Document the work tasks associ- ated with each job identified as need- ing exposure control improvements, noting any special circumstances surrounding the work tasks and work environ- ment which could affect worker exposure. Determine the potential sources of air contamina- tion associated with each work task which can result in worker exposure while performing the job. Table 1 can be used to summarize
Protecting worker health by controlling air contaminants is an important objective for metalcasters.
the source identification process for specific worker exposure situations. In a source assessment, you need to know the work task being conducted, portion of the work shift involved with the task, potential sources of exposure, and circumstances sur- rounding the exposure. Effective and reliable exposure
reduction requires the control mea- sures to directly address the sources of air contamination. Some of these potential sources will be apparent during exposure sampling activities in Action Item 1. However, in many cases where exposure sampling results are quantified in terms of time- weighted-average (TWA) exposures over the work shift, the key contribu- tors to the measured average concen- trations may not be apparent. Te manner in which air con- taminants from multiple sources are dispersed can complicate pinpointing the sources with the greatest impact on worker exposures. Because the concentrations of air contaminants are highest near the points of genera- tion, workers directly involved with those processes stand the highest risk of being exposed. As air contaminants migrate away from their sources, their concentrations decrease. Te con- tributions to worker exposures from background air contamination could ultimately comprise a significant por- tion of the worker’s total exposure. Several different air sampling
techniques can be employed as needed to locate air contaminant sources and assess their impacts on worker exposure levels as well as to provide a broad-based view of air quality in the facility: 1. Gathering
area samples concurrently with exposure samples. 2. Mapping
air contaminant concentrations
throughout an area. 3. Determining sources of air
contamination of exposures associated with job tasks.
ACTION ITEM 3: IDENTIFY CANDIDATE EXPOSURE CONTROL MEASURES FOR SPECIFIC JOB TASKS. Objectives:
• Identify candidate exposure control measures for each work task with identified sources of air contamination.
• Evaluate the potential use of any control measure option in light of the capabilities and limitations of the control method when applied to the situation at hand. Candidate exposure control
measures should be listed in Table 2 for each potential exposure source associated with a work task. Work practices associated with operational and maintenance tasks are critical to the performance of processes and their exposure controls and should be defined as exposure controls where they apply.
It is unlikely at the outset that
one could predict with any degree of accuracy which exposure control measure or combination of mea- sures could achieve compliance with exposure limits in a feasible manner for a specific work situation. Thus, it is advisable the initial process of identifying control options not be limited or prejudged. All of the control measure categories in the
hierarchy have general capabilities and limitations which should be considered.
ACTION ITEM 4: SELECT EXPOSURE CONTROL MEASURES FOR IMPLEMENTATION Objectives:
• Rate the expected performance of each candidate exposure control measure based on a set of perfor- mance factors as applied to each specific case.
• Select exposure control measures for implementation on the basis of the performance ratings. A Performance Factors Checklist is
presented in Table 3 as a tool to assist in the evaluation of expected exposure control performance. Tis set of factors relate specifically to the potential for a candidate control measure to perform effectively and reliably in controlling worker exposures to air contaminants. An implementation plan for exposure control measures should include the step of demonstrating the effectiveness and reliability of the exposure mea- sures chosen as part of the commis- sioning process. Protecting worker health by
controlling air contaminants is an important objective for metalcast- ers. Achieving that goal requires an understanding of exposures, sources and control options. Each of these elements requires careful attention to and evaluation of data in order to make effective decisions that pro- duce the intended result. Important opportunities to protect workers may be lost if assumptions are made about exposures based on misinter- pretation of scant data, if exposure sources are not correctly identified, or if suboptimal control strategies are used based on incomplete evaluation of performance. Te performance based approach to selecting exposure control methods presented here is a stepwise process designed to avoid these errors and achieve optimal worker protection.
Tis article is based on a paper (16-062) published in the 2016 AFS Transactions, “Controlling Exposures to Air Contaminants in Metalcasting-A Performance Based Approach.”
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