Environmental Engineering Reference
In-Depth Information
amphibole fibers. In a study of U.S. municipal buildings, TSI contained
asbestos fibers in the following proportions: chrysotile only — 60%, mixed
chrysotile and amphibole — 35%, and amphibole only — 7%. For SM, pro-
portions were: chrysotile only — 73%, mixed fibers — 10%, and amphibole
only — 17%. In the latter case, ceiling tile was classified as SM rather than
MM. This is significant in that most of the amphibole-only surfacing material
was found in asbestos-containing ceiling tiles.
Various surveys have been conducted to assess the prevalence of build-
ings with friable ACBM (SM, TSI, and ceiling tile). In 1988, USEPA estimated
that approximately 700,000 U.S. public and commercial buildings (about
20%), out of a population of 3.5 million, contained some type of friable
ACBM. A study conducted by the Philadelphia Department of Health found
that 47% of 839 municipally owned or occupied buildings contained friable
ACBM. In a California study, 78% of its public buildings constructed before
1976, and 56% of all public buildings, were estimated to contain ACBM. A
similar study estimated that 67% of the 800,000 buildings in New York City
contained ACBM. Most of this material (84%) was TSI, 50+% of which was
found in mechanical rooms. Eighty +% of this material was assessed as being
moderately to severely damaged.
The percentage of buildings containing ACBM increases considerably
when other nonfriable or mechanically friable materials, such as vinyl asbes-
tos tile, asbestos cement board, mastics, and drywall taping products, are
included. Asbestos fibers in floor tile, cement board, and mastics are bound
in a hard material that prevents them from being easily released. As such,
they are not hand-friable. They are, however, mechanically friable (broken,
cut, drilled, sanded, or abraded in some way). Mechanically friable ACBM
can pose an exposure hazard under certain conditions and activities. Con-
sequently, such activities are regulated under federal and state demolition
and renovation requirements.
2.
ACM in residences and other structures
Asbestos in residences has received relatively limited regulatory attention.
This has been due, in part, to the fact that ACBM was not as widely used in
residences (except large apartment houses) as it was in large institutional
and commercial buildings. ACBM in residences includes a variety of prod-
ucts, e.g., TSI around hot or cold water lines, asbestos paper wrap around
heating ducts, cement board around furnaces/wood-burning appliances,
cement board (Transite) siding, cement board roofing materials, asbestos-
containing asphalt roofing, wallboard patching compounds, asbestos-con-
taining ceiling materials that were spray-applied or troweled on, and vinyl
asbestos tiles.
With the exception of TSI and SM used on ceilings, most ACBM in
residences contains asbestos in a bound matrix. It is therefore mechanically
friable and should only produce an exposure risk if significantly disturbed.
Materials used on building exteriors should also pose little risk of human
exposure.
