Environmental Engineering and Bioterrorism

The post-September 11 events have caused many people to reassess interests, goals, and activities. In the particular sphere of protecting against bioterrorism threats and mitigating their effects, there is a particular role for environmental engineering researchers and practitioners. A useful definition of environmental engineering is ‘‘the application of engineering principles to improve and maintain the environment for the protection of human health, for the protection of nature’s beneficial ecosystems, and for environment-related enhancement of the quality of human life’’ ~Bylaws of the American Academy of Environmental Engineers!. The autumn 2001 anthrax events have caused the threat of bioterrorism to gain increasing recognition. However, this has not been the first realized or threatened malicious use of biological agents. At least 200 such situations have occurred worldwide since 1900. The understanding of and response to a threat posed by a malicious biological release definitely involves the use of ‘‘engineering principles to improve and maintain the environment for the protection of human health.’’ Particularly, this requires skills that are in the toolbox of environmental engineers, including risk assessment ~dose-response modeling, exposure assessment!, cleanup technologies, and design of systems to reduce vulnerability. The question of ‘‘what is a safe level’’ poses questions in the context of bioterrorist events that are quite analogous to the question ‘‘how clean is clean’’ in the context of site remediation. It is entirely possible to develop dose-response relationships for pathogens that could potentially be used. From this, with the usual exposure calculations we perform ~how much air is breathed, water or food consumed, etc.!, one can arrive at an answer ~with input from decision makers as to acceptable risk!. The question of how to remediate a site where exposure occurs may involve technologies that are quite familiar ~albeit in other contexts! to environmental engineers. For example, in the remediation of the Hart Senate Office Building, the use of chlorine dioxide, which is used in drinking-water disinfection, played a significant role. We have learned particularly over the past 25 years how to design water and wastewater disinfection systems to achieve public health protection, and more recently how to apply UV to treat infectious agents in air. The development of rational standards for remediation of spaces contaminated with infectious agents is amenable to similar approaches, and environmental engineers should be central to this activity. There are interesting and complex issues with respect to the design of facilities resistant to contamination ~or spread of contamination! from malicious use of microorganisms and to the remediation of spaces in which such use has occurred. When the problem focus is on the ~indoor! air or contact surfaces with air ~e.g., HVAC ducts!, the spread of contamination and the rate at which remediation can occur ~due to penetration of any chemical agents that may be used in the gas phase! can be limited by transport through this complex environment. Lessons that have been learned in the field of indoor air pollution and industrial hygiene have direct relevance. Many of the facilities that could be targets for malicious use of microorganisms are directly within the purview of frequent environmental engineering activity. These include drinking-water systems, wastewater collection, and treatment systems. These must be looked at in detail on a site-specific basis to assess whether additional barriers ~in the form of treatment, monitoring, site modifications or security! need to be put in place to reduce vulnerability. Environmental engineers will need to work in close collaboration with colleagues in mechanical, architectural, civil, and other engineering disciplines in these tasks. Environmental engineers design systems and processes to protect against and cleanup after the release of contaminants into air, water, and land environments. These activities are equally necessary and appropriate when the contaminants are microbial and are released as a consequence of deliberate malicious activity. Vulnerability assessments of these systems to potential threats can be conducted by environmental engineers applying tools perfected in such disciplines as nuclear or mechanical engineering ~failure analysis, event-tree analysis, probabilistic safety, and reliability analysis!. Hence, there is no question that there is a link between environmental engineering and bioterrorism. As there are new challenges to the public health and the environment, our profession must rise to the occasion and show our strength in new applications. But one of the strengths, and joys, of the profession has been the historic incorporation of new skills to meet newly recognized challenges.