Occupational Health Hazards: General Concepts and Recognition Methods

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 body’s 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. 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) TOXICOLOGY- the study of poisonous materials and their effects on living organisms

19. 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 LOCAL AND SYSTEMIC EFFECTS

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. very toxic toxic harmful corrosive irritant sensitising carcinogenic mutagenic toxic for reproduction HEALTH EFFECTS CLASSIFICATION OF HAZARDOUS SUBSTANCES

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

26. CATEGORIES OF CHEMICAL AGENT • toxic, including carcinogenic • corrosive and irritant • dermatitic and sensitising

27. solids liquids dusts fibres mists gases fumes vapours FORMS OF CHEMICAL AGENT

28. 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 TYPES OF TOXIC EFFECT

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

30. lead mercury benzene phenol trichloroethylene silaceous dust asbestos carbon monoxide COMMONLY OCCURRING TOXIC SUBSTANCES

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. 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 (II)

36. 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 OCCUPATIONAL EXPOSURE LIMITS (III)

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. 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 VENTILATION

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 >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

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 Legionnaire’s or Weil’s disease • fungi • extrinsic allergic alveolitis • blood-borne infections • hepatitis B and AIDS

47. Brucellosis (bacterium) cattle, pigs Q Fever (bacterium) cows, sheep Orf (virus) sheep Psitticosis (bacterium) poultry, birds Anthrax (bacterium) farm animals Glanders horses, donkeys, mules ZOONOSES

48. 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 CONTROL STRATEGIES FOR ZOONOSES

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. 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