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Pacific Southwest, Region 9

Serving: Arizona, California, Hawaii, Nevada, Pacific Islands, 147 Tribes

Las Vegas (Clark County) Carbon Monoxide Pollution

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On September 16, 2010, the U.S. Environmental Protection Agency finalized the rule to redesignate Las Vegas Valley to attainment for the National Ambient Air Quality Standard (NAAQS) for Carbon Monoxide (CO) and approved the maintenance plan showing maintenance of the CO standard though 2020.

Las Vegas was designated as a CO nonattainment area in 1978. In response to this nonattainment status, Clark County and the State of Nevada adopted and implemented new air quality plans and control measures, including state and local wintertime gasoline fuel requirements. These measures helped reduce the number of exceedances of the CO standard from over 40 each year in the mid-1980s to less than 5 by the mid-1990s. The last recorded exceedances of the CO air quality standard occurred in 1998.

Carbon monoxide is a colorless, odorless, poisonous byproduct of combustion. In Clark County, like most urban areas, CO comes primarily from tailpipe emissions of cars and trucks. Exposure to elevated CO levels is associated with impairment of visual perception, work capacity, manual dexterity, and learning ability, and with illness and death for those who already suffer from cardiovascular disease, particularly angina or peripheral vascular disease.

Documents and related information

Past EPA Actions

Proposed Redesignation for Carbon Monoxide

On July 21, 2010, the U.S. Environmental Protection Agency proposed to approve the most recent carbon monoxide maintenance plan and re-designation request submitted by the state of Nevada. When finalized, the plan will bring the Las Vegas Valley into attainment status and compliance with carbon monoxide air quality standards set forth by the Clean Air Act. EPA's proposed approval was contingent upon the state's submittal of a commitment to reinstate certain state requirements for Reid Vapor Pressure (RVP) related to wintertime gasoline in Clark County. This commitment is important because the state may need to reinstate the requirements in case carbon monoxide levels increase in the future.

Documents and related information

Finding of Attainment for the Las Vegas Area for Carbon Monoxide

On May 20th, 2005, EPA made a final decision that Las Vegas, Nevada, and the surrounding area meets the federal public health air quality standards for carbon monoxide (CO). There have been no exceedances of the carbon monoxide standard since 1998. The improvement in air quality came about because of carbon monoxide control measures that have been successfully implemented in Las Vegas. These control measures include Nevada's motor vehicle inspection and maintenance program and Clark County's cleaner burning gasoline program. No comments were received from the public on the proposal, which was published on January 10th 2005. This final action was published in the Federal Register on June 1, 2005.

Documents and related information

Finalized Approval of SIP Revisions

On August 7, 2006, EPA finalized its approval of revisions to the state implementation plan (SIP) revisions submitted by the State of Nevada to provide for attainment of the carbon monoxide (CO) national ambient air quality standards (NAAQS) in the Clark County serious CO Nonattainment Area. The revised attainment plan, as modified as requested by EPA, includes revised base year and future year emissions inventories and a revised demonstration of continued attainment of the carbon monoxide national ambient air quality standard in Las Vegas Valley through 2020 based on the most recent emissions models and planning assumptions and establishes new motor vehicle emissions budgets. The intended effect of this approval action is to update the carbon monoxide motor vehicle emissions budgets in the Las Vegas area and thereby make them available for the purposes of transportation conformity.

On July 23, 2004, EPA finalized its approval of the state implementation plan (SIP) revisions submitted by the State of Nevada to provide for attainment of the carbon monoxide (CO) national ambient air quality standards (NAAQS) in the Clark County serious CO Nonattainment Area. EPA finalized approval of the Clark County serious area carbon monoxide (CO) plan because the plan demonstrates attainment of the national CO standard and meets the applicable Clean Air Act (CAA) requirements. There are presently no monitored exceedances of the CO health-based standard, which is 9 ppm averaged over 8 hours. Clark County has experienced no exceedances from 1999 to the present.

As part of this action, EPA approved control measures that are relied upon in the CO plan to demonstrate attainment of the health-based standard. EPA approved Nevada’s Inspection and Maintenance (I/M) program under section 187(a)(6) of the CAA, Clark County’s Cleaner Burning Gasoline (CBG) program under section 211(c)(4)(C) of the CAA, and Nevada’s wintertime specifications related to Reid Vapor Pressure (RVP) for gasoline sold in Clark County. These three programs are the major control measures, other than the oxygenated fuels program that we approved in a prior, separate action and the federal motor vehicle control program, that reduce CO emissions from motor vehicle sources.

EPA had proposed to approve the plan in January 2003. EPA received public comments on the proposed approval and has responded to those comments in the document below titled “Response to Comments” document.

Documents and related information

Additional documents related to the proposals

Finding of nonsubmittal and Adequacy Determination

On August 31, 1999, EPA made a formal finding that Clark County, Nevada, missed a deadline under the Clean Air Act to submit a plan showing how it will meet national air quality standards for carbon monoxide in the Las Vegas Valley. Under the Clean Air Act, states are required to submit state implementation plans (SIPs) providing for attainment of health-based air quality standards in areas such as Clark County, which is classified as serious for carbon monoxide pollution. The deadline for submittal of such a plan for Clark County was May 3, 1999. EPA's formal finding that the plan had not been submitted started an 18 month Clean Air Act sanction clock. Sanctions would have imposed more stringent permit requirements for industrial sources, and limitations on the county's federal highway funds (after 24 months).

However, EPA determined that the entire plan was complete in September 2000, which stopped these Clean Air Action sanctions from applying. EPA also determined that the motor vehicle emission budgets in the plan were adequate in November of 2000.

Related Documents

Contact Information

Karina OConnor (oconnor.karina@epa.gov)
(775) 833-1276

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