Applying probabilistic material flow analysis for quality control and management of waste recycling in steelmaking.

In modern steelmaking, multiple processes comprise a continuous manufacturing system, but not all phosphorus content data are connected or integrated into a holistic and systematic database. Disconnected data hinder the improvement of material management and resource efficiency in the industry. The objective of this study was to establish a method to evaluate material flows, reduce uncertainty, and perform quality control for waste recycling in the steelmaking industry. The results indicate that 10% of the phosphorus input is present in the final products, 30% accumulates in the slags, and more than 60% of the total mass remains in the processes. Comparing the material flow analysis results obtained using static and probabilistic approaches, the partition ratio of the phosphorus content in slags changes from 24.07% to 40.78%, but that in processes changes from 49.10% to 68.05%. This indicates that the variations in phosphorus content in slags and processes might affect the effectiveness of slag recycling and might increase the resource consumption required to maintain the quality of final products. The probability of forming substandard products in the baseline scenario is 0.43. Adopting a 50% removal rate, the probabilities of forming substandard products are reduced to 0.36 (waste removal scenario), 0.38 (slag reduction scenario), and 0.31 (raw material treatment scenario). The performance of raw material treatment and waste removal is more efficient for quality control. The method used in this study can be applied to evaluate the possible outcomes of waste recycling and reduce the probability of forming substandard products.

Twice the effort: Ineffectiveness of selecting air pollution control targets with emission quantity for risk reduction.

Protection of human health from air pollution has been typically pursued primarily via regulations of air quality standards and emission standards. Although reducing air pollution from the largest sources and placing more stringent emission limits on the industries of focus is a criterion used by decision makers to control air pollution, it is not clear whether this criterion is the most effective and efficient in improving health protection. Pollutants released from sources into the environment are spatially fluctuating rather than uniformly distributed, and hence, health risk is an issue of geographic variability. To address this issue, this study used a representative example of lead (Pb) in Taiwan. This study implemented an IO-RA methodology to redefine the effectiveness of air pollution management and rank the control priorities of target industries using different perspectives, i.e., environmental responsibility, economic benefit and repercussion potential. This study also considered the potential differences in policy effectiveness based on the air pollution control targets and ranked the industries according to their effectiveness in health risk improvement across the three perspectives and pure emission quantities. After determining the cause-effect chain of health risk through IO-RA, authorities can partner with specific industries according to the chosen effectiveness criteria and thus facilitate better policy performance.

The influence of spatial resolution on human health risk co-benefit estimates for global climate policy assessments.

Assessment of the ability of climate policies to produce desired improvements in public health through co-benefits of air pollution reduction can consume resources in both time and research funds. These resources increase significantly as the spatial resolution of models increases. In addition, the level of spatial detail available in macroeconomic models at the heart of climate policy assessments is much lower than that available in traditional human health risk modeling. It is therefore important to determine whether increasing spatial resolution considerably affects risk-based decisions; which kinds of decisions might be affected; and under what conditions they will be affected. Human health risk co-benefits from carbon emissions reductions that bring about concurrent reductions in Particulate Matter (PM10) emissions is therefore examined here at four levels of spatial resolution (Uniform Nation, Uniform Region, Uniform County/city, Health Risk Assessment) in a case study of Taiwan as one of the geographic regions of a global macroeceonomic model, with results that are representative of small, industrialized nations within that global model. A metric of human health risk mortality (YOLL, years of life lost in life expectancy) is compared under assessments ranging from a "uniform simulation" in which there is no spatial resolution of changes in ambient air concentration under a policy to a "highly spatially resolved simulation" (called here Health Risk Assessment). PM10 is chosen in this study as the indicator of air pollution for which risks are assessed due to its significance as a co-benefit of carbon emissions reductions within climate mitigation policy. For the policy examined, the four estimates of mortality in the entirety of Taiwan are 747 YOLL, 834 YOLL, 984 YOLL and 916 YOLL, under Uniform Taiwan, Uniform Region, Uniform County and Health Risk Assessment respectively; or differences of 18%, 9%, 7% if the HRA methodology is taken as the baseline. While these differences are small compared to uncertainties in health risk assessment more generally, the ranks of different regions and of emissions categories as the focus of regulatory efforts estimated at these four levels of spatial resolution are quite different. The results suggest that issues of risk equity within a nation might be missed by the lower levels of spatial resolution, suggesting that low resolution models are suited to calculating national cost-benefit ratios but not as suited to assessing co-benefits of climate policies reflecting intersubject variability in risk, or in identifying sub-national regions and emissions sectors on which to focus attention (although even here, the errors introduced by low spatial resolution are generally less than 40%).

Assessing the transfer of risk due to transportation of agricultural products.

Health risk assessment (HRA) is the process used to estimate adverse health effects on humans. The importance and sensitivity of food chains to HRA have been observed, but the impact of the transportation of food has generally been ignored. This study developed an exposure assessment to demonstrate the significance of the transportation of agricultural products in HRA. The associated case study estimated the health risks derived from various sources of arsenic emissions in Taiwan. Two assessment scenarios, self-sufficiency and transportation of agricultural products, were compared to calculate risk transfer ratios that show the impact of agriculture transportation. The risk transfer ratios found by the study range from 0.22 to 42.10, indicating that the quantity of transportation of agricultural products is the critical factor. High air deposition and high agricultural production are the two main contributors to the effect of the transportation of agricultural products on HRA. Risk reduction measures could be applied to high-pollution areas as well as to areas with high agricultural productivity to reduce ingestion risks to residents. Certain areas that are sensitive to the transportation of agricultural products may incur more risks if emissions increase in agriculturally productive counties.

Integrating input output analysis with risk assessment to evaluate the population risk of arsenic.

Multimedia and site-specific risk assessments (RA) of major sources releasing arsenic (As) were converted into sector-based risk coefficients, which were integrated with the Input Output Table (IO) to analyze the association between sector activities and health risks. The developed IO-RA framework is a valuable tool for unfolding the risk chain linking the receptors, exposure pathways, emission sources, and production and consumption activities associated with various industrial sectors. The enlarged decision space along the chain can then be considered in planning risk management strategies. This case study estimates that air emissions of As result in 1.54 carcinogenic cases. Export is the primary driving force and accounts for approximately 48% of the final demand that leads to population risks of As. The ranking of the contribution of the five sectors in terms of total population risks is as follows: electricity supply (1.06E+00), steelmaking (2.2 × 10(-1)), cement kilns (1.50 × 10(-1)), semiconductor manufacturing (6.34 × 10(-2)) and incinerators (4.31 × 10(-2)). The electricity supply, steelmaking industry, and cement kilns are the major sectors, not only because their emissions directly cause risk but also because they have a stronger influence on the risk generated by other sectors.

Life cycle risk assessment of bottom ash reuse.

The life cycle thinking was integrated with risk assessment to develop the life cycle risk assessment (LCRA) methodology in this study. Because LCRA assessed risks from a life cycle perspective of the concerned policies, it was helpful to identify important sources, contaminants, receptors and exposure pathways along the life cycle of reuse activities. The case study showed that different reuse scenarios resulted in risk shift between different life stages and receptors, and using duration of pavement was an essential factor for risk management. When ash reuse strategies were made based on a focus on the stage of reuse, the rank of strategies were shown to be different from the one based on the total population risks over the entire life cycle. This demonstrated the importance of decision criteria used in selecting reuse strategies. The results also showed that when bottom ash was reused, the health risk was shifted to the laborers; the individual risks of laborers were higher than residents through exposure to Cr and Cd via inhalation and dermal contact. Although the population risk at the treatment stage was the highest, the smaller size of exposed population would make it quite effective to reduce the risk of the laborers.

Assessing the health risk of reuse of bottom ash in road paving.

Although the reuse of bottom ash has been favored gradually, reflected on regulations and researches, the associated risk is still an issue of great concern. This study quantified the health risks from multimedia transport and multi-pathway exposure to the concerned chemicals as a result of reusing bottom ash in road paving with consideration of various application scenarios. In particular, the using duration of the pavement was taken into consideration because movement of chemicals in the soils and groundwater would affect the subsequent exposure and risk. By using soil and groundwater transport modeling linked to food chain exposure assessment and incorporating the Monte Carlo method, the study identified Cr as the crucial toxicant and ingestion of drinking water and vegetables as the key exposure pathways. Furthermore, control of the using duration of road pavement is an essential factor of management and regulations to minimize the leaching of the hazardous constituents into the groundwater and subsequent contamination of food chain.

The Health Risk assessment of Pb and Cr leached from fly ash monolith landfill.

As of 2004, nearly two hundred thousand tons of fly ash monoliths are created each year in Taiwan to confine heavy metals for reducing the leaching quantity by precipitation. However, due to abnormal monolith fracture, poorly liner quality or exceeding usage over designed landfill capacity, serious groundwater pollution of the landfills has been reported. This research focuses on Pb and Cr leaching from monolithic landfill to assess the risk of groundwater pollution in the vicinity. The methodology combines water budget simulations using HELP model with fate and risk simulations using MMSOILS model for 5 kinds of landfill structures and 2 types of leaching models, and calculates the risk distribution over 400 grids in the down gradient direction of groundwater. The results demonstrated that the worst liner quality will cause the largest risk and the most significant exposure pathway is groundwater intake, which accounted for 98% of the total risk. Comparing Pb and Cr concentrations in the groundwater with the drinking water standards, only 14.25% of the total grids are found to be under 0.05 mg/L of Pb, and over 96.5% of the total grids are in the safety range of Cr. It indicates that Pb leaching from fly ash monolithic landfills may cause serious health risks. Without consideration of the parameters uncertainty, the cancer and noncancer risk of Pb with the sanitary landfill method was 4.23E-07 and 0.63, respectively, both under acceptable levels. However, by considering the parameters uncertainty, the non-carcinogenic risk of Pb became 1.43, exceeding the acceptable level. Only under the sealed landfill method was the hazard quotient below 1. It is important to use at least the sealed landfill for fly ash monoliths containing lead to effectively reduce health risks.