What is available at this
risk map site? Top of Page
This web site contains inhalation cancer risk maps for
California for the 2001 calendar year, along with backcast 1990
calendar year maps, projected 2010 calendar year maps, and maps
representing a 75% reduction in the diesel risk from year 2000 levels.
There are also maps that focus in more detail on smaller areas of
California for these same modeled years. The finest visual resolution
available in the maps on this web site is 1 kilometer by 1 kilometer.
Therefore, individual neighborhoods, or single facilities do not show
up on these maps.
This web site also contains links to important reference documents
that explain how the modeling was performed that produced these
maps, as well as the inherent strengths and weaknesses of the
modeling.
These maps are a working draft. The linked reference documents will
help you to understand the current state of knowledge and how
ARB staff is working to improve this knowledge base. The references
documents also contain more detailed information on the caveats discussion below.
Caveats related to the risk
modeling and risk maps: Top of Page
Many emissions sources were not included in the
modeling used to generate the current set of risk maps. All of
these sources are being examined for future inclusion as the available
data are improved.
The facility data represented in the current risk maps were derived either from the CEIDARS toxics data base, or
by applying speciation profiles to organic gas and particulate
matter release data from the CEIDARS criteria pollutant facility data
base. The CEIDARS toxics data base was produced as a result of Assembly Bill 2588 ( AB2588
), commonly referred to as the "Toxic Hot Spots" bill. This work has
generated an enormous amount of toxic emissions data for facilities
throughout California. The toxics and criteria data bases were
reconciled to avoid double counting of emissions data, due to overlap
of the two data bases.
The current modeling also does not yet incorporate the human
behavior aspects of toxic risk analysis, such as
how an individual moved about within the modeled region. As the
behavioral data and the modeling methods that would allow its
incorporation become available, they may be worked into this analysis
as well.
What is risk, and how is
it represented by the maps? Top
of Page
There are risks evident in all aspects of our lives. The level
of risk varies with the activity and the environment that the
activity takes place in. The objectives of the ARB's Toxic
Air Contaminant Identification Program and Toxic
Air Contaminant Control Program are to identify
sources of toxic air contaminant health risk, prioritize them,
and try to find feasible ways to reduce the risk, while maintaining
a healthy, vibrant economy.
Toxic compounds have different effects on different individuals.
The toxicity of certain compounds may also vary in complex ways
based upon the level and duration of exposure. Other environmental
factors, such as climate, can influence both the level and impact
of exposure. In addition, other compounds that are present at
the same time, or that the individual has been previously exposed
to or could later be exposed to, may change the toxic impact
on the individual. For a more extensive discussion of compound toxicity
and the assignment of risk, visit the Toxic Air
Contaminant Identification Program web site.
These maps were produced by applying cancer inhalation risk factors
determined by peer review
to modeled toxic air contaminant concentrations.
The cancer inhalation risks are in units of cancer risk per million
people, which represents the lifetime risk that one person in
a million may contract cancer from inhalation of the toxic compound
at the modeled ambient concentration.
The values shown on these risk maps should be viewed
as a gauge of relative risk, rather than as an absolute risk determination.
These maps are very useful for determining the geographic locations
where current science indicates that the greatest amount of risk
from toxic air contaminants exists. However, the absolute risk
numbers shown on the maps should NOT be used as the basis for
determining personal risk.
Many individuals contributed to the data and methods necessary
to run and subsequently display the risk modeling:
- ARB Staff:
- Paul Allen - spatial surrogates, speciation profiles
- Vijay Bhargava - source category linkages
- Richard Bode - guidance
- Skip Campbell - geographic information system data
- John DaMassa - emissions data
- Dan Donohoue - source categorization
- Vanessa Embree - web page text editing
- Michael FitzGibbon - guidance
- Bob Fletcher - guidance
- Steve Francis - modeling, mapping, web-site design
- Dennis Goodenow - emissions inventory guidance
- Vernon Hughes - spatial surrogates, method consultation
- Larry Hunsaker - emissions projection data
- Vlad Isakov - guidance, data files
- Miki Miyashiro - web-site integration
- Linda Murchison - guidance
- Chris Nguyen - emissions inventory guidance
- Randy Pasek - guidance
- Ron Rothacker - air quality data
- Beth Schwehr - speciation profiles, risk factors, guidance
- Tony Servin - data files, consultation
- Mena Shah - offroad mobile emissions guidance
- Dale Shimp - guidance
- Maritess Sicat - onroad mobile emissions
- Cheryl Taylor - facility location data
- Bob Weller - air quality data files
- Ed Yotter - onroad motor vehicle data
- and many others
- State of California staff from many departments - data files
and consultation
- Air pollution control district staff throughout California -
data files and consultation
- United States Environmental Protection Agency (U.S.EPA) staff
and consultants - ASPEN model development, guidance, data files
- Consultants retained by the ARB and other government agencies
- data files and consultation
- and many others
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