Lincoln Plaza
Auditorium, First Floor
400 "P" Street
Sacramento, CA

October 10, 1991
9:30 a.m.



91-8-1 Public Hearing to Consider the Adoption of a 001
Regulatory Amendment Identifying Perchloroethylene
as a Toxic Air Contaminant.

91-8-2 Public Meeting to Consider a Plan for the Control 029
of Emissions from Marine Vessels.

NOTE: If the Board is unable to complete consideration
of this item on October 10, 1991, it may continue its
consideration on October 11, 1991, at 8:30 a.m. at the
same location.

**PLEASE NOTE: Item 91-8-2 was hear SECOND on Friday, October 11,

ITEM NO.: 91-8-1

Proposed Identification of Perchloroethylene as a Toxic Air
Contaminant (Regulatory).


The Air Resources Board (ARB) staff recommends that
perchloroethylene be identified as a toxic air contaminant
without a threshold because there is inadequate scientific
evidence of an exposure level below which no significant adverse
health effects are anticipated.


In accordance with the provisions of California Health and Safety
Code section 39650 et seq., the ARB staff, after consulting with
staff of the Office of Environmental Health Hazard Assessment
(OEHHA), selected perchloroethylene for the Board's consideration
for listing as a toxic air contaminant. The staff selected
perchloroethylene for the following reasons: 1) the International
Agency for Research on Cancer (IARC) and the Environmental
Protection Agency (EPA) list perchloroethylene as a possible
human carcinogen, 2) perchloroethylene is used, emitted, and
detected in outdoor and indoor air in California (major sources
are dry cleaners, degreasers, paints and coatings, and
adhesives), 3) atmosphere at a rate that would significantly
reduce public exposure, and 4) the EPA lists perchloroethylene as
a Hazardous Air Pollutant (HAP), and Health and Safety Code
section 39655 requires that HAPs be identified as toxic air

As required by Health and Safety Code section 39661, a report
estimating perchloroethylene exposure levels as resultant health
effects in California was jointly prepared by the staffs of the
ARB and OEHHA. The estimated cancer unit risk for continuous
lifetime exposure to 1 ppbv perchloroethylene ranges from 2 to 72
per million. The staff estimates that the potential excess
cancer risk from lifetime exposure to California's estimated
population-weighted annual ambient perchloroethylene
concentration (0.37 ppbv) is from 1 to 26 cancers per million
people. Using the OEHHA's best value cancer unit risk factor for
perchloroethylene (54 x 10-6 per ppbv), results in an estimated
potential lifetime risk of 20 cancers per million people and an
estimate of up to 600 potential lifetime excess cancers

"Hot spot" perchloroethylene exposures increase the potential
risk of cancer above the annual average statewide level. An
excess potential risk of 480 cases per million is estimated for
maximally exposed individuals near eight perchloroethylene
emitting facilities in Southern California. This estimate is
based on potential maximum exposures from modeled emissions and
use of OEHHA's best value of cancer unit risk.

The Scientific Review Panel (SRP), established by Health and
Safety Code section 39670, reviewed the perchloroethylene report.
The SRP found the report with serious deficiencies and submitted
its written findings to the Board. In the findings, the Panel
recommended that the Board list perchloroethylene by regulation
as a toxic air contaminant, and found that, based on available
scientific information, perchloroethylene does not have a
threshold below which carcinogenic effects are not expected to


The identification of perchloroethylene 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 control measures. In addition, local
air pollution control districts have the authority to require
that public exposures to particular toxic substances not exceed
levels deemed by the district to be protective of public health.
Districts have exercised this authority in the form of permitting
and notification requirements for facilities. Information used
in the identification of perchloroethylene as a toxic air
contaminant may be used by districts in implementing these