IB4 Flashcards
(a)
Outline what is meant by inhalable dust.(2)
(b)
Outline the equipment and method required for personal sampling of inhalable rubber dust.(7)
Inhalable dust: Inhalable dust is the fraction of (a)
airborne dust that enters the nose and mouth during breathing, and is therefore available for deposition in the respiratory tract
One of the defining characteristics of dust is the diameter of the particles, usually given in microns, µm (1 micron = 1/1,000 of a millimeter or 10-3mm). Inhalable dust particles can be as large as 100µm or more
(b)
The sampling equipment (sometimes referred to as a ‘sampling train’) consists of an air pump, connecting hose, sampler (sampling head containing a filter), and flow meter:
• Air pump - must meet certain minimum standards and is usually a unit that can be worn by a worker on a belt or in a pocket and is capable of drawing air at a steady fixed rate for 4-8 hours.
• Hose - simply a clear plastic tube for connecting the air pump to the sampler.
• Sampler - a small filter holder that can be attached to the worker close to their breathing zone; usually clipped to clothing at the collar bone.
• Flowmeter - used to check the flow rate of the sampler train before and after use.
The type of sampler used to measure inhalable rubber dust is IOM inhalable dust sampler
Method of Use
–Stabilise the airflow at the required rate.
–Fit the sampling head with a clean, pre-weighed filter.
–Attach the sampling head to the operator, near the nose-mouth region.
–Record the time at the start of the sampling period and check the flow rate as necessary.
–At the end of the sampling period, note the time and remove the filter for re-weighing.
–Volume of air passing through the filter is calculated by multiplying the flow rate (cubic metres per minute) by the sampling time (minutes).
–Weight gain (mg) of the filter, divided by the volume sampled, gives the average dust concentration in milligrams per cubic metre of air (mg/m3).
The following legally enforceable long-term exposure limits (8-hour time weighted average (TWA)) apply
Rubber process inhalable dust 6mg/m3
Rubber fume 0.6mg/m3
-Rubber process inhalable dust 12hours 3mg/m3 -Rubber fume 12hours 0.5mg/m3
(c)
Calculatethe 8-hour TWA exposure to the process operators from BOTH the rubber process dust and the rubber fume.
(d)
Comment on the significance of your answers calculated in part (c) in terms of exposure and possible future action.(5
(c)
123/8 = 4 mg/m
120.5/8=0.75 mg/m
(d)
it is evident that the value (4mg/m3) to which employee are exposed is below legal limit ( 6mg/m3) , but Rubber fume value has exceeded the legal limit (0,6mg/m3), Additional controls are therefore required; e.g. substitution, automation, LEV, PPE including RPE
Also an investigation into current controls and work practices is needed
It would also be necessary to undertake additional measurements (to investigate why LTEL is exceeded and gather more data, not only to establish accuracy but also to explore exposure patterns during other operations). There will also be a need for routine monitoring to make sure that any additional controls put in place are having the desired effect.
a) Explain what the term Occupational Exposure Limit (OEL) means in practice. (3)
(b) Calculate, using the data below, the 8-hour TWA exposure to flour dust of a bakery worker. Include detailed working to show how the exposure is determined.
task Weighing ingredients , Wokring period 2,5 , exposure 20 mg/m3
(a)
The definition of OEL is the maximum concentration of an airborne substance, averaged over a reference period, to which employees may be exposed by inhalation. It is usually expressed in units of mg/m3 or ppm. In practice, this means that for most substances assigned a OEL, the exposure of employees to the substance assigned the OEL must be below the OEL on a time weighted average basis. Two different reference time periods are used and the OELs are expressed in terms of these time periods - either Long Term Exposure Limits (LTEL) measured over an eight hour period, or Short Term Exposure Limits (STEL) measured over 15-minute periods. In certain instances exposure to the substance must be below the OEL to the greatest extent reasonably practicable. Where possible OELs are set below the ‘no observed adverse effect’ level.
b)The TWA exposure to flour dust can be calculated as:
=T1xC1+T2xC2+T3xC3/8
= (50 + 60 + 50 + 0 + 0) / 8= 160 / 8= 20mg/m3
= 20mg/m3
(a) Outline the circumstances in which monitoring of employee exposure to hazardous substances should be carried out. (5)
(b) Identify the information that should be included in a record of monitoring to ensure that the record is ‘suitable’. (3)
(c) Identify the periods of time for which records should be kept, and the factors that determine the period of time.(2)
(a)
When failure or deterioration of the control measures could result in a serious health effect, either due to toxicity of the substance or because of the extent of the potential exposure.
When measurement is necessary to be sure that the OEL is not exceeded.
When necessary as an additional check on the effectiveness of any control measure provided.
(b)
The records should contain details as to when the monitoring was done (dates, times and durations of tests); where and/or on who the monitoring was done (the locations where samples were taken, the names of the individuals concerned and the operations in progress at the time) and the results (calculated exposures).
(c)
The length of time for which records have to be kept depends on the type of measurement taken. For individuals (personal dosimetry) the period is for at least 40 years, in any other cases (e.g. static sampling) for at least five years.
(a) Outline the meaning of the phrase ‘biological monitoring’ and identify the circumstances when biological monitoring might be appropriate.
(b) Review the practical difficulties that an employer may have to consider when introducing a biological monitoring programme.
(a)
Biological monitoring involves measurement/assessment of workplace agents (or their metabolites) in tissues, body fluids (blood/urine) or breath. For example, a worker exposed to isocyanate solvent might provide a urine sample that can then be analysed to indicate the workers total exposure to isocyanate. It is indicative of the absorption into the body by all routes, not just by inhalation (which is the thrust of OELs). It compliments air monitoring and helps determine adequacy of existing controls.The circumstances when biological monitoring might be appropriate would be: when absorption via entry routes other than respiratory is significant AND there is a heavy reliance on PPE as a control measure AND when valid monitoring techniques exist AND when a reference/guidance value exists
(b)
Apart from the case of biological monitoring as part of statutory medicals, submission to testing is usually voluntary. Since it is somewhat invasive, there may be a reluctance/concern to consent - so this needs to be tackled. Also the availability of suitable facilities and specialists to carry out the tests (nurses, etc.) may present practical problems. Sample integrity (cross-contamination) is another important issue that must be tackled, since positive test results can have dramatic consequences for the employer and employee alike. Also there are relatively few available guidance values (for interpretation of result); not to mention the costs involved
Stonemasons are exposed to irritant limestone dust in the course of their work. Limestone dust has been assigned an Occupational Exposure Limit (OEL).
(a) Explain the term Occupational Exposure Limit (OEL) in this context. (3)
(b) Stonemasons’ work involves both cutting and finishing of limestone. Explain the factors to be considered when undertaking a suitable and sufficient assessment of the risks from their exposure to limestone dust. (11)
(c) Given that stonemasons are required to work both in a workshop and out on site, review a range of control measures that would be suitable in each of these situations
(a)
Occupational Exposure Limit is defined as “the maximum concentration of airborne contaminant (limestone dust in this case), averaged over a reference period, to which employees may be exposed by inhalation”. It would be measured in mg/m³. There would be a long term (8 hours, a typical work shift) exposure limit and there might be a short term (15 minutes) limit as well (if none is given then 3 LTEL is used). The OEL must not be exceeded and principles of good hygiene should be followed for control to be considered adequate.
(b)
The hazardous nature of the limestone dust, which causes irritation to skin, eyes and respiratory tract, must be considered. The numbers of workers exposed and the level and duration of their exposure must also be taken into account. There may be individual susceptibility to the irritant effects of the dust within the working populations (e.g. asthma sufferers might be sensitive to the dust). The possible routes of entry must be thought about; in this case it would be principally inhalation into the lungs, with some potential for ingestion into the gastrointestinal tract. The dust particle sizes created by work processes would be important, as this determines the deposition site in lungs. Another set of factors to consider would be how the work is carried out. Power tools will almost certainly be used, so what is their nature, what controls do they already have built into them and how are they used? For example, what position does an operator need to adopt when using certain tools, do they have to stand above or in the line of ejected dust plumes? The effectiveness of existing controls would have to be evaluated during the assessment process. Any airborne contaminant monitoring and health surveillance results would be examined to give information about current exposures and existing health effects.
(c)
There are a number of control measures that might be adopted within this type of workplace. Some of these might be appropriate for indoor workshops, some for outdoor work and some can be applied to both instances. General workspace ventilation of indoor workshops would be necessary to dilute low levels of dust down to acceptable levels. An LEV system would have to be fitted to any processes generating dust at a point source (e.g. stone cutting), unless damping down techniques were used to eliminate dust generation (this would be the case at most indoor stone cutting operations). Tools would need to be kept sharp to minimise the amount of dust generated and would either have in-built extraction or damping spray mechanisms. Suitable RPE would have to be selected and used with some attention paid to user comfort, efficiency, fit, and compatibility. Personal PPE might be particularly important in outdoor workplaces where damping down and LEV are less likely to be practical. Other PPE such as eye, hearing and skin protection(e.g. goggles, ear plugs, gloves and overalls) may also be necessary, depending on the operation being carried out. General hygiene measures, such as providing clean rest and food preparation areas, would have to be supplied. Hand wash facilities would also have to be supplied adjacent to these areas
In a shoe factory, workers use a range of solvents.
(a) Outline the issues that should be taken into account and the information that could be examined when undertaking an assessment of the health risk assessment of worker exposure to these solvents.
(b) Describe a monitoring strategy that would be appropriate for the monitoring of actual worker exposure to the solvent vapours.
(c) Explain how any data obtained during monitoring assessments should be interpreted so as to determine the acceptability of worker exposures and the adequacy of the control measures that are already in place.
(a) Information on the solvents themselves would be of paramount importance. What is their chemical nature, what health effects do they have, what target organs do they affect, are there any workplace exposure limits, might there be synergistic effects between one solvent and another or a solvent and other chemicals present in the workplace, what routes of entry do the solvents take in order to make their way into the body? Information sources that would need to be consulted in order to determine this information would include: the ACoP, guidance note EH40 containing the table of OELs, HSG173 outlining basic monitoring strategies and of course the SDSs for the solvents themselves. Other issues/factors that would also need to be considered would include the actual working methods employed, employee exposure patterns, the adequacy of existing controls, the need for monitoring and health surveillance.
(b)
HSG173 describes a three-stage approach to a monitoring strategy. In this case the strategy might consider people/areas to monitor, timing and duration of monitoring and how to monitor. There would need to be some basic data so that an initial evaluation of exposure levels might be made. This initial evaluation might make use of simple grab-sampling data (stain tubes or other methods), and other techniques might be used, to get quantitative data on exposures (including personal monitoring and biological monitoring). There would also be the need to consider the analysis methods to be used. This would require reference to standardised methods.
(c)
The interpretation of data obtained would require a comparison of actual assessed exposures with exposure standards. Namely Occupational Exposure Limits (OELs). This should be done taking into account of presence of mixtures and any additive effects. Any Biological Limit Values that exist (e.g. listed in EH40) should also be considered. The results of any environmental monitoring or personal dosimetry carried out should be compared to the OELs. Any measurements of LEV performance tests can be used to assist in the evaluation. PPE data might also be useful (such as glove breakthrough times which would be very appropriate if gloves were used to protect the hands from solvent contact). Finally, the result of any health surveillance carried out might be used to contribute to the valuation process.
Methanol (an organic solvent) is being used in the production of a specialist coating. An operative’s measurement of exposure to the methanol varies throughout his 8-hour working day. The results of the measurement of his exposure are as follows:
Task undertaken by operative:
- Measuring out and adding methanol 15m, 280ppm(exceeed)
- Adding other components to the mix 1h, 90 ppm.
- Supervision of mixing and decanting 2h, 150 ppm
- Clean down of equipment using solvents 2h,170ppm.
(a) Calculate the 8 hour Time-Weighted Average (TWA) exposure to methanol for the operative. Your answer should include detailed working to show you understand how the exposure is determined.
(b) Information relating to methanol in EH40 Workplace Exposure Limits is as follows:
STEL(15mn)= 250ppm
LTEL(8hours)= 200ppm
Table (2) page(84) revision guide IB.
(c)Describe how the personal exposure of the operative to methanol can be measured.
(a)The 8-hour TWA exposure for the operator is calculated as:(Convert the 15 minute time slot into hours (i.e. 0.25 hour) and then do the TWA calculation)((280 0.25) + (90 1) + (150 2) + (170 2)) / 8 = (70 + 90 + 300 + 340) / 8 = 800/8 = 100ppm (b)
Key things to note are that the calculated 8-hour TWA exposure does not exceed the LTEL (in table 2).
However, the STEL (table 2) is exceeded during the first 15 minute measuring stage (table 1). This first time slot is 15 minutes long (matching the 15 minute reference period for a STEL) and the exposure level is measured at 280ppm. The STEL given in table 2 is 250ppm. Therefore the STEL has been breached. It is not possible to determine if the STEL has been exceeded during any other times over the working day, as all other task durations are for a period of much longer than 15 minutes (namely 1 hour and greater).
Additional controls are therefore required; e.g. substitution, automation, LEV, PPE including RPE. Note that gloves should be worn as a matter of course because of the “SK” comment - skin absorption is a significant exposure route. It would also be necessary to undertake additional measurements (to investigate why STEL is exceeded and gather more data, not only to establish accuracy but also to explore exposure patterns during other operations). There will also be a need for routine monitoring to make sure that any additional controls put in place are having the desired effect
(c) The operator’s personal exposure to methanol would be quantified by the use of the standard method. A sampling head would be placed close to the breathing zone. There would be a sorbent material in the sampler such as activated charcoal or silica. Either an active (calibrated air pump) or passive sampler would be used. Details of the precise method would be found in the relevant standard. The methanol is absorbed in the sorbent in the sampler and then needs to be desorbed in an accredited lab and analysed (typically by Gas Chromatography). Methanol quantities can then be calculated and methanol concentration within the operators breathing zone can be estimated by reference to the sampling pump rate and the duration of the sampling period.
(a) Use the data below to calculate the 8 hour Time-Weighted Average (TWA) exposure to flour dust for a
bakery operative. Your answer should include detailed working to show your understanding of how the
exposure is determined
2h30 weighing ingredients 14 mg/m3 15mn Break 2h Charging mixers 10mg/m3 1h lunch 2h Cleaning the equipment 2.5mg/m3
Assume that exposure is zero during break times and lunch time and that a legally enforceable Exposure Limit (8 hours TWA) of 10mg/m3 is applicable to flour dust
(b) The bakery changes the working patterns to the extent that the operative now only charges the mixer. In
addition, shift times have been altered to a 10 hour shift, which includes a 1-hour lunch break where the
exposure is assumed to be zero. Using the relevant data above, re-calculate the equivalent 8-hour TWA
exposure in their new role AND comment on the legal implications of this change.
(a) Exposure calculations: Period 1 (weighing) = 2.5 × 14 = 35mg.m-3 Period 2 (break) = 0.25 × 0 = 0mg.m-3 Period 3 (charging) = 2 × 10 = 20mg.m-3 Period 4 (lunch) = 1 × 0 = 0mg.m-3 Period 5 (cleaning) = 2 × 2.5 = 5mg.m-3 Period 5 (maintenance) = 0.25 × 0 = 0
= 35 + 0 + 20 + 0 + 5 + 0 = 60mg.m-3
Total exposure during shift
Total shift time = 8 hours
exposure as an 8 hour TWA = 60/8hr =7.5mg.m-3 (which is below the legal exposure limit)
Total shift time = 8 hours, hence exposure as an 8 hour TWA = 60/8hr =7.5mg.m-3
(which is below the legal exposure limit)
(b)
Exposure calculations:
Activity 1 (charging the mixer) = 9 × 10 = 90mg.m-3
Activity 2 (lunch) = 1 × 0 = 0mg.m-3
Total exposure over 10 hour shift = 90mg.m-3
Exposure calculated as an 8 hr TWA = 90/8 = 11.25mg.m-3
When this new exposure is compared to the legal limit of 10mg.m-3, it is clear that the operator is now exposed to more than the legal limit and as such the employer is failing to adequately control exposure to flour dust.
Operators use a range of solvents in a manufacturing process.
Describe a monitoring strategy that could be used to measure the exposure of the operators to solvent vapours.
The first stage would take the form of an initial appraisal with the objective of determining if and to what extent more detailed monitoring of workers’ exposure would be required. It is basically an exercise to gather information on matters such as the activity being carried out, the substances in use, the duration of exposure, relevant exposure limits, and the nature and use of any existing controls, which would inform the decisions to be made on who, where, when, for how long and what to monitor. If the initial appraisal were to indicate that there would be significant exposure, a basic survey would be necessary.
A number of measuring methods could be used ranging from the
use of a pump with adsorption and/or stain tubes to direct reading instruments. It might also be necessary to take samples either on a personal or static basis, and either for the short or long term with the samples being analyzed using a method such as gas chromatography or mass spectroscopy. Finally, biological monitoring could be used to measure what has actually been taken into the body rather than the airborne concentration.
(a)What is the action required when STEL and LTELS aren’t exceeded
(b) There is a concern that exposure to a mixture of these two liquids might increase the risk to workers.
Consider why this might be a valid concern.
no further action is necessary and the
maintenance of existing controls as appropriate.
• One compound may simply add to the toxicity of another (additive effect).
• One compound may enhance the toxicity of the other so that the
resultant toxicity is greater than the sum of the individual toxicities
(potentiation or synergy).
Outline how an occupational hygienist should determine a worker’s long
term personal exposure to total inhalable hazardous dust.
(a) by using sampling equipment (sometimes referred to as a ‘sampling train’)
The type of sampler used to measure inhalable hazardous dust is IOM inhalable dust sampler
Method of Use
–Stabilise the airflow at the required rate.
–Fit the sampling head with a clean, pre-weighed filter.
–Attach the sampling head to the operator, near the nose-mouth region.
–Record the time at the start of the sampling period and check the flow rate as necessary.
–At the end of the sampling period, note the time and remove the filter for re-weighing.
–Volume of air passing through the filter is calculated by multiplying the flow rate (cubic meters per minute) by the sampling time (minutes).
–Weight gain (mg) of the filter, divided by the volume sampled, gives the average dust concentration in milligrams per cubic meter of air (mg/m3).
Workers cutting and finishing stone are exposed to silica dust.
Outline factors to be considered when carrying out a ‘suitable and sufficient’ assessment of the risks
from exposure to silica dust.
The hazard classification of silica dust
The health effects associated with silica dust exposure(it can cause silicosis, a form of pneumoconiosis, or scarring of the lungs, and associated with an increased risk of lung cancer)
The likely routes of entry(in this case, inhalation)
The particle size distribution of airborne silica dust(to determine if the dust is inhaled or respirable )
The chemical for of the silica (different WELs exist for different forms, with crystalline-free silica being the most hazardous)
The number of workers exposed and the duration and frequency of their exposure, which will determine their actual levels of exposure(their dose)
The Workplace Exposure Limits (WELs) that may apply to silica- which will be expressed both as long-term exposure Limits(LTELS) and short term Exposure Limits(STELS)
The nature of the work activity since some activities will create more airborne dust than others and in particular, the use of power tool during work
Any existing control measures that be available and in use, such as local exhaust ventilation systems and dust suppressions systems (e.g. waters jets used to lubricate some cutting) or Respiratory Protective
Equipment(PRE)
The concentration of any airborne dust clouds that are created, as measured by direct instruments by personal or static sampling. This can be used in combination with the duration of exposure to determine the personal exposure of works to silica.
The occupational health department at the organisation needs to decide whether to carry out health surveillance for workers exposed to this solvent.
(i) Outline the purposes of health surveillance.
(ii) Identify ONE type of health surveillance that may be appropriate for the workers using this solvent.
(iii) Other than health surveillance, identify FOUR functions that may be carried out by an occupational health service in a large manufacturing organisation.
(i)
detecting ill-health effects at an early stage, so employers can introduce better controls to prevent them getting worse
providing data to help employers evaluate health risks
enabling employees to raise concerns about how work affects their health
highlighting lapses in workplace control measures, therefore providing invaluable feedback to the risk assessment
providing an opportunity to reinforce training and education of employees (eg on the impact of health effects and the use of protective equipment)
(ii) lung function tests, as simple as routine skin checks by a responsible person to identify early signs of dermatitis
(III)
Giving victim immediate medical assistance following an accident and
Assisting in the training and assessment of first aid personnel;
Carrying out specific risk assessments with respect to
o the vulnerability of certain groups such as pregnant women and young persons,
o new processes such as those involving potential ergonomic hazards such as manual
handling, and
Carrying out pre-employment medical examinations and health screening
Providing training and counseling for manual handling, stress management, personal hygiene issues, and post-traumatic stress conditions;
Providing an advisory service including health promotion, ill health, and retirement, advice
for travelers, advice to management on the need for workers to be given restricted duties or
re-deployment, liaising with appropriate external authorities and medical specialists and
providing medical input into emergency plans covering events such as major accidents and
pandemics.
(a) Outline the process of hazard classification under the GHS system.
(b) Outline what is meant by ‘sensitizer’ under the GHS system.
(d) explain what actions might be required by the employer to control exposure.
legal limit
Long-term exposure limit (8-hour TWA limit reference period) 50
Short-term exposure limit (15-minute reference period)
100
Measuring out and adding the mixture to process vessel (duration of task 15m) 140
the 8-hour timeweighted average (TWA)=48
(a)
Hazard classification under the GHS system involves a two-step process. Firstly, relevant hazard data is identified and reviewed. This data is either already available or from further tests that are commissioned. In both cases, it is necessary to use data from standard test methods. This data is then compared to GHS classification criteria for the various hazard categories.
(b) A sensitizer causes an allergic response - which can be either skin or respiratory.
Skin - the sensitizing chemical passes through the epidermal barrier, causing antibodies to be formed
Respiratory system - allergic sensitization occurring in the respiratory system results in asthma
Sensitization occurs in two phases, the initial contact with the sensitizer may produce only mild effects but the subsequent exposure of even small amounts may produce an extreme reaction.
(d)
It is quite likely that on other days or for other workers, the value may be exceeded, so more detailed measurements should be carried out. The STEL is exceeded and some action is needed during the measuring stage
this involves a sensitizer (where even small amounts could cause an allergic reaction), you should try to reduce exposure to as low as possible (regardless
of the LTEL/STEL).
control measures such as substitution, process change, LEV
