Unit GC 2 – Controlling workplace hazards Element 7: Chemical and biological health hazards and control

Question 1

Forms that chemical agents may come in

Answer 1

Dusts - consist of solid particles of varying size and are created by such operations as grinding or sieving of solid materials, controlled detonations and various drying processes. In still atmospheres, dusts tend to settle under gravity and accumulate on surfaces. Where there is turbulence, at least some element of the dust will remain airborne.

Fibres - Asbestos fibres and other man-made mineral fibres (MMMF) have different characteristics to dust particles. Important dimensions are the length and diameter of the fibre and the length to diameter ratio.

Fumes - are fine particulate solids, which are created by condensation from a vapour (see below), very often after a metal has been converted to the molten state. The metallic fume is usually the oxide of the metal and is highly toxic.

Gases - a gas is a formless chemical which occupies the area in which it is enclosed. Its volume and state can be changed by the combined effect of increased pressure and decreased temperature. There are many toxic gases used in industry, such as chlorine, hydrogen sulphide, etc. Gases used in construction include propane, butane, acetylene and LPG.

Mists - consist of finely suspended droplets formed by condensation from a gas or the atomising of a liquid or from aerosols. Mists are created by many industrial processes, such as chromium plating, charging lead acid batteries and car paint spraying.

Vapour - is the gaseous form of a liquid below its boiling point. There is an equilibrium
between the two phases. Heating a liquid causes evaporation. Solids also exist in equilibrium with vapour, hence we can smell them, but in most cases the amount of vapour is negligible.

Liquids - many chemicals are supplied and used in the workplace in liquid form. These can vary from relatively harmless cleaning fluids through to highly toxic and corrosive acids and alkalis.

Aerosol - fine suspension of solid particles or droplets in a carrier gas.

Question 2

Forms that biological agents may come in

Answer 2

Fungi - a fungus is a plant lacking chlorophyll and reproducing by spores. Examples include
mushrooms, mould and yeasts. Fungal diseases manifest themselves as an allergic or immune response in the form of asthmatic and/or influenza-type symptoms from inhalation of dust or air contaminated by fungi, such as dry rot in roofs.

Bacteria - a bacterium is any of a large group of single celled, microscopic organisms of various shapes that are often agents of fermentation and putrefaction and that may cause disease. There are many bacteria present in the world, but those that we are concerned with here are those which may be present because of the particular nature of the work processes
themselves. Examples include:

• Legionella – caused by the bacterium Legionella Pneumophila, which may be present given certain conditions in cooling towers, water systems and air-conditioning systems. The bacterium may be spread by sprays of mist from the contaminated water source.
  It affects the lungs and is deposited in the alveoli, and can be fatal.
• Zoonoses – animal bacterial infections which may be transmitted to people in the course of their working with or near particular animals. On construction sites, those
  working near rivers, watercourses or sewers are particularly at risk. Common examples of zoonoses include:
• Leptospirosis – contracted by working near sewers or infected watercourses and caused mainly by rats’ urine, although some evidence exists that other animals
  may also be a cause, e.g. voles and fieldmice. Leptospirosis is a notifiable disease under the Reporting of Injuries, Diseases and Dangerous Occurrences
  Regulations 1995 (RIDDOR).
• Tetanus – see later in the element.
• Anthrax – a virulent bacterial infection which may occur in those who are in contact with live animals suffering from the disease or, more often, from handling
  infected animal skins or carcasses.
• Brucellosis – caused by a pathogen contracted from cattle or pigs.

Viruses - a virus is a pathogenic agent capable of increasing rapidly inside a living cell. Examples
include:

• Hepatitis B -this severe form of jaundice is most common amongst medical staff and refuse
  disposal operatives as a result of contact with blood or excreta of patients suffering from viral hepatitis or in whom the disease is still in its incubation stage, or from
  carelessly discarded syringes and other ‘sharps’ in disposable plastic sacks. The disease is normally self-limiting with recovery in about six weeks. In about 5% of cases, chronic infectious hepatitis follows, leading to cirrhosis and possibly death.

Question 3

Outline the common classes of hazardous substances

Answer 3

Irritant - Non-corrosive substances which through immediate, prolonged or repeated contact with skin or mucous membrane may cause inflammation e.g. Petrol

Corrosive - Substances which on contact with living tissue may destroy it by burning e.g. acids

Harmful - Substances which if swallowed, inhaled or penetrate the skin may cause damage to health

Toxic - A poisonous substance which in low quantities may cause death, acute or chronic damage to health

Carcinogenic - Substance which cause disorders to cell growth that may lead to cancer

Question 4

Outline the main routes of entry of substances into the body

Answer 4

• Inhalation
• Ingestion
• Injection
• Absorption
• Direct Contact

Question 5

The body defences against hazardous substances

Answer 5

Respiratory system – nasal hairs; mucous lining; ciliary escalator; coughing and sneezing.
Digestive system – vomiting and diarrhoea.
Eyes – tear production.
Skin – natural oils; blisters; rashes; inflammation.

Question 6

The differences between Irritant or Contact Dermatitis and Sensitive or Allergic Dermatitis

Answer 6

Contact dermatitis usually occurs after prolonged exposure to a substance. When exposure ceases the symptoms usually disappear.

Allergic dermatitis occurs when a person becomes sensitised to a substance. Future exposures will normally cause an allergic reaction.

Question 7

The physical signs of occupational dermatitis

Answer 7

• Blisters
• Inflammation
• Dryness
• Reddening
• Cracking of skin

Question 8

Common sources of information relevant to hazardous substances

Answer 8

• UK’s HSE Guidance Note EH40
• Signs and labels on containers, packages etc.
• Manufacturers Material safety data Sheets

Question 9

Identify 6 pieces of information that might be found on a Material safety data Sheet

Answer 9

1. Composition and ingredients
2. Hazard identification and classification
3. Handling and storage requirements
4. Exposure limits and controls
5. Stability and reactivity
6. First aid requirements

Question 10

The purpose of Occupational Exposure Limits and explain the application of LTEL and STEL.

Answer 10

OELs are levels of airborne contamination of hazardous substances, based on time averages, which should be not be exceeded.

OELs are usually given both:

Long Term Exposure Limits (LTELs) (of 8 hours duration and intended to protect against the chronic effects of hazardous substances) and

Short term Exposure Limits (STELs) (of 15 minutes duration and intended to protect against possible acute effects).

Question 11

Limitations with the principle of OELs

Answer 11

• They do not take into account rate of work (increased respiration will increase the amount inhaled)
• They only relate to airborne contamination
• They are based on data which may not be totally accurate
• Not all hazardous substance have an assigned OEL.

Question 12

Outline the differences between acute and chronic health effects

Answer 12

Acute health effects

After short duration or single exposures
Often reversible
Symptoms remain for short duration

Chronic health effects

After long duration or repeated exposures
Often irreversible
Symptoms remain for long periods

Question 13

The hierarchy of control using the acronym E.R.I.C.P.D.

Answer 13

Eliminate the hazard and hence eliminate the risk.

Reduce the hazard by using something less harmful.

Isolate the hazards from the workers.

Control the risk by engineering and behavioural means.

PPE to used for the residual risk

Discipline in the form of procedures and supervision

Question 14

Requirements for inspection of a local exhaust ventilation system

Answer 14

• LEV systems should be examined after installation and every 14 months.
• Inspections must be carried out by a competent person
• Records to be kept for 5 years

Question 15

Give 6 reasons why a local exhaust ventilation system (LEV) may become ineffective

Answer 15

1. Damaged ducting
2. Blocked or defective filters
3. Poor performance of fans (reduced face velocity)
4. Workers not turning LEV on when needed
5. Poor maintenance
6. Lack of inspection and testing

Question 16

What is meant by dilution ventilation and the limitations of this type of control with regard to airborne contamination?

Answer 16

Dilution ventilation is a means of introducing fresh air into a general area. It can be achieved by opening doors and windows and supplemented by the use of fans and extractors.

Because of the general nature of the ventilation it would not be suitable for areas where there is a large amount of contamination or in ‘dead’ areas of buildings where the air flow isn’t felt.

Question 17

Identify 6 suitable precautions to take when dealing with biological agents

Answer 17

1. Eradication – try to eliminate the source of biological hazard
2. Substitute harmful strains of bacteria for less harmful ones if possible
3. Containment – using enclosures to prevent escape
4. Sharps control arrangements and facilities
5. Immunisation / vaccination
6. Personal protective equipment

Question 18

Outline the hierarchy for managing waste

Answer 18

• Prevention
• Reduction
• Re-use
• Recover
• Disposal

Question 19

Outline the factors to be taken into account when undertaking an assessment of health risks from a hazardous substance to be used in the workplace

Answer 19

• the nature of the substance (e.g. whether it was toxic, corrosive, or carcinogenic);
• the form it will take when used (e.g. fume, dust);
• likely route of entry into the body (e.g. inhalation, absorption through skin);
• the potential ill health effects;
• the frequency and duration of use;
• how it will be used, stored and decanted;
• the likely level of exposure;
• who will be exposed;
• relevant workplace exposure limits;
• adequacy of existing control measures.

Question 20

Identify four possible routes of entry of a hazardous substance into the body.

Answer 20

1. Inhalation the most significant route of entry is breathing in airborne material;
2. Absorption enters the blood stream through the skin;
3. Injection forced through the skin (puncture wound).
4. Direct contact through an open wound eg abrasion

Question 21

Describe the differences between acute and chronic health effects following exposure to hazardous substances.

Answer 21

Acute effects may be experienced from a single, short exposure to the substance and the symptoms appear almost immediately. The symptoms are usually reversible.

Chronic effects are experienced after long term or repeated exposure, sometimes over many years before the ill health effects are detectable. Chronic effects are usually irreversible.

Question 22

Identify the factors that could affect the level of harm experienced by an employee exposed to a toxic substance.

Answer 22

Toxic- the effects of toxic substances on the body are often serious and small doses may result in serious ill health or death. Toxic substances are often referred to as poisonous.

Question 23

Identify the information that should be included on a manufacturer’s safety data sheet supplied with a hazardous substance.

Answer 23

Manufacturers are required to provide information on substances they supply recipients, telling them about the substance, the hazards it presents and any issues regarding the safe use, storage and disposal of the substance. This is done in the form of a manufacturer’s safety data sheet (SDS), which is a document organised under 16 standard headings. These are:

1. Identification of the substance / preparation and company - e.g. sodium hydrosulphite and manufacturer’s details.
2. Hazard identification - e.g. harmful if swallowed.
3. Composition / information on ingredients - colour, powder, liquid etc.
4. First aid measures - e.g. remove contaminated clothing immediately and dispose of safely, remove casualty into fresh air and keep calm, seek medical aid.
5. Fire-fighting measures - e.g. the only suitable extinguishing medium is a large quantity of water, do not use foam, sand or gas extinguishers.
6. Accidental release measures - e.g. ensure adequate ventilation; do not discharge into drains or surface water.
7. Handling and storage - e.g. avoid contact with small amounts of water, protect from moisture, and avoid influence of heat.
8. Exposure controls / personal protection - e.g. do not eat, drink or smoke during work time, wear protective gloves
9. Physical and chemical properties.
10. Stability and reactivity - e.g. violent reaction with water.
11. Toxicological information - e.g. non-irritant effect on skin.
12. Ecological information - e.g. consumes oxygen from water.
13. Disposal considerations - e.g. dispose at an authorised special waste disposal site.
14. Transport information.
15. Regulatory information (Hazard statements and Precautionary statements) – these now are individually numbered as it the hazard pictograms.
16. Other information.

Question 24

Explain the meaning of the term ‘workplace exposure limit’.

Answer 24

“The maximum concentration of an airborne substance averaged over a reference period of time to which employees may be exposed by inhalation.”

Question 25

Explain the meaning of the term ‘dilution ventilation’

Answer 25

Dilution ventilation is a means of introducing fresh air into a general area. It may be achieved by the opening of doors and windows and supplemented by the use of fans and extractors.

Dilution ventilation is not suitable for work situations where there may be exposure to substances with high toxicity or in ‘dead’ area of the building where there may be a large amount of contamination and air flow is not efficient.

Question 26

Describe the respiratory defence mechanisms of the body against atmospheric dust.

Answer 26

Nasal hair and mucus lining – which traps dust particles and they are then expelled through sneezing when the nasal cavity is cleared

Reflex actions – coughing and sneezing to quickly expel the dust particles from the nose and throat;

Ciliary escalator – the bronchial system is lined with small hairs known as cilia. These hairs stop the larger dust particles from travelling to the lungs by trapping the particles and then using the movement of the small hairs to move the particles back up to the throat. This is then coughed up or swallowed.

Question 27

Outline the control measures that could be used to minimise the health risks from the use of hazardous substances in the workplace.

Answer 27

• Change the process or activity;
• Replace it with a safer alternative, such as a chemical with non-hazardous properties;
• Use it in a safer form, such as granules rather than fine powders.

Question 28

For each of the following agents, outline the main health effects AND identify a typical work-place situation in which a person might be exposed:

Answer 28

a) Carbon monoxide

Carbon monoxide is an exhaust gas produced from fuels such as petrol and diesel. It is easily inhaled, taken up by the haemoglobin in the blood, produces carboxyhaemoglobin which then blocks the uptake of oxygen, which can result in loss of consciousness, and death over time.

The human body is not able to protect itself against the inhalation of carbon monoxide.

b) Silica

Crystalline silica is a solid substance which exists in several forms. It is transparent and colourless when pure, and insoluble in solvents and water. It occurs in mining, tunnelling, quarrying and pottery manufacture amongst others. Health effects are primarily due to inhalation. It causes a disease which is known as Silicosis, characterised by shadows on a chest x-ray. Silicosis is a form of lung fibrosis, (thickening or scarring of lung tissue) which manifests itself in shortness of breath. This may occur some months after exposure. Silicosis may also result in sufferers being more vulnerable to other diseases such as tuberculosis. Acute silicosis can be fatal within months of onset.

The human body is not able to protect itself well against the inhalation of silica. The dust collects in the lower lungs where the macrophages attempt to destroy the collected dust particles. There may be some success over time but it does result in the scarring of lung tissue and long term ill health effects.

c) Legionella bacteria

Legionellosis is the collective name given to the pneumonia-like illness caused by legionella bacteria. Legionnaires’ disease is a potentially fatal form of pneumonia and everyone is susceptible to infection. However, some people are at higher risk, including:

• people over 45 years of age;
• smokers and heavy drinkers;
• people suffering from chronic respiratory or kidney disease; and
• anyone with an impaired immune system.

The risk of exposure to legionella bacteria should be assessed under the requirements of the Control of Substances Hazardous to Health Regulations 2002. In order to support employers in fulfilling their duties and maintaining suitable and sufficient controls with regard to the risk of exposure to legionella the HSE issued an ACoP (Legionnaires disease – The control of legionella bacteria in water systems – L8). Appropriate controls must be used in workplaces to manage the risk of exposure. The controls include:

• ensuring a suitable and sufficient risk assessment is carried out by a competent person;
• the preparation and implementation of a written control scheme involving the treatment, cleaning and maintenance of the system;
• appointment of a named person with responsibility for the management of the control scheme;
• the monitoring of the system by a competent person;
• record keeping and review of procedures developed within the control scheme.

d) Hepatitis virus

Blood-borne viruses are viruses that some people carry in their blood and which may cause severe disease in certain people and few or no symptoms in others. The virus can spread to another person, whether the carrier of the virus is ill or not.

Hepatitis B virus (HBV), hepatitis C virus and hepatitis D virus, which all cause hepatitis, a disease of the liver;

These viruses can also be found in body fluids other than blood, for example semen and breast milk. Other body fluids or materials such as urine, faeces, saliva, sputum, sweat, tears and vomit carry a minimal risk of blood borne viruses.

Therefore the occupations at risk from exposure to blood borne infections are:

• health professionals;
• care services;
• laboratory workers;
• dentists;
• emergency response teams.

The human body protects itself against blood borne viruses through the white blood cellular response and the use of macrophages to engulf and destroy the viruses. There may be limited success due to unique way in which viruses invade and overtake cells in the body.

Question 29

There are three general classifications of hazards, each of which contains a number of such
categories:

Answer 29

• Physico-chemical hazards – those that are caused by the intrinsic physical or chemical properties of the substance.

• Explosive
• Oxidising
• Extremely flammable
• Highly flammable
• Flammable

• Toxicological hazards – those that arise from a chemical causing harmful effects to living organisms, which in practice normally means death, injury or adverse effects in humans when ingested, inhaled or absorbed through the skin. Toxic effects may be
acute or chronic, local or systemic, and reversible or irreversible.

• Very toxic
• Toxic
• Harmful
• Corrosive
• Irritant
• Sensitising
• Carcinogenic
• Mutagenic
• Toxic for reproduction

• Environmental hazards – those that relate to the potential of a chemical to damage one or more environmental compartments (i.e. the air, soil or water, including groundwater).

• Toxic or harmful to aquatic organisms
• Long-term effects such as persistence
• Toxic to the non-aquatic environment
• Dangerous for the ozone layer

Question 30

The definitions of the categories of danger posed by chemicals within the general
toxicology classification are as follows:

Answer 30

• Very Toxic - substances and preparations are those that in very low quantities cause death or acute or chronic damage to health when inhaled, swallowed or absorbed via the skin.
• Toxic - substances and preparations are those that in low quantities cause death or acute or chronic damage to health when inhaled, swallowed or absorbed via the skin.
• Harmful- substances and preparations are any that may cause death or acute or chronic damage to health when inhaled, swallowed or absorbed through the skin.
• Corrosive - substances and preparations are those that may, on contact, destroy living tissues. The following examples of corrosive substances may be encountered in the course of construction work:

Acids – sulphuric acid and hydrochloric acid in chemical cleaners, e.g. for masonry, brickwork.
Alkalis – cement, lime or agents used as chemical cleaners.
Gases and vapours – hydrogen sulphide.
Vapours – from resins, paints and thinners.

• Irritant - these are non-corrosive substances and preparations which through immediate, prolonged or repeated contact with the skin or mucous membrane may cause inflammation.
• Sensitising - these are substances and preparations that may cause an allergic reaction.
• Carcinogenic - substances and preparations are those which, if inhaled or ingested or absorbed by the skin, may induce cancer or increase its incidence. For the purposes of classification under the CHIP Regulations, carcinogens are divided into three categories,

Category 1 - being substances which are known to be
carcinogenic to humans;
Category 2 - where there is sufficient evidence to provide a strong presumption of human carcinogenicity; and
Category 3 - where there is concern
for humans about carcinogenic effects but the available information is not adequate for making a satisfactory assessment.

Question 31

Organisations are responsible for the safe-handling and storage of waste materials. The main environmental concerns which should be considered are:

Answer 31

• Likelihood of air pollution
• Likelihood of land pollution
• Likelihood of water pollution
• Requirements of waste disposal

Question 32

Typical sources of air pollutants include:

Answer 32

Sulphur dioxide
Suspended particulate matter
Oxides of nitrogen
Carbon monoxide 
Hydrocarbons 
Carbon dioxide

Question 33

Air pollution, control measures include:

Answer 33

Redesigning the process
Use of clean technology 
Use of low sulphur fuels 
Air filtration before discharge to the atmosphere 
Regular maintenance of equipment

Question 34

Water may be polluted by a number of industrial processes including

Answer 34

Factory / industrial waste
Foul / surface water drains wrongly connected
Solvents / oil spills running into drains

Question 35

The main industrial water pollutants are:

Answer 35

Cyanide

Carbon dioxide

Question 36

Water pollution, control measures include

Answer 36

Redesigning the process
Use of clean technology 
Use of low sulphur fuels 
Air filtration before discharge to the atmosphre
Regular maintenance of equipment

Question 37

Personal protective equipment (PPE)

Answer 37

Personal protective equipment is often used as part of control measures. This also needs checking and maintenance because, if it fails, it no longer provides
protection and exposes the wearer to danger. The users need to know exactly what they are doing, and so do the supervisors.

Question 38

Exposure Limited Wood Dust

Answer 38

Both hardwood and softwood dusts have a Workplace Exposure Limit (WEL) of 5mg/m3 which must not be exceeded. These are limits placed on the amount of dust in the air, averaged over an eight-hour working day. However, you must reduce exposure to wood dust to as low as ‘reasonably practicable’.

Question 39

Wood dust is a substance hazardous to health
because it can cause serious non-reversible health
problems, including:

Answer 39

■ skin disorders;
■ obstruction in the nose, and rhinitis;
■ asthma;
■ a rare type of nasal cancer

Question 40

Control which should be used when exposed to wood dusts are:

Answer 40

• Elimination or substitution
• Use of ventilation systems
• Training and awareness of staff
• Good welfare facilities
• Provision of RPE and PPE

Question 41

What makes up an LEV system?

Answer 41

A typical LEV system will have:

• Hood(s) – to collect airborne contaminants at, or near, where they are created (the
  source) .
• Ducts – to carry the airborne contaminants away from the process.
• Air cleaner – to filter and clean the extracted air.
• Fan – which must be the right size and type to deliver sufficient ‘suck’ to the hood.
• Discharge – for the safe release of cleaned, extracted air into the atmosphere.

Question 42

What do I need to do once the LEV is installed?

Answer 42

The law says that you need to make sure it carries on working properly. The user manual, logbook and training will help you do this. Most LEV systems need a thorough examination (see below) by a competent person and test once each year (legally, you are allowed no more than 14 months between tests) to make sure it
works well and continues to protect your employees. Some LEV systems (such as those controlling more critical or high-hazard processes) need more frequent thorough examination and testing. COSHH requires more frequent testing for some processes.

If you have an LEV system that hasn’t been commissioned, you will need to have its performance tested to ensure that it is adequately controlling exposure.

Question 43

Prevent: Where possible think about eliminating or reducing the amount of cement used and contact with it. Consider:

Answer 43

• avoiding exposure to cement powder by using pre-mixed concrete / mortar
• using work methods that increases the distance between the worker and the substance such as longer handled tools
• rotating cement bags to ensure they are used before the shelf date. The ingredient added to reduce the risk of allergic contact dermatitis is only effective for a limited period.

Question 44

Cement: Even if you stop some of the risk this way, you may still do other work that might involve contact with cement. Control the risk by:

Answer 44

• Gloves – gloves should be waterproof and suitable for use with high pH (alkaline) substances; eg marked with EN374:2003 and tested for use with “alkalis and bases” (class K) – some nitrile or PVC gloves may be suitable. Breakthrough time and permeation rate should also be suitable for the type and duration of the work. Gloves should be long and /or tight fitting at the end to prevent cement being trapped between the glove and the skin.
• Footwear – suitable footwear, such as wellington boots, should be used where large concrete pours are taking place. If standing in cement, these should be high enough to prevent cement entering the top of the boot.
  Waterproof trousers – when kneeling on wet products containing cement, appropriate waterproof trousers should be worn or, if screeding, use appropriate waterproof knee pads or knee boards. Minimise any time spent kneeling. Wear trousers over the top of boots. This stops cement getting into them.
• Washing – wash off any cement on the skin as soon as possible. Workers should be encouraged to wash exposed skin at breaks and after work. Good washing facilities are essential. There should be hot and cold or warm running water, soap and towels. Basins should be large enough to wash forearms. Showers may be needed in some situations where workers could get heavily covered in cement. Use emergency eyewash to remove any cement that gets into eyes.

Skin care products – these can help to protect the skin. They replace the natural oils that help keep the skin’s protective barrier working properly.

Train: Workers need to know how to use the controls properly. They also need to be aware of the signs and symptoms of dermatitis. Finding skin problems early can stop them from getting too bad.

Question 45

Monitoring exposure to hazardous substances

Answer 45

Monitoring normally means air sampling but it may also involve taking biological
samples, eg breath or urine. Monitoring normally makes reference to ‘Workplace
Exposure Limits’ (WELs) published by HSE.

You may consider combining aspects of the basic and detailed surveys. This
may involve the simultaneous use of smoke tubes, air velocity meters, chemical
indicator tubes and personal sampling equipment.

Question 46

Hazardous Substance - Types of PPE

Answer 46

Respirators
Protective gloves
Protective clothing
Protective footwear
Eye protection

When deciding about PPE ask the supplier, your trade association or the manufacturer.

Is it suitable for the conditions of the job?
Does it offer the right level of protection?
What sort of training or maintenance is required?
How do I know when it needs replacing?
It is important that employees know why they need PPE and are trained to use it correctly. Otherwise it is unlikely to protect as required.

Does it fit correctly?

How does the wearer feel? Is it comfortable?
Are all items of PPE compatible?
Does PPE interfere with the job being done?
Does PPE introduce another health risk, eg overheating, entanglement with machinery?
If PPE needs maintenance or cleaning, how is it done?

Question 47

Where control measures are in place it is important to use them properly.

This includes:

Answer 47

• wearing any PPE necessary;
• using control equipment;
• following hygiene procedures;
• warning supervisors if anything appears to be wrong.