Civil Engineering Reference
In-Depth Information
Counties where amphibole asbestos fibers have been reported
Counties where chrysotile or serpentine rock or both have been reported
Solid lines surround those areas where fiber-bearing rocks might exist. The
dashed line shows lowest limit of glacial activity. Rocks not native to the area can
be found north of this line.
Fig. 2-1.
Locations of asbestos sources in the United States (Reprinted from
Journal AWWA,
Vol. 66, No. 9 [September 1974], by permission. Copyright
1974, American Water Works
Association.)
less than 1 MFL, 8 percent were between 1 and 10 MFL, and 10 percent had over 10
MFL. In 1981, EPA sampled 100 systems and found 0.08 MFL in 12 systems, with
values ranging from 0.385 to 1.071 MFL.
2
Health Effects
Inhaled asbestos is clearly carcinogenic. Human occupational and
laboratory animal inhalation exposures are associated with lung cancer, pleural and
peritoneal mesothelioma, and gastrointestinal tract cancers.
3
The physical dimensions
of asbestos fibers rather than the type are more important in health effects, with the
longer, thinner fibers more highly associated with cancers by inhalation. In drinking
water, some inhalation may take place through showers and humidifiers.
With respect to ingested asbestos, health effect findings are inconsistent, with some
studies suggesting elevated risk for gastric, kidney, and pancreatic cancers.
9
The EPA
has classified ingested asbestos as a possible human carcinogen (Group C).
The American Water Works Association Research Foundation has stated
2
:
No firm evidence shows that the proper use of asbestos-cement pipe poses a hazard to
health by reason of ingestion of asbestos fibers. Calculations comparing the probably in-
gestion exposure in occupational groups to that likely to occur as a result of ingestion of
potable water from asbestos-cement pipe systems suggest that the probability of risk to
health from the use of such systems is small, approaching zero.
