MAK maximum allowable concentration of a substance (Germany) MAPP major accident prevention policy MASTA Medical Advisory Service for Travelers Abroad MbOCA dichloro-4,4-methylene dianiline MCA Maritime and Coastguard Agency MDA 4,4-diaminodiphenylmethane MDHS methods for the determination of hazardous substances MDI methylenebis (phenyl isocyanate) MDR-TB multidrug-resistant tuberculosis ME myalgic encephalomyelitis MEDIF medical information form ( \201 tness to \202 y) VII_Smedley_symb01.indd xxii 1/2/2013 1:23:48 PM SYMBOLS AND ABBREVIATIONS xxiii MEK methyl ethyl ketone MHOR Manual Handling Operations Regulations MHRA Medicines and Healthcare Products Regulatory Agency MHSWR Management of Health and Safety at Work Regulations MI myocardial infarction M/I manufacturers and importers MIG metal inert gas (welding) MMA manual metal arc (welding) MMMF machine-made mineral \201 bre MMR measles, mumps, rubella vaccine MMSE Mini Mental State Examination MOD Ministry of Defense (UK) MOSS Musculoskeletal Occupational Surveillance Scheme MP Member of Parliament mp melting point MPE maximum permissible exposure value (of lasers) MPTP 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine MRI magnetic resonance imaging MRO Medical Review Of \201 cer (of drug test results) MRSA multiresistant Staphylococcus aureus MS member states of EU MSD musculoskeletal disorder MSDS Manufacturer \200\231s Safety Data Sheet MSLA minimum school-leaving age mSv millisieverts MUC maximum use concentration (of respirators) Muta. mutagen MWF metal-working \202 uid NaCN sodium cyanide NCGC National Clinical Guideline Center (UK) NEBOSH National Examination Board in Occupational Safety and Health NEQAS UK National External Quality Assessment Service NHS National Health Service (UK) NI National Insurance (UK) NIBSC National Institute for Biological Standards and Controls NICE National Institute for Health and Clinical Excellence (UK) NIHL noise-induced hearing loss VII_Smedley_symb01.indd xxiii 1/2/2013 1:23:48 PM SYMBOLS AND ABBREVIATIONS xxiv NIOSH National Institute for Occupational Safety and Health (USA) nm nanometer NMC Nursing and Midwifery Council NOx oxides of nitrogen NOAEL no observable adverse effect level NPIS National Poisons Information Service NRL natural rubber latex NRPB National Radiological Protection Board NRT nicotine replacement therapy NRTIs nucleoside analog reverse transcriptase inhibitors NSI needle stick injury NTE neuropathy target esterase OA occupational asthma OA osteoarthritis OASYS computer based analytical tool of serial measurements of peak expiratory \202 ow OC organochlorine OCD obsessive compulsive disorder OCP oral contraceptive pill OD occupational dermatitis ODTS organic dust toxic syndrome OEL occupational exposure limit OH occupational health OHA occupational health adviser \200\224an occupational health nurse OHN occupational health nurse OHP occupational health physician OHS occupational health service ONS Of \201 ce for National Statistics (UK) OP organophosphate OPCS Of \201 ce of Population Censuses and Surveys OPIDN organophosphate-induced delayed neuropathy OPRA Occupational Physicians Reporting Activity OSHA Occupational Safety and Health Administration (USA) OSSA Occupational Surveillance Scheme for Audiological Physicians OSHCR Occupational Safety and Health Consultants Register Pa pascal (SI unit of pressure) PAP 3-(N-phenylamino)-1,2-propanediol VII_Smedley_symb01.indd xxiv 1/2/2013 1:23:49 PM SYMBOLS AND ABBREVIATIONS xxv PAHs polycylic aromatic hydrocarbons PBG porphobilinogen PBT persistent bioaccumulative and toxic (REACH) PC personal computer PCBs polychlorinated biphenyls PCDF polychlorinated dibenzofuran PCR polymerase chain reaction PCV passenger-carrying vehicle PD Parkinson \200\231s disease PDA personal digital assistant \200\224a palmtop computer pdf portable document format PEF peak expiratory \202 ow PEP post-exposure prophylaxis for blood-borne virus exposures PGD patient group direction (for vaccine administration) PHLS Public Health Laboratory Service (UK) PHQ9 Patient Health Questionnaire PI protease inhibitor PM2.5 particulate matter <2.5 m in diameter PM10 particulate matter <10 m in diameter PMF progressive massive \201 brosis PMV predicted mean vote PPC pollution prevention and control PPD predicted percentage of persons dissatis \201 ed with the thermal environment PPE personal protective equipment ppm parts per million PTFE polytetra \202 uoroethylene PTO power take-off PTSD post-traumatic stress disorder PULHHEEMS UK military grading scheme: Physique, Upper and Lower limbs, Hearing, Eyesight, Mental func tion, Stability PUWER Provision and Use of Work Equipment Regulations Pv velocity pressure (of ventilation systems) PVA polyvinyl alcohol PVC polyvinyl chloride QEC Quick Exposure Check tool RAST radio-allergosorbent test VII_Smedley_symb01.indd xxv 1/2/2013 1:23:49 PM SYMBOLS AND ABBREVIATIONS xxvi RBP retinol binding protein RCN Royal College of Nursing RCT randomized controlled trial REACH Registration, Evaluation, Authorization and Restriction of Chemicals Repr reproductive toxin RF radiofrequency radiation RIDDOR Reporting of Injuries, Diseases, and Dangerous Occurrence Regulations RMM risk management measures (REACH) RMO Review Medical Of \201 cer (of drug screen results) RMP registered medical practitioner rms root mean square RNA ribonucleic acid RO Responsible Of \201 cer (for revalidation of UK doctors) RPA radiation protection adviser RPE respiratory protective equipment RPS radiation protection supervisor RR relative risk RULA Rapid Upper Limb Assessment tool SaO 2 SARS oxygen saturation (%) severe acute respiratory syndrome SARs structure \200\223activity relationships (of toxicology) SBS sick building syndrome SCL skin contamination layer SD standard deviation SEA strategic environmental assessment Sen sensitizer (term used in HSE publication EH40) SEPA Scottish Environmental Protection Agency SEQOHS Safe effective quality occupational health service \200\224UK occupational health accredita tion scheme SI Le Syst me International d \200\231Unit s \200\224the metric system of measurements SIDAW Surveillance of Infectious Diseases at Work SIEF substance information exchange forum (REACH) SIGN Scottish Intercollegiate Guideline Network Sk substance can be absorbed through the skin (term used in HSE publication EH40) SLM Sound level meter VII_Smedley_symb01.indd xxvi 1/2/2013 1:23:49 PM SYMBOLS AND ABBREVIATIONS xxvii SMEs small- and medium-sized enterprises SMR standardized mortality ratio SN sensorineural \200\224of hand arm vibration syndrome grading SNR single rating number (of hearing protection) SOM Society of Occupational Medicine SOP standard operating procedure SOSMI Surveillance of Occupational Stress and Mental Illness SPRU Special Pathogens Reference Unit SSP statutory sick pay SSRI selective serotonin-reuptake inhibitor STEL short-term exposure limit STOT/SE speci \201 c target organ toxicity \200\224single exposure STOT/RE speci \201 c target organ toxicity \200\224repeated exposure Sv Sievert SVHC substance of very high concern (REACH) SWASH Survey of Workplace Absence Sickness and (Ill) Health -UK SWI Self-reported Work-related Illness survey SWORD Surveillance of Work-related and Occupational Respiratory Disease TB tuberculosis TDI toluene-2,4-diisocyanate TENS transcutaneous electrical nerve stimulation THOR The Health and Occupation Reporting network TIA transient ischaemic attack TIG tetanus immunoglobulin TIG tungsten inert gas (welding) TLD thermoluminescent dosemeter TLV threshold limit values TNT trinitrotoluene TOCP tri-orthocresylphosphate TOP termination of pregnancy TPT thermal (temperature) perception threshold Travax travel health information website \200\224run by Health Protection Scotland TSE transmissible spongiform encephalopathy TST tuberculin skin test TTS temporary threshold shift (of hearing thresholds) TURP trans-urethral resection of prostate VII_Smedley_symb01.indd xxvii 1/2/2013 1:23:49 PM SYMBOLS AND ABBREVIATIONS xxviii TWA time-weighted average Twc Wind Chill Index UKAP UK Advisory Panel for health care workers infected with blood-borne viruses UKAS UK Accreditation Service ULD upper limb disorder UV ultraviolet light UVA ultraviolet light A UVB ultraviolet light B UVC ultraviolet light C vCJD Variant Creutzfeldt \200\223Jakob disease VCM vinyl chloride monomer VDU visual display unit VHF viral haemorrhagic fever VO2max maximal oxygen consumption VOCs volatile organic compounds vPvB very persistent and very bioaccumulative (REACH) VPT vibrotactile perception threshold VWF vibration white \201 nger \200\224the vascular component of hand arm vibration syndrome WB wet bulb temperature WBGT wet bulb globe temperature WBV whole-body vibration WCA Work Capability Assessment \200\224of entitlement to Employment and Support Allowance in UK WEL workplace exposure limit WHASS Workplace Health and Safety Survey WHO World Health Organization WRULD work-related upper limb disorder XRD X-ray diffraction XRF X-ray \202 uorescence spectroscopy ZPP zinc protoporphyrin VII_Smedley_symb01.indd xxviii 1/2/2013 1:23:49 PM Section 1 Occupational hazards 1 Physical hazards 2 Chemical hazards 3 Biological hazards 4 Mechanical and ergonomics haza rds 5 Psychosocial hazards 3 41 103 117 133 01_Smedley_Chap01.indd 1 12/31/2012 8:42:03 PM This page intentionally left blank 3 Chapter 1 Physical hazards Noise 1: legal requirements, and risk assessment 4 Noise 2: instrumentation and determinati on of L EP , d 6 Vibration 1: whole-body vibration 8 Vibration 2: hand-transmitted vibratio n 10 Light and lighting 1: units, effects, and assessment 12 Light and lighting 2: assessme nt and surveys 14 Ionizing radiation 1: types, units and effects 16 Ionizing radiation 2: p rinciples of radiation protection 18 Ionizing radiation 3: instrumentation and measurement 20 Ionizing radiation 4: exposure control 22 Non-ionizing radiation 1: electromagnetic \201 elds 24 Non-ionizing radiation 2: optical radiation 26 Non-ionizing radiation 3: laser s 28 The thermal environment 1: thermal balance and instrumentation 30 The thermal environment 2: assessment of the thermal environment 34 The thermal environment 3: assessment of cold workplaces 36 The thermal environment 4: thermal comfort 38 01_Smedley_Chap01.indd 3 12/31/2012 8:42:03 PM CHAPTER 1 Physical hazards 4 Noise1: Legal requirements and risk assessment De \201 nitions \200 Peak sound pressure level ( L Cpeak ): maximum value of the C-weighting sound pressure in pascals (Pa) to which a person is exposed during the working day Daily personal exposure level ( L EP,d ): daily equivalent A-weighted sound level, expressed in dB (A). L Aeq : continuous equivalent A-weighted sound pressure level. \200 dB (A) and dB (C ) we ighting: the human ear is more sensitive to certain frequencies than to others. Allowance f or this can be made in the electronic circuitry of the sound meter. Certain frequencies can be suppressed and others boosted. This technique is called weighting. The most commonly us ed weighting is the A weighting because it mimics the response of the human ear. The C weig hting should be applied when measuring the peak sound pressure level. Control of noise at work regulations and exposure limits The legal requirements are covered in the Control of Noise at Work Regulations 2005 (CNAWRs; see Box 1.1). The exposure actio n values (EAVs) are the noise exposure levels at which certain actions are required. These actions relate to need for risk assessment, controlling exposure, health surveillance, and the provision of information and training. The exposure limit values (ELVs) are the levels of noise above which employ- ees may not be exposed. The EAVs and ELVs are listed in Table 1.1. Box 1.1 The general duties under CNAWRs \200 A formal risk assessment at or above the low er EAV \200 If exposure cannot be reduced by other means, and is likely to above the upper EAV, then ear protection must be provided by the employer and used by emplo yees Health surveillance is required if the risk assessment indicates that there is a risk to he alth from noise (those regularly exposed above the upper EAV) without taking account of noi se reduction from use of hearing protectors Information, instruction, and training must be provided for those exposed at or the lower EAV. Table 1.1 Noise exposure limits and action values Exposure limit type Daily or weekly personal noise exposure dB (A) Peak sound pressure dB (C) Lower EAV 80 135 Upper EAV 85 137 ELV 87 140 01_Smedley_Chap01.indd 4 12/31/2012 8:42:04 PM NOISE1 5 Risk assessment and management Risk assessment \200 Systematically identify all noise sources \200 Identify individual s exposed to noise \200 For those exposed to noise determine daily exposure pattern and exposure duration Identify measure used to reduce exposure including protection afforded by ear defenders Estimate likely exposure (daily and peak) to noise and compare with limit and action values. Risk management \200 Eliminate/reduce noise exposure where practical \200 Provide healt h surveillance (audiometry) for those at risk \200 Give employees information and trainin g on safe work practices and hearing protection Maintain noise control equipment and hearing protection \200 Record \201 ndings and act ion plan \200 Review the following; actual work practices, exposure assessments, health surveillance data, \201 nding from workplace inspections, individual complaints re lated to noise exposure and new ways to reduce risk. 01_Smedley_Chap01.indd 5 12/31/2012 8:42:04 PM CHAPTER 1 Physical hazards 6 Noise 2: Instrumentation and determination of L EP , d Instrument types Sound level meter ( SLM) \200 Hand held portable instruments with data integrating facility \200 Quality (I nstrument class) governed by European Standards BS EN 61672 \200\2231:2003 Use windshield to protect microphone against air movement and dirt \200 Indicates the fol lowing; L eq over the measurement period; L Cpeak and the frequency content of noise (octave band analysis). Dosimeter (personal sound level meter) \200 Easily carried around by operator (Fig. 1.1). Should be placed at least 15cm from the head (avoid re \202 ected sound) and on the side of head where noise levels are higher In addition to data from SLM, dosimeters can indicate L EP , d or noise dose expressed as a percentage e.g. 200% dose May have data logging facility, enabling the visualization, storage and retrieval of record showing change in sound level with time (work tasks) and data storage. SPL (Leq) Dose (Pa2h) Peak (Lcpeak) Fig. 1.1 Personal noise dosimeters. 01_Smedley_Chap01.indd 6 12/31/2012 8:42:04 PM NOISE 2 7 Calibrators \200 Must provide tight \201 t around microphone \200 Use to check the SL M before and after making measurements \200 SLM and calibration should be checked by manu facture at least annually. Methods for determining L EP , d Personal dosimeter \200 Use when the person is highly mo bile (e.g. maintenance workers) or where exposure \202 uctuates greatly Place microphone on operators shoulder and on the side of the head where the noise levels a re higher and monitor for the duration of shift. Monitoring tasks/job \200 Break the working day in to a number of discrete tasks/jobs and measure representative noise level for each task (L Aeq ) Record time spent conducting each task \200 The L Aeq for each task is combined with dura tion to determine L EP , d using either the ready reckoner or the electronic spreadsheet available on the HSE website (http://www.hse.gov.uk/noise). Relevant legislation \200 The Control of Noise at Work Regulations 2005 (HSE Books) \200 Supply of Machinery (Safety) Regulations 1992 (as amended in 1994) \200 Provision and U se of Work Equipment Regulations 1998 (amended 1999). Further information Health and Safety Executive (1995). Sound Solutions HSG 138 . HSE Books , Sudbury. 01_Smedley_Chap01.indd 7 12/31/2012 8:42:04 PM CHAPTER 1 Physical hazards 8 Vibration 1: Whole-body vibration Common sources Exposure to whole-body vibration (WBV) ari ses in workers who drive or ride-on vehicles. Many different vehicle types can give rise to exposure. In the UK, the most common sources are cars, vans, fork-lift trucks, lorries, tr actors, busses, loaders, trains, dumpers, and excavators. Other exposures arise from trains , armored vehicles, off-road vehicles and helicopters. Occupations and industries The commo nest occupations with exposure are: \200 Farm workers \200 Drivers of road goods vehicl es \200 Lift truck drivers. The commonest industries are: \200 Agriculture \200 Const ruction \200 Land transportation. Main factors affecting exposure \200 Intrinsic vibration of the vehicle (wear and tear, d esign) \200 Seating and vehicle suspension \200 Road surface \200 Road speed. Potential health effects The best recognized effects are on the lumbar spine \200\224non-sp eci \201 c low-back pain (LBP), sciatica, lumbar disc degeneration. A systematic review by NIOSH (1997) 1 described evidence on the association with LBP as \200\230strong \200\231 (15 of 19 studies positive), but there is less certainty about the dose-response relationsh ip. Other suggested effects include: neck pain and cervical disc degenera- tion; autonomic dist urbance; and disorders of balance and digestion. The evidence for these is much weaker. Mot ion sickness is well recognized, however. Risk assessment and monitoring The Health and Safety Executive (HSE) provides an exposure c alculator to facilitate the summation of partial doses from several vehicles (M http:// www .hse.gov.uk/vibration/wbv/wbv.xls). 1 NIOSH (1997). Musculoskeletal disorders and workplace factors. A critical review of epide mio- logic evidence for work-related musculoskeletal disorders of the neck, upper \200\223e xtremity and low back, Publication no. 97 \200\223141. NIOSH, Cinncinati. 01_Smedley_Chap01.indd 8 12/31/2012 8:42:04 PM VIBRATION 1: WHOLE-BODY VIBRATION 9 Exposure limits Two exposure limits are speci \201 ed in UK and European legislation: \200 An EAV A(8) of 0.5m/s 2 : this is the daily amount above which employers must act to control exposure ELV A(8) of 1.15m/s 2 : this is the maximum amount an employee may be exposed to on any giv en day. (HSE advises that the ELV should not be considered a target; rather, the aim should be to reduce exposure as low as reasonably possible.) Prevention and control HSE advises that drivers should: \200 Adjust their seating \200 Avoid rough, poor or uneven surfaces \200 Adjust the vehicle speed to suit road condition s. It also advises on several other measures, including: \200 Maintenance of vehicle susp ension \200 Maintenance of site roadways \200 Better choice of seating \200 Rest brea ks \200 Safer systems of work \200 Simple health monitoring. Relevant legislation Contr ol of Vibration at Work Regulations 2005. Further information and guidance HSE web links. Available at: M http://www.hse.gov.uk/vibra tion/wbv/index.htm Vibration calculator. Available at: M http://www.hse.gov.uk/vibration/wb v/calculator.htm 01_Smedley_Chap01.indd 9 12/31/2012 8:42:04 PM CHAPTER 1 Physical hazards 10 Vibration 2: Hand-transmitted vibration Common sources Exposure arises from many sources, i ncluding concrete breakers, chain- saws, hand-held grinders, metal polishers, power hammers and chisels, needle scalers, scabblers, powered sanders, hammer drills, and even powered l awnmowers and motorcycle handlebars. Occupations and industries Occupations where exposure is common include: \200 Construction workers \200 Metal-working and maintenance \201 tters \200 Welders \200 Foresters, shipbuilders \200 Foundry workers \200 Road work ers. The main industries are construction and heavy engineering. An estima- teed 1.2 millio n men in Britain have weekly exposures that may justify health surveillance. Main factors affecting exposure \200 Tools: intrinsic properties of the tool (e.g. size, weight, frequency characteristics, balance between reciprocating forces), age of tools, and their maintenance . \200 Material being worked \200 Type of action at the work interface (e.g. cutting, d rilling, grinding) \200 Operator technique (e.g. type and force of grip, orientation of t he hand-arm). Potential health effects \200 Best-recognized are 2 Raynaud \200\231s phenomenon (vibra tion-induced white \201 nger), sensorineural impairment in the digits and carpal tunnel syndrome Other effects to the hand and arm are described (see b p. 300, Hand-arm vibration syndrome) Workers who use noisy vibratory tools commonly suffer from noise-induced hearing loss, as w ell as local hand-arm symptoms. Risk assessment and monitoring Vibration magnitude is measured in terms of acceleration, av eraged (by the root \200\223mean square (rms) method). Frequency-weighted measurements (a h w ) are made in three axes relative to the tool handle, using mounted accelerometers, and v alues (in m/s 2 rms) are determined for each axis and summated. The procedure is de \201 n ed in ISO 5349, 1986 (see also ISO 8041 and BS 7482). Injury is assumed to relate to the total energy entering the hand, so the dose can be re-ex pressed in terms of the equivalent acceleration impart- ing the same energy over an 8-h per iod: A(8) = ahw \210\232 (t/T(8))m/s2 01_Smedley_Chap01.indd 10 12/31/2012 8:42:04 PM VIBRATION 2: HAND-TRANSMITTED VIBRATION 11 where A(8) = the 8-h energy equivalent acceleration, a hw = rms accelera- tion magnitude af ter frequency-weighting, t = duration of exposure in a day, and T 8 = 8h (in the same units as t ). Partial doses from >1 tool can be summed to an equivalent daily dose. In practice this requ ires an inventory of sources, data on vibration magni- tude from equipment handbooks or sup pliers \200\231 information sheets, and an estimate of hand-tool contact times \200 HSE p rovides an exposure ready-reckoner, to estimate A(8) from exposure time and vibration magnitude, 2 and an exposure calculator to facilitate the summa tion of doses from several tools. 3 Exposure limits Two exposure limits are speci \201 ed in UK and European legislation: \200 EAV A(8) of 2.5m/s 2 : the daily amount above which employers must act to control exp osure. Health surveillance is required for workers who are regularly exposed above the EAV. ELV A(8) of 5m/s 2 : the maximum amount an employee may be exposed to on any given day. Prevention and control A number of steps can mitigate the risk in exposed populations. Thes e may be broadly summarized as: \200 Avoidance (e.g. doing the job another way) \200 Su bstitution (of tool or material worked) \200 Interruption of the pathway (by isolation or vibration-damping) \200 Safer systems of work. Some options include: \200 Routine repl acement of worn out tool parts \200 Proper selection of tools for the task \200 The red esign of tools to avoid the need to grip high vibration parts, or to reduce grip force Rest breaks to limit exposure times. Another common approach involves screening for early h ealth effects and limiting further exposure in those with hand-arm vibration syndrome. Relevant legislation Control of Vibration at Work Regulations 2005. Further information and guidance HSE web links: M http://www.hse.gov.uk/vibration/hav/index .htm 1 http://www.hse.gov.uk/pubns/indg175.pdf 2 http://www.hse.gov.uk/vibration/hav/readyreckon er.htm 3 http://www.hse.gov.uk/vibration/hav/calculator.htm 01_Smedley_Chap01.indd 11 12/31/2012 8:42:04 PM CHAPTER 1 Physical hazards 12 Light and lighting 1: effects and illuminance levels Terms, de \201 nitions, and units \200 Luminous intensity is the term applied to the luminous \202 ux emitted per solid an gle and is measured in candela (Cd). The candela is one of the seven basic SI units. Illuminance (symbol E) is the term given to the amount of light falling on a surface divided by the area over which it is falling and is measured in lux (derivatio n: lumens/square meter). Luminance (symbol L) is the \202 ow of light in a given direction from a surface element, measured in Cd/m 2 . Lighting and health In striving for optimum lighting conditions it is essential to consider the intensity and color spectrum of the light sources used. Incorrect selec- tion may lead to adverse health and/or psychological effects. The selection of the appropriate illuminan ce for given visual tasks is vitally important. \200 Too much illuminance can lead to the onset of glare \200 Too little illuminance can put a strain on the eyes. In some cases t he latter causes the individual to adopt uncomfortable working postures which may lead to m usculoskeletal problems. Poor lighting increases risk of fatigue and accidents reduces productivity and increases wo rkers dissatisfaction, which may contribute to worker absenteeism. Speci \201 c health risks These include, but are not limited to: \200 Infrared and ultra violet (UV) radiation: tungsten halogen (desk top lamps) and other high powered lamps e.g. those used in broadcasting studios may emit high l evels of UV radiation and cause harm to skin and eyes. These lamps should be \201 tted wi th a safety shield or UV \201 lter. For lasers see b p. 26, Non-ionizing radiation 2. Las ers. \200 Blue light hazard (photo retinitis): this is photochemical damage from exposure to medium to intense strength visible radiation for more than 10s. Blue light hazard is de \201 ned as the potential for a photochemical-induced retinal injury from ra diation between 400 and 500nm. The damage is irreversible and can lead to blindness. Blue l ight hazard is particularly important when considering aphakic individuals. \200 Photoker atitis \200\224a tender eye condition typically following exposure of insuf \201 ciently protected eyes to the ultraviolet rays emitted by either natural or arti \201 cial sources e.g. welder \200\231s arc or some arti \201 cial light sources. Unwanted effects created by lamps and lighting \200 Glare occurs when one part of the vis ual \201 eld is much brighter than others. There are two major types of glare: \200 disability glare where the individual is disabled from carrying out a given visual task 01_Smedley_Chap01.indd 12 12/31/2012 8:42:04 PM LIGHT AND LIGHTING 1: EFFECTS AND ILLUMINANCE LEVELS 13 discomfort glare where the individual is not disabled from carrying out a given visual task, but where he/she will experience discomfort, which may be delayed in manifestation. Veiling re \202 ections is the term applied to the scenario where typically out of focus r e \202 ections of light sources are viewed on specular surfaces (typically display screen equipment). This throws a veil of light over the screen making reading of text either dif \201 cult or impossible. Veiling re \202 ections is a form of disability glare Flicker is effectively light modulations at frequencies detectable by the human visual syst em. This can lead to both discomfort and fatigue and may provoke seizures in photosensitive individuals if the \202 icker frequency is typical 5 \200\22330Hz Stroboscopic effects on rotating machines: this is the scenario where rotating elements of machinery appear to be stationary or moving in a different manner (pos sibly in the reverse direction). It is caused by a combination of the rate of oscillations in light output illuminating the rotating element and the rate at which the human visual sy stem can detect movement. Recommended illuminance values \200 The Illuminance requirements of a task depend on perf ormance factors such as level of detail, speed, and accuracy. The Chartered Institute of Bu ilding Service Engineers (CIBSE) provides a comprehensive schedule of recommended illuminan ce values for different workplaces. 1 \200 Examples of recommended average illuminance va lues for work requiring: \200 limited perception of detail (e.g. factories assembling large components, kitchen) \200\224300 lux to 500 lux perception of detail (e.g. of \201 ces, metalworking plant) \200\224500 to 750 lux \200 \201 ne detail (e.g. electronic plants) \200\2241000 to 1500 lux. publication Lighting at work . 2 Guidance on minimum acceptable levels of lighting is given in the HSE 1 CIBSE (2009). http://www.cibse.org/ 2 HSE (2002). Lighting at work . HSE, Sudbury. Availa ble at: M http://www.hse.gov.uk/pubns/books/ hsg38.htm 01_Smedley_Chap01.indd 13 12/31/2012 8:42:05 PM CHAPTER 1 Physical hazards 14 Light and lighting 2: Assessment and surveys Assessing lighting in the workplace Workplace lighting should meet the following criteria: \200 Provides suitable and suf \201 cient i lluminance on the work piece \200 Provides suitable and suf \201 cient discrimination on the surface colors of objects in the working area Prevents the onset of glare (e.g. disability glare) \200 Avoids \202 icker and/or strob oscopic effects \200 Avoids the effects of veiling re \202 ections \200 Provides suf \201 cient contrast between work piece and background \200 Prevents excessive variation i n illuminance and luminance within the vicinity of the working areas. Optimally, the ratio of luminance values (task: near surround: far surround) should be 10:3:1. Takes into account the requirements of workers with disabilities \200 Is located so that access to luminaires (formerly light \201 ttings) and other lighting equipment does not p ose a risk to maintenance personnel Incorporates appropriate emergency lighting. Lighting surveys \200 It is desirable to have scale drawings of the interior to be survey ed. Alternatively draw a sketch plan of room showing position of work surfaces, windows and luminaires. Record: visual tasks carried out \200 whether luminaires and windows are clean \200 any luminai res which are damaged or missing \200 whether luminaires or windows cause discomfort or d isability glare \200 any \202 icker from discharge lamps Photographs showing areas of particular contention can be extremely useful The principle measurements of interest when undertaking a lighting survey are illuminance and luminance. Measuring equipment has to be color corrected (to com pensate for spectral variation) and cosine corrected Take illuminance reading at all work stations on every work surface \200 During measureme nts normal workplace lighting should be switched on and natural lighting should be excluded, where possible Measurements should be taken 0.80m above \202 oor level. \200 The minimum number of mea surements can be derived by calculating the room index k k = L \227 W / Hm \227 (L + W) where L is the room length, W is the room width, Hm is the height of lamps above working su rface. For values of k < 1, 1 \200\2232, 2 \200\2233, and >3, the minimum number of measure ments are 9, 16, 25, and 36, respectively 01_Smedley_Chap01.indd 14 12/31/2012 8:42:05 PM LIGHT AND LIGHTING 2: ASSESSMENT AND SURVEYS 15 Average illuminance is calculated by adding all measurements and dividing by the number of measurements and compared with the CIBSE guidance values Comprehensive details of required illuminance values in given locations are provided in CIBSE Code for Lighting. Further information BS EN 12464 \200\2231 (2011). Light and lighting \200\224lighting of wo rk places. Part 1: indoor work places. Available at: M http://shop.bsigroup.com/ BS EN 12464 \200\2232 (2007). Light and lighting \200\224lighting of work places. Part 1: o utdoor work places. Available at: M http://shop.bsigroup.com/ BS 5266 \200\2231 (2005). Emergency lighting regulations. Available at: M http://shop.bsigr oup.com/ CIBSE (2009). Code for Lighting . CISE. London. Available at: M http://www.cibse.o rg/ Health and Safety (Display Screen Equipment) Regulations (1992). Available at: M http:/ /www.hse. gov.uk/pubns/priced/l26.pdf HSE (2002). Lighting at work , HSG38. HSE Books, Sudbury. Available at: M http://www.hse.go v.uk/ pubns/books/hsg38.htm Smith NA (2000). Lighting for Health and Safety . Butterworth-Heinemann, Oxford. 01_Smedley_Chap01.indd 15 12/31/2012 8:42:05 PM CHAPTER 1 Physical hazards 16 Ionizing radiation 1: Types, units, and effects Routes and sources of exposure \200 The h azard from ionizing radiation can arise from: the uniform irradiation of the whole body or part of the body (external radiation) irradiation due to inhaled or absorbed radioactive material, which may concentrate in organs and tissues (internal radiation). \200 Natural (background) rad iation arises from several sources, including radiation from materials in the earth \200 \231s crust (e.g. radon in granite strata), cosmic radiation, food, radioactive aerosols, a nd gasses in the atmosphere. The largest dose of radiation, approximately 85% of the total, received by a person living in the UK is due to natural background radiation. Typically, t his can amount to 2.2mSv per year (see b p. 16, Units of ionizing radiation). Sources of ionizing radiation \200 Sealed : contained or shielded, and present only an ex ternal radiation hazard Unsealed : can be released into the atmosphere because they: are powders, liquids or gasses; \200 can contaminate surfaces and be taken into the body by ingestion, inhalation or via the skin, thereby giving rise to an internal radiation hazard, which can be present for variable periods of time. Types of ionizing radiation \200 Alpha particles: these are positively charged particles consisting of two protons and two neutrons (the same as a helium atom nucleus) with relativ ely little energy (they cannot pass through a sheet of paper or intact skin), but capable o f causing signi \201 cant damage to tissue over a short range. Beta particles: these are electrons and are also charged (negatively). They are much lighter than alpha particles and can pass through paper and skin, although th ey can be stopped by materials such as glass or thin layers of metal. Neutrons: these are uncharged particles with intermediate mass and variable energy. Gamma and X-rays: these are uncharged and without mass. They therefore cause less damage to tissue, but can pass through many materials, although are attenuated by thick layers of le ad or concrete. Units of ionizing radiation Activity This indicates the rate of transformations in radioact ive material. The unit is the becquerel (Bq). 1 Bq = 1 transformation/s 01_Smedley_Chap01.indd 16 12/31/2012 8:42:05 PM IONIZING RADIATION 1: TYPES, UNITS, AND EFFECTS 17 Absorbed dose This is the measure of energy deposition in any irradiated material by all ty pes of ionizing radiation, and is expressed as the energy absorbed per unit mass of materia l. The unit of absorbed dose is the gray (Gy): 1Gy = 1J/kg of energy deposition. Dose equivalent In biological systems, the same absorbed dose of different types of radia- tion produces different degrees of biological damage. To take account of this, the absorbed dose of each type of radiation is multiplied by a Q (or weighting) factor, which re \202 ects the relative ability of the particular type of radiation to cause damage. The unit of dose equivalent is the sievert (Sv), which is related to the gray as follows: dose equivalent (Sv) = absorbed dose (Gy) \227 Q. (Occupational doses of radiation are quoted in millisieverts (mSv) in view of the levels of radiation received.) For beta particles, gamma and X-rays, Q = 1. For (cid:2) particles, Q = 20. For neutrons, on average, Q = 10. Effective dose Similarly, the risk to various tissues varies from one tissue to another; it is not the same for any given equivalent dose. There is thus a weighting fac- tor for each tissue, when multiplied by the equivalent dose, the sum of all such calculations for the v arious tissues is referred to as the effective dose and is a single measure of the risk of detriment to health. Health effects \200 Damage to tissue sustained by an irradiated indi vidual is termed \200\230somatic \200\231 effects . These can be acute or delayed. That passed on to descen dants is the hereditary effect. Stochastic effects are those for which risk (the probability of the effect) increases progr essively with dose received, but there is no detectable threshold (e.g. induction of carcin ogenesis). The risk of developing cancer for radiation workers is calculated as 4% per Sv. Deterministic effects are those for which the severity of the effect increases progressively with dose and will not occur until a certain threshold of dose has been received (e.g. radiation burn). 01_Smedley_Chap01.indd 17 12/31/2012 8:42:05 PM CHAPTER 1 Physical hazards 18 Ionizing radiation 2: Principles of radiation protection Justi \201 cation The use of sour ces of ionizing radiation or radioactive materials must be justi \201 ed in terms of risk and bene \201 t. Optimization Work with sources of ionizing radiation must be such as to r educe risks to levels that are as low as reasonably achievable (in practice, \200\230achie vable \200\231 becomes \200\230practicable \200\231). Dose limits \200 Dose limits are r ecommended by the International Commission on Radiation Protection (ICRP), with the aim of preventing non-stochastic (deterministic) effe cts and limiting stochastic effects. \200 Current dose limits for UK workers and the publ ic are published in the Ionizing Radiations Regulations 1999 and are shown in Table 1.2. Table 1.2 UK annual dose limits (mSv) Annual dose limits Whole body Skin Lens of the eye Radiation workers (classi \201 ed) Trainee (under 18) Radiation workers (non classi \201 ed) Others, including members of the public 20 6 6 1 500 150 50 50 150 50 15 15 The dose limit to the abdomen of a woman of reproductive capacity is 13mSv in any consecuti ve 13-wk period. The dose limit to the fetus once pregnancy has been declared is 1mSv durin g the period of the pregnancy. From HMSO (1999). Ionizing Radiations Regulations . HMSO, Lo ndon. Available at: M http://www.hse.gov.uk/pubns/books/l121.htm 01_Smedley_Chap01.indd 18 12/31/2012 8:42:05 PM This page intentionally left blank CHAPTER 1 Physical hazards 20 Ionizing radiation 3: Instrumentation and measurement Environmental radiation detectors A w ide range of instruments are available. Instruments are based on several types of detectors (gas ionization, solid state detectors, change in chemical systems, and neutron activation ) and are used to quantify incident radiation as a count or dose rate. Such detectors inclu de: \200 Installed ( \201 xed) monitors: used to monitor personal contamination, general radiation, and air contamination level in the working environment Portable (battery operated) monitors: used to measure levels during speci \201 c operations and for contamination surveys. Devices for personal monitoring Movie badges \200 Movie is developed and analyzed for ext ernal radiation dose, in proportion to darkening of the \201 lm Various \201 lters inside the badge differentiate types of radiation and energies