1 Establishing Similar Exposure Groups Lecture 4

2 Why? Not needed for OSHA compliance sampling So why do it?  workplaces can employ a few up to thousands of workers  magnitude of exposure to exposure agents varies from minute ‑ to ‑ minute, hour ‑ to-hour and day ‑ to ‑ day Represents best practice

3 The goal….. To assess the exposures and occupational health risks for all workers to all environmental agents on all days

4 The challenge…… Is to do it accurately and efficiently, despite the diversity of exposures across workers and across time.

5 The how to….. One strategy for meeting these challenges is to assemble workers, thought to have similar exposures, into a group Qualitative or quantitative characterization of the exposure of one or a few in the group is then considered "representative" of the exposures of everyone in the group

6 The benefit…. Stratification of workers into "similar exposure groups" (SEGs) allows limited resources to be better used to characterize the many exposures that may be present in a particular workplace over different periods of time.

7 The definition….. Similar exposure group (SEG) are groups of workers having the same general exposure profile because of the similarity and frequency of the tasks that they perform, the materials and processes with which they work, and the similarity of the way that they perform the tasks

8 Two general methodologies for defining a SEG Observational approach  More traditional, workers are assigned to SEG based on an examination of the activities they perform and a judgment about the expected similarity of their exposures  Exposure monitoring results are not needed.

9 Two general methodologies for defining a SEG Operational and sampling approach  Workers are initially grouped by activities they perform and or a judgment about the expected similarity of their exposures, then  Exposures of many workers are measured and used to refine the assignment of individual workers to a SEG based upon statistical analysis of their exposure data.

10 A “workable approach” to develop and use SEGs Use the observational approach as the primary, default approach to defining SEGs Assess exposures for the SEGs formed by observation

11 A “workable approach” to develop and use SEGs Identify critical SEGs for which the consequences of misclassifying an individual worker's exposure are very severe Use exposure monitoring and statistical analysis to check and refine critical SEGs using the sampling approach

12 Establishing SEGs by Observation Established by using the information gathered during the basic characterization of the workplace, workforce and exposure agent(s). Observational approach allows the IH to make initial judgments about exposures to form SEGs and prioritize them for further action  exposure monitoring or  control

13 Establishing SEGs by Observation SEGs established by observation are generally described by….  Process  Job  Task  Exposure agent

14 Hierarchical strategies for establishing SEGs by observation Classifying by process and exposure agent Classifying by process, exposure agent, and job and/or task Classifying work teams Classifying non ‑ repetitive work

15 Establishing SEGs by Sampling Measured exposure values are used to classify workers into SEGs Workers grouped with a given amount of similarity and a given amount of confidence Has the advantage of objectivity Can be more accurate than classification by observation

16 Establishing SEGs by Sampling Good idea but……  large number of random measurements are required and multiple measurements must be made on individual workers  Very seldom is sufficient exposure data available  Costly in $ and personnel to collect sufficient data

17 Some summary thoughts….. SEGs are needed to efficiently assess the exposures for each and every worker, each and every day SEGs are generally described by the following determinants  Process  Job  Task  Environmental Agent

18 Some summary thoughts….. An exposure assessment program will be forced by problem scope and limited resources to group workers into SEGs and prioritizing those SEGs for further information gathering or health hazard control In doing so the industrial hygienist will accept the risk of possibly misclassifying some workers.

19 Some summary thoughts….. As the exposure assessment and management system matures the IH can identify those SEGs where the risk posed by individual misclassification is a concern Critical SEGs can be targeted for more extensive exposure monitoring using statistical analysis of the exposure data to check or re ‑ assign individuals as necessary

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