Study Notes on Chemical Hazards in Occupational Health

Chemical Hazards in Occupational Health

Overview of Occupational Health

  • Concerns can be framed by several categories:

    • By Hazard Categories:

    • Chemical, Physical, Biologic, Psychological

    • By Health Effects:

    • Examples include: pulmonary, dermatologic, neurologic, etc.

    • By Specific Hazards:

    • Examples include: asbestos, noise, hepatitis, workplace violence

    • By Occupations:

    • Specific to: miners, construction workers, firefighters, etc.

Respiratory Anatomy and Inhalation

  • Key Anatomical Structures:

    • Frontal Sinus

    • Sphenoid Sinus

    • Nasal Cavity

    • Nasal Vestibule

    • Connective Tissue

    • Alveolar Sacs

    • Alveolar Duct

    • Oral Cavity

    • Pharynx

    • Mucous Gland

    • Mucosal Lining

  • Process of Inhalation:

    • Inhalation serves as a direct and rapid route for toxic exposure to get into the lungs.

Effects of Chemical Substances on Respiratory Health

  • Chemical substances can exist in various forms:

    • Solids, Liquids, Dusts, Vapors, Gases, Fibers, Mists, Fumes

  • Upon inhalation, chemicals can:

    • Attack the nose, throat, or lungs directly.

    • Enter the bloodstream via the lungs and harm internal organs such as the liver.

Definitions of Airborne Matter

  • Gas: Air-like state of matter, e.g., O3 (Ozone)

  • Vapor: Matter in gaseous state below critical temperature, e.g., water vapor

  • Mist: Liquid droplets suspended in air, e.g., paint mist

  • Fume: Solids generated by condensation of gas after volatilization of molten metal, e.g., from welding or smelting

  • Dust: Particulate matter, e.g., coal that comes in two categories:

    • "Inhalable Dust" (>10 µm) deposits in upper airways.

    • "Respirable Dust" (<10 µm or PM10) deposits in lungs.

  • Fiber: Particulates with a length-to-width ratio >3:1, e.g., asbestos.

Disease Burden Linked to Occupational Risks

  • Total disease burden (in Disability-Adjusted Life Years - DALYs) attributable to occupational risks, categorized by disease (2015): Chronic Obstructive Pulmonary Disease (COPD)

  • Data Source: WHO, 2018

Types of Respiratory Hazards

  1. Asphyxiants:

    • Definition: A gas or vapor depriving cells of oxygen.

    • Examples include:

      • Carbon monoxide (CO)

      • Hydrogen cyanide (HCN)

      • Hydrogen sulfide (H2S)

  2. Irritants:

    • Cause direct damage to respiratory tissue.

    • Induce inflammation around the affected tissue.

    • Examples include:

      • Ozone (O3)

      • Nitrogen Dioxide (NO2)

      • Sulfur Dioxide (SO2)

      • Particulates

      • Formaldehyde

      • Ammonia (NH3)

      • Chlorine (Cl2)

  3. Restrictive Lung Disease:

    • Characterized by restricted alveolar expansion due to fibrosis and scarring.

  4. Obstructive Lung Disease:

    • Characterized by obstruction of air movement through bronchial tubes.

    • Includes chronic obstructive pulmonary disease (COPD) and asthma.

Occupational Risk Statistics (2004)

  • Deaths from selected occupational risks amounted to:

    • Noise: 0 deaths

    • Ergonomic Stressors: 1 death

    • Carcinogens: 34 deaths

    • Airborne Particulates: 43 deaths

    • Total: 457 deaths (High vs Low and Middle Income)

  • Data source: WHO, IER, 2007

Specific Respiratory Hazards

  1. Quartz (Silica)

  2. Asbestos

  3. Coal

  4. Diacetyl:

    • Represents a butter flavoring chemical with the structure O=C(H3C)C

Health Effects Related to Asbestos Exposure

  • Asbestos was historically common and deemed safe (used as “snow” on movie sets in the 1930s).

  • Restricts lung expansion leading to decreased lung volume and inadequate ventilation.

  • Crocidolite (Blue Asbestos) is particularly hazardous:

    • 2 million tons of asbestos are still used annually, mainly produced in Russia and used in China.

    • 125 million international workers are regularly exposed, resulting in over 100,000 annual deaths attributed to asbestos.

    • Classified as a confirmed carcinogen (e.g., Mesothelioma) with a long latency period of 20-30 years after exposure.

Deaths Due to Silicosis and Asbestosis

  • Death statistics reveal:

    • Silicosis:

    • Nearly 4% of exposed workers develop the condition causing diffuse interstitial fibrosis restrictive to lung volume.

    • Associated with lung cancer, chronic bronchitis, and susceptibility to tuberculosis.

  • Data on deaths due to:

    • Silicosis and Asbestosis indicates significant occupational health concerns.

Historical Context: Mining

  • The metaphor “canary in the coal mine” relates to traditional mining safety measures, resulting in the first occupational safety regulations in the US in 1891.

  • The Federal Mine Safety and Health Act (Mine Act) was established to ensure safety in mining operations.

Global Cancer Burden and Occupational Risks

  • Global burden concerning occupational-related cancer registrations is categorized by carcinogens and major industries.

  • Example figures indicate major industry sectors like construction account for notable cancer registrations linked to carcinogens, including:

    • Asbestos

    • Shift Work

    • Mineral Oils

    • Silica

    • ETC.

Mesothelioma Overview

  • Mesothelioma is a rare and severe form of lung cancer linked to asbestos exposure with an average survival of under one year post-diagnosis.

  • Approximately 80% of mesothelioma cases relate to asbestos exposure, manifesting after nearly 40 years of latency.

Respiratory Protective Equipment (RPE)

  • RPE is critical in managing exposure:

    • Disposable RPE and various types (SCBA, Half Mask, Gas Mask) serve to mitigate inhalation of hazardous substances.

Obstructive Lung Disease Overview

  • Lungs can become hyper-inflated due to air trapping from exposures like dust and chemicals.

  • At-risk occupations include construction work.

  • Examples include:

    • Chronic Obstructive Pulmonary Disease (COPD)

    • Asthma

    • Bronchiolitis obliterans

Popcorn Workers Lung Disease (Bronchiolitis Obliterans)

  • Caused by diacetyl exposure in food flavoring plants.

  • Instances traced to workers handling butter flavoring led to severe respiratory problems.

OSHA Recommendations and Protocols

  • OSHA advocates for:

    • Air monitoring in workplaces for flavoring exposures.

    • Use of engineering controls and PPE.

    • Medical evaluations for atrisk workers showing symptoms.

    • Training for worker health protection.

Occupational Carcinogen Exposure

  • Occupational exposure to known lung carcinogens raises risk significantly, accounting for a notable percentage of lung cancer in men (approximately 10-15%).

  • A latency of 10-15 years is common before classic lung cancers manifest.

International Agency for Research on Cancer (IARC)

  • Agency under WHO responsible for:

    • Conducting and coordinating cancer research.

    • Surveillance of cancer occurrence globally.

    • Classifying carcinogens based on risk (Groups 1, 2A, 2B, 3, and 4).

Examples of Category 1 Carcinogens

  • Agent Sources:

    • Arsenic (smelters, mines, drinking water) - Lung, skin, bladder cancers

    • Asbestos (mining, manufacturing) - Lung, pleura, peritoneum

    • Benzidine (dyes, textiles) - Bladder cancer

    • More examples follow similar structure.

Surveillance of Workers Exposed to Respiratory Hazards

  • Pulmonary Function Tests (PFTs) assist in determining lung function and detecting health changes early.

  • Example data includes the summary of a patient's PFT results over time and general trends in pulmonary health.

Control of Occupational Hazards

  • Hierarchy of Controls:

    • Physically remove the hazard

    • Substitute the hazard

    • Isolate individuals from the hazard

    • Modify work methods

    • Use Personal Protective Equipment (PPE) as a last resort.

Setting Occupational Health Standards

  • NIOSH sets recommended exposure limits (RELs), while OSHA establishes permissible exposure limits (PELs) as regulatory measures.

Key Takeaways

  • Reducing exposures may decrease but not entirely eliminate health risks.

  • Continuous health surveillance is key to monitoring exposure control effectiveness.

  • The workplace environment presents a high-risk scenario, but many risks are preventable with effective intervention.

  • Ongoing concern remains with asbestos exposures.