Questions: Occupational Health Surveillance and Hazard Control

Question 1

Workers in a ceramics factory are exposed to high concentrations of respirable crystalline silica. Management responds by issuing N95 respirators to all workers. Which statement best evaluates this response?

• A. This is the optimal control because respirators directly protect each worker from inhaling silica
• B. This is appropriate as a short-term emergency measure, but engineering controls such as local exhaust ventilation should be the primary long-term solution
• C. This is sufficient because PPE is the most reliable control when properly used
• D. This is appropriate because administrative controls should be exhausted before engineering controls are considered

Answer: (B)

Respirators are last in the hierarchy of controls. They depend entirely on correct use at every exposure moment — they leak around facial hair, workers remove them when hot, and they provide no protection when forgotten. Local exhaust ventilation (an engineering control) captures silica dust at the source before it reaches breathing zones, without relying on worker behavior. Option C is the classic misconception that PPE is 'direct protection' — in practice, it is the most failure-prone control.

Question 2

A pulmonologist notices a cluster of workers at a shipyard with abnormal chest X-rays suggesting asbestosis. She contacts the occupational health unit. What surveillance stream should this trigger?

• A. Passive reporting only, since the disease has already appeared and prospective surveillance is no longer useful
• B. Medical surveillance only, to screen remaining workers for early disease
• C. Hazard surveillance — measuring airborne asbestos fiber levels — to assess current exposure and prevent further disease
• D. Both hazard surveillance (airborne fiber monitoring) and intensified medical surveillance of remaining workers

Answer: (D)

The two surveillance streams are complementary and should be triggered together. Medical surveillance (screening remaining workers for subclinical disease) identifies who else may be affected. Hazard surveillance (measuring current asbestos levels) determines whether ongoing exposure continues — it is possible current workers are still being exposed decades after the original cohort. The two streams feed each other: medical findings prompt exposure investigation; exposure findings intensify health monitoring.

Question 3

Personal protective equipment is the least preferred control in the hierarchy because it provides no protection to the worker.

• T. True
• F. False

Answer: False

PPE does provide protection — when used correctly. The reason it is last in the hierarchy is that it depends entirely on consistent correct use by the worker at every exposure moment, making it the most failure-prone control. Engineering controls (which remove or isolate the hazard) and elimination/substitution (which remove the hazard entirely) are preferred because they work independently of worker behavior.

Question 4

Occupational medical surveillance for diseases with long latency periods — such as asbestosis or silicosis — must begin at the time of initial employment, long before any symptoms appear.

• T. True
• F. False

Answer: True

Silicosis takes 10–20 years of cumulative exposure to manifest clinically; mesothelioma presents 30–40 years after asbestos exposure. By the time symptoms appear, irreversible fibrosis is already established and the causal exposures are decades in the past. Longitudinal baseline measurements (pulmonary function tests, chest X-rays, audiograms) from initial employment create a surveillance record that detects trends — slowly declining FEV₁, for example — long before clinical disease, allowing intervention before irreversible damage occurs.

Question 5

Explain why engineering controls are ranked above administrative controls in the hierarchy of controls for occupational hazards.

Model answer: Engineering controls physically remove or isolate the hazard — local exhaust ventilation captures dust before it reaches breathing zones; enclosure prevents worker exposure entirely — without depending on worker behavior. Administrative controls (job rotation, shift limits, access restrictions) reduce exposure by modifying work organization, but still leave the hazard present and rely on consistent procedural compliance from workers and supervisors. Since human behavior is more variable and failure-prone than physical systems, controls that function regardless of worker behavior are more reliable and therefore ranked higher.

This principle — that controls higher in the hierarchy work independently of human reliability — is why the hierarchy is ordered by effectiveness, not convenience. PPE at the bottom requires correct use at every exposure moment; elimination at the top removes the problem completely regardless of what anyone does.