State of California
AIR RESOURCES BOARD
3400 Wilshire Blvd.
Los Angeles, CA
January 25, 1978
78-1-1 Public Hearing to Consider Adoption of an Air 1
Quality Standard for Ambient Concentrations of
78-1-2 Public Hearing to Consider Proposed Highway Cycle 128
Exhaust Emission Standards.
78-1-3 Consideration of Approval of Letter of Protest to 169
ICC Regarding Southern Pacific.
78-1-4 Other Business -
a. Executive Session - Personnel & Litigation
b. Research Proposals
ITEM NO.: 78-1-1
Public Hearing to Review and Consider Data on the Effects of
Airborne Vinyl Chloride.
The staff cannot recommend any level of exposure to vinyl
chloride, other than zero, as being safe. Accordingly, the staff
recommends that the Board specify an ambient exposure level of
vinyl chloride that, when exceeded, will present an unacceptable
high risk of harm to the community and adopt an interim air
quality standard corresponding to that exposure level.
The staff recommends that the board adopt such an interim
standard for vinyl chloride based upon the findings of medical
experts summarized in the accompanying staff report, upon the
recommendation of the State Department of Health and upon the
application of a margin of safety that reflects continuous 24-hour
exposures, the long latency period and sensitive sub-populations in the
community. The staff recommends as an interim
standard a maximum allowable level for ambient concentrations of
vinyl chloride within the range of 0.01 to 0.05 parts per
million, twenty-four hour average.
The staff recommends that the ARB measurement method be employed
rather than the NIOSH method because the sample collection and
preparation techniques employed are inherently simpler and
because the ARB sampling method has much less opportunity for
sample loss. Furthermore, the staff recommends the Board
delegate to the Executive Officer the authority to determine the
administrative responsibilities of both the ARB staff and the
local districts with regard to sample collection and chemical
analysis, for the districts where there is reason to believe
ambient vinyl chloride concentrations do or might occur, in order
to enforce the vinyl chloride standard most expeditiously and
An increasingly large data base gathered from studies of persons
who have experienced occupational and/or community exposure to
vinyl chloride, a chlorinated hydrocarbon, points to this
chemical as the causative agent for a wide range of malignancies,
including angiosacroma of the liver, a hitherto rare form of
cancer. There is, in addition, evidence that workers exposed to
vinyl chloride exhibit a substantially higher frequency of
chromosome aberrations in certain blood cells (lymphocytes); that
the wives of these workers may experience a significantly greater
frequency of miscarriages than is normal; and that women who live
in communities in the vicinity of facilities in which polyvinyl
chloride (a plastic produced from vinyl chloride) is produced may
face an increased risk of bearing children with birth defects. A
number of experimenters have demonstrated that vinyl chloride and
its metabolites induce mutations in bacteria and in mammalian
cells, underscoring the possibility that inheritable genetic
consequences may occur as a result of exposure to vinyl chloride.
Several of the studies described in this report provide estimates
of the concentrations and dosages of vinyl chloride to which
humans were exposed prior to developing cancer. For example,
liver tumors and other vinyl chloride-related effects appeared in
healthy workers repeatedly exposed to a time-weighted average
(TWA) concentration of 200 ppm over an eight-hour day.
In an earlier preliminary study, possible liver damage was
reported to have occurred among some workers with eight-hour
exposures of 50 ppm. In another study, increases in chromosome
abnormalities in blood cells were observed in workers routinely
exposed to airborne vinyl chloride at estimated levels of 20 to
30 ppm (for eight hours).
The results of inhalation tests in which experimental animals
were exposed to vinyl chloride confirm its carcinogenicity.
Three species--mice, hamsters and two strains of rats--developed
tumors of the liver and other organs when exposed to vinyl
chloride at concentrations as low as 50 ppm for several months.
Consideration of these studies and testimony from a 1974 fact-finding
hearing led to the promulgation by the Occupational
Safety and Health Administration of an occupational exposure
standard for vinyl chloride of 1.0 ppm for eight hours.
The information on exposure levels used in setting the
occupational standard was based on studies of human or animal
subjects that can be characterized as normal and healthy. These
are the only studies available for use as a guide for setting a
standard for vinyl chloride for the community at large, which may
include vulnerable subpopulation groups.
It is difficult to assess the health risks to communities located
in the vicinity of these vinyl chloride sources. Evaluation of
available information on health effects of vinyl chloride in
humans and animals is complicated by a limited data base that
includes only relatively high exposures for relatively short
periods, the typically long time delay or latency period for the
development of cancer and the fact that the concept of a
threshold exposure level is not applicable to the setting of a
standard for a chemical carcinogen such as vinyl chloride.
Previous monitoring by both EPA and ARB near a facility in the
Saugus, California area showed vinyl chloride levels well in
excess of 1 ppm for 8 hours. On a 24-hour basis, levels of at
least 0.5 ppm have occurred. However, monitoring done in Long
Beach in the vicinity of other facilities showed values (averaged
over 24 hours) ranging from the detectable limit to only 0.044
ppm (see Tables VII-8 and 9 on pages 80-81).
Several regulatory agencies, including the Air Resources Board,
have developed reliable methods for the collection and analysis
of air samples containing trace amounts of vinyl chloride. In
addition, several still more sensitive "research" methods have
been developed. The staff has examined these in some detail and
concluded that the method developed by the Board's Atmospheric
Studies Branch provides the optimum combination of sensitivity,
accuracy, precision and ease of operation required for routine
monitoring of vinyl chloride in the ambient atmosphere.
ITEM NO.: 78-1-2
Public Hearing to Consider Proposed Highway Cycle Emission
Standard for Passenger Cars, Light-Duty Trucks, and Medium-Duty
Adopt Resolution 78-4.
The LA-4 test cycle is currently used in the Federal Test
Procedure to evaluate light-duty vehicle emissions performance.
This cycle is representative of typical metropolitan driving
conditions during periods of relatively high traffic density.
Since the 1972 model year, the LA-4 has been used as the basis
for regulation of light-duty vehicle emissions. Although
emissions from vehicle operation under substantially different
conditions from those encountered during the LA-4 affect air
quality in California, it has been assumed that the emissions
reductions measured in the LA-4 are also reflected under
different operating conditions.
The staff has recently received evidence, however, which shows
that some vehicles do not exhibit adequate emission control
during the high speed driving conditions typically encountered in
California. These conditions are represented in the EPA highway
cycle, which is used to determine highway fuel economy numbers
for compliance with federal fuel economy regulations.
A comparison of highway and city NOx measurements revealed that
some manufacturers may be incorporating defeat devices into
electronic spark advance systems by programming them to exhibit
low emissions during LA-4 type conditions, and good fuel economy,
but not necessarily low emissions, during the highway cycle. The
staff has analyzed one of these potential defeat devices: the
Chrysler ESA (Electronic Spark Advance) system.
Accordingly, the staff is proposing that highway cycle NOx
emissions be limited to 1.33 times the applicable LA-4 NOx
standard. If applied to 1980 and later model vehicles, this
standard could reduce NOx emissions in SCAB by approximately 3
tons/day in 1990, assuming the same rate of defeat device use in
1980 as in 1978. Since the EPA highway cycle is already
performed on all emission data vehicles, the standard will result
in no significant expense to manufacturers. Only minimal lead
time is necessary, since no major system redesign work should be
required, but only system recalibration. However, the staff
proposes that the highway cycle NOx standard not take effect
until the 1980 model year in order to give manufacturers an
adequate safety margin for compliance.
ITEM NO.: 78-1-3
Consideration of Approval of Letter of Protest to ICC Regarding
This report will be available at the Board Meeting.