General Plan Update - City of Inglewood

5.6 Air Quality
the City of Inglewood (Plains Exploration and Production Company) had to prepare an
HRA. 89
The ARB also has identified diesel particulate matter as a TAC. Diesel particulate matter
is generated from the burning of diesel fuel. Consequently, sources, such as truck-stops,
rail yards, loading docks or other places, where large numbers of diesel vehicles may
congregate may present a health hazard.
Lifetime cancer risk is defined as the increased chance of contracting cancer over a
70-year period as a result of exposure to a toxic substance or substances. It is the product
of the estimated daily exposure of each suspected carcinogen by its respective cancer unit
risk. The end result represents a worst-case estimate of cancer risk. ARB has produced a
series of estimated inhalation cancer risk maps based on modeled levels of outdoor
airborne toxic pollutant levels. The most recent map, generated for 2001, indicates that
cancer risk in the City of Inglewood ranges from 500 persons per million to 750 persons
per million. The largest contributor to this inhalation cancer risk is the emission from
diesel engines. This cancer risk is lower than the average cancer risk over the entire Basin
(1,400 in one million), as presented in the SCAQMD Multiple Air Toxics Exposure Study
(MATES-II).
MATES-II
The SCAQMD MATES-II study, which was published in 2000, investigated region-wide
cancer risk. In particular, this study served to quantify the current magnitude of
population exposure risk from existing sources of selected TACs. The MATES-II study
estimates the current average lifetime carcinogenic risk to be 1,400 in one million in the
Basin. Mobile sources (e.g., cars, trucks, trains, ships, aircraft, etc.) represent the greatest
contributor. According to the MATES-II study, about 70 percent of all risk is attributed
to diesel exhaust particulate emissions; about 20 percent to other toxics associated with
mobile sources (including benzene, butadiene, and formaldehyde); and about ten percent
of all risk is attributed to stationary sources (which include industries and certain other
businesses such as dry cleaners and chrome plating operations). In addition, the
differences in carcinogenic risk from one site to another within the Basin are much more
driven by the influence from mobile sources than from stationary sources. The levels of
TACs associated with mobile sources are also subject to strong seasonal variations, with
elemental carbon (a surrogate for diesel particulates), benzene, and butadiene having
seasonal peaks in the late fall and winter months, while the lowest levels of these TACs
are observed during the spring and summer months.
Stationary sources that potentially emit TACs are regulated through performance
standards and emission limitations in federal and SCAQMD regulations. Past efforts for
regulating mobile sources of toxic air contaminants have provided substantial control of
lead emissions. Diesel exhaust particulates have more recently been identified as a TAC.
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SCAQMD, Annual Report on AB 2588 Air Toxics “Hot Spots” Program, March 2005.
City of Inglewood General Plan Update Technical Background Report
5.6-13