Role of Regulations, Advisories, and Notifications in Improving Air Quality

Shankar B. Prasad, M.B.B.S.
Community Health Advisor
California Air Resources Board
Sacramento, California

In California, state and local entities are responsible for controlling emissions from stationary and mobile sources to meet federal and state ambient air quality standards (AAQSs) to protect human health and welfare. In an effort to protect individuals from adverse air pollution impacts, local air pollution control agencies (e.g., South Coast AQMD) routinely issue health advisories and public notifications when air pollutant levels are expected to exceed preset threshold levels for criteria pollutants and toxic air contaminants, respectively. The success of advisory and notification programs is evident from the changes in activity patterns in schools, and from reductions in toxic pollutant emissions from many facilities. Guidelines for these programs have been developed in consultation with various state (Office of Environmental Health Hazard Assessment (OEHHA) and ARB) and federal agencies, cities, schools, the public-at-large, consumer interest groups, and the regulated community.

    California is a state of great diversity and size spanning an area of about 156,000 square miles. For purposes of managing the geographically distinct air quality problems across the state, California is divided into 35-air pollution control districts, where an individual air basin may encompass administrative areas of one or more county governments. Without question, the most severe air pollution problem occurs in the South Coast Air Basin (SoCAB), which is commonly known as the Los Angeles Basin. In this regard, federal and state AAQSs for ozone, carbon monoxide (CO), and PM10 are routinely exceeded in the SoCAB. In 1997, the maximum 1-hr average ozone concentration recorded in the SoCAB was 0.205 ppm, with 144-days exceeding the state AAQS (0.09 ppm) and 64-days above the federal AAQS (0.12 ppm) (Table 1). For CO in 1997, the maximum 8-hr average concentration was 17.1 ppm, with 16 and 12-days recorded above the state (9.0 ppm) and federal (9 ppm) AAQSs, respectively. The highest 24-hr average PM10 concentration in 1997 was 224 :g/m3, with 54-days exceeding the state standard (50 :g/m3) and 6-days over the federal standard (150 :g/m3). The sizeable improvements in ambient air quality observed in the SoCAB are largely the result of an aggressive air pollution control program to reduce emissions of both criteria pollutants and toxic air contaminants from stationary and mobile sources.

In the mobile source arena, the ARB has targeted two main parameters to control emissions from motor vehicles: exhaust emission levels from on-road motor vehicles and the properties of motor fuels. From light-duty motor vehicles (e.g., cars and small trucks) without tailpipe controls (i.e., pre-1968), emissions of hydrocarbons, nitrogen oxides (NOx), and CO are 10.6, 4.1, and 84 g/mile, respectively. Over the ensuing 26-years (Table 2), improvements in emission control technologies and vehicle durability enabled the ARB to adopt “Low Emission Vehicle” standards in 1994. These standards called for low and ultra-low emission vehicles that have to be certified to meet tailpipe emission standards that were < 1% for hydrocarbons, ~4% for NOx, and 2-4% for CO of the emission levels from pre-1968 motor vehicles.

The achievement of increasingly stringent tailpipe standards could not have been achieved without improvements in motor fuels. Over the same time span, the ARB has also adopted a suite of regulations to tighten the specifications of gasoline sold for use in motor vehicles (Table 3). Since 1991, with the adoption of Phase 2 of the California Reformulated Gasoline (CaRFG) Program, stringent limits were placed on Reid Vapor Pressure (RVP), sulfur, aromatic, and olefin levels, along with the phase-out of leaded gasoline. Currently, levels of sulfur in gasoline are capped at 30 ppm by weight, RVP at 7.0 psi, and aromatics at 22.3 % by weight. The mandated reductions in fuel aromatic and olefin contents has the added benefit of reducing emissions of two major toxic air contaminants – benzene and 1-3, butadiene.

To address emissions from heavy-duty vehicles, which primarily utilize diesel, recent efforts have focused on reformulating diesel fuel and lowering emissions from trucks and buses. Of special concern is the reduction of particulate emissions, which have been designated as a toxic air contaminant by the State of California.

For stationary sources, criteria pollutant emissions from major industrial facilities largely occurred in the 1970’s. Since 1987, efforts have focused on reducing emissions of toxic air contaminants through the adoption of control measures including those to reduce benzene emissions from gasoline service stations (adopted in 1987) and perchloroethylene emissions from dry cleaners (adopted in 1993). Other measures have been adopted to limit emissions of metals (e.g., hexavalent chromium, arsenic, cadmium, and nickel), ethlene oxide, and dioxins.

To warn the general public in California about the health risks posed by criteria pollutants, local air pollution control agencies like the South Coast AQMD make regular predictions of air quality conditions and issue health advisories on a daily basis. Health advisories serve to provide the public with information on air quality conditions in different areas within an air basin. Qualitative terms such as good, moderate, or unhealthful are used to inform the public that air pollution levels have exceeded predetermined thresholds that could lead to adverse health impacts such as the impairment of lung function (resulting in a decrease in breathing capacity and exercise tolerance), excess coughing, or headache. For example, a “good” ozone day is characterized as a day in which the maximum 1-hr average ozone concentration is no greater than 0.12 ppm. At this maximum concentration, no reported adverse health effects are known to occur based on present knowledge. On “moderate” days, ozone concentrations may reach levels that are harmful to sensitive sectors of the general population like school children, the elderly, and people with heart and lung disease. When ambient levels are projected to reach concentrations that are harmful for these sectors of the population, a cautionary statement is issued to recommend changes in activity patterns at schools, such as to limit or avoid outdoor activities.

For toxic air contaminants, chronic exposures are associated with higher lifetime cancer risk, and the State of California recognizes the cancer-causing potential of a suite of airborne contaminants (e.g., diesel particulate, benzene, perchloroethylene, and 1,3-butadiene). Because emissions of toxic air contaminants from stationary sources could be higher in surrounding areas, public notifications, to inform the public living in the vicinity of major source of airborne toxics, are required by law under Assembly Bill 2588 known as the “Hot Spots” bill. The aim of the notification process is to trigger action by facility operators to inform the people living near the facilities of the risk from toxic emissions released by the facility. Whenever the risk posed by the release of air toxics exceeds a predetermined level deemed as unsafe by a local air pollution control agency, the facility must notify the public of the risk posed by the emissions release. In the SoCAB, no existing facilities are allowed to exceed a maximum individual cancer risk (MICR) of 25 in a million (i.e., 2.5 x 10-5) or a hazard index of 3.0. If they exceed this limit, emissions must be reduced in order to continue operations. The requirement for a public notification applies to all facilities with a MICR of 10 in a million (10-5), a hazard index > 1 for toxic air contaminants, or a hazard index > 0.5 for lead. Different thresholds are applicable to new facilities or sources undergoing modification.

In the last three decades, California has made tremendous progress in reducing emissions of criteria and toxic pollutants using the command-and-control approach. While the ARB’s long-term programs to reduce emissions from motor vehicles and toxic “hot spots” has played a major role in achieving the air quality improvement, the issuance of public notifications and health advisories has also been a contributing factor to improving environmental quality. By informing the public that criteria pollutant levels may reach unhealthful levels, the public-at-large has the information needed to make informed decisions as to what they can do to change their activity pattern and reduce personal exposure to those pollutant stressors. The levels at which notifications are issued is critical insofar as keeping residents living near toxic pollutant sources informed of the risk they face in their daily lives. However, because of the amount of effort required to issue public notifications and the inference that they may be “bad neighbors”, many facilities have opted to reduce their emissions below threshold values, thereby eliminating the need for issuing a public notification. In this regard, the public notification process has indirectly led to voluntary reductions in the amount of toxic pollutants emitted in California.