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Biosolids Applied to Land: Advancing Standards and Practices Glossary Aggregate exposure —Exposure to a single chemical by multiple pathways and routes of exposure. Benchmark dose —An exposure level that corresponds to a statistical lower bound on a standard probability of an effect, such as 10% of people affected. Bioaerosols —Aerosolized biological particles that range in diameter from 0.02 to 100 micrometers. Biomarker —Changes in the characteristics of a biologic sample, such as changes in enzyme levels, that reflect a particular environmental exposure, a particular human or animal disease process, or evidence of increased or decreased susceptibility to adverse effects from such exposures. Biosolids —Defined by EPA as the primarily organic solid product yielded by municipal wastewater treatment processes that can be beneficially recycled (whether or not they are currently being recycled). The term is defined in this report as sewage sludge that has been treated to meet the land-application standards in the Part 503 rule or any other equivalent land-application standards. Cumulative exposure —Combined exposures to multiple pollutants by multiple pathways and routes of exposure. Default assumption —An assumption about a receptor population characteristic that is made when actual information about that characteristic is unavailable. Domestic sewage —Waste and wastewater from humans or household operations that is discharged to or otherwise enters a treatment works.
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Biosolids Applied to Land: Advancing Standards and Practices Endotoxin —A complex bacterial toxin composed of protein, lipid, and polysaccharide that is released upon lysis of the cell. Exposure —Contact of an individual with a chemical or physical agent. Exposure is quantified as the amount of the agent available at the exchange boundaries of the individual (e.g., skin, lungs, gut) and available for absorption. Exposure assessment —The determination or estimation (qualitative or quantitative) of the magnitude, frequency, duration, and route of exposure. Exposure pathway —The course a chemical or physical agent takes from a source to an exposed individual. An exposure pathway describes a mechanism by which an individual or population is exposed to chemical or physical agents at or originating from a site. Each exposure pathway includes a source or release from a source, an exposure point, and an exposure route. If the exposure point differs from the source, a transport/exposure medium (e.g., air) or media (in cases of intermediate transfer) also is included. Highly exposed individual (HEI) —An individual who remains for an extended period at or adjacent to the site where maximum exposure occurs. Indicator organism —A microorganism that is used for monitoring whether a certain set of pathogens might be present. Indirect exposure —Exposure involving multimedia transport of chemicals from source to exposed individual. For example, consumption of produce grown on biosolids-amended soil. Loading rate —The maximum loading limit of a chemical per unit of time, permissible on a given site. Margin of exposure —A ratio defined by EPA as a dose derived from a tumor bioassay, epidemiological study, or biologic marker study, such as the dose associated with a 10% response rate, divided by an actual or projected human exposure. Mutipathway exposure —Exposure to an agent (chemical, physical, or biological) by various routes, such as inhalation, ingestion, and dermal absorption. No-observed-adverse-effect level —The highest dose of a chemical that was administered to animals in a toxicity study without producing an observed adverse effect. Probabilistic approaches —Evaluating a range of possible risk estimates and their likelihood, tied to various mathematical models of the likely distribution of potential values, instead of relying on single numbers or point estimates. Reasonable Maximum Exposure (RME) —A semiquantitative term referring to the lower portion of the high end of the exposure distribution. It
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Biosolids Applied to Land: Advancing Standards and Practices typically determined using a combination of average and upper-bound values for various exposure parameters so that the final exposure estimate will be an upper-bound exposure with a reasonable expectation of occurrence, usually considered the 95th percentile. Receptor population —The groups of people that may be exposed to the contaminated media. Secondary transmission —The spread of disease by indirect transmission of the infectious agent. Transmission can be from person-to-person contact, whereby an infected individual infects another, from exposure to contaminated objects, or via environmental pathways, such as contamination of soil or surface water. Sewage sludge —The solid, semi-solid, or liquid residue generated during the treatment of domestic sewage in a treatment works. Stakeholders —Stakeholders are groups who are potentially affected by the risk, risk managers, and groups that will be affected by efforts to manage the source of the risk. They could include federal regulators, state regulators, biosolids managers, local businesses, industries, public health officials, clinicians, and citizens. Susceptible subpopulation —Populations which may exhibit a greater effect in response to particular exposures. Uncertainty analysis —Analysis of information about risks that is only partly known or unknowable. Mathematical uncertainty analyses can be used to generate probabilistic distributions of risk estimates that reflect the extent to which the information used to assess risk is uncertain. Variability —A population’s natural heterogeneity or diversity, particularly that which contributes to differences in exposure levels or in susceptibility to the effects of chemical exposures. Vector —An organism capable of transmitting an infectious agent to another organism.
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