Hygiene

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Course Learning Outcomes for Unit VII

Upon completion of this unit, students should be able to:

7. Evaluate types of hazard controls. 7.1 Discuss the use of elimination/substitution for controlling occupational hazards. 7.2 Discuss the use of engineering controls for occupational hazards. 7.3 Discuss the use of administrative controls for occupational hazards.

Reading Assignment

To access the following resources, click on the links below:

Occupational Safety and Health Administration. (n.d.). Chemical hazards and toxic substances: Controlling exposures. Retrieved from https://www.osha.gov/SLTC/hazardoustoxicsubstances/control.html

Occupational Safety and Health Administration. (n.d.). Basic hazard awareness [PowerPoint slides]. Retrieved from https://www.osha.gov/sites/default/files/2018-11/fy10_sh-20839- 10_basic_hazard_awareness.pptx

Occupational Safety and Health Administration. (n.d.). OSHA technical manual—Section III: Chapter 3 Ventilation Investigation. Retrieved from https://www.osha.gov/dts/osta/otm/otm_iii/otm_iii_3.html

Unit Lesson

The last of the four tenets of industrial hygiene that we will study is control. The first three tenets— anticipation, recognition, and evaluation—identify hazards and the level of risk for each hazard. Controls then are used to reduce the risk associated with the hazards to an acceptable level. Risk assessment is a valuable tool in prioritizing expenditures for control methods. Controls will be implemented first for hazards with the

highest level of risk.

The Occupational Safety and Health Administration (OSHA) established a hierarchy of controls for occupational hazards. It illustrates OSHA’s preferred approach for hazard control. As summarized in the diagram below, the Hierarchy of Controls includes elimination/substitution, engineering controls, administrative controls (including work practices), and personal protective equipment (PPE).

In looking at protection from occupational hazards, the most effective method is to prevent an exposure from occurring in the first place; however, this is not always possible in occupational settings. Therefore, the next

Course/Unit Learning Outcomes

Learning Activity

7.1 Unit VII Lesson Article: “Basic hazard awareness [PowerPoint slides]” Unit VII Assessment

7.2 Unit VII Lesson Unit VII Assessment

7.3 Unit VII Lesson Article: “Basic hazard awareness [PowerPoint slides]” Unit VII Assessment

UNIT VII STUDY GUIDE

Hazard Controls

https://www.osha.gov/SLTC/hazardoustoxicsubstances/control.html

https://www.osha.gov/sites/default/files/2018-11/fy10_sh-20839-10_basic_hazard_awareness.pptx

https://www.osha.gov/dts/osta/otm/otm_iii/otm_iii_3.html

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Title priority is to prevent harm to exposed individuals. Finally, if harm occurs, the priority is to limit the harm as much as possible. OSHA’s Hierarchy of Controls is designed to meet these priorities.

The first control method in OSHA’s Hierarchy of Controls is elimination/substitution. This control method is always the most effective and preferred method because it prevents the exposure from occurring in the first place. If you remove a specific hazard completely from a workplace, no one can be exposed to that hazard. For example, if a facility is using a solution containing styrene to clean parts, there is a health risk from exposure to the styrene, both through inhalation and dermal exposure.

If the facility determined that the cleaning could be performed using only water, the exposure to styrene would be completely eliminated for that particular task. This approach sounds simple but is much more complicated in practice. If, for example, a solvent solution is needed to clean a part, water would not be effective. Therefore, this approach would change to evaluating other chemicals effective in performing the same task and choosing one that would produce

the lowest risk to employees. In the example above, some employers have changed from a solvent like styrene to a solvent like acetone. Acetone has a lower toxicity than styrene, so health risks will be reduced. Nevertheless, reducing a health risk may increase other risks. Acetone is more flammable than styrene, so substituting acetone may reduce health risks but increase the risk of a fire. Of course, there may be situations where specifications require the use of a specific chemical and thus the use of elimination/substitution is untenable.

If the hazard cannot be eliminated from the workplace, residual risks will remain. Additional controls will be designed to reduce the risk associated with the hazard. In evaluating the use of control methods, one must always ask what level of residual risk will be acceptable. Once the acceptable level of residual risk has been determined, the rest of the controls in OSHA’s Hierarchy of Controls can be applied, in order of preference, until the residual risk has been lowered to the acceptable level.

The acceptable level of residual risk is a debated topic. Certainly, for exposures to chemical and physical hazards that industrial hygienists evaluate, the established OSHA permissible exposure limits (PELs) represent what should be accepted as residual risks. One would think exposures below the OSHA PELs are either safe or at least below a level where the residual risk would be significant, but this is not always true. OSHA should consider technological and economic feasibility in addition to risk assessments when they establish PELs. In some instances, exposures at the established PELs continue to carry significant risks of morbidity and mortality, even by OSHA’s definition of significant risk.

OSHA has historically used a residual risk of 1 in 1,000 as being significant; this is based on a Supreme Court decision in 1980. Any residual risk exceeding that level is considered significant by OSHA. In many cases, OSHA has estimated the residual risk to exceed this level for lifetime exposures at new PELs. For example, OSHA recently released new PELs for crystalline silica. Under the old PELs, OSHA estimated the risk of death from silicosis to be 11:1,000 in general industry and 17:1,000 in the construction industry. For exposures at the newly published PEL, OSHA estimates the risk of death from silicosis at 7:1,000 for both general industry and construction. At the new action level, OSHA estimates the risk of death from silicosis at 4:1,000 for both general industry and construction. Significant residual risk of death is also present for exposures at the PEL for both asbestos and hexavalent chromium. For this reason, many employers may choose to use more stringent control methods than those required by OSHA.

Basic hazard awareness diagram (Occupational Safety and Health Administration [OSHA], n.d.)

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Title

The next preferred control method in the Hierarchy of Controls is engineering controls. Because it may be difficult to eliminate a hazard or substitute a less hazardous chemical for a process, engineering controls are the most commonly used control method for occupational settings. Many different engineering controls are used. In some cases, the process can be isolated or enclosed to separate the worker from the hazard. An example would be to place a machining process inside an enclosure with a lid that opens and closes and to provide automatic sprayers that apply metalworking fluids. The employee opens the door to the machine, removes the part, and places another part inside the machine. The metalworking fluid is not applied, and the machining process will not start until the door is closed. Industrial hygiene evaluations have shown that exposures to metalworking fluids still occur because the hazard is still present, but the exposures are lower than they would be with an open process.

Engineering controls can also address noise hazards, for example, in using enclosure and isolation methods to reduce noise hazard risk. The enclosures, however, will require the use of specific materials. As discussed in Unit VI, noise propagates through air as a wave, and noise hazards from a single source can be present at different frequencies. Noise-deadening materials are typically effective at reducing dB levels based on frequencies. The use of the octave band filter with a sound level meter, as discussed in Unit VI, can provide the information necessary to choose materials for a noise enclosure that will be effective in reducing noise levels from a specific source.

Another engineering control involves wet methods. These methods are specified in some regulations such as OSHA’s asbestos in construction regulation. Because significant residual risk remains for exposures at the PEL, OSHA has specified wet methods (and respiratory protection) for some tasks involving asbestos removal, even if exposures have been shown to be below the PEL. Wet methods are designed to reduce, but not completely eliminate, the concentration of an aerosol hazard in the air.

Ventilation is one of the most common engineering controls. Two types of ventilation can reduce exposure to hazards: general dilution ventilation and local exhaust ventilation (LEV) systems. The nature of a hazard and the risk associated with that hazard, will help determine the ventilation system with the best protection.

General dilution ventilation systems merely blow fresh air into a work area to dilute the concentration of an air hazard. A typical dilution ventilation system in a workplace consists of a fan or fans in the ceiling or through an exterior wall. The fans blow either fresh air into the work area or move air from inside the work area to outside the building. Fresh air in the latter case will come through other openings in the building. The use of portable fans placed in the work area can also be considered dilution ventilation, though they are not typically as effective. An example using the metalworking operation would be to place large fans in the ceiling above the machines and blow fresh air through the area, reducing the employees’ exposure to metalworking fluids. In many cases, the use of dilution ventilation is adequate to reduce exposures to an acceptable risk level.

LEV systems collect the air at the source and move it somewhere else through duct systems. Where the contaminated air is moved depends on how it will be treated. Sometimes the air is simply discharged to the outside air. Other contaminants require some type of treatment, such as filtration or disintegration. Whether the air can be released directly to the outside air or needs some type of collection or treatment will depend on the specific compound. Some chemicals are too toxic to release into the outside air directly, and some states have regulations controlling the release of specific chemicals from a facility. An example using the metalworking fluid operation is to place an LEV above or near the machine to collect and filter out aerosols associated with the fluids. This type of LEV is commonly called a smog hog by industry. Another example of using an LEV would be laboratory fume hoods commonly found in laboratory settings. Although called fume hoods, they typically are used for gases and vapors, not fumes.

The next level of controls on OSHA’s Hierarchy of Controls is administrative and work practice controls. These do not provide the level of controls that engineering controls can, but may further reduce residual risk if the engineering controls cannot reduce the residual risk to an acceptable level. Administrative controls can reduce risk by limiting the amount of time an employee spends in a certain area. Let’s say a certain task requires work near a machine that produces constant noise levels exceeding 100 dBA. The first approach would be to apply some type of sound barrier to reduce the exposure. If this was not possible, employees could be rotated into and out of the area to limit their total exposure to a point below the OSHA PEL and action level.

Work practice controls could also be used to evaluate the standard operating procedures used by employees, and then work practices could be changed to reduce exposures. For example, if a job has been performed

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Title during the first work shift, and there is an unacceptable risk of heat illness in the summer, the work could be moved to the third shift during periods of lower temperatures to reduce the risk.

Reference

Occupational Safety and Health Administration. (n.d.). Basic hazard awareness [PowerPoint slides]. Retrieved from https://www.osha.gov/dte/grant_materials/fy10/sh-20839- 10/basic_hazard_awareness.pptx