Principles of Industrial/Occupational Hygiene

2.1 Basic Concepts of Exposure and Risk

Industrial/occupational hygiene revolves around the understanding of exposure and risk. Exposure refers to the contact workers have with hazardous substances or conditions in the workplace, while risk is the probability that this exposure will result in harm.

Key Concepts:

• Exposure Assessment: Identifying and quantifying the extent to which workers are exposed to hazards.
• Dose-Response Relationship: The correlation between the level of exposure and the severity of the health effect.
• Risk Assessment: Evaluating the likelihood of adverse health outcomes due to exposure.

2.2 Routes of Exposure: Inhalation, Ingestion, Dermal, Injection

Hazardous substances can enter the body through several pathways, each posing unique health risks.

1. Inhalation: The most common route of workplace exposure. Workers can breathe in dust, fumes, vapors, and gases.
2. Ingestion: Contaminants may enter the body if workers eat, drink, or handle contaminated surfaces.
3. Dermal Exposure: Chemicals and other hazardous agents can be absorbed through the skin.
4. Injection: Less common, but it can occur through accidental punctures, especially in healthcare settings (e.g., needlestick injuries).

Note: The route of exposure greatly influences the severity of the health effects. Inhalation of toxic gases can cause immediate harm, while dermal exposure might result in long-term effects depending on the substance.

2.3 Toxicology and Health Effects of Workplace Hazards

Toxicology is the study of the adverse effects of chemicals on living organisms. In industrial hygiene, understanding toxicology is essential to assess the potential harm that workplace chemicals may cause to workers.

Key Toxicological Concepts:

• Acute vs. Chronic Exposure: Acute exposure refers to short-term, high-level exposure, while chronic exposure occurs over a long period at lower levels.
• Dose-Response Relationship: The higher the dose of a hazardous substance, the greater the effect on the body.
• Carcinogens, Mutagens, and Teratogens: Some workplace chemicals can cause cancer, genetic mutations, or birth defects.

Table 2.1: Examples of Workplace Toxicants and Their Health Effects

2.4 Threshold Limit Values (TLVs) and Permissible Exposure Limits (PELs)

Threshold Limit Values (TLVs) and Permissible Exposure Limits (PELs) are guidelines and regulations that specify the maximum level of exposure to hazardous substances that is considered safe over a workday.

• TLVs are guidelines recommended by the ACGIH (American Conference of Governmental Industrial Hygienists) to help occupational hygienists assess workplace conditions.
• PELs are enforceable standards set by regulatory bodies such as OSHA.

Both TLVs and PELs are essential for determining whether the concentration of a hazardous substance in a workplace exceeds safe limits.

Table 2.2: Example TLVs and PELs for Common Substances

Practical Applications: Risk Assessment in the Workplace

Occupational hygienists must apply principles of exposure and toxicology to perform risk assessments. For instance, if workers in a manufacturing facility are exposed to benzene, an occupational hygienist would:

1. Measure the airborne concentration of benzene.
2. Compare the results with TLVs and PELs.
3. Recommend control measures such as ventilation or PPE if levels exceed safe limits.

Listing: Steps in a Basic Risk Assessment

1. Identify the hazard: Determine if a hazardous substance or condition is present.
2. Assess exposure: Measure the level and duration of exposure to the hazard.
3. Evaluate risk: Analyze the likelihood and severity of harm.
4. Implement controls: Apply control measures to mitigate the risk.

Review Questions:

1. What is the difference between TLVs and PELs, and why are they important in occupational hygiene?
2. Describe the four main routes of exposure in the workplace.
3. Explain the concept of the dose-response relationship and its significance in toxicology.
4. What is the formula for assessing risk, and how does it relate to occupational hygiene?

Case Study: Inhalation Hazards in a Chemical Plant

In a chemical manufacturing plant, workers are exposed to formaldehyde fumes. An occupational hygienist performs air sampling and finds that the concentration exceeds the recommended TLV. Immediate measures are taken:

• Engineering controls such as local exhaust ventilation are installed.
• PPE (e.g., respirators) are provided until permanent controls are in place.
• Medical surveillance is initiated to monitor the health of workers who may have been affected.

Further Reading:

• Occupational Exposure Limits by ACGIH
• OSHA’s Air Contaminants Standard (29 CFR 1910.1000)
• Fundamentals of Industrial Hygiene by Barbara A. Plog

This chapter covers foundational principles of industrial/occupational hygiene, focusing on the basic concepts of exposure, routes of exposure, toxicology, and essential occupational exposure limits like TLVs and PELs.