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Environmental and Occupational Health


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Exposure pathway
The physical course a pollutant takes from the source to a subject.
Exposure Route
Way a substance enters the body
Exposure assessment
The study of distribution of determinants of substances or factors affecting human health:
3 components of exposure assessment
1)design of the study
2)data collection
3)interpretation of the data
is referred to the exposure after uptake of the body.
A substance or factor affecting human health (adversely or beneficially). In Occupational or Environmental Epidemiology- generally contact with a substance through and environmental medium and surface of the human body.
Source-receptor models
Include the routes and pathways of exposure and a helpful in understanding how people are exposed.
3 possible exposure routes for humans
1. inhalation through respiratory system
2. ingestion through gastrointestinal system
3. absorption through the skin.
3 dimensions of exposure
1. Duration (ie, hours or days)
2. Concentration
3. Frequency (ie, times per week)
[can be used as an exposure index in an epidemiological stdy. i.e., exposures that cause acute effects, the short term concentration is generally the most relevant exposure index.] NOTE: these can be combined such as duration x concentration = cumulative exposure.
Within and between subject exposure variability
Exposure generally varies from day to day for any subject and from subject to subject.
Can be estimated with repeated exposure measurements
2 main approaches to obtaining exposure estimate(s) for a population
1. Individual (ie every member of a population is monitored either once or repeatedly.
2. Exposure grouping population is split into smaller subpopulations or "exposure groups" based on determinants of exposure & group or ecological estimates are obtained for each exposure group.
Pros & Cons of expert and self-assessment methods
Pro: easiest and cheapest, generally.
Con: Can suffer due to lack of objectivity and knowledge, and may introduce bias.
More objective way to assess exposure
- Measurement.
ex: Levels of outdoor pollution assessed by ambient air monitors.
ex: Levels of substance into body can be estimated by biomonitoring.
Deterministic Modeling
One of two types of modeling - in which the models describe the relationship between variables mathematically on the basis of knowledge of the physical, chemical, and or biological mechanisms governing these relationships.
Stochastic Modeling
One of two types of modeling - statistical relationships are modeled between variables.
The degree to which a measurement or an estimate represents the true value of what is being measured
Deviation of results or inferences from the truth, or processes leading to such deviation; any trend in the design, collection, analysis, interpretation, publication or review of data that can lead to conclusions that are systematically different from the truth.
Limit of Detection (LOD)
The minimum concentration of an analyte, in a given matrix and with a specific method, that statistically is significantly greater than zero, that is, the lowest concentration that can be measured with a certain degree of confidence
The degree of variability in a measurement or estimate, estimated, for example, by the standard error of measurements or the standard deviation in a series of replicate measures
The ability of a study to demonstrate statistically significant effects, which is determined by a number of factors including study design, magnitude of effect, and sample size.
The degree of stability exhibited when a mesurement is repeated under identical conditions - the degree to which the results obtaind by measurement procedure can be replicated.
A test or measurement is repeatable if the results are identical or closely similar each time it is conducted
A procedure is said to be robust if it is not very sensitive to departures from assumptions or variations in the conditions or practices under which it was set up
Index of the performance of a diagnostic tool, for ex, for questionnaires: the proportion of truly exposed people in the population who are identified as exposed by the questionnaire.
Index of the performance of a diagnostic tool, for ex, for questionnaires: teh proportion of truly non-exposed people in the population who are identified as non-exposed by the questionnaire.
An expression of the degree to which a measurement measures what it purports to measure.

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