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Monitoring Occupational Environment

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Monitoring Occupational Environment

  1. 1. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat Occupational Health Courses Dr. Ahmed-Refat Professor of Occupational Medicine Tibah University, KSA, March ,2012 www.SlideShare.net/AhmedRefat 1- Assessment of Work Place Hazards: Measuring Tools and Principles Introduction: Occupational Hygiene:"The discipline of anticipating, recognizing,evaluating and controlling health hazards in theworking environment with the objective ofprotecting worker health and well-being andsafeguarding the community at large. 1
  2. 2. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefatComponents of Occupational Hygiene: — —ANTICIPATION – this involves identifying potential hazards in the workplace before they are introduced. — —RECOGNITION - this involves identifying the potential hazard. — —EVALUATION of the extent of exposure to hazards in the workplace. This often involves measurement of the personal exposure of a worker to the hazard in the workplace, and —assessment of the data in terms of recommended occupational exposure limits (OELs), where such criteria exist. Controlling health hazards in the working environment. 2
  3. 3. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat I- Measuring of Physical Hazards A- NoiseBasic Concepts :Sound is fluctuations in pressure above and below theambient pressure of a medium that has elasticity andviscosity. The medium may be a solid, liquid, or gas.Sound is the auditory sensation evoked by the oscillationsin pressure .Noise = unwanted sound, Sound perceived by the ear results from fluctuations ( Frequency – cycle per second - Hz ) the pressure ( Intensity- Power – Loudness –Energy – dB ) of the air. 3
  4. 4. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefatDecibel: The decibel ( dB) is a dimensionless quantity.Unit of Sound/ Noise intensity 4
  5. 5. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat dB weighting: • A-weighting’, or dB(A), is used to measure average noise levels as it approximates the sensitivity of the human ear at low noise levels. This is typically used to assess for the potential of hearing loss  ‘C-weighting’, or dB(C), is used to measure peak, impact or explosive noises. This weighting is used to determine suitable personal hearing protection equipment in high noise environments 3dB change in noise level results in a doubling of the noiseWorkplace Noise Levels 5
  6. 6. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat 6
  7. 7. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat B- LightBasic Concepts:Measuring of WorkplaceIlluminationLight meter / Lux meter). 7
  8. 8. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefatWhat is a light meter?A light meter measures the level (amount) of visible light(illumination) in a given area tested. Illumination is expressed in units of lumens per square meter LUX (metric) and lumens per square ft. Foot candles/ Fc (English).Convert Foot candles, LUX, and Lumens: • Multiply Foot candles by 10.76891 to convert to LUX • Multiply LUX by 0.09290304 to convert to Foot candles • Foot candles = Lumens per sq. ft. Sun = 107,527 Lux Full day light = 10,752 Lux Full moon = 108 LuxWork place Adequate Light ( office ):• General background 160–240 Lux• Routine office work (typing, filing) 400 Lux• Work with poor contrast (proof reading) 600 Lux. 8
  9. 9. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat Minimum Illumination Intensity on Objects of Work 9
  10. 10. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat C- HeatBasic Concepts: HEAT STRESS “The net heat load to which a worker may be exposed from the combined contributions of metabolic cost of work, environmentalfactors (ie air temperature, humidity, air movement and radiant heat exchange) and clothing requirements.” HEAT STRAIN “The physiological impact of heat stress on the body, as expressed in terms of changes in tissue temperatures andcompensatory changes in the activity of physiological systems (sweat rate, heart rate, skin blood flow).” Heat strain =“The overall physiological response resulting from heat stress.” 11
  11. 11. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefatTemperature Levels and its effects46.5°C Highest recorded survivable core temperature43°C Tissue damage (brain, liver)41°C Cessation of sweating39°C The threshold of hyperthermia36.8°C Normal core temperature35°C The threshold of hypothermia33°C Impaired muscle function, introversion, loss of mentalalertness30°C Cessation of shivering and then unconsciousness28°C Possible ventricular fibrillation26°C Bradycardia and bradypnoea24°C Possible death without rewarming14.4°C Lowest recorded core temperature for a survivor of accidentalhypothermia 11
  12. 12. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefatDamaging Effects of Heat Exposure>50°C Second-degree burn>45°C Tissue damage41 – 43°C Burning pain39 – 41°C Pain33 – 39°C Skin warmth through to discomfort (hot)28 – 33°C Thermal comfort25 – 28°C Cool through to discomfort (cold)15°C Pain10°C Loss of skin sensation5°C Non-freezing cold injury: (time dependent, and can occurbetween 17 – 0.55°C)<0.55°C Freezing cold injury (frostbite) 12
  13. 13. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat Measuring of Thermal Environment Measurement of air temperature is usually made with one of the following techniques:  Mercury-in-glass thermometer  Thermocouple  Platinum resistance thermometer  ThermistorA- Mean Radiant TemperatureMeasurement of the mean radianttemperature can be derived fromthe readings of a black globethermometer. This consists ofa hollow black globe usually madeof copper (due to its highconductivity) in the centre ofwhich is placed a temperaturesensor . 13
  14. 14. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefatB- Humidity • Air contains a certain amount of water vapour • Higher air temperature – more water vapour can be contained in the air • Lower air temperature – less water vapour can be contained in the airThe absolute humidity is defined as the mass of water vapour in airper unit volume of air/water vapour mixture and has units of kg m-3.Relative humidity is defined as:“The ratio of the prevailing partial pressure of water vapour to thesaturated water vapour pressure.”The “dew point” is the temperature at which the air becomessaturated.Dry & wet Bulb Thermometer • Water evaporating from a surface reduces the temperature of the surface • If the bulb of a thermometer is covered by a damp fabric sleeve water evaporating causes a lower reading - this is termed the wet bulb temperature • The difference between dry bulb temperature and wet bulb temperature can be used to determine relative humidity 14
  15. 15. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat • At 100% relative humidity no evaporation takes place so the dry bulb temperature and wet bulb temperature will be the sameMeasuring relative Humidity • One of the most commonly used instruments for determining humidity is the whirling hygrometer, which is also called a sling psychrometer (Figure 5.2).Whirling hygrometer  one dry bulb thermometer  one wet bulb thermometer - bulb covered with wick dipped into distilled water reservoir  air flow (> 4 metres / sec) achieved by ‘whirling’  read wet bulb temperature first, then dry bulb Its operation is relatively simple. The sling psychrometer consists of two thermometers, a wet bulb and dry bulb. A “wick” or “sock” covers one of the thermometers (the “wet” bulb) and should be thoroughly wettedusing distilled (de-ionised) water prior to taking any measurements. Thisinvolves filling the water reservoir at the end of the psychrometer and may 15
  16. 16. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat also involve manually wetting the wick. Care should be taken not to contaminate the wick with dirty fingers or water that is not de-ionised.The handle is then unclipped and the psychrometer is swung for at least 20 – 30 seconds. This will allow an air movement to pass over the wet bulb thermometer and initiate evaporation of water from the wick. After 20 – 30 seconds, the aspirated wet bulb temperature is read first (then the dry bulb temperature). These values are noted and the measurements repeated three times. Optimally, the repeated measurements should be within ±1°C of CalculationPsychrometric charts – Charts that inter-relate – vapour pressure (water content) – relative humidity – dry bulb temperature – wet bulb temperature 16
  17. 17. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefatMeasurement of Air VelocityAir movement across the body can influence heat flow to and from the bodyand hence body temperatureAir velocity can be measured by a number of methods • Vane anemometer – Directional & not accurate at low velocities • Hot-wire anemometer – Directional & inaccurate at low velocities • Kata thermometer – Omni-directional but not suited to conditions where large or rapid variations in air movement occur 17
  18. 18. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat Vane anemometerHot-wire Anemometer 18
  19. 19. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefatKata Thermometer • Principle of operation – thermometer with large bulb – two marks on stem (3K apart) – heated so that fluid is above higher mark – fixed in monitoring position – allowed to cool – time for fluid to cool to lower mark noted 19
  20. 20. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat Wet Bulb Globe Thermometer 21
  21. 21. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat Wet Bulb Globe Thermometer Calculation of WBGT 21
  22. 22. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat 22
  23. 23. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat II- Chemical Hazards Physical States of chemicals • • Vapour - the gaseous state of a substance which is liquid at 25°C and 760 mm Hg (STP). • Mist - liquid particles, large size generally produced by bubbling, splashing or boiling of a liquid. • Fume - Solid particles produced by condensation from a liquid or a reaction between two gases. The particle size of a fume <1 micron (µm) diameter anything larger is considered a dust particle. • 23
  24. 24. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat • Dust - particles of solid material in the broad size range of 1 micron to 1 millimetre diameter. Anything of a larger particle size is considered to be grit and will be too heavy to remain airborne. • Aerosol - general term for the dispersions of solid or liquid particles of microscopic size in a gaseous medium e.g. fog, smoke etc. although commonly used to term fine liquid spray (e.g. ‘aerosol can’).Fibre – Solid particulate which are long and thin i.e. have a high aspect ratio of length to breadth. Types of Sampling • Grab • Short term • Long term • Continuous Sampling Pattern • Grab sampling • Task duration sampling • Short period sampling (less than the task duration and sometimes taken consecutively) • Full shift sampling • 24
  25. 25. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefatGrabConcentration TimeShort TermConcentration Time 25
  26. 26. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefatLong TermConcentration TimeContinuousConcentration Time 26
  27. 27. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat Sampling for Particulates/Dust Particle Size Distribution 27
  28. 28. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat Particle sizeTotal inhalable dust is the fraction of airbornematerial which enters the nose and mouth duringbreathing and is therefore liable to depositionanywhere in the respiratory tract. The particle sizesof total inhalable dust are up to 100 microns.Respirable dust is that fraction that penetrates to thedeep lung where gas exchange takes place. Theparticle sizes of respirable dust are up to 10 micronsBreathing ZoneAs the main route of entry into the body for many substances isvia inhalation, it is logical that any estimate of exposure of such substances should be conducted in a location consistent withnormal inhalation patterns of workers. By convention, this has been deemed the “breathing zone” .“A hemisphere of 300 mm radius extending in front of the face and measured from the midpoint of a line joining the ears.” 28
  29. 29. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat Elements of a Sampling System 29
  30. 30. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat 31
  31. 31. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat Sampling for Gases and Vapours • Active Sampling - i.e. by means of a mechanic/sampling pump method. – Sorbent Tubes • Passive Sampling 31
  32. 32. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat 32
  33. 33. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat 33
  34. 34. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat Indicator Tubes (Gas Grab Sampling) Before ( Left) and after sampling (Right) 34
  35. 35. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat 35
  36. 36. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat HYGIENE STANDARDS By “hygiene standard” we are referring to the level ofexposure, via inhalation, that should not cause ill health to a healthy adult when exposed to a contaminant. The results from air sampling can thus be compared against these standards and can be used as a guide to assist in the control of health hazards. Other names for hygiene standards commonly used throughout the world areThreshold Limit Values (TLVs®), Exposure Standards (ES),Occupational Exposure Limits (OEL), Workplace Exposure Limits (WEL). In general all such terminology is interchangeable. The best known list of “hygiene standards” is the Threshold Limit Values (TLVs®) produced by the American Conference of Governmental Industrial HygienistsThreshold Limit Values (TLVs®) refer to airborne concentrations of chemical substances and represent conditions under which it is believed that nearly all workers may be repeatedly exposed, dayafter day, over a working lifetime, without adverse health effects. 36
  37. 37. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat There are three types of TLVs®1. TLV-Time Weighted Average (TLV-TWA)2. TLV-Short Term Exposure Limit (TLV-STEL)3. TLV-Ceiling (TLV-C)4.3.1 TLV-TWA “The TWA concentration for a conventional 8-hour workday and a 40-hour work week, to which it is believed that nearly all workers may be repeatedly exposed, day after day, for a working lifetime without adverse effect.”TLV-STEL “A 15 minute TWA exposure that should not be exceeded atany time during a workday, even if the TWA is within TLV-TWA. The TLV-STEL is the concentration to which it is believed thatworkers can be exposed continuously for a short period without suffering from:1. irritation2. chronic or irreversible tissue damage3. dose-rate dependent toxic effects, or4. narcosis of sufficient degree to increase the likelihood ofaccidental injury, impaired self rescue, or materially reducedwork efficiency.”TLV-C “The concentration that should not be exceeded during any part of the working exposure.If instantaneous measurements are not available, sampling should be conducted for the minimum period of time sufficient to detect exposures at or above the ceiling value.” 37
  38. 38. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat 38
  39. 39. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefat Mixtures When two or more hazardous substances have a similar toxicological effect on the same target organ or system, theircombined effect rather than that of either individually, should be given primary consideration. In the absence of information to the contrary, differentsubstances should be considered as additive where the health effect and target organ or systems is the same ie: C1/TLV1 + C2/TLV2 + …… + Cn/TLVn ≤ 1 39
  40. 40. {{{ Occupational Health Training Courses }}} www. Slideshare.net/AhmedRefatConversion of PPM to mg/m3 41

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