Baseline 2020: Air Quality


Source and Assumptions

The Utah Division of Air Quality monitors pollutants and implements regulatory policies to protect public health. When concentrations of certain pollutants are expected to exceed the maximum thresholds allowed by federal law, the Division takes actions to achieve and maintain the minimum air quality standards. As part of this process the state has the State Implementation Plan (SIP) in place. For certain pollutants the Division's planning branch conducts simulation modeling to understand the effects of weather on the development and buildup of air pollution. Air emissions are also projected for five major pollutants:

  • Carbon Monoxide (CO)
  • Nitrogen Oxides (NOx)
  • Particulate Matter (PM10)
  • Sulfur Oxides (SOx)
  • Volatile Organic Compounds (VOC)

To project emissions for these pollutants the Division does the following:

  • Conducts an emissions inventory of point sources (stationary, commercial, or industrial sources that emit more than 100 ton/yr of a monitored pollutant. Utah has approximately 300 monitored point sources); mobile sources (highway vehicles); and area sources (non-road mobile and stationary sources that are too small or numerous to be monitored individually). The annual emissions inventory quantifies the amount of pollution emitted in each county. This type of inventory provides only a very coarse representation of the spatial and temporal distribution of the pollutants.
  • Incorporates known technological advances that will be accepted in the marketplace and assist in reducing emissions. These include cleaner engines, fleet turnover, and other technologies. The Environmental Protection Agency promulgates rules for crediting reductions to a State's emissions inventory based upon demonstrated technology. Based upon these rules, and at times upon the expectation that such rules will be in place, the state is allowed to adjust future emissions projections accordingly. This is true for all emission sources, including large industrial sources and automobiles.


Characteristics and Trends

The emissions of all five major air pollutants are projected to increase from 1995 to 2020, despite general decreases in the previous 25 years. The Greater Wasatch Area has met the ozone standard since 1990 and has been redesignated as an attainment area for ozone. An "ozone maintenance plan", outlined in the SIP, is in place and will be carried out. The standards for CO and PM10 have been met since 1994. The largest percent increases are expected to be in volatile organic compounds (VOC), fine particulates (PM10), and nitrous oxides (NOx).

Major Issues and Findings

The anticipated growth in emissions in the Greater Wasatch Area introduces several major issues and findings that are relevant to the understanding of the baseline and the development of alternative scenarios. These include the following:

  • Based on the ambient air monitoring of the past seven years, the increase in PM10 may pose the most pressing problem in terms of meeting the National Ambient Air Quality Standards (NAAQS). Past monitoring data indicates that the new particulate standards (PM) will be difficult to attain at current emissions levels. Because NOx is an important contributor to PM formation, the increase in levels of both PM10 and NOx pose a significant challenge for the future.
  • NOx in combination with VOC become ozone. Salt Lake and Davis counties have been redesignated to attainment for ozone. Past monitoring data for ozone indicates that the new ozone standard may be difficult to attain depending on meteorological conditions in a given year. Automobiles are the single largest source of NOx and VOC and emissions in both are projected to grow.
  • CO is also projected to grow substantially. This problem is highly localized, with the greatest concentrations occurring in the vicinity of road intersections. However, more important than overall growth of the CO inventory is the spatial distribution of these emissions.
  • The new NAAQs are stricter and will make attainment much more difficult. Air quality is a major challenge and a possible constraint to future growth in the Greater Wasatch Area.



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