Industrial Hygiene and Toxic Substances

Industrial Hygiene: Overview and Importance

  • Definition: Industrial hygiene is the science of anticipating, recognizing, evaluating, and controlling workplace conditions that may cause workers' sickness and injury.
  • Application: Toxic chemicals can be safely used if the principles of industrial hygiene are appropriately applied.

Learning Outcomes

At the end of the lecture, students should be able to understand:

  1. Define toxic substances, entry points, and effects.
  2. Identify contaminants and effects of airborne toxics and carcinogens.
  3. Understand ventilation and the "sick-building syndrome".
  4. Recognize confined space hazards.
  5. Assess hazard recognition and evaluation.
  6. Recall OSHA standards.

Toxic Substances

  • Definition: Toxic substances are those that have a negative effect on the health of a person or animal.
  • Types of Toxic Substances:
    • Irritants: Cause inflammation or discomfort.
    • Examples: Ammonia (NH3) and chlorine (Cl2).
    • Depressants: Slow down the brain and central nervous system.
    • Examples: Benzodiazepines (e.g., alprazolam) and barbiturates (e.g., phenobarbital).
    • Asphyxiants: Cause unconsciousness or death by suffocation.
    • Types: Chemical asphyxiants (e.g., carbon monoxide) and simple asphyxiants (e.g., nitrogen).
    • Mutagens: Change the genetic information of an organism.
    • Examples: Formaldehyde, ethanol.
    • Teratogens: Cause harm to a fetus during pregnancy.

Factors of Toxicity

  • Factors that contribute to toxicity include:
    • Routes of entry (inhalation, ingestion, absorption, injection).
    • Amount of the dose.
    • Level of exposure.
    • Individual resistance to the substances.
    • Physical and chemical properties of the substances.

Routes of Entry for Toxic Substances

  1. Inhalation: Airborne toxic substances that can enter the bloodstream via the respiratory system.
    • Influenced by concentration, duration of exposure, and breathing volume.
  2. Absorption: Passage through the skin.
    • Affected by molecular size, ionization degree, aqueous and lipid solubility.
  3. Ingestion: Entry through the mouth and subsequent absorption from the stomach into the bloodstream.
  4. Injection: Direct introduction into the body using syringes or needles.

Effects of Toxic Substances

  • Acute Effects: Symptoms appear rapidly (seconds to hours).
  • Chronic Effects: Symptoms emerge slowly and can take months or years to manifest.

Dose Response Relationships

  • Dose Threshold: Minimum dose required for a measurable effect.
  • Lethal Dose: Dose likely to cause death and lethal concentrations for inhaled substances.

OSHA Standards (29 CFR 1910)

  • Essential for regulating toxic and hazardous materials in the workplace including the following:
    • Compressed gases (1910.101).
    • Specific chemical hazards (e.g., acetylene, nitrogen).
  • Employee Right-To-Know: Includes:
    • Hazardous product inventory.
    • Material Safety Data Sheets (MSDS).
    • Proper labeling.
    • Emergency response plans.
    • Employee training on hazards.

Airborne Contaminants

  • Types:
    • Particulates: Solid or liquid air contaminants (dusts, fumes, mists).
    • Vapor: Liquid substances released into the air.
    • Aerosols: Small particles suspended in air.
    • Gases: Formless fluids that can be hazardous in confined spaces.
  • Exposure Limits: Includes permissible exposure limits (PELs), short-term exposure limits (STELs), ceiling limits, and threshold limit values (TLVs).

Sick Building Syndrome

  • Definition: Poor indoor air quality leading to health issues in occupants.
  • Causes:
    • Ventilation system issues.
    • Inadequate air flow and infiltration rates.

Confined Spaces Hazards

  • Definition: Areas with limited entry or exit, not designed for continuous occupancy (e.g., vaults, silos, sewers).
  • Hazard Management: Requires purging toxic gases, proper PPE, and monitoring gas levels before entry. Ensure equipment is powered down and appropriate permits are obtained before work commences.