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| EPI6-1: Sources Of Exposure Data |
OBJECTIVES |
At the end of this session you should:
- know about the principal sources of occupational exposure data, and,
- where and how to access them..
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SOURCES OF EXPOSURE DATA:
Methods of external exposure measurement include personal interviews or self-administered questionnaires (completed either by the study participant or by a proxy respondent), diaries, observation, routine records, physical or chemical measurements on the environment, or physical or chemical measurements on the person.
Measurements on the person can relate either to exogenous exposure (e.g. airborne dust) or internal dose (for example, plasma cotinine); the other measurement options (for example, questionnaires) all relate to exogenous exposures. Traditionally, exposure to most non-biological risk factors (e.g. cigarette smoking) has been measured with questionnaires (either self-administered or interviewer-administered), and this approach has a long history of successful use in epidemiology. Questionnaires may be combined with environmental exposure measurements (for example, pollen counts, industrial hygiene surveys) to obtain a quantitative estimate of individual exposures.
More recently, there has been increasing emphasis on the use of molecular markers of internal dose (Schulte, 1993). However, questionnaires and environmental measurements have good validity and reproducibility with regard to current exposures and are likely to be superior to biological markers with respect to historical exposures. The emphasis should be on using "appropriate technology" to obtain the most practical and valid estimate of the etiologically relevant exposure.
Types of exposure data commonly used in occupational epidemiology studies
| Ever employed in the industry |
Yes/No results in a dichotomous group exposure variable |
| Duration of employment in the industry |
Years of service |
| Ordinally ranked jobs or tasks |
Jobs are high, medium or low exposed |
| Job-exposure matrices |
Based on representative exposure measurements for certain jobs/occupations for certain years |
| Quantified personal measurements |
Based on personal sampling or biological exposure measurements |
Example of job exposure matrix
| Job category |
1930 - 1935 |
1936 - 1945 |
1946 - 1965 |
1966 - 1975 |
| General area |
10.8 |
5.3 |
2.4 |
4.3 |
| Card operators |
13.3 |
6.5 |
2.9 |
5.3 |
| Clean-up |
18.1 |
8.8 |
4.0 |
7.2 |
| Raw fiber handling |
22.8 |
11.0 |
5.0 |
9.0 |
Asbestos concentrations (fibers/cc) in job categories in an asbestos textile plant (Source: Checkoway et al, 1989)
General Introduction to
Occupational Health: Occupational Hygiene,
Epidemiology & Biostatistics by Prof Jonny
Myers is licensed under a Creative
Commons Attribution-Noncommercial-Share Alike
2.5 South Africa License.
