CALIFORNIA AIR RESOURCES BOARD
Auditorium, First Floor
400 "P" Street
October 12, 1990
90-17-1 Public Hearing to Consider the Adoption of 001
a Regulatory Amendment Identifying Trichloro-
ethylene (TCE) as a Toxic Air Contaminant.
90-17-2 Public Meeting to Consider Second Semi-Annual ---
Report on the South Coast Plan.
ITEM NO.: 90-17-1
Proposed Identification of Trichloroethylene (TCE) as a Toxic Air
The Air Resources Board (ARB/Board) staff recommends that
trichloroethylene be identified as a toxic air contaminant
without a specified threshold exposure level.
The ARB staff, after consulting with the Department of Health
Services (DHS), selected trichloroethylene for the Board's
consideration for listing as a toxic air contaminant. The staff
selected TCE for the following reasons: The US EPA lists TCE as a
probable human carcinogen; there are a wide variety of sources in
California; and TCE is mobile in the environment and is not
naturally removed or detoxified at a rate that would
significantly reduce public exposure.
A report was prepared jointly by the ARB and DHS staffs which
reviews the exposure levels and health effects of exposure to TCE
in California. Major sources of TCE are: degreasing operations,
paints and coatings, adhesive formulations, and polyvinyl
Ambient TCE testing results from the ARB's air toxics monitoring
network indicates that at least 20.3 million people are exposed
to a population-weighted annual TCE concentration of 0.22 ppb.
"Hot spot" exposure to airborne TCE may increase the potential
cancer risk to nearby residents. The result of modeling
emissions from three of the largest sources of TCE in the state
indicates that nearby residents may be exposed to a maximum
annual average concentration ranging from two to five times above
ambient TCE concentrations.
The DHS staff found that TCE has been identified as a animal
carcinogen and should be regarded as a probable human carcinogen.
The DHS' health effects evaluation includes an assessment of the
potential excess lifetime cancer risk from continuous exposure to
DHS estimates the overall population-weighted average TCE
lifetime cancer risk from ambient exposure to 0.22 ppb ranges
from 1 to 10 cases per million people exposed; assuming a
California population of 20.3 million, an excess of 20 to 203
potential lifetime cancer cases might result from such continuous
exposure to airborne TCE.
The Scientific Review Panel (SRP), reviewed the report and found
that the TCE report is without serious deficiency and submitted
its written findings to the Board. The SRP has recommended that
the Board list TCE by regulation as a toxic air contaminant, and
found that, based on available scientific information, TCE
exposure dos not have a threshold below which carcinogenic
effects are not expected to occur.
IMPACT OF ACTION
The identification of TCE as a toxic air contaminant will not in
itself have any environmental and economic impacts. However,
specific control measures may be developed subsequent to
identification and an analysis of potential environmental and
economic impacts will be included in the consideration of such