Environmental Engineering Reference
In-Depth Information
Lung cancer has been a major public health concern in the context of
potential exposures that may be experienced by building occupants, such as
school children, teachers, and service personnel (custodians, maintenance
workers). This concern reflects the fact that there is apparently no threshold
for asbestos exposure and the induction of lung cancer.
Asbestos exposure can cause mesothelioma, a rare cancer of the mesothe-
lium (i.e.,
the tissue which comprises pleura and peritoneum) of the chest
and abdominal cavities. Pleural mesothelioma is 5 times more common than
abdominal or peritoneal mesothelioma. The annual incidence of mesothe-
lioma in the U.S. has been estimated to be in the range of 1500 to 2500 cases.
Most mesotheliomas appear to be associated with industrial/occupational
exposures or household contact with an asbestos worker. However, in 10 to
30% of reported cases, there is no evidence of exposures to asbestos or talc
(which often contains asbestos fibers). Mesothelioma is incurable and, as a
consequence, has a 100% fatality rate.
The scientific literature indicates that mesothelioma risk is greater among
workers exposed to amphiboles, such as crocidolite, than to chrysotile, the
most widely used asbestos fiber in the U.S. There is considerable uncertainty
as to whether chrysotile asbestos can cause mesothelioma. A potential caus-
ative role for the amphibole, tremolite, has been proposed for mesothelioma
among some chrysotile-exposed workers. Tremolite is commonly reported
as a minor constituent of chrysotile mineral extracted and used for ACBM
and other products.
The risk of developing mesothelioma increases with increasing cumula-
tive exposure and is independent of age or smoking history. The earlier one
is exposed, the higher the probability of developing mesothelioma in one's
lifetime. This phenomenon is due to the fact that early-in-life exposures mean
that an individual has a longer period of time in which to develop the disease.
Such potential early-in-life exposures have, in part, underlain asbestos expo-
sure concerns for children in ACBM-containing school buildings in the U.S.
Additional concern lies in the fact that mesothelioma may also be caused by
brief high exposures.
Epidemiological studies of asbestos-exposed workers have reported
increased prevalence rates of cancers of the larynx (voice box), oropharynx
(mouth/throat), and upper and lower digestive tract. The risk of such cancers
in asbestos workers appears to be small; the risk to building occupants is
several orders of magnitude smaller.
4.
Cancer risks associated with building asbestos exposures
During the mid- to late 1980s, public health concern focused on potential
asbestos fiber exposures of building occupants and workers in buildings
containing ACBM and their risks of developing lung cancer or mesothe-
lioma. As a consequence, the Health Effects Institute (Cambridge, MA) con-
vened a panel to evaluate the lifetime cancer risk of general building occu-
pants as well as service workers. Unlike general building occupants,
