IB2 Flashcards
The table below shows data provided in a supplier’s catalogue for three different grades of the same industrial chemical.
Fine white powder product code AS1/01 Average particle size(microns)15 Particle size distribution(microns)12-20 Fine white powder product code AS1/02 Average particle size(microns) 8 Particle size distribution(microns) 7-10 Fine white powder product code AS1/03 Average particle size(microns) 2 Particle size distribution(microns) 1-5
(a) Use the data to identify the likely distribution in the respiratory tract of each of these powders following inhalation.(3)
(b) In EACH case, describe the mechanisms the body may use to defend itself. (7)
(a)
Though there is some overlap, generally particles above 10 microns (i.e. AS1/01 powder) will be deposited in the nasal cavity (trapped by nasal hairs and mucous membranes). Particles of 7-10 microns (i.e. AS1/02 powder) will be deposited in the conducting airways (i.e. everything up to but excluding the respiratory units; that is, the trachea and bronchioles). Particles of 0.5-7 microns (i.e. AS1/03) deposited in the respiratory units (i.e. respiratory bronchioles and alveoli).
(b)
Nasal cavity - nasal hairs, sneeze reflex. Conducting airways - mucociliary escalator (trapping in mucous, cilia waft debris towards pharynx for swallowing or spitting). Respiratory units - alveolar macrophages (specialised attacking cells which ingest (phagocytose) foreign particles and then migrate up the mucociliary escalator as above). If particles cannot be moved in this way then inflammation of the membranes may occur and this may lead to the formation of fibrous cross-connection (scarring).
(a) Compare and contrast retrospective and prospective cohort studies as epidemiological methods.
(b) Outline the issues that can affect the reliability of the two epidemiology study methods.
(a)
Cohort studies are concerned with establishing a cause-effect (or exposure-disease) relationship and use exposed and unexposed groups. Retrospective cohort studies build an historical cohort in the past (from records of exposure histories, disease outcomes). Historic exposures are then estimated and disease is looked for in the present day cohort. Prospective cohort study starts in the present and follows cohort forward in time - exposure and health outcomes being monitored as the study proceeds. This study involves selecting groups of exposed and unexposed individuals who otherwise are very similar and then looking for disease in the future.
(b)
There is a range of issues that affect the reliability of these types of epidemiological study. For example, cohort size will make a difference to the statistical significance of results. Too small a cohort and the significance of the results may cease to have meaning. There are issues to do with the accuracy of historical records (of workplace exposure, health effects, diagnoses, etc.). This can mean that retrospective studies fail to find enough reliable evidence of exposure, etc. to make good predictions. There will always be complications of non-occupational exposure and lifestyle factors (smoking, drinking, diet, etc.) that will affect both types of study. Did a worker develop cancer because they were exposed to a certain toxic substance in a previous workplace or because they smoked for twenty years of their early life? Most ill health diseases have a period of latency (effects may take a long time to appear). There may be selection bias (i.e. the cohort is unrepresentative). There might be a ‘healthy worker effect’ (sick people leave workplaces, only the healthy ones remain to continue to work). Prospective short studies may suffer from loss of members (people die, move away, no longer co-operate, etc.).
Workers in a factory making furniture are potentially exposed to a range of solvents associated with adhesives, paints and varnishes.
Outline the range of factors that should be considered when assessing the health risks associated with this potential exposure.
The assessment of health risks from exposure to paint and varnish solvents in a factory producing flat-pack furniture should begin by considering the hazardous properties of the substances used, such as toxicity and ability to cause dermatitis. The likely level of exposure will depend on the quantities used, the volatility and also the work methods such as spraying or brush application, and such exposures should be assessed against the relevant Occupational Exposure Limits. The numbers of persons exposed and also the individual susceptibility of the persons exposed (i.e. health condition, pregnant, young) will affect the risk, as will the duration and frequency of exposure. There may be possible synergistic or additive effects from the substances being used and information on the paints and varnishes will be available from the materials data sheets.
The assessment will also need to take into account the adequacy of existing control measures and the results of any health surveillance or even complaints from workers.
(a) Describe the anatomical structure of the skin and describe how hazardous substances enter the body via this route.
(b) Explain how primary contact dermatitis occurs.
(c) Workers in a hair salon are experiencing skin irritation on their hands, which in one case has been formally diagnosed as contact dermatitis. Review the likely causes of the dermatitis and make recommendations to the salon manager on the steps that could be taken to try to overcome these problems.
(a)
The skin essentially consists of three layers:
Epidermis - the outer tough layer consisting of a horny zone of dead cells (continually being lost) together with a germinal zone below, from which these dead cells develop.
Dermis - true living skin containing blood vessels, sweat glands and nerve endings.
Subcutaneous adipose tissues - fatty tissues used for storage purposes.
In addition, the epidermis benefits from protective layer of glandular secretions, sebum in particular, which affords a good degree of waterproofing.
The skin is semi-permeable and some chemicals in liquid/solution form can go straight through it. This is particularly the case with organic solvents such as phenol, carbon tetrachloride and dimethyl sulphoxide (DMSO). Once through the skin, these chemicals can then permeate the tissues beneath the skin and enter blood vessels
The skin route is particularly available if the glandular secretions are removed (e.g. by solvents or washing) and when hot/sweaty (pores/sweat glands open).
Cuts/abrasions are another significant entry route. Here, the defensive layers of the skin have been physically damaged, so any hazardous substance introduced to this area can come into direct contact with body tissues and the bloodstream. This is a particular risk with biological agents, as a very small amount of the agent may be enough to cause infection and the agent then reproduces within the body to cause disease.
The final route of entry is very similar to the last, and that is direct physical injection through the skin, by puncture of the skin with a sharp object, such as a hypodermic needle (e.g. a needle-stick injury) or by high pressure gas or fluid injection (e.g. from a burst hydraulic pipe).
(b) Primary contact dermatitis arises as a result of skin contact with Primary Cutaneous Irritants (PCIs). PCIs can be chemicals (such as solvents, strong acids, strong alkalis) but also physical agents (such as hot or cold conditions).Frequent contact with water (wet working) is a major cause of contact dermatitis. These irritants de-grease or de-fat the skin; this results in drying out, cracking and inflammation/reddening. Dermatitis may not develop immediately. It might take a while or might arise from frequent exposure to quite mild irritants.
(c)
The hairdressing industry is a workplace where contact dermatitis is common.
Essentially, dermatitis in this case is caused by frequent wet working (washing/ shampooing/dying of hair), as well as from direct contact with the chemical irritants in shampoos, dyes, “perm” preparations, bleaching agents, sterilising fluids, etc. Such contact can occur directly (such as deliberately working without gloves) or accidentally (splashes to skin, touching contaminated equipment/clothing, etc.).
Various factors affect whether a worker will contract dermatitis or not.
Factors such as individual susceptibility (people’s personal response to wet working and dermatitic agents is different), frequency and duration of exposure, the presence of existing damage to skin, failure to wear gloves, etc.The steps that should be taken or considered to control the dermatitis include:
Pre-employment identification of susceptible individuals by health questionnaire or medical examination.
Making sure that information on the risks of contact dermatitis is brought to the attention of all workers through leaflets and training.
Ensuring that substance information is available to all workers (in the form of MSDSs, etc.).
Elimination or substitution, where possible, of the dermatitic agents.
Job rotation to minimise the amount of time that workers have wet hands.
Wearing protective gloves (non-latex) when wet working or dealing with chemicals (these must be of an appropriate type and should be examined routinely to ensure they still afford protection).
Drying hands properly and promptly.
Using moisturising creams.
Health surveillance in the form of regular visual checking of skin (for dryness, itching, cracking) followed by referral for workers with symptoms.
In certain instances, workers with a pre-existing condition may have to be prevented from working with dermatitic agents
Certain lung diseases caused by dusts at work are commonly known as the occupational pneumoconiosis.
(a) Review the causative agents, symptoms and mechanisms of damage of such a disease.
(b) Explain the information that may be needed in order to diagnose a case of pneumoconiosis.
(a) Pneumoconiosis can be subdivided into two principal groups; collagenous and noncollagenous.
Non-collagenous pneumoconiosis, typically caused by metal oxide dust such as tin oxide (a condition called stannosis), has relatively minor symptoms and is detectable by observation of reversible structural changes to lungs which generate a distinctive chest X-ray pattern (tiny opacities).
Collagenous pneumoconiosis is a far more serious condition, caused by respirable asbestos (asbestosis), crystalline silica (silicosis), coal dust (miner’s pneumoconiosis), cotton dust (byssinosis). Symptoms include a cough, breathlessness and emphysema. The dusts in these instances provoke a chronic inflammatory response; this in turn leads to formation of permanent collagenous scar tissue in lungs and loss of lung function. Death may result from heart failure brought on by the rapid beating of the heat necessary to pump blood quickly around the circulatory system as a result of the reduced lung function.
(b) In order to diagnose a case of pneumoconiosis, the employees work history would have to be investigated. This would normally be done by reviewing their employment history verbally, perhaps with reference to records at a later stage. Their exposure history to dusts known to cause pneumoconiosis would have to be gauged, again by verbal review of their employment history and the types of agent likely to have been involved. A chest X-ray would be taken and lung function tested by use of a spirometer. A clinical examination would complete the diagnosis
As part of a foam manufacturing process, a resin is mixed with a hardener that contains toluene di-isocyanate (TDI). Pre-employment screening is undertaken in order to exclude susceptible individuals.
(a) Identify the possible health effects of TDI.
(b) Identify the type of health screening that is likely to be conducted and outline the signs and symptoms that might lead to the exclusion of potential employees from the process.
(c) Describe measures that could be taken to reduce the employees’ exposure to TDI.
(a)
Isocyanates can cause eye irritation, allergic dermatitis and respiratory sensitisation (leading to asthma). Allergic dermatitis is where the skin becomes sensitised to the isocyanate. This occurs over time, as a result of over-exposure to the solvent. Once sensitised, exposure to the solvent will lead to a whole skin reaction, i.e. the skin all over the body may become red, inflamed, itchy and this may lead to cracked skin, flaking, suppuration, etc. Respiratory sensitisation involves the same process occurring to the lungs through inhalation of solvent vapours. Once sensitised, any exposure to isocyanate vapour may bring on an asthma attack.
(b)
Health screening - questionnaires (skin, breathing function), medical examination, healt assessment (lung function).
Signs/symptoms - existing allergies, asthma, predisposition to asthmatic conditions, depressed lung function
(c)
Eliminate TDI and all other forms of isocyanate from the workplace. This might be done by moving to a totally new production process, or by buying in foam pre-manufactured, so that the isocyanate-dependant part of the process is avoided.
Substitute TDI for less harmful forms of isocyanate solvent, such as MDI or HDI.
Apply an engineering solution and totally enclose the part of the process where TDI is handled and solvent fumes are generated. This might be done by direct dosing of the solvent (rather than hand dosing) and by automation of plant.
If total removal of workers from the process is not possible, then total enclosure in a handling booth (so that workers who do not need to be exposed are not exposed) should be considered. In this instance, any workers who have to come into contact with TDI must wear PPE which would include appropriate gloves, apron, face protection and respiratory protection.
Minimisation of the quantities of TDI being handled is a very practical step.
Local Exhaust Ventilation (LEV) must be applied to any enclosures where TDI is handled/exposed. This LEV must be maintained, cleaned, inspected and tested as per COSHH Regulations, ACoP and guidance.
Training must be given to all employees on the hazards associated with TDI and the precautions to follow. This would be particularly important, of course, to the employees who actually work with the solvent.
Contractors have been engaged to carry out re-cabling work in an office. During this work a small area of ceiling board is removed. At this point the office manager raises a concern that the ceiling material may contain asbestos and office staff and the contractors working in the area may become exposed to asbestos.
(a) Outline the steps that should be taken to deal with this immediate problem.
(b) Describe the features and principles of operation of the equipment that should be used to determine the airborne concentration of asbestos fibres.
(c) Outline steps that could be taken to prevent a similar situation arising during any future work of this nature.
Stop work immediately (assume it is asbestos).
Keep everyone else out of the area (to remove people from potential exposure).
If dust/debris is present on the clothing of the worker (or anyone else) make sure that the clothing is removed and bagged and that the person washes/ showers immediately (leaving the shower clean too).
Inform the person in charge (e.g. site manager).
Place warning signs in the area “possible asbestos contamination”.
Arrange for a sample to be taken and sent for analysis to discover if it is asbestos.
If the results show it is not asbestos, then no further action is required. However if it is, then depending on the size of the job and the condition of the ACM an HSE-licensed contractor may be needed. Lower level work such as short, non-continuous maintenance activities on material in good condition where only low-fibre release is expected, may be carried out without a licence but may require notification to the appropriate enforcing authority depending on the level of risk.
If a single ceiling tile is involved, it is unlikely to need a specialist licensed contractor and the board can be removed and replaced following the methods described in HSE guidance. If a specialist contractor is needed, then specific controls would also have to be put in place
(b)
The airborne concentration of asbestos fibres is determined in the following manner. Using the MDHS 39/4 method, a measured volume of air from a controlled flow sampling pump is drawn through a membrane filter held in a cowl filter head. After sampling, the filter is mounted on a microscope slide and made transparent using solvent. The fibres in a measured area are counted under the microscope and the concentration of fibres per volume of air is calculated from the fibre count and the measured volume.
(c)
There would be a need to find out if there is asbestos on/in the premises, what state it is in and what to do about it (if anything) in a planned, systematic way. A risk assessment, as to whether asbestos is, or is liable to be, present in the premises, should be undertaken. It should take into account the condition of the asbestos and amounts. This would require some investigation into the age and existing plans of the building, plus a survey/inspection of the premises. If asbestos is found, then a record of where it is and a plan of what to do with it would be required. With regards the scenario described, some form of contractor control might also be appropriate so that if contractors intend to disturb the fabric of the building then some authorisation is required by a person with knowledge of this site plan.
Hazardous substances entering the body through the skin can cause systemic effects.
(a) Describe the structure of the skin.
Marks will not be awarded for diagrams. A description in words is required.
(b) Explain how a hazardous substance could enter the body through the skin and cause a systemic effect.
(a)
Skin structure
The skin is the largest organ of the body. It has three main layers, the epidermis, the dermis and the subcutaneous layer.
The epidermis is an elastic layer on the outside that is continually being regenerated. It includes the following:
Keratinocytes - the main cells of the epidermis formed by cell division at its base. New cells continually move towards the surface. As they move they gradually die and become flattened.
Corneocytes - the flattened dead keratinocytes that together make up the very outer layer of the epidermis is called the stratum corneum or horny layer. This protective layer is continually worn away or shed.
Melanocytes – produce the pigment melanin that protects against UV radiation and gives skin its colour.
The dermis is the inner layer that includes the following:
Sweat glands – produce sweat that travels via sweat ducts to openings in the epidermis called pores. They play a role in temperature regulation.
Hair follicles – are pits in which hairs grow. Hairs also play a role in temperature regulation.
Sebaceous glands – produce sebum (an oil) to keep hairs free from dust and bacteria. Sebum and sweat make up the ‘surface film’.
The subcutaneous layer under the dermis is made up of connective tissue and fat (a good insulator).
(b)
Chemicals which pass through the skin are nearly always in liquid form. Solid chemicals and gases or vapours do not generally pass through the skin unless they are first dissolved in moisture on the skin’s surface.
Organic and alkaline chemicals can soften the keratin cells in the skin and pass through this layer to the dermis, where they are able to enter the blood stream.
Areas of the body such as the forearms, which may be particularly hairy, are most easily penetrated by chemicals since they can enter down the small duct containing the hair shaft
Chemicals can also enter through cuts, punctures or scrapes of the skin since these are breaks in the protective layer.
Contact with some chemicals such as detergents or organic solvents can cause skin dryness and cracking. There can also be hives, ulcerations or skin flaking. All these conditions weaken the protective layer of the skin and may allow chemicals to enter the body.
Some solvents may soften the keratin layer but are not believed to penetrate much further unless there is prolonged skin contact.
Other chemicals can readily pass through the epidermis and subsequently enter the blood stream. Some chemicals are so corrosive they burn holes in the skin, allowing entry for infection or other chemicals.
Once the substances is in, the bloodstream carries the substance around the body to target organs, or the entire body system.
Safety Data Sheets (SDSs) provide important information to employers, who are required to assess exposure to hazardous substances in their, workplace. A typical SDS is divided into sections that contain different types of information.
Identify FIVE different types of information contained in an SDS, AND for EACH, outline how the information could contribute to the assessment of
risk or control of exposure
-details of the manufacturer of the substance (such as emergency contact information) so that the user might make contact with them in the case of an
emergency.
- information on the physical properties such as its volatility/dustiness for
an example which will help assess how likely it is to be inhaled - health hazard information on the substance, such as whether it is toxic, corrosive or an irritant and the target organs which will indicate directly the type of harm
- the appropriate first aid measures to be taken in the event of contact which may indicate specific training or treatments
- the precautions to be taken when handling or storing the substance (segregation)
- regulatory information such as the exposure limit of the substance, which provides a standard against which to assess the likely significance of workplace exposure
- considerations to be taken when disposing of the substance
- and other relevant information such as those concerned with possible environmental damage or fire.
Building maintenance workers use hot and cold methods to strip old paint
containing lead from doors and windows. This produces dust, fume and vapour containing lead.
(a) Identify the specific health effects to the workers relating to working with lead.
(b) Outline the requirements for health surveillance for workers who work with lead.
(c) Workers have a general duty to comply with the health and safety measures put in place by their employers.
Outline what the workers should do to protect their health.
(a)
High levels of lead overshort period:
may cause anemia, weakness, and kidney and brain damage. Very high lead exposure can cause death.
Lead can damage a developing baby’s nervous system, miscarriage, stillbirths, and infertility (in both men and women).
Prolonged exposure to lead may also be at risk for high blood pressure, heart disease
weight loss and nerve damage. producing restlessness, a raised level of excitement and talkativeness, muscular twitching and possible delusions, acute and violent mania.
(b)
- At regular intervals (every 3, 6 or 12 months) during the work
- blood or urine samples are provided for analysis
- that a health record is created for each employee exposed or potentially exposed to lead.
- setting suspension levels, action levels for employee exposed to lead (vulnerable has lower levels)
- establishing a baseline for new joiners.
(c)
■ Make sure you have all the information and training need to work safely
with lead, including what to do in an emergency, such as a sudden uncontrolled release of lead dust or fume.
■ Follow good and well-tested work practices, and especially:
– keep the immediate work area as clean and tidy as possible;
– clear up and get rid of any lead waste at the end of each day or shift, as
directed by the employer;
– do not take home any protective clothing or protective footwear for washing or cleaning.
■ inspecting engineering controls prior to working with lead.
■ reporting damaged or defective equipment.
■ Use all the equipment provided by your employer and follow instructions for use
■ Make sure that equipment provided for worker health and safety fits correctly and is in good condition.
■ Only eat and drink in designated areas that are free from lead contamination.
■ Wear any necessary protective clothing and respiratory protective equipment
and return it at the end of the shift/day to the proper place provided by the
employer.
■ Practise a high standard of personal hygiene, and especially:
– wash hands and face and scrub your nails before eating, drinking or
smoking;
– wash and/or shower and change if necessary before going home.
Human epidemiology and animal studies are methods that can be used
to investigate whether a substance is carcinogenic.
(a)
(i) Explain what is meant by the term ‘carcinogen’.
(ii) Outline the advantages and disadvantages of human
epidemiology.
(iii) Outline the advantages and disadvantages of animal
studies.
(b) Outline the control measures that should be in place in a workplace where a carcinogenic substance is used.
(i): According to GHS, a carcinogen is a substance or a mixture of substances
which induce cancer or increase its incidence.
(ii)
Advantage:
■ Human epidemiology is a definitive method for identifying human carcinogens as it is based on experience in actual populations.
disadvantage:
■ Human epidemiology can be expensive and time-consuming and usually requires large populations to reduce sampling errors that may otherwise distort the real, underlying picture.
■Expensive and time-consuming,
■ Limited applicability (can’t really assess the carcinogenic potential of new substances);
■Requires large populations (statistical validity);
■Relies on the accuracy of historical records for substances currently in use;
■Problems with sensitivity and specificity (no test is 100% specific – can get false positives and false
negatives when testing the population to see if they have the disease).
(ii)
• Does not rely on exposing people to chemicals, thereby preventing
human disease and suffering.
• Can be quicker and cheaper than epidemiological studies on human
populations.
- Provides good-quality information about the effects of exposure to certain chemicals that could not be determined by other types of study, such as in-vitro studies.
- Allows the long-term effects of exposure to low doses to be studied, replicating the actual types of exposure that workers might experience at work.
These studies are not without their limitations:
• Responses vary between species, so the application to humans may be questionable.
• Testing on animals raises ethical questions and should be avoided where possible.
• Diseases like cancer may have a number of contributing factors (e.g. lifestyle).
• These studies may take a long time and be expensive (though not usually as long or as expensive as human
epidemiological studies).
(b)
- Reducing exposure to a level as low as reasonably practicable by minimizing quantities used and/or changing the physical form;
- The use of a totally enclosed system or automation of the process to physically separate workers from the process and, where this is not possible, the use of a partial enclosure in the workplace or appropriate local exhaust ventilation.
- The prohibition of eating, drinking, and smoking in areas that may be contaminated by carcinogens.
- Cleaning floors, walls, and other surfaces at regular intervals and whenever necessary.
• Designating those areas and installations that may be contaminated by carcinogens or mutagens and using
suitable and sufficient warning signs.
- Storing, handling, and disposing of carcinogens or mutagens safely, including using closed and clearly labeled containers.
- Providing adequate washing facilities.
- The numbers working in the restricted areas should be minimised and non-essential personnel excluded
- The use of PPE a temporary expedient until the risk was removed or eliminated.
Outline the merits and limitations of EACH of the following methods for identifying the carcinogenic potential
of a substance:
(iii) in vitro mutagenicity (AMES) testing.
(iii)In vitro mutagenicity testing / Short-term Testing, e.g. Ames Test – quick, cheap, avoids ethical issues,
mutagenicity is indicative of carcinogenic potential but raises issues of reliability (false positives and false negatives).
(a) Explain how exposure to silica dust can cause silicosis.
(b) The construction of a city’s underground rail line involves extensive tunneling and concrete spraying activities.
Outline controls that reduce the risk of workers developing silicosis, while carrying out tunneling and concrete spraying activities.
(a)
Silica is a substance naturally found in certain types of stone, rock,…Working with these materials can create a very fine dust that can be easily inhaled.
Silica is hazardous by inhalation.
When inhaled, respirable crystalline silica dust is deposited deep in the
lungs becoming trapped in the alveoli. Over time scar tissue develops causing a form of pneumoconiosis known as silicosis
(b)
-Adopting working processes that generate less dust for example any wet method is likely to generate less dust than a dry one
-Treating the dust on its transmission path using dust suppression techniques
for example water sprays, chemical additives, local exhaust ventilation (LEV), vacuum.
-to ventilate the area by dilution ventilation ,the need to test/maintain
these systems
- Use products that do not contain silica or have less silica in them
- Isolating high dust generation work processes within an enclosed room with restricted access
- a job rotation schedule so that the same workers are not continually exposed to silica
- Conduct a cleaning schedule for work areas and a maintenance schedule for engineering controls
- Never use compressed air, dry sweeping, or general-purpose vacuum cleaners to clean surfaces or clothing
- Tight-fitting respirator with an effective face seal
- health surveillance, spirometry or lung function testing.
(a) Outline the health effects associated with the Human Immunodeficiency Virus (HIV). (3)
(b) Outline control measures to protect against occupational exposure to the virus. (7)
(a) HIV
Affects the body’s immune defense system, reducing its ability to fight infections
Can result in Acquired Immune Deficiency Syndrome (AIDS). (potentially life-threatening infections and illnesses that happen when your immune system has been severely damaged by the HIV virus.)
Can reduce appetite and result in AIDS wasting syndrome. (Wasting syndrome refers to unwanted weight loss of more than 10 percent of a person’s body weight, with either diarrhea or weakness and fever that have lasted at least 30 days. )
Can result in opportunistic infections, such as hepatitis B, thrush or tuberculosis (Opportunistic infections (OIs) are infections that occur more frequently and are more severe in people with weakened immune systems)
(b) Control measures must focus on workplace controls, such as
Pre-employment medical screening
Identification of high-risk workers (more risk of being infected and/or an adverse outcome if infected.)
Sharps procedures and controls for dealing with and disposing of sharps (Dispose of used syringes or other sharp instruments in a sharps container.)
Procedures for dealing with and disposing of spills of bodily fluids
Use of microbiological cabinets for handling samples in a laboratory, such as a pathology lab.
Cleaning and disinfection procedures for surfaces such as lab benches
Providing PPE, eg. overalls/scrubs, gloves, masks
Providing controls to avoid physical contact with potentially violent persons, such as patients or prison inmates.
Providing facilities for those working outside of the controlled’ environment, eg in clients’ or patients’ homes, such as social workers or the police
Providing a high level of worker supervision
Providing workers with training in the need to follow control measures and observe good personal hygiene.
(i) NOAEL;
No Observed Adverse Effect Level (NOAEL) - the dose at which the response does not occur in any member of the population.
