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 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.


—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.


—An organism capable of transmitting an infectious agent to another organism.

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