Air Pollution: The Border Smog Reduction Act's Impact on Ozone Levels
(Letter Report, 07/01/1999, GAO/RCED-99-212).
This report provides information on the recently enacted Border Smog
Reduction Act of 1998. GAO is required to study the potential impact of
the act, which now applies only to the San Diego metropolitan area and
amends the Clean Air Act to prohibit certain foreign-registered,
noncommercial vehicles from entering the area more than twice a month.
GAO focuses on measured ozone levels and the impact of the North
American Free Trade Agreement on ozone in the San Diego area.
--------------------------- Indexing Terms -----------------------------
REPORTNUM: RCED-99-212
TITLE: Air Pollution: The Border Smog Reduction Act's Impact on
Ozone Levels
DATE: 07/01/1999
SUBJECT: Air pollution control
Environmental policies
Environmental monitoring
Hazardous substances
Motor vehicle pollution control
Environmental law
Foreign trade agreements
Motor vehicles
IDENTIFIER: San Diego County (CA)
San Diego (CA)
Mexico
NAFTA
North American Free Trade Agreement
Los Angeles (CA)
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United States General Accounting Office GAO Report
to Congressional Committees July 1999 AIR POLLUTION The
Border Smog Reduction Act's Impact on Ozone Levels GAO/RCED-99-212
United States General Accounting Office
Resources, Community, and Washington, D.C. 20548
Economic Development Division B-282838
Letter July 1, 1999 The Honorable John H. Chafee Chairman The
Honorable Max Baucus Ranking Minority Member Committee on
Environment and Public Works United States Senate The Honorable
Thomas J. Bliley, Jr. Chairman The Honorable John D. Dingell
Ranking Minority Member Committee on Commerce House of
Representatives Ground-level ozone, a major component of smog, is
a persistent air quality problem in several areas of the country.
The recently enacted Border Smog Reduction Act of 1998 addresses
one aspect of the problem, which involves reducing ozone-causing
chemicals from certain foreign-registered vehicles.1 The act
currently applies only to the San Diego metropolitan area and
amends the Clean Air Act to prohibit certain foreign-registered,
noncommercial vehicles from entering the area more than twice a
month unless they have complied with California's inspection and
maintenance requirements.2 The act authorizes fines of up to $400
per violation, and the U.S. Customs Service and the Immigration
and Naturalization Service plan to cooperate in enforcing the act.
While the Border Smog Reduction Act addresses emissions from
certain passenger vehicles, it does not address those from
commercial vehicles, such as trucks, which are also a source of
ozone-causing chemicals. The effect of increased commercial
vehicle traffic on air quality has been of particular concern
since the North American Free Trade Agreement (NAFTA) was
implemented in January 1994. This agreement created 1P.L. 105-286
(1998). 2The act does not specifically mention San Diego or
California, but they are the only jurisdictions meeting criteria
specified in the act. Page 1
GAO/RCED-99-212 Border Smog B-282838 incentives to encourage trade
between Mexico and the United States and has been responsible, in
part, for the growing number of trucks traveling in the border
region. The Border Smog Reduction Act required us to study the
act's potential impact. As agreed with your offices, we focused
on measured ozone levels and the impact of NAFTA on ozone in the
San Diego area. Specifically, we determined (1) what estimates
were available of the act's potential impact on ozone-causing
chemicals in the San Diego area and (2) trends in commercial
border traffic and ozone levels in the San Diego area before and
after NAFTA was implemented. Results in Brief The California
Air Resources Board, a state agency that regulates air quality,
estimated that the Border Smog Reduction Act would reduce ozone-
causing chemicals in San Diego County by less than 0.5 percent
annually. This calculation was based on an estimated number of
foreign- registered vehicles that would be subject to the act's
provisions. The act's impact is difficult to estimate because
data are not available on the number and condition of foreign-
registered vehicles entering the United States and a variety of
factors influence measured ozone levels. The trend in commercial
truck crossings into the United States from Mexico was generally
upward both before and after NAFTA was implemented in January
1994. At the same time, the trend in measured ozone levels in the
San Diego area was generally downward. Several factors
contributed to the decrease in ozone levels, including efforts by
San Diego County and California state officials to tighten the
standards for passenger vehicle emissions and to encourage the use
of cleaner formulations of gasoline. Because a number of factors
affect measured ozone levels, it is difficult to isolate the
impact of a single factor, such as commercial truck traffic.
Background Ozone results from a reaction between two
groups of chemicals, nitrogen oxides and volatile organic
compounds, in the presence of sunlight and warm temperatures.
Often, when strong winds are present, ozone may travel hundreds of
miles from its source. As a result, a region that may have
relatively low levels of ozone-causing chemicals may nonetheless
experience high levels of ozone. Motor vehicle exhaust is a
significant source of ozone-causing chemicals. Other common
sources include Page 2
GAO/RCED-99-212 Border Smog B-282838 chemical solvents from dry
cleaners and fossil fuel combustion from industrial facilities.
Ozone, a major component of smog, is a strong irritant that can
cause restriction of the airways, forcing the respiratory system
to work harder to provide oxygen to the body. Clinical studies
show that chronic exposure to smog reduces lung capacity, lowers
stamina, and leaves people vulnerable to long-term respiratory
problems. The Clean Air Act establishes standards for atmospheric
ozone that many areas within the United States currently fail to
meet. The act requires states to develop plans to reduce ozone
levels in these areas. Such plans must establish, among other
things, vehicle inspection and maintenance programs to monitor and
enforce emission limits. In 1993, California passed a law
requiring certain vehicles registered outside the state, including
those registered in Mexico, to comply with its inspection and
maintenance requirements.3 Although Mexico has emission standards
for several pollutants, including ozone-causing chemicals, the
enforcement of these standards is often weak, according to
Mexico's Director of Air Quality for the National Institute of
Ecology and an air quality expert with the San Diego Air Pollution
Control District. California found the enforcement of its law
difficult for vehicles entering from Mexico because monitoring the
border area is a federal responsibility. The Border Smog
Reduction Act makes vehicles violating this California law subject
to federal enforcement. The Border Smog Reduction Act became
effective on April 27, 1999. On that date, the U.S. Customs
Service and the Immigration and Naturalization Service began a 60-
day effort to inform targeted members of the public- specifically,
commuting workers and students-of the act's requirements. During
this trial period, inspectors with those agencies provided verbal
warnings to drivers who did not have documentation showing that
they were in compliance with the act. After this 60-day period,
officials planned to enforce the act at random intervals. Verbal
warnings would continue for drivers who were not in compliance and
were crossing the border for the first or second time in a
calendar month. Drivers not in compliance and attempting to cross
the border a third time in a calendar month would be referred to
local law enforcement authorities or returned to Mexico if local
officials were not available. 3Cal. Health and Safety Code, secs.
44011, 44011.1. Page 3
GAO/RCED-99-212 Border Smog B-282838 In addition to passenger
vehicles, commercial traffic is a major contributor to ozone-
causing chemicals in the San Diego area. NAFTA, which went into
effect on January 1, 1994, was intended to facilitate trade and
investment throughout North America. Since the implementation of
NAFTA, cross- border trade has increased. Imports from Mexico
grew by 86 percent from 1993 through 1996, while imports from all
other sources grew by 33 percent, raising Mexico's share of total
U.S. imports by 2.4 percent, to 9.3 percent in 1996. This
increase has meant that more trucks are traveling in the border
regions and has raised concerns about the impact of increased
truck traffic on air quality. Act's Estimated Impact The
California Air Resources Board, the state's air quality authority,
on Ozone Levels estimated that the Border Smog
Reduction Act would decrease the emission of ozone-causing
chemicals by less than 0.5 percent annually. The agency based its
calculation on the number of vehicles subject to the provisions of
the act-foreign-registered cars entering the county more than
twice a month-estimated at 7,000 each day. This number is equal
to 0.37 percent of the 1.9 million cars and light-duty trucks
registered in San Diego County. However, according to U.S.
Customs Service officials, data on the actual number of vehicles
affected by the act and the condition of these vehicles-including
their age and how much pollution they produce-are not available.
California air quality experts who have reviewed the act said they
believed its impact on air quality, including measured ozone
levels, would be relatively minor. An Environmental Protection
Agency (EPA) air quality expert we interviewed said that whether
there will be a decrease in measured ozone levels corresponding to
the decrease in ozone-causing chemicals is unclear. Several
additional factors affect the formation of ozone, such as
chemicals from other sources and weather conditions. A San Diego
air quality official, however, said that in order to reduce
overall emissions of ozone-causing chemicals in the county, it is
necessary to address even seemingly minor emitters, such as the
population of foreign- registered vehicles affected by this act.
Additionally, some U.S. Customs Service agents working at one San
Diego County port of entry said they believed any improvement in
air quality brought about by the act would be beneficial.
Thousands of vehicles cross this border area into the United
States daily and, according to U.S. Customs officials, must often
wait in line for at least 20 minutes. This number of vehicles
idling in one location produces concentrated pollution that
creates a health concern among those working at the border. Page 4
GAO/RCED-99-212 Border Smog B-282838 The state of California and
San Diego County routinely monitor air quality and emissions, but
a San Diego air quality official told us there are currently no
formal studies planned to monitor the effects of the act.
Officials with these agencies said that showing a causal
relationship between the act and any decrease in measured ozone
levels would be difficult because of the many factors that
contribute to the formation of ozone. Upward Trends in
During the past decade, there has been a general upward trend in
the Commercial Traffic number of northbound commercial truck
crossings at ports of entry in the San Diego area. Contributing
to this increased traffic is the higher volume From Mexico and
of cross-border trade encouraged by NAFTA, according to a Federal
Downward Trends in Highway Administration official
specializing in the impact of NAFTA. Measured Ozone
Although the San Diego County Air Pollution Control District
considers truck traffic a major contributor to ozone-causing
chemicals, measured Levels ozone levels in the San
Diego area have generally declined. However, California air
quality experts told us it is difficult to establish a causal
relationship between ozone levels and increased truck traffic
because the presence of ozone in the area is influenced by several
factors, and fluctuations may or may not occur as a result of
changes in truck traffic. As shown in figure 1, traffic counts at
the three San Diego County border crossing points for commercial
trucks4 increased from 1992 to 1997. Crossings rose from 429,000
in 1992 to 635,000 in 1997, an increase of 48 percent. Although
the upward trend began in 1992, commercial truck traffic increased
at a higher rate after January 1994, the date NAFTA took effect.
An official with the Federal Highway Administration told us this
increase was due, in part, to the trade agreement, which, through
reduced tariffs and other provisions, created incentives for
greater cross-border trade. A San Diego County official told us
that other factors, such as fluctuations in the Mexican economy,
might have affected trade as well. 4The ports of entry in San
Diego County that currently process commercial traffic are Otay
Mesa and Tecate. San Ysidro stopped processing commercial traffic
in 1992. Page 5
GAO/RCED-99-212 Border Smog B-282838 Figure 1: Northbound
Commercial Truck Crossings at San Diego County Ports of Entry,
1989-97 700 Number of crossings (thousands) 600 500 400 300 200
100 0 1989 1990 1991 1992 1993 1994 1995
1996 1997 Year Note: Truck crossing data were not available for
November 1995 at Otay Mesa. Thus, we estimated the number of
crossings by using a simple average of the preceding and following
months. Source: GAO's analysis of the U.S. Customs Service's
data. Concerns have been raised that greater volumes of trade may
exacerbate environmental problems along the border, including air
pollution. Air quality experts we interviewed said they believed
that imposing stricter regulations on emissions from commercial
trucks would be more effective in reducing ozone levels than
targeting passenger vehicles. According to a San Diego air
quality expert, commercial trucks have higher emissions per
vehicle than cars for one type of ozone-causing chemical.
Currently, commercial trucks traveling in California are not
subject to routine emission inspections but may participate in
voluntary self-inspections. An EPA official in Region IX (San
Francisco), however, stated that there is a difference between
emissions from gasoline- and diesel-powered trucks and that the
issue of testing and requiring repairs should be further studied
to determine the impact on ozone-causing chemicals. While the
number of commercial trucks entering San Diego County from Mexico
in the past decade has been generally increasing, measured ozone
levels in San Diego County have been on a downward trend. Ozone
Page 6
GAO/RCED-99-212 Border Smog B-282838 decreased by 27 percent from
1990 through 1994 and remained stable from 1995 through 1997 (see
fig. 2).5 San Diego County and California state air quality
officials said that the decrease in ozone and ozone-causing
chemicals was due, in part, to their efforts to implement
pollution controls, including emission standards for automobiles
and cleaner formulations of gasoline. Figure 2: Ozone Levels for
San Diego County, 1989-97 0.12 Ozone, parts per million 0.10 0.08
0.06 0.04 0.02 0 1990 1991 1992 1993
1994 1995 1996 1997 Year Note: Measurements
given are for the fourth-highest daily maximum 8-hour
concentration of ozone, averaged over a 3-year period. Thus, the
number for 1997, for example, reflects air quality for the years
1995 through 1997. Source: GAO's analysis of EPA's data. Although
ozone-causing chemicals-emitted by cars and trucks, among other
sources-are necessary for the production of ozone, the increased
production of these chemicals does not necessarily result in
higher ozone levels in the same area, according to EPA. Several
other conditions affect the level of ozone measured in a given
area. For instance, ozone levels in the greater Los Angeles area
affect the amount of ozone present in San Diego because the
prevailing winds, which blow from northwest to 5The measurement
used to calculate this change was the fourth-highest daily maximum
8-hour concentration. Page 7
GAO/RCED-99-212 Border Smog B-282838 southeast, transport ozone
from Los Angeles to San Diego, according to California officials.
A California Air Resources Board official told us that
improvements in recent years in San Diego's air quality correlate
with improvements in the Los Angeles area. Additionally,
fluctuations in measured ozone levels may be a result of other
weather conditions. For ozone to form, ozone-causing chemicals
must be exposed to sunlight and heat. As a result, ozone levels
are generally higher in summer months than in winter months.
Likewise, a San Diego air quality expert told us that during a
particularly cloudy or cool year, ozone levels may decrease
regardless of whether the production of ozone-causing chemicals
has increased. Agency Comments We provided the U.S.
Environmental Protection Agency and the U.S. Customs Service with
a draft of this report for review and comment. In commenting for
the EPA, officials in the agency's Office of Air and Region IX
(San Francisco) said that the agency generally agreed with the
report but would find more information on how the ozone reduction
estimate was calculated helpful. We were not provided with a
complete description of the California Air Resources Board's
estimate and therefore did not add this information to the report.
The officials also noted that emissions from different types of
commercial vehicles need to be tested differently. We added this
information to the report. The Director of the U.S. Customs
Service's Office of Planning generally agreed with the information
in the report and made technical suggestions, which we
incorporated into the report. Scope and To determine the
estimates that were available on the potential impact of
Methodology the Border Smog Reduction Act of 1998, we
interviewed officials with the California Air Resources Board, the
San Diego Air Pollution Control District, San Diego State
University, the U.S. Customs Service, and the U.S. EPA. We
reviewed the estimate prepared by the California Air Resources
Board on the potential impact of the act and gathered information
on the planned implementation of the act, including attending a
planning session on the act's implementation. The data used in
the California Air Resources Board's estimate were not
independently verified for accuracy. To determine the changes in
the volume of traffic from Mexico through San Diego border
crossings before and after the implementation of NAFTA, we Page 8
GAO/RCED-99-212 Border Smog B-282838 obtained data on commercial
truck crossings from the U.S. Customs Service for the period from
1989 through 1997. We analyzed these data to identify the trends
in commercial traffic. To determine the changes in measured ozone
levels in the San Diego area before and after the implementation
of NAFTA, we obtained information on the formation of ozone and
the factors that influence ozone levels in the San Diego area. We
also obtained ozone data from EPA for the San Diego area and
analyzed these data to identify trends for the period from 1989
through 1997. We did not independently verify the traffic or
ozone data for accuracy. We performed our work from March 1999
through June 1999 in accordance with generally accepted government
auditing standards. We are sending copies of this report to the
Honorable Carol Browner, Administrator, the Environmental
Protection Agency; the Honorable Raymond Kelly, Commissioner, U.S.
Customs Service; and other interested parties. We will make
copies available to others on request. If you have any questions
about this report, please contact me at (202) 512-6111 or John
Wanska at (312) 220-7628. Key contributors to this assignment
were Heather J. Halliwell, Richard P. Johnson, Rosemary Torres
Lerma, and D. Alan Rogers. David G. Wood Associate Director,
Environmental Protection Issues (160472) Letter Page 9
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