5.1 Hierarchy of Controls: Elimination, Substitution, Engineering, Administrative, PPE
The hierarchy of controls is a widely accepted framework for controlling workplace hazards. It prioritizes control methods based on their effectiveness, starting with the most effective and ending with the least.
Hierarchy of Controls:
- Elimination: Completely removing the hazard from the workplace.
- Substitution: Replacing hazardous materials or processes with safer alternatives.
- Engineering Controls: Physical modifications to the workplace or equipment to reduce exposure (e.g., ventilation, barriers).
- Administrative Controls: Changes to work policies, procedures, or schedules to limit exposure (e.g., rotating tasks, training).
- Personal Protective Equipment (PPE): Using equipment like gloves, masks, or earplugs to reduce exposure.
Listing: Key Principles of the Hierarchy of Controls
- Elimination and substitution are the most effective control methods because they remove or replace hazards.
- Engineering controls reduce exposure without relying on worker behavior.
- Administrative controls and PPE are the least effective because they depend on worker compliance and proper usage.
Table 5.1: Example Control Measures for Common Hazards
| Hazard Type | Elimination/Substitution | Engineering Controls | Administrative Controls | PPE |
|---|---|---|---|---|
| Chemical Exposure | Use non-toxic alternatives | Local exhaust ventilation | Training on safe handling | Respirators, gloves |
| Noise | Use quieter machinery | Sound barriers, dampening | Limit exposure time, job rotation | Earplugs, earmuffs |
| Biological Hazards | Use disinfectants instead of biological agents | Isolation of infectious areas | Hygiene protocols | Masks, gowns, face shields |
5.2 Engineering Controls: Ventilation Systems, Isolation, and Enclosures
Engineering controls are designed to isolate workers from hazards or modify the work environment to reduce exposure. These controls are effective because they don’t depend on workers’ actions for success.
Ventilation Systems:
- Local Exhaust Ventilation (LEV): Captures contaminants at the source and removes them from the air before they can disperse throughout the workplace. Commonly used in laboratories or areas with high concentrations of fumes or dust.
- Dilution Ventilation: Reduces the concentration of airborne contaminants by introducing fresh air into the workspace, often used in larger areas where contaminants are less concentrated.
Isolation: Physical barriers, such as enclosures or partitions, can separate workers from hazardous environments or equipment.
Enclosures: Complete enclosures can contain hazardous materials, such as chemical fume hoods in laboratories.
Note: Engineering controls are often more cost-effective in the long run compared to administrative controls or PPE because they provide ongoing protection once installed.
5.3 Personal Protective Equipment (PPE): Selection, Use, and Limitations
Personal protective equipment (PPE) serves as the last line of defense in the hierarchy of controls. While it can be effective in protecting workers, it should not be the primary method of control, as it relies on correct usage and maintenance.
Selection of PPE:
- Gloves: Protection from chemicals, biological agents, or sharp objects.
- Respirators: Used to protect against inhalation of harmful dusts, fumes, or gases.
- Ear Protection: Earplugs or earmuffs to protect against noise-induced hearing loss.
- Protective Clothing: Gowns, coveralls, or aprons to prevent contact with hazardous substances.
Limitations of PPE:
- PPE only protects the individual wearing it, not the overall environment.
- It must be worn correctly and consistently to be effective.
- Regular maintenance and replacement are required to ensure its effectiveness.
Table 5.2: Examples of PPE and Associated Hazards
| PPE Type | Hazard Type | Limitations |
|---|---|---|
| Respirators | Inhalation of toxic gases | Must be properly fitted; limited duration |
| Gloves | Chemical/biological exposure | Can tear, may reduce dexterity |
| Earplugs/Earmuffs | Excessive noise | Must be worn correctly to ensure full protection |
| Safety Goggles | Chemical splashes, dust | Can fog up or reduce visibility |
5.4 Administrative Controls: Policies, Procedures, and Training
Administrative controls focus on changing how work is performed rather than addressing the hazard itself. These controls are useful when elimination, substitution, or engineering controls are not feasible or sufficient on their own.
Examples of Administrative Controls:
- Workplace Policies: Developing and enforcing rules about safe work practices (e.g., limiting the time workers spend in hazardous areas).
- Work Schedules: Rotating workers to minimize exposure to hazards, such as rotating tasks to avoid repetitive strain injuries.
- Training Programs: Ensuring that all workers understand the hazards they may face and know how to use control measures, such as PPE or emergency procedures.
Note: Administrative controls should be regularly reviewed and updated as conditions change in the workplace or new hazards emerge.
5.5 Ergonomic Interventions and Workplace Design
Ergonomic interventions focus on designing the workplace to fit workers’ physical needs, thereby reducing the risk of musculoskeletal disorders (MSDs) caused by repetitive tasks, awkward postures, or overexertion.
Examples of Ergonomic Controls:
- Workstation Design: Adjusting the height of desks or chairs to reduce strain on the back and neck.
- Tool Design: Using tools with ergonomic handles to minimize grip force and repetitive motions.
- Work Rotation: Alternating between tasks to avoid overuse of the same muscle groups.
Listing: Key Ergonomic Considerations
- Posture: Workstations should promote neutral postures to avoid musculoskeletal strain.
- Repetition: Repetitive tasks should be minimized or broken up with rest or alternate activities.
- Force: Tools and equipment should be designed to minimize the force needed to complete tasks.
Practical Applications: Implementing Control Measures in a Chemical Plant
In a chemical manufacturing facility, workers are exposed to hazardous fumes and ergonomic hazards from repetitive motions. An occupational hygienist implements the following control measures:
- Elimination: Replacing a highly toxic chemical with a safer alternative.
- Engineering Control: Installing a local exhaust ventilation system to capture fumes at the source.
- Administrative Control: Implementing a rotation schedule to reduce worker exposure time to both chemical fumes and repetitive tasks.
- PPE: Providing respirators and protective gloves for tasks involving potential exposure to remaining chemical hazards.
As a result, air quality improves, and workers report less fatigue from repetitive tasks.
Review Questions:
- What are the five levels of the hierarchy of controls, and why is elimination the most effective?
- Explain how local exhaust ventilation works and its importance in controlling chemical exposures.
- What are the limitations of PPE, and why should it not be relied on as the primary method of control?
- Provide examples of administrative controls and their role in reducing worker exposure to hazards.
Further Reading:
- Ventilation for Contaminant Control by ACGIH
- OSHA’s Personal Protective Equipment (PPE) Standards
- Ergonomics in the Workplace by NIOSH
This chapter provides a comprehensive understanding of the various control measures used in industrial and occupational hygiene. It emphasizes the hierarchy of controls, focusing on engineering and administrative controls, PPE, and ergonomic interventions to ensure worker safety and well-being.