A similar exposure group (SEG) is a group of workers expected to have the same general exposure to a hazard because they do similar tasks, with the same substances, in a similar environment. Employers use SEGs to plan exposure monitoring without measuring every worker, and to read health surveillance results across people who share an exposure. HSE guidance calls them “similarly exposed groups”; NIOSH’s 1977 sampling manual describes a “homogeneous risk group” whose members have a similar expected exposure risk.
How groups are formed
HSE’s HSG173, Monitoring strategies for toxic substances, explains that monitoring every worker can be prohibitively expensive, so monitoring strategies usually focus on groups of workers who do similar jobs in similar ways (Appendix 2, paragraph 5). Workers are grouped by careful observation of common factors:
- similarity of the tasks performed, not necessarily the same job;
- exposure to the same range of airborne contaminants;
- similarity of environment: process, exposure source and control measures.
A group has to hold up against the data. A wide spread in individual results shows considerable variation within the SEG, and the group should be sub-divided or workers reassigned. As a guide, a worker whose exposure is less than half or more than twice the group average should move to a more appropriate SEG (Appendix 2, paragraphs 6 to 8).
The NIOSH Occupational Exposure Sampling Strategy Manual adds a warning: groups built only from job title can misclassify workers, and anyone grouping workers for analysis should have actual knowledge of each worker’s exposure situation. Where no single maximum risk worker can be picked out, it describes randomly sampling the group so that there is a high probability of including at least one worker with high exposure.
Why it matters for employers
- Protecting everyone, not the average. In Great Britain, COSHH requires protection for all employees, so after group-based monitoring the employer needs to show that the conclusion drawn for one worker applies equally to the others in the group (HSG173, paragraph 81).
- Reading surveillance results. HSE’s guidance on occupational asthma says occupational health professionals should interpret surveillance results for individuals and for groups of similarly exposed workers, which can show the need to revise the risk assessment, review controls or move workers to other roles.
- Spotting trends early. The OSHA and NIOSH spirometry infosheet notes that surveillance can detect changes among groups of workers with similar exposures at a time when individual results may not be severe or noticeable. The infosheet makes this point about spirometry surveillance.
In MyC’s health surveillance software, surveillance is scheduled per worker from their exposure group, with due dates and expiry alerts.
Related terms
- Health surveillance: Health surveillance is a program of repeated health assessments for workers still exposed to a hazard after controls, to identify ill health caused by work.
- Spirometry surveillance: Spirometry surveillance is the repeated lung function testing of workers exposed to respiratory hazards, comparing results with each worker's own baseline.
- Employee exposure record: Employee exposure record, under OSHA 29 CFR 1910.1020, means workplace or biological monitoring, safety data sheets or chemical inventories on toxic exposures.
Go further
Sources
- HSG173: Monitoring strategies for toxic substances (HSE)
- DHEW (NIOSH) Publication 77-173: Occupational exposure sampling strategy manual (NIOSH)
- G402: Health surveillance for occupational asthma (HSE)
- DHHS (NIOSH) Publication 2011-133: Maximize your spirometry screening and surveillance resources (OSHA and NIOSH)