From a traditional standpoint, most employers look at industrial hygiene projects as the front-end assessment of their workers’ exposures. This starts often as a “desktop” review of operations and then develops into an exposure assessment, or sampling plan, that then leads to the actual exposure evaluation using data from personal monitors and/or area monitors.
However, much of the time the evaluation and interpretation of the workplace sampling results is not the final step. If the results indicate that your workers’ exposures are below the applicable Occupational Exposure Limits (OELs), such as the Occupational Safety and Health Administration’s (OSHA) Permissible Exposure Limits (PELs), the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values (TLVs), or the National Institute of Occupational Safety And Health (NIOSH) Recommended Exposure Levels (RELs) then it is assumed your workers are not being exposed to harmful or dangerous levels of chemicals while at work. However, if the data indicates an exceedance of an OEL, then the next step is to reduce the exposure.
The graphic above shows the Hierarchy of Controls, well known in the safety and health field of work. As you look at it from top to bottom, the effectiveness of the control is reduced. Obviously, the elimination of the process or hazardous chemical (or hazardous noise level) would be the best way to eliminate or minimize the exposure, but sometimes it is not feasible due to quality requirements, product design, military specifications, or customer specifications.
If you can’t eliminate the hazard, then the feasibility of engineering controls should be considered next. Engineering controls are integrated into the process so that employees can perform the task safely and exposure is minimized. Engineering controls are often the sweet spot, or the middle bowl of porridge, when you consider costs versus effectiveness of the control. Additionally, engineering controls reduce the potential for exposure while reducing the responsibilities of the employee (i.e., correctly following a safe work procedure or properly wearing protective equipment).
Depending on your situation, engineering controls can be as simple as installing local exhaust around a process. But what kind is needed? Should you look into down draft tables, fume hoods, vacuum units integrated into the unit itself? All are viable options but one method may make more sense based on the application. Maybe you just need increased ventilation in the area. The more outdoor air you bring in and the more “contaminated” air you push out, the lower the potential exposure will be.
For example, with the requirements of OSHA’s silica standard, we are seeing more and more engineering controls become available that are designed to reduce employee’s exposure to respirable silica during routine tasks such as those involving concrete in construction. Many companies have begun using integrated vacuum units around smaller units that extract the concrete dust particles as they are being generated. Some are using hoses that apply water to the concrete as you cut, minimizing the potential for respirable dust. Whatever the application is, we can help identify a control or set of controls for your process. Many times, just one control is not enough to limit all the hazards for a process. You will have to consider all the hazards: chemical exposures, pinch points, electrical hazards, etc., that may require controls.
If engineering controls are not feasible, then administrative controls are next in the hierarchy to consider. Administrative controls focus on changing how employees perform the work or task. For instance, any time Task XYZ is performed, employees must follow a safe work practice which is intended to limit the exposure. Another type of exposure control may be rotation of personnel so one employee is not performing a task all day. The final control to consider is the use of personal protective equipment (PPE). PPE is effective at controlling exposure, but it does not eliminate or reduce the hazard – which is still present. The reduction in employee exposure will be affected by the proper (or improper) selection and wearing of the PPE. PPE can initially appear relatively inexpensive, but if you consider the repeat costs per employee for replacement of PPE over time, and employee training, it can be rather expensive. Both administrative controls and the use of PPE puts some of the responsibility back on the employee. If they forget to don their PPE or it doesn’t fit correctly, or if they forget to enact administrative controls, then the potential for the exposure is still very real.
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