Page 28 - OHS, May 2022

INDUSTRIAL HYGIENE
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e industrial hygiene responsibilities face.
YBY BETH ANGUS
ou did it! A whole exposure assessment from start to fin- ish. You’ve received the sampling results from the labo- ratory, notified your employees and submitted a correc- tive action plan based on the results to your supervisor.
You’ve checked it off your list once and for all—but are you done? Maybe you’ve found a treasure trove of sampling data: multiple studies over the years, collected by your predecessor, catalogued into tidy exposure groups and archived alongside detailed qualitative assessments. Let it be? Or should you take another look to make sure your employees are as safe as they can
be and your company is OSHA compliant?
You lean back in your desk chair, considering the numbers
in front of you, and questions pop up in the back of your mind: is this it? Is this the true picture of the exposures in my facility? What if I need to sample again? How will I know?
Depending on the hazard you monitored, your reassessment schedule may be dictated by a regulatory schedule. OSHA has sam- pling frequency requirements for several chemicals, including sili- ca, hexavalent chromium, lead and formaldehyde. For most agents with prescribed schedules, OSHA has the following requirements:
■ Every three months for exposures greater than the Permissible Exposure Limit
■ Every six months for exposures between the Action Level and the Permissible Exposure Limit
But what if you’re looking at exposures outside of OSHA’s limited list of specific standards? How do you decide if you need to reassess?
Determining when to reassess employee exposures is a challenge that any health and safety professional with industrial hygiene responsibilities faces. Exposure assessments must be updated as the work processes evolve (e.g., operational changes, new equipment is adopted, etc.), materials change and as employees turn over or adapt to new working conditions. Health and safety professionals have the responsibility to decide what conditions trigger a reassessment.
Quantitative Data
One of the easiest methods for determining when and what exposures to re-evaluate is to develop a matrix based on your already existing exposure results. The American Industrial Hygiene Association (AIHA) recommends the following matrix in their “A Strategy for Assessing and Managing Occupational Exposures,” 4th Edition:
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Periodic monitoring strategies, such as this one, can be used to identify subtle changes in exposures, such as variation between the seasons or as systems undergo routine maintenance or updates. These exposure frequencies may also be adjusted based on properties of a specific agent. For instance, you may choose to monitor exposures to a carcinogen used in your process more frequently, even if exposures are routinely less than 25 percent of the exposure limit you are comparing it to. Or exposures may simply be so infrequent that you choose to evaluate the exposure every time a task occurs, regardless of the results.
Changes in the Workplace: A Cause for Reevaluation
Other triggers for reevaluation could be changes to the physical workplace itself. Minor changes to equipment, an increase or decrease in production, or a modification to the process can all result in changes to the exposure profile. Your employee worker population can be a factor; new employees may have greater exposures than more experienced ones based on their work practices. Sometimes an organizational change can influence how your employees interact with the hazard. A significant change to the workday itself, say switching from 8-hour to 12-hour shifts or a period of mandatory overtime, can also have an impact. Even if the exposure measurement itself doesn’t change, you may decide to use a more conservative exposure limit to account for a decrease in recovery time.
As a result of your previous sampling results, you may have decided to implement some new engineering or work practice controls. Reevaluating exposures once controls are in place can demonstrate if the measures are effective or if more needs to be done to reduce potential exposures.
You may also choose to reevaluate exposures when existing control systems are modified, or a new system is installed. Additionally, as engineering controls age, they may not be as effective at minimizing exposures, especially in the absence of a preventative maintenance program. Even normal wear and tear to mechanical components in your controls, including fans, ducting or seals, can result in a change to exposures. Repeating exposure monitoring can help determine if there’s been a change in control efficacy.
Changes to the Hazard
As processes change and evolve, companies may look to change materials to positively impact performance or profits. Any new materials may have different health effects or may interact with other exposures to change how we consider them. Or a switch to a new vendor leads to a change in the material blend, and the ratio of chemicals is enough to change exposures.
Changes to our knowledge of the hazards can also have an impact on the exposure profile. New health information is
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Exposure Measurement
Frequency
Greater than Exposure Limit
Annually
50-100 percent of Exposure Limit
Every six months
25-50 percent of Exposure Limit
Every nine months
Less than 25 percent of Exposure Limit
Every two years
24 Occupational Health & Safety | MAY 2022
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