Monday, June 17th, 2019
Exposure Groups can simplify Chemical Exposure Monitoring

Similar Exposure Groups can simplify Chemical Exposure Monitoring

Do you know how many individual chemicals workers are exposed to in your workplace? How do you monitor who is exposed to what? What about exposures that are seasonal or change with maintenance activities?

Collecting data and identifying hazards on employees can be time intensive and costly. Using Similar Exposure Groups enables industrial hygienists to design monitoring programs that enhance safety while offering the best possible return on investment.

What is a similar exposure group?

A Similar Exposure Group (SEG) is a group of workers who have common risks and similar exposure profiles. SEGs are created based on knowledge of employee activities, assuming that similar tasks with similar regularity will result in similar exposures (qualitative approach), or based on exposure measurements (quantitative).

What advantage is there in establishing SEGs?

Risk assessments are fundamental to any OHS program. Grouping workers into SEGs avoids having to assess every individual position. If the members of a large work group do a similar job and are exposed to similar risks, data from a small sample of workers can be used to predict the exposure of the whole group, saving significant resources.

Creating SEGs can minimize the variability of exposure monitoring data. For highly dynamic work sites where activities and related exposures may vary significantly from day-to-day, SEGs should be categorized by the tasks or activities being performed. Categorizing SEGs by process, task, environmental agent and engineering controls is often preferred over defining SEGs by title and/or occupation.

How do I establish SEGs to start the process?

Using an integrated approach that combines qualitative data (through observation) with quantitative data (through sampling) is considered best practice.  Begin by determining which employees conduct similar tasks with common exposure risks, then validate with direct exposure monitoring and adjust the SEGs as needed based on the results. Direct observation of the work environment and participation of employees is highly valuable.

Observation involves grouping work activity according to the task, job description, the process, and exposure to any agent in the work environment and control measures applied. Workers may be assigned to more than one SEG.

Look for workers who:

  • Perform similar types of tasks at a similar frequency.
  • Use the same materials or processes to complete tasks.
  • Perform their tasks using the same procedures.
  • Perform job tasks near the same emission source.

Since exposures can alter with differences in shifts, seasons, or locations in the same facility sampling data is required to support observational data. Sampling data can include noise levels, respirable dust levels and exposure to hazardous substances.

Once sufficient data is collected, statistical analysis can be carried out to confirm that the group does represent a SEG.

What is an Example of a SEG?

  • Employees spray pesticides on flower beds at city parks. This chemical is a known respiratory hazard. An SEG based on a list of workers who perform this task would be created for the task of spraying flower beds. .
  • Jackhammering exposes workers to a noise hazard. To establish a overarching control for this particular task, you would set up a SEG for jackhammering including locations were the work is performed and tasks that involve jackhammering.

What will this information be used for?

SEGs can be used to collect and classify data and analyse for health trends that can be associated to a group of workers. This information can help employers adjust controls for a group of workers if necessary.

What is the value of SEGs?

Using SEGs allows you to use data from a small sample of the exposed population to predict the exposures of the wider population. This information allows you to allocate and prioritize exposure monitoring and control efforts. The information can also be used to compare with other similar SEG at other workplaces.

A systematic exposure monitoring program provides significant savings in resources: fewer samples are collected and a range of statistical tools can evaluate the collected data. 

The purpose of a monitoring program is to identify unacceptable exposures as soon as possible so that further controls are expedited. A balance may need to be struck between investing in more sampling, or controlling the exposure.  

Creation of the SEG is important to provide accurate risk assessments. Another benefit that often comes from the creation of SEGs is that potential exposures that might be overlooked otherwise.  


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