NEBOSH Chemical and Biological Hazards 2

Question 1

What is the difference between a WEL 8-hour TWA and a WEL short-term exposure limit (STEL)?

Accepted Answer

The 8-hour TWA is the average concentration over a full shift, while the STEL is the maximum concentration over any 15-minute period

Answer

The 8-hour TWA (Time-Weighted Average) is the average concentration over a standard 8-hour working day. The STEL (Short-Term Exposure Limit) is the maximum concentration over any 15-minute reference period during the working day. STELs prevent excessive short-term peaks even when the 8-hour TWA is met.

Question 2

Under COSHH 2002, what is the hierarchy of control measures for hazardous substances?

Accepted Answer

Elimination, substitution, engineering controls (enclosure/LEV), administrative controls (safe systems of work), and PPE as a last resort

Answer

COSHH follows the hierarchy: (1) eliminate the substance or process, (2) substitute with a less hazardous alternative, (3) engineering controls such as total enclosure, partial enclosure with LEV, or general ventilation, (4) administrative controls including safe systems of work, reduced exposure time, and hygiene measures, (5) PPE as a last resort when other measures are insufficient.

Question 3

What is Legionella and where is it commonly found in the workplace?

Accepted Answer

A bacterium found in water systems that can cause Legionnaires' disease, commonly found in cooling towers, hot and cold water systems, spa pools, and humidifiers

Answer

Legionella pneumophila is a bacterium that thrives in water temperatures between 20-45°C. It is commonly found in cooling towers, hot and cold water systems (especially where water stagnates), spa pools, humidifiers, and decorative fountains. Inhalation of contaminated water droplets (aerosols) can cause Legionnaires' disease, a severe form of pneumonia.

Question 4

Which GHS signal word indicates the more severe level of hazard?

Accepted Answer

Danger

Answer

GHS uses two signal words: 'Danger' for the more severe hazard categories and 'Warning' for less severe categories. Only one signal word appears on a label. If a product has multiple hazards, the most severe signal word takes precedence. 'Caution' and 'Alert' are not GHS signal words.

Question 5

What is health surveillance and when is it required under COSHH 2002?

Accepted Answer

Monitoring the health of employees who are exposed to substances linked to identifiable diseases or adverse health effects, where there is a reasonable likelihood of the condition occurring and valid techniques exist to detect it

Answer

Health surveillance under COSHH Regulation 11 involves systematic health monitoring of employees exposed to hazardous substances. It is required when: there is an identifiable disease or adverse effect linked to the exposure, there is a reasonable likelihood it may occur under the conditions of work, and valid detection techniques exist (e.g., lung function tests for respiratory sensitisers, skin checks for dermatitis-causing agents).

NEBOSH IGC Practice Test

NEBOSH IGC Practice Test

NEBOSH Chemical and Biological Hazards 2