Section A Questions Deck 5

Question 1

Dilution ventilation is sometimes used to control certain types of

hazardous substances generated in a workplace.

(a) Outline circumstances when dilution ventilation may be

appropriate as a control measure. (3)

(b) Explain how an effective dilution ventilation system is designed

and operates to reduce exposure to a hazardous substance. (4)

(c) The following specification applies in an open-plan workshop:

Calculate the actual number of air changes per hour AND

comment on the suitability of the specified dilution ventilation

system. (3)

Answer 1

(a) Dilution ventilation can be considered as a control option in several circumstances including:

• when the hazardous substance has low toxicity (or high OEL),
• has a low generation rate
• and is a fume, vapour, or gas (but not a dust).

(b) the air input can be passive (natural air movement) through windows, doors or vents or active (via fans), that clean input air mixes with contaminants to dilute the contaminant concentration, hence reducing exposure levels. The positioning of air inlets and outlets is dependent on the relative density of the contaminant and needs to avoid dead spots. Air throughput (air changes) needs to be sufficient to reduce concentrations to safe levels.
(c) Volume of the workshop: 10x10x3 = 300m3

The air throughput is 3000m3/hr

which means that every hour a volume equivalent to 10 times (3000m3/300m3 = 10) the volume of the workshop passes through it.

In other words, there are 10 ‘air changes’ per hour.

This is just within the specification (10 - 15 air changes per hour) but a recommendation would be to increase the throughput so it is closer to 15 air changes per hour.

Question 2

Audiometry can be used to assess a worker’s hearing.

(a) Explain what is meant by the term ‘threshold shift’. (2)
(b) The figure below shows an audiogram for an adult worker.
(i) Give the name of the hearing condition indicated in this audiogram. (1)
(ii) Describe the physical changes in the inner ear for an adult worker with this audiogram result. (2)
(iii) Outline the resultant effect on hearing for an adult worker with this audiogram result. (1)
(iv) Outline reasons why audiometry testing may not produce an accurate representation of the effects of workplace noise exposure on a worker’s hearing. (4)

Answer 2

Part (a)

Temporary Threshold Shift (TTS)

Exposure to a high noise level; hearing acuity returns with time. (Caused by the fatigue of the hair cells in the cochlea.)

A dip in hearing acuity occurs at 4,000 Hz.

Permanent Threshold Shift (PTS)

A non-reversible condition; usually follows from continual TTS exposure.

b) i) Noise induced hearing loss (NIHL)
ii) damage in the ear or inner ear, damage in the cochlea or damage to hair cells. hair cells being broken or flattened.
iii) A worker with noise-induced hearing loss would not hear consonants clearly and would only hear vowels
iv) Limitations of audiometry include:

• Not preventative.
• Information may precipitate claims.
• Possible inaccuracies in data.
• Does not identify the source of noise-induced hearing loss. As it could be that workers don’t wear PPE at work, or possibly that they listen to loud music with headphones on.

Question 3

An organisation is considering the substitution of a chemical it currently uses, for an alternative one.

Outline what should be considered when assessing the risk of using a new chemical. (10)

Answer 3

The first step in assessing the risks of hazardous chemicals is to read the safety data sheet (SDS). The SDS provides information about the health hazards if it is breathed in, swallowed, or if there is contact with the skin or eyes. It also provides other hazard information such as whether it is flammable or toxic.

Identification of health risks to susceptible workers, for example how the chemical will affect pregnant women and young persons.

The control measures needed to comply with legal standards, for instance, it might be required the specialized waste bins, or a specialized licensed company must be contracted to dispose of the chemical.

The effect of mixtures with current chemicals that will not be substituted, it could be that introducing the new chemical could add to the toxicity of another chemical being used or vice versa (additive effect) etc.

Unusual activities should also be considered taking into account any unusual activities that are known to occur or that are reasonably foreseeable. This includes cleaning and maintenance work and emergencies, such as power cuts and spillages.

Question 4

Outline what should be considered when selecting workplace seating to minimize ergonomic risks to workers. (10)

Answer 4

Some features are important for a good chair regardless of how you intend to use it:

• Adjustability - Check to see that seat height is adjustable.
• Seat height range - Check whether the seat height can be adjusted to the height recommended for the worker(s) who will use it. Alternate chairs may have to be selected for very short or tall workers. Ideally, a user should be able to sit with their feet on the floor or on a footrest without pressure on the underside of their thighs.
• Backrest - Check to see that the backrest is adjustable both vertically and in the frontward and backward direction and has firm lumbar support but does not create pressure points that restrict blood circulation. The backrest should be of appropriate height and width to provide support without restricting movement.
• Seat depth - Select the seats that suit the tallest and the shortest users. Users should be able to sit in the chair without pressure at the back of their knees, with their back supported by the backrest, and support through the buttocks and thighs.
• Seat width – The seat should be wide enough to allow users to have a comfortable and even pressure across the entire seat and allow for some adjustments to their posture.
• Seat angle – Where the angle of the seat is adjustable, the seat should allow users to support their feet on the floor or footrest. Forward sloping seats should have a surface that has enough friction to prevent the user from sliding out of the chair or placing too much weight on their feet.
• Seat surface – The seat surface should be comfortable, usually made of breathable materials that minimize heat and moisture build-up. In some workplaces, such as healthcare or laboratories where infection control is a concern, other materials may be more appropriate.
• Armrests – armrests should provide support and evenly support the arms. The rests should be adjustable both for height and width (distance from the seat). In other situations, armrests may not be helpful if they prevent a person from sitting close enough to the desk and keyboard. Adjust or remove armrests, as needed.
• Stability - Check for the stability of the chair; a five-point base is recommended.

Other features to consider

• See if the selected chair has features that will help someone do their job better. Armrests with adjustable heights are good for computer operators. Wider or narrower armrests may also be required depending on the worker’s dimensions and tasks they do.
• See if the selected chair has features that will make doing a job more difficult. An example may be that someone may be using a chair with casters or wheels when a stable and stationary work position would be better. If chairs with casters are needed, choose ones that match the type of flooring you have (e.g., hard casters for carpeting or soft casters for hard floors). Determine if there is a need to have brakes on the casters.
• The user should be able to operate the controls from a seated position where practical, and be logical in their placement and function.

Question 5

Workers in a chemical manufacturing plant need personal protective equipment (PPE) to protect their eyes and faces when handling open containers of highly corrosive liquids.

(a) Describe what should be considered when selecting the PPE for this task. (6)
(b) Outline arrangements that the chemical manufacturer should put in place when the selected PPE is in use. (4)

Answer 5

(a)

• It is appropriate for the risks and conditions, it must have the ability to protect against the specific workplace hazards, in this case, the highly corrosive liquid.
• It takes account of ergonomic requirements; it Should fit properly and be reasonably comfortable to wear
• It does not increase the overall risk
• it meets the relevant standards.
• Should provide unrestricted vision and movement
• Should be durable and cleanable
• Should allow unrestricted functioning of any other required PPE

(b)

• Storage Provision must be made for the safe storage of PPE away from sources of contamination. It is common practice to provide a locker or storage area for PPE and RPE.
• Maintenance PPE must be maintained in safe working order. The level of maintenance will be determined by the item, manufacturer’s recommendation, and the conditions of use.
• Clear and constant supervision of the use of PPE must be demonstrated
• Training requirements, if workers are to use PPE effectively, they must be provided with information, instruction, and training, for example on how and when the PPE should be uses, storage requirements, how to clean, inspect, maintain, or replace.

Question 6

(a) Give the meaning of the term ‘vocational rehabilitation. (2)

A worker has been absent from work for eight months following a back injury. This was a work-related manual handling injury. This worker is due to return to work.

(b) Using the bio-psychosocial model, outline possible barriers to the worker’s rehabilitation. (3)
(c) Outline ways in which the employer can assist workers to return to work. (5)

Answer 6

(a) Vocational rehabilitation is the process of returning a worker back to meaningful work as a way of aiding their recovery and return to health following a period of physical or mental ill-health. It can also be a way of improving the health of an individual through getting them into work and keeping them at work.
(b) The bio-psychosocial model takes a more holistic view that includes biological, psychological, and social aspects in considering ill-health.

Considering this, the possible barriers to the workers’ rehabilitation could include:

Biological barriers – the physical disability in this case which is the back pain may have impaired mobility which restricts the type of work that the individual can safely perform.

Psychological barriers – These barriers are the inevitable psychological ones that will arise following any long-term absence from work. The worker may be fearful that returning to work may worsen their ill-health condition. They may worry that work colleagues think less of them if they are unable to work to the full extent due to restrictions on working hours or type of work.

Social barriers – These barriers may be physical in nature, such as access to and from the workplace and workstation design and layout, In other instances, these barriers may be more to do with workplace arrangements and the way that work is organized.

(c)

Keeping in contact with the individual – Regular contact is vital to prevent the employee from feeling isolated, to keep them up to date with developments in the workplace, and to prepare them for return to work.

Health, Occupational or rehabilitation interventions – It is vital that the manager, health specialist, HR, and the employee work together to bring about the most positive outcome – usually a return to work and an ongoing reduction in sickness absence. Early investment (financial, training, or time) is more likely to lead to a complete recovery and positive return to work.

Changes to work patterns or the environment – Temporary or permanent changes to work patterns or to the working environment are often an effective way of managing return to the workplace after long-term sickness absence.

• Temporary changes can include
  
  • Phased return to previous job and hours
  • No Lone working
  • Buddying with a colleague etc.
• Permanent changes can include:
  
  • Change of job or job level/responsibility
  • Change of hours
  • Change of base etc.

Return to work interviews – conducting an interview with the worker upon his return to work is a great way of assessing where the employee is mentally as well as physically and will allow a better understanding of what will be necessary to have the employee return to work.

Question 7

Workers at a waste-water treatment plant are at risk of contracting

cryptosporidiosis.

(a) Explain how these workers might contract cryptosporidiosis. (4)
(b) Identify symptoms associated with cryptosporidiosis. (2)
(c) Outline specific control measures that these workers should use

to help reduce the risk of contracting cryptosporidiosis. (4)

Answer 7

(a) Cryptosporidiosis is caused by a protozoan parasite (cryptosporidium parvum) and is found in water contaminated with humans feces. As the workers are at a waste-water treatment plant, they are at high risk

It is transmitted by the hand-to-mouth route.

These workers could easily be in contact with contaminated water or equipment, as well as spreading it from one person to another.

(b) Symptoms include:

• Watery diarrhea.
• Stomach cramps or pain.
• Dehydration.
• Nausea.
• Vomiting.
• Fever.
• Weight loss.

(c) Control measures the workers can use include:

• handwashing with soap and water,
• use of disinfectants,
• use of suitable gloves and
• prohibition of eating/drinking in work areas

Question 8

The hazardous substance called machine-made mineral fibre (MMMF)

has a legally binding occupational exposure limit (OEL) listed in

standards. Unusually, there are two OELs. The limit is expressed both

as fibre/ml and as mg/m3:

2 fibre/ml 8-hour time-weighted average (TWA);

5 mg/m3 8-hour TWA).

Two personal monitoring results, obtained using two different measuring

techniques for an operative working with MMMF, are provided below:

(a) Calculate the average concentration of MMMF to which the

operative is exposed for EACH of the two samples shown. (6)

You must show your working.

(b) Comment on the significance of the operative’s exposure in

terms of future action required to adequately control exposure. (4)

Assume the exposure in the time monitored is representative of

Answer 8

(a) sample 1, we first calculate the volume of contaminated air drawn

through the pump. This is 0.5 x 6 x 60 = 180 litres.

We need to convert this to ml; 180 litres = 180 x 1000 = 180,000 ml. We collected 5625 fibres over the sampling period,

so, the average concentration is 5625 fibres/180,000ml = 0.03 fibres/ml for the 6 hour sampling time.

sample 2 (gravimetric method), there is a similar approach (but the units are of

course different). Once again, we calculate the volume of contaminated air drawn

through the filter = 2 x 4 x 60 = 480 litres. We convert this to m3; 480/1000 = 0.480 m3.

2mg was collected, so the average concentration = 2mg/0.480m3 = 4.17mg/m3 over the

4 hours sampling time.

(b) It is evident that the fibre value (0.03 fibres/ml) is well below the fibre count OEL (2 fibres/ml) but that the gravimetric value (4.17mg/m3) is below, but quite close to the gravimetric OEL (5mg/m3). More detailed monitoring would be recommended and, since the gravimetric method is clearly more discriminating (in this case, as the fibre value is so very low) the gravimetric method is the most suitable method going forward.

Question 9

A fire alarm engineer visits many customers’ premises during the working

day in order to check that fire alarm sounders are operating at the correct

sound level. The engineer does not wear hearing protection.

(a) Explain how the engineer may be at risk of hearing damage. (3)
(b) Explain how the engineer’s personal noise exposure should be
determined. (7)

Answer 9

(a) The engineer would experience frequent but brief exposure to very loud noise that, over the course of time, could exceed legal limits and lead to hearing damage. And in the long-term cause NIHL.
(b) The Engineer should make use of a personal sound level meter/dosimeter, given the fact that the engineer is highly mobile, and the noise levels are likely to be highly variable from day to day.

It should be ensured that the equipment used is calibrated when issued as well as calibrated as per the OEM requirements. (Normally annually). The dosimeter microphone should be fitted close to the worker’s ear to get as close to real scenario sound levels as possible. The dosimeter indicates LAeq and ideally should have a data logging function as well as a conversion of the result to LEP,d

The Engineer should keep a daily work log to verify the sources of exposure.

Question 10

A bus company operates a fleet of buses to provide transport for

passengers in a busy city. The bus driver is the only bus company

worker on each bus. Bus drivers are sometimes subject to violence.

(a) Outline why these bus drivers may be at an increased risk of
violence. (5)
(b) Outline practical control measures to help reduce the risk of

violence to these bus drivers. (5)

Answer 10

(a)

• that lone working (seen as more of a target),
• ill-behaved passengers,
• dissatisfied passengers (eg having to wait too long for the bus to arrive)
• passengers attempting to avoid paying,
• Passengers having a bad day and taking it out on the bus driver

(b) measures such as

• barriers between passenger and driver,
• cashless systems (smartcards, pre-paid tickets),
• security cameras,
• vehicle tracking devices and
• alarms/communications to control room.(Panic Button)