Human activities emit large number of different chemicals into the air. Due to their large concentrations and close location to people, the most dangerous air pollutants to human’s health and environment are: ground-level ozone, ground-level ozone precursors (volatile organic compounds (VOCs) and nitrogen oxides (NOx)), particulate matter (PM2.5 and PM10), sulfur dioxide (SO2), carbon monoxide (CO), and lead.


Concentrations of ground-level ozone, its precursors (VOCs and NOx), PM2.5, and sulfur dioxide in Madison County have been barely meeting acceptable levels. We will explain their sources in Madison County and what actions can help reduce them.


  • Difficulty or shortness of breathing
  • Coughing or scratchy throat
  • Increased frequency of asthma attacks
  • Making lungs for susceptible to infection
  • Worsening of other lung diseases
  • Irregular heartbeat
  • Nonfatal heart attacks
  • Premature death
  • As a result of the health problems above, there is an increase of school absences, medication use, visits to doctors and emergency rooms, and hospital admissions.


In order to decrease air pollution, we should take two steps:

  1. Look at sources of air pollution
  2. Act to reduce it


Nitrogen Oxides (ground-level ozone precursor). In 2011 Madison County, 80 % of nitrogen oxides were emitted by motor vehicles, 15 % by industrial, commercial and fuel combustion activities, and the rest by miscellaneous activities like using lawn care equipment and vehicle refueling.


Volatile Organic Compounds (ground-level ozone precursor). In Madison County in 2011, about half of VOCs are emitted by area polluters (vehicle refueling, solvent usage, etc.), 33 % by motor vehicles, 16 % by industrial and commercial processes, and 9 % by non-road outdoor equipment.


Ground-level Ozone. Ground-level ozone, or “bad” ozone, that is concentrated close to the ground (not to be confused with the ozone located in the upper atmosphere)  is not emitted by any source directly but is created by chemical reactions between nitrogen oxides and Volatile Organic Compounds (VOCs) in the presence of sunlight and heat. Thus, most ozone is created during the day and during the warm and hot months (April through October). Urban environments on hot sunny summer days are very likely to reach unhealthy levels of ozone. Wind also carries ground-level ozone, so some communities can get ozone from other places.


Motor vehicles and gas-powered equipment are the primary sources for NOx and VOC pollution. This is why reducing number of cars on the roads, fueling your car or mowing your lawn late in the evening is important to reducing potential of ozone creation.


Unhealthy concentrations of ground-level ozone poses a threat to people’s health, especially for vulnerable groups like children, pregnant women, elderly and people with respiratory diseases. In the past, Madison County has been in containment with the air quality standards of the EPA. However, after extensive research on the negative health effects of ozone, a new national ozone standard between 0.065-0.070 ppm will be introduced by the end of 2015 meaning that Madison County will become a non-containment area.


Particulate Matter. Particulate matter, or particle pollution, is a mixture of solid particles, chemicals (sulfates, nitrates, and other) and liquid droplets in the air. Usually, they are reported as two types: PM10 and PM2.5. Numbers refer to the size of the particles. The solid particles are small and invisible to the human eye, but some are big enough to see. These particles in Madison County come mostly from agriculture, dust, followed by cars, trucks, industrial and commercial facilities. In urban environments, PM pollution comes mostly from human activities like driving motor vehicles.


Sulfur Dioxide. 85 % of sulfur dioxide in East Central Indiana comes from power plants (52 %) and industrial facilities (33 %). While power plants are usually located far from human residencies, the wind can carry their pollution.



Looking at the sources of pollution, one can see that reducing motor vehicles, gasoline-powered equipment and electricity use can reduce air pollution. Other reductions should happen within the industry sector.