12 Chemical and Biological Health Hazards and Risk Controls

Question 1

What are the physical forms of chemicals?

Answer 1

• Solid – a solid block of material (e.g. a lead ingot).
• Dust – very small solid particles normally created by grinding, polishing, milling, blasting, etc. and capable of becoming airborne (e.g. flour dust, rock dust).
• Fume – very small metallic particles that have condensed from the gaseous state during work with molten metal (e.g. welding) to create an airborne cloud.
• Gas – a basic state of matter; expands to fill the space available (e.g. carbon dioxide (CO2)). • Mist – very small liquid droplets suspended in air, normally created by spraying (e.g. paint spraying).
• Vapour – the gaseous form of a substance that exists as a solid or liquid at normal temperature and pressure (e.g. vapour given off by acetone solvent).
• Liquid – a basic state of matter; free flowing fluid (e.g. water at 20°C).

Question 2

How can we categorized biological agents?

Answer 2

• Fungi – moulds, yeast and mushrooms. Most are harmless to humans but some can cause disease, such as fungal infections (e.g. athlete’s foot) and farmer’s lung (an allergic irritation caused by inhaling mould spores).
• Bacteria – single-celled organisms that are found in vast numbers in and on the human body. Some are harmless, some are beneficial (certain gut bacteria) and some cause disease (e.g. legionnaires’ disease, leptospirosis).
• Viruses – very small infectious organisms that reproduce by hijacking living cells to manufacture more viruses. Many viruses cause disease (e.g. hepatitis).
• Prions - abnormal, transmissible agents able to induce abnormal folding of normal cellular prion proteins in the brain, leading to brain damage (e.g. Creutzfeldt-Jakob Disease (CJD or “mad cow” disease” and variant CJD)).

Question 3

Types of danger caused by chemicals.

Answer 3

• Physico-chemical effects – such as highly flammable, explosive or oxidising.
• Health effects – such as toxic or carcinogenic.
• Environmental effects – such as harmful to aquatic life.

Question 4

Classification of chemicals hazardous to health:

Answer 4

• Toxic – small doses cause death or serious ill-health when inhaled, swallowed or absorbed via the skin (e.g. potassium cyanide (KCN)).
• Harmful – cause death or serious ill-health when inhaled, swallowed or absorbed via the skin in large doses.
• Corrosive – destroy living tissue on contact (e.g. concentrated sodium hydroxide (NaOH)). • Irritant – cause inflammation of the skin or mucous membranes (e.g. eyes and lungs) through immediate, prolonged or repeated contact (e.g. ozone (O3)).
• Carcinogenic – may cause cancer (abnormal growth of cells in the body) when inhaled, swallowed or absorbed via the skin (e.g. asbestos). (Note that there are two categories of substance that are infrequently found in workplaces but can be of great concern when they are present:
• Mutagens – may cause genetic mutations that can be inherited.
• Toxic to reproduction – may cause sterility or affect an unborn child.)

Question 5

What are sensitizing agents?

Answer 5

Some chemicals are sensitising agents. This means that they are capable of producing an allergic reaction that will gradually worsen on repeat exposures. There are two groups of sensitising chemicals:

• Skin sensitisers – can cause allergic dermatitis on contact with the skin (e.g. epoxy resin).
• Respiratory sensitisers – can cause asthma on inhalation into the lungs (e.g. flour dust and isocyanates).

Question 6

Type of dermatitis

Answer 6

• Primary contact dermatitis - following immediate, repeated or prolonged contact with a primary skin irritant. This dermatitis is restricted to the skin that was in contact with the irritant substance only.
• Allergic or secondary contact dermatitis – following immediate, repeated or prolonged contact with a skin sensitising agent. This form of dermatitis often appears on different parts of the body other than the point of contact with the substance and can flare up in response to very small exposures once the person has become sensitised.

Question 7

Distinguish between acute and chronic-ill health.

Answer 7

• Acute effects – as a result of exposure to high levels of the substance, sometimes over very short periods of time, and usually quite quickly after exposure begins (seconds, minutes or hours), e.g. exposure to high concentrations of chlorine gas causes immediate irritation to the respiratory system.
• Chronic effects – as a result of exposure to lower levels of the substance, over long periods of time, and usually weeks, months or years after exposure began, e.g. asbestosis occurs 10-20 years after multiple exposures to asbestos.

Question 8

What are the main route of entry of hazardous substances into the body?

Answer 8

Inhalation – the substance is breathed in through the nose and mouth and down into the lungs. Dust can be inhaled through the nose and mouth in this way, but not all dust will travel down into the lungs. These two types of dust are called: –– Inhalable dust – particles of all sizes that can be inhaled into the nose and mouth. –– Respirable dust – particles less than 7 microns (7/1000 mm) in diameter that can travel deep into the lungs on inhaled breath.

Ingestion – the substance is taken in through the mouth and swallowed down into the stomach and then moves on through the digestive system. Ingestion usually occurs by cross contamination

Absorption through the skin – the substance passes through the skin and into the tissues beneath and then into the blood stream. Only some substances (e.g. organic solvents)

Injection through the skin – the substance passes through the skin barrier either by physical injection (e.g. a needle-stick injury) or through damaged skin (cuts and grazes).

Question 9

What are the defence mechanisms of the body?

Answer 9

• Cellular defence (internal defence), which allows cells to fight bacteria and other toxins mostly from blood, respiratory and ingestion entry routes.
• Superficial defence (external defence), which protects against toxins that enter through the skin and contaminants in the nose and throat (via collection by the hairs and mucus).

Question 10

Respiratory defences

Answer 10

The respiratory system is made up of the nose and nasal cavity, windpipe (trachea) and lungs. The air passes down the bronchi and bronchioles to the alveoli. These are small air sacs where oxygen enters the bloodstream. The respiratory system is protected by the following defences:

• The sneeze reflex.
• Filtration in the nasal cavity (which has a thick mucus lining that particles stick to). This is very effective at removing large particles; only particles less than 10 microns in diameter pass through. Not prevent smaller asbestos fibres or fine powders such as cement and finer silica dusts.
• Ciliary escalator – the bronchioles, bronchi and trachea are lined with small hairs (cilia). Mucus lining these passages is gradually moved by these cilia up out of the lungs. Any particles trapped in this mucus are cleaned out of the lungs by this mechanism. This filtration mechanism is effective at removing all particles larger than 7 microns in diameter.
• Macrophages/phagocytes – scavenging white blood cells of irregular outline. They produce enzymes that attack and destroy particles that enter body tissues. • Inflammatory response – any particles that cannot be removed by macrophages are likely to trigger an inflammation response. This causes the walls of the alveoli to thicken and become fibrous. This can be temporary or may result in permanent scarring (as with silicosis from silica and asbestosis from asbestos fibres).

Question 11

Skin Defences

Answer 11

The skin forms a waterproof barrier between the body and the outside world. It is made of two layers, the outer epidermis and the inner, thicker, dermis. Defence mechanisms include:

• A thick layer of dead cells at the surface of the epidermis which are constantly being replenished as they wear off.
• Sebum – an oily fluid secreted onto the surface of the skin that has biocidal properties.

Question 12

Factors to consider when carrying out an assessment of health risks include the: (10)

Answer 12

• Hazardous nature of the substance present – is it toxic, corrosive, carcinogenic, etc.?
• Potential ill-health effects – will the substance cause minor ill-health or very serious disease and will these result from short-term or long-term exposure?
• Physical forms that the substance takes in the workplace – is it a solid, liquid, vapour, dust, fume, etc.?
• Routes of entry the substance can take in order to cause harm – is it harmful by inhalation, ingestion, skin absorption, etc.?
• Quantity of the hazardous substance present in the workplace – including the total quantities stored and the quantities in use or created at any one time.
• Concentration of the substance – if stored or used neat or diluted, and the concentration in the air if airborne.
• Number of people potentially exposed and any vulnerable groups or individuals – such as pregnant women or the infirm.
• Frequency of exposure – will people be exposed once a week, once a day or continuously?
• Duration of exposure – will exposure be very brief, last for several hours or last all day?
• Control measures that are already in place – such as ventilation systems and PPE.

Question 13

What information should be included in a label? (5)

Answer 13

• The name of the substance/preparation.
• Some idea of the components which make the product hazardous (though this often depends on the overall classification of the product and any provisions for confidentiality or “trade secret” in the country).
• An indication of the danger, which may be by specific warning phrases or symbols or a combination of both.
• Basic precautions to take (things to avoid or PPE to wear, etc.).
• Name, address and telephone number of the supplier.

Question 14

Safety data sheets contain the following information:

Answer 14

• Identification of the substance or preparation and supplier – including name, address and emergency contact telephone numbers.
• Composition and information on ingredients – chemical names.
• Hazard identification – a summary of the most important features, including adverse health effects and symptoms.
• First aid measures – separated for the various risks, and specific, practical and easily understood.
• Fire-fighting measures – emphasising any special requirements.
• Accidental release measures – covering safety, environmental protection and clean-up.
• Handling and storage – recommendations for best practice, including any special storage conditions or incompatible materials.
• Exposure controls and personal protection – any specific recommendations, such as particular ventilation systems and PPE.
• Physical and chemical properties – physical, stability and solubility properties.
• Stability and reactivity – conditions and materials to avoid.
• Toxicological information – acute and chronic effects, routes of exposure and symptoms.
• Ecological information – environmental effects, which could include effects on aquatic organisms (sea and river life), etc.
• Disposal considerations – advice on specific dangers and legislation.
• Transport information – special precautions.
• Regulatory information – overall classification of the product and any specific legislation that may be applicable.
• Other information – any additional relevant information (e.g. explanation of abbreviations used).

Question 15

What are the limitations that MSDS has in providing information to assess health risks?

Answer 15

• They contain general statements of the hazards. They do not allow for the localised conditions in which the substances are to be used, which will affect the risk.
• The information can be highly technical and therefore meaningless to non-specialists. • Individual susceptibility to substances varies; a person can be very prone to the health effects of a certain chemical.
• They provide information about the specific substance or preparation in isolation and do not take into account the effects of mixed exposures.
• The information represents current scientific thinking and there may be hazards present that are not currently understood.

Question 16

When should be appropriate to stablish the role of hazardous substance monitoring?

Answer 16

• When failure or deterioration of the control measures could result in serious health effects.
• When measurement is required so as to be sure that anexposure limit is not exceeded.
• The effectiveness of control measures.
• If adequate control of exposure is no longer being maintained, following process or production changes, for example

Question 17

Types of Continuous monitoring

Answer 17

• Stain Tube detectors
• Passive Samplers
• Smoke tubes / Sticks Dust
• Monitoring Equipment
• Dust Lamp (Tyndall Lamp)

Question 18

What are the disadvantages of continuous Monitoring devices.

Answer 18

• Are expensive and require considerable training in their use.
• May not record peaks and troughs, merely an average.
• May not identify a specific type of contaminant (depending upon the design of the equipment and sensors used).
• Can be tampered with by workers to impact the results.
• If used as a static sampler, their results cannot be extrapolated to give results for personal exposure.  

Question 19

Stain Tube Detectors

Answer 19

These are easy to use and useful for analysing gas and vapour contamination in air at one moment in time. The principle of operation is simple – a known volume of air is drawn through a chemical reagent contained in a glass tube. The contaminant in the air reacts with the reagent and a coloured stain is produced. The degree of staining gives a direct reading of concentration. The instrument comprises a glass tube containing the chemical reagent fitted to a hand-operated bellows or piston-type pump. Many types of tube are available for detecting different gases and vapours. Stain tubes are quick and cheap to use, require little training and provide an instant result with no additional analysis requirements. However, their use is limited, as they:

• Are only suitable for gases and vapours, not dusts.
• Can be inaccurate.
• Can only be used for grab-sampling and not for taking time-weighted measurements.
• Are fragile.
• Have a limited shelf-life.
• May be used incorrectly.

Question 20

Passive Samplers

Answer 20

These use absorbent chemicals to sample contaminants without using a pump to draw air through the collector. At the end of the sampling period, the sampler is sent for laboratory analysis This a more complex and expensive (and slower) process, requiring training in its use. However, the results can be very accurate and can be used to calculate time-weighted measurement results.

Question 21

Smoke Tubes / Sticks

Answer 21

These are simple devices that generate smoke in a controlled chemical reaction. They are similar in appearance to stain tubes and can be used in conjunction with a rubber bulb. Breaking the smoke tube open activates the chemical reaction, then the bulb is used to puff the smoke as required. Smoke tubes are useful for visualising the movement of air currents in a workplace and in particular can be used to assess the effectiveness of ventilation and extraction systems (and to provide general information about air movements).

Question 22

Dust Monitoring Equipment

Answer 22

Dust exposure in the workplace can be quantified using a sampling train made up of an air pump, tube and sampling head. This equipment can be worn by a worker, so gives an indication of personal exposure

Question 23

Dust Lamp (Tyndall Lamp)

Answer 23

Airborne dust in the workplace which is not visible to the naked eye can be visualised using a dust lamp. A strong beam of light is shone through the area where a cloud of finely divided dust is suspected. The eye of the observer is shielded from the light beam and the dust cloud is made visible. This method is used to determine how exhaust ventilation systems are working.

Question 24

Limitations of hazardous Substance Monitoring

Answer 24

• Accuracy of results – monitoring equipment is often limited in its accuracy and variations between will occur depending on the time it is used.
• Variations in personal exposure – even when careful monitoring has been carried out there may still be variation in employees’ personal exposure from the monitoring results due to personal habits and one-off events.
• Absence of a standard – monitoring for its own sake is of no use if there is no occupational exposure limit (OEL) to compare monitoring results to. Not all hazardous substances have an OEL set.
• Other exposure routes – monitoring focuses exclusively on airborne contaminant.

Question 25

Long-Term and Short-Term limits for OELS

Answer 25

Occupational exposure limits are time-weighted average exposures; in other words, they are calculated by measuring a person’s average exposure over a specific reference period of time. They only apply to airborne concentrations of a substance. The two reference periods of time commonly used are:

• 15 minutes (short-term exposure limit, also known as a STEL). Short-term exposure limits combat the ill-health effects of being exposed to very high levels of the substance for quite short periods of time.
• 8 hours (long-term exposure limit, also known as a LTEL ). Long-term exposure limits combat the illhealth effects of being exposed to relatively low concentrations of the substance for many or all hours of every working day through an entire working lifetime.

Question 26

Define Time-weighted average.

Answer 26

A time-weighted average is equal to the sum of the part of each time period which is multiplied by the exposure level of the contaminant in that time period. It is then divided by the hours in the working day

Question 27

Limitations of exposure limits

Answer 27

• OELs are designed only to control the absorption into the body of harmful substances following inhalation. They are not concerned with absorption following ingestion or through contact with the skin or eyes.
• They take no account of individual personal susceptibility. Many of the limits have also been established in countries in Europe and the USA and are based on male physiology, so variations due to ethnicity and gender may be significant.
• They do not take account of the synergistic (or combined) effects of mixtures of substances, e.g. the use of multiple substances.
• They may become invalid if the normal environmental conditions are changed, e.g. changes in temperature, humidity or pressure may increase the harmful potential of a substance.
• The organisation may believe that limits are being adhered to but the employees may be working with controls which are no longer effective.
• The monitoring equipment may become contaminated, resulting in inaccurate results.
• Some limits are only “guidelines”.
• Some limits do not consider all the possible health effects of a substance, e.g. impact on the skin, such as dermatitis, would not be considered with an airborne limit.

Question 28

Principles of good practice with regards to controlling exposure to hazardous substances

Answer 28

• Minimisation of emission, release and spread of hazardous substances through design and operation of processes and task activities.
• Accounting for relevant routes of entry into the body when developing control measures for hazardous substances. This will give clear indication of the type of control required, whether personal or collective control is needed, and the level of control necessary (based on toxicity).
• Exposure control which is proportional to health risk.
• Effectiveness and reliability of control options that minimise the escape and spread of hazardous substances.
• Use of personal protective equipment (PPE) in combination with other control measures if adequate control cannot otherwise be achieved. Specifically, respiratory
• Regular checks and review of the control measures that are in place to ensure that they remain effective.
• Provision of information and training.
• Ensuring that any control measures implemented do not increase the overall risks to health and safety.

Question 29

How to eliminate or substitute the exposure to hazardous substances?(7)

Answer 29

• Eliminating the process or type of work that requires the use of the substance (e.g. outsourcing a paintspraying operation).
• Changing the way that the work is done to avoid the need for the substance (e.g. securing with screws rather than gluing).
• Reducing exposure times.
• Disposing of unused stock of the substance that is no longer required.
• Substituting the hazardous substance by using a non-hazardous one (e.g. switching from an irritant to a non-hazardous floor cleaner).
• Substituting the hazardous substance by using one that has a lower hazard classification (e.g. switching from a corrosive substance to an irritant substance).
• Changing the physical form of the substance to one that is less intrinsically harmful (e.g. massive solid rather than powder).

Question 30

Show a typical Local Exhaust Ventilation

Answer 30

A typical LEV system consists of:

• An intake hood that draws air from the workplace in the immediate vicinity of the contaminant.
• Ductwork that carries that air from the intake hood.
• A filter system that cleans the contaminant from the air to an acceptable level.
• A fan of some sort that provides the motive force to move the air through the system.
• An exhaust duct that discharges the clean air to atmosphere.

Question 31

Different intake hoods are used on LEV systems, but they can be categorised into two main types:

Answer 31

Captor hoods – capture the contaminant by drawing it into the system by overcoming the contaminant’s initial velocity (which may have been taking it away from the hood, such as during grinding).

Receptor hoods – positioned in such a way that the contaminant is moving in that direction already, so less air movement is required to achieve uptake (e.g. a large intake hood suspended above a bath of molten metal; the metal fume will be hot and will rise up into the hood on convection currents).

Question 32

The effectiveness of an LEV system will be reduced by:(8)

Answer 32

• Poorly positioned intake hoods.
• Damaged ducts.
• Excessive amounts of contamination.
• Ineffective fan due to low speed or lack of maintenance.
• Blocked filters.
• Build-up of contaminant in the ducts.
• Sharp bends in ducts.
• Unauthorised additions to the system.

Question 33

LEV systems should be routinely inspected and maintained to ensure their ongoing effectiveness. This may include:

Answer 33

• Routine visual inspection – to check the integrity of the system, signs of obvious damage and build-up of contaminant both outside and inside the ductwork. Filters should be visually inspected to ensure they are not blocked and the exhaust out-feed should be checked.
• Planned preventive maintenance – may include replacing filters, lubricating fan bearings and inspecting the fan motor.
• Periodic testing – to ensure that air velocities through the system are adequate. This can be done by visual inspection of the intake hood using a smoke stick, measuring air velocities at the intake and in the ductwork using anemometers, and measuring static pressures using manometers and pressure gauges.

Question 34

When dilution Ventilation is appropriate?

Answer 34

Dilution ventilation operates by diluting the contaminant concentration in the general atmosphere to an acceptable level by changing the air efficiently in the workplace over a given period of time, e.g. a number of complete changes every hour. These air changes might be achieved passively (by providing low level and/or high level vents) or actively using powered fans. Dilution ventilation is appropriate where:

• The OEL of the harmful substance is high.
• The rate of formation of the gas or vapour is slow.
• Operators are not in close contact with the contamination generation point.

Question 35

Limitations of dilution ventilation systems:

Answer 35

• Not suitable for the control of substances with high toxicity.
• Do not cope well with the sudden release of large quantities of contaminant.
• Do not work well for dust.
• Do not work well where the contaminant is released at a point source.
• Dead areas may exist

Question 36

Two main categories of RPE:

Answer 36

• Respirators filter the air taken from the immediate environment around the wearer. Respirators are used to remove a contaminant from the air. They cannot be used in an environment where there may be a lack of oxygen (as they can only “filter”, they cannot “add oxygen”), and they should not be used either to remove a contaminant which is very toxic or within confined spaces
• Breathing apparatus provides breathable air from a separate source. As breathing apparatus (BA) provides a stream of fresh, clean air and does not rely on filters, it can be used in atmospheres where contaminants may be toxic or where there may be a lack of oxygen

Question 37

Type of respirators

Answer 37

• Filtering face-piece respirator
• Half-mask or ori-nasal respirator
• Full-face respirator
• Powered Respirator

Question 38

Benefits and Limitations of Filtering face-piece respirator

Answer 38

The simplest type, consisting of a filtering material held over the nose and mouth by an elastic headband.

• Benefits
  
  • Cheap
  • Easy to use
  • Disposable
• Limitations
  
  • Low level of protection
  • Does not seal against face effectively
  • Uncomfortable to wear

Question 39

Benefits and Limitations of Half-mask or ori-nasal respirator

Answer 39

Consists of a rubber or plastic face-piece that fits over the nose and mouth with one or two canisters (cartridges) that contain the filtering material.

• Benefits
  
  • Good level of filtration
  • Good fit achievable
  • Easy to use
• Limitations
  
  • No built-in eye protection
  • Negative pressure inside face-piece
  • Uncomfortable to wear

Question 40

Benefits and Limitations of full face respirator

Answer 40

Similar to the half-mask, but with a built in visor that seals in the eyes and face. Again, care must be taken to select the correct filters.

• Benefits
  
  • Good level of filtration
  • Good fit achievable
  • Protects the eyes
• Limitations
  
  • Restricts vision
  • Negative pressure inside face-piece
  • Uncomfortable to wear

Question 41

Benefits and Limitations of powered respirator

Answer 41

A powered fan blows filtered air to the wearer. Usually made up of a helmet and face visor with the air blown down over the face from the helmet. Care must be taken to select the correct filters.

• Benefits
  
  • Intermidiate level of filtration
  • Air movement cools wearer
  • Air stream prevents inwar leaks
• Limitations
  
  • Heavy to wear
  • No tight face seal
  • Limited battery life

Question 42

Types of breathing apparatus

Answer 42

• Fresh air hose BA
• Compressed air BA
• Self-Contained BA

Question 43

Benefits and Limitations of Fresh air hose BA

Answer 43

The simplest type, where a largediameter hose is connected to the user’s face mask. Air is either: –– Drawn down the hose by breathing. –– Blown down by a fan at low pressure.

• Benefits
  
  • Air is from outside the work room
  • Supply of air is not time-restricted
• Limitations
  
  • Hose must be tethered
  • Bends or kinks make breathing difficult
  • User is restricted by limited hose length

Question 44

Benefits and Limitations of Compressed air hose BA

Answer 44

Similar to the fresh air hose system, but air is supplied down a small-bore hose at high pressure.

• Benefits
  
  • Positive pressure inside face-piece
  • Supply of air is not time-restricted
  • Wearer is not burdened with sylinder
• o Limitations
  
  • Hose can be long, but not endless.

Question 45

Benefits and Limitations of Self-Contained air hose BA

Answer 45

Breathable air is supplied from a pressurised cylinder worn by the user

• Benefits
  
  • Positive pressure inside face-piece
  • Complete freedom of movement
• Limitations
  
  • Supply of air is time-restricted
  • Equipment is bulky and heavy
  • More technical training is required-

Question 46

Factors affecting the suitability of RPE:

Answer 46

• Concentration of the contaminant and its hazardous nature.
• Physical form of the substance, e.g. dust or vapour.
• Level of protection offered by the RPE.
• Presence or absence of normal oxygen concentrations.
• Duration of time that it must be worn.
• Compatibility with other items of PPE that must be worn.
• Physical requirements of the job, such as the need to move freely.
• Shape of the user’s face and its influence on fit.
• Facial hair that might interfere with an effective seal.
• Physical fitness of the wearer.

Question 47

How to calculate the assigned protection factor (APF)

Answer 47

Dividing Concentration of contaminant in workplace between Concentration of contaminant in face piece.

Question 48

Hand Protection

Answer 48

Gloves (short cuff) and gauntlets (long cuff) can give protection

Question 49

Eye Protection

Answer 49

• Safety spectacles offer a degree of front and side protection but do not completely encase the eye.
• Safety goggles completely encase the eye and offer better splash and impact resistance.
• Face visors cover the eyes and face, offering a higher degree of protection.

Question 50

Body Protection

Answer 50

• Overalls (prevent direct skin contact with agents such as grease).
• Aprons (prevent spills and splashes from getting onto normal work-wear and soaking through to the skin).
• Whole body protection (the entire body is encased in a protective, chemical-resistant suit).

Question 51

Good hygiene practices are

Answer 51

• Hand-washing routines when leaving work-rooms.
• Careful removal and disposal of potentially contaminated PPE to prevent cross-contamination of normal clothes.
• Prohibition of eating, drinking and smoking in work areas.

Question 52

Health surveillance may be needed, but it is required where:

Answer 52

• here is an adverse health effect or disease linked to a workplace exposure, and
• it is likely that the health effect or disease may occur, and
• there are valid techniques for detecting early signs of the health effect or disease, and
• the techniques don’t themselves pose a risk to employees.

Question 53

Two types of health surveillance are commonly carried out:

Answer 53

• Health monitoring – the individual is examined for symptoms and signs of disease that might be associated with the agent in question. For example, a worker in a bakery might have a lung function test to check for signs of asthma; flour dust is a respiratory sensitiser capable of causing occupational asthma.
• Biological monitoring – a blood, urine or breath sample is taken and analysed for the presence of the agent itself or its breakdown products. For example, a worker in a car battery manufacturing plant might have a blood sample taken to test for the levels of lead in the bloodstream.

Question 54

Types of check which could be included in a health surveillance programme depend upon the hazards in the workplace, but may include:

Answer 54

• At a basic level, a health assessment questionnaire.
• Self-checks or checks by a supervisor (e.g. forskin rashes).
• At a more involved level, a nurse may carry out an examination. This might also be carried out by a doctor (physician) under certain conditions (e.g. sometimes this is required in law, such as for certain radiation workers). Examinations may consist of:
  
  • Skin checks to look for signs of dermatitis or rashes.
  • Lung function tests (spirometry).
  • Hearing tests (audiometry).
  • Eyesight checks (e.g. for drivers).
  • X-rays and scans (though this is more unusual).
  • Blood tests (if certain hazardous substances are used).

Question 55

Exposure to carcinogens, mutagens and asthmagens should be prevented, but if this is not possible then a hierarchy of controls can be adopted:

Answer 55

• Total enclosure of the process and handling systems.
• Prohibition of eating, drinking and smoking in potentially contaminated areas.
• Regular cleaning of floors, walls and other surfaces.
• Designation of areas that may be contaminated (using warning signs).
• Safe storage, handling and disposal.

Question 56

What is asbestos?

Answer 56

Asbestos is a generic name given to a collection of naturally occurring minerals that have been used extensively as fire-resistant building and lagging materials. The three main forms of asbestos are blue (known as crocidolite), brown (amosite) and white (chrysotile).

Question 57

Health Risks deriving from asbestos

Answer 57

Asbestos is hazardous by inhalation. Four forms of disease are associated with asbestos exposure:

• Asbestosis – asbestos fibres lodge deep in the lungs and cause scar tissue formation. If enough of the lung is scarred then severe breathing difficulties occur. Asbestosis can prove fatal and increases the risk of cancer.
• Lung cancer – asbestos fibres in the lung trigger the development of cancerous growths in the lung tissue. Usually fatal.
• Mesothelioma – asbestos fibres in the lung migrate through the lung tissue and into the cavities around the lung and trigger the development of cancerous growths in the lining tissue. Always fatal.
• Diffuse pleural thickening – thickening of the lining tissue of the lung (sometimes know as pleural plaques) that causes breathing difficulties. Not fatal.

Question 58

Controls when work involves disturbing ACMs (7)

Answer 58

• The work must be notified to the local enforcement agency.
• The work area must be sealed to prevent the escape of air contaminated with asbestos dust.
• Workers entering the sealed area must wear protective clothing and respiratory protective equipment to prevent dust inhalation.
• The sealed area must be ventilated by a negative pressure ventilation system with high efficiency particulate air (HEPA) filters.
• All ACMs removed must be securely double-bagged, labelled and disposed of as a hazardous waste at a site licensed to receive it. • Monitoring of asbestos dust levels in the air must be carried out both inside and outside the sealed work area.
• Worker exposure must not exceed a specified limit (similar in principle to a OEL).
• The sealed enclosure should only be removed once monitoring has confirmed that asbestos dust levels have dropped below safe limits and a clearance has been given.
• Workers must be provided with health surveillance.

Question 59

Typical controls with blood-borne viruses

Answer 59

Hepatitis A is contracted orally by cross-contamination with faecal material containing the hepatitis A virus, so sewage workers are at risk.

Hepatitis B is transmitted in body fluids, such as blood, so occupations at risk would include health care workers (doctors and nurses), firefighters, police and waste disposal workers.

Typical controls include:

• Use of PPE (such as gloves and eye protection) when handling potentially contaminated material.
• Correct disposal of potentially contaminated material (such as clinical waste).
• Prevention of needle-stick injuries by correct disposal of sharps in a sharps bin.
• Decontamination and disinfection procedures.
• Vaccination where appropriate.
• Procedures to deal with accidental exposures (e.g. needlestick injuries).

Question 60

Typical controls with Carbon Monoxide (CO)

Answer 60

A colourless, odourless gas usually encountered as a byproduct of partial combustion (e.g. poorly maintained heating boiler). It is hazardous by inhalation. Carbon monoxide interferes with this oxygen carrying process by binding onto the haemoglobin molecule at the same place where the oxygen should be(forming a compound called carboxy-haemoglobin). This prevents oxygen transportation and can lead to death by asphyxiation. Low levels of CO (0.005%) will cause a progressively worsening headache. Levels of 1.3% will cause immediate unconsciousness and death within three minutes. Note that this can occur even though oxygen concentrations are normal at 21%.

Typical controls include:

• Restricting work on gas systems to competent engineers only.
• Maintenance and testing of boilers and flues.
• Good general workplace ventilation.
• LEV for vehicle exhausts in workshops.
• Care in the siting of equipment containing combustion engines.
• Carbon monoxide alarms.
• Confined space entry control.

Question 61

Typical controls with Cement

Answer 61

In its dry powder form it is an irritant dust, which is easily inhaled or blown into the eyes. Once mixed with water it is corrosive on contact with the skin or eyes. Typical controls include:

• Eliminating or reducing exposure.
• Use of work clothing, and PPE such as gloves, dust masks and eye protection.
• Removal of contaminated clothing.
• Good hygiene and washing on skin contact.

Question 62

Typical controls with Legionella Bacteria

Answer 62

Legionella bacteria are water-loving soil bacteria. The bacteria are hazardous when inhaled into the lungs, where they cause Legionnaires’ disease The most common sources for outbreaks of the disease are outdoor cooling towers associated with air conditioning systems.

Typical controls include:

• Enclosing water systems to minimise the risk of contamination.
• Water treatment (e.g. chlorination) to kill the bacteria.
• Operating hot water systems above 60°C (the bacteria are temperature-sensitive and are killed above 60°C).
• Use of biocides (treatment chemicals) for some water systems.
• Prevention of limescale build-up (limescale can harbor the bacteria).
• Routine cleaning of cooling towers.
• Water sampling and analysis.

Question 63

Typical controls with Leptospira Bacteria

Answer 63

Leptospira bacteria commonly infect animals such as rats, mice, cattle and horses

Typical controls include:

• Preventing rat infestation, by good housekeeping and pest control.
• Good personal hygiene (e.g. hand-washing).
• PPE (especially gloves).
• Covering cuts and grazes.
• Issuing workers with an “at risk” card to be shown to the worker’s doctor (physician) to allow early diagnosis.

Question 64

Typical controls with Silica

Answer 64

A component of rock commonly encountered in the mining, quarrying, pottery and construction industries, silica is hazardous by inhalation. When inhaled, respirable crystalline silica dust is deposited deep in the lungs. Over time it causes scar tissue to form (known as silicosis – very similar to asbestosis). This progressive disease leads to breathlessness and chest pain and can prove extremely disabling and fatal (by heart and lung failure).

Typical controls include:

• Prevention of exposure by use of alternative work methods.
• Dust suppression by water jet/spray.
• Local exhaust ventilation.
• Respiratory protective equipment.
• Health surveillance (lung function test and chest X-ray).

Question 65

Typical controls of Wood Dust

Answer 65

Certain types of wood dust are more likely to cause asthma than others and are therefore categorised as asthmagens. Hardwood dusts can cause cancer Typical controls include:

• Local exhaust ventilation systems.
• The use of vacuuming to clean up dust (not sweeping).
• Respiratory protective equipment.
• Health surveillance (usually annual questionnaire).

Question 66

Factors to consider when disposing of waste using a compactor:

Answer 66

• The hazardous nature of the waste.
• The duty of care to dispose of the waste in line with relevant law.
• Any appropriate documentation that should accompany the waste.
• Preventing the waste from escaping from safe storage.
• Keeping the waste segregated from other types of waste.
• Safe loading of the compactor.
• Guarding of moving parts.
• Safe movement of vehicles during collection or unloading.

Question 67

Name six general hazards that might arise when handling and storing waste for disposal.

Answer 67

• Any manual handling of the waste.
• Mechanical hazards arising from any handling equipment such as trucks or compactors.
• Fire hazards associated with storing combustible materials, especially if stored outside and accessible to trespassers.
• Health hazards arising from the chemical nature of the waste, e.g. toxic substances.
• Hazards arising from the mixture of incompatible chemicals that might react together to form harmful products or even cause fire.
• Biological hazards that might arise from disposal of organic waste such as food waste and the pests (e.g. rats) that might be associated.

Question 68

(a) Identify THREE forms of biological agent. (3)
(b) Identify THREE possible routes of entry into the body for a biological agent. (3)
(c) Give TWO control measures to reduce the risk of exposure to a biological agent. (2)

Answer 68

(a) Common forms of biological agents include bacteria, viruses and fungi.

(b) Three possible routes of entry for a biological agent include inhalation (e.g. of dusts or spores), absorption (through the skin, eyes or mucous membranes), and injection (e.g. through needle- stick injuries).
(c) Two possible control measures include the use of PPE – such as goggles and gloves – to prevent skin and eye contamination with biological agents, or the use of immunisation to provide immunity from infection for some agents, such as hepatitis B vaccina-tions given to health workers or first-aiders..

Question 69

Spill containment procedures are important wherever liquid pollutants are present. Measures which could be taken include:

Answer 69

• Provision of spill kits containing booms to contain the spillage and absorbent granules or pads to soak up the spill (ready for safe disposal).
• Drain covers which can be used to seal surface water drains.
• Training of operators in the use of the spill kits.

Question 70

Hierarchy of principles for waste management

Answer 70

• Reduce
• Reuse
• Recycle
• Other recovery
• Disposal