the application of fabric  filters, these
standards would permit the use of other control equipment of somewhat lesser
efficiency.
The proposed regulations that would prohibit visible emissions apply to  sources  not
readily controlled by gas-cleaning devices.  Flexibility with regard to  choice and
development of the most effective control  techniques would be provided  in  that the
proposed standards would not specify control equipment.   The exception  of  uncombined
water from the prohibition would be made to accommodate  situations  in which  water
would be used as a control medium.  Processes that are properly operated could be
controlled by feasible techniques to secure compliance.
The surfacing and resurfacing of roadways with asbestos tailings  would  be  banned
because of the probable ineffectiveness of control  measures during  both application
and an extended period of usage.  The proposed ban  on the spray application  of
products that contain asbestos is based upon experience with spray-fireproofing
operations wherein efforts to control emissions by  the use of containment  and good
housekeeping practices have repeatedly failed.  Several large municipalities in the
United States have already put into effect procedures that exclude  the  use of
sprayed asbestos materials.  Asbestos-free substitute materials are available for
both sprayed asbestos fireproofing and high-temperature asbestos  insulation,


ECONOMIC IMPACT  OF  PROPOSED STANDARDS
The basic processing of domestic asbestos ores is carried out in  nine mills  with  pro-
duction capacities ranging from 200 to 65,000 tons  per year.  These mills  produce
approximately one-sixth of the total consumption of asbestos in the United States.
The estimated additional annualized costs required  of these existing sources for  com-
pliance with the proposed standards range from zero to $5.96 per  ton of asbestos
fiber produced per year; this represents a range of zero to 6.7 percent of the
average selling price per ton of domestically produced asbestos in  1969.   The
average investment, for the entire industry, is estimated to be $0.78 (0.9 percent)
per ton of asbestos fiber produced per year.  Actual  investments  range  from  $2,780
for an essentially uncontrolled mill of 200-ton/year capacity to  $183,000  for a
partially controlled mill  of 40,000-ton/year capacity.

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For the major categories of industries that manufacture products  containing  com-
mercial asbestos, i.e., producers of asbestos-cement products,  asbestos-containing
floor tile, asbestos-reinforced friction materials, asbestos paper,  and  asbestos
textiles, a total additional  investment of $5,281,000 is estimated  to  be required
to bring existing, partially controlled sources into compliance with the proposed
standards.   This represents an investment of 0.6 percent of the total  value  of
product output, or an annualized cost of 0.3 percent of the output  product value.
In terms of alterations in product price, there would result an average  increase
of 0.3 percent; the most significant increase would be 2.6 percent  for asbestos
paper products.
The use of asbestos in spray-applied fireproofing and insulation  represents  only
approximately 0.5 percent of the annual domestic consumption of asbestos.  No
major impact on the price of asbestos or upon producers of asbestos  would result
from the prohibition on spray application of asbestos fireproofing  and insulation.
Further, increased costs for substitute materials, available or scheduled for  intro-
duction in the near future, range from zero to a maximum of 15  percent.   The use of
these asbestos-free substitute materials does not require new equipment  or extensive
retraining of personnel.

REFERENCES
1.  Airborne Asbestos.  National Academy of Sciences.  Washington,  D.C.   1971.

2.  Kiviluoto, R.  Pleural Calcification as a Roentgenologic Sign of Non-Occupational
    Endemic Anthophyllite-Asbestosis.  Act. Radiol., Suppl. 1,  194_:l-67, 1960.

3.  Zolov, C., J. Bourilkov, and L. Babjov.  Pleural Asbestosis in Agricultural
    Workers.  Environ. Res.  1(3):287-292, 1967.

4.  Merewether,  E.R.A.  Asbestosis and carcinoma of  the lung.  In:   Annual  Report  of
    the  Chief  Inspector of Factories  for  the Year  1947.  London:   H. M.  Stationary
    Office, 1949.  79  p.

5.  Sullivan, R.J. and Y.C. Athanassialis.  Preliminary Air Pollution Survey of
    Asbestos.  DREW, PHS, CPEHS, National Air Pollution Control Administration.
    Raleigh, N.C. Publication No. APTD 69-27.   1969.

6.  Asbestos.  In:  National  Inventory of Sources  and Emissions.   W. E.  Davis  and
    Associates.   Leawood, Kansas.  Report to National Air Pollution Control  Adminis-
    tration.   Durham,  N.  C.   Contract No. CPA 22-69-131.  February  1970.  46 p.

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                      TECHNICAL  REPORT  NO.  2  -

                                  BERYLLIUM
 SUMMARY  OF PROPOSED  STANDARDS
The proposed  beryllium  standards are designed to protect  the  public from 30-day
average atmospheric  concentrations of beryllium greater than  0.01 microgram per
cubic meter (pg/m^).  Experience over more than 20 years  has  shown this to be a safe
level of exposure.   For short-term, periodic exposures, the safe level has been
determined to be  25  yg/m^ for a maximum of 30 minutesJ  This periodic exposure
limit is the  basis for  the standard pertaining to rocket-motor firings.

The proposed  beryllium  emission standards for extraction  plants, machine shops,
foundries, ceramic plants, propel 1 ant plants, and incinerators designed or modified
for disposal  of toxic substances allow the operator to demonstrate compliance with
either 1 or 2 below:
      1.   No  more than 10 grams of beryllium emitted per  24-hour day.
      2.   No  emission that will cause atmospheric concentrations of beryllium to
          exceed an average of 0.01  microgram per cubic meter  of air for 30 days.

The beryllium emission  standards given below are being proposed for rocket-motor
test facilities:
      1.   No  emissions that will  cause atmospheric concentrations of beryllium to
          exceed 75 microgram-tninutes per cubic meter  of  air*  within the limit of
          10  to 60 minutes.
      2.   No  more than 10 grams of beryllium will  be emitted  per 24-hour day when
          rockets are fired into a tank and  the exhausts  are  gradually released.
Two methods of sampling will be used to determine compliance: sampling of individual
stacks or industry-operated networks sampling ambient  air.  The method used must be
approved by the Administrator of the Environmental Protection Agency  (EPA).  If
*Defined as the product  of  the concentration (in yg/m )  and duration of exposure
(in minutes).

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stack sampling is used, tests will  be conducted each 90 days.   Where  outside  net-
works are used, sampling will be continuous and filters will  be collected every 4
days unless otherwise approved by the Administrator.  When  it is the  opinion  of the
Administrator that the standards will not be exceeded, a waiver of  stack-sampling
requirements can be granted.

EFFECTS ON HEALTH
The adverse effects of airborne beryllium on human  health were  first  recognized in
1940 as a result of the occurrence  of lung disease  in  occupationally  exposed  workers.
Beryllium workers develop two forms of lung disease.  One form,  an  acute chemical
                                                           p
pneumonitis, has been observed, with one reported exception,  only  in workers who
were occupationally exposed to beryllium.   The  chronic form,  berylliosis - a  pro-
gressive, interstitial, granulomatous disease located  primarily in  the alveolar
walls - has been observed in  individuals who have never been  occupationally exposed
to beryllium.   Of the 60 people with non-occupationally incurred disease whose cases
are on file with the Beryllium Registry, 27 were exposed to beryllium by washing
clothes soiled with beryllium dust.  Another 18 were exposed  to beryllium in  the
form of air pollution surrounding beryllium plants,  13 were exposed both to polluted
air and contaminated clothing, and  the exposure of  the remaining 2  was unknown.3

Most of the cases of berylliosis involved exposure  to  beryllium at  a  time when its
hazard was not recognized and its concentration in  the air was  not  measured.  Retro-
spective estimates of the concentrations of beryllium  that resulted in some cases of
berylliosis from non-occupational exposure have been made.  The report of this work
states:  "It may therefore be concluded that the lowest concentration which produced
disease was greater than 0.01 microgram per cubic meter and probably  less than
                                A
0.10 microgram per cubic meter."

In 1949, a guideline limit for beryllium concentrations in  community  air was  devel-
oped by the Atomic Energy Commission (AEC).^  The concentration selected was  an
average of 0.01 microgram of beryllium per cubic meter of air for 30  days.  In the
period since the implementation of this guideline,  no reported  cases  of chronic
beryllium disease have occurred as a result of community exposure.^  Consequently,
the Committee on Toxicology of the National Academy of Sciences has concluded that
the average concentration 0.01 yg/m^ for 30 days has proved to  be a safe level of
exposure.  Therefore, an average of 0.01 vig/m^ for  30 days  should be  used as  a guide
in developing emission standards.

NATURE OF BERYLLIUM AIR POLLUTION  PROBLEM
Emissions of beryllium from the sources covered by  these standards  occur as dust,
fume, or mist.  Alteration of a beryllium product by burning,  grinding, cutting, or
10

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other  physical means can,  if uncontrolled, produce a significant toxicological
hazard.   In  contrast,  beryllium alloys., in the form of strip or other wrought pro-
ducts  are utilized  in  operations that  do not generate dust, fume, or mist.  The
number of operations that  use  beryllium is estimated to be in the thousands.
Approximately 300 operations such as machine shops, ceramics plants, propellant
plants, extraction  plants, and foundries comprise the major users of beryllium that
could  cause  emissions  to the atmosphere.

The distribution of the sources of  beryllium is such that dangerous levels have not
been recorded except in a  few  instances.  Data from the National Air Surveillance
Networks do  not show the existence  of  dangerous levels.

Beryllium extraction plants, in present practice, determine effectiveness of control
of emissions by measuring ambient air  concentrations at various points in the vicin-
ity of the plants.  For control of wet chemical  processes, scrubbers, packed towers,
organic wet collectors, and wet cyclones are used.  In dry operations, cyclones and
fabric-filter units are often used.   The following are typical  air management
practices:

     1.  Local pickup  of contaminated  exhaust from fully enclosed sources.

     2.  Tandem use of primary and  secondary air-cleaning devices; the former is
         used mainly to take reactive  gases and easily removable contaminants out
         of  the exhaust air, and the latter is used to provide high-efficiency
         cleaning.

     3.  Use of high-energy wet collectors (or scrubbers) to obtain high particle-
         collection efficiency (in the removal  of corrosive, wet, and/or hygroscopic
         contaminants).

     4.  Application of fabric tube filters for high-efficiency cleaning.


All  extraction plants have the control  equipment necessary to keep ambient concen-
trations below 0.01  ug/m .   Regardless  of plant  size and type of beryllium operation,
the target concentration of 0.01  yg/m  has been  achieved readily.   Operators of
extraction plants indicate that their experience in  operating government-owned
beryllium plants under contract with the AEC within  the 0.01  ambient air level,  and
voluntarily maintaining the same level  of control  in their own  private facilities,
has  demonstrated that the required  ambient air  level  can be met in an economically
feasible manner.   Results obtained  from sampling sites  in the vicinity of plants
                                                                                   11

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                                                                    o
show that all extraction plants are in compliance with  the  0.01  ng/m  standard or
are very close to it.

In industries other than primary extraction plants,  the control  devices applied are
usually dry collectors and a variety of pre-filter and  high-efficiency particulate
air (HEPA) (or absolute) filter equipment.   Examples of the most thorough emission
control practices may be found among ceramic manufacturing  plants, machine  shops,
and propel 1 ant fabricating facilities.  In  many of these industries, air-cleaning
equipment includes primary fabric tube filters  followed by  secondary HEPA filters,
or dry collectors followed by pre-filter/HEPA filter units.   Arrangements sucji as
these are among the most effective in reducing  beryllium emissions.  The most poorly
controlled operations occur in foundries and in shops that  occasionally machine
beryllium metal, alloy, or ceramic materials.

Since 1966, emissions from the firing of rockets utilizing  beryllium as a propel!ant
have been limited by PHS policy; since 1967, they have  been limited  as well  by DOD
directive. '   Both agencies direct that 75 microgram-minutes of beryllium  per cubic
meter of air not be exceeded.  Both also suggest that rockets be fired into  contain-
ment vessels if possible and, if not, that  they be controlled by other positive
engineering methods, such as the use of scrubbers.

DEVELOPMENT OF PROPOSED  STANDARDS
The sources covered by these standards, if  not  controlled,  can potentially  release
                                                                            3
amounts of beryllium that will produce concentrations greater than 0.01 ug/m in
the ambient air.  No source known to have caused, or to have  the potential  to cause,
dangerous levels is excluded from these standards.

Other sources of beryllium emissions to the atmosphere  exist  that are  not included
in the standards.  The beryllium content of coal varies, but  most coal contains from
1 to 2 parts per million (ppm).  Present knowledge indicates  that coal-fired power
plants do not produce hazardous levels of beryllium in  ambient air.  Beryllium
emissions from coal combustion have recently been and will  continue  to be documented
by source testing.  As additional sources of beryllium  are  discovered, the  magnitude
of their emissions will be evaluated and, if necessary, that  source  will be included
among those covered by these standards.

Considering dispersion estimates, number and type of emission sources  per facility,
and average fence-line distances, a maximum emission of 10  grams of  beryllium per
day provides assurance that a concentration of 0.01  microgram of beryllium  per cubic
meter of ambient air will not be exceeded.   Limiting the beryllium concentrations  in
ambient air to 0.01 ug/m3 has proved successful in protecting community populations
from beryllium-caused disease since this limit was proposed in 1949.
12

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Contacts made by EPA have indicated that the control  systems required to meet this
standard are already in use in many facilities.  For example, one machine shop emits
0.4 gram per day; another large machine shop, which uses absolute filters, exhausts
its air at concentrations below 0.01 yg/m^; and a third machine shop exhausts 5,000
cubic feet per minute, with a concentration of 2 pg/m-3 of exhaust, for a total emis-
sion of less than 0.3 gram per day.  At least 20 of the operations contacted use
absolute filters as a final cleaner.

ECONOMIC IMPACT  OF PROPOSED STANDARDS
In order to assess properly the economic impact of the beryllium standards, it must
first be understood that the major portion of the beryllium industry already has
the emission controls necessary to comply with the standards.  This level  of con-
trol has been the result of recommendations issued in 1949 by the Beryllium Medical
Advisory Committee to the AEC.   Compliance with the AEC recommendations has been
required of all government facilities and government contractors.  Other beryllium
operators generally accepted them to protect themselves and their employees.

The cost of controlling beryllium emissions varies with the nature and size of the
operation.  In most cases, the percentage of capital  costs allocated for control of
emissions should approximate the values listed below:

                    Source                Percentage of capital cost
               Foundries                             13.0
               Ceramic plants                        19.0
               Machine shops                          8.0
               Extraction plants                     12.0

These percentages include all  ventilation equipment inside the plant, some of which
is necessary for good industrial hygiene.  Because good inside control  of emissions
is necessary in all  beryllium operations, it is difficult to separate emission con-
trol costs from the  cost of controlling the inside atmosphere.  For this reason, the
stated costs of beryllium emission control  are deceptively high.

The beryllium emission standards will  have little economic impact on the industry.
In addition to the fact that most of the potentially dangerous sources  are already
controlled, the beryllium collected in control  equipment can in some cases be sold
to the primary extraction plants for reprocessing.

Foundries may have to add control  equipment and install  stacks suitable for stack
testing.   Control  equipment is generally lacking, but in most cases emissions do not
exceed the proposed  standards.  In any case, beryllium is an expensive  material and
the cost of control  is low in  terms of consumer prices.
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REFERENCES
1.  Air Quality for Beryllium and Its  Compounds.   National Academy of Sciences,
    National Research Council.  Washington,  D.  C.   March  1966.

2.  Shipman, T. L. and A.  0.  Vorwald.   History  of  Beryllium  Disease.  In:  Beryllium:
    Its Industrial Hygiene Aspects.   Stokinger, H.  E.  (ed.).  New York, Academic
    Press.  1966.   p. 14.

3.  Hardy, H.  L.,  E.  W. Rabe, and S.  Lorch.   United States Beryllium Case Registry
    (1952-1966).  J.  Oecup. Med. £:271-276,  June 1967.

4.  Eisenbud,  M. et al.  Non-occupational  Berylliosis.  J. Ind.  Hyg. Toxicol.
    31:282-294, 1949.

5.  Stokinger, H.  E.   Recommended Hygienic Limits  of Exposure to Beryllium.   In:
    Beryllium:  Its Industrial Hygiene Aspects. Stokinger,  H.  E. (ed.).  New York,
    Academic Press.  1966.  p. 236.

6.  Memoranda, "Control of Air Pollution Associated with  Beryllium-Enriched  Propel-
    lents," April  7, 1967, and November 20,  1967,  issued  by  Director of Defense
    R. and E.

7.  Statement of PHS Policy on the Use of Beryllium as  an Ingredient of Rocket Pro-
    pellants.   Department of Health,  Education, and Welfare,  Public Health Service.
    December 21, 1966.
 14

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                        TECHNICAL REPORT  NO. 3 -
                                   MERCURY
 SUMMARY OF PROPOSED STANDARDS
The proposed standards  are  intended to protect the general  public from adverse health
effects contributed to  by  inhalation of atmospheric mercury.   Mercury-cell chlor-
al kali plants  and primary mercury mines will be regulated  by  the proposed standards.
Each facility  of these  two  industries may not emit more than  5 pounds of mercury
into the atmosphere during  a  24-hour period.

The monitoring requirements of  the proposed standards at each facility will be based
on EPA-approved sampling and  analytical techniques, and such  measurements will be
made at intervals of 90 days.   All emission data, records  of  required operating
parameters existing at  the  time of emission measurement, and  operating records neces-
sary to estimate the emissions  from the facility during each  90-day period must be
kept on file for inspection for a minimum of 2 years.

The above monitoring requirements may be waived by EPA if  a facility installs and
institutes control  techniques and housekeeping procedures  that EPA deems adequate
for meeting the standards.

EFFECTS ON HEALTH
It has been stated  that most mercury compounds degrade to  elemental mercury under
the action of  sunlight.   Consequently, most atmospheric mercury is probably chiefly
                                          2
elemental mercury in vapor or aerosol form.   Airborne mercury may be inhaled
directly by man or  it may settle out of the atmosphere or  fall  with rain.  It has
been demonstrated  that man will absorb 75 to 85 percent of inhaled mercury vapor at
concentrations of 50 to 350 yg/m .  Lower concentrations may  be absorbed more
           4
completely.

The central nervous system  is the critical focal  point in  long-term exposure to
mercury vapor.    The vapor  is absorbed into the blood from the lung where some of it
remains unchanged,  and  some is  oxidized to mercuric ions,  a form whose action
results in damage.   Elemental mercury is 1ipid-soluble and  can, therefore, diffuse
                                         15

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into the central  nervous system and similar tissues  where more of  it  is oxidized to
mercuric ions.  Mercury can accumulate in  the  brain, testes,  and thyroid because its
elimination from these sites is slow.

In cases of chronic exposure to mercury vapor,  symptoms  indicating central nervous
system involvement are most commonly seen,  the  principal features  being tremor and
psychological  disturbances.   In addition,  loss of appetite,  loss  of  weight, and
insomnia have been reported.

In order to determine the level of mercury  in  the ambient air that does not impair
health, the airborne burden must be considered  in conjunction with the contribution
of mercury from water and food.  Swedish experts have concluded that  an intake of
30 ug/day of methyl mercury is safe.   An  intake, however,  of ten  times that amount,
or 300 ug/day, of methyl mercury can be expected to  produce symptoms  in the most
sensitive humans. '   In a study of occupational exposures,  a similar intake of
mercury vapor was found to have some subtle effects, such as  loss  of  appetite and
loss of weight.  Because similar intakes of methyl mercury  and mercury vapor appear
to produce detrimental effects, exposures  to methyl  mercury (diet) and mercury vapor
(air) will be considered equivalent.

Data on the dietary (food and water) intake of mercury are  scarce.  Recent estimates
in Sweden and the United States make some  generalizations possible, however.  Diets
containing fish contaminated to the FDA limit  (0.5 yg/g) would lead to intakes in
excess of 30 ug/day of mercury, a problem  which must be  resolved.  From average diets,
however, over a considerable time period,  one  could  expect  mercury intakes of about
10 ug/day, thus the average mercury intake from air  would have to  be  limited to
20 yg/day if the average total intake is to be restricted to  30 yg/day.

Assuming inhalation of 20 cubic meters of  air  per day, the  air could  contain an
                                                     3
average daily concentration of no more than 1  ug Hg/m .  Because chronic health
effects occur with long-term exposure, emission standards should be designed to
restrict air concentrations to a daily concentration, averaged over 30 days, of
         o
1  yg Hg/m.

NATURE OF MERCURY AIR  POLLUTION PROBLEM
Mercury, although a scarce metal, is widely distributed  throughout the earth's crust
and hydrosphere.   Because of its high volatility, emissions of mercury emanate from
any source where mercury is exposed to the  atmosphere or where any material bearing
mercury is processed.  Some major sources  of atmospheric mercury are  considered to
be coal-fired power plants, paint, primary non-ferrous smelters, incinerators, mercury-
cell chlor-alkali plants, primary and secondary mercury-processing plants, and general
laboratories and hospitals.
 16

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Mercury and its compounds enter the atmosphere through emission in the form of
vapors and particulates from industries and also by evaporation from soil and water.
Once in the atmosphere, mercury is widely transported by wind currents.  Eventually,
some of the atmospheric mercury returns to the earth's surface as settleable partic-
ulates, but most of it returns with rainfall.  Because the mercury that falls on
soil does not penetrate deeply, it can re-enter the atmosphere by evaporation or
wash off into an aqueous system.  Other ways by which mercury can gain entrance into
aquatic systems are through settleable particulates, rainfall, and soil erosion.
After entering the hydrosphere, all forms of mercury appear to be directly or indi-
rectly capable of being converted by bacteria to highly toxic methyl  and dimethyl
mercury.  The solubility of methyl mercury in water causes it to be incorporated
into the body tissues of aquatic life forms and, ultimately, into the human food
chain.  Dimethyl mercury can evaporate from the water system and re-enter the
atmosphere.

As is readily seen from the foregoing discussion, mercury is extremely mobile in the
environment.  Natural processes such as methylation, evaporation, and solution pro-
vide means for mercury compounds to cycle between air, water, and land for an indef-
inite period of time.  Atmospheric mercury is not only a local inhalation hazard,
but can contribute to contamination of food and drinking water or produce hazards
in other ecological systems.

Currently there are few existing data concerning atmospheric concentrations of
mercury.  Those data that do exist, however, indicate that a concentration of
         3
1  yg Hg/tn  may be approached, on a 24-hour basis, in large industrial cities.  The
measurement of mercury and its compounds in ambient air and from industrial-plant
effluents has only recently received attention; as a result, measurement methodology
is in a state of evolution.

Few industries currently control atmospheric mercury emissions solely for the sake
of protecting public health.  In general, economic reasons have dictated the use of
those mercury emission controls that are employed.  In the primary and secondary
mercury industries, process efficiency improves with lower mercury emissions, there-
by making reduction of mercury emissions profitable.  Some primary non-ferrous
smelters collect mercury from their gaseous effluents as a by-product.  The basic
control method employs condensation to remove mercury from a gas stream.  The amount
of cooling accomplished depends on the temperature of the ambient air and available
cooling water.  In the mercury-cell chlor-alkali industry, the hydrogen stream is
cooled to collect valuable mercury that must be replaced if atmospheric losses
occur.  In certain cases, the hydrogen stream is either treated further with impreg-
nated activated carbon or cooled to very low temperatures and sold as a by-product
                                                                                   17

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 to the chemical  industry.  The mercury concentration in the chlor-alkali  cell  room
 is controlled  to less  than 100 yg/m  , as recommended by the National  Conference of
 Governmental  Industrial  Hygienists (NCGIH), to protect operating personnel  from
 mercury poisoning.   The  control  is maintained by dilution of the cell-room  air with
 large ventilation flow rates, resulting in sizable atmospheric emissions  from  the
 cell  rooms.
DEVELOPMENT OF  PROPOSED STANDARDS
Considering dispersion estimates,  number and type of emission sources per facility,
and average fence-line distances,  a  maximum emission of 5 pounds of mercury per day
provides assurance that a concentration of 1 microgram per cubic meter of ambient
air will not be exceeded.  This level  will protect the public from adverse health
effects due to inhalation of mercury.  A meteorological derivation is given in the
Appendix.  Of the major sources of mercury emissions, mercury-cell chlor-alkali
plants and primary mercury-processing  plants are the only two that are known to be
emitting mercury in quantities and in  a manner  that will cause the ambient air con-
centration of mercury to exceed 1.0  ng/m3  (assuming a negligible background level).
The proposed standards can be achieved, however, with existing technology in both
the chlor-alkali and primary mercury industries.  Additional control of mercury
emissions from the primary industry  can be achieved by cooling the effluent gases to
lower temperatures.  The additional  cost incurred would put unbearable economic
burdens on an already declining industry.  Additional control of mercury emissions
for the chlor-alkali industry is  not feasible at this time.  The cell room, which is
responsible for the largest emissions  from a chlor-alkali plant, is not readily
adaptable to existing control methods  because of the low mercury concentration con-
tained in the large volumetric flow  rate of cell-room ventilation systems.

Currently, work is  in progress to determine additional mercury sources and the
extent of mercury emissions to the atmosphere.  Operators of those  plants suspected
of being sources of atmospheric  mercury emissions will  be required  to submit the
information necessary for quantifying  mercury  emissions from their  operations.
 ECONOMIC IMPACT OF  PROPOSED STANDARDS
 There are no  known state regulations that control specifically the emissions of
 mercury  to  the atmosphere or control ambient-air levels of mercury.   The  City  of
 New  York, however, has revised its 1964 Code of City of New York,  Article 9, to
 state:   "No emission of air contaminants containing cadmium, beryllium, and mercury,
 or any compounds thereof, are allowed."  This law became official  on August 21, 1971,
18

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                                               3
Zero emission of mercury is defined as 0.1 yg/m , or less, of effluents.   Further-
more, the State of Wisconsin has issued a legal order to a mercury-cell  chlor-
al kali plant to reduce its total mercury emissions from both the hydrogen and end-
box-ventilation gas streams to less than 0.9 pound of mercury per day.   Although
the order did not regulate the amount of mercury in the ventilation effluents from
the cell room, mercury emissions from this source must be compatible with the present
Occupational Health Standard of 100 yg/m .  The proposed Federal standard of
5 pounds of mercury per 24-hour period may require the chlor-alkali plant in
Wisconsin to improve its present control.  The proposed Federal  standards should
have no impact on the standard for mercury emissions set by the City of New York
since the latter is more restrictive than the former.

Since mid-1970, the consumption of mercury in chlor-alkali plants, agricultural  use,
and paper industries has been reduced, largely because mercury emissions  from these
users were thought to contribute to environmental  pollution.  The total  use of
mercury has decreased by more than one-third of the consumption for the same period
in 1969.  A decrease in the price and production of mercury has followed  the decrease
in consumption.

Average primary mercury production has dropped from 29,640 flasks in 1969 to 27,303
flasks in 1970, and to 7,900 flasks in the first two quarters of 1971.   Average
price per flask of mercury was $505 in 1969, $405 in 1970, and $286 in the second
quarter of 1971.  The August 1971 price was $295 per flask.  Marginal prices required
for production range from $360 to $400 per flask for underground operations, and from
$270 to $300 for open-pit operations.  Current prices are so far below marginal  costs
that all but a few primary mercury mines have abandoned production.  As a result, the
number of mercury mines in operation has dropped from 109 in 1969 to fewer than 10 in
August 1971.

A mine processing 100 tons of ore per day has a capital investment of $300,000 to
$400,000 in its processing equipment and produces mercury valued at an average of
$518,000 per year.  The amount of mercury emitted is estimated to be a minimum of
4 to 35 pounds per 24-hour day.  Control devices to limit mercury emissions to
5 pounds per day require a capital investment of $38,000 to $42,000 and a yearly
operating or annualized cost of $12,500 to $18,000.

The capital required for control devices for mercury mines is approximately 10 per-
cent of the total capital investment for processing equipment.  The total value of
1971 production, if it continues at the current rate, will be about $5,200,000.   The
annualized cost of control equipment as a percentage of total product worth (at $295
per flask) varies from 2.5 to 3.5 percent.  Partial recovery of operating cost will
be obtained from the value of additional recovered mercury.
                                                                                   19

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Large, directly fired ore smelters are not meeting the proposed standards.   Condenser
gas, which is currently being emitted at 90° to 145° F, may have to be cooled to
55° F and demisted to meet the proposed standard.   The control  equipment cost is
based on this control technique.   Because of the currently depressed market, only
the larger directly fired mercury smelters, which produce about 75 percent  of the
current U. S. mercury production, may be able to absorb the cost of required con-
trols.  The primary retort operations, which account for 10 to  15 percent of the
U. S. mercury production, are probably already meeting the proposed standards, and
little impact on this type of operation is expected.
The U. S. mercury production cannot substantially affect the international  price of
mercury, so that little of the cost increase required for control  of emissions is
expected to be passed on to the consumer.  The current low mercury prices have
caused the shutdown of both small retort operations and large, directly fired opera-
tions.  These shutdowns were accelerated by the availability of only low-mercury
ores.
The production of chlorine and alkali metal hydroxide is estimated to grow at a rate
of 6 percent for the next 5 years.  There are currently 16 companies operating 31
mercury-cell chlor-alkali plants in the United States.  The total daily production
is 7,556 tons of chlorine; the average plant produces 244 tons per day.  The mercury-
cell chlor-alkali process produces about 28 percent of the U. S. production of
chlorine and caustic.  The average plant in 1969, with no mercury emission controls,
was emitting 60 to 80 pounds of mercury per day.  Currently, plants with limited
controls are emitting from 10 to 15 pounds of mercury per day.  Original plant invest-
ment ranges from $14,000,000 to $20,000,000.  Annual value of chlorine and alkaline
metal hydroxide from an average plant is $14,100,000.
Capital costs of control devices necessary for meeting the proposed standard of
5 pounds of mercury per 24-hour period vary from 1.7 to 2.7 percent of the original
plant  investment.  The annualized cost of controls for an average chlor-alkali plant
ranges from $75,000 to $120,000.  These control costs depend largely on the sophisti-
cation and complexity of the control devices needed to meet the proposed standards,
and will vary in different chlor-alkali plants.  The annualized cost as a percentage
of the total product worth will vary from 0.5 to 0.9 percent.  The annualized cost
includes allowances for labor and supervision, maintenance, payroll overhead, operat-
ing supplies, indirect costs, and capital charges at 14 percent per year.  Amortiza-
tion of this annualized cost will at least be partially absorbed by the consumer.
 20

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Currently, most chlor-alkali plants are probably not meeting the proposed Federal
standards, but can do so by installing adequate control  devices.  The additional
cost of control devices will effect the economics of the mercury cell and will
reduce or eliminate the favored economics of mercury cells over diaphragm cells.
With current technology, the mercury-cell operation produces high-grade sodium
hydroxide at a lower price than is possible by the diaphragm-cell operation.  In
general, the cost required for producing chlorine by the mercury-cell process,
however, is slightly higher.

Until recently, the need to supply the textile and plastics industries with low-
priced, high-grade sodium hydroxide justified the fabrication of new chlor-alkali
plants employing the mercury-cell  operation.  Construction of future chlor-alkali
plants will probably favor the diaphragm cell to avoid environmental problems with
mercury emissions to water and air, and the economics of the chlor-alkali processes
will not be a deciding factor.  Modern mercury-cell plants will be controlled and
will continue to operate.  Only those plants that are already obsolete or marginal
will be abandoned.

REFERENCES
1.  Johasson, I. R.  Mercury in the Natural Environment, A Review of Recent Work.
    Geological Survey of Canada.   1971.

2.  Hazards of Mercury.  Environ.  Research 4_: 1-69, 1971.

3.  Maximum Allowable Concentration of Mercury Compounds.  Arch. Environ. Health
    19:891-905, 1969.

4.  Magoes, K.  Mercury Blood Interaction and Mercury Uptake by the Brain After
    Vapor Exposure.  Environ. Research 1_:323-337, 1967.

5.  Smith, R. G. et al.  Effects  of Exposure to Mercury  in the Manufacture of
    Chlorine.  Am. Industr. Hyg.  Assn. J. 3J_:687-700, 1970.

6.  Methylmercury in Fish.  Nord.  Hyg. Tidskr. (Stockholm), Supplement 4, 1971.
    English Translation.
                                                                                  21

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       APPENDIX.   ATMOSPHERIC DISPERSION  ESTIMATES

GENERAL PROCEDURES
Dispersion estimation  techniques were employed to assist in the  development of
national  emission standards  for mercury and beryllium.   Because  of  the broadness of
the estimation criteria and  the generally conservative  nature  of the estimation
techniques used,  the results were used as a guide rather than  as an absolute means
of determining allowable  emissions.  The estimates made were intended to apply to a
large number of sources characterized by diverse emission characteristics, climatic
conditions,  and topography.  Selection of a calculation method and  of meteorological
assumptions, therefore, involved professional judgment  based on  diffusion theory and
the limited, pertinent information that is available concerning  existing plants.

In estimating allowable emissions, the following factors were  taken into account:
                                         3                          3
      1.   The ambient  air goals are 1 pg/m  for mercury and 0.01 ug/m  for beryl-
          lium, maximum 30-day average concentration.  The 30-day averaging period
          necessitated use of a long-term dispersion estimation  method.

      2.   The allowable emissions being estimated are intended to keep ambient pollu-
          tant levels  from exceeding the given concentration goals.  They should
          apply to all rather than to average source situations. Therefore, meteor-
          ology and topography at source locations with the most restrictive disper-
          sion conditions, that is, where the least emissions  would be allowed, form
          the basis for the  calculations.

      3.   The nature of the  locations of the more significant  sources of mercury and
          beryllium (other than extraction and primary  metal production plants)
          dictated that the meteorological assumptions  used for  each pollutant be
          somewhat different.  The mercury sources that are affected by restrictive
          dispersion conditions are typically situated  in relatively rural, valley
          locales.  Correspondingly, such beryllium plants are typically situated in
          urban,  coastal  locations.

      4.   The estimation  criteria are rather broad.  Therefore,  generally conserva-
          tive assumptions were employed in order to be reasonably  confident that
          the calculated  allowable emissions will not result in  ambient air concen-
          trations in  excess of the indicated ambient air concentration goals under
          any realistically  possible circumstances.
                                         23

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CALCULATION  METHOD

The general equation given by Turner  for estimating long-term dispersion is Equa-
tion 5.15.  For this particular application it is assumed that:

     1.  A source emits at a constant rate.
     2.  Wind direction frequency is the maximum percentage occurrence of wind flow
         from one of sixteen 22.5-degree sectors during any 30-day period.
     3.  Wind flow is random from all directions within a sector during a 30-day
         period.  Correspondingly, the effluent is uniformly distributed horizon-
         tally within a sector.

With relation to the pollutants being considered, further assumptions are that:

     1.  Mercury and beryllium are emitted in aerosol form.
     2.  All effluents are emitted from a single stack.  (This assumption is rather
         conservative, for most sources have multiple emission points that permit
         greater initial dispersion.)
     3.  No loss of pollutants occurs from fallout, decay, or other natural  removal
         processes.
     4.  Mercury or beryllium background is negligible and no interaction of plumes
         between sources occurs.

The equation in the form used to estimate maximum allowable daily emissions  is:
                                        4'23 >max"°zx
where:  Q    = maximum allowable daily emission, g/day
         max
                                                         3
        xm,K, = maximum 30-day average concentration, yg/m
         fflaX
        U    = representative average wind speed, m/sec

        a    = vertical dispersion term as function of stability and distance, m

        x    = distance downwind, m

        F    = maximum frequency of wind direction from a 22.5-degree sector, %

        H    = effective stack height, m
24

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Effective stack height was assumed  to  be  10 meters (about 33 feet).  This assumption
was made since mercury and beryllium are  usually emitted from roof vents or short
stacks with little or no  plume rise.   The consequent release of pollutants at a
relatively low height is  compounded by aerodynamic downwash effects that often
influence these sources.   The result is to minimize the average effective height of
emission.

METEOROLOGICAL  ASSUMPTIONS
There are  three principal meteorological  parameters  for which  representative values
were  selected.  These  parameters are:

      1.   Average  wind  speed,  U.

      2.  Average  atmospheric  stability, which determines values of the vertical
         dispersion  term, o  .

      3.  Maximum  frequency of wind direction from any one sector, F.

Restrictive meteorological conditions selected as representative of the site types
indicated  for mercury  and beryllium for  a 30-day period are as follows:

                               Mercury                    Beryllium
         Average           Neutral  (class D)      Slightly unstable (class C)
           atmospheric
           stability
         Average           2 m/sec (4.5 mi/hr)         3 m/sec (6.7 mi/hr)
           wind speed
         Maximum wind          40 percent                 40 percent
           direction
           frequency

DISCUSSION  OF METEOROLOGICAL  ASSUMPTIONS
Representative meteorological  conditions  were  selected  from a range of alternatives.
The purpose of this discussion is to indicate  the effect on estimated allowable
emissions of the various  alternatives.
Average  Atmospheric Stability
In selecting an average stability condition  for  site  types with typically restrictive
meteorological  conditions, the choice was  made between  the Pasquill class C, D, and
E stabilities for mercury and class  C and  D  stabilities for beryllium.  For a rural-
valley mercury source site, D (neutral)  is judged  to  be the most appropriate stabil-
ity.  Stability C (slightly unstable) would  apply  if  the  valley site experienced sig-
nificant turbulence induced by buildings or  topographic features.  Class E  (slightly
                                                                                  25

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stable) would  be  the  least  likely choice  and would  apply  in  a well-protected  valley
under deep shadows during a  large portion of the daylight hours.   Most sources of
beryllium, such as metal working or machine shops,  would  typically be located in
metropolitan areas where the heat island  effect and building-induced turbulence
would be likely to result, on the average, in a class C stability  condition.   In
smaller or suburban communities, class D  would probably be a better choice.

The calculated maximum  allowable emissions for the  stability classes discussed are
shown in Figure 1 for mercury and in  Figure 2 for beryllium.  These figures  show
maximum allowable emissions  calculated not to exceed ambient concentration goals at
corresponding  distances from the source.
                                                1500
                                     DISTANCE FROM SOURCE, M
           Figure 1.  Calculated maximum allowable mercury emissions under applicable
           Pasquill stability classes (C, D, and E) and wind speed of 2 m/sec.
Average Wind Speed
For  estimating  allowable mercury  emissions,  the choice  of 2 mps  (4.5  mph)  is  con-
servative.   However,  an actual  valley  site  in  which  a chlor-alkali  plant  is
situated had an average wind  speed  of  4.6 mph  during a  recent annual  period of
measurement. The wind speed  of 2 mps  was chosen over a less  restrictive  wind
speed  of 3 mps  (6.7 mph).   The  effect  of a  3-mps wind speed on calculated  allowable
emissions is shown  in Figure  3  for  the three  stability  alternatives.   For estimating
allowable beryllium emissions,  the  choice of  3 mps was  considered  typical  of  some
urban-coastal source  sites  and  no other alternative  was considered.

Maximum  Wind  Direction Frequency
The  maximum  wind  direction  frequency of 40  percent  that was used to estimate  mercury
emissions is slightly conservative.  Inspection of  limited  data  available for a
26

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                LkJ

                lac
                                                              /"C" STABILITY

                                         1000         1500
                                         DISTANCE FRO* SOURCE, tat
            Figure 2.  Calculated maximum allowable beryllium emissions under applicable
            Pasquill stability classes (C and D) and wind speed of 3 m/sec.
                                        UN          ISM

                                        DISTANCE FRO! SOURCE. M
            Figure 3.  Calculated maximum allowable mercury emissions under applicable
            Pasquill stability classes (C, D, and E) and wind speed of 3 m/sec.
period  of 1 year  for four  typical valley locations  indicated maximum values in the
range of 30 to 35 percent.   It is likely that inspection of data for a  longer period
would have revealed values  approaching  or possibly  exceeding 40 percent.   It suf-
fices to point out that, on the basis of available  information, the 40  percent may
                                                                                          27

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be slightly conservative.   With respect to  beryllium  sources,  inspection of avail-
able wind direction frequency data for a 5-year period  did reveal values of 40 per-
cent or greater at some coastal sites, apparently  as  the  result  of  flow patterns
associated with typical sea-breeze effects.

REFERENCE
1.  Turner, D.  Bruce.   Workbook of Atmospheric  Dispersion Estimates.  U.S. DHEW,
    PHS, EHA, National  Air Pollution Control  Administration.   NAPCA Publication
    No. 999-AP-26.  Cincinnati, Ohio (Revised 1970).
 28

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