Sources of Air Toxics – 1996 NATA


Air toxics are emitted from many types of sources.  These sources of air pollution are generally categorized as point, nonpoint, and mobile (on-road and non-road) source.

For the purposes of the National-scale Air Toxics Assessment (NATA), a point source is a stationary facility or process whose location could be identified with latitude and longitude coordinates. Point sources include large facilities that emit a significant amount of air pollution during manufacturing, power generation, heating, incineration, or other such activity. They also include smaller facilities including those that are required to report their emissions under the federal Toxic Release Inventory program and the state’s Community Right-To-Know program.

These are small stationary sources of air pollution which by themselves may not emit very much, but when their emissions are added together, they account for a significant portion of the total emissions of air toxics. They are also referred to as area sources and are generally too small or too numerous to be inventoried individually. The following are grouped under nonpoint sources in NATA:

  • Consumer products, including personal care products, household products, adhesives and sealants, automotive products, and coatings such as paints
  • Residential heating and fuel use
  • Pesticide use
  • Gasoline stations
  • Dry cleaners
  • Institutional and commercial heating

Mobile Sources are divided into two categories:

  • On-road mobile sources are vehicles found on roads and highways, including cars, trucks, buses, and motorcycles.
  • Non-road mobile sources include aircraft, trains, lawnmowers, boats, dirt bikes, construction vehicles, farm equipment, leaf blowers, and more.


As part of the National-Scale Air Toxics Assessment (NATA), USEPA prepared a comprehensive list of air toxics emissions for the entire country in 1996. The emissions inventory for New Jersey was briefly reviewed and revised by NJDEP before being finalized by USEPA. Although there are bound to be some errors in the details of a massive undertaking such as this, a summary of the emissions inventory can give us some indication of what may be the most important sources of air toxic emissions in our state. As can be seen from the pie chart below, Mobile sources are the largest contributors to air toxics emissions in New Jersey, with on-road mobile sources accounting for 35%, and non-road mobile sources contributing 33%. Area sources represent 25% of the inventory (USEPA refers to this category as “Area and Other” because it includes residential, commercial, and small industrial sources). Major Point sources account for the remaining 7% of the inventory. Major Point sources are defined by the Clean Air Act as facilities that emit more than 10 tons per year of a single hazardous air pollutant (HAP) or 25 tons per year of all HAPs combined.

Note that this pie chart does not include emissions of diesel particulate matter. For a discussion of diesel emissions, click here.


When the New Jersey emissions estimates are broken down by county, it is evident that the areas with the greatest air toxic emissions are generally those with the largest population. This is directly related to high levels of vehicle use, residential fuel burning, solvent use, and other population-related activities in those counties.

USEPA emphasizes that the methods used to conduct emissions inventories vary somewhat from year to year, so the results are not exactly comparable.

Concentrations of some air toxics are dominated not by local emissions, but by atmospheric transformation (or secondary formation) and by what USEPA refers to as background estimates.

Background concentrations can be attributed to long-range pollutant transport, unidentified emission sources and past emissions. A detailed description of how USEPA came up with these “background concentrations” can be found on USEPA’s NATA web site.

There are two air toxics that are of concern in New Jersey in the 2014 NATA for which the estimated statewide average background concentrations are higher than their respective health benchmarks. These pollutants are:

  • Acetaldehyde
  • Carbon tetrachloride


Atmospheric transformation, also referred to as secondary formation is a process by which air pollutants are transformed in the air into other chemicals. When a pollutant is transformed, the original chemical no longer exists, but is replaced by one or more chemicals. Compared to the original pollutant, the newer reaction products may have more, less, or the same toxicity. Transformations and removal processes affect both the fate of a pollutant and its atmospheric persistence.