Recent disasters have highlighted the difficulties in assessing and managing risks and the types of failure that can occur in extreme circumstances. The means of characterizing and preparing for disasters can vary widely, even among engineers. Thus, clarity is required in communicating how scientific principles are applied in preventing and responding to disasters. This paper discusses lessons learned from environmental and other disasters regarding risk assessment and management, including the role of perception, and five types of failure that may occur during a disaster: miscalculations, extraordinary natural circumstances, critical path, negligence, and inaccurate prediction of contingencies. Examples from past disasters are used to illustrate these concepts.

Adopting and adapting emerging biotechnologies presents promise and challenges to the environmental engineer. Emerging biotreatment technologies that employ synthetic biology approaches, genetic engineering, and nanotechnologies present unique risk, reliability, and resilience profiles, especially given their unknown potential effects on human health and the environment. Decisions on whether and how to apply these technologies are challenging in light of the uncertainties about the potential environmental and health implications, including any downstream effects. Environmental engineers must balance the benefits of remediation, waste treatment, and other applications with these potential adverse effects by employing a systems view of the complexities in time and space to address the difficult-to-predict intended and unintended outcomes because these applications have few precedents. Insights and possible approaches to address these complexities and uncertainties are presented in this state-of-the-art review.

During the 20th century, air pollution control technologies grew at an amazingly rapid rate. Air quality in much of the industrialized world greatly improved as the efficiencies of these technologies improved. This continued improvement in pollution control has more recently been complemented with measures to prevent the emission of air pollutants. The previous, exclusive focus on treatment requires systems thinking. This review provides a framework for this Special Issue of Sustainability by describing the new tools that are needed to support this new, broader focus, including life cycle assessments, exposure models, and sustainable design.

To measure airborne asbestos and other fibers, an air sample must represent the actual number and size of fibers. Typically, mixed cellulose ester (MCE, 0.45 or 0.8 μm pore size) and, to a much lesser extent, capillary-pore polycarbonate (PC, 0.4 μm pore size) membrane filters are used to collect airborne asbestos for count measurement and fiber size analysis. In this research study, chrysotile asbestos (fibers both shorter and longer than 5 μm) were generated in an aerosol chamber and sampled by 25 mm diameter MCE filter media to compare the fiber retention efficiency of 0.45 μm pore size filters vs. 0.8 μm pore size filter media. In addition, the effect of plasma etching times on fiber densities was evaluated. This study demonstrated a significant difference in fiber retention efficiency between 0.45 μm and 0.8 μm pore size MCE filters for asbestos aerosols (structures longer than or equal to 0.5 μm length). The fiber retention efficiency of a 0.45 μm pore size MCE filter is statistically significantly higher than that of the 0.8 μm pore size MCE filter. However, for asbestos structures longer than 5μm, there is no statistically significant difference between the fiber retention efficiencies of the 0.45 μm and 0.8 μm pore size MCE filters. The mean density of asbestos fibers (longer than or equal to 0.5 μm) increased with etching time. Doubling the etching time increased the asbestos filter loading in this study by an average of 13%. The amount of plasma etching time had no effect on the filter loading for fibers longer than 5 μm. Many asbestos exposure risk models attribute health effects to fibers longer than 5 μm. In these models, both the 0.45 μm and 0.8 μm pore size MCE filter can produce suitable estimates of the airborne asbestos concentrations. However, some models suggest a more significant role for asbestos fibers shorter than 5 μm. Exposure monitoring for these models should consider only the 0.45 μm pore size MCE filters as recommended by the U.S. Environmental Protection Agency Asbestos Hazard Emergency Response Act (AHERA) protocol and other methods.