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1 BACKGROUND The use of combustible materials in mass transportation vehicles has raised concern that' should the materials be involved in a fire, the toxicity of the combustion products may be a significant factor in preventing escape and/or rescue of those persons exposed. Recognizing the scope and extreme complexity of this issue, the Urban Mass Transportation Administration (UMTA), requested that the National Research Council (NRC) undertake a study of this issue. The study was conducted by the NRC's National Materials Advisory Board (NMAB), with assistance from the Transportation Research Board. 1 his report presents the results of the NMAB study. MISSION OF UMTA Established by the Urban Mass Transportation Act of 1964 and incorporated into the U.S. Department of Transportation in 1968, UMTA was created to provide assistance for the development of comprehensive and coordinated mass transportation systems, both public and private. UMTA assistance, primarily financial, has been provided through grants and funded technical efforts. UMTA's mission Is to assist in the development of improved mass transportation facilities, equipment, techniques, and methods; to encourage the planning and establishment of areawide urban mass transportation systems where they are cost effective; to provide assistance to state and local governments in financing such systems; and to encourage private sector involvement in local mass transportation systems. Within UMTA's organizational framework, the Safety and Security Office, under the direction of the associate administra- tor for technical assistance and safety, is responsible for transit safety. The mission of the Safety and Security Office is twofold: (1) to develop and administer a safety and security s
6 . program that provides technical assistance to transit agencies and entities; and (2) to provide oversight of safety and security efforts throughout the transit industry. To fulfill its mission, the Safety and Security Office has developed a program to promote and maintain a strong safety awareness in the transit industry and to equip the industry with tools to assist it in accomplishing the goal of providing the highest practical level of safety to transit patrons. UMTA provides funding to transit agencies throughout the United States and considers passenger safety a high priority. The primary recipients of these funds are urban rail and bus transit systems. UMTA capital assistant grants are mainly for facilities and rolling stock. To address fully the issue of fire safety in rail transit systems, UMTA initiated at its Transportation Systems Center a program to assess the overall fire threat in transit systems and to identify and develop suitable remedial actions. Fire safety efforts are directed at the prevention, detection, containment, and suppression of transit fires. Guidelines and recommended practices are being further developed by UMTA to assist and enhance transit operators' ability to identify and resolve fire threats and thereby minimize the fire threat in their systems. As an initial step in this program, UMTA issued its "Recommended Fire Safety Practices for Rail Transit Materials Selections (see Appendix A). Published in the Federal Register on August 14' 1984' and subsequently updated for transit buses and vans on July 2. _ · ~ ~ ~ . ~ · · . · · . . ~ ~ . · . . . . ~ . · . 1990, this document provides recommendations for testing and evaluating the flammability and smoke emission characteristics of materials used in the construction of heavy rail transit and light rail transit vehicles. These recommended practices are intended to minimize the fire threat in transit vehicles and thereby reduce injuries and damage resulting from transit vehicle fires. Not addressed by UMTA's recommended practices is the toxicity of the combustion products of burning materials. In an effort to respond to the transit industry's needs, UMTA initiated the present NMAB study to develop guidance for assessing the potential toxic hazards of the combustion products of materials used in mass transit vehicles. RELATED WORK Identifying and establishing the nature of all ongoing efforts to study the toxicity of combustion products were beyond the scope of this report. For that reason the following sections address only selected related governmental activities and efforts of the National Research Council. For a more thorough examination of the overall field of toxicity, the reader is referred to the literature. Suggested readings are listed in Appendix E. Governmental Activities The toxicity of the combustion products of construction materials Is an issue common not only to all modes of transportation but also to many other industries. Several departments and agencies of the federal government have initiated or are participating in efforts to address their respective concerns relative to the toxicity issue. In an effort to coordinate the efforts of these federal government organizations, the Consumer Product Safety Commission (CPSC) established the Interagency Fire Combustion Toxicity Work Group. This Work Group is composed of representatives of federal organizations that have an interest in combustion toxicity. It has met periodically in an effort to avoid duplication
7 of efforts, to share information, and to work cooperatively on projects to reduce fire toxicity deaths and injuries. Several members of the committee, namely the CPSC, the National Institute of Standards and Technology (NIST), the Federal Aviation Administration (FAA), and the Department of Defense, have conducted toxicity work within their own laboratories, and have sponsored the efforts of other members of the technical community. Federal organizations such as the FAA and the NIS(s Center for Fire Research have, in their laboratories, developed their own test protocols for evaluating the toxicity of combus- tior~ products. These and many other government organizations, such as UMTA and the Federal Emergency Management Agency, have also sponsored efforts in academia and other private sector organizations. Each organization conducting or sponsoring efforts to address the toxicity issue must, by the very nature of the issue, consider many of the same factors. The individual level of concern associated with the needs of each organization may, however, be quite different. Toxic products of combustion, when released in an environment such as a tunnel or in a closed compartment such as an aircraft cabin or submarine where there is no readily available means of egress, are of major concern to such organizations as UMTA, the FAA, and the U.S. Navy. For many rail transit vehicles that operate in tunnels, this concern is of particular importance because of the number of passengers that may be exposed. The situation is quite different in an open-air environment such as a bus, where rapid egress to a safe area is generally possible. In addition to the efforts of the aforementioned organizations, several organizations within the federal government are conducting research solely into the fire threat present in their respective jurisdictions. This research addresses the issues of transportation vehicle fires, mine fires, forest fires, building fires, and so forth. Relative to transportation, in addition to UMTA and the FAA, other U.S. Department of Transportation administrations known to be conducting fire safety research are the U.S. Coast Guard (USCG), the National Highway Traffic Safety Administration (NHTSA),-the Federal Highway Administration (FHWA), and the Federal Railroad Administration (FRA). The USCG research is conducted by the headquarters staff and the Coast Guard R&D Center in Groton, CT. Research efforts include both analytical studies and futI-scale testing conducted at the USCG fire test facility in Mobile, AL. The NHTSA is presently funding research directed at the develop- ment of a test protocol and test criteria for use in upgrading the performance requirements of Federal Motor Vehicle Safety Standard 302, Flammability of Interior Materiab. This test standard addresses the fire safety of bus materials. The FHWA research has addressed the initiation and propagation of fires in highway tunnels. The agency is currently sponsoring, through a highway construction grant, a full-scale evaluation of smoke and heat movement with various ventilation systems in a vehicular tunnel. The FRA's fire safety efforts have been directed at the promulgation of guidelines for rail passenger car materials and the fire safety of railroad tunnels. National Research Council In 1977 the NMAB published a lO-volume series of reports entitled Fire Safety Aspects of Polymeric Materials. The volumes covered materials, test methods for combus- tion and toxic gases, fire dynamics and scenarios, a guide to designers, civil and military aircraft, buildings, land transportation vehicles, ships, and mines and bunkers. Volume 3, "Smoke and Toxicity (Combustion Toxicology of Polymers, presented some conclusions relevant to the present study. A general conclusion stated in the summary was that, Present test methods are only partly adequate to evaluate polymeric materials. Also, toxic condi- tions generated by burning a single material may be greatly altered by the presence of other
8 burning materials. It is erroneous to consider that single toxicity tests offer a precise hazard evaluation. Rather, they offer a guide that may permit logical rating of toxicity under specified degradation conditions and permit the recognition of unusually toxic pyrolysis or combustion products (p. 1 1~. A related combustion toxicity study was carried out by the National Research Councils Committee on Fire Toxicity of the Board on Environmental Studies and Toxicolo- gy (1986~. The sponsors of this study were the FAA, CPSC, the U.S. Environmental Protection Agency, and the U.S. Navy. The committee's general task was to review the state of the art of combustion product toxicity anal fire hazard assessment, to consider the relationship between the physiological and behavioral end points currently used in combus- tion product toxicity test systems and the performance capabilities of humans exposed to pyrolysis and combustion products, and to evaluate fire hazard models that focus on toxicity. OBJECTIVES OF THE STUDY The present study was designed to give guidance to UMTA in addressing the potential toxic hazards of combustion-generated smoke. The objectives are summarized as follows: · to review the present state of knowledge of combustion toxicology, · to identify specific toxic hazards related to the combustion of materials used in transit vehicles, · to recommend guidelines for assessing materials for the potential toxic hazards of smoke produced in fires, and · to recommend research and development needed to develop an increased understanding of the combustion and toxicological phenomena associated with the burning of materials. APPROACH To study the problem, a committee of scientists was convened whose collective expertise consisted of combustion science, toxicology, fire modeling, the chemistry and physical properties of polymeric materials, analytical chemistry, transit safety, and systems engineering (see Appendix F). The committee held a series of meetings and carried out assignments between meetings. At the early meetings, committee members and guests gave tutorial presentations and expressed their views on the test methods and practices familiar to them. A number of sites were visited by the committee to tour facilities for conducting fire tests, to view the refurbishing of rail cars, to gather information on underground transit systems, and so forth. A draft report was compiled based on the tutorial presentations from experts, information garnered during site visits, publications submitted to and reviewed by the committee, committee members' own personal expertise, and a review of existing methods for evaluating the toxicity of the combustion products of materials.
9 REFERENCES National Materials Advisory Board, National Research Council. lg77. Fire Safety Aspects of Polymeric Materials, Vols. 1-10, National Academy of Sciences, Washington, DC. Board or Environmental Studies and Toxicology, National Research Council. 1986. Fire and Smoke: Understanding the Hazards, National Academy of Sciences, Washing- ton, DC.