New
Jersey Department of Health and Senior Services
Certain Workers Are At Risk of Developing Silicosis
Crystalline silica is found in many common materials, such as those
listed in the box to the right. When these materials are made into
a fine dust in work activities such as those listed in the box on
page 2, the inhalation and deposition of these fine particles can
produce silicosis over time.
Workers in many industries and occupations are at risk, including:
- Construction, especially bridge, tunnel, and elevated highway
- Wrecking and demolition
- Concrete work
- Surface mining and quarrying
- Underground mining
- Stone cutting
- Milling stone
- Agriculture
- Foundry
- Ceramics, clay, pottery
- Vitreous enameling of china plumbing fixtures
- Glass manufacturing
- Manufacturing of concrete products and brick
- Manufacturing of soaps and detergents
- Shipyards, railroads
Other employees who do not work directly with materials containing
silica may be exposed as bystanders if they are in the area
when crystalline silica containing materials are being used.
Materials
Containing Crystalline Silica
- Granite
and marble
- Quartz
and quartzite
- Sand,
gravel, and sandstone
- Slate
and Traprock
- Many
abrasives used for abrasive blasting
- Concrete,
concrete block, cement
- Brick
and refractory brick
- Mortar
- Gunite
- Soil,
especially sandy soil
- Asphalt
containing rock or stone
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Silica dust exposure to worker jack hammering concrete
pavement to weaken bridge for demolition.
Definition and Clinical Features
Silicosis is a diffuse, nodular, interstitial pulmonary fibrosis caused
by a tissue reaction to inhaled crystalline silica dust. It can take
the acute form under conditions of intense exposure but usually
takes the chronic form, requiring several to many years to
develop. People who have silicosis have increased susceptibility to
infections such as tuberculosis, complicating the patient.s prognosis.
There is also increasing evidence that crystalline silica causes cancer
and that individuals with silicosis are at increased risk of developing
lung cancer.
Except in its acute form, silicosis begins with few, if any, symptoms.
When clinical symptoms of silicosis are present, they could include
cough and shortness of breath of increasing severity. On physical
examination, breath sounds may be normal or distant and, with increased
severity, there may be signs of right heart failure. Evidence of pathological
response to silica exposure exists well before symptoms occur.
Chronic reactions, occurring after 10 or more years from first
exposure, involve nodular lesions, (bilateral, multiple, rounded opacities)
often more prominent in the upper lobes. In this simple
stage of silicosis, nodules are usually small (1 cm or less). There
may be little effect on pulmonary function at this stage.
Work
Activities Associated With Silica Exposure
- Drilling,
cutting, sawing, grinding, chipping, jack hammering
- Crushing,
screening, sorting
- Loading,
hauling, dumping, bagging
- Dry
sweeping or pressurized air blowing
- Abrasive
blasting
- Clean-up/maintenance
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Construction worker exposure to silica
dust during interstate highway repair.
Complicated silicosis or progressive massive fibrosis
(PMF) also usually develops in the upper lobes but the nodules go
on to consolidate and exceed 1 cm and encompass blood vessels and
airways. Lung function may be severely compromised, often with a mixed
restrictive/obstructive pattern, but either pure restriction or obstruction
may be seen.
Acute reactions may appear within a few weeks to two years
after the onset of massive exposure. The distinguishing feature of
acute silicosis is intraalveolar deposits, similar to those seen with
alveolar proteinosis. In contrast to the nodular fibrosis seen in
the chronic form, diffuse interstitial fibrosis is not found. Silicosis
developing in less than 10 years, the accelerated form, has been described
most often in sandblasters. In these cases, diffuse fibrosis is likely
to develop and may be located throughout all lobes of the lung.
Progression of disease and radiographic findings can continue
even after exposure has ended.
Recommended Medical Surveillance
The following are recommended by the New Jersey Department of Health
and Senior Services as a baseline before exposure, then periodically
as noted:
1. Occupational history to determine years of exposure --
update annually. Inquire about the materials used, tasks performed,
occupations, and industries in which employed, including those listed
in the boxes on pages 1 and 2.
2. Medical exam emphasizing the respiratory system -- annually.
3. Chest x-ray to look for evidence of abnormality. Posteroanterior
14" x 17" or 14" x 14", classified according to the 1980 Guidelines
for the Use of ILO International Classification of Radiographs of
Pneumoconiosis by a certified class .B. reader, is recommended.
The ILO system has the distinct advantage of a standardized set of
comparison x-ray films. Names of B-readers are available from NIOSH.
Information on how to contact NIOSH is given at the end of this bulletin.
The above box gives recommendations for the frequency of x-rays. NOTE
the potential for excessive x-rays if the employee has also worked
with asbestos or other hazards for which OSHA may require employers
to provide x-rays.
4. Pulmonary Function Tests (PFT) to look for evidence of respiratory
impairment. Should include FEV1 (forced expiratory volume in 1 second),
FVC (forced vital capacity), and DLCO (diffusion capacity of the lungs)
-- annually. All PFT should use equipment and follow recommendations
issued by the ATS (American Thoracic Society) and be administered
by a technician who has successfully completed NIOSH-certified training.
5. A baseline PPD skin test for tuberculosis because people who
have silicosis have increased susceptibility. Repeat annually if there
is x-ray evidence of silicosis (1/0 or greater profusion category
using the ILO classification) or 25 years or longer exposure.
Clinical
Signs of Silicosis
Simple
- mild
restrictive and/or obstructive defects
- small,
rounded opacities on x-ray
Accelerated
- diffuse,
small rounded opacities on x-ray
- more
severe restrictive and/or obstructive defects
Advanced
- increased
profusion of small opacities and development of large opacities
on x-ray
- more
severe restrictive and/or obstructive defects
- cor
pulmonale
Acute
- diffuse
perihilar alveolar filling process with ground glass opacities
on x-ray
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Reporting Guidelines
Physicians, radiologists, pathologists and other health care professionals
should report cases of silicosis to the health department in their
state so that it can be determined whether silica exposures are being
controlled at the workplaces where the patient has been employed.
Such reporting is mandatory in many states, including New Jersey.
In NJ, call 800-772-0062 to report cases or for reporting forms.
If the state has no occupational health program, cases of concern
should be discussed with NIOSH (National Institute for Occupational
Safety and Health) or the local OSHA (Occupational Safety and Health
Administration) or MSHA (Mine Safety and Health Administration) office.
Information on how to contact these agencies is given at the end of
this bulletin.
The following elements define a case of silicosis for reporting
purposes:
- A physician.s
provisional or working diagnosis of silicosis, OR
- Chest x-ray
or other imaging technique interpreted as consistent with silicosis,
OR
- Pathologic
findings consistent with silicosis.
Frequency
of Chest X-rays for Silicosis
- Every
3-5 years with normal x-ray, low exposure, and less than
20 years exposure.
- Every
1-3 years with normal x-ray, high exposure, or greater than
20 years exposure.
- Annually
with x-ray evidence of silicosis (ILO 1/0 or greater or
ILO results A, B, or C large opacities), massive exposure,
or positive PPD test.
- See
NOTE in item 3.
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Because silicosis is sometimes confused with sarcoidosis, asbestosis,
coal miner.s pneumoconiosis, or other pneumoconiosis it is important
that all chest x-rays be reviewed by a B-reader.
Medical Management of Silicosis
There is no known medical treatment to reverse silicosis, therefore
prevention is critically important. Removal from exposure may decrease
the rate of disease progression. Corticosteroids are not useful to
reduce the progression of the disease. Appropriate treatment for heart
failure and tuberculosis should be begun if these complications exist.
All individuals should be strongly advised to stop smoking and offered
smoking cessation information and support. Regular follow-up exams
to assess progression and possibly to screen for lung cancer should
be scheduled. Individuals who develop silicosis should be given the
option of transfer to silica-free jobs. In order for this to be a
realistic alternative, the individual should be able to maintain the
same rate of pay and benefits without loss of seniority.
For Additional Information
NIOSH: e-mail -- pubstaft@niosdt1.em.cdc.gov.
1-800-35-NIOSH (1-800-356-4674) or 513-533-8328, fax 513-533-8573,
Internet site -- http://www.cdc.gov/niosh/topics/silica/
- CDC/NIOSH
Alert, Request for Assistance in Preventing Silicosis and Deaths
in Rock Drillers, DHHS (NIOSH) Publication No. 92-107, August
1992.
- CDC/NIOSH
Alert, Request for Assistance in Preventing Silicosis and Death
in Construction Workers, DHSS (NIOSH) Publication No. 96-112,
May 1996.
- CDC/NIOSH
Alert, Request for Assistance in Preventing Silicosis and Deaths
from Sandblasting, DHHS (NIOSH) Publication No. 92-102, August
1992.
- Lists of
certified B-readers by state, approved pulmonary function technician
courses, state health department contacts for reporting purposes.
MSHA: Call headquarters for the number of your local office:
703-235-8307 Internet site -- http://www.msha.gov
has a directory of all offices.
OSHA: Internet site -- http://www.osha.gov
has a directory of all offices. Or, call the national office for the
number of your local office: 202-219-8151.
ATS (American Thoracic Society): Adverse Effects of Crystalline
Silica Exposure. American Journal Respiratory and Critical Care Medicine,
1997; 155:761-765.Standardization of Spirometry - 1994 update. American
Journal Respiratory and Critical Care Medicine, 1995; 152: 1107-1136.
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