Original Date: 02/23/1998
Revision Date: 01/18/2007

Proposition 65 and the California Assembly Bill 2588 require industrial manufacturers that generate more than 25,000 pounds of toxic air emissions per year to notify the public in the immediate area that there may be a risk of exposure to known carcinogenic substances. To comply with these regulations, Northrop Grumman’s environmental engineers developed an In-House Air Toxics Modeling process to precisely determine the exact isopleth (the distribution and dispersion pattern of an airborne substance) of the toxic air emissions.

Proposition 65 and the California Assembly Bill 2588 (AB2588) require industrial manufacturers that generate toxic air emissions to notify the public in the immediate area that there may be a risk of exposure to known carcinogenic substances. To comply with these regulations, Northrop Grumman’s environmental engineers developed an In- House Air Toxics Modeling process to precisely determine the exact isopleth (the distribution and dispersion pattern of an airborne substance) of the toxic air emissions.

The modeling process consists of (1) identifying the pollutant sources and emission factors, (2) developing emissions inventories and public notification, (3) modeling, and (4) final analysis, presentation, and reporting. The modeling parameters include calculating the Maximum Individual Cancer Risk (MICR) using the following equation:

MICR = Q * (X/Q) * U * MP * MET, where Q is the emissions of pollutants in tons per year; X/Q is the dispersion factor as fn (distance from the emission source using Gaussian distribution calculations); U is the unit risk factor of toxic pollutant; MP is the multi-pathway factor of exposure (human toxicology); and MET are the meteorological factors.

A graphic model of the distribution and dispersion pattern of the toxic emissions can be generated for analysis, presentation, and compliance reporting by using standard EPA Industrial Source Complex Dispersion Models (ISC2 and ISC3); the California Air Resources Board Assessment of Chemical Exposure for AB2588; specialty software (Golden Software Surfer) developed expressly to calculate the isopleth; and sophisticated mapping software.

Northrop Grumman’s In-House Air Toxics Modeling process determines accurate models that are essential for proper regulatory compliance. In addition, these models provide operational flexibility in program planning; reduce potential mitigation and related costs; and demonstrate a good neighbor policy with substantial and positive results.

For more information see the Point of Contact for this survey.