A hazard is an object or material which may release energy during an incident and/or cause an adverse effect.

Energy has many different forms, it may be kinetic, such as the energy of motion, potential, such as that stored in a spring or by a weight situated on a ledge. It may also be in chemical, electrical, radiation (nuclear) or heat forms. Hazards may often be identified, by the very fact that they usually possess stored energy.

A risk is the likelihood that exposure to a hazard will result in injury , disease or other loss,(in some circumstances the term may refer to beneficial outcomes of an incident).

There are two components of risk – likelihood (probability) that an incident will occur, and the consequences (outcomes or severity) of the incident, the combination of these factors constitute ‘risk’.

The magnitude of risk to an organisation, may be increased by the ‘outrage factor’, or the adverse effect on public (and other interested parties) perceptions of an organisation, after an incident has occurred.

Once hazards have been identified, an assessment of the risks associated with each hazard determines the likelihood of injury or illness (loss) being caused by that hazard.

When assessing the risk associated with any hazard, it is necessary to ask the following questions:

• Who is exposed to the hazard?
• How often are people near the hazard?
• What if a release of energy occurs?
• Has this hazard already caused any problems?
• How easily could someone be hurt?
• How common is it for this hazard to cause problems in other workplaces?
• Which factors relating to that hazard need to be taken into account, according to health and safety law?
• Which factors or specific aspects of the work are increasing the likelihood of injury or illness?

It is important to record the identified hazards and classify them according to type of potential injury or illness, for example:

• hazards that could kill or cause serious injury, permanent disability or ill health;
• hazards that might cause injury or illness resulting in an employee being off work for several days; or
• hazards that might cause injury or illness resulting in an employee requiring first aid.

Risk assessment also involves deciding whether it is likely that someone could be hurt by being exposed to those hazards, and establishing whether it is:

• very likely
• likely
• unlikely
• very unlikely

to cause harm in the workplace. Once these assessments have been made, plans to control risks can be developed.

These are hazards that a caused by the use, storage and handling of chemicals.

Figures from Worksafe Australia Report 1996.

Fatal Exposures

#Yearly average: Deaths from occupational exposures, 1989-1992

Cause of Death

#Comparisons of Causes of Death (Australia 1992)

A shopping centre car park has a number of employees that carry out a variety of duties. Some of them work on the car park booths to collect tickets and parking fees. Other employees are usually involved in relieving booth operators and roaming around the carpark to attend to entry gates, and occasionally directing traffic. The main hazardous substance exposure is carbon monoxide (CO) from the exhausts of cars. The car park is predominantly naturally ventilated with a few areas of the car park with mechanical ventilation. The car park booths are not ventilated. The booth collectors can be exposed to high levels of CO during peak periods, usually at lunch and closing times. The person roaming around relieving staff is also exposed to high CO levels when relieving booth operators. during meal breaks, and when directing traffic. Directing traffic exposes this person to high CO levels due to working in heavy traffic and near the vehicles. CO exposure may cause headaches, nausea, weakness and dizziness. CO combines with haemoglobin in the blood to reduce the supply of oxygen to the body. To control exposure the car park booths should be mechanically ventilated with fresh air drawn form a source away from vehicle exhausts. Exposure for the person acting as relief for the booth operators can only be reduced by providing tasks to be carried out with no CO exposure and by reducing booth CO levels. Exposure to CO can occur in any workplace where the combustion of fuels occurs. This includes warehouses, automotive repair and service centres, toll collecting, drive through outlets and car auction houses.

Health effects from exposure to hazardous substances can be either chronic or acute.

• Acute effects Materials which are toxic enough, that a single large enough dose can kill or cause serious injury are described as acutely toxic.

The effects of exposure to the chemical are immediate.

e.g. exposure of the skin to a concentrated acid will result in burns to the skin.

• Chronic effects Toxic materials are present in low amounts, low enough to cause no immediate short term problems, but prolonged exposure, even at low levels can cause health damage.

Some of the long term problems directly attributed to chronic toxins include, migraine and nausea, liver disease, kidney failure, various cancers, dermatitis, asthma, bronchitis and allergic responses.

Poisons can cause injury in any of three ways:

• Interference with respiratory processes.
• Direct destruction of tissue.
• Interference with bodily processes.

(i) Asphyxiants:

Dilute the air by taking the place of oxygen. Death can occur rapidly if the oxygen level falls too low. Oxygen makes up 21% of normal air, it is considered dangerous if this drops to 18%.

Asphyxiating gases include carbon dioxide, hydrogen, argon, nitrogen, methane.

(ii) Blood Asphyxiants:

These combine with red blood cells which carry oxygen from the lungs to tissues throughout the body. The oxygen carrying capacity of the red cells is then reduced, leading to less oxygen reaching the body tissues.

One of the most important of this type is carbon monoxide.

(iii) Tissue Asphyxiants:

These are picked up and carried by the blood to the body cells. The poison is released by the blood into the cells, which then interferes with the cells ability to use oxygen, even if it is present. The cells then begin to die, leading to tissue damage or death.

Cyanide works in this way.

(iv) Respiratory Paralysis:

Some poisons paralyse the lungs when inhaled or ingested.

Examples are ether, chloroform, carbon disulfide.

(i) Corrosive or caustic substances burn skin or interior tissue if swallowed. Death follows by loss of fluid. Examples are sulfuric, hydrochloric and nitric acids, sodium and potassium hydroxide.

(ii) Some gases, e.g. Phosgene, oxides of nitrogen and oxides of phosphorus form corrosives when mixed with moisture in breathing passages.

(iii) Some gases cause irritation and eventual blockage of breathing passages. Some examples are sulfur dioxide, ammonia, and hydrogen sulfide.

Examples

• Benzene: destroys bone marrow where the blood cells are formed, leading to leukaemia.
• Strychnine: causes uncontrollable muscle spasms, even violent enough to break bones.
• Arsenic, some pesticides: destroys kidneys and liver.
• Organophosphates: used in insecticides and nerve gases, they interfere with the transmission of nerve impulses.
• Lead: interferes with the nervous system
• Cadmium: can damage the lung severely if inhaled as fume. Salts of cadmium damage the kidneys.

The Lungs

The lungs essentially serve as a gas exchange mechanism for the body. The two main groups of substances which cause lung damage are;

• Gases and vapour which mix with lung moisture and form corrosive liquids. e.g. chlorine gas.
• Small particles which lodge in the narrow airway of the lung and cause emphysema and fibrosis diseases along with the possibility of lung cancer. e.g. asbestos.

The Kidneys

The kidneys filter impurities from our blood. They can be affected by a wide range of chemicals. Substances which affect the kidneys are called nephrotoxins. Even small amounts of chemical in the blood can affect the kidneys due to the chemical concentration building up as the material is filtered from the blood

The main types of nephrotoxins are:

• Heavy metals such as mercury, lead cadmium etc.
• Chlorinated hydrocarbons such as chloroform, trichloroethane methylene chloride.
• Aromatic hydrocarbons such as benzene, toluene and xylene.

The Liver

The liver is a very complex organ. It essentially breaks down or helps to break down any materials which enters the body. This includes fats and carbohydrates in our foods and also toxic materials which enter the body. The liver breaks down toxic materials and is therefore prone to damage by chemical exposure.

Chemicals which can affect the liver are called Hepatotoxins. Hepatotoxic materials typically cause sections of the liver to die and/or an uncontrolled deposition of fatty materials in and around the liver. Some substances cause liver cancer.

Examples of hepatotoxins are chlorinated hydrocarbons, alcohol, some solvents, vinyl chloride monomer, some heavy metals and some vitamins taken in high concentration.

The Bladder

The bladder stores urine and is the receptacle of waste from the kidneys. As it can store toxic materials for some time, it can be prone to damage.

Examples of materials which cause bladder damage are aromatic amines, chlorinated hydrocarbons and some pesticides.

The routes of entry for chemicals are:

• Breathing or inhalation of gases, dusts, vapours, aerosols, fumes.
• Skin, especially through wounds or damaged skin.
• Digestive tract, by ingestion and swallowing.

Our lungs are a very effective organ for extracting oxygen form the air and absorbing it into the blood. But this also means that anything in the air, whether it is a gas, dust particle, or liquid aerosol droplet, if it is fine enough can gain rapid access to the blood, and from there to any part of the body.

You might notice gases, dusts and fumes by smoke, a haze in the air, or dirty nose. Only big particles are stopped by hairs and mucous in the air passages. Our body has no natural protection to stop gases entering the lungs.

• Poisonous Chemicals

When poisonous chemicals enter our bodies through breathing, they can cause:

headache

confusion

unconsciousness

death

Examples of poisonous chemicals are:

hydrogen sulfide

hydrogen cyanide

carbon monoxide

• Solvents

When solvent vapours are breathed in, they can cause:

loss of sensation

headaches

nausea

tiredness

intoxication

death

Examples of solvents are:

Trichloroethane Lack of concentration or co-ordination

Isocyanates in polyurethane "Solvent syndrome" (long term condition involving memory loss and irritability.)

• Asphyxiants

Asphyxiants cause death through lack of oxygen

Examples of asphyxiants include:

nitrogen

carbon dioxide

• Inorganic dusts

Inorganic dusts may cause:

blocked noses

eye irritation

cancer (asbestosis and silicosis)

Examples of inorganic dusts include:

asbestos

silica

talc

iron

cement

mineral fibre

mica

• Organic dusts

Organic dusts can cause:

irritation

sensitisation

cancer

Examples of organic dusts include:

wood dust

coal

cereals

seeds

feathers

The skin covers the body and protects it against chemical and mechanical damage. The skin also has an important role in controlling body temperature and conserving water.

The skin is made up of three layers:

• Epidermis The surface layer cells have a high level of keratin (the protein in nails and hair);

• Dermis The middle layer firms the skin;

• Subcutis Connective and fatty tissue to absorb shock and insulate the body.

The skin also contains:

• sweat glands;
• hair follicles;
• nerve fibre endings.

• Mechanical Damage

• Irritation to the Skin

The skin produces substances (amino acids, lactic acids and lactate) to try and prevent or reduce the amount of irritation. Sweat will also dilute the concentration of the contact material.

Some chemicals will easily penetrate the skin and eye tissues and enter the body. Cuts, scrapes, grazes, punctures and sweating will speed the absorption rate. The diagram below gives an idea of the chemical resistance of the skin.

Surface Layer Keratin Layer

Epidermal

Cells

Pigment

Cells

Basal Cells

Duct

Sebaceous

(oil) Gland

Sweat

Gland

Hair Follicle

Types of Skin Damage by Chemicals and Examples

You might notice a chemical on your skin by a burning sensation, irritation, a discolouration, a strange feeling, or a smell. If the chemical is not removed, it may be absorbed into your body.

High temperatures and sweating increase absorption rate. Some areas of the body have higher absorption rates. These include the hairy parts of the body (scalp, armpits, groin) where the skin is thinner.

At the workplace, ingesting chemicals is the least common route of entry. The amount is generally not large, and the nature of the digestive system prevents absorption of many hazardous chemicals. Generally chemicals are ingested in the following ways:

• Dirty hands by licking fingers to turn pages.

from biting fingernails.

• Contamination when cigarettes, food or drink are taken into workplaces where chemicals are used.

• Splashes of chemicals when pouring (decanting).

from something being dropped.

The digestive system has various built-in defences which can reduce the chemical hazard:

• Hydrochloric acid in the stomach can inactivate some toxins;
• The small intestine does not absorb all chemicals;
• The liver detoxifies many chemicals, but may cause some chemicals to become more toxic;
• Chemicals leave the body (excretion) via the faeces, urine, sweat or in exhaled breath. Use of the last of these is made in breathalyser tests.

You can usually notice a chemical you have swallowed by a distinctly different taste or smell. You may have a burning sensation, an irritation, a discolouration of your mouth, a strange feel, or a smell. Sometimes small amounts of chemical can be in food and not easily noticed. It is important to keep aware of any strange taste, smell or colour. This will help protect you from most problems. Other conditions can be recognised by the following:

• Combustion fire
• Chemical explosion when two chemicals react together
• Physical explosion electrical
• Mechanical explosion hydraulics
• BLEVE burning liquid expanding vapour explosion
• Dust explosion dust and air mixture, e.g. wheat silo
• Implosion

• Asphyxiants
• Toxic Substances
• Corrosives
• Irritants
• Sensitisers
• Carcinogens
• Mutagens
• Teratogens

• Pollution
• Fire

The health effects of chemicals and hazardous substances are determined from human evidence or animal exposure. There are three primary ways of systematically identifying chemical hazards:

• Counting the Bodies
• Epidemiological Studies
• Laboratory Tests on Animals/Bacteria

Workers notify their problems to superiors or their doctors. Clinical observation by doctors and other health workers. Worker’s compensation statistics. National data.

Case Study:

A group of workers experiencing similar problems are matched with a control group in as many ways as possible (sex, age, occupation, etc.). If the group with problems demonstrates a particular trait (e.g. exposure to a given substance or stressor) not found in the control group, then a link may be established with a particular chemical.

Cohort Study:

Two defined groups are matched in every possible way except exposure to a chemical. Observations are made over a period of time to determine if a link exists between the chemical and the exposed group. Such observations may be retrospective (studying personnel records of people who worked in a particular environment over a period of years and following up on their present state) or prospective (a group is selected and observations continue into the future).

Test results obtained from animal studies cannot be directly extrapolated to humans. However, they frequently give an indication of the likely human response to a chemical. Dealing with rats not people. Very little long term monitoring is usually done.

All new chemicals, and many existing chemicals, have to undergo vigorous testing before being allowed onto the market. One of these tests is to use animals such as rats, rabbits or beagle dogs. The test animals are either fed the material, or absorb it through their skin or by breathing it in. When half of the test animals are dead, the amount of material that caused this is recorded as a Lethal Dose 50% or LD50. The exposure time is 4 hours and follow up work is carried out for 2 weeks.

The following table, adapted from Approved Criteria for Classifying Hazardous Substances [NOHSC:1008(1994)], shows how materials are classified according to LD50 information. As a general rule, the higher the LD50 figure, the safer the material.

*LD50 A dose of a substance that produces death in 50% of a population of experimental animals. It is usually expressed as milligrams per kilogram (mg/kg) of body weight.

#LC50 A concentration of a substance (usually in air) that is estimated to produce death in 50% of a population of experimental animals on inhalation for a short period of time.

1. If you had 10 people who weighed 70kg each, how much of the material with an LD50 of 25mg/kg would they need to absorb to kill 50% or 5 people?

2. If you had 10 children who weighed 30kg each, how much of the material with an LD50 of 25mg/kg would they need to absorb to kill 50% or 5 children?

• Children are at greater risk because of their lower body weight.
• LD50’s are lethal doses that killed 50% of the animal test group. Figures for LD5 or Lethal Dose 5% can also be obtained, where only 5% of the animal test group died.
• Animals are not humans. Just because the LD50 is quiet high, and therefore "safe", you should still treat all chemicals with care.

90 day inhalation/ingestion studies to check for obvious effects of a chemical on an animal’s organs.

Material Safety Data Sheets should tell you if the material will cause skin, eye and lung irritation. This is primarily based on animal testing data, but also from medical data. Once someone is sensitised to a material, they may never be able to work with it again.

Chemical is applied to animal’s skin or eyes for response. (DRAIZE Test.)

Some substances accumulate or build up in the body over a period of time with constant exposure. They can be either toxic or harmful.

The following table, adapted from Approved Criteria for Classifying Hazardous Substances [NOHSC:1008(1994)], shows the routes and dose ranges.

Particular care must be taken with carcinogenic (cancer causing), mutagenic (capable of causing genetic damage) and teratogenic (capable of causing birth defects) materials.

Animal and bacteria tests are used to determine possible human chronic effects.

Life time inhalation/ingestion studies to check for long term disease/cancer in animals. Life span for a rat is approximately two years.

A chemical is added to a bacterial culture and incubated for 2 - 3 days for growth or mutation in bacterial cells.

Observation of animal behaviour to check for effects of chemical exposure on the control nervous system.

Multi-generation studies of animals to check for reproductive effects.

This information was compiled using results of animal studies and the study of human epidemiology. The body responsible for the information is the International Agency for Research on Cancer (IARC). The IARC classify carcinogens according to the following criteria:

The chemical, group or mixture of chemicals or industrial process or occupational exposures are definitely carcinogenic to humans. The category is only used when the evidence is strong enough for a causal relationship to be established between the exposure and cancer in studies in which chance, bias and confounding could be ruled out with reasonable confidence. (i.e. sufficient evidence in humans).

e.g. Asbestos (lung), Benzene (bladder), Vinyl Chloride monomer (liver).

The chemicals, group or mixture of chemicals or industrial process or occupational exposures are probably carcinogenic to humans. Good evidence of cancer in humans.

e.g. Acrilonitrile, nickel

The chemicals, group or mixture of chemicals, or industrial process or occupational exposures are possibly carcinogenic to humans. Evidence of cancer in animals.

e.g. DDT, ethylene oxide.

The chemicals, group or mixture of chemicals or industrial process or occupational exposures in this category are not classifiable as to carcinogenicity in humans. The substances are placed in this category when they do not fall into any other category.

e.g. Bitumens, toluene diisocyanate (TDI).

The chemicals, group or mixture of chemicals, or industrial process or occupational exposures are probably not carcinogenic to humans. Evidence for the lack of carcinogenicity must come from both humans and animals, or if there is inadequate evidence in humans, there must be supporting evidence from other data.

Some carcinogens are prohibited for use or are notifiable carcinogens.

2-Acetylaminofluorene [53-59-3]

Aflatoxins

4-Aminodiphenyl [92-67-1]

Amosite (brown asbestos) [12172-73-5]

except for removal and disposal purposes and situations where amosite occurs naturally and is not used for any new application.

Benzidine [92-87-5] and its salts (including benzidine dihydrochloride [531-85-1])

bis(Chloromethyl) ether [531-85-1]

Chloromethyl methyl ether [107-30-2]

(technical grade which contains bis(chloromethyl) ether

Crocidolite (blue asbestos) [12001-28-4]

except for removal and disposal purposes and situations where crocidolite occurs naturally and is not used for any new application.

4-Dimethylaminoazobenzene [60-11-7]

2-Naphthylamine [91-59-8] and its salts

4-Nitrodiphenyl [92-93-3]

These substances:

• can only be used for bona fide research or analysis;
• where an exemption has been granted by the Authority.

(Source [NOHSC:1011(1995)] National Model Regulations Control of Hazardous Substances Part 2 - Scheduled Carcinogenic Substances)

Acrylonitrile [107-13-1]

Benzene [71-43-2]

when used as a feedstock containing more than 50% of benzene by volume.

Chrysotile (white asbestos) [12001-29-5

when used for the manufacture of asbestos products.

Cyclophosphamide [50-18-0] (cytotoxic drug)

when used in preparation for therapeutic use in hospitals and oncological treatment facilities, and in manufacturing operations.

3,3’-Dichlorobenzidine [91-94-1]

and its salts including 3,3’-Dichlorobenzidine dihydrochloride [612-83-9])

Diethyl sulfate [64-67-5]

Dimethyl sulfate [77-78-1]

Ethylene dibromide [106-93-4]

when used as a fumigant.

4,4’-Methylene bis(2-chloroaniline) [101-14-4-] - MOCA

2-Propiolactone [57-57-8]

o-Toluidine [95-53-4]

and o-Toluidine hydrochloride [636-21-5]

Vinyl chloride monomer [75-01-4]

Can only be used:

• if an assessment has been carried out;
• the Authority has been notified;
• certain conditions are met.

(Source [NOHSC:1011(1995)] National Model Regulations Control of Hazardous Substances Part 2 - Scheduled Carcinogenic Substances)

• Workload considerations calculated on work of normal intensity, under normal climatic conditions and 16 hours between shifts.

• Heavy or strenuous work increases breathing rate, thereby increasing the uptake of contaminants. Similarly, heavy physical work under adverse climatic conditions, such as excessive humidity or heat, or work at high altitudes, may lead to an increased uptake of contaminants.

Exposure standards are set by Worksafe Australia

Exposure standard means an airborne concentration of a particular substance in the worker’s breathing zone, exposure to which, according to current knowledge, should not cause adverse health effects nor cause undue discomfort to nearly all workers.

There are 3 categories of exposure standards:

• Time Weighted Average (TWA)
• Short Term Exposure Limit (STEL)
• Peak Limitation Values

The average concentration in air of a vapour, dust, gas or fume to which workers can be exposed for 8 hours per day, 5 days per week without suffering any short or long term health damage.

Units ppm parts of vapour or gas per million parts of contaminated air by volume.

mg/m³ milligrams of substance per cubic metre of air at 25^o C and one atmosphere pressure.

The lower the value the more hazardous the material:

e.g. Carbon Tetrachloride .1ppm 0.63 mg/m³

Carbon Monoxide 30ppm 34 mg/m³

Acetone 500ppm approx 1190 mg/m³

(Source Documentation of the Exposure Standards [NOHSC:10003(1996)])

Some substances can cause intolerable irritation or other acute toxic effects upon brief over exposure although the primary toxic effects may be due to long term exposure (chronic). Under these circumstances, exposure should be controlled.

STEL is the upper limit to which workers can be exposed for up to 15 minutes without suffering:

• intolerable irritation;
• chronic or irreversible tissue damage;
• narcosis (sleepiness) such that could cause workplace accidents.

Maximum of 4 exposures per day with 60 minutes between exposure.

e.g. Acetone 1000 ppm 2380 mg/m³

Isoycanates 0.07mg/m³

Methyl Ethyl Ketone 300ppm approx 890mg/m³

(Source Documentation of the Exposure Standards [NOHSC:10003(1996)])

For some rapidly acting substances and irritants, the averaging of the airborne concentration over an 8 hour period is inappropriate. The exposure time should not exceed 15 minutes.

A peak limitation value is the maximum concentration to which any worker should be exposed to at any one time. That is a concentration figure that cannot under any circumstances be exceeded.

e.g. Chlorine 1ppm 3mg/m³

Ethyl Acrylate 5ppm 20mg/m³

Glutaraldehyde 0.1ppm 0.41mg/m³

(Source Documentation of the Exposure Standards [NOHSC:10003(1996)])

When the body is exposed to two or more contaminants, an additive effect is obtained when contaminants have the same target organ or the same mechanism of action. In this situation, the total effect upon the body equals the sum of effects from the individual substances.

e.g. 2 + 2 = 4

Sometimes the combined effect of multiple exposure is considerably greater than the sum of the effects from the individual components. This phenomenon can be one of synergism or potentiation. Synergism occurs when both chemicals have an effect individually and a more than additive effect when together. Potentiation is when one chemical has an effect but the second chemical does not but enhances the effect of the former chemical on combined exposure

e.g. synergism 2 + 2 = 4

potentiation 2 + 0 = 6

*Source Exposure Standards in the Occupational Environment: Guidance Note and National Exposure Standards

1. What are the organs most commonly affected by chemicals?

2. What are:

(a) Chronic effects?

(b) Acute effects?

3. What is a LD₅₀?

4. What is the difference between a Peak Limitation Value and a STEL?

5. How do people come into contact with chemicals?

6. What kind of strategies could you put in place to prevent employees from ingesting chemicals?