Date: May 2, 1996
From: Joseph A. Dear, Assistant Secretary
Occupational Safety and Health Administration
Subject: Special Emphasis Program (SEP) for Silicosis
provides inspection targeting guidance for implementing an OSHA-wide Special Emphasis
Program (SEP) to reduce and eliminate the workplace incidence of silicosis from exposure
to crystalline silica. The policy set forth in this memorandum is effective immediately.
This SEP covers most SIC codes where an exposure to crystalline silica may exist.
Inspections initiated under this SEP shall be scheduled and conducted in accordance with
the provisions in the Field Information Reference Manual (FIRM) and the Revised Field
Operations Manual (FOM). 1,2 Regional Administrators and Area Directors shall
ensure that the procedures established in this memorandum are adhered to in the scheduling
of programmed inspections. Regional Administrators shall also ensure that the State
Consultation Program Managers and the State Plan State Designees in their Regions are
appraised and aware of the contents of this SEP and its required Area Office outreach
initiatives. In all Federal enforcement states, and state plan states which adopt this
program policy, Regional Administrators are to encourage the Consultation Programs' full
cooperation and assistance in this Agency-wide effort.
Background information on
crystalline silica and silicosis can be found in Appendix A to this document.
General Industry Targeting:
Inspections conducted under this special emphasis program shall be scheduled and
conducted under the priorities listed below. Wherever possible (data permits) inspections
shall be focused to particular establishments where overexposures to crystalline silica
are most likely or there are known cases of silicosis. In looking at records mentioned
below be advised that a diagnosis of silicosis may include such terminology as
pneumoconiosis, fibrosis, respiratory disease, non-malignant respiratory disease, or even
congenital heart failure.
The following are suggestions for obtaining information to target inspections at
particular establishments or SIC Codes. Area Offices shall determine if any of these
suggestions are applicable to their areas and shall attempt to obtain and use such data.
The data sources have been prioritized based upon what is considered most beneficial.
In some cases the use of the data may involve lengthy discussions and
preparation of Memorandums of Understanding with the respective agency.
Where CSHOs utilize visual observations for targeting of construction related
inspections the following shall be followed:
- For Area and Regional Offices that have workers compensation data, it shall be evaluated
for trigger entries such as silicosis, pulmonary fibrosis, fibrosis, nonmalignant
respiratory disease, pulmonary edema, congenital heart failure, and/or scarring of the
lungs. Data obtained from this source shall be examined and compared with likely SIC Codes
for a determination of whether there is a potential for exposure to silica.
- Cross referencing of Agency-collected OSHA 200 data with SIC data may produce inspection
sites for the SEP. The Office of Statistics can be contacted to determine the status of
the data and the potential for matching certain SIC codes with specific employers. Bear in
mind that, this is in the early development phase and will not likely be a good source
during the early implementation of this SEP.
- SENSOR Data (Sentinel Event Notification Systems for Occupational Risks) is a NIOSH
program of cooperative agreements with state health departments to develop models for
state-based occupational disease surveillance programs. There are 11 current cooperative
agreements for FY 1995. The program is collecting silicosis data in Illinois, Michigan,
North Carolina, New Jersey, Ohio, Texas, and Wisconsin. The Office of Health Compliance
can provide the names and phone number/address of state contact persons.
- State Surveillance Systems. Many states have such programs in place. As these become
more popular they could represent our best source of data.
- Contacts with local trade unions, especially those involved with painting may provide
information useful to developing a targeting system.
- Hospital Discharge Data. This source may represent a valuable source of data as
hospitals sometimes obtain patient work histories. Rosenman (1988), has considerable work
on this and can be referred to for more specific information.3
- Registry of Occupational Safety and Health (ROSH) data. The Bureau of Labor Statistics
(BLS) has been collecting data and has set up special coding for crystalline silica. The
BLS can be contacted to obtain the this data which cross references with SIC Codes.
- Review of local or area morbidity statistics.
- Other possible sources include contacting pulmonary specialists and discussing silica
and silicosis with them. Occupational health clinics, can be contacted as well as
occupational physicians. One can also contact the Association of Occupational and
Environmental Clinics (AOEC) at (202) 347-4976 for clinics in jurisdictional areas.
- The reference list for this memorandum also contains a variety of articles that show
different sources of data that can be used in establishing inspection lists.
- Chemical Use Inventories - This is under development by the EPA. Potentially, the
database will contain chemical, site specific information which can be used for targeting.
Some states (New Jersey) may already have some form of this in place.
Whenever a CSHO observes or receives information, the CSHO shall:
Documentation of the events leading up to the observation shall be maintained by the
Area Office in case of a denial of entry.
- Document the status and condition of the work operation as far as it is known, noting
any serious hazards.
- Note the name and address and location of the worksite or facility and, in construction,
the name of the contractor(s) performing the work.
- Provide the Area Office Supervisor or Area Director with the information. Based upon the
information provided, all potential crystalline silica dust exposures brought to the
attention of the Area Office shall be inspected as follows:
If the worksite has been
inspected within the last 30 days, the results of the inspection shall be considered along
with the current worksite observations in determining whether or not an inspection is to
If the crystalline silica dust generating work was not in progress during the previous
visit to the site but is currently in progress the inspection shall be authorized and
If the crystalline silica dust generating work was in progress and evaluated during the
previous inspection, the inspection will be opened only if apparent serious violations are
present or can reasonably be expected at the site.
If the worksite has not been inspected within the previous 30 days, an inspection shall
be conducted unless it is apparent that workers are not exposed to crystalline silica
The following is a list of elements which may be included in an effective program
[Note: In a facility where exposures are below the permissible exposure limit, CSHOs, for
education and information purposes, should make the employer aware of elements that should
be included in an effective crystalline silica control program in order to provide
employees at the establishment protection from possible crystalline silica over
For Area Offices that cannot develop a site specific inspection list from the examples
in No. 1, a list of industries under their jurisdiction likely to be involved in
crystalline silica-related activities and exposures shall be developed. The tables
presented in Appendix B include SIC codes prepared from OSHA's IMIS data. The two tables
represent lists of SIC codes where sampling was conducted and where over exposures to
crystalline silica were documented. These lists can be used as a starting point for Area
Offices to develop a list of SIC Codes and facilities under their jurisdiction where there
is the most likely potential for worker silica exposure.
Inspection sites using any of the previously discussed methods shall be randomly
selected for inspection using a random numbers table. This selection process sets forth
administratively neutral criteria to identify establishments for inspection. Area Offices
and Regions may first want to cull the list to remove sites recently evaluated or not
likely to have hazards associated with crystalline silica. Some lists generated using 4
digit SIC codes will produce sites clearly not likely to have the hazard present.
- Focused Inspections:
As with focused inspections in construction6,
those sites targeted for inspection that have implemented an effective and ongoing
silicosis prevention program can be exited after the program review. The silicosis
prevention program may appear as or be part of the establishment's overall safety and
health program. If the facility appears to qualify for a focused inspection based upon
management interviews and company documentation the CSHO will verify the program through a
brief walkthrough and employee interviews. The CSHO, prior to leaving the facility, shall
document that his or her initial review of the site's safety and health program or the
site's crystalline silica control program found that the program elements were appropriate
and fully effective in providing protection to the affected workers.
*Required by specific OSHA standards if an overexposure to crystalline silica exists.
ongoing personal air monitoring program*
ongoing medical surveillance program
training and information to workers on crystalline silica*
availability of air and medical surveillance data to workers*
an effective respiratory protection program*
hygiene facilities and clothing change areas
personal exposures below the PEL or the facility has an abatement program that also
provides for interim worker protection
in construction a safety and health program*
This SEP is a nationwide initiative with participation by all Regions and Area Offices.
In the case of locally developed Cooperative Compliance Programs such as the Maine 200,
the Wisconsin 200, the New Hampshire 50, or other programs developed by redesigned Area
Offices, the offices shall work this SEP into their programs.
Regions are to begin conducting inspections under this SEP immediately following 60 days
of outreach activities. (See Full Service Program Support beginning on page 11.)
In construction and maritime, where resources permit, a joint safety and health
inspection should be conducted. Referrals to safety compliance officers where appropriate
shall be submitted.
If CSHOs find a product that contains crystalline silica and downstream exposure is
reasonably anticipated (sawing or cutting of brick, tiles, and concrete blocks), they
should investigate the adequacy of the material safety data sheets (MSDS) and product
labeling. For example, concrete blocks have been found with labels stating "caution,
irritant dust", and the MSDS did not address accurately the chronic health hazard.
And Laboratory Submission Of Samples
Inspections under this SEP shall address areas of potential crystalline silica
dust-related overexposures where there is an increased risk of silicosis. Inspections will
include a review of written documentation (i.e. recordkeeping, air monitoring, medical
examinations or evaluations, respirator protection, engineering and/or work practice
controls, hazard communication, MSD sheets, and training). The CSHO may expand the
inspection scope beyond the crystalline silica-related activities if hazards or violations
are observed (FIRM CH. II-1).1
If the CSHO, based upon professional judgement or sufficient employer monitoring data,
determines that employees are not overexposed to crystalline silica the CSHO can close and
move to another job site. Prior to exiting, the CSHO should discuss the employer's silica
program and provide suggestions and information where appropriate.
CSHOs shall question employers to determine whether the employer has conducted personal
or area sampling for dust containing crystalline silica. Where such data has been
collected copies of the data shall be obtained. CSHOs will also interview the employer to
determine whether the employer has conducted any medical surveillance of exposed
employees. If such surveillance records exist, copies of the records shall be obtained
where necessary to support a violation (medical access orders shall be used where
Medical records should be reviewed in consultation with the Office of Occupational
Medicine. Appendix C contains recommendations for medical evaluations related to
crystalline silica exposure as well as suggestions for a medical monitoring program.
Regardless of the level of exposure to crystalline silica, CSHOs should make Appendix C
available to the employer.
CSHOs shall conduct personal employee monitoring and collect appropriate bulk samples
where appropriate to document exposures unless the inspection focused or the employer has
documented that no overexposure exists.
While evaluating worker exposures to dust containing crystalline silica during abrasive
blasting, CSHOs shall also be aware of and evaluate potential exposures to noise and
metals. Metal exposures often associated with abrasive blasting include but are not
limited to: lead, arsenic, manganese, chromium, cadmium, copper, and magnesium.
Worker clothing contaminated with crystalline silica dust can be carried home and
potentially expose family members. Worksites where this potential is observed by the CSHO
should be evaluated (including automobiles) and the employer and employee representatives
made aware of the hazard of such activity.
Citations and classification of violations for overexposures to crystalline silica dust,
for respiratory protection, and for work practice and/or engineering controls shall be
issued in accordance with the procedures and requirements of the FIRM.1
For examples of standards that contribute in controlling potential exposures to
crystalline silica please refer to Appendix D.
The exposure monitoring shall consist of personal
respirable dust samples collected from the worker's breathing zone. Exposure monitoring
shall be conducted in accordance with The OSHA Technical Manual TED 1.15 and with OSHA
Instruction CPL. 2-2.43A, the Chemical Information file (noted as Chemical Sampling
Information on the OSHA CD).6
As a reminder, all collected samples shall be pre- and post-weighed by the CSHO in
accordance with standard agency procedures. The SLTC is now providing filter weighing
services to the field. To use the pre-weighed filters supplied by the SLTC with the 10-mm
nylon cyclone sampling device assembly, the field must obtain a plastic coupler [contact
the SLTC or the Cincinnati Technical Center (CTC) for further information]. The
pre-weighed filters can be ordered either from the SLTC or the CTC. If the CSHOs do not
use the SLTC pre-weighed filters, they should pre- and post-weigh all collected samples
according to the standard agency procedures. Samples shall be desiccated before conducting
pre- and post-weighings. Filter cassettes with the 10 mm nylon sampling device will be
placed in the workers breathing zone. Full shift samples shall be collected where
possible. Sample air volumes of 408 to 816 liters are recommended. A sampling flow rate of
1.7 liters per minute (ñ 0.2 liters per minute) should be used with the 10 mm nylon
cyclone sampling device. CSHOs should refer to the OSHA Technical manual TED 1.15 for pump
calibration information with cyclones.6 Care needs to be taken to assure that
the cyclones are not inadvertently inverted. CSHOs are to check pumps on at least an
hourly basis, if possible, and note the flow rates, and document what the worker was doing
at the time of the check. If filter overloading is suspected or workers change to another
job or procedure, the CSHO shall replace the sampling filter with a new filter and
document the time of the changes. Blank filters shall be obtained in accordance with
standard procedures. For jobs that are of short duration such as in construction, CSHOs
should request that the samples be expedited.8
The SLTC will honor a request from a CSHO to have sample analyses "rushed"
because of "a short term operation", "severe health problems",
"union or media concern", or even if a limited number of samples need to be
rushed for a "fast track screening".
Occasionally CSHOs will encounter a work situation where there is mixed exposure to
quartz, cristobalite, and/or tridymite. In these situations, CSHOs, in addition to looking
at the individual exposures, shall also apply the mixture formula found in Appendix E to
Sampling for Bulks:
For crystalline silica analysis, if available, bulk samples should be submitted to
the laboratory under separate cover. Bulk samples can be collected through a variety of
means. A bulk, high volume, respirable sample may be the most ideal of the bulk samples.
However, this type of bulk sample may not be as practical to collect as a settled dust
sample or a sample of the raw materials. The following bulk sample methods are listed in
the ideal order of preference: 8
- High volume respirable filter sample (preferably > 1.0 grams). Contact the SLTC for
information on this.
- High volume filter sample - nonrespirable (preferably > 1.0 grams).
- Representative of settled dust [i.e. rafter sample (preferably > 1.0 grams)].
- Sample of the bulk material in the workplace - preferably 10-20 grams.
Interferences can affect the laboratory analyses. However in the vast majority of
cases, interferants do not prevent analyses. The SLTC uses X-ray diffraction to analyze
for quartz and uses the three most sensitive peaks to minimize interferences and provide
conclusive identification. To assist the laboratory, list any potential interferences on
the OSHA 91A Form submitted with the samples. In addition, the CSHO should include a copy
of the material safety data sheet for the silica containing material if available.
Potential interferences on one or more peaks for crystalline silica analyses include but
are not limited to the following:8
Procedures For Construction And Maritime
- aluminum phosphate
- biotite (mica)
- feldspar (some)
- high albite
- iron carbide
- lead chromate
- lead sulfate
- muscovite (mica)
- potassium hydroxide
The crystalline silica exposure limit for the
construction and maritime trades in 29 CFR Parts 1926 and 1915 are expressed in terms of
millions of particles (of dust) per cubic foot (MPPCF), which is measured using an
impinger sampling method. The impinger method of counting dust particles is obsolete, and
comparative sampling has established that the formula of 250/[(% quartz) + 5] which sets
the mppcf exposure limit described in the maritime and construction standards is
equivalent to the general industry PEL of:
(10mg/m3)/((% Quartz) + 2)
Therefore the same gravimetric sampling method and the general industry PEL formula should
be used in all industries. This evidence is discussed more fully in Appendix F.
Recording In The IMIS
Current instructions for completing enforcement forms OSHA-1, OSHA-7, OSHA-36, and OSHA-90 and
Consultation Request Form-20 and Visit Form-30 shall be applied when recording inspections
conducted under this SEP as follows:
- The OSHA-1 Form for any programmed inspection covered under this special emphasis
program for crystalline silica in all industries shall be marked "PLANNED" (Item
24h) and "SPECIAL EMPHASIS PROGRAM" (Item 25d). Record SILICA in the space in
- The OSHA-1 Form for any unprogrammed inspection shall be marked as unprogrammed (Item
24a. through g. as appropriate). In addition, it shall be marked "SPECIAL EMPHASIS
PROGRAM" (Item 25d). Record SILICA in the space in Item 25d.
- For focused inspections covered under this SEP, Item 42 (Optional Information) of the
OSHA 1 Form shall be completed according to the guidelines outlined in the memorandum of
March 10, 1995, detailing the proper coding for focused inspections (see Appendix G).
- Whenever an OSHA-7 is completed by a Federal office and the applicable complaint alleges
the presence of crystalline silica or related silicates, complete the OSHA-7 in the normal
manner, but include the code for silica in "Optional Information" Item No. 46.
The following format should be used:
- Whenever an OSHA-36 is completed by a Federal office and the inspecting compliance
officer(s) is/are able to identify at the site of the fatality/catastrophe the presence of
crystalline silica or related silicates, complete the OSHA-36 in the normal manner, but
include the code for silica in "Optional Information" Item No. 35. The following
format should be used:
- Complete the OSHA-90 in the normal manner and enter the code "SILICA" in
"Optional Information" Item No. 26, when an OSHA-90 is completed by a Federal
office and the applicable referral case has crystalline silica as one of the subjects of
the file. The following format should be used:
Whenever a visit is
made in response to this SEP, Consultation Request, and/or Visit forms are to be completed
Full Service Program Support
- Complete the Request Form-20 in the normal manner and enter the code "SILICA"
in "Optional Information", Item No. 26, when a visit has been made in response
to the SEP. The following Information should be used:
- Complete the Visit Form-30 in the normal manner and enter the code "SILICA" in
"Optional Information", Item No. 34, when a visit has been made in response to
the SEP. The following Information should be used:
Each Area Office/Region is encouraged
to develop outreach programs that will support the enforcement effort. Such programs could
include letters to employers, professional associations, the Associated General
Contractors (AGC), local unions, Associated Builders and Contractors, local safety
councils, apprenticeship programs, local hospitals and occupational health clinics, and/or
other industry employer organizations that work with or potentially generate crystalline
silica dust. Speeches, training sessions, and/or news releases through the local news
papers, safety councils and/or industrial hygiene organizations can provide another avenue
for dissemination of information. A generalized crystalline silica/SEP news release will
be prepared by the National Office and made available to each Region.
All OSHA Consultation Program offices will be provided with a copy of the SEP
memorandum. In those states which are participating in the program, Regional
Administrators shall ensure the coordination between Area Directors and the State
Consultation Program manager to encourage their assistance in outreach efforts in support
of this program. Existing local silica/silicosis expertise within state Consultation
program office may provide valuable assistance to the Area Office staff in their various
outreach efforts. Consultation projects may also have already developed or have available
to them written, audio visual, or materials in other formats on working safely with silica
and/or worker safety and health training materials that may be helpful to the Area Office.
State Consultation projects are provided specific instruction in this document for coding
consultative visits made for requests for assistance in response to this SEP. Requests for
Consultative visits from employers as a result of OSHA's Silicosis SEP are to be given
priority over other visit requests, as appropriate.
The Office of Health Compliance Assistance in conjunction with the OSHA Training
Institute will develop crystalline silica related information and training materials. This
information will be made available to the Regional Offices for distribution to their
respective field offices.
Area Offices are encouraged to develop a list of industries and contractors involved in
crystalline silica related work and potential exposures. Once the list has been generated,
each entry can be contacted (if resources permit) in writing and provided with a copy of
this memorandum and general information available about crystalline silica.
To assist the Agency in outreach, Area and Regional Offices through the Silica SEP
Coordinator should be compiling a list of frequently asked questions (FAQs) that are
received a long with their full responses. These FAQs would then be periodically forwarded
to the Office of Health Compliance Assistance. The FAQs could include questions like the
Measuring Agency Impact
- How does the OSHA PEL of 10/(% Quartz + 2) compare to the ACGIH TLV of 0.1 mg/m3
or the NIOSH REL of 0.05 mg/m3?
- How do I perform a mixture calculation if the sample contains both quartz and
- How are we able to use a PVC filter with a 5 m pore size to capture down to submicron
- Can I sample using low ash 0.4 m pore size AA (MCEF) filters instead of low ash PVC
- Why do we use nylon cyclones rather than metal cyclones?
- How do I perform a leak test of the cyclone?
Region shall designate an individual as the silica SEP Coordinator. The identified
individual shall coordinate crystalline silica inspection activities and work with the
Office of Health Compliance Assistance to collect and evaluate the effect and success of
this program. Measuring Agency impact can be broken down into an interim component and a
final component. In the interim, the Office of Health Compliance Assistance will collect
and evaluate IMIS data through coding on the OSHA-1 for this SEP. In the long-term, the
Regional Silica Coordinator, in conjunction with the Office of Health Compliance
Assistance, will collect information on the development of new and feasible engineering
and work practice control techniques, and on controls through substitution of silica with
other materials (for example some non-ferrous foundries have found that with equipment
modification they can use olivine sand). They will also collect information on medical
programs implemented, airborne personal monitoring programs in place, examples of silica
control plans or exemplary workplace safety and health programs with effective silica
control program elements, numbers of inspections that were focused, and the like.
Area Offices or the Regions, under this SEP, will need to maintain a file containing
abatement information from their inspections and a summary of any medical programs related
to silica exposure in effect. The data shall include both recommended and implemented
abatement information for the specific type of operation that was evaluated. Such
information shall also include a reference to the inspection number.
This program will run through Fiscal Year 1997. At the end of Fiscal Year 1997 the
program will be regionally evaluated by each Regional Silica Coordinator. A written
evaluation will be submitted to the Director of the Office of Health Compliance Assistance
discussing the program operation in their respective Regions, the effectiveness, problems
encountered, any recommendations for changes or additions to the program, and finally a
recommendation on whether or not to continue the program. The Office of Health Compliance
Assistance will evaluate these Regional Report and will make a recommendation to the
Director of Compliance Programs on whether or not to continue the program. A final report
on the program will be prepared by the Office of Health Compliance Assistance evaluating
the effectiveness of this SEP.
Federal Program Change
This is a federal program change that impacts state programs. The Regional Administrator (RA)
shall ensure that this change is promptly forwarded to each state designee using a format
consistent with the Plan Change Two-way Memorandum in Appendix A, OSHA Instruction STP
2.22A, State Plan Policies and Procedures Manual (SPM). The RA shall explain the content
of this change to the state designees. States are encouraged, but not required, to adopt
an identical or alternative policy. States shall be asked to provide preliminary
notification to the RA within 30 days from the date of this instruction of their intent to
adopt or not to adopt the SEP established by this memorandum. The state shall formally
respond to this change with an indication of its final determination within 70 days in
accordance with paragraph I.1.a.(2).(a). and (b), Chapter III of Part I of the SPM. If the
state adopts identical compliance procedures, the Plan Change Two-way Memorandum plus a
copy of the state's cover memo or directive transmitting these procedures to its field
staff will suffice as the plan supplement. If the state adopts different compliance
procedures, a copy of the procedures shall be provided to the RA within six (6) months
from the date of this memorandum.
In those state plan states where the PEL in construction or maritime is the same as
OSHA's (units in MPPCF) the states are urged to follow the procedures spelled out in
Appendix F. States are also strongly encouraged to use all the sampling and analytical
methods in this memorandum when they evaluate crystalline silica, regardless of whether
they adopt the SEP. These procedures are the same as those in the OSHA Technical Manual.
As with any complex sampling procedures, states not having the necessary laboratory
equipment for the analyses may contact the Salt Lake City Laboratory for assistance.
The RA shall review policy, procedures, and instructions issued by the state and
monitor their implementation as provided in a performance agreement or through routine
monitoring focusing on impact and results.
Distribution: National, Regional, and Area Offices
All Compliance Officers
State Consultation Project Managers
NIOSH Regional Program Directors
Background: Crystalline Silica and Silicosis
Crystalline silica is a ubiquitous substance which is the basic component of sand,
quartz and granite rock.9 Airborne crystalline silica occurs commonly in both
the work and non-work environments. Occupational exposure to crystalline silica dust has
long been known to produce silicosis, a pneumoconiosis or dust disease of the lung.
Activities such as sandblasting, rock drilling, roof bolting, foundry work, stonecutting,
drilling, quarrying, brick/block/concrete cutting, gunite operations, lead-based paint
encapsulant applications, and tunneling through the earth's crust can create an airborne
silica exposure hazard. In addition some recently noted exposures to crystalline silica
include the following:
Geologically, quartz is the second most common mineral in the earth's crust. Quartz is
readily found in both sedimentary and igneous rocks. Quartz content can vary greatly among
different rock types, for example: granite can contain anywhere from 10 to 40 percent
quartz; shales have been found to average approximately 22 percent quartz; and sandstones
can average almost 70 percent quartz. Silica is a general term for the compound silicon
dioxide (SiO2). Silica can be crystalline or amorphous. Different crystalline
silica structures exist as polymorphs of silica and include quartz and less common forms
such as cristobalite and tridymite. The latter two are less stable than quartz which
accounts for the dominance of the quartz form. Quartz can exist as two sub-polymorphs,
à-quartz or low quartz, and -quartz or high quartz. Of these two forms, à-quartz is more
common as the -quartz is apparently only stable at temperatures above approximately 570
degrees centigrade. Upon cooling, -quartz quickly converts to à-quartz. In the
literature, crystalline silica is commonly referred to as silica sand, free-silica,
quartz, cristobalite, and tripoli. When diatomaceous earth is subjected to pressure or is
processed (calcined) at temperatures above 1000 degrees C some of the amorphous silica is
converted to crystalline silica in the form of cristobalite.11 Recent articles
have documented the creation of cristobalite in "after-service" refractive
ceramic fiber insulation.12-14 Amorphous silica has been found to exist in
nature as opal, flint, siliceous glass, diatomaceous earth and vitreous silica.15
- Calcined diatomaceous earth can contain anywhere from <1% to 75% cristobalite. In
addition to use as a filtering media, calcined diatomaceous earth is often used in
industries such as food and beverage preparation where only food grade products and
equipment can come in contact with foods or beverages being made.
- Asphalt paving manufacturing may also be a source of crystalline silica exposure, due to
the mechanical formation of crystalline silica dust when sand and aggregate passes through
rotary dryers. The fine dust can have significant amounts of crystalline silica, depending
upon the source of the aggregate. For example, rotary drying of gravel from the Willamette
river in Oregon was found to generate dust containing approximately 7 to 12% quartz. The
waste dust was transferred periodically by front loader, resulting in clouds of visible
dust drifting to the operator.
- The repair or replacement of linings of rotary kilns found in pulp and paper mills and
in other manufacturing locations as well as the linings in cupola furnaces are potential
sources of crystalline silica exposure. This work may not be commonly seen due to the
infrequency and less visible nature of the work location. Turnarounds and yearly shutdowns
are the time when this work commonly occurs.
- In food processing operations where crops such as potatoes and beans are readied for
market, silica overexposures have been documented in the sorting, grading and washing
Silicosis is one of the world's oldest known occupational diseases with reports dating
back to ancient Greece. Since the 1800's, the silicotic health problems associated with
crystalline silica dust exposure have been referred to under a variety of common names
including: consumption, ganister disease, grinders' asthma, grinders' dust consumption,
grinders' rot, grit consumption, masons' disease, miner's asthma, miner's phthisis,
potters' rot, sewer disease, stonemason's disease, chalicosis, and shistosis. Silicosis
was considered the most serious occupational hazard during the 1930s, and was the focus of
major federal, state, and professional attention during this time.10 The
hazard is still present 60+ years later.
Crystalline silica is commonly found and used in the following industries:
Perhaps the most familiar use of quartz sand is as an abrasive blasting agent to
remove surface coatings prior to repainting or treating. A recent alert published by the
National Institute for Occupational Safety and Health (NIOSH) estimates that there are
more than one million American workers that are at risk of developing silicosis. Of these
workers, NIOSH further estimates that more than 100,000 are employed as sandblasters.16
- electronics industry
- foundry industries
- ceramics, clay and pottery, stone, and glass industries
- railroad industry (setting and laying track)
- slate and flint quarrying and flint crushing
- use and manufacture of abrasives
- manufacture of soaps and detergents
- mining industries.
In the United States, from 1968 through 1990 the total number of deaths where silicosis
was reported anywhere on the death certificate was 13,744. Of these, approximately 6,322
listed silicosis as the underlying cause of the death.17 In this study, deaths
in the United States due to silicosis was primarily concentrated in 12 states (California,
Colorado, Florida, Illinois, Michigan, New Jersey, New York, Ohio, Pennsylvania, Virginia,
West Virginia, and Wisconsin.) The silica-related deaths in these 12 states accounted for
68% of the total silica related deaths in the United States. By industry, construction
accounted for 10% of the total silicosis-related deaths.17
Based upon the wide spread occurrence and use of crystalline silica across the major
industrial groups (maritime, agriculture, construction, and general industry), and in
consideration of the number of silicosis related deaths, the NIOSH estimates for the
number of exposed workers, and the health effects of crystalline silica dust exposure
(e.g., pulmonary fibrosis, lung and stomach cancer), the Agency is implementing a
nationwide special emphasis program to assure worker protection from over exposure to
crystalline silica dust.
Health Effects of Silica Exposure
Inhalation of crystalline silica-containing dusts has been associated with
silicosis, chronic obstructive pulmonary disease, bronchitis, collagen vascular diseases,
chronic granulomatous infections such as tuberculosis, and lung cancer. In general,
aerosols of particulates can be deposited in the lungs. This can produce rapid or slow
local tissue damage, eventual disease or physical plugging. Dust containing crystalline
silica can cause formation of fibrosis (scar tissue) in the lungs.9
The inhalation of free crystalline silicon dioxide (SiO2) can produce a
fibrotic lung disease known as silicosis. Particle size, dust concentration and duration
of dust exposure are important factors in determining the attack rate, latency period,
incidence, rate of progression and outcome of disease. A higher attack rate and severity
of silicosis is seen with heating crystalline silica-containing materials to greater than
800° C to transform SiO2 into tridymite and cristobalite (both of which occur
naturally and are also found in synthetic silica preparations). High cristobalite
concentration also result from direct conversion of diatomaceous earth following heat
and/or pressure and can be found in the superficial layers of refractory brick which have
been repeatedly subjected to contact with molten metal. 9
NIOSH has classified three types of silicosis, these include acute, accelerated,
Acute Health Effects:
Intense crystalline silica exposure has resulted in outbreaks of acute silicosis
referred to medically as silico-proteinosis or alveolar lipoproteinosis-like silicosis.
Initially, crystalline silica particles produce an alveolitis (inflammation in the gas
exchange area of the lung) which is characterized by sustained increases in the total
number of alveolar cells, including macrophages, lymphocytes and neutrophils. The
alveolitis has been found to progress to the characteristic nodular fibrosis of simple
A rapid increase in the rate of synthesis and deposition of lung collagen has also been
seen with the inhalation of crystalline silica particles. The collagen formed is unique to
silica-induced lung disease and biochemically different from normal lung collagen.18
Accelerated Health Effects:
Accelerated silicosis may occur with more intense exposure over 5 to 15 years.
Fibrotic nodules are generally smaller and the massive fibrosis often occurs in the
mid-zones in the lungs.
Acute and accelerated silicosis have been associated with abrasive blasters.
Chronic Health Effects:
Chronic silicosis usually takes 20 to 45 years to develop as a result of prolonged
exposure to free crystalline silica. Nodular lesions tend to form in the upper lobes. In
the simple stage of silicosis, symptoms and impairment of pulmonary function are uncommon.
If progressive massive fibrosis (PMF) forms from the coalescence of fibrotic nodules the
disease usually progresses, even following removal from exposure. Symptoms of silicosis
may not develop for many years. Shortness of breath with exertion is the most common
symptom of established silicosis. Cough and expectoration may develop with disease
progression, especially in cigarette smokers. Wheezing typically only occurs when
conditions such as chronic obstructive bronchitis or asthma are also present. Significant
abnormality on a chest x-ray may not be seen until 15 to 20 years of exposure have
When advanced disease and progressive massive fibrosis are present there is distortion
of the normal architecture of the lung. Airway obstruction may occur from contraction of
the upper lobes of the lung. Emphysematous changes may develop in the lower lobes of the
The issue of crystalline silica exposure and cancer is a complicated one with
disagreement in the literature.20 In worst case, exposure to respirable
crystalline silica dust has been associated with lung cancer.20-26 There also
has been the suggestion of stomach cancer associated with ingestion of crystalline silica.7 The International Agency for Research on Cancer (IARC) in examining the
carcinogenesis of crystalline silica has published monographs regarding crystalline silica
and some silicates. IARC determined that there is sufficient evidence for carcinogenicity
in experimental animals with limited evidence for carcinogenicity in humans and has
classified silica as a 2B carcinogen.21 IARC is in the process of revisiting
the crystalline silica carcinogen issue based upon recent epidemiological studies.
Studies have demonstrated a statistically significant, dose-related increase in lung
cancer in several occupationally exposed groups. Winter (1990) observed that the lung
cancer risk for pottery workers increased with estimated cumulative exposure to low levels
of silica found in potteries. Another study also found that the risk of lung cancer among
pottery workers was related to exposure to silica, although the dose-response gradient was
not significant (McLaughlin, et al., 1992). An adjustment for possibly confounding
exposure to polycyclic aromatic hydrocarbons slightly raised the odds ratios for exposure
to silica. This study also analyzed lung cancer risk in tin miners in China and found a
significant trend of increasing risk of lung cancer with increasing cumulative respirable
silica exposure. A significant dose-response relationship between death from lung cancer
and silica dust particle-years has also been demonstrated for South African gold miners
(Hnizdo and Sluis-Cremer, 1991). In this study a synergistic effect on lung cancer risk
was found for silica exposure and smoking. Lung cancer risk among workers in the
diatomaceous earth industry has been studied by Checkoway, et al. (1993). Results showed
increasing risk gradients for lung cancer with cumulative exposure to crystalline silica.
The authors felt that this finding indicated a causal relation. Several studies have
demonstrated a relationship between the degree of silicosis disability and risk for lung
cancer (Goldsmith, 1994). Since severity of silicosis reflects silica exposure, this may
also indicate a dose-response relationship for silica exposure and lung cancer (Checkoway,
For additional information please refer to references No. 22-26.
Due to the potential association between exposure to dust containing crystalline
silica and the development of lung and stomach cancer, one may find facilities where the
employer is evaluating or has evaluated this exposure using thoracic samplers. Thoracic
dust is defined as that portion of inhaled dust that penetrates the larynx and is
available for deposition within the airways of the thorax. Thoracic dust includes the
respirable fraction. The collection of thoracic dust samples currently is not a method
used by the Agency. Area Offices need to be aware that thoracic sampling devices are
currently available and one may run across the use of these samplers during inspections.
For more information one can consult with the OSHA Salt Lake Technical Center (SLTC) or
the Office of Health Compliance Assistance.
SIC Codes where overexposures to crystalline silica dust have been documented22
||Crop preparation services
||Bridge, tunnel, and
elevated highway construction
||Painting and paper hanging
||Masonry and other stone
||Special trades contractors
||Fabricated structural metal
||Fabricated plate work
||Metal coating and engraving
and allied services
||Shipbuilding and repair
where sampling has been conducted for crystalline silica dust during the previous three
years and overexposures were not found.
||Oil and gas field services
not elsewhere classified
||Highway and street
||Glass and glazing work
||Wrecking and demolition
lacquers, enamels, and allied products
||Asphalt paving mixtures and
||Plastics plumbing fixtures
||Plastics products not
||Brick and structural clay
||Cut stone and stone
||Concrete products except
brick and block
||Steel investment foundries
||Aluminum die castings
||Non-ferrous die castings
||Enameled iron and metal
||Sheet meatal works
||Fluid power valves and hose
||Fabricated pipe and pipe
||Farm machinery and
||Oil and gas field machinery
||Pumps and pumping equipment
machinery and equipment
||Industrial and commercial
machinery and equipment not elsewhere classified
||Lighting equipment, not
||Industrial instruments for
||Funeral services and
||Help supply services
||General automobile repair
||Repair shops and related
recommendations for exposure to crystalline silica:28-48
- MEDICAL EXAMINATIONS
The following are the recommended medical procedures for individuals chronically exposed
to crystalline silica or for individuals who have received one or more severe acute
exposures to crystalline silica.
- A baseline examination which includes a medical and occupational history to elicit data
on signs and symptoms of respiratory disease prior to exposure to crystalline silica. The
medical examination emphasizing the respiratory system, should be repeated every five (5)
years if under 20 years of exposure and every two (2) years if over 20 years of exposure.
The medical examination should be repeated more frequently if respiratory symptoms develop
or upon the recommendation of the examining physician.
- A baseline chest x-ray should be obtained prior to employment with a follow-up every 5
years if under 20 years of exposure and every 2 years if over 20 years of exposure. A
chest x-ray may be required more frequently if determined by the examining physician.
- Pulmonary Function Tests (PFT): Should include FEV1 (forced expiratory volume in 1
second), FVC (forced vital capacity) and DLCO (diffusion lung capacity). PFTs should be
obtained for a baseline examination with PFTs repeated every 5 years if under 20 years of
exposure and every 2 years if over 20 years of exposure. PFTs may be required more
frequently is respirable symptoms develop or if recommended by the examining physician.
- A chest x-ray should be obtained on employment termination.
- MEDICAL MANAGEMENT
The chest x-ray should be a chest roentgenogram (posteroanterior 14" x 17" or
14" x 14") classified according to the 1970 ILO International Classification of
radiographs of Pneumoconiosis by a certified class "B" reader. The medical
follow-up should include the following procedures:
- With a positive chest x-ray (1/0 or greater) the worker should be placed in mandatory
respiratory protection, or if already wearing a respirator, the program should be
reevaluated to assure proper fit and that the elements of 29 CFR 1910.134 are being met.
- The worker should be referred to a physician specializing in lung diseases for a medical
evaluation and medical monitoring as warranted by the examining physician. A written
opinion from the examining physician as to whether the employee has any detected condition
that would place the worker at an increased risk should be provided to the employer and
employee, while specific medical findings remain confidential.
- All medical test results should be discussed with the worker by the physician.
- In accordance with 29 CFR 1910.20, medical records shall be maintained for at least 30
years following the employee's termination of employment, unless the employee is employed
for less than one year and the records are provided to the employee upon termination.
The following list
of standards includes those standards, that may, under appropriate inspection conditions
be cited for crystalline silica overexposure under this SEP. The standards listed below
are for general industry, maritime, and construction standards.
|Permissible exposure limit
||1926.55 & .57
|Accident prevention &
|Access to employee exposure
and medical records
|OSHA 200 forms
breathing air, enclosures, controls
||1926.28, 55, 95, 100, 101,
102, 103, and 300
||1915.131, 133, 151,152,
153, and 1000
||1926.27 and 51
|Safety and Health program
Sample Calculation for
a mixture of crystalline silica:8
Two consecutive samples from the same employee taken from a combined exposure to
crystalline silica dusts have the following results:
Calculation of the TWA from the sampling and analytical data:
Step No. 1: Calculate the percentage of quartz, cristobalite, and tridymite in the
respirable particulate collected
Step No. 2:
Percentage = (weight of quartz in Sample A) + (weight of quartz in sample B) x
Total weight of respirable particulate collected
= 0.052(0.855 mg) + 0.048(0.619 mg) x (100)/(0.855 mg + 0.619 mg)
= 0.044 mg + 0.03 mg x (100)/1.474 mg = 0.074 mg x (100)/1.474 mg = 0.05(100) = 5%
Percentage = (weight of cristobalite in sample A) + (weight of Cristobalite in
sample b) x (100)/Total weight of respirable particulate collected
= 0.023(0.855 mg) + 0.017(0.619 mg) x (100)/1.474 mg
= 0.02 mg + 0.011 mg x (100)/1.474 mg
= 0.031 mg x (100)/1.474 mg = 0.021(100) = 2.1% = 2%
- Tridymite: None Detected = 0%
Calculate the PEL for the mixture (use the formula in the OSHA Technical manual
Step No. 3:
PELmixture = 10 mg/m3/[ % quartz + 2(% cristobalite) + 2(% tridymite) + 2]
= 10 mg/m3/[5.0 + 2(2.0) + 2(0) +2]
= 10/11 = 0.91 mg/m3
Calculate the employee's exposure to respirable dust
Step No. 4:
Exposure = (sample weight A + Sample weight B)/Total volume of air sampled
= (0.855 mg + 0.619 mg)/ 731 liters (1 m3/1000 liters)
= 2.0 mg/m3
Adjust (where necessary) for sampling period less than 8-hours. Assume a zero
exposure time for the sampling period remaining.
Step No. 5:
Adjusted Exposure = (2.0 mg/m3)(430 minutes) + 0(50 minutes)/480 minutes
= 2.0 mg/m3 (430 minutes)/ 480 minutes = 1.8 mg/m3
Calculate the Severity of the exposure:
Severity = Adjusted Exposure/PELmixture
= (1.8 mg/m3)/(0.91 mg/m3) = 2.0
If the result from Step 5 is greater than 1.0 than an overexposure to the mixture of
crystalline silica exists.
Permissible Exposure Limits for Construction and
OSHA's silica standards, promulgated pursuant to section 6(a) of the OSH Act, adopted
the identical 1968 (General Industry) and 1970 (construction and maritime) ACGIH TLVs,
which were expressed in terms of mppcf, but contained a notification that ACGIH intended
to begin to express the silica TLV in gravimetric (mg/m3) terms.49-51
The 1968 and 1970 TLV tables therefore included two formulas.
Formula No. 1: PEL = 250/((% quartz) +5) mppc, or
Formula No. 2: PEL = 10/((% quartz +2) mg/m3
The 1968 and 1970 TLV documentation described the advantages of the newer
gravimetric sampling method, which yields results expressed mg/m3, over the
impinger sampling method, which yields results expressed in mppcf.49-51 These
advantages include the gravimetric sampling method's ability to account for the particle
size and respirability of collected dust, and the facts that only a single sample need be
collected to determine both the quartz content and the concentration of the dust and that
the samples do not need to be analyzed within 24 hours. Moreover, the results are likely
to be more accurate because, unlike impinger samples, they will not be affected by the
possible agglomeration of collected dust during processing. The documentation also
explained that the two formulas provided equivalent limits, and stated ACGIH's intent to
drop the mppcf formula entirely from future TLV editions.49-51 Beginning in
1972, silica TLVs have been expressed exclusively in gravimetric terms.51
ACGIH made clear that the purpose of this change was to take account of improved sampling
and analytical procedures, and not to change the TLV in any way:
"The impinger method requiring a counting procedure for evaluating relative
dustiness, although extremely valuable in judging dust reduction, falls short of the ideal
in relevance to health hazard, in simplicity, in reproducibility, and in unit cost. By the
use of size-selective (cyclones) sampling devices, a fraction of dust may be collected
which is capable of penetrating to the gas-exchange portion of the lung, where long-term
retention occurs. The concentration of airborne quartz in this size fraction should relate
more closely to the degree of health hazard. Mass methods also have advantages in
reproducibility, lower cost, and simplicity.
Data on long-term quartz exposures and their effects, using respirable mass
measurements of dust, are not yet available. However, comparisons of impinger-count
concentration and respirable-mass concentration show that the 9-10 MPPCF of granite dust
suggested by Russell contains 0.1 mg/m3 of respirable quartz.52 The
formula, TLV = 10/(%respirable quartz) mg/m3 generalizes this relationship to
all percentages of quartz in respirable dust. If the TLV were used only for dust
containing at least 5% quartz, the above TLV formula would be satisfactory, but to prevent
excessively high respirable dust concentrations when the fraction of quartz in the dust is
less than 5%, a constant has been added in the denominator, as with the counting TLV,
giving the formula, TLV = 10/(% respirable quartz + 2) mg/m3. The additive
constant "2" limits the concentration of respirable dust with <1% quartz to 5
mg/m3. The above TLV has been demonstrated to give evaluations comparable to
the impinger method in foundry dust exposures (emphasis added).53 Where
agglomerates are a factor, the results by the respirable mass method are more closely
related to the hazard." 51
general industry standard, 29 C.F.R.1910.1000, adopted in 1971, included both formulas as
equivalent exposure limits. The construction and maritime standards, adopted in 1974,
however, included only the mppcf formula. No reason was given for this distinction. In
fact, OSHA's 1971 adoption of both formulas in its general industry standard makes clear
the agency's agreement with ACGIH's position that the two formulas are substantively
Since the PELs were adopted, the impinger sampling method has been rendered
obsolete by gravimetric sampling. OSHA is not aware of any government agencies or
employers in this country that are currently using impinger sampling to assess worker
exposure to dust containing crystalline silica, and impinger samples are generally
recognized as being less reliable than gravimetric samples. OSHA has determined that
sampling procedures in the construction and maritime industries should be the same as in
general industry, and that the mppcf PELs in 29 C.F.R. 1915.1000 and 1926.55(a) are
equivalent to the mg/m3 PEL in 29 C.F.R. 1910.1000.
Appendix G: SEP References
to the SEP
- OSHA Instruction CPL 2.103, September 26, 1994, Field Inspection Reference Manual
- OSHA Instruction CPL 2.45B, March 3, 1995, The Revised Field Operations Manual (FOM).
- Rosenman, K.: Use of Hospital Discharge Data in the Surveillance of Occupational
Disease. Am. J. Ind. Med. Vol. 13: 281-289 (1988).
- Lofgren, D.J.: Case Study: Silica Exposure for Concrete Workers and Masons. Appl. Occup.
And Environ. Hyg. J. Vol. 8(10): 832- 835 (1993).
- K. Ringen, et al. Editors. Occupational medicine - Construction Safety and Health State
of the Art Reviews. Vol. 10, No. 2 Hanley and Belfus, Inc. April 1995.
- OSHA Memorandum date August 22, 1994 (Revision September 20, 1995) "Guidance to
Compliance Officers for Focused Inspections in the Construction Industry."
- Lippmann, M.: Exposure Assessment Strategies for Crystalline Silica Health Effects.
Appl. Occup. Environ. Hyg. Vol. 10 No. 12: 981-990 (December 1995).
- Occupational Safety and Health Administration Technical Manual: OSHA Instruction TED
1.15. References Related to Appendix A
- Markowitz, G.; Rosner, D.: The Limits of Thresholds: Silica and the Politics of Science,
1935 to 1990. American Journal of Public health. Vol. 85: 2,254 (1995).
- Rosner, D.; and Markowitz, G.: Deadly Dust: Silicosis and the Politics of Occupational
Disease in Twentieth Century America. Princeton: Princeton University Press, 1991, 1994.
- Flynn, et al.: Cristobalite Formation in Diatomaceous Earth - Effects of Time and
Temperature; Proceedings of the Symposium on Environmental Management for the 1990's.
Denver Colorado; Published AIME (Feb. 1991).
- Ganter, B.A.: Respiratory Hazard from Removal of Ceramic Fiber Insulation from High
Temperature Industrial Furnaces. Am. Ind. Hyg. Assoc. J. Vol. 47 (8): 530-534 (1986).
- Cheng, R.T.; McDermott, H.J.; Gia, G. M.; et al.: Exposure to Refractory Ceramic Fiber
in Refineries and Chemical Plants. Appl. Occup. Environ. Hyg. Vol. 7 No. 6: 361-367 (June
- Bergen, E.A.v. d.; Rocchi, P. S. J.; and Boogaard, P. J.: Ceramic Fibers and other
Respiratory Hazards During the Renewal of the Refractory Lining in a Large Industrial
Furnace. Appl. Occup. Environ. Hyg. Vol. 9 No. 1: 32-35 (January 1994).
- Applied Occupational and Environmental Hygiene Journal. Vol 10, Number 12, pgs. 981 -
1156. (December 1995.) Proceedings of the International Conference on Crystalline Silica
Health Effects: Current State of the Art.
- NIOSH Hazard Alert: Preventing Silicosis and Deaths from Sandblasting.
- Bang, K. M.; Althouse, R. B.; Kim, J. H.; et al.: Silicosis Mortality Surveillance in
the United States, 1968-1990. Appl. Occup. Environ. Hyg. Vol. 10 No. 12: 1070-1074 (1995).
- Olishifski, L.B.; rev Plog, B.A.: Overview of Industrial Hygiene, Fundamentals of
Industrial Hygiene 3rd Ed. Chicago, National Safety Council (1988).
- Schluter, D.P.: Silicosis and Coal Worker's Pneumoconiosis. Occupational medicine. Ed
Zens C. Et al. 3rd Edition St Louis, Mosby-Year Book, Inc. Pgs 171-173 (1994).
- Lilis, R.: Silicosis. Maxcy-Rosenau-Last Public Health and Preventative medicine, eds.
Last J.M.; et al. East Norwalk, Appleton and Lange pgs. 373-373 (1992).
- IARC. Silica and Some Silicates, Vol. 42. Lyon. International Agency for Research on
- Checkoway, H.; Heyer, N.J.; Demers, P.A.; et al.: Mortality among workers in the
diatomaceous earth industry. Brit. Jour. Ind. Med. Vol. 50: 586-597 (1993).
- Goldsmith, D.F.: Silica exposure and pulmonary cancer. In: Epidemiology of Lung Cancer,
pp. 245-298, Samet, J.M. Ed. New York: Marcel Dekker, Inc. (1994).
- Hnizdo, E.; and Sluis-Cremer, G.K.: Silica exposure, silicosis, and lung cancer: A
mortality study of South African gold miners. Brit. Jour. Ind. Med. Vol. 48: 53-60 (1991).
- McLaughlin, J.K.; Chen, J.Q.; Dosemeci, M.; et al.: A nested case-control study of
silica exposed workers in China. Brit. Jour. Ind. Med. Vol. 49: 167-171 (1992).
- Winter, P.D.; Gardner, M.J.; Fletcher, A.C.; and Jones, R.D.: A mortality follow-up
study of pottery workers: Preliminary findings of lung cancer. In: Occupational Exposure
to Silica and Cancer Risk (IARC Scientific Publications, No. 97), pp. 83-94, Simonato, L.
Et al.; Eds. Lyon International Agency for Research on Cancer (1990). Reference Related to
- Freeman, C.S.; and Grossman, E.: Silica Exposures in U. S. Workplaces: An Update. In
Press. Scand. J. Work and Environ. Health. Vol. 21, Supp. 2: 47-49 (1995). References
Related to Appendix C - Medical
- ILO (International Labour Office) Committee on Pneumoconiosis. Med Radiogr Photogr.
- ATA/CDC (American Thoracic Society and Centers for Disease Control). Treatment of
Tuberculosis Infections in Adults and Children. Am. Rev. Respir Dis. Vol. 134(2): 355-363
- Grahm, W.G.B.; O'Grady, R.V.; and Dubuc, B.: Pulmonary Function Loss in Vermont Granite
Workers. Am. Rev. Respir. Dis. Vol. 123: 25-28 (1981).
- Grahm, W.G.B.; Ashikaga, T.; Hememway, D.; et al.: Radiographic Abnormalities in Vermont
Granite Workers Exposed to Low levels of granite Dust. Chest. Vol. 100: 1507-1514 (1991).
- Grahm, W.G.B.; Weaver, S.; Ashikage, T.; and O'Grady, R.V.: Longitudinal Pulmonary
Function Losses in Vermont granite Workers. Chest. Vol. 106: 125-130 (1994).
- Grahm, W.G.B.: Silicosis. Occupational Lung Diseases. Vol. 13, No. 2: 253-267 (1992).
- Amandus, H.; Costello, J.: Silicosis and Lung Cancer in U.S. Metal Miners. Arch. Environ
Health. Vol. 46: 82-89 (1991).
- Balmes, J.R.: Medical Surveillance for Pulmonary Endpoints. Occupational Medicine. Vol.
5 No. 3: 499-513 (1990).
- Batra, P.; and Brown, K.: Radiology in Prevention and Surveillance of Occupational Lung
Disease. Occupational Medicine. State of the Art Reviews. Vol. 6, No. 1: 81-100 (1991).
- CDC. Silicosis: Cluster in Sandblasters - Texas and Occupational Surveillance for
Silicosis. MMWR Vol. 39, No. 25: 433-437 (1990).
- CDC. Silicosis Surveillance - Michigan, New jersey, Ohio, and Wisconsin 1987-1990. MMWR
Vol. 42, No. SS-5: 23-28 (1993).
- Finkelstein, M.M.: Silicosis Surveillance in Ontario: Detection Rates, Modifying
Factors, and Screening Intervals. Amer. J. of Ind. Med. Vol. 25: 257-266 (1994).
- Froines, J.R.; Wegman, D.H.; and Dellenbaugh, C.A.: An Approach to the Characterization
of Silica Exposure in U.S. Industry. Amer. Jour Ind. Med. Vol. 10: 345-361 (1986).
- Gelb, A.: Physiologic Testing in preventing Occupational Lung Disease. Occup. Med.:
State of the Art Reviews. Vol. 6, No. 1: 59-68 (1991).
- Koskinen, H.: Symptoms and Clinical Findings in Patients with Silicosis. Scand J. Work
Environ. health. Vol. 11: 101-106 (1985).
- Ng, T.; Chan, S.: Quantitative Relations between Silica Exposure and Development of
Radiological Small Opacities in granite Workers. Ann. Occup. Hyg.: (suppl 1) 857-863
- Snider, D.E.: The Relationship between Tuberculosis and Silicosis. Am. Rev. Respir. Dis.
Vol. 118: 455-460 (1978).
- Steenland, K.; and brown, D.: Silicosis Among Gold Miners Exposure - Response Analyses
and Risk Assessment. Am. J. Pub. Health. Vol. 85: 1372-1377 (1995).
- Valiante, D.; Richards, T.; and Kinsley, K.: Silicosis Surveillance in New Jersey:
Targeting Workplaces Using Occupational Disease and Exposure Surveillance Data. Amer.
Jour. Ind. Med. Vol. 21: 517-526 (1992).
- Valiante, D.J.; and Rosenman, K.D.: Does Silicosis still occur? JAMA: 3003-3007 (1989).
- Zisking, M.; Jones, R.N.; and Weill, H.: Silicosis. Am. Rev. Respir. Dis. Vol. 113:
643-665 (1976). References for the Construction and Maritime PELs -- Appendix F
- Threshold Limit Values of Airborne Contaminants and Intended Changes. Adopted by the
ACGIH for 1968.
- Threshold Limit Values of Airborne Contaminants and Intended Changes. Adopted by the
ACGIH for 1970.
- Documentation of the Threshold Limit Values; for Chemical Substances in the Work
Environment. American Conference of Governmental Industrial Hygienists. (1971 and 1980).
- Ayer., H.E.: The Proposed ACGIH Mass Limits for Quartz: Review and Evaluation. Am. Ind.
Assoc. Hyg. J. Vol. 30: 117-125 (1968).
- Ayer., H.E.; Sutton, G.W.; and Davis, I.H.: Size-Selective Gravimetric Sampling in
Foundries. Am. Ind. Hyg. Assoc. J. Vol. 29:4 (1968).
- Ayer., H.E.; Dement, J.E.; Busch, K.A.; et al.: A Monumental Study -- Reconstruction of
a 1920 Granite Shed. Amer. Ind. Hyg. Assoc. J. Vol. 34:206-211 (1973).
- Hearl, F.J.: In Silica and Silica-Induced Lung Diseases; V. Castranova, V. Vallyathan,
and W.E. Wallace, Eds.: Section I, Chapter 3: Guidelines and Limits for Occupational
Exposure to Crystalline Silica. CRC Press, Inc. (1996).
- Rice, C.; Harris, R. L.; Lumsden, J. C.; et al.: Reconstruction of Silica Exposure in
North Carolina Dusty Trades. Am. Ind. Hyg. J. 45(10): 689-696 (1984).
- Sutton, G. W.; and Reno, S. J.: Sampling in Barre, Vermont, Granite Sheds. Paper
Presented at the American Industrial Hygiene Conference, Chicago. Ill. (1967).
- Sheehy, J. W.; and McJilton, C. E.: Development of a Model to Aid in Reconstruction of
Historical Silica Dust Exposure in the Taconite Industry. Am. Ind. Hyg. Assoc. J. 48(11):
- Ayer., H. E. Origin of the U. S. Respirable Mass Silica Standard. Appl. Occup. Environ.
Hyg. J. Vol. 10(12) 1027-1030 (1995). General Silica References
- Criteria for a Recommended Standard: Occupational Exposure to Crystalline Silica.
Washington, D.C. U.S. Department of Health Education and Welfare, Public health Service,
Centers for Disease Control, NIOSH, DHEW (NIOSH) Pub. No. 75-120, (1974).
- NIOSH. NIOSH 1992 Alerts. NIOSH publications 92-102 and 92-107. Cincinnati, OH.
- OSHA Instruction CPL 2-2.38C, October 22, 1990, Inspection Procedures for the Hazard
- Corn, J. K.: Historical Aspects of Industrial Hygiene: II. Silicosis. American
Industrial Hygiene Journal. Vol. 41(2): 125-133 (1980).
- OSHA Instruction CPL 2-2.43A; OSHA Chemical Information manual [also see OSHA
Computerized Information System (OCIS) online or the OSHA Compact Disk (CD) for current
sampling information. Dated July 1, 1991.
- Ness, S. A. Air Monitoring for Toxic Exposures. Van Nostrand Reinhold, New York. (1991).
- Groce, D. W.; Linch, K. D.; Jones, W. G.; and Costello, J.: Silicosis: A Risk in
Construction. NIOSH, Div. Of Resp. Disease Studies. Presented at the AIHCE (1993).
- Linch, K. D.; and Cocalis, J. C.: Commentary: An Emerging Issue - Silicosis Prevention
in Construction. John B. Moran, Column Editor. Appl. Occup. Environ. Hyg. J. Vol. 9(8):
- Hardy, T.S.; Weil, H.: Crystalline Silica: Risks and Policy. Environ. Health Perspec.
Vol. 103:152 (1995).
- OSHA Priority Planning Process, Recommendations for Assistant Secretary Joseph A. Dear
and Director Linda Rosenstock, Silica (Crystalline) (July, 1995).
- Alpaugh, E.L.; rev Hogan, T.J. Particulates. Fundamentals of Industrial Hygiene. Ed
Plog, B.A. 3rd ed. Chicago, National Safety Council, 141 (1988).
- Holland, L.M.: Animal Studies of Crystalline Silica: Results and Uncertainties. Appl.
Occup. Environ. Hyg. Vol. 10, No. 12: 1099-1103 (1995).
- Costello, J.; and Grahm, W.G.B.: Vermont Granite Workers' Mortality Study. Amer. Jour.
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