Threat Radius vs Air Toxics Risk

The Oil and Gas Threat Map displays/characterizes potential health impacts from oil & gas air pollution in two ways:

  1. With a ½ mile Threat Radius around active oil and gas wells, compressors and processors.
  2. As a county-wide average increase in cancer and respiratory risk from oil and gas air pollution based upon the Environmental Protection Agency’s National Emissions Inventory and National Air Toxics Assessment.

There are important differences between the two.

The County-wide Risk Average

Oil & gas production in Kern County

The risk assessment is based on oil & gas air pollution reported through the National Emissions Inventory.

Because it is a county-wide risk average, in counties where oil and gas development is concentrated in one region – like Kern County in California where the vast majority of facilities are in the west – a county-level assessment may downplay the risk: for those living close by oil and gas facilities the risk may well be above that threshold.

The Threat Radius

The Threat Radius is the area within ½ mile of active oil and gas wells, compressors and processors. It indicates that those within it should be concerned; it is not a declaration that those within it will have negative health impacts. The Threat Radius does not quantify the threat posed by this pollution.

Oil & Gas Facilities Used to Calculate Threat Radius vs Average Risk

The Threat Radius is drawn around active oil & gas wells, compressor stations, and gas processing plants.

The average health risk was calculated using a broader range of facilities as defined by EPA in its National Emissions Inventory. It includes the following types of facilities:

  • Active oil and gas wells, and rig for drilling new wells,
  • Centralized production facilities (tanks batteries storing oil and water from multiple wells),
  • Compressor stations,
  • Gas processing plants,
  • Other facilities along natural gas pipelines, and
  • Natural gas distribution.

Because the average health risk includes more types of facilities than the Threat Radius, there are some counties that show increased average health risk even though they host no active facilities plotted on the map, nor are adjacent to counties that host such facilities – like Appomattox County, Virginia.