What is an example of how to focus on contaminants in the environment
This section describes factors to consider when evaluating fate and transport of environmental contaminants, the second element of the exposure pathway evaluation. It provides guidance for issues that you might need to consider on some sites. Not every site requires a comprehensive fate and transport analysis to categorize exposure pathways. Show
“Fate and transport” refers to how the nature of contaminants might change (chemically, physically, or biologically) and where they go as they move through the environment. Fate and transport evaluations help you determine how likely it is that 1) contaminants have moved or will move beyond the source area, and 2) contamination could migrate and exposures could occur beyond the sampled areas. The fate and transport analysis is generally a qualitative exercise that does not require quantitative evaluations (modeling studies). Depending on your site, you might consider different types of information when evaluating fate and transport. The following categories of information may be useful:
The extent to which you examine fate and transport issues depends on many factors, such as the availability of site-specific environmental data sets, the complexity of site issues, and community health concerns. If you determine that the nature and extent of contamination in all relevant media have been adequately characterized after reviewing pertinent studies, you might need little or no fate and transport evaluation. But if you are not able to adequately characterize the fate and transport of contamination, you cannot rule out that contaminants traveled to relevant site-specific media. You can often obtain pertinent fate and transport information in site investigation reports. All Superfund remedial investigation reports, for example, include contaminant- and media-specific fate and transport information. When evaluating and interpreting fate and transport information, you might need to consult technical experts (e.g., hydrogeologists, air modelers), especially when more quantitative analyses are needed to characterize affected media. When Is a Fate and Transport Evaluation Required? An evaluation might be required to answer questions such as these:
Using Judgment When Evaluating Fate and Transport Health assessors often use their professional judgment when evaluating environmental fate and transport. For example, suppose that at your site, there was a massive release of polychlorinated biphenyls (PCBs) into a river, and sampling studies found elevated levels of PCBs in fish tissues. Based on your understanding of how PCBs bioaccumulate, you can safely assume that part of the PCBs detected in the fish probably originated from the spill. You do not have to run a hydrology and bioaccumulation model to prove that fate and transport exists, nor do you have to step through every contaminant and physical property of PCBs to evaluate their fate and transport. Determining Fate and Transport ProcessesFate and transport are interdependent processes. Fate is what eventually happens to contaminants released to the environment. Some fraction of the contaminants might simply move from one location to the next; other fractions might be physically, biologically, or chemically transformed; and others still might accumulate in one or more media. Transport is the movement of gases, liquids, and particulate solids within a given medium and across interfaces between water, soil, sediment, air, plants, and animals. When evaluating sites, you need an overall appreciation of the primary release processes, intermedia transfer mechanisms, and transport pathways that might influence the ultimate fate of site-related contamination. Depending on site issues, understanding these basic fate and transport mechanisms (see table below) can help you understand the implications for possible past, current, and future exposures. In addition, find out how chemical and site-specific factors may affect contaminant transport in this fate and transport resource. Ways That Fate and Transport Mechanisms Can Influence Potential Exposure Points Ways That Fate and Transport Mechanisms Can Influence Potential Exposure Points
Considering Physical, Chemical, and Biological Contaminant PropertiesUnderstanding a contaminant’s physical, chemical, and biological properties (see table) can provide insights into its behavior in the environment and help you focus on transport mechanisms of possible significance. However, it’s important to remember that the scientific community’s understanding of chemical and physical properties is the result of laboratory studies in highly controlled conditions. This contaminant property information does not allow us to always predict completely how contaminants will behave under real-world environmental conditions. Laboratory studies also do not usually reflect the multiple variables and influences found in the environment such as chemical mixtures, biological and chemical processes in the environment, and geochemical conditions of soils and geologic materials. Thus, health assessors should not rely too heavily upon theoretical and laboratory studies to predict the fate and transport of site-specific contaminants. Site-specific environmental measurements that reveal how much and where contamination exists are always preferred. Common Chemical and Physical Properties Common Chemical and Physical Properties
ATSDR’s Toxicological Profiles (Tox Profiles) are a unique compilation of information on hazardous substances. They include details on various topics such as contaminant-specific properties, fate and transport, and where contaminants are found in the environment. More The U.S. National Library of Medicine’s PubChem is an open chemistry database that provides information on the chemical, physical, and biological properties of many contaminants. Moreexternal icon Examining Site-Specific FactorsMany climatic as well as geologic and hydrogeologic factors can affect—speed up, slow down, or even stop—how contaminants move through the environment and whether human exposures occur. For example, precipitation, topography, hydrology, hydrogeology, and soil type indicate how quickly water-soluble contaminants will enter groundwater, while temperature and other factors affect whether and how quickly contaminants will volatilize into the air. Pertinent information is usually documented in site investigation reports and other information sources. Climatic FactorsClimate can be important when determining the likelihood of contaminant movement in a setting. The following are some of the key climatic factors affecting environmental fate and transport:
Geologic and Hydrogeologic ConditionsGeologic and hydrogeologic conditions will influence how fast and in what direction contaminants in soil and groundwater might move, and ultimately if and how contaminants might reach people. Consider these conditions when deciding whether available sampling data are sufficient to characterize exposure points. GRASP can help develop maps to illustrate these conditions at your site (see example GRASP maps). The following are some key considerations:
Remember: Human-made objects, such as sewers, culverts, and drainage channels, can create or alter exposure pathways by changing the movement of contaminants through the environment.
What are some examples of environmental contaminants?These include radon, most criteria air pollutants (e.g., ozone, nitrogen dioxide, carbon monoxide, particulate matter), and biological agents (e.g., molds, certain infectious agents such as bacteria or viruses, dust mites).
What are contaminants with example?Examples of chemical contaminants include nitrogen, bleach, salts, pesticides, metals, toxins produced by bacteria, and human or animal drugs. Biological contaminants are organisms in water. They are also referred to as microbes or microbiological contaminants.
How do we contaminate the environment?The source
Most contaminants enter the environment from industrial and commercial facilities; oil and chemical spills; non-point sources such as roads, parking lots, and storm drains; and wastewater treatment plants and sewage systems.
What is an environmental contaminant?Environmental contaminants are chemicals that accidentally or deliberately enter the environment, often, but not always, as a result of human activities. Some of these contaminants may have been manufactured for industrial use and because they are very stable, they do not break down easily.
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