NEBOSH NATIONAL GENERAL CERTIFICATE

1
NEBOSH NATIONAL GENERAL CERTIFICATE

• Occupational health hazards

2
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

3
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

4
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

5
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?

6
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

7
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

8
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

9
BIOLOGICAL HAZARDS

• exposure to biological agents resulting in
  illness
• types of biological agent include
• bacteria
• viruses
• fungi

10
PHYSICAL HAZARDS

• harmful energy absorbed by the bodys structure
• energy derived from
• mechanical sources
• noise, vibration
• radiation sources
• ionising, non-ionising
• thermal sources

11
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

12
MEASUREMENT

• continuously
• control strategy where the risk is high
• intermittently
• initial determination of hazard
• spot measurement in an established process
• routine check measurement

13
EVALUATION

• harmful characteristics of the substance, energy
  or condition involved
• concentration, intensity or level of the exposure
  to the harmful agent
• time duration of the exposure

14
CONTROL

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

15
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)

16
ROUTES OF ENTRY

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

17
PROCESS OF ENTRY

• absorption
• epidermis
• lungs
• gastro-intestinal tract
• direct entry into the body

18
TOXICOLOGY- the study of poisonous materials and
their effects on living organisms

• 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)

• 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

19
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

20
DEFENCE MECHANISMS OF THE BODY

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

21
CHIP 2

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

22
HEALTH EFFECTS CLASSIFICATION OF HAZARDOUS
SUBSTANCES

• very toxic
• toxic
• harmful
• corrosive
• irritant

• sensitising
• carcinogenic
• mutagenic
• toxic for reproduction

23
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
  

24
LABELLING

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

25
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

26
CATEGORIES OF CHEMICAL AGENT

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

27
FORMS OF CHEMICAL AGENT

• solids
• liquids
• dusts
• fibres

• mists
• gases
• fumes
• vapours

28
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

29
TOXIC AGENTS

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

30
COMMONLY OCCURRING TOXIC SUBSTANCES

• lead
• mercury
• benzene
• phenol

• trichloroethylene
• silaceous dust
• asbestos
• carbon monoxide

31
CORROSIVE AGENTS

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

32
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

33
SENSITISERS

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

34
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 (milligrams of substance per cubic metre of
  air)
• expressed as the concentration of an airborne
  substance averaged over a reference period
• 15 minutes short term limit
• 8 hours long term limit

35
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

36
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

37
SAMPLING OF AIRBORNE CONTAMINANTS (I)

• Purpose
• qualitative analysis
• indicate presence of and identity of contaminants
• quantitative analysis
• measure concentration and assess compliance with
  standards

38
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)

39
CONTROL PHILOSOPHY
40
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

41
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

42
DILUTION VENTILATION (II)

• rate of contaminant generation governs air
  changes per hour required
• density of contaminant governs position of fans
• density gt1 (ie solvents) - low level fan in wall
• density lt1 (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

43
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)

44
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

45
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

46
BIOLOGICAL HAZARDS

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

47
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

48
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

49
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

50
WEILS 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

51
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

52
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

53
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

54
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

55
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

56
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

57
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

58
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

59
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

60
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

61
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

62
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