B4 Exam Q's Flashcards
A manufacturing process involves the use of
three organic solvents, exposure to which is
controlled by local exhaust ventilation (LEV)
and personal protective equipment. The LEV
system is regularly inspected and is subject
to thorough examination and testing on an
annual basis.
(a) Outline how the exposure of the process workers to solvent vapours could be assessed. 10 marks
(b) Outline how the data obtained could be used to determine if the exposure of the process workers to the solvents is adequately controlled. 10 marks
The outline could have been based around the 3 stage monitoring strategy as
described in HSG173 comprising an initial appraisal and then a basic and, if
required, a more detailed study.
The initial appraisal would consider:
the nature of the solvents involved, for example whether they were toxic,
harmful or irritant
the existing control measures such as the local exhaust ventilation and the
personal protective equipment provided
the health surveillance records
the known health effects of the solvents on the body and target organs
the volatility of the solvents at the process and/or workplace temperatures
the synergistic or additive effects of the three solvents
the frequency and duration of exposure and any WELs or relevant
biological guidance values.
As a result of this appraisal a decision could be taken on the necessity to
undertake workplace monitoring.
A number of sampling methods could be used including: static, personal,
passive, active, direct reading and laboratory analysis.
The equipment used would include stain and adsorbent tubes.
It would also be necessary to carry out biological monitoring to measure
what has actually been taken into the body rather than the airborne
concentration.
b.)
The data would enable comparisons to be made:
between actual exposures from personal sampling to the relevant WELs
(workplace exposure limits)
between the workplace monitoring results and in-house and industry
standards
between the results of biological monitoring and those of biological
monitoring guidance values (BMGV).
If personal monitoring exposure values were very close to the workplace
exposure limit (WEL) or one or more of the solvents was a carcinogen or
asthmagen, then further monitoring would have to be undertaken as advised
in HSG173 to confirm whether the solvent required further control to bring its
exposure to a level as low as is reasonably practicable.
A comparison would also have to be made between the performance of the
personal protective equipment provided against information contained in
material safety data sheets (MSDS) such as, for example, the chemical
resistance of gloves.
Finally the results of the annual examination and testing of the local exhaust
ventilation could be compared with its commissioning data and the
performance recommended in HSG258 to ensure the adequacy of its level of
control.
(a) Use the data below to calculate the 8-hour Time-
Weighted Average (TWA) exposure to a solvent
for a factory worker. Your answer should include
detailed working to show your understanding of
how the exposure is determined.
7
marks
08.00 – 10.30 Weighing ingredients 140
10.30 – 10.45 Break 0
10.45 – 12.45 Charging the mixers 100
12.45 – 13.45 Lunch 0
13.45 – 15.45 Cleaning equipment 25
15.45 – 16.00 Assisting maintenance staff 0
Assuming that exposure is zero during all other times.
To calculate the 8-hour time-weighted average, each time period
and exposure need to be multiplied together, then added including
the periods of zero exposure and the total divided by eight.
TWA =
(occupational exposure x exposure time) + (occupational exposure x exposure time) + … / 8
From the data provided this would result in the following calculation:
(140 x 2.5) + (0 x 0.25) + (100 x 2) + (0 x 1) + (25 x 2) + (0 x 0.25) / 8
= 350 + 0 + 200 + 0 + 50 + 0 / 8
= 600 / 8 = 75 ppm
Note: Remember to include the correct units with the answer. Care should be taken to reflect the period of time accurately as a fraction of an hour i.e. 15mins = 0.25 hours.
(a) Identify the circumstances when health surveillance would be considered appropriate according to Regulation 11 of the Control of Substances Hazardous to Health Regulations 2002 (COSHH). 2 marks
Circumstances where health surveillance would be
considered appropriate under Regulation 11 of COSHH
include:
where employees are exposed to a substance and
engaged in a process which are both listed in Schedule
6 of the Regulations
when there is an identifiable disease or health effect
associated with exposure to a hazardous substance and
a reasonable likelihood that the disease will occur
when there are valid techniques for detecting indications
of the disease or health effect which are of low risk to
the employee.
(b) Outline the arrangements and
facilities that an organisation should
put in place if they are to carry out
health surveillance in accordance
with the COSHH Regulations.
10
marks
Procedures / arrangements:
carrying out of medical surveillance for Schedule 6
substances by an appointed doctor on an annual basis
the completion of other health surveillance by a suitably
qualified person such as an occupational health nurse or
other responsible person under the supervision of a
registered medical practitioner
procedures for assuring the integrity of any samples taken
and their submission to an accredited laboratory informing an
employee if an adverse health effect or disease is identified
during the surveillance
the maintenance of up to date health records which should
be confidential, securely kept and retained for a period of
forty years
arrangements for employees to view their own health
records.
Facilities: Allocation of a suitable room which would ensure: privacy toilet and hand washing facilities sufficient space to store records.
(c) A small engineering company uses metal working fluids which can cause dermatitis and occupational asthma. Assuming the engineering company has the necessary arrangements and facilities referred to in part (b); outline the practical steps this company could take to meet its responsibilities under Regulation 11 of COSHH. 8 marks
Practical steps that the engineering company could take
include:
the appointment of a responsible person to oversee
health surveillance
undertaking regular skin inspections of the employees
and, at the same time, monitoring any breathing
problems they might be experiencing
referring those with breathing problems to occupational
health staff for medical assessment
training employees to undertake their own skin
inspections and advising them to report any problems
they might have with skin irritation or breathing
organising and administering the completion of
confidential questionnaires for skin and breathing issues
introducing a record keeping system for health
surveillance information
carrying out a regular analysis both of this information
and of sickness absence data.
Five employees work an 8 hour shift during which
they are exposed to a hazardous dust. The
employer has asked an occupational hygienist to
undertake monitoring of the employees’ personal
exposure to the hazardous dust.
(a) Describe how the hygienist should determine the employees’ long term personal exposure to the total inhalable hazardous dust. 10 marks
(b) The five employees were each
monitored for exposure to total
inhalable dust during the same 8
hour shift. Four of the results are
roughly equivalent but the fifth is
significantly higher.
Outline the possible reasons for this
discrepancy.
10
marks
The hygienist would be expected to monitor the exposure
throughout the eight hour shift and note both the work
undertaken during the monitoring and the time for which the
sampling was undertaken.
A gravimetric method should be used incorporating a
pump, a filter and an appropriate sampling head such as
a 7 hole, an IOM or a conical inhalable head with the
head being positioned in the breathing zone of the
employee.
The pump flow rate would be calibrated and noted as
would the volume of air in the sample collected, and the
filter weighed before and after the sampling to
determine any gain in the weight.
The concentration of total inhalable dust could then be
calculated by dividing the weight gain by the volume of
air with the result being expressed in mg/m³.
b.)
Reasons could have been divided into those to do with:
working environment and the tasks being performed
those resulting from possible failures with the monitoring
equipment
those connected with the individual employee.
In considering the working environment, there could have been
areas in the workplace which were not as well ventilated as
others, with possible problems with the local exhaust ventilation
provided.
As for the monitoring equipment for the individual concerned,
there could have been errors in the calibration of the pump flow, in
the timing of the air measurement, in the selection of the filter and
in weighing the filter at the end of the exercise, either because of
a misreading or because different and possibly uncalibrated
scales were used for the rogue sample.
The individual, too, could have had a part to play if they had
been particularly involved in the more dusty operations, had taken
fewer or shorter breaks than the other operators and had not
taken sufficient care with personal hygiene and had continued to
wear dusty overalls for long periods.
The possibility of deliberate sabotage could not be discounted.
(a) Give the meaning of the term
‘biological monitoring’.
2
marks
Biological monitoring is concerned with the measurement or
assessment of hazardous substances or their metabolites in
tissues, secretions, excreta or expired air.
(b) Outline the circumstances in which biological monitoring may be appropriate. 4 marks
Biological monitoring is a complementary technique to air
monitoring or sampling and can be used to determine:
if existing controls are adequate
when information is required on the accumulated dose in a
target organ
when there is a specified guidance value against which a
comparison might be made (such as in EH 40) when there is
significant absorption by non-respiratory routes
in circumstances when there is significant reliance on
personal protective equipment
where required by statute such as for example the Control of
Lead at Work Regulations.
(c) Outline the practical difficulties that an employer must take into account when introducing a programme of biological monitoring. 4 marks
Practical difficulties include:
obtaining the informed consent of those involved and
overcoming their concerns because, apart from the monitoring
required by statute, biological monitoring would normally be
conducted on a voluntary basis
the availability of suitable facilities or a location to carry out
the monitoring especially if this has to be done at the end of
the shift
the availability of specialists to carry out the monitoring, for
example, if blood samples are to be taken
maintaining the integrity of samples to avoid cross
contamination and ensuring there was no possibility of cross
infection
the fact that there are few guidance values available for
comparison
that exposure may be non-occupational
the cost involved in carrying out the exercise.
It is often necessary to monitor an employee’s
personal exposure to hazardous substances. Some of the measurement principles that can be used include gravimetric analysis, microscopy and chemical analysis.
For EACH of these measurement principles:
(a) Identify a type of hazardous substance for which it can be used AND suggest a typical workplace situation where such a measurement may be necessary. 6 marks
(b) Outline the type of equipment AND the methodology used to determine the employee’s personal exposure to the hazardous. 14 marks
The gravimetric method for measuring personal exposure
to hazardous substances may be used for measuring total
inhalable or respirable dusts for instance in a
woodworking workshop or in the manufacture of chemicals.
Microscopy would be used for the measurement of fibres
such as following the accidental disturbance or planned
removal of asbestos.
Chemical analysis is used in the measurement of gases,
vapours and fumes in workplaces such as laboratories or
those involved in the manufacture of chemicals.
b.)
With the gravimetric method:
A filter attached to a pump is used.
There are three main types of sample head depending on the type of dust being
determined. These are: the multi-orifice (7 hole) sampler, the IOM inspirable dust
sampler or the cyclone head.
The filter is weighed before and after sampling.
The concentration, expressed in mg/m³, is determined from the weight gain and the
volume of air used.
With microscopy:
A membrane fitted on an appropriate sampling head such as a cowl is attached to a
pump.
After sampling is completed, a phase contrast microscope is used to count the fibres.
The number of fibres in a known proportion of the sample is calculated and extrapolated
to the whole sample with the result being expressed as fibres per millilitre of air (f/ml).
With chemical analysis:
A tube or sampling head with a filter impregnated with an adsorbing material such as
charcoal, tenax or silica is attached to a pump.
After sampling it is desorbed and analysed in a laboratory.
The analysis techniques which can identify both the chemical and its concentration
include mass spec or IR spectrometry and gas chromatography.
Concentrations are expressed in parts per million or milligrams/m³.
General points associated with each monitoring method include the necessity:
to calibrate the pumps used
to draw a known volume of air through the filter or tube
to take a number of samples to minimise errors in measurement
to ensure the sampling head was placed in the breathing zone
to use the appropriate methods (MDHS)for determining the hazardous substances.
Methanol (an organic solvent) is being used in the production of a specialist coating.
An employee’s measurement of exposure to methanol varies throughout their 8-hour working day. The results of measurement
of their exposure are as follows:
Measuring out and adding methanol 15 minutes 320
Adding other components to the mix 1 hour 100
Supervision of mixing and decanting 2 hours 125
Clean down of equipment using solvents 3 hours 150
Assume that exposure is zero at all other times
(a) Calculate the 8-hour Time-Weighted Average (TWA) exposure to methanol for the employee. Your answer should include detailed working. 8 marks
TWA = (occupational exposure x exposure time) + (occupational exposure x exposure time) + … / 8
= (320 x 0.25) + (100 x 1) + (125 x 2) + (150 x 3) / 8
= 80 + 100 + 250 + 450 / 8
= 880 / 8 = 110 ppm
Note: Remember to include the correct units with the answer. Care should be taken to reflect the period of time accurately as a fraction of an hour i.e. 15mins = 0.25 hours.
Information relating to methanol in EH40 Workplace Exposure Limits is as follows:
Substance
Methanol
CAS Number
67-56-1
Long-term exposure limit
(8-hour TWA limit reference period)
200ppm 266mg/m3
Short-term exposure limit
(15-minute reference period)
250ppm 333mg/m3
Comments
Sk
R11, 23/24/25,
39/23/24/25
(b) Outline the following terms:
(i) Chemical Abstract Services
(CAS) number
2
marks
(ii) Short-term exposure limit (15-
minute reference period)
2
marks
(i) A CAS number is a unique number, recognised internationally,
which is assigned to identify a particular chemical, thus avoiding
confusion between chemicals with similar names.
(ii) A short term exposure limit (15 minute reference period)
represents the maximum permissible exposure by inhalation in a
15 minute period. This is relevant where substances may cause
adverse and acute effects after a brief exposure. For substances
with no assigned short term exposure limit (STEL), it is usual to
apply a figure of three times the long term exposure limit (LTEL)
as a guideline.
c) Using your results from part
(a), the original exposure
information in Table 1 and by
selecting the relevant data
from Table 2, explain what
actions might be required by
the employer in order to
comply with the Control of
Substances Hazardous to
Health (COSHH)
Regulations 2002.
8
marks
The Time Weighted Average (TWA) calculated in part (a) needed to be
applied to the additional information contained in Table 2, to determine
whether the employer needed to take any action to comply with the
requirements of the COSHH Regulations of 2002.
The conclusion should have been that the long term exposure (calculated
as 110ppm) did not exceed the WEL (given as 200ppm) and it would
therefore be sufficient to continue with, and monitor, the existing control
measures.
However, the short term exposure limit (of 250 ppm) was exceeded during
the time when the employee was measuring out and adding the methanol
(320 ppm) and consequently further control measures would be required
for that part of the process. These might include, for example:
substitution with a less hazardous substance
automatic dispensing of the solvent
installing local exhaust ventilation or improving its efficiency if already
installed
wearing respiratory protective equipment to reduce inhalation and
personal protective equipment to avoid splashing to the skin since the
reference to SK indicates that the substance may enter the body
through the skin
Measuring the level of exposure to other components and comparing
them with their respective WELs, and investigating any possible
synergistic or additive effects, might also be a good idea.
A manufacturing process involves the use of
a solvent which has a Workplace Exposure
Limit (WEL).
(a) Explain what is meant by the term WEL and how it relates to the term “adequate control” as defined in the Control of Substances Hazardous to Health (COSHH) Regulations 2002. 5 marks
(b) Outline a range of methods and equipment that could be used to measure the personal exposure of the process workers to this solvent. 7 marks
(c) Exposure of the process workers to this solvent is controlled by local exhaust ventilation (LEV) and personal protective equipment (PPE). The LEV system is regularly inspected and is subject to thorough examination and testing on an annual basis.
Using results from personal exposure measurements and information relating to the control measures in use, outline how you could determine if the process workers’ exposure to this solvent is adequately controlled.
8
marks
A WEL is the maximum concentration of an airborne substance averaged over a
reference period (either a short term exposure limit of 15 minutes, or a long term
exposure limit of 8 hours), to which employees may be exposed by inhalation.
‘Adequate control’ is only achieved if the WEL is not exceeded and the principles
of good practice are met. There are also additional requirements for carcinogens,
mutagens and asthmagens.
b.)
Personal monitoring is used to establish the concentration of an airborne
substance within the employee’s breathing zone, which is generally accepted to
be no more than 30cm from the mouth. Personal monitoring sampling apparatus
to measure gas or vapours in air, consist of: a sampling head with a filter
impregnated with adsorbing material (charcoal or silica, for example), positioned
in the wearers breathing zone, connected by tubing to a calibrated, portable flow
plump. Once the monitoring (over a specified period) is complete, analysis via
spectrometry, spectroscopy or chromatography will identify the chemical and its
concentration.
Note: Relevant MDHS documents on the HSE website (Methods for Determining
Hazardous Substances) describe the methodologies for measuring exposure to
solvents. You are not expected to have detailed knowledge about the
name/number of these MDHS documents.
c.)
Comparing the results of personal exposure monitoring with
the relevant Workplace Exposure Limit would help determine
if the workers exposure to the solvent is adequately
controlled.
The results of LEV testing compared with the commissioning
data for the LEV system could indicate a drop in LEV
performance over time, which may result in the control of
exposure deteriorating.
Comparing personal exposure monitoring results to PPE or
RPE specifications would also be useful in determining their
effectiveness as a control measure.
