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Water: Microbial

Thesaurus of Terms Used in Microbial Risk Assessment:

5.8   Dose-Response Terms

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additive dose

The overall result of exposure to two or more chemicals, when each chemical behaves as a concentration or dilution of the other chemicals in the mixture.  The response of the combination is the response expected from the equivalent dose of an index chemical.  The equivalent dose is the sum of component doses scaled by their toxic potency relative to the index chemical.  (EPA 2004)

additive effect

A biologic response to exposure to multiple substances that equals the sum of responses of all the individual substances added together.  (ATSDR 2004)
RELATED TERMS: antagonistic effect, synergistic effect

benchmark concentration          (ACRONYM: BMC)

SEE: benchmark dose

benchmark concentration lower confidence limit          (ACRONYM: BMCL)

SEE: benchmark dose lower confidence limit

benchmark dose          (ACRONYM: BMD)

A dose or concentration that produces a predetermined change in response rate of an adverse effect (called the benchmark response or BMR) compared to background.  (EPA 2003)

benchmark dose lower confidence limit          (ACRONYM: BMDL)

A statistical lower confidence limit on the dose or concentration at the BMD.  (EPA 2003)

benchmark response          (ACRONYM: BMR)

An adverse effect, used to define a benchmark dose from which an RfD (or RfC) can be developed.  The change in response rate over background of the BMR is usually in the range of 5-10%, which is the limit of responses typically observed in well-conducted animal experiments.  (EPA 2003)

biologically based dose-response model          (ACRONYM: BBDR model )

A predictive model that describes biological processes at the cellular and molecular level linking the target organ dose to the adverse effect.  (EPA 2003)

concentration-effect relationship

Relationship between the exposure, expressed in concentration, of a given organism, system, or (sub) population to an agent in a specific pattern during a given time and the magnitude of a continuously-graded effect to that organism, system, or (sub) population.  (IPCS/OECD 2004)
RELATED TERMS: effect assessment, dose-response relationship

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cumulative dose                 

The total dose resulting from repeated exposures of ionizing radiation to an occupationally exposed worker to the same portion of the body, or to the whole body, over a period of time (see 10 CFR 20.1003).  (RAIS 2004)

Note: It may be necessary to also determine cumulative dose for microbial pathogens if there is more than one source of exposure during a finite time or if there are multiple exposures to a single source. For microbial pathogens the cumulative dose period may be short (over hours or a day).

dose
  1. The amount of a substance available for interactions with metabolic processes or biologically significant receptors after crossing the outer boundary of an organism. 
    1. The POTENTIAL DOSE is the amount ingested, inhaled, or applied to the skin. 
    2. The APPLIED DOSE is the amount presented to an absorption barrier and available for absorption (although not necessarily having yet crossed the outer boundary of the organism). 
    3. The ABSORBED DOSE is the amount crossing a specific absorption barrier (e.g., the exchange boundaries of the skin, lung, and digestive tract) through uptake processes. 
    4. INTERNAL DOSE is a more general term denoting the amount absorbed without respect to specific absorption barriers or exchange boundaries.  
    5. The amount of the chemical available for interaction by any particular organ or cell is termed the DELIVERED or BIOLOGICALLY EFFECTIVE DOSE for that organ or cell.  (EPA 1997a, EPA 2003, EPA 2004, EPA 2005a)
    1. The actual quantity of a chemical administered to an organism or to which it is exposed.
    2. The amount of a substance that reaches a specific tissue (e.g., the liver).
    3. The amount of a substance available for interaction with metabolic processes after crossing the outer boundary of an organism.
  2. In terms of monitoring exposure levels, the amount of a toxic substance taken into the body over a given period of time. (EPA 2005e)
    1. (for non-radioactive chemicals) The amount of a substance to which a person is exposed over some time period.  Dose is a measurement of exposure.  Dose is often expressed as milligram (amount) per kilogram (a measure of body weight) per day (a measure of time) when people eat or drink contaminated water, food, or soil.  In general, the greater the dose, the greater the likelihood of an effect.  An “exposure dose” is how much of a substance is encountered in the environment.  An “absorbed dose” is the amount of a substance that actually got into the body through the eyes, skin, stomach, intestines, or lungs.
    2. (for radioactive chemicals) The radiation dose is the amount of energy from radiation that is actually absorbed by the body.  This is not the same as measurements of the amount of radiation in the environment.  (ATSDR 2004)
  3. The amount of a pathogen that enters or interacts with an organism.  (FAO/WHO 2003b, ILSI 2000)
    Includes discrete single doses and continuous and multiple exposures.  (ILSI 2000 text)
  4. The amount of a toxic component or the number of a pathogen that is ingested or interacts with an organism (host).  (FDA 2002)
  5. Total amount of an agent administered to, taken up or absorbed by an organism, system or (sub) population.  (IPCS/OECD 2004)
  6. The amount or concentration of undesired matter or energy deposited at the site of effect.  (SRA 2004)
  7. The amount of agent that enters a target after crossing an exposure surface.  If the exposure surface is an absorption barrier, the dose is an absorbed dose/uptake dose (see uptake); otherwise, it is an intake dose (see intake).  (See introductory comments.)  (IPCS 2004)
    RELATED TERMS: absorbed dose, administered dose, applied dose, potential dose
dose adjustment

Modification of doses used in animal experimentation to equivalent levels for human beings. The usual method is to calculate the ratio of body weights raised to some power, which is roughly equivalent to the ratio of surface areas; a simple ratio of body weights has also been used. (AIHA 2000)

dose rate
  1. Dose per unit time, for example in mg/day, sometimes also called dosage. Dose rates are often expressed on a per-unit body-weight basis, yielding units such as mg/kg/day (mg/kg-day). They are also often expressed as averages over some time period, for example a lifetime (EPA 1992).

In exposure assessment, dose per time unit (e.g., mg/day), sometimes also called dosage (EPA 1997b)
Dose per unit time.  (IPCS 2004)

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dose-effect relationship
  1. Relationship between the total amount of an agent administered to, taken up or absorbed by an organism, system or (sub) population and the magnitude of a continuously-graded effect to that organism, system or (sub)population.  (IPCS/OECD 2004)
  2. Determination of the quantitative relationship between exposure to a particular substance or activity and the incidence or severity of an effect.  Dose-response assessment evaluates the conditions under which the effect might occur and considers factors that influence relationships, such as intensity and pattern of exposure and age and lifestyle variables that could affect susceptibility.  Such assessments also can involve extrapolation of high-dose responses to low-dose responses and from animal responses to human responses.  The development of this relationship may involve the use of mathematical models.  (NYS 1998)
  3. The relationship between dose (usually an estimate of dose) and the gradation of the effect in a population, that is a biological change measured on a graded scale of severity, although at other times one may only be able to describe a qualitative effect that occurs within some range of exposure levels.  (RAIS 2004, SRA 2004)
    RELATED TERMS: effect assessment, dose-response relationship, concentration-effect relationship
dose-related effect

Any effect to an organism, system or (sub) population as a result of the quantity of an agent administered to, taken up or absorbed by that organism, system, or (sub) population.  (IPCS/OECD 2004)

dose-response
  1. Shifts in toxicological responses of an individual (such as alterations in severity) or populations (such as alterations in incidence) that are related to changes in the dose of any given substance.  (EPA 2005b)
  2. How an organism’s response to a toxic substance changes as its overall exposure to the substance changes. For example, a small dose of carbon monoxide may cause drowsiness; a large dose can be fatal. (EPA 2005e)
  3. The relationship between the amount of exposure [dose] to a substance and the resulting changes in body function or health (response).  (ATSDR 2004)
  4. The quantitative relationship between the dose of an agent and an effect caused by the agent.  (CRCWQT 2002)
  5. A relationship in which a change in amount, intensity, or duration of exposure to a pathogen is associated with a change in the manifestation and magnitude of human health effects.  (ILSI 2000)
  6. Relationship between the amount of an agent administered to, taken up or absorbed by an organism, system or (sub) population and the change developed in that organism, system or (sub) population in reaction to the agent.  Synonymous with dose-response relationship.  (IPCS/OECD 2004)
  7. A correlation between a quantified exposure (dose) and the proportion of a population that demonstrates a specific effect (response).  (RAIS 2004, SRA 2004)
    RELATED TERMS: dose-effect relationship, effect assessment, concentration-effect relationship, exposure-response
dose-response analysis

The process of characterizing the relation between pathogen dose, infectivity, and the manifestation and magnitude of health effects in an exposed population, including estimating the incidence of the health effects as a function of exposure to the pathogen.  (ILSI 2000)
RELATED TERMS: dose-response assessment

dose-response assessment
  1. A determination of the relationship between the magnitude of an administered, applied, or internal dose and a specific biological response.  Response can be expressed as measured or observed incidence or change in level of response, percent response in groups of subjects (or populations), or the probability of occurrence or change in level of response within a population.  (EPA 2003)
  2. A determination of the relationship between the magnitude of an administered, applied, or internal dose and a specific biological response.  Response can be expressed as measured or observed incidence, percent response in groups of subjects (or populations), or as the probability of occurrence within a population.  (EPA 2004)
    1. Estimating the potency of a chemical.
    2. In exposure assessment, the process of determining the relationship between the dose of a stressor and a specific biological response.
    3. Evaluating the quantitative relationship between dose and toxicological responses.  (EPA 2005b)
  3. The determination of the relationship between the magnitude of exposure (dose) to a chemical, biological or physical agent, and the severity and/or frequency of associated adverse health effects (response).  (CAC 1999, CAC 2003, FAO/WHO 2003b)
  4. The determination of the relationship between the magnitude of exposure and the magnitude and/or frequency of an effect.  (FDA 2002)
  5. Analysis of the relationship between the total amount of an agent administered to, taken up or absorbed by an organism, system or (sub)population and the changes developed in that organism, system or (sub)population in reaction to that agent,  and inferences derived from such an analysis with respect to the entire population.  Dose-Response Assessment is the second of four steps in risk assessment.  (IPCS/OECD 2004)
  6. The determination of the relationship between the magnitude of exposure (dose) to a microbiological agent and the severity and/or frequency of the associated adverse health effects (response).  (KIWA 2004)
  7. The process of characterizing the relation between the dose of an agent administered or received and the incidence of an adverse health effect in exposed populations and estimating the incidence of the effect as a function of human exposure to the agent. It takes account of intensity of exposure, age pattern of exposure, and possibly other variables that might affect response, such as sex, lifestyle, and other modifying factors. A dose-response assessment usually requires extrapolation from high to low dose and extrapolation from animals to humans. A dose-response assessment should describe and justify the methods of extrapolation used to predict incidence and should characterize the statistical and biologic uncertainties in these methods (NRC 1983).
  8. The process of characterizing the relation between the dose of an agent administered or received and the incidence of an adverse health effect in exposed populations and estimating the incidence of the effect as a function of human exposure to the agent.  (RAIS 2004, SRA 2004)
    RELATED TERMS: hazard characterization, dose-effect relationship, effect assessment, dose-response relationship, concentration-effect relationship

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dose-response curve
  1. A graphical representation of the quantitative relationship between administered, applied, or internal dose of a chemical or agent, and a specific biological response to that chemical or agent.  (EPA 2004)
  2. Graphical representation of the relationship between the dose of a stressor and the biological response thereto.  (EPA 2005b)
  3. A mathematical relationship between the dose administered or received and the incidence of adverse health effects in the exposed population; toxicity values are derived from this relationship (AIHA 2000).
  4. Graphical presentation of a dose-response relationship.  (IPCS/OECD 2004)
dose-response relationship
  1. The resulting biological responses in an organ or organism expressed as a function of a series of doses.  (EPA 1997a)
  2. The relationship between a quantified exposure (dose) and the proportion of subjects demonstrating specific biologically significant changes in incidence and/or in degree of change (response).  (EPA 2003)
  3. The quantitative relationship between the amount of exposure to a substance and the extent of toxic injury or disease produced.  (EPA 2005b)
  4. Relationship between the amount of an agent administered to, taken up or absorbed by an organism, system or (sub) population and the change developed in that organism, system or (sub) population in reaction to the agent (IPCS/OECD 2004)
    RELATED TERMS: dose-effect relationship, effect assessment, concentration-effect relationship

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infectious dose

The number of organisms that make individuals ill or carriers.  In reality, there is a probability distribution associated with different pathogen exposure levels.  (USDA 2004)
RELATED TERMS: minimum infective dose

infective dosex           (ACRONYM: IDx)

This term applies to the dose that will cause infection in x% of the population receiving the dose (e.g., ID50 for 50% of population).  (Microbial AWQC Methodology)
RELATED TERMS: lethal dose

internal dose

In exposure assessment, the amount of a substance penetrating the absorption barriers (e.g., skin, lung tissue, gastrointestinal tract) of an organism through either physical or biological processes.  (EPA 2004, EPA 2005b)

lethal dose           (ACRONYM: LD)

This term applies to the dose that will cause death in x% of the population receiving the dose (e.g., LD50 for 50% of population).  (Microbial AWQC Methodology)
RELATED TERMS: lethal dose-50, infective dosex

lethal dose-50          (ACRONYM: LD50)

The dose of a toxicant or microbe that will kill 50 percent of the test organisms within a designated period.  The lower the LD50, the more toxic the compound.  (EPA 2005b, EPA 2005e)

lowest acceptable daily dose

The largest quantity of a chemical that will not cause a toxic effect, as determined by animal studies.  (EPA 2005b)

minimum infective dose          (ACRONYM: MID)

This term was intended to indicate the lowest dose that would cause infection in an individual and assumed that there was a threshold dose.  This term generally considered to be obsolete because one microorganism is believed to be capable of causing infection in a susceptible individual.  However, it should be noted that infection does not imply symptomatic illness.  (EPA 2005f)
RELATED TERMS: contrast with quorum sensing

non-linear dose response
  1. A pattern of frequency or severity of biological response that does not vary directly with the amount of dose of an agent.  (EPA 2003)
  2. The term “nonlinear” is used in the Guidelines for Carcinogenic Risk Assessment in a narrower sense than its usual meaning in the field of mathematical modeling.  In the cancer guidelines, the term “nonlinear” refers to threshold models (which show no response over a range of low doses that include zero) and some nonthreshold models (e.g., a quadractic model, which shows some response at all doses above zero).  In the cancer guidelines, a nonlinear model is one whose slope is zero at (and perhaps above) a dose of zero.  (EPA 2005a)
non-threshold effect
  1. An effect (usually an adverse health effect) for which there is no exposure level below which the effect is not expected to occur.  (EPA 2004)
  2. A non-threshold model presumes that one organism can lead to infection.  (ILSI 2000 text)
    RELATED TERMS: contrast with threshold effect

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point of departure          (ACRONYM: POD)
  1. The dose-response point that marks the beginning of a low-dose extrapolation.  This point can be the lower bound on dose for an estimated incidence or a change in response level from a dose-response model (BMD), or a NOAEL or LOAEL for an observed incidence, or change in level of response.  (EPA 2003)
  2. A point of departure marks the beginning of extrapolation to lower doses.  The POD is an estimated dose (usually expressed in human-equivalent terms) near the lower end of the observed range, without significant extrapolation to lower doses.  (EPA 2005a)
potential dose

The amount of a compound contained in material swallowed, breathed, or applied to the skin.  (EPA 2004)

probability of illness

The likelihood that a susceptible host will develop symptomatic disease given sufficient exposure to a particular microorganism.  (ILSI 2000)

probability of infection

The likelihood that a particular microorganism will successfully establish itself in a given host or population.  (ILSI 2000)

response

Change developed in the state or dynamics of an organism, system or (sub) population in reaction to exposure to an agent.  (IPCS/OECD 2004)

threshold
  1. The dose or exposure below which no deleterious effect is expected to occur.  (EPA 2003)
  2. Threshold Dose/Threshold - The lowest dose of a chemical at which a specified measurable effect is observed and below which it is not observed.  (EPA 2004, EPA 2005b)
  3. Threshold Dose of a substance or exposure concentration below which a stated effect is not observed or expected to occur (disease).  (WHO 1999)
  4. Dose or exposure concentration of an agent below that a stated effect is not observed or expected to occur.  (IPCS/OECD 2004)
  5. A pollutant concentration [or dose], below which no deleterious effect occurs.  (RAIS 2004, SRA 2004)
  6. A threshold dose is a dose level below which there is no effect of radiation on the biological response.  It is often difficult to distinguish between a threshold and a linear-quadratic dose response where the response changes only slightly at low doses.  A threshold model postulates that radiation does not cause the effect at any level below the threshold.  Radiation thresholds are generally thought to be limited to acute (short-term) effects that are called deterministic, because they require depletion of certain cells in the body to below a critical number in a given organ or tissue.  These effects include radiation sickness (nausea and vomiting), infection and bleeding, and loss of hair.  (RERF 1999)
    RELATED TERMS: non-linear dose response, minimum infective dose

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threshold effect

An effect (usually an adverse health effect) for which there is an exposure level below which the effect is not expected to occur.  (EPA 2004, EPA 2005b)
RELATED TERMS: contrast with non-threshold effect

threshold limit value          (ACRONYM: TLV)
  1. Recommended guidelines for occupational exposure to airborne contaminants published by the American Conference of Governmental Industrial Hygienists (ACGIH).  TLVs represent the average concentration in mg/m3 for an 8-hour workday and a 40-hour workweek to which nearly all workers may be repeatedly exposed, day after day, without adverse effect.  (EPA 2003)
  2. Refers to airborne concentrations of substances and represents conditions under which it is believed that nearly all workers are protected while repeatedly exposed for an 8-hr day, 5 days a week (expressed as parts per million (ppm) for gases and vapors and as milligrams per cubic meter (mg/m3) for fumes, mists, and dusts).  (RAIS 2004, SRA 2004)

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