Although no U.S. emissions requirements apply to these plants, Sempra  and Intergen required a presidential permit to construct and connect the  new transmission lines needed at the U.S.-Mexican border to export  electricity into the United States. Emissions from the Mexicali Plants Are Comparable to New Plants in California, but Offset Requirements Would Apply in Imperial County

The emissions from the Sempra and Intergen power plants in Mexicali are  comparable to emissions from similar plants recently permitted in  California and are low relative to emissions from the primary sources of  pollution in Imperial County, which are various forms of dust and motor  vehicles. However, if the plants were located in Imperial County, they  would be required, among other things, to offset their emissions by  reducing emissions from other pollution sources in the region. Emissions Generated by the Sempra and Intergen Power Plants May Contribute to Various Adverse Health Impacts in Imperial County, but the Extent of Such Impacts Is Unknown

Emissions from the Sempra and Intergen power plants may contribute to  adverse health impacts in Imperial County, but the extent of those impacts  is unknown for several reasons. DOE Did Not Analyze All the Likely Asthma-Related and Other Health Impacts of Increased Pollution from the Sempra and Intergen Power Plants

calculated that emissions from the power plants would be expected to  increase asthma hospitalizations in the county by less than one case per  year. In addition, the DOE study did not address the extent to which increased  emissions of particulate matter would cause other adverse health impacts,  such as other respiratory or cardiovascular problems. However, if the modeling is not accurate, then the health impacts  could be larger than DOE estimated. Because these data were not available, DOE used surrogate  values from Phoenix, Arizona. In addition, relevant  agreements among the United States, Canada, and Mexico may not provide  adequate mechanisms to address adverse health impacts resulting from  emissions from these plants. While this action would  have benefits to air quality and health, it would also have costs, such as  possibly reducing energy supplies available to southern California. Finally, another potential option is the development of a binational clean  air trust fund that could provide grants and loans to support projects that  would improve the air quality of U.S. and Mexican cities that share air  basins in the border region. Nevertheless, the plants emit some pollutants into an air  basin that already does not meet some air quality standards and is home to  many asthmatic children and a low-income population that may be  particularly susceptible to adverse health consequences from any level of  pollution increase. Appendix I: Objectives, Scope, and Methodology

The objectives of this report were to determine (1) how emissions from  the Sempra and Intergen power plants compare to emissions from recently  permitted plants in California and emissions from sources in Imperial  County, and what emissions standards the plants would be subject to if  they were located in Imperial County; (2) the health impacts of emissions  from the power plants on Imperial County residents; and (3) what options  exist for U.S. policymakers to ensure that emissions from these power  plants do not adversely affect the health of Imperial County residents. 3.
Why GAO Did This Study

Power plants emit pollutants that have been linked to various negative health effects. In 2003, two new power plants, owned by Sempra Energy and Intergen, began operations 3 miles south of the U.S.-Mexico border near Imperial County, California. The county does not meet some federal and state air quality standards and may be further impacted by the emissions from these plants. Although these plants export most of the electricity they produce to the United States, they are not currently required to meet any U.S. or California emissions standards. GAO was asked to determine (1) how emissions from the two plants compare with emissions from recently permitted plants in California and emissions from sources in Imperial County, and what emissions standards they would be subject to if they were located in Imperial County; (2) the health impacts of emissions from the plants on Imperial County residents; and (3) options available to U.S. policymakers to ensure that emissions from these plants do not adversely affect the health of Imperial County residents. In commenting on a draft of this report, DOE disagreed with our characterization of the limitations of their assessment of the health impact of pollution from the Sempra and Intergen power plants. We believe we have portrayed the limitations of this assessment accurately.

What GAO Found

The estimated emissions from the Sempra and Intergen power plants near Mexicali are comparable with similar plants recently permitted in California and are low relative to emissions from the primary sources of pollution in Imperial County, California, which are dust and vehicles. However, if the plants were located in Imperial County, they would be required to take steps to improve air quality by reducing emissions from other pollution sources in the region, such as paving dirt roads, because the county is not meeting certain U.S. air quality standards. Although emissions generated from the Sempra and Intergen plants may contribute to various adverse health impacts in Imperial County, the extent of such impacts is unknown. The Department of Energy (DOE) estimated that emissions from these plants may increase asthma hospitalizations by less than one per year. However, DOE did not quantify any other asthma-related impacts, such as emergency room visits or increased use of medications, which, although less severe, are likely to occur more often. In addition, DOE did not determine whether increased emissions would cause other respiratory or cardiovascular problems and the impact of particulate matter on particularly susceptible populations. Finally, the potential health impacts associated with ozone could be greater than DOE estimated because some important data needed for modeling were not available. Existing laws and international agreements may not provide adequate mechanisms to address adverse health impacts resulting from power plant emissions. Policymakers could take some actions, such as requiring plants that seek to export electricity to the United States to use specified emission controls. While this action would have benefits, it would also have costs, such as possibly reducing energy supplies available to Southern California. Long-term policy options include the development of a binational pollution reduction program or a trust fund to provide grants and loans to support air quality improvement projects. However, substantial efforts on both sides of the U.S.-Mexico border would be required to establish the legal and management framework necessary for such programs to be effective.