CHAPIS Emissions Maps

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More About the Data

Mobile, Stationary, and Area-wide Sources

The information displayed in CHAPIS comes from three major areas: mobile sources, stationary sources, and area-wide sources.

The mobile sources include information on cars and trucks (on-road mobile) as well as other mobile sources, like off-road equipment, construction equipment, ships, trains, and airports. The information for cars and trucks is compiled by the Air Resources Board (ARB) using information from ARB testing and research, the Department of Motor Vehicles (DMV), the California Councils Of Government (COGs), and Caltrans. Various models, including EMFAC2002 and Travel Demand Models, are used to estimate emissions annually of cars and trucks. County-total estimates are spatially allocated to smaller grid cells using the Direct Travel Impact Model (DTIM). For other (off-road) mobile sources, the ARB's OFFROAD model is used to estimate emissions. County-totals are spatially allocated to smaller grid cells using spatial surrogate distributions, such as light commercial zoning.

The stationary sources include information on businesses and manufacturing facilities and is compiled by each local air district. These sources are shown as black triangles in CHAPIS, and are also included as one of the source types in the Gridded Emission combinations. Larger industrial or commercial facilities can be viewed separately from the small commercial facilities (which include county-wide, aggregated estimates for facilities like gas stations and dry cleaners) in the Gridded Emissions checklists.

The area-wide sources include consumer products, paints, and other products containing solvents. These sources are estimated annually by the Air Resources Board and/or the local air districts. County-totals are spatially distributed using surrogate distributions (such as population for consumer products).

To view the information on mobile sources and area-wide sources, use the "Gridded Emissions" button in CHAPIS. The totals from all source types can be combined, or they can be turned on and off separately, for example to view just the contribution of cars and trucks (on-road mobile sources) to the emissions in each grid cell.

More Information on Stationary Sources
For stationary sources (industrial and commercial facilities), two broad types of pollutants are inventoried in California. The first type includes the traditional, smog-forming pollutants (called "criteria pollutants"), and includes reactive organic gases (ROG), nitrogen oxides (NOx), sulfur oxides (SOx), particulate matter (PM10), and carbon monoxide (CO). These emissions are estimated annually by the local air districts for major stationary-source facilities in their area. Currently, CHAPIS includes criteria pollutant data for facilities that emit 10 or more tons per year of any criteria pollutants. The second type of pollutant includes the toxic air pollutants, that can cause or contribute to adverse health effects, such as cancer, chronic organ damage, or reproductive harm. Most of the stationary source toxics information in CHAPIS is collected under a state law for the Air Toxics "Hot Spots" program, enacted in 1987. The "Hot Spots" program is intended to identify facilities whose toxic air pollution emissions may pose local impacts. The "Hot Spots" legislation requires facilities (stationary sources) to report to their local air district information about the toxic air pollution released from routine operations of the facility. Currently, CHAPIS includes toxics data for petroleum refineries, power plants over 50 megawatts, as well as metal fabrication facilities, aerospace/electronics manufacturing facilities, and chemical plants that conducted risk assessments under the "'Hot Spots" program. There will be on-going additions to the toxics data in the future.

After receiving the air toxics inventory information, the local air district prioritizes the facility into "low", "medium", or "high" priority, and the highest priority facilities must conduct a health risk assessment. The prioritization scores themselves are not an accurate measurement of risk; rather, they are used to determine whether a facility must conduct a more refined risk assessment. This risk assessment is then reviewed by the State of California Office of Environmental Health Hazard Assessment (OEHHA), and approved by the local air district. If the risk from that facility is significant, the operator of that facility must notify the public of the risk posed by that facility. For example, the facility may place ads in local newspapers, or conduct a community meeting to discuss the risks posed by that facility. If the risk exceeds a risk threshold, that facility is also required to reduce those risks below a level of significance set by each local air district. This notification requirement has proven effective in voluntary reductions of thousands of pounds of toxic emissions from facilities throughout the state.

Every four years, facilities are required to submit an update of their emissions (an emission inventory) to the local air district. Often the facility has not changed their business significantly in the past four years and simply states that there is "no change". Please contact the local air district for the most recent emission and risk data. For a detailed discussion of the "Hot Spots" program, please click here. Use the district links at the bottom to read more about your local air district's toxics program and/or link to the local air district's "Hot Spots" annual report.

To date, CHAPIS includes the following stationary source (facility) information:
1. Criteria pollutant emissions, from facilities that emit 10 or more tons per year of reactive organic gases (ROG), nitrogen oxides (NOx), sulfur oxides (SOx), carbon monoxide (CO), or particulate matter of 10 microns or less (PM10).
2. Toxic pollutant emissions from Power Plants (50 megawatts or greater) and Refineries.
3. Toxic pollutant emissions from facilities that conducted health risk assessments under California's Air Toxics "Hot Spots" program in the categories of chemical manufacturing, metal fabrication, and aerospace/electronics manufacturing.

CHAPIS uses the facility data reported in ARB's CEIDARS database for the year 2001. The latest snapshot of CEIDARS for CHAPIS was May 19, 2004.

The initial release includes facilities emitting the bulk of the criteria pollutant (smog-forming) emissions and many of the larger or important sources of toxic air pollutants. However, overall at this time, there is a much lower number of facilities with toxic air pollutant information in CHAPIS than for criteria pollutants. It is a major objective of CHAPIS to include all of the largest air pollution sources and those with the highest documented air pollution risk. CHAPIS will be updated on a periodic basis and additional facilities will be added to CHAPIS as more data become available.

Future Additions:
We are continuing to collaborate with the local air districts through the California Air Pollution Control Officers Association (CAPCOA) regarding the on-going inclusion of additional toxics emission facilities. In a few months we anticipate adding information for the following types of facilities:

(a) Other facilities with "Hot Spots" risk assessments
(b) Gas stations
(c) Plating industry
(d) Dry cleaners


Community Health | Emission Inventory

This page last reviewed May 13, 2008