B4-MONITORING AND MEASURING

Question 1

What specific form of hazardous substance does EH40 lay down WELS for?

Answer 1

The WELS in EH40 are concerned with inhalation of airborne contaminants. Therefore, the form of the substance must be one that can become airborne, dust, fibres or fumes, mists and vapour or gas

Question 2

What is the definition of “workplace exposure limit”

Answer 2

Workplace exposure limit is defined as “the maximum concentration of an airborne substance, average over a reference period, to which employees may be exposed by inhalation”

Question 3

Describe the criteria for setting a WEL

Answer 3

WELs are set on the recommendation of the Advisory Committee on Toxic Substances (ACTS).

The First step in deriving a WEL involves an assessment of the toxicology of the substance in order to identify the potential for adverse health and safety effects and to understand the dose/response relationship

If a NOAEL is identified, then this value is used as a starting point for determining the highest level of exposure at which no adverse health effects are predicted to occur in an occupational context

The final step in the process is to determine the actual levels of exposure that are being achieved in the workplace. if these actual exposure levels are below the level identified by ACTS, or if ACTS believes that achieving lower level is reasonably practicable, then ACTS will set the WEL at this level.

However, for certain substance, it is not possible to set a NOAEL. In these cases, ACT will set a WEL at a level commensurate with good occupational hygiene practice. In setting this level, ACTS will consider the severity of level health effects and the cost and efficacy of the possible control solutions. Wherever possible, the WEL is not set at a level where there is positive evidence of adverse effects on human health.

Question 4

State the four stages of occupational hygiene?

Answer 4

• Recognition/identification of the hazard-identifying those factors that may cause harm
• Measure of the hazard/extent of exposure-determining who is affected and by how much.
• Evaluation against recognised standards-making a judgement on the risk posed
• Control-putting measures in place to reduce or eliminate the risk posed.

Question 5

Outline the monitoring strategy described in HSG173

Answer 5

Initial appraisal-helps establish the need for, and extent of, exposure monitoring. it is conducted in two stages-information gathering and simple qualitative tests. Depending on the conclusions drawn,a basic survey may then be needed. This estimates an employee’s personal exposure using crude methods. The conclusion of this stage will enable you to decide if a detailed survey is required. The detailed survey is conclude in cases such ass highly variable exposure and involves more detailed monitoring and analysis. In addition, there are the stages of re-appraisal (to see if changes have had the desired effect) and routine monitoring (to ensure controls remain effective) described in HSG173.

Question 6

Describe the gravimetric method for the analysis of inhalable dust.

Answer 6

The sampling effect equipment (sampling train) consists of an air pump, connecting hose and sampler (containing a pre-weighed filter):

• Clean and load the sampler with a pre-weighed filter or cassette.
• Fit the sampler to the pump. Run the pump to stabilise airflow and then check and adjust flow rate using the flow meter.
• Attach the sampling train to the operator, not more than 30cm away from the nose-mouth region
• Record the time at the start of the sampling period and check, record and re-adjust the flow rate as necessary at the end of each hour
• At the end of the sampling period, note the time and remove the filter for re-weighing.
• Re-check the flow rate using the flow meter.
• Once the weight of dust collected on the filter is known,a simple calculation is carried out to give the weight of dust per cubic metre of air (mg.m3)

Question 7

State the limitations of stain tubes as a method of quantifying airborne contaminant

Answer 7

• Tubes with incorrectly broken ends may not give correct flow rate.
• Bellows action and the number of strokes are critical in ensuring that the correct volume of air is drawn through the tube.
• Tubes may be cross-sensitive to substances other than the one being analysed.
• Tubes give inaccurate readings at non-standard temperatures and pressures that have to be corrected for.
• Tubes have limited shelf life
• Measurements obtained are inherently inaccurate so the margin of error of the tube type must be taken into account.
• Hand-operated stain tube system are capable of only a point-in-time or grab sample.

Question 8

State the specific criteria that have to be met before health surveillance becomes a legal requirement.

Answer 8

These criteria are outlined under regulation 6 of the Management of Health and Safety at Work Regulations 1999:

• There Is an identifiable disease or adverse health condition related to the work concerned.
• Valid techniques are available to detect indications of the disease or condition.
• There is a reasonable likelihood that the disease or condition may occur under the particular conditions of work
• Surveillance is likely to further the protection of the health and safety of the employees to be covered.

Question 9

State four sets of regulations that contain a requirement for health surveillance.

Answer 9

• Management of Health and Safety at Work Regulations 1999
• Control of Substances Hazardous to Health Regulations 2002
• Control of Lead at Work Regulations 2002
• Control of Asbestos Regulations 2012

Question 10

Who can conduct medical surveillance as opposed to health surveillance?

Answer 10

Medical surveillance is a statutory requirement under COSHH, CAR and CLAW and requires surveillance by a ‘relevant doctor’ is a:

• medical inspector of the HSE’s Employment Medical Advisory Service, or
• doctor appointed by the HSE.

Question 11

What is the minimum requirement for health surveillance and the keeping of a health record?

Answer 11

The minimum requirement for health surveillance is that a health record is created for each employee exposed or potentially exposed to the hazard in question. That health record is simply a record of the fact that exposure has, or is liable to have, occurred.

The minimum requirements for record keeping in a health record are:

• Surname
• Forenames
• Sex
• Date of birth
• Permanent address
• N.I number
• Date started present job
• An historical record of jobs involving exposure to hazards for which health surveillance is required during the current spell of employment.

Question 12

What is the difference between a health record and a medical record?

Answer 12

• A health record is a record of the conclusions of clinician (such as an OH doctor) on health surveillance results. It does not contain clinical information and so is not medically confidential. It can therefore be viewed by the employer.
• A medical record is created by a clinician, contains clinical information and is medically confidential. Therefore, it cannot be viewed by the employer without the authorisation of the individual concerned.

Question 13

What are the legal requirements for the keeping of health records?

Answer 13

Health records must, as a minimum, be kept for the length of time that a worker remains working with the specific hazard that required for the keeping of the record.

However, in most instances, there will be specific legal requirements on the length of time that the record must be kept: COSHH, CLAW and CAR state 40 years

Health records always relate to individuals and are therefore subject to data protection legislation. They must only be used for their intended purpose, must be stored securely and must be destroyed once no longer required.

Individuals have a right of access to their health records.

Question 14

What does the term ‘biological monitoring’ mean?

Answer 14

Biological monitoring is the measurement of a substance of its metabolite (substance formed when the body converts the chemical) in a biological fluid (breath, urine or blood).

An example of this is monitoring urine for the presence of isocyanates.

Question 15

What are the biological limit values for lead?

Answer 15

The action level for inorganic lead is based on the level of lead in blood:

• 25ug per dl (100ml) of blood for women of reproductive capacity
• 50ug per dl for young person (under 18).
• 60ug per dl for other employees

• The suspension level for lead is based on the level in urine:

• 25ug Pg/g creatine for women of reproductive capacity
• 110ug Pb/g creatine for other employees.

Question 16

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)

Answer 16

Adopt the three stage-monitoring strategy as described in HSG173 comprising an initial appraisal and then a basic and, if required, a more detailed study.

An initial appraisal helps establish the need for, and extent of, any exposure monitoring. It helps you decide if you need more information, like actual monitoring data and who/when to monitor. Information is gathered on substances (identify, health hazards, volatility, possible synetgystic effects between the solvents, etc), activities/task, exposure frequency/duration, existing controls, applicable exposure limits (WELS and also consideration of any applicable BMGVs) and any health surveillance data. Simple qualitative methods are all that is required, e.g. smoke tubes (which show air flows); smell (unreliable); dust (makes fine dust/mist visible and identifies leaks/emission sources).

Basic survey is what you do if your initial appraisal is inconclusive and you need more information to help you decide, i.e. the extent of the risk is uncertain. The basic survey is more detailed than initial appraisal appraisal and attempts to estimate employees’ personal exposure and the effectiveness of the controls. In this case, you would focus on the staff most likely to be exposed and the worse case sends scenarios (suck as peak exposure times). You could then use relatively crude, semi-quantitative methods to estimate their ‘worst case’ personal exposure (using direct reading instruments such as stain tubes and photoionisation dectectors) or measure it using more rigorous, quantitative active or passive methods (bubblers, absorption tubes etc that need to be sent off to a laboratory for analysis such as by gas chromatography). Both personal and static monitoring might be used.

The detailed survey is used for complex cases where the basic survey leaves you with some doubt that things are normally well controlled (or as well controlled as they should be!). For example, exposure between employees may highly be variable; you may be dealing with carcinogens, mutagens or respiratory sensitisers (where a higher standard applies); estimates from initial appraisal and basic surveys suggest you are working very close to the WEL or you need more evidence/data to justify the exposure of putting in extra controls.

Monitoring techniques would be similar to those already used in initial appraisals and basic surveys but would be a more detailed look at exposure patterns, more extensive quantitative personal monitoring (larger numbers of samples at different times,etc). You might even need to do some biological monitoring to help asses amounts taken in by those exposed.

Question 17

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.

(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)

Answer 17

Any TWA personal monitoring data would be compared with any applicable WELS, in-house standards or industry standards.

Similarly, any workplace (static) monitoring could be compared with in house/industry standards.

The same is also true of any biological monitoring- comparison with the BMGV (if one exist).

Depending on how they compare (e.g. if very close to WEL) or of the solvents were asthmagens or carcinogens (ALARP principle applies), then further monitoring and/or controls might be needed.

You would need also to compare requirements of PPE (such as chemical resistance, breakthrough time for gloves) identified on SDS (and other sources) to performance of available/existence PPE supplied.

Comparison also of LEV monitoring/test/inspection results against its design performance (and performance recommendations, such as in HSG258) to see whether its performing as designed/required.