ABT Occupational Toxicology 2 — Questions and Answers
Question 1: Silicosis results from occupational inhalation of which form of silica?
- Amorphous silica (diatomaceous earth)
- Crystalline silica (quartz) (Correct answer)
- Silicon carbide
- Vitreous fused silica
Correct answer: Crystalline silica (quartz)
Crystalline silica, particularly quartz, is fibrogenic and causes progressive pulmonary fibrosis (silicosis) upon inhalation.
Question 2: Which type of asbestos fiber is associated with the greatest risk of mesothelioma due to its biopersistent, thin, needle-like morphology?
- Chrysotile (white asbestos)
- Amosite (brown asbestos)
- Crocidolite (blue asbestos) (Correct answer)
- Tremolite
Correct answer: Crocidolite (blue asbestos)
Crocidolite (blue asbestos), an amphibole fiber, carries the highest mesothelioma risk due to its biopersistance and fiber dimensions that allow deep lung penetration.
Question 3: Occupational asthma caused by toluene diisocyanate (TDI) primarily involves which immunological mechanism?
- IgE-mediated (Type I) hypersensitivity (Correct answer)
- IgG-mediated (Type III) immune complex deposition
- Cell-mediated (Type IV) delayed hypersensitivity
- Direct pharmacological airway irritation without sensitization
Correct answer: IgE-mediated (Type I) hypersensitivity
TDI-induced occupational asthma typically involves IgE-mediated sensitization, causing immediate hypersensitivity reactions with bronchospasm upon re-exposure.
Question 4: n-Hexane causes peripheral neuropathy through which specific mechanism?
- Direct membrane disruption by the parent compound
- Formation of 2,5-hexanedione which cross-links neurofilament proteins (Correct answer)
- Inhibition of axonal acetylcholinesterase activity
- Competitive inhibition of myelin synthesis
Correct answer: Formation of 2,5-hexanedione which cross-links neurofilament proteins
n-Hexane is metabolized to 2,5-hexanedione, which pyrrylates lysine residues in neurofilament proteins, causing cross-linking and axonal swelling (giant axonal neuropathy).
Question 5: Minamata disease is caused by occupational and environmental exposure to which toxic substance?
- Inorganic lead
- Cadmium
- Methylmercury (Correct answer)
- Inorganic arsenic
Correct answer: Methylmercury
Minamata disease results from methylmercury poisoning documented in Minamata Bay, Japan, where industrial effluent contaminated the marine food chain.
Question 6: Coal workers' pneumoconiosis (black lung disease) is caused by chronic inhalation of which dust?
- Crystalline silica dust
- Coal dust (Correct answer)
- Talc particles
- Iron oxide fumes
Correct answer: Coal dust
Coal workers' pneumoconiosis results from the progressive accumulation of coal dust in the lungs, leading to macule formation and, in severe cases, progressive massive fibrosis.
Question 7: The General Duty Clause (Section 5(a)(1)) of the OSH Act requires employers to:
- Post all OSHA regulations visibly in the workplace
- Provide a workplace free from recognized hazards likely to cause death or serious harm (Correct answer)
- Conduct annual certified industrial hygiene surveys
- Register all hazardous chemicals with OSHA before use
Correct answer: Provide a workplace free from recognized hazards likely to cause death or serious harm
Section 5(a)(1) of the OSH Act obligates employers to provide workplaces free from recognized hazards causing or likely to cause death or serious physical harm to employees.
ABT Occupational Toxicology 2
Silicosis results from occupational inhalation of which form of silica?