Human Environment Fate and Transport Processes

Lead in the Human Environment Fate and Transport Processes 

This chapter also serves as an environmental road map, laying out the physical, physicochemical and chemical means by which lead is transported and mobilized in and out of environmental compartments that serve as lead contact points for human and ecological populations. Environmental compartment cycling of lead until recently was a largely unknown cluster of phenomena, and the multimedia impact of lead emissions on the larger biosphere was little understood and even misunderstood. This chapter is not intended to be encyclopedic, but it focuses on data eventually useful for human health risk assessment and regulatory initiatives. 

Trace Metals and other Contaminants in the Environment, Volume 10 

FIGURE 5.1 Environmental cycling of lead in the human environment. Line thickness varies with pathway importance for children. Source Mushak 1992. Elsevier Inc. Reprinted with permission. 

Some illustrative salient features of the depiction of lead s fate and transport can be summarized as follows  

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Chapter 5 Lead in the Human Environment Fate and Transport Processes ( 93 )... 

The third step in the risk assessment process is exposure assessment. In exposure assessment, the intake of a toxic agent from the environment is quantified using any combination of oral, inhalation, and dermal routes of exposure. This assessment may include a component for each route, such as when an assessor would investigate the potential impact of a point source of pollution. In this case, the magnitude of exposure depends on the amount of chemical used or released, chemical fate and transport, chemical concentration at the point of exposure, the routes and rates of uptake, the duration, the exposure setting (location and number of potential receptors, land use and human activities that could lead to exposure), and characteristics of receptors potentially exposed to the chemical. 

Mixtures Risk Assessment The mere occurrence of chemicals and contaminants in the environment does not increase the potential of risk to human or environment, but their exposure does. A five-step process is used to determine the extent, route, and duration of exposure and includes its environmental fate and transport. This process allows identification of likely site-specific exposure to chemicals and chemical mixtures, the extent of exposure, and the conditions under which the exposure occurred. This way contaminants of concern can be identified in a systematic manner by combining the chemical hazard and exposure data [7],... 

Product stewardship means "responsibly managing the health, safety, and environmental aspects of raw materials, intermediate, and consumer products throughout their life cycle and across the value chain in order to prevent or minimize negative impacts and maximize value" [7], Chapter 2 of this book discusses the technical tools that a product steward uses to achieve this goal. These tools include the techniques to characterize and predict the fate and transport of chemicals in the environment upon their manufacture and use. The tools also include the methods used to calculate the possible risks to human health and the environment that may result. Chapter 2 also describes the formal process of life cycle assessment, which uses these tools to evaluate the potential effects on the environment as a result of the production, use, and disposal or recycling of a product. 

It is now universally accepted that chemicals of commerce and those that may be formed inadvertently by processes such as combustion should be subjected to evaluation for their possible adverse effects on humans, the environment, and its various ecosystems. Earth surface processes are continually active with atmospheric, oceanic, and terrestrial media forces that foster chemical mobilization with long-range chemical transport within continental land masses, across the oceans, and on a global scale between the hemispheres. Monitoring data from remote locations provide evidence of this transport and these assertions are confirmed by the theoretical results of a variety of multimedia chemical fate and transport models. At the local level, the other geographic extreme, chemical sources are more intense and the pathways shorter and the impacts are therefore more severe. Anthropogenic substances have been mobilized and now exist in every nook, cranny, and recess of the physical environment and within many biological species. 

The Division of Chemistry and the Environment of the International Union of Pure and Applied Chemistry (IUPAC) has recently approved the creation of an IUPAC-sponsored book series entitled Biophysico-Chemical Processes in Environmental Systems to be published by John Wiley Sons, Hoboken, NJ. This series addresses the fundamentals of physical-chemical-biological interfacial interactions in the environment and the impacts on (1) the transformation, transport and fate of nutrients and pollutants, (2) food chain contamination and food quality and safety, and (3) ecosystem health, including human health. In contrast to classical books that focus largely on separate physical, chemical, and biological processes, this book series is unique in integrating the frontiers of knowledge on both fundamentals and impacts on interfacial interactions of these processes in the global environment. 

His interests have included the fate and effects of oil spills, especially under cold climate and arctic conditions, environmentally relevant physical chemical properties of organic chemicals and the development and validation of models of chemical fate in the environment. He has introduced the concept of fugacity to environmental modeling using Mackay-type models and has a particular interest in human exposure to chemical substances, bioaccumulation processes, that is, uptake of chemicals by a variety of organisms, and chemical transport to and fate in cold climates. 

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