Hazardous and Solid Wastes and Health

Session Overview. The interest and importance of hazardous waste management among Pacific Rim countries was reflected in the numbers and scientific content of the papers presented. There were consecutive sessions for papers on hazardous chemicals, covering aspects of hazard assessment and risk minimization. Since some of the poorest and richest countries in the world were present at the conference, it is interesting to observe that essentially all countries present are experiencing the health costs associated with rapid industrial advancement. In this context, the chemicals of interest are similar, with super-regional concerns for arsenic, mercury and an expanding number of persistent, xenobiotic organics. Owing to various aspects of globalization and the astounding growth of East Asian economies, it is not surprising that lists of emerging hazardous waste problems are similar in many of these countries. The evolution of such problems has followed similar trajectories, for example, in the United States and China, where there is now an almost traditional concern for persistent organic pollutants derived from the electronics industry and associated solid wastes, emerging concerns for flame retardants and other newly identified hazards. The need for inexpensive, reliable tools for measuring chemical hazard is a concern held in common by developed and developing nations. That is, estimation of risk would improve significantly from development/adoption of integrated hazard measurement tools for metals (for example) and more reliable quantitative structure activity relationships for estimation of chemical toxicity. Both topics were featured in presentations at the conference. Similarly, both rich and poor nations would benefit from more cost effective remediation technologies that can be widely and reliably deployed. Phytoremediation was prominent among the conference presentations as were abiotic catalytic processes for destruction of trace organics and nitrate in water--in addition to bacterial catalysis for transformation of hazardous chemicals.

The primary difference in approaches to hazardous waste management between the developed and developing, then, are related to the method of exposure to hazardous chemicals and therefore the nature of intervention strategies to interrupt exposure pathways. The health of waste sorters, for example, is of concern in parts of East Asia, particularly since solid wastes continue to change in character. Mercury and arsenic exposures from indoor heating in rural China are a staggering environmental problem. The PBC Conference provided an ideal venue in which to explore similarities and differences in hazardous waste management tools and needs among participants. The value of accelerating information transfer in this area, which affects or will soon effect the inhabitants of both the developed and less developed worlds, was a central feature of all twelve PBC conferences to date.

Session Specifics

There were three sessions throughout the conference which focused on hazardous and solid wastes.The first session was chaired by Professor Margaret-Ann Armour, University of Alberta, Canada and Professor Nie Yongfeng, Tsinghua University, China and included eight papers from six countries and covered topics on the management, remediation and bioremediation of hazardous wastes. Two papers were related to the incineration of wastes: Professor Nie from Tsinghua University, Beijing has developed a method for converting fly ash from municipal incinerators to construction material. After washing to remove chlorides the fly ash is sintered to yield a non-leachable solid. Professor Kirk from the University of Toronto, Canada, described the production of an activated sulfur impregnated carbon which can control mercury emissions from the incineration of waste and in landfills. Professor Armour of the University of Alberta, Canada, shared her work on methods for the recovery of metal salts for reuse and the precipitation of heavy metal ions as insoluble silicates. Uses of titanium dioxide particles were described by two researchers. Professor Murugesan of Anna University in India has found that nanoparticles of titanium dioxide doped with magnesium metal are effective in the photo-catalytic decomposition of endocrine disruptors such as Bisphenol-A present in water resources. An advantage of these particles is that visible light can be used. The work of professor Mariquit of the Tokyo Institute of Technology, Japan, has shown that humic acids are decomposed on titanium dioxide in the presence of calcium ions. Bioremediation was the topic of four papers: professor Chakrabarti of the National Environmental Engineering Research Institute in India has studied the degradation of endosulfan by micro-organisms in a contaminated site and found that the addition of magnesium metal and acetic acid increase the efficiency of the degradation; Professor Fukuda of Nagaoka University in Japan has elucidated the mechanism of degradation of PCBs by the mycelia of maitake mushrooms with added lignin and is working on the application of this process to PCB-contaminated sites; and Ms. Parvin of Bangladesh Agricultural University has investigated the conditions under which spirulina platensis can be used to bioremediate poultry waste.

The second Hazardous Waste session of this conference presented the results of a number of studies describing the assessment or treatment of waste problems at local and regional scales around Asia. Two of the presentations discussed methods for assessing the degree of contamination of soils, as tools for indicating risks to public health and the potential need for risk management. Shao Chunyan and colleagues at the Shenyang Academy of Environmental Sciences in China presented a method for assessing the potential risk of mixtures of trace metals contaminating sites, a common issue globally. The investigators derived integrated soil threshold criteria for 6 trace metals based on leaching potential and direct soil contact. The integrated thresholds suggested by the authors are useful for the screening of sites contaminated by several trace metals, and site-specific risks can later be estimated definitively. In the second study, Huang Qifei and colleagues at the Research Institute of Solid Waste Management of the Chinese Academy of Environmental Sciences assessed the distributions of DDT and its breakdown products at three industrial sites, and identified typical attenuation patterns with increasing distance from the industrial plants, as well as with depth in soils. One presentation by R. Siva Sakthi Raj of Anna University in Chennai, India, evaluated the effectiveness of a pilot-scale biogas plant in decomposing various agricultural and food wastes to combust methane, which would otherwise be released to the atmosphere as a potent greenhouse gas.Two presentations assessed the efficacy of methods to remediate soils contaminated with persistent organics and trace metals. Helmi Hamdi and colleagues at Okayama University in Japan, as well as other colleagues from Lithuania and Tunisia, described tests of microbial and phytoremediation of PAHs contaminated soils amended with treated sewage sludge, and tested the residual toxicity of the soils after prolonged treatment. Saoussen Benzarti and colleagues at Okayama University concentrated on the remedial capabilities of a known trace metal hyperaccumulating plant Thlaspi sp. vs. three common crops (radish, lettuce and alfalfa) in removing copper, cadmium and zinc from nutrient solutions (as surrogates for pore waters in soils).The last group of presentations discussed two emerging areas of investigation, both of which have worldwide implications. S, Rengaraj of the Ecole des Mines in Nantes, France and colleagues from Hong Kong Polytechnic University described the photoactivation of Be- Tio 2 nanoparticle complexes to reduce nitrate wastes – a treatment process commonly needed for municipal and industrial wastewaters. Their project is illustrative of the current worldwide interest in developing new products and processes based on nanotechnology. In the second presentation in this group, Rajendra Prasad and colleagues at the National Environmental Engineering Research Institute (NEERI) in Nagpur, India discussed the evaluation of a range of physical-chemical characteristics of a large set of organic chemicals, in order to identify robust Quantitative Structure-Activity Relationships (QSARs) to predict the toxicity of the chemicals to the fathead minnow, Pimephales promelas. QSARs will be an important tool for International Chjemicals Management, including the Globally Harmonized System for the Hazard Classsification and Labeling of chemicals in commerce (GHS), as well as the REACH chemical risk assessment regulation in the European Union. As with the first Hazardous Waste session of the conference, the presentations of this session demonstrated the maturity of the science and engineering being advanced in Pacific Basin countries to address issues of both local and global significance.

The third solid and hazardous waste session was chaired by Donald Kirk of the University of Toronto, Canada and Selvaraj Rengaraj, of the Ecole de MInes, Nantes, France. In the waste technology sessions, there was an obvious need to understand health and technology impacts in MSW handling and disposal. In addition to the differences in MSW composition for developing and developed nations, there is a significant difference in the handling of wastes. Developing nations have a high recycling rate for materials that have economic value but at the human expense of garbage pickers, a class of low income people subsisting on their ability to extract value from discarded wastes. Developed nations have focused on recycling using government controls and industry subsidization, and to encourage curbside waste separation for potential reuse. In developed nations governments take ownership of trash to minimize human contact with these materials. This approach often restricts energy recovery and requires usage of controlled landfills. There is a lack of knowledge about the LCA of these approaches. There is a lack of knowledge about the carbon emissions, contaminants, human health impacts and economics. For example, if the risk to workers in the sorting and picking fields were known, training and licensing regulations might be able to be applied to minimize impacts, while not losing the economics of recycling. Developed nations have taken very different routes to handling MSW and it is not clear if there is a significant benefit to any of these approaches. We learned that China has tackled the problem of MSW combustion by-products such as the hazardous fly ash by water extraction, followed by stabilization, then use in cement or brick making. Research from India questioned the wisdom of hazardous waste in building materials. Industrialized nations have used different approaches to handling fly ash. France prefers encapsulation and landfill, NA uses direct hazardous waste landfill, co-disposal with MSW has been proposed, separation of heavy metals from ash is possible; there does not appear to be any consensus on what are the important criteria to be achieved.