Science and policy are tied together when developing legislation for air quality. Key components of the science include emissions inventories, atmospheric chemistry and meteorology. These areas are integrated into complex mathematical models that are used to replicate air quality in the past to demonstrate the model's accuracy, and predict air quality in the future. The predictions are based on carefully chosen reductions in the emissions inventories. The emissions inventory reductions are used to create science based policy.
Recent research has begun to show a link between vehicle emissions and human health in proximity to highways and busy roads. The two lines of evidence come from (a) careful epidemiology combined with spatial mapping, revealing a direct link between respiratory disease, proximity to roadways, and exposure time; and (b) emerging evidence showing that ultrafine particles common in diesel exhaust are capable of crossing the blood-brain barrier, with implications for development of cancers.
In addition, concern is rising over the human health impacts associated with hazardous air pollutants from local incineration and from industry, especially high production volume chemicals. Among the most visible endpoints of concern is endocrine disruption, particularly associated with burdens of chlorinated organics in the human body. Other issues, such as mercury pollution from power plants, are also surfacing.
In January 2005, a series of articles in the Houston Chronicle called attention to very high concentrations of air toxics in Houston Ship Channel neighborhoods such as Milby Park. This resulted in heightened public awareness of the air toxics issue and subsequent demands that TERC address the issue more seriously in addition to funding ozone research. TERC has responded to this demand by drafting an Air Toxics Research Agenda, which is attached to this proposal as Appendix IV.
In the coming years, more resources may have to be spent on quantifying human health impacts of air toxics. TERC will concentrate on funding human exposure research, in coordination with medical institutions that study health effects. TERC will coordinate its efforts with those of the medical community, resulting in greater efficiency in meeting the needs of the general population.
In Texas the pollutant that receives the most attention is ozone. Ozone is a molecule composed of the oxygen atoms and is formed when nitrogen oxides (NOx) mix with volatile organic compounds (VOCs) in sunlight. NOx comes from many different sources, frequently whenever something is burning, whether it be the fuel in your car or the fuel in a large furnace at a power plant or refinery. Similarly, VOCs come from many different sources including vehicles, petrochemical plants and vegetation. There is not a simple equation that describes the exact formation of ozone, but rather there are numerous chemical reactions and chemical pathways that form pollutants in the atmosphere.
Exhaustive work has been done to develop models that represent the reaction mechanisms of pollutant precursors under a variety of conditions. These models use emission rates and chemistry to identify the type and concentration of pollutants that can be expected to form in the atmosphere. Information about emission rates of pollutants combined with the meteorology determines their spatial and temporal distribution.
An emissions inventory is an estimate of the spatial and temporal magnitude of emissions of various pollutants from sources in a region. Emissions inventories are typically divided into categories of point sources (e.g. industrial), on-road mobile (e.g. cars, trucks), non-road mobile (e.g. cranes, forklifts), area (e.g. commercial/residential fuel usage, dry cleaning) and biogenic (e.g. trees, swamps). A good emissions inventory provides input for air quality models that can reliably predict air quality. Accurate emissions inventories are the key to developing emission source-air quality relationships and cost effective control strategies for reducing pollution. Emissions inventories are frequently identified as the largest source of error in the modeling process.
The relationship between emissions inventories, chemical reaction mechanisms and meteorological conditions is intricate and involves very complicated algorithms to track the spatial and temporal formation of pollutants. Complicated software modeling techniques are used to integrate the various components that create pollution. The modeling process operates by measuring extensive data in a pre-selected timeframe and evaluating if the model can correctly predict what was measured. When the model meets the accuracy requirements for representing the past, it can then be used to predict the future. This is achieved by reducing the emissions inventories by a specified amount and determining if the reduction can create the desired reduction in pollution. When the appropriate level of emission control strategies is identified it is implemented into policy. Meteorological conditions including humidity, wind velocity, wind direction, the amount of sunlight, temperature and even soil moisture all impact the travel, mixing and chemical reactions of emissions that form pollutants. Consideration must also be given to the conditions at various heights because the meteorology at ground level is very different from the meteorology at different altitudes. Because meteorological conditions change frequently throughout the day, complex modeling must be done to keep track of the changing conditions and their impact on the temporal and spatial location of pollutants.
The New Technology Research and Development Program (NTRD) was established by the Texas Legislature in 2001 with the passage of Senate Bill 5, which also established the Texas Emission Reduction Plan (TERP). The NTRD program was administered by the University of Texas from September 1, 2001 - August 31, 2003. The Texas Commission on Environmental Quality (TCEQ) began to administer this program on September 1, 2003, which will continue through August 31, 2005. TERC assumes responsibility for the NTRD program on September 1, 2005.
The fundamental purpose of the NTRD program is to facilitate the development, certification and verification of new technologies so that they may be broadly and economically used to support clean air attainment efforts.
Reducing NOx and particulates from diesel fueled vehicles and equipment is the primary reason the Legislature established the TERP. New technologies are certified or verified by the Environmental Protection Agency (EPA) or the California Air Resources Board (CARB). In order to be successful in administering the NTRD program, TERC must facilitate the following critical actions items in cooperation with the TCEQ, the EPA, CARB and technology manufacturers:
- Identify the sources of emissions in Texas that must be targeted for new technologies because of federal pre-emption requirements and eight-hour ozone attainment mandates;
- Identification, testing and evaluation of the new and emerging technologies which are capable of reducing emissions in a cost effective manner from the targeted sources;
- Collaboration with the EPA and CARB on the actions TERC should take to facilitate the certification or verification of the needed new technologies;
- Development and implementation of TERC funded technology projects on the basis of input received from the EPA, CARB and equipment manufacturers; and
- Broad-based distribution of information regarding new and emerging technologies.
For historical information about the NTRD program see the Texas Commission on Environmental Quality's website at: http://www.tnrcc.state.tx.us/oprd/sips/research.html
Good policy is based on the best science that is available. In order to reduce pollution legislation should include specific control strategies that address the emission sources that the most significant impact. In order to identify the best control strategies detailed scientific studies are carried out using complex air quality modeling, analytical chemistry and meteorology monitoring techniques, and a variety of programs used to tabulate emissions from various pollution sources. Millions of dollars are spent each year improving emissions inventories, chemical reaction mechanisms, monitoring techniques, meteorology descriptions and the air quality models that are used to generate the formation of pollutants. The investment that is made is invaluable because it ultimately enables policymakers to identify the most economical ways of developing control strategies that reduce pollution and protect human health.