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Guidance to learners

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should you ‘cut and paste’ blocks of text from the Internet or other sources.

The examination begins with a scenario to set the scene. You will then need to complete a series of
tasks based on this scenario. Each task will consist of one or more questions.

Your responses to most of these tasks should wholly, or partly, draw on relevant information from the
scenario. The task will clearly state the extent to which this is required.

The marks available are shown in brackets to the right of each question, or part of each question.
This will help guide you to the amount of information required in your response. In general, one mark
is given for each correct technical point that is clearly demonstrated. Avoid writing too little as this
will make it difficult for the Examiner to award marks. Single word answers or lists are unlikely to
gain marks as this would not normally be enough to show understanding or a connection with the
scenario.

You will have 2 weeks (10 working days) to complete the assessment.

Please refer to your registration confirmation email for the upload deadline.

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You must use the available answer template.

NEBOSH

DO – CONTROLLING WORKPLACE HEALTH ISSUES
(INTERNATIONAL)

UNIT DI2:
For: NEBOSH Level 6 International Diploma for Occupational Health and Safety

Management Professionals

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SCENARIO

Water Wise Analytics (WWA) is a successful and growing organisation carrying out water quality
testing and analysis. WWA is based at a purpose-built facility within an industrial unit, on the edge of
a large town with good access to main roads. There are 30 workers at WWA, mainly consisting of
scientists and technicians working in four different labs. In addition, the organisation has a fieldwork
team. Most days the fieldwork team are out at various sites. Their role is to inspect water sources
and take water samples from numerous locations, bringing these back to the labs for testing. WWA
also has a range of office-based support services, including an administration team, IT support,
human resources, and a health and safety team.

There are 4 purpose-built labs, each specialising in different types of testing and analysis. Lab 1
identifies contaminants in water samples, and where required produces a water treatment plan. This
will be done when the water source needs to be treated so that it is fit for purpose. Lab 4 is a
microbiology lab specialising in testing for Escherichia coli (E. coli 0157).

Each lab has a range of equipment relevant to the type of work carried out, including workbenches
with stools, chemical storage cupboards under the workbenches, fume cupboards, autoclaves,
incubators, and microscopes. Each lab also has its own changing rooms and toilets. The scientists
and technicians are highly trained in their specific work. All scientists and technicians receive
detailed health and safety induction training about their own safe laboratory working procedures.

Laboratory 1 (Lab 1)

In this lab, workers are testing water samples and working on water treatment plans. The treatment
plans often require sodium hypochlorite to be added to water systems at an appropriate dose, and
the lab workers carry out tests to determine the dosing regime required. These tests involve adding
measured amounts of sodium hypochlorite to water samples. The sodium hypochlorite is supplied in
5 litre containers that are a manageable size to handle in the lab, and allow relatively small amounts
of sodium hypochlorite (typically 100 – 200mls) to be dispensed safely into measuring cylinders.

Today, worker B finds that the 5 litre container that is kept in the lab’s cupboard is empty, and visits
the stores to collect another. At the stores, worker B is informed that sodium hypochlorite is now
being purchased in a 20 litre container which is better value for money. The stores’ manager shows
worker B the advert in the supplier’s catalogue (see supporting document 1), and seems pleased
that they have managed to save the organisation money. They tell worker B that, in future, the 20
litre container will be delivered straight to the lab, so fewer trips to the stores will be needed.

Worker B, who is now running late on the day’s work schedule, returns to Lab 1 with this much larger
container. They feel quite hot after carrying the 20 litre container, so push up the sleeves on their lab
coat before putting on their PPE. Remembering their induction training worker B does not want to
decant any of the sodium hypochlorite into an unlabelled container, as this is not good practice.
Instead, they lift up the container and start to pour the required amount directly into the measuring
cylinder on the workbench. Unfortunately, the sodium hypochlorite comes out of the container very
quickly, spilling down the side of the measuring cylinder and onto the workbench. Worker B tries to
stop the measuring cylinder from falling over, and in doing this partly loses their grip on the large
container of sodium hypochlorite. There is now sodium hypochlorite all over the workbench, the
equipment, and on the forearms of worker B. Their colleagues grab the spill kit and rush to assist
worker B, and deal with the spillage.

The next day when Lab 1’s manager returns from annual leave, they see the accident report on their
desk. They are concerned that there will be lots of questions raised about the safe working methods
in Lab 1. They quickly look at the existing hazardous substance risk assessment for this task, and
the safety data sheet (SDS) for sodium hypochlorite (see supporting document 2). The lab
manager is thankful that the company-wide control system is now in place for hazardous substances.
This also means that they can confirm that all workers at WWA received training in the safe handling
of chemical and biological agents earlier in the year. However, that makes it more surprising to the
manager that this accident happened.

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Fieldwork Team

The Fieldwork Team meet up in their office to allocate the work for the day. The fieldwork manager
(FWM) has a list of samples that need taking or collecting, and sites where inspections are required.
There are three members of the Team who have been in the role for several years. Due to an
increased workload, three new workers have been recruited to the Fieldwork Team; they have just
finished their training and are about to start going out to sites on their own. Fieldworker A is one of
these new recruits; they came to this job straight from university, and are very eager to go out to sites
on their own in their company car. Work is allocated to the experienced fieldworkers and the two
other newly-trained fieldworkers.

The only work that is left to do during the day involves taking samples from various natural springs
and boreholes. Most of these sampling points are located down tracks, away from main roads in
isolated rural locations and on farmland. The FWM is concerned that this work is too much for new
fieldworker A’s first job on their own. Fieldworker A is very keen and states that they are aware of
where the sampling points are. They are familiar with these sites, having been out with one of the
experienced workers, and because they go cross-country running in these areas several times a
week. The FWM is convinced by fieldworker A, but insists that fieldworker A must phone them at
14:00 to update the FWM on their progress. Happy with this, fieldworker A takes the details of the
sample collections needed on their mobile phone and gathers what they need, including safety
equipment, before leaving for the first sampling point.

Fieldwork manager

The FWM is pleased that fieldworker A can take the samples today, as the FWM needs to speak to
the contractors, Find & Dig (F&D), about a large job starting next week. F&D are contracted by WWA
when an excavation is needed in order to locate, inspect, and sample water sources. The job next
week is at Marshes Road, and once excavated, the FWM will go out to inspect and take samples
along with a colleague. In the meantime, the FWM needs to email F&D’s manager to check that all
the arrangements are in place (see supporting document 4).

Fieldworker A

Meanwhile, fieldworker A arrives and parks as close as possible to the first site where they need to
take a sample. They have started with the site furthest away from the facility, and intend to work their
way through the jobs back towards Lab 1, delivering all the samples when they have finished. At this
first site they will have to walk about 1km to the sampling point. Fieldworker A starts walking down a
rough track. After a few minutes’ walk the path has ended and fieldworker A is walking across a
rocky terrain covered in slippery moss and grass. The sampling point is further up the hill in front of
them, in a small, wooded area. As they keep walking it starts to rain. Fieldworker A is used to rain
from their cross-country running, so carries on walking.

After a few minutes, fieldworker A arrives in the wooded area and starts looking for the natural spring.
After some time, fieldworker A still cannot find the sampling point. They get their phone out to check
the location again from the job details. They notice that it is now 14:30, but they do not have a phone
signal. Eventually, they find the natural spring and take a sample. As they come out of the wooded
area it is raining even harder and it is very dark. As they clamber over the rocky terrain they slip,
falling to their knees. Fortunately, they only bruise their knees. When fieldworker A gets back to the
car, they check their phone; they have a very weak phone signal, but they have several missed calls
from the FWM.

Find & Dig (F&D)

A week later, November 6 is a very cold morning when F&Ds’ workers arrive at the site on Marshes
Road. Worker X is going to begin with operating the hand-held percussive breaker (breaker), so they
put on the required PPE including hearing protection and eye protection, as well as steel toe-capped
boots. Meanwhile, worker Y is unloading the breaker and setting it up ready for worker X. Workers X
and Y are concerned that worker Z will be absent this morning, as worker Z is the most experienced
member of the team, having spent many years working for several organisations that do this type of
work. Workers X and Y feel under pressure as they know that workers from WWA will be coming to

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the site soon. Workers X and Y will share the use of the breaker equally to remove as much of the
road material as possible. After this, they will change to hand digging as they get close to the water
pipe. Around 11:15 the WFM from WWA arrives on site, and has to wait for the digging to be
completed before they can inspect the water pipe and take samples back to the lab for testing.

Important contract for Laboratory 4 (Lab 4)

Eighteen months ago, WWA won a major contract to carry out bathing water quality testing, on behalf
of the national environmental regulator. Water samples from inland and coastal bathing locations are
regularly collected and analysed in Lab 4 (the microbiology lab) at WWA. The analysis is done to
determine the level of any harmful biological agents, in particular E. coli 0157. The results produced
by WWA are published on a public information website for anyone to access. This is a high profile
project; there has recently been a lot of public attention due to health problems experienced by
people swimming in a small number of these bathing waters. There are currently many posts on
social media from swimmers who have become unwell after swimming at Green Valley Lake. The
shareholders at WWA are increasingly concerned that the organisation’s involvement in this work is
attracting bad publicity for WWA, and this is on the agenda of the forthcoming shareholders’ meeting.

As part of this contract, Lab 4 receives a constant stream of weekly samples from each of the 300
bathing water locations. The lab workers are very aware of the need for hand hygiene and wear
gloves to handle each 100ml bathing water sample. Each sample is passed through a specific
membrane filter that traps the E. coli 0157. The filter is then placed on a Petri dish that contains a
special growing medium (agar). After incubation at 36°C for approximately 24 hours, the E. coli 0157
is visible as blue or violet colonies on the agar. The number of colony forming units (cfu’s) per
100mls of water sample are counted. These results are reported on the public information website.
Lab 4’s workers are very experienced, and although the pace of work is intense, they take great care
and pride in their work, and so minimise the opportunity for contamination from water samples.

Using microscopes

In order to count the number of cfu’s on the Petri dishes a microscope is needed. Workers in Lab 4
spend a significant proportion of their time carrying out work using a microscope. The microscopes
owned by WWA are very basic, quite heavy, and are not adjustable. Typically, a worker will spend
eight hours a day looking at the samples through the microscope, counting the number of colonies
that have grown.

Supporting Documents

1. Advert in supplier’s catalogue

2. Safety data sheet (SDS) for Sodium Hypochlorite

3. Bathing water catchment area data

4. Email trail between WWA and F&D

5. Lone-minder device details

6. Extract from the HSE vibration exposure ready-reckoner (Daily exposure)

7. Image: Worker using a microscope

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Task 1: Use of sodium hypochlorite

1 At WWA, the way in which sodium hypochlorite is supplied has changed, as
described in the scenario and shown in supporting document 1.

(a) Discuss what difference, if any, this has made to the risks associated with

the use of sodium hypochlorite at WWA. (20)

Note: You should support your answer, where applicable, using relevant
information from the scenario and supporting documents 1 and 2.

(b) What additional control measures could be introduced in Lab 1 if it is

decided that the use of 20 litre containers of sodium hypochlorite is to be
continued? (15)

Note: You should support your answer, where applicable, using relevant

information from the scenario and supporting documents 1 and 2.

Task 2: Exposure to biological agents

2 The shareholders at WWA are increasingly concerned about the organisation’s
involvement in the handling and testing of bathing water samples. This work is
attracting bad publicity and they have asked for an update to reassure them.

(a) Prepare a short briefing note to the shareholders on E. coli 0157 outlining

the

(i) type of biological agent. (2)

(ii) sources. (2)

(iii) properties. (2)

(iv) the possible ill-health effects of exposure to E. coli 0157. (4)

(b) Posts on social media from swimmers who swam at Green Valley Lake in

the first two weeks of June, report that many have since been ill. The
swimmers are reporting stomach pain, but others are more unwell.

(i) Explain how these swimmers at Green Valley Lake have become ill. (15)

Note: Your answer must be based on the information in
supporting document 3.

Later in June, social media posts from some of the same swimmers

report members of their family, who had not been swimming, are now
also unwell.

(ii) Suggest likely explanations for this. (10)

(iii) Suggest reasons why the water sampling results for White Cliff

Cove differ significantly from those for Green Valley Lake in the
same two weeks of June. (4)

Note: Your answer must be based on the information in
supporting document 3.

(c) Suggest why the workers handling bathing water samples in Lab 4 are at

a lower risk of becoming ill than those people who swim in Green Valley
Lake. (6)

Note: Your answer must be based on the scenario only.