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Water: Microbial

Thesaurus of Terms Used in Microbial Risk Assessment - 5.4  Hazard Occurrence Terms (Pathogen Occurrence Terms)

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airborne transmission
  1. The spread of infectious microorganisms through the air, usually over distances greater than one meter from the infected host.  (Queensland Health 2005)
    RELATED TERMS: bioaerosol
background levels
  1. The concentration of a chemical already present in an environmental medium due to sources other than those under study.  Two types of background levels may exist for chemical substances: (a) Naturally occurring levels of substances present in the environment, and (b) Anthropogenic concentrations of substances present in the environment due to human associated activities (e.g., automobiles, industries).  (EPA 2004)
  2. Two types of background levels may exist for chemical substances:
    1. Naturally occurring levels: ambient concentrations of substances present in the environment, without human influence.
    2. Anthropogenic levels: concentrations of substances present in the environment due to human-made, non-site sources (e.g., automobiles, industries).  (EPA 2003)
  3. The concentration of a substance in an environmental media (air, water, or soil) that occurs naturally or is not the result of human activities. In exposure assessment the concentration of a substance in a defined control area, during a fixed period of time before, during, or after a data-gathering operation.  (EPA 2005b)
  4. An average or expected amount of a substance or radioactive material in a specific environment, or typical amounts of substances that occur naturally in an environment.  (ATSDR 2004)
  5. In air pollution, the level of pollutants present in ambient air from natural sources.  More generally, the level of pollution present in any environmental medium attributable to natural or ubiquitous sources.  (RAIS 2004, SRA 2004)
  6. The average amount of a substance present in the environment.  Originally referring to naturally occurring phenomena.  Used in toxic substance monitoring.  (Stedman 2005)
  7. The amount of an agent in a medium (e.g., water, soil) that is not attributed to the source(s) under investigation in an exposure assessment.  Background level(s) can be naturally occurring or the result of human activities.  (Note: Natural background is the concentration of an agent in a medium that occurs naturally or is not the result of human activities.)  (IPCS 2004)

Note that in some cases the definition is limited to natural sources and in other cases natural and anthropogenic sources are added together.

background source

Any source from which pollutants are released and contribute to the background level of a pollutant, such as volcano eruptions, windblown dust, or manmade source upwind of the study area.  (EPA 2004)

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biological monitoring
  1. The measurement of chemicals in biological media (e.g., blood, urine, exhaled breath) to determine whether chemical exposure in humans, animals, or plants has occurred.  (EPA 2004)
  2. Measuring hazardous substances in biologic materials (such as blood, hair, urine, or breath) to determine whether exposure has occurred. A blood test for lead is an example of biologic monitoring.  (ATSDR 2004)
  3. Biomonitoring: 1. The use of living organisms to test the suitability of effluents for discharge into receiving waters and to test the quality of such waters downstream from the discharge.  2. Analysis of blood, urine, tissues, etc. to measure chemical exposure in humans.  (EPA 2005b)

Analytical device comprising a biological recognition element (e.g. enzyme, receptor, DNA, antibody, or microorganism) in intimate contact with an electrochemical, optical, thermal, or acoustic signal transducer that together permit analyses of chemical properties or quantities. Shows potential development in some areas, including environmental monitoring.  (EPA 2005b)

composite sample
  1. A series of water samples taken over a given period of time and weighted by flow rate. (EPA 2005b)
  2. A sample of water, soil or other medium which is made by combining samples from two or more locations.  (NYDOH1999)

Note: composite samples may be used in sampling for microorganisms in the environment especially if there is a desire to provide estimates of microbial concentrations over some discrete period of time or area.

  1. The relative amount of a substance mixed with another substance. An example is five ppm of carbon monoxide in air or 1 mg/l of iron in water.  (EPA 2005b, EPA 2005e)
  2. The amount of a substance present in a certain amount of soil, water, air, food, blood, hair, urine, breath, or any other media.  (ATSDR 2004)
  3. Amount of a material or agent dissolved or contained in unit quantity in a given medium or system.  (IPCS/OECD 2004)
  1. The movement of underground contaminants from one level or area to another due to invasive subsurface activities.  (EPA 2005b)
  2. Direct or indirect transfer of a pathogen from one medium (e.g., food or water) to another.  (ILSI 2000)

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detection limit
  1. The lowest concentration of a chemical that can reliably with analytical methods be distinguished from a zero concentration.  (EPA 2004)
  2. The lowest concentration of a chemical that can reliably be distinguished from a zero concentration.  (EPA 2005b, ATSDR 2004)
environmental fate model

In the context of exposure assessment, any mathematical abstraction of a physical system used to predict the concentration of specific chemicals as a function of space and time subject to transport, intermedia transfer, storage, and degradation in the environment.  (EPA 1992)

environmental medium

Any one of the major categories of material found in the physical environment (e.g., surface water, ground water, soil, or air), and through which chemicals or pollutants can move.  (EPA 2004)
RELATED TERMS: medium (singular; plural, media)


Pattern of distribution of an agent, its derivatives or metabolites in an organism, system, compartment or (sub) population of concern as a result of transport, partitioning, transformation or degradation.  (IPCS/OECD 2004)

fate and transport

A description of how a chemical is carried through and changes in the environment.  (EPA 2004)

fate and transport analysis

The general process used to assess and predict the movement and behavior of chemicals in the environment.  (EPA 2004)

grab sample
  1. A single sample collected at a particular time and place that represents the composition of the water, air, or soil only at that time and place.  (EPA 2004)
  2. A single sample of soil or of water taken without regard to time or flow.  (EPA 2005e)

Interferents are anything that interfere with obtaining an accurate result for an assay (e.g., a PCR assay).  Interferents include reaction inhibitors, but are not limited to substances that directly interact with enzymes.  The source of interferents is the environmental or clinical sample matrix.  (EPA 2005f)

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limit of detection
The minimum concentration of a substance being analyzed test that has a 99 percent probability of being identified.  (EPA 2005b)
  1. The LOD is the lowest concentration of a pesticide residue or contaminant that can be identified and quantitatively measured in a specified food, agricultural commodity, or animal feed with an acceptable degree of certainty by a regulatory method of analysis. The LOD is considered synonymous with the limit of quantitation/quantification.  (FAO/WHO 1997)
limit of quantification


  1. LOQ is the point at which “measurements become quantitatively meaningful” (Taylor 1987).  It is the lowest pesticide residue that can be accurately quantitated in a reproducible fashion.  The LOQ can be defined in a number of ways, such as the background response plus ten times the standard deviation of the lowest measurable concentration, ten times the signal-to-noise ratio of the baseline noise, ten times the standard deviation of the lowest measurable concentration, etc.  In practice, the LOQ is the lowest fortification level that shows adequate recovery during the method validation process.  (EPA 1998b)
  2. The smallest amount of the pesticide that can be quantified by the analytical method.  (OECD 1997)
lower detection limit

The smallest signal above background noise an instrument can reliably detect.  (EPA 2005b)

  1. Periodic or continuous physical surveillance or testing to determine pollutant levels in various environmental media or in humans, plants, and animals.  (EPA 2004)
  2. Periodic or continuous surveillance or testing to determine the level of compliance with statutory requirements and/or pollutant levels in various media or in humans, plants, and animals.  (EPA 2005b, RAIS 2004)
  3. The act of conducting a planned series of observations or measurements of operational and/or critical limits to assess whether a control point is under control.  (KIWA 2004)
most probable number

An estimate of microbial density per unit volume of water sample, based on probability theory.  (EPA 2005b)

natural source

Non-manmade emission sources, including biological (biogenic sources such as plants) and geological sources (such as volcanoes), and windblown dust.  (EPA 2004)
RELATED TERMS: anthropogenic

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pathogen occurrence

A description of the frequency of appearance of a pathogen in a medium, including identification of peaks, average levels, frequency of detection, distribution, seasonal variation, and association with other temporal or spatial changes.  (ILSI 2000)

  1. Refers to the length of time a compound stays in the environment, once introduced.  A compound may persist for very short amounts of time (e.g., fractions of a second) or for long periods of time (e.g., hundreds of years).  (EPA 2004)
  2. Refers to the length of time a compound stays in the environment, once introduced. A compound may persist for less than a second or indefinitely.  (EPA 2005b)
  3. The ability of a pathogen to remain in a host or in the environment for extended periods of time.  (ILSI 2000)
  4. The quality of remaining for a long period of time (such as in the environment or the body).  Persistent chemicals (such as DDT and PCBs) are not easily broken down.  (NYDOH 1999)
  1. A measure of the reproducibility of a measured value under a given set of circumstances.  (EPA 1997a, EPA 2004)
  2. A measure of the reproducibility of the predictions of a model or repeated measurements, usually in terms of the standard deviation or other measures of variation among such predictions or measurements.  (FAO/WHO 2003b)
  3. The quality of being sharply defined or stated.  One measure of precision is the number of distinguishable alternatives from which a measurement wan selected, sometimes indicated by the number of significant digits in the measurement.  Another measure of precision is the standard error of measurement, the standard deviation of a series of replicate determinations of the same quantity.  See also measurement, problems with terminology. Statistics: Precision is defined as the inverse of the variance of a measurement or estimate. (Last 1983)
  4. The degree to which a measurement (e.g., the mean estimate of a treatment effect) is derived from a set of observations having small variation (i.e., close in magnitude to each other).  A narrow confidence interval indicates a more precise estimate of effect than a wide confidence interval.  A precise estimate is not necessarily an accurate one.  (NLM/NICHSR 2004)
  5. A measure of how consistently the result is determined by repeated determinations without reference to any “true” value.  (RAIS 2004, SRA 2004)
  6. Precision is a measure of how close an estimator is expected to be to the true value of a parameter.  Precision is usually expressed in terms of imprecision and related to the standard error of the estimator.  Less precision is reflected by a larger standard error.  (STEPS 1997)
    RELATED TERMS: parameter
presumptive count

An estimate of the number of bacteria of a specific group in a sample, as revealed by an initial screening test.  Requires further testing to be confirmed.  (NZ 2002)

  1. The degree to which a sample is, or samples are, characteristic of the whole medium, exposure, or dose for which the samples are being used to make inferences.  (EPA 1997a)
  2. The property of a sample (set of observations) that they are characteristic of the system from which they are a sample or which they are intended to represent, and thus appropriate to use as the basis for making inferences.  A representative sample is one that is free of unacceptably large bias with respect to a particular data quality objective.  (FAO/WHO 2003b)

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representative sample

A portion of material or water that is as nearly identical in content and consistency as possible to that in the larger body of material or water being sampled.  (EPA 2005b)


The degree of variation obtained when the same measurement is made with similar instruments and many operators.  (RAIS 2004, SRA 2004)

  1. The habitat in which an infectious agent normally lives, grows and multiplies; reservoirs include human reservoirs, animals reservoirs, and environmental reservoirs.  (CDC 2005)
  2. Any natural or artificial holding area used to store, regulate, or control water.  (CRCWQT 2002)
  3. Any biological or environmental milieu that supports the maintenance and/or growth of pathogenic organisms.  Such reservoirs can be the sources of both epidemic and endemic infections.  (ILSI 2000)
  1. A portion or piece of a whole.  A selected subset of a population or subset of whatever is being studied.  For example, in a study of people the sample is a number of people chosen from a larger population. An environmental sample (for example, a small amount of soil or water) might be collected to measure contamination in the environment at a specific location.  (ATSDR 2004)
  2.  A specimen of a whole entity small enough to involve no threat or damage to the whole; an aliquot.  A selected subset of a population; a sample may be random or nonrandom (haphazard); representative or nonrepresentative.  (CancerWeb 2005)
  3. A selected subset of a population.  A sample may be random or non-random and it may be representative or non-representative.  (CDC 2005)
  4. A sub-group of the population of interest that has been selected for study.  (ESOMAR 2001)
  5. A specimen that is taken from food and tested for the purpose of identifying a foodborne pathogen or various kinds of chemical contaminants in food.  (FDA 2001)
  6. Material collected from a source other than an animal or man for laboratory analysis (such as water sample or soil sample).  (MERREA 2005)
  7. The set of observational units (wafers, people, etc) whose properties our study is to observe.  When we select a sample by scientific randomization, we are more easily able to generalize our conclusions to the population of interest.  As opposed to population.  For a given characteristic, the collection of measurements that are actually observed.  (NIST/SEMATECH 2005b)
  8. A sample is a group of units selected from a larger group (the population).  By studying the sample it is hoped to draw valid conclusions about the larger group.  A sample is generally selected for study because the population is too large to study in its entirety.  The sample should be representative of the general population.  This is often best achieved by random sampling.  Also, before collecting the sample, it is important that the researcher carefully and completely defines the population, including a description of the members to be included.  (STEPS 1997)
    RELATED TERMS: contrast with population

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sampling distribution
  1. A probability distribution for a statistic.  (FAO/WHO 2003b)
  2. The distribution of a summary quantity or statistic.  (NIST/SEMATECH 2005b)
  3. The sampling distribution describes probabilities associated with a statistic when a random sample is drawn from a population.  The sampling distribution is the probability distribution or probability density function of the statistic.  Derivation of the sampling distribution is the first step in calculating a confidence interval or carrying out a hypothesis test for a parameter.  (STEPS 1997)
    RELATED TERMS: distribution, population, sample

Change in physiological status or in disease occurrence that conforms to a regular seasonal pattern.  (CDC 2005)

systematic error

A reproducible inaccuracy introduced by faulty equipment, calibration, or technique.  (RAIS 2004, SRA 2004)

temporal variability

The difference in contaminant concentrations observed in samples taken at different times.  (EPA 2004)

time-averaged exposure

The time-integrated exposure divided by the exposure duration.  An example is the daily average exposure of an individual to carbon monoxide.  (Also called time-weighted average exposure.)  (IPCS 2004)

time-integrated exposure

The integral of instantaneous exposures over the exposure duration.  An example is the area under a daily time profile of personal air monitor readings, with units of concentration multiplied by time.  (IPCS 2004)

time-integrated sample

Samples are collected over a period of time.  Only the total pollutant collected is measured, and so only the average concentration during the sampling period can be determined.  (EPA 2004)

time-trend study

Samples spaced in time to capture systematic temporal trends (e.g., a facility might change its production methods or products over time).  (EPA 2004)

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