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

July 9, 1992
9:30 a.m.



92-10-1 Public Hearing to Consider the Adoption of a 001
Regulatory Amendment Identifying 1,3-Butadiene
as a Toxic Air Contaminant.

92-10-2 Public Meeting to Receive a Presentation on the ---
South Coast Air Quality Management District Regional
Clean Air Incentives Market.

92-10-3 Public Meeting to Consider Approval of the 1991 028
Attainment Plan for Districts Within the Northern
Sacramento Valley, Specifically the Feather River
Air Quality Management District and the Shasta,
Tehama, Glenn, Colusa, and Butte County Air Pollution
Control Districts, as Required by the California Clean
Air Act of 1988.

ITEM NO.: 92-10-1

Proposed Identification of 1,3-Butadiene as a Toxic Air
Contaminant (Regulatory).


The Air Resources Board (ARB) staff recommends that 1,3-butadiene
be identified as a toxic air contaminant without a cancer
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 1,3-butadiene for the Board's consideration for
listing as a toxic air contaminant. The staff selected 1,3-butadiene for
the following reasons: 1) the International Agency
for Research on Cancer (IARC) and the Environmental Protection
Agency (EPA) list 1,3-butadiene as a possible and probable human
carcinogen respectively, 2) 1,3-butadiene is used, emitted, and
detected in outdoor and indoor air in California, 3) major
sources of outdoor exposure are from incomplete combustion of
petroleum derived fuels by mobile sources and stationary sources,
4) indoor concentrations of 1,3-butadiene may be higher than
outdoor due to environmental tobacco smoke if smokers are
present, 5) 1,3-butadiene is not naturally removed from the
atmosphere at a rate that would significantly reduce public
exposure, and 6) the EPA lists 1,3-butadiene as a Hazardous Air
Pollutant (HAP), and Health and Safety Code section 39655
requires that HAPs be identified as toxic air contaminants.

As required by Health and Safety Code section 39661, a report
estimating 1,3-butadiene exposure levels and resultant health
effects in California was jointly prepared by the staffs of the
ARB and the OEHHA. The estimated cancer unit risk for continuous
lifetime exposure to 1 ppbv 1,3-butadiene ranges from 10 to 800
per million. Using the OEHHA's best value cancer unit risk
factor of 3.7 X 10-4 per ppbv and the corresponding ambient
concentrations, the number of potential excess cancer cases due
to exposure to 1,3-butadiene is estimated to be 140 per million.
this corresponds to an estimated potential lifetime risk of up to
4,200 for a California population of 30 million.

Near source exposures to 1,3-butadiene are expected to increase
the potential risk of cancer above the annual statewide level.
The EPA has estimated an excess potential risk of approximately
10 to 100 excess cancers per million for maximally exposed
individuals near two facilities in California. In addition,
information from the Air Toxic "Hot Spots" Act (AB 2588) will be
used to prioritize and estimate potential near source exposure in
the control phase if 1,3-butadiene is identified as a toxic air

The Scientific Review Panel (SRP), established by Health and
Safety Code section 39670, reviewed the 1,3-butadiene report.
The SRP found the report without serious deficiencies and
submitted its written findings to the Board. In the findings,
the Panel recommended that the Board list 1,3-butadiene by
regulation as a toxic air contaminant, and found that, based on
available scientific information 1,3-butadiene does not have a
threshold below which carcinogenic effects are not expected to


The identification of 1,3-butadiene 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. this has taken the
form of permitting and notification requirements for facilities.
Information used in the identification of 1,3-butadiene as a
toxic air contaminant may be used by districts in implementing
these requirements.

ITEM NO.: 92-10-3

Public Meeting to Consider Approval of the 1991 Air Quality
Attainment Plan for Districts Within the Upper Sacramento Valley;
Specifically: Butte, Colusa, Feather River (PART), Glenn, Tehama,
and Shasta.


That the Board approve most of the plan for the Upper Sacramento
Valley; that the Board conditionally approve a moderate
classification for ozone pending completion of a proportional
rollback analysis as proposed by staff; that the Board direct
those districts not in compliance with the 25 ton per year
permitting program requirement to adopt conforming rules within 6
months of ARB's hearing on the plan.


The six districts within the Upper Sacramento Valley (USV)
jointly developed and submitted a single plan. Requirements for
most of the plan elements have been satisfied by all districts
within the USV. However, one plan requirement, the permitting
program for new and modified stationary sources 25 tons per year
or greater, has been met by only Shasta and Tehama. Requirements
for reasonably available transportation control measures (TCMs),
as appropriate for individual districts, have been fully
satisfied by all districts except for Feather River. Shasta and
Butte, two of the fastest growing areas in the USV, have
completed separate TCM plans. Feather River has prepared a draft
report which identifies TCMs considered feasible in the district.
Staff is recommending conditional approval of TCMs for Feather
River pending receipt of the final report. The plan satisfies
the requirements for all feasible measures and expeditious
adoption schedule, given the particular characteristics of the

The plan assumes a moderate classification for ozone. A moderate
classification presumes attainment of the state standard by
December 31, 1994 or, in the case of transport receptors,
abatement of the local contribution by that date. However, the
districts have not yet done an air quality analysis to determine
whether the local contribution to ozone will be fully abated by

Staff is recommending that the districts work with ARB staff in
applying a proportional rollback analysis to project the likely
date by which the local contribution to ozone violations will be


Approval of the plan will allow the districts to begin
implementing satisfactory plan elements while any plan
deficiencies are addressed. The emission reductions identified
in the plan along with other reductions not accounted for in the
plan (e.g., benefits from vehicle inspection and maintenance),
are expected to abate, or partially abate, the local contribution
to ozone violations.