Environmental Engineering Reference
In-Depth Information
Asbestos Diseases
Asbestosis is caused by fine silicate fibers retained in the lungs. There are six
grades of asbestos. The most common are crocidolite (blue asbestos), amosite
(brown asbestos), and chrysotile (white asbestos), which come from serpentine,
and the less common are actinolite, tremolite, and anthrophyllite. Fibers are 0.1
to 10
µ
m in length, a size not generally visible. Positive identification requires
laboratory analysis. The crocidolite fibers, the most hazardous, are straight and
stiff (crocidolite has rarely been used since World War II), the amosite are less
so; the chrysotile are curly. Fibers that are stiff and elongated lodge across the
bronchi and eventually pass into the lung tissue and pleural cavity. Hence, more
of the crocidolite is retained in the lungs and may be the cause of most asbestosis.
However, chrysotile
∗
is as likely as crocidolite and other fine silicate fibers to
induce mesotheliomas after intrapleural entry and also as likely to induce lung
neoplasms after inhalation exposures, although it is of less risk than crocidolite.
The four most common diseases that might result from asbestos, usually after
prolonged exposure, are listed here. The disease may appear 10 to 35 years after
first exposure:
1.
Asbestosis
— a diffuse interstitial nonmalignant, scarring of the lungs
2.
Bronchogenic carcinoma
— a malignancy of the interior of the lungs
3.
Mesothelioma
— a diffuse malignancy of the lining of the chest cavity
(pleural mesothelioma) or of the lining of the abdomen (peritoneal mesothe-
lioma)
4. Cancer of the stomach, colon, and rectum
A potential health risk exists when asbestos fibers become airborne, as in the
deterioration and exposure of asbestos in old asbestos paper-lined air distribution
ducts, acoustic plaster ceilings, decorative and textured-spray finishes or paints
and fire-retardant coatings on steel beams, and the demolition of old buildings.
Spackling and other patching compounds may contain asbestos, which would
be released to the ambient air in mixing and sanding to prepare the surface for
painting. Fireplaces that simulate live embers and ash usually contain asbestos
in an inhalable form. Other sources include furnace patching compounds, old
steam pipe covers, floor materials, brake linings, paints, and certain domestic
appliances. Asbestos is also found in some surface waters, urban stormwaters,
and soils and generally in urban areas. However, occupational exposure is the
major risk.
The EPA, under authority of the Toxic Substances Control Act of 1976, ruled
on July 6, 1989, that all manufacture, import, or processing of felt products,
asbestos - cement sheets, floor tiles, and clothing containing asbestos be ended
by August 1990 and that distribution be ended in 1992; that disc brake linings
∗
Chrysotile fibers are estimated to make up 90 percent of all asbestos (“The asbestos dilema,”
U.S.
News & World Report
, January 14, 1990, pp. 57 - 58).
