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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