Memorandum
U.S. Department of Transportation Federal Highway Administration

This is to follow-up on my previous memorandum of February 4, 2002. In that memorandum, we conveyed our conclusions that a Supplemental Environmental Impact Statement (EIS) was not warranted and that the Final EIS remained valid. We also promised to conduct short-term and long-term research on the subject. While longer term research is ongoing, the short-term research has been completed. It confirms that many of our concerns explained in the February 4 memorandum are valid and reaffirms our conclusion that a Supplemental EIS on the US 95 project is not warranted.

Background

The Federal Highway Administration (FHWA) commissioned a study in May 2002 to further explain recent research in the transportation-air toxics field and to assess the transferability or applicability of this research to the proposed US 95 project in Las Vegas. Responding to the growing need for better understanding of the issues surrounding air toxics, the FHWA engaged in this research to maintain our compliance with the National Environmental Policy Act (NEPA) and to reach a satisfactory conclusion of the legal issues surrounding the project.

We are confident that the independent research we commissioned will carry forth the most accurate assessment of air toxics issues and transportation activities available in this evolving field. This memorandum provides the primary conclusions of the study and also serves to transmit the final document.

Recent Research-MATES-II & US 95

A recent piece of research on mobile source air toxics (MSATs) is the second installment of the California-based effort Multiple Air Toxics Emissions Study or MATES-II. The FHWA commissioned Sonoma Technology, Inc. to provide an explanation of the MATES-II work, its research design, and its conclusions. More importantly, the agency was interested in the suitability of transferring the results of the MATES-II study to environmental assessments elsewhere, most notably to the ongoing debate over the US 95 project in Las Vegas.

For a number of reasons, the research team concluded that the results of MATES-II are not transferable to the US 95 case. Foremost, there is no air toxics inventory for Las Vegas-no basis from which to compare emissions impacts, vis-à-vis travel changes, projected as a result of the project. Similarly, there is no formal monitoring network from which to even begin gathering data for an inventory. In addition, the researchers concluded that vehicle fleets were considerably different between Las Vegas and the Southern California focus area of MATES-II. Weather and topography also differ considerably between the two areas. Other assessments of MATES-II and its applicability to the US 95 project failed to discuss these very significant obstacles to transferability.

The analytical approach to MATES-II also failed to address the issues of localized, project level analysis dominating the debate over US 95. The California study was spatially organized around two-kilometer grid squares with average emission projections established for each of these relatively large areas. Project-level or "hot-spot" analysis traditionally involves emissions concentrations generated by nearby sources, sometimes measured in mere meters not kilometers.

The research team also commented on the available research that addresses these MSAT issues, especially work in exposure and risk factor analysis, cancer incidence, and the development of unit risk factors for individual air toxics. Although by no means an exhaustive review of available literature, the Sonoma Technology team found that the body of evidence is not conclusive as to the correlation between road proximity and health risk. The pool of available research is not at all consistent on the existence of this linkage.

One of the key conclusions drawn from the MATES-II work and from the California Air Resources Board, statewide, is the excess cancer risk associated with diesel particulate matter (DPM). The California research pointed to a 70 percent excess cancer risk attributed to DPM alone-89 percent for all mobile source air toxics, collectively.

Despite these high numbers, it should be stressed that there is great uncertainty surrounding the establishment of risk factors. The factor employed in MATES-II for DPM is unique to California. The Environmental Protection Agency (EPA) has not developed a risk factor for DPM claiming instead that the data for human exposure are too uncertain to generate such a benchmark. In addition, the treatment of human exposure to air toxics is considerably different than for other pollutants the transportation community has traditionally assessed or mitigated. Standards for ozone, carbon monoxide, and a number of other pollutants are based on exposures measured usually in hours. Risk factors-not standards-for air toxics are measured against lifetime exposures, or 70 years, for these relevant projections.

For regional air toxic levels, the MATES-II research findings provided a positive assessment and outlook for the future. Between 1990 and 1997, cancer rates associated with air toxics decreased by about 50 percent. In addition, as EPA's Tier II and heavy-duty vehicle emission standards along with low-sulfur fuel standards go into effect, air toxics are projected to drop even further-more than 95 percent in diesel PM by 2020.

Further Environmental Assessment

The Council on Environmental Quality (CEQ) established very clear provisions for treating incomplete or unavailable information, such as the state of knowledge regarding the environmental health effects of air toxics. Section 1502.22 of the CEQ regulation acknowledges that there will be times when the agency cannot fully evaluate or disclose environmental impacts because it is lacking complete or available information supported by credible scientific evidence. The research FHWA has commissioned to address MATES-II and the US 95 project deals in large part with these uncertainties. The agency contracted with Sonoma Technology to address information considered unknown and to describe some degree of relevance to any reasonably foreseeable adverse impacts associated with the project. We are confident that the completed research falls within the provisions of Section 1502.22(b) of the CEQ regulations. Sonoma Technology's study provides ample discussion of the incomplete, developing nature of MSAT exposure and risk relationships, the relevance of such unavailable information, and the data that are available and can be used to generally assess these MSAT issues.

For the reasons noted above, especially the lack of both an air toxics inventory in Las Vegas and the uncertainty in establishing risk factors, FHWA believes that the costs to obtain such information would be excessive, and more importantly, our attempt would lack scientific credibility and be largely conjectural.

The Sonoma Technology effort supports the NEPA study we completed for the US 95 project. The FHWA does not approach the assessment of air toxics casually, regardless of the incomplete state of knowledge associated with the field. In addition to our ongoing research objectives, we co-sponsored a recent technical review panel under the umbrella of the National Academies of Science, focusing on the impacts of transportation-derived air toxics.

Conclusion

As your office indicated in its letter of February 5, 2002, FHWA does not believe that it is possible to accurately analyze MSAT impacts at the project level, given the present state of the science. Furthermore, absent such an analysis, there is no evidence that would support the need to prepare a Supplemental EIS under 23 CFR 771.130(a)(2). This may change in the future as new tools and methods are developed and the body of scientific knowledge on these health impacts continues to grow. However, since such tools and methods are not available, we continue to conclude, based on the Sonoma Technology, Inc. study, as well as the reasons explained in our memorandum to you of February 4, 2002, that the preparation of a Supplemental EIS on the US 95 project is not warranted. We will, of course, continue our research into this area and work closely with our EPA counterparts and other interested parties to expand our knowledge to ensure that we continue to appropriately address these important issues.

2 Attachments

cc:
Ed Kussy
Reid Alsop
Dave Ortez
Bob O'Loughlin