NEBOSH NATIONAL GENERAL CERTIFICATE

Occupational health hazards

LEARNING OUTCOMES (I)

• classification of occupational health hazards (physical, chemical, biological, ergonomic) • commonly occurring occupational diseases and conditions arising from exposure to physical, chemical, biological and ergonomic hazards • meaning of terms; toxic, harmful, corrosive, irritant and the response of the body to substances with these properties

LEARNING OUTCOMES (II)

• the main routes of entry of hazardous substances into the body • the significance of the form taken by a hazardous substance ie gas, vapour, mist, aerosol, smoke fume, dust, liquid and solid • the concept of target organs and target systems • occupational exposure limits; distinction between MELs and OESs

LEARNING OUTCOMES (III)

• general principles and methods of air monitoring • methods that can be used for prevention and control of hazardous substances, with particular reference to workplace ventilation systems • main requirements of the Control of Substances Hazardous to Health Regulations 1994 • precautions needed during the storage, transport, use and disposal of dangerous substances

GENERAL ASPECTS OF OCCUPATIONAL HEALTH & HYGIENE

• what types of agent might represent an occupational health risk in the workplace?

• how do we go about evaluating the severity of the risk?

PRINCIPLES OF OCCUPATIONAL HYGIENE

•

Recognition/identification

of occupational health hazards • •

Measurement

of level or concentration

Evaluation

of likelihood and severity of harm •

Control strategies

available to reduce or eliminate risk

RECOGNITION

• • • •

chemical

– liquids, fumes, mists vapours, gases, dusts

physical

– radiation, noise, vibrations, temperature, humidity

biological

– bacteria, viruses, fungi

ergonomic

– body position, repetitive actions, work pressure

CHEMICAL HAZARDS

• absorption then attack on organs or metabolic processes –

toxic

response –

carcinogenic

response • contact then attack on the surface of the body –

corrosive/irritant

– response

dermatitic/sensitisation

response

BIOLOGICAL HAZARDS

• exposure to biological agents resulting in illness • types of biological agent include –

bacteria

–

viruses

–

fungi

PHYSICAL HAZARDS

• harmful energy absorbed by the body’s structure • energy derived from –

mechanical

sources • noise, vibration –

radiation

sources • ionising, non-ionising –

thermal

sources

ERGONOMIC HAZARDS

• concerns the physical, physiological and psychological relationships between people and work • specific areas include – – – –

perceptual responses work rates

and

fatigue man-machine interface anthropometrics

MEASUREMENT

•

continuously

– control strategy where the risk is high •

intermittently

– initial determination of hazard – spot measurement in an established process – routine check measurement

EVALUATION

•

harm

ful characteristics of the substance, energy or condition involved • concentration, intensity or

level

of the exposure to the harmful agent •

time

duration of the exposure

CONTROL

• elimination • substitution • change of work method • change of work pattern • isolation and segregation • engineering controls • personal protective equipment

ROUTES OF ATTACK ON THE HUMAN BODY

• route of entry (reach an area of penetration of the body) • process of entry (penetrate the outer cover of the body)

ROUTES OF ENTRY

• inhalation • ingestion • skin pervasion • injection • implantation • aspiration

PROCESS OF ENTRY

• absorption

– epidermis – lungs – gastro-intestinal tract

• direct entry into the body

TOXICOLOGY

-

the study of poisonous materials and their effects on living organisms • toxic substances –

systemic

• travel through the system –

local

• act only at the point of contact –

cumulative

• not readily excreted from the body • accumulated over a period of time • toxicity – LD50 to quantify the effects of a toxic agent –

Acute Toxicity

• harmful effect occurs quickly (seconds, minutes, hours) –

Chronic Toxicity

• harmful effect takes a long time to appear (months, years)

LOCAL AND SYSTEMIC EFFECTS

• local effects (confined to specific area where contact occurs) – skin – eye – respiratory tract • systemic effects (occur at organs distant from contact site) – liver – nervous system – bone – blood-forming organs

DEFENCE MECHANISMS OF THE BODY

• respiratory defence – physical filtration – phagocytosis • lachrymation • immune response • inflammatory response • fibrotic response

CHIP 2

• Chemicals (Hazard Information and Packaging for Supply) Regulations 1994 – category of danger – indication of danger – symbol

HEALTH EFFECTS CLASSIFICATION OF HAZARDOUS SUBSTANCES

• very toxic • toxic • harmful • corrosive • irritant • sensitising • carcinogenic • mutagenic • toxic for reproduction

APPROVED SUPPLY LIST

• general nature of the risk (

risk phrase)

“causes severe burns” • precautions to be taken

(safety phrase)

“keep out of reach of children”

LABELLING

• supplier information • name of substances or constituents • indication of danger • symbol • risk phrase • safety phrase

SAFETY DATA SHEETS

• composition • hazards • first aid • fire fighting • accidental release • handling/storage • exposure controls • personal protection • physical properties • chemical properties • stability/reactivity • toxicology • ecological information • disposal

CATEGORIES OF CHEMICAL AGENT

• toxic, including carcinogenic • corrosive and irritant • dermatitic and sensitising

FORMS OF CHEMICAL AGENT

• solids • liquids • dusts • fibres • mists • gases • fumes • vapours

TYPES OF TOXIC EFFECT

• respiratory irritants • chemical asphyxiants • haemolytic poisons • narcotics • nervous system poisons • metallic poisons • metallic and polymer fume fever • carcinogens – halogenated compounds – nitro-compounds – aromatic amines – polycyclic aromatic hydrocarbons – natural carcinogens – inorganic carcinogens – benzene

TOXIC AGENTS

• physical form(s) • mode of entry to body • target organs • symptoms of exposure – acute – chronic • occupations at risk

COMMONLY OCCURRING TOXIC SUBSTANCES

• lead • mercury • benzene • phenol • trichloroethylene • silaceous dust • asbestos • carbon monoxide

CORROSIVE AGENTS

• destroy living tissue • acids and alkalis • injury through – contact with skin and eyes – inhalation – ingestion

DERMATITIC AGENTS

• primary cutaneous irritants – contact dermatitis – at site of contact – recovery on removal of agent • cutaneous sensitisers – sensitisation dermatitis – initial sensitisation – trace contact enough to cause reoccurrence

SENSITISERS

• respiratory system – occupational asthma – inhalation of antigen causes bronchial constriction • sensitisation dermatitis – isocyanates – trace contact enough to cause reoccurrence

OCCUPATIONAL EXPOSURE LIMITS (I)

• designed to control the absorption of airborne contaminants into the body • measured in: –

ppm

(parts of vapour/gas per million parts of air) –

mg/m3

air) (milligrams of substance per cubic metre of • expressed as the concentration of an airborne substance averaged over a reference period – 15 minutes short term limit – 8 hours long term limit

•

OCCUPATIONAL EXPOSURE LIMITS (II)

•

Maximum Exposure Limit (MEL)

– maximum permissible concentration – has legal status – must not be exceeded – reduce exposure to as far below the MEL as possible

Occupational Exposure Standard (OES)

– concentration at which no evidence of harm – represents good practice – if exceeded, take steps to reduce down to OES – OES represents adequate control

OCCUPATIONAL EXPOSURE LIMITS (III)

• long term limits – time-weighted average concentration – conc. x exposure time averaged over 8 hours – designed to control chronic effects • short term limits – time-weighted average concentration – conc. x exposure time averaged over 15 mins – designed to control acute effects

SAMPLING OF AIRBORNE CONTAMINANTS (I)

•

Purpose

–

qualitative

analysis • indicate

presence of

and

identity

of contaminants –

quantitative

analysis •

measure concentration

and

assess compliance

with standards

SAMPLING OF AIRBORNE CONTAMINANTS (II)

•

Types

–

“spot” or “grab” sample (stain tube)

• taken at a single point at a particular time in the general working atmosphere eg ozone monitoring –

time averaged sample (dust sampling)

• taken over a period of time, analysed, and averaged over that period (operators breathing zone) –

continuous monitoring (direct reading)

• continually measured and giving a continuous record of airborne contamination (can be used in conjunction with alarm systems eg toxic chemicals)

CONTROL PHILOSOPHY

Source

Elimination Substitution Enclosure Process change LEV

Transmission Receiver

Shielding Remove worker Distance Reduce exposure Dilution ventilation Enclose worker Reduce no of workers Personal protective equipment

VENTILATION

•

dilution ventilation

– dilutes contaminant to an acceptable level – comprises fans set in walls or roof – cheap and simple – limited application as a control strategy •

local exhaust ventilation

– captures contaminant close to point of generation – comprises hood, ductwork, filter, fan,outlet – good control of hazardous contaminants

DILUTION VENTILATION (I)

• changes the whole workplace air over a given time period ie air changes per hour • limit to circumstances where: – exposure limit is high – low evaporation rate for liquids – slow evolution for gases – operators not close to the point of generation – substance is quickly carried away from the operator

DILUTION VENTILATION (II)

• rate of contaminant generation governs air changes per hour required • density of contaminant governs position of fans: – density >1 (ie solvents) - low level fan in wall – density <1 (ie hot gases) - high level fan in roof • problems include: – “dead areas” where poor airflow allows contamination to build up – heat losses due to high rate of air change

LOCAL EXHAUST VENTILATION (I)

• Hood or exhaust inlet – receptor hood • contaminant directed into a large hood by fan assisted draught – captor hood • contaminant captured by air flow close to point of generation – low pressure large volume flow – high pressure low volume flow (high velocity)

LOCAL EXHAUST VENTILATION (II)

• ducting – straight with gentle bends and angled joints – sufficient air flow to prevent deposition of solids – access ports for cleaning and flow monitoring • filter or purifying system – cyclones, washers, electrostatic, bag filters

LOCAL EXHAUST VENTILATION (III)

• Fans – axial flow fan • airflow is parallel to the shaft of the impeller • compact and fits neatly into ductwork – centrifugal fan • air enters the impeller then is discharged at right angles • exhaust outlet – careful location to avoid: • cyclic pollution • effects of weather of air disturbance

BIOLOGICAL HAZARDS

• zoonoses – animal infections transmitted to persons in the course of their work • bacilli – infections such as Legionnaire’s or Weil’s disease • fungi – extrinsic allergic alveolitis • blood-borne infections – hepatitis B and AIDS

ZOONOSES

•

Brucellosis

(bacterium) – cattle, pigs •

Q Fever

(bacterium) – cows, sheep •

Orf

(virus) – sheep •

Psitticosis

(bacterium) – poultry, birds •

Anthrax

(bacterium) – farm animals •

Glanders

– horses, donkeys, mules

CONTROL STRATEGIES FOR ZOONOSES

• routes of entry – skin penetration • cuts, sores, abrasions • injection by bites • contact with conjunctiva of eye – inhalation • contaminated dust – ingestion • contamination via hands • control strategies – eliminate • immunisation • improve animal stock – enclosure • infected aerosols – ventilation • infected dusts from wool, skin, hides – hygiene • disinfection – personal protective equipment

LEGIONNAIRES’ DISEASE

• caused by inhalation of airborne droplets containing the legionella bacteria • pneumonia-type symptoms • manage the risk by: – identifying and assessing sources of exposure • contaminated sprays and aerosols – avoid conditions where legionella can proliferate (water temperature,stagnation, treatment) • persons at risk – susceptible persons ie hospital patients

WEIL’S DISEASE

• caused by infection from rats – type of bacteria (Leptospira icterohaemorrhagiae) – enters body through cuts/abrasions of skin • jaundice-type symptoms • manage the risk by: – identifying and assessing sources of exposure – destruction of rat infestation – immunisation, first aid, information, protective clothing • persons at risk – canal workers, sewer workers, abattoir workers

BLOOD-BORNE INFECTIONS

• hepatitis B (virus) – severe form of jaundice – infection through contact with blood or bodily fluids – persons at risk include health workers and emergency services – protect through preventing puncture wounds, disinfection and disposable gloves • AIDS (virus) – debility of immune system – infection through contact with blood or bodily fluids – persons at risk include health/social workers and emergency services – protect through preventing puncture wounds, disinfection and disposable gloves

SUBSTANCES HAZARDOUS TO HEALTH

• classified as dangerous to health under the current CHIP Regulations • assigned a MEL or OES • biological agent • dust in a substantial concentration • any other substance which creates a comparable health hazard

REQUIREMENTS OF COSHH

• assess the risks to health arising from exposure • prevent or adequately control exposure • ensure that control measures are used and properly maintained • monitor exposure and carry out appropriate health surveillance • ensure that employees are properly informed, trained and supervised

COSHH ASSESSMENT (I)

• which hazardous substances are present?

– brought into the workplace – dusts, fumes, leakages – finished products or wastes • who might be exposed?

– employees – contractors – public

COSHH ASSESSMENT (II)

• do they represent a significant risk?

– hazardous properties (toxic, corrosive, irritant) – quantity used and frequency of use – possible routes of exposure (inhalation, contact) – possibility of exposure exceeding OEL – possibility of leakage, spillage or release – cleaning and maintenance operations

PREVENTING EXPOSURE

• change the process or activity – the hazardous substance is not required or generated • replace the hazardous substance with a safer alternative • use the hazardous substance in a safer form

CONTROLLING EXPOSURE

• totally enclose the process • partially enclose the process and use local exhaust ventilation • use general ventilation • use systems of work and handling procedures that minimise spills and leaks • reduce the duration of exposure

MONITORING EXPOSURE HEALTH SURVEILLANCE

•

monitoring exposure

– where serious risks if controls fail – to confirm exposure limits are not exceeded – to confirm that controls are working properly – keep records •

health surveillance

– where exposure is linked to a disease which could occur and can be detected – where employees are working in a process listed in schedule 5 and exposure could be significant

•

RECORDING AND REVIEWING THE ASSESMENT

record

enough information: – to show how decisions on risks and precautions were made – to clearly show the responsibilities for implementing the precautions •

review

the assessment: – at no less than 5-yearly intervals – whenever it is thought that the assessment might not be valid – where there has been a significant change in the work

INFORMATION, INSTRUCTION AND TRAINING

• inform, instruct and train employees about: – the nature of the substances and the risks arising from exposure – the precautions that should be taken • give information and instruction on: – the purpose and use of control measures – use of personal protective equipment – results of any monitoring or health surveillance – emergency procedures

•

DISPOSAL OF HAZARDOUS SUBSTANCES (I)

Safe Storage

– segregate – control storage to prevent risks to employees and others – keep hazardous and non-hazardous waste separate – ensure correct labelling – keep quantities to a minimum – separate incompatible hazardous wastes

•

DISPOSAL OF HAZARDOUS SUBSTANCES (II)

Transport

– use correct type of vehicle – inspect load prior to transport to check: • description of material • containment • labelling • documentation – transfer waste only to an authorised person – transfer must be accompanied by written documentation: • identification • quantity • time and place of transfer • details of current and intended holder – special waste requires use of a consignment note