32_Smedley_Chap32.indd 646 1/2/2013 12:54:29 PM LOCAL EXHAUST VENTILATION: ASSESSING PERFORMANCE 647 Capture Zone Working Zone Fig. 32.5 Capture and working zone. Note: The capture zone is the space in front of the hoo d where the air velocity is suf \201 cient to capture the contaminant. The working zone is de \201 ned as the space where the activity generates the contaminant. For effective cont rol, the working zone must be lie within the capture zone of the hood. De \201 nitions \200 Capture velocity : the air velocity required at the source of emiss ion suf \201 cient to cause the pollutant to move towards the mouth of the extractor and t hus be successfully captured Face velocity : the air velocity at the opening of a hood or enclosure \200 Transportatio n velocity : minimum velocity required in the system, including ductwork and extract devices, to keep collected particles airborne and to prevent them from being deposited in the system Static pressure : the pressure exerted by a \202 uid in motion at right angles to the direction of \202 ow Velocity pressure : the pressure equivalent of the kinetic energy of a \202 uid in motion . It is calculated from the expression P v = 0.5 pv 2 where p is the density of air (kg/m 3 ) and v is the velocity of air (m/s). Total pressure : the sum of the static and velocity pressures at a point in an air stream. It can be +ve or \200\223ve relative to atmospheric pressure. Further information and guidance HSE (2011). Controlling airborne contaminants at work \200 \224a guide to local exhaust ventilation (LEV) , HSG258. HSE, Sudbury. Available at: M http://www.hse.gov.uk/pubns/priced/hsg258.pdf HSE (2008). Clearing the air \200\224a simple guide to buying and using local exhaust venti lation (LEV) , INDG408. HSE, Sudbury. Available at: M http://www.hse.gov.uk/pubns/indg408.pdf 32_Smedley_Chap32.indd 647 1/2/2013 12:54:30 PM CHAPTER 32 Prevention and control of exposure 648 Recording the examination and testing of local exhaust ventilation plant A suitable record of each thorough examination and test of LEV should contain the following details \200 The name and address of the employer \200 The identi \201 cation (and lo cation) of the LEV, and the process and substances concerned The dates of the examination and test \200 The process conditions at the time of test, e. g. normal \200 Diagram of the LEV system showing position of hood, \201 lter, fan and test points Information about the LEV plant which shows: its intended operation performance for controlling adequately \200 exposure to hazardous substances \200 whether the LEV is still achieving the same performance \200 if not, th e adjustment or repairs needed to achieve that performance Methods used to make the judgment of performance \200 Results of any air sampling relevan t to LEV performance \200 Name, job title, and employer of the person carrying out the examination and test Observation on the way the operator used the LEV \200 Signature of person carrying out th e test. The employer should have a LEV \200\230user manual \200\231 and a system \200\230logbook \200\231 \200 These documents should be supplied as part of the design, installation, and commissioning process The maximum time between tests for most LEV systems is 14mths (see b p. 532, Control of Substances Hazardous to Health Regulations Regulations 2002) The employer should keep the examination and test report for at least 5yrs. 32_Smedley_Chap32.indd 648 1/2/2013 12:54:30 PM This page intentionally left blank CHAPTER 32 Prevention and control of exposure 650 Personal protective equipment: legal requirements and use De \201 nition PPE is de \201 n ed as all equipment (including clothing) that is intended to be worn or held by a person at work, and which protects him/her against one or more risks to his health or safety. Legal requirements See PPE at Work Regulations 1992 (as amended) Personal protective equip- ment: legal requirements and use, PPE at Work Regulations 1992. The law governing the use of PPE in other speci \201 c regulations is contained in: \200 PPE at Work Regulations 1 992 COSHH 2002 (as amended) \200 Control of Asbestos at Work Regulations 2002 (as amended ) \200 Control of Lead at Work Regulations 2002 \200 Ionizing Radiation at Work Regulat ions 1999 \200 Con \201 ned Spaces Regulations 1997 \200 Control of Noise at Work Regu lations 2005 \200 Construction (Head Protection) Regulations 1989. 1 PPE is considered as the last resort to protect against risks to health and safety. Thus there is a need to dem onstrate \201 rst that the risk cannot be controlled adequately by other means. Use of PPE \200 Effective protection is only achieved by suitable PPE, correctly \201 t ted and maintained, and properly used PPE is used widely, but should be considered as the last resort as: it only reduces exposure for the individual wearer, whereas control at source protects all those in the area the actual level of protection is dif \201 cult to assess \200 it may interfere with wor k tasks/practice \200 it may be uncomfortable and restrict the wearer, limiting movement, and visibility. PPE should be selected and used after justi \201 cation for its use has been made in the r isk assessment. For example RPE can be used in the following situations: \200 where inhal ation exposure remains despite use of other controls, i.e. used minimize residual risk where there is short-term or infrequent exposure and use of other controls is not practical as an interim measure, e.g. when putting in place other controls \200 for emergency respo nse, e.g. safe exit or emergency rescue \200 for emergency work/when there is temporary f ailure of controls. Setting up a effective PPE program Having assessed the risk and implemented all reasonable control meas- ures, the following steps should be considered when setting up a PPE program. 32_Smedley_Chap32.indd 650 1/2/2013 12:54:30 PM PPE: LEGAL REQUIREMENTS AND USE 651 Identify individuals/tasks/environment where PPE is needed \200 Select appropriate PPE to control residual exposure \200 Involve worker in the PPE selection process \200 Match PPE to each individual wearer \200 Carry out \201 t tests for respiratory protective eq uipment (RPE) \200 Ensure the use of PPE does not create additional risks \200 Ensure t hat the PPE is compatible with other PPE \200 Minimize PPE use time by de \201 ning when it should be used, e.g. particular tasks Train the wearer in the correct use of their PPE and supervise use \200 Inspect PPE to en sure it is correctly maintained \200 Provide suitable storage facilities to prevent conta mination \200 Record: PPE issue, maintenance, inspection, and RPE \201 t-testing data \200 Inform individuals of the need for PPE, consequences of PPE failure and the importance of reporting PPE defects. 32_Smedley_Chap32.indd 651 1/2/2013 12:54:30 PM CHAPTER 32 Prevention and control of exposure 652 Selecting respiratory equipment The decision to use RPE should be justi \201 ed in a risk assessment. When selecting RPE consideration must be given to: \200 Individual factors : health status, e.g. cardiorespiratory problems \200 Contaminant : form of substance, sing le substance/mixture, nature of release (energy), concentration and variation, toxicity, OEL Task : duration, other PPE used, mobility, manual dexterity, visibility, communication, work rate (metabolic rate) Environment : indoor/outdoor, temperature, humidity \200 Legal requirements : CE marking, employer and employee duties \200 Costs : equipment, training, testing, repair/replacing storage, and record keeping. RPE protection factors The effectiveness of RPE is indicated by the assigned protection fac tor (APF). The APF is the level of respiratory protection that the respirator (or class of respirators) is expected to provide to employees when it is used correctly. Example: A respirator with an APF of 10 should reduce the workers exposure by a factor of 1 0, i.e. to one-tenth of exposure level in the breathing zone (outside the mask). Therefore the maximum use con- centration (MUC) an employee can be expected to be protected when wear ing this respirator is 10 times the WEL. 1 Whenever the exposure approaches the MUC, then the next higher class of respirator should be selected. APF values assigned to different types of RPE are given in HSG 53 (HSE, 2005). Examples of RPE are shown on b p. 655, Protective equipment. Required protection factor Example: A worker is exposed to dust assigned a WEL 8h TWA = 5mg/m 3 . The daily TWA exposu re is measured to be 20mg/m 3 . In order to reduce the personal exposure to the WEL, the re quired protection (PF) is: PF= 20/5 =4. RPE selector guide HSG 33 (HSE, 2005) describes a generic guide on the selection of RPE whi ch comprises 5 steps: \200 Step1: details about the company and the work environment 32_Smedley_Chap32.indd 652 1/2/2013 12:54:30 PM SELECTING RESPIRATORY EQUIPMENT 653 Step 2: information on control measures currently in use (other than RPE), reasons for want ing to use RPE, whether work is to be carried out in a con \201 ned space, and risk of oxy gen de \201 ciency Step3: determination of the health hazard group (HHG) for the substance and the level of protection needed. The HHG is based on risk phrases assigned to the substance. The required PF is determined from the combination of HHG and the amount of substance used and its dustiness/volatility Step 4: consideration of tasks and individual factors that may affect the selection of the RPE, e.g. work rate, mobility, medical conditions \200 Step 5: consider need to test the selected RPE for a good \201 t over the mouth and nose ( \201 t test). RPE \201 t testing A major cause of leaks for RPE equipment is poor \201 t. Fit testing will ensure that the RPE selected is suitable to the individual wearer. \200 Tight- \201 tting RPE must be \201 t tested as part of the initial selection stage \200 The \201 t-test report should include the following: name of the person \201 t tested \200 make, model, type, and size of face-piece tested \200 exercises performed during the test \200 the test method (qualitative or quantitat ive) \200 measured \201 t factor if applicable \200 date of test \200 details of pe rson carrying out the test Fit testing should be conducted by a competent person. Competence can be demonstrated throu gh achieving accreditation under the \200\230Fit2Fit RPE Fit Test Providers Accreditation Scheme \200\231 developed by the British Safety Industry Federation (BSIF). For further det ails on the scheme, see M http://www. \201 t2 \201 t.org. Further information HSE (2005). Respiratory protective equipment at work. a practical guide , HSG 53. HSE Books, Sudbury. Available at: M http://books.hse.gov.uk/hse/public/saleprodu ct.jsf?catalogueCode= 9780717629046 BSI (2005) Respiratory protective devices \200\224recommendations for the selection, use, c are and mainte- nance , guidance document BSEN529. BSI, London. 32_Smedley_Chap32.indd 653 1/2/2013 12:54:30 PM CHAPTER 32 Prevention and control of exposure 654 Types of respiratory protective equipment \200 RPE can be divided in to two main types: respirator ( \201 ltering device) \200\224i.e. \201 lter used to remove contaminants; d o not use for protection in situations with reduced oxygen levels \200 breathing apparatu s (BA) \200\224requiring a supply of breathing quality air from an independent source, e.g. air compressor, air cylinder \200 Both types are availab le with different face pieces. Masks (Fig. 32.6) rely on a good seal with the wearer \200\231s face. Hoods, helmets, and visors (loose- \201 tting face pieces) rely on clean air being provided to the wearer to prevent leak-in o f contaminants (Fig. 32.7). Filter for respirators There are three main types of \201 lter: particle \201 lter, gas /vapor \201 lter, and combined \201 lter. Examples of different types of RPE available are shown in Tables 32.1 and 32.2. \200 Particle \201 lters are marked with a \200\230 P \200\231 sign and \201 ltration ef \201 ciency number 1 (low), 2, or 3 (high). If the \201 lter is re-useable with fan-assisted respirat ors they will also have a sign \200\230TH \200\231 or \200\230TM \200\231 Gas/vapor \201 lters are categorized by the substance type they can be used against. The \201 lter is marked with a letter indicating type, a number to indicate capacity (1 = low , 2 = medium, 3 = high) and a color code. See Table 32.2. Combined \201 lters are marked for both particles and gas/vapor, e.g. A1P3 \200\224organi c vapor with capacity class 1 and high ef \201 ciency particle \201 lter. 32_Smedley_Chap32.indd 654 1/2/2013 12:54:30 PM TYPES OF RESPIRATORY PROTECTIVE EQUIPMENT 655 Half-mask respirator against gasses/vapors Fresh air hose BA Respirator against particles Contant flow air line BA with mask Powered (fan-assisted) respirator with mask Demand valve BA Fig. 32.7 Types of breathing apparatus. Powered (fan-assisted) respirator with hood Fig. 32.6 Types of respirator. 32_Smedley_Chap32.indd 655 1/2/2013 12:54:30 PM 3 2 _ S m e d l e y _ C h 6 5 6 a p 3 2 . i Table 32.1 Protection values for different types of RPE n d d C H A P T E R 6 Respirators Breathing apparatus 5 6 Full face mask, particle \201 lters Full face mask, gas \201 lters Powered (fan-assisted) masks Powered (fan-assisted) hoods 3 2 P r e v e n t i o n Half-mask, particle \201 lters Half-mask, gas \201 lters Fresh air hose Constant \202 ow airline BA Demand valve BA PF required P1 4 FFP1, FMP1, P1 10 FFP2, FMP2, P2 FF gas, FM gas, Gas P2 TM1 TH1 LDH1 a n d c o n t r o l 20 FFP3, FMP3, P3 Gas TM2 TH2 LDH2, LDM1, LDM2, Half-mask o f 40 P3 TM3 TH3 Full face mask, Hood LDH3, LDM3, Hood, Full mask e x p o s u r e 200 Suit 2000 Airline, self-contained From HSE (2005). Respiratory protective equipment at work , HSG 53. HSE Books, Sudbury, p. 30. Crown copyright, material is reproduced with the permission of the Controller of HMS O and Queen \200\231s Printer for Scotland. 1 / 2 / 2 0 1 3 1 2 : 5 4 : 3 1 P M TYPES OF RESPIRATORY PROTECTIVE EQUIPMENT 657 Table 32.2 Gas/vapors \201 lters Filter type For use against Color code Other information Brown EN 14387 A Organic gasses and vapors, boiling point >65(cid:6)C Inorganic gasses and vapors B Gray EN 14387. Do not use against carbon monoxide E SO 2 and other acid gasses Yellow EN 14387 K Ammonia and its organic derivatives Green EN 14387 Hg Mercury Red and white EN 14387, includes P3 particle \201 lter. Max. use time 50h NO Oxides of nitrogen Blue and white EN 14387, includes P3 particle \201 lter. Single use only AX Organic gasses and vapors, boiling point <65(cid:6)C Substance as speci \201 ed by the man ufacturer Brown EN 14387. Single use only SX Violet EN 14387 From HSE (2005). Respiratory protective equipment at work , HSE 53. HSE Books, Sudbury, p. 28. Crown copyright, material is reproduced with the permission of the Controller of HMS O and Queen \200\231s Printer for Scotland. Further information HSE (2005). Respiratory protective equipment at work: a practical guide , HSG53. HSE Books, Sudbury. 32_Smedley_Chap32.indd 657 1/2/2013 12:54:31 PM CHAPTER 32 Prevention and control of exposure 658 Hearing protectors Requirements, types, use, and maintenance \200 Guidance on hearing pro tection can be found in the CNAWR 2005 ( b p. 548, Control of Noise at Work Regulations 2005). More detailed information can be fo und in BS EN 458:2004 Hearing protectors, Recommendations for selection, use, care and main tenance \200 Under CNAWR the use of personal hearing protectors (HP) is compulsory for employees whose exposure to noise is likely to reach either of the upper exp osure action values, i.e. 85dB(A) and 137dB(B) and for any employees working within areas a ssigned as hearing protection zones HP should be used where additional protection is needed above what can be achieved using ot her methods of noise control (e.g. engineering) and as a short term measure Avoid HPs that over protect the worker, i.e. reducing the level at the ear below 70dB HPs must be CE marked showing that it meets the European Standard BS EN 352 HPs include earmuffs and earplugs; the latter can be custom molded. \200 Most HPs provide greater protection at higher frequencies than at lower frequencies. Earmuffs Easy to \201 t, re-useable, clearly visible, and hence easy to monitor. They may be uncomfortable in warm conditions. Long hair, beards, jewelry, or glasses may reduce pro tection. More expensive than ear plugs. \200 Seals: check seals for cleanliness, hardenin g, and damage \200 Cup: check for cracks, holes, damage \200 Headbands: avoid over-bend ing and twisting, check tension \200 Store in a clean environment. Earplugs More suitable when used with other PPE, e.g. safety glasses. Workers who suffer fr om recurrent otitis externa may be unable to tolerate earplugs. Custom-made plugs are more comfortable and are easier to \201 t for some wearers. However, need to conduct \201 t tests before putting into use. \200 Reusable plugs: clean regularly, ensure not damaged o r degraded \200 Issue to individual: not to be shared \200 Require careful insertion to ensure effective protection \200 Provide greater protection at higher than low frequency \200 Risk of infection (dirty hands) \200 Disposable plugs: use only once. Special protector types \200 Level-dependent (or amplitude-sensitive) protectors: designe d to protect against noise, but allow communication during quieter periods. \200 Flat or tailored freq uency protectors: these provide similar protection across all frequencies which can assist communication. Useful where 32_Smedley_Chap32.indd 658 1/2/2013 12:54:31 PM HEARING PROTECTORS 659 it is important to be able to hear high-frequency sound at the correct level relative to lo wer-frequency sounds, e.g. musicians. Active noise reduction (ANR) protectors: incorporate an electronic sound-canceling system enabling additional noise attenuation. Effective at low frequencies (50 \200\223500Hz). Protectors with communication facilities: these use a wire or aerial to rely signals, alarm s, and messages to the wearer. The signal level should not be too loud and the microphone s hould be switched off when not in use. Selecting hearing protectors When selecting HPs the following should be considered: \200 Noise level (personal) and exposure variation \200 Pattern of exposure \200 Noise reduc tion (attenuation) provided by the protector \200 Work environment (temperature, humidity , dust, dirt) \200 Compatibility with other PPE worn \200 Comfort and wearer preference \200 Hearing needs: communication, hearing warning sounds, conducting tasks Costs: equipment, maintenance, training \200 Health problems: ear infections, discharge, etc. \200 Legal requirements. Further information BS EN 458:2004 Hearing Protectors. Recommendations for Selection, Use, Care and Maintenance. Guidance Documents. 32_Smedley_Chap32.indd 659 1/2/2013 12:54:31 PM CHAPTER 32 Prevention and control of exposure 660 Predicting noise reduction The noise level at the ear (L \200\231 A ) when hearing protecti on is worn can be estimated using three different methods (octave band method, high, medium , and low frequencies (HML) method, and single rating number (SNR) method). L \200\231 A is estimated by subtracting the estimated noise reduc- tion (using manufacturer \200\231s per formance data) from measured noise data. Manufacturers \200\231 hearing protection data The supplier must provide the following info rmation for the HP. An exam- ple of supplier data is shown in Table 32.3: \200 Mean and s tandard deviation attenuation values at each octave band center frequency (63Hz \200\2238KHz) Assumed protection values (APrV) at each frequency, i.e. mean protection minus one SD \200 H, M, L and SNR values. Noise level data required for estimating protection The following types of noise data shoul d be measured depending on the method chosen (one of three) to calculate the attenuation af forded by the ear protector. \200 Octave band analysis: requires measurement of noise lev el at each octave center frequency for the range 63Hz \200\2238kHz HML require measurement of the A-weighted (LA) and C-weighted (LC) sound pressure levels SNR: requires single measurement of LC only. Predicting attenuation using the HSE electronic spreadsheet The measured noise levels and m anufacturer \200\231s data can be entered into an electronic spreadsheet to calculate the a ttenuation afforded by the chosen ear protector. The spreadsheet is available on the HSE we bsite (M http:// www.hse.gov.uk/noise). Of the three methods, the octave band analysis meth od provides the best estimate for L \200\231 A . Hearing protectors usually give lower protection than predicted by manufactures data due to , e.g. poor \201 tting. The difference between manu- facturers \200\231 data and \200 \230real-world data \200\231 is accounted for in the HSE calculator by \200\230derating \200\231 the protection by 4dB. Protector use time If HP is removed in a noisy area, even for short period, amount of prote c tion provided will be reduced (Fig. 32.8). Information for employees Employees should be provided with information on HPs including: \200 Why and where HPs need to be worn? \200 How replacements can be obtained? \200 Ho w to wear HPs with other personal protection? \200 How to check, store, and report damage to HPs? 32_Smedley_Chap32.indd 660 1/2/2013 12:54:31 PM PREDICTING NOISE REDUCTION 661 Table 32.3 Example of noise attenuation data supplied by manufacturers Octave band center frequency (Hz) 63 125 250 500 1000 2000 4000 8000 Mean attenuation 17.3 21 24.5 27.3 27.9 33.8 36.1 40.8 Standard deviation (dB) 5.4 5.3 6.7 6.6 4.8 3.7 5.2 6.5 Assumed Protection Value (APV) 11.9 15.7 17.8 20.7 23.1 30.1 30.9 34.3 Single number values H 29 M 23 L 20 SNR 27 APV, mean attenuation minus 1 SD. 30 30 25 25 ) B d ( A 20 n o i t a u n e t t a 20 B 15 15 C e v i t c e f f E 10 10 5 5 0 0 100 90 80 70 60 50 Fig. 32.8 Effectiveness of hearing protectors in relation to time worn. Protectors providin g (A) 30dB attenuation, (B) 20dB attenuation, and (C) 10dB attenuation. From HSE (2005). Th e Control of Noise at Work Regulations 2005 . HSE Books, Sudbury. Material reproduced with permission from the Controller of HMSO, 32_Smedley_Chap32.indd 661 1/2/2013 12:54:31 PM CHAPTER 32 Prevention and control of exposure 662 Gloves Glove selection and use Gloves differ in design, material, thickness, and size. The following factors should be considered when selecting gloves to avoid contact with harmful substances: \200 The substance types handled (Tables 32.4 and 32.5) and their dermal effects (local and systemic) Type and duration of dermal contact \200 The user: size (use sizing charts) and comfort. \200 The tasks: e.g. manual dexterity requirements, need for sterile gloves \200 Work e nvironment (temperature and humidity). Check that correct gloves have been selected using s upplier \200\231s perform- ance data, and that the glove user is not allergic to the glove material, e.g. powdered latex gloves. The HSE glove selection memory aid (from HSG262) is a vailable on web page M http://www.hse.gov.uk/skin/resources/ glove-selection.pdf Glove failure Protective gloves can fail to protect the wearer from exposure to chemi- cals in different ways. \200 Permeation: chemical migrates through glove \200 Penetration: bulk \202 ow of chemical through seams, pinholes, closures, porous materials, or other imperfections Degradation: change in physical properties of glove material as a result of exposure to a chemical agent. 2 The breakthrough time is de \201 ned as the time between the initial applica- tion of a test chemical to the outside surface of the protective glove and its subsequent presence on the inside of the material. Glove performance data Glove suppliers usually provide chemical resistance charts, with glo ve per- formance for different chemicals. Performance is rated using the following data: \200 Breakthrough time: ranges from 1 \200\22310 to >480min. \200 Permeation rate: fast, medium, or slow \200 Degradation : scale 0 \200\2236. Applications \200 Protection from cuts and abrasion, handling sharps \200 Keeping hands warm in cold weather when using machines that cause HAVS Handling chemicals, radio-active materials, hot or cold materials \200 Danger of electric al hazards \200 Work involving naked \202 ame, welding. Gloves should be checked regula rly and replaced if they are worn or have deteriorated. Workers should receive training in the correct way to care for, put on, wear, and take off gloves. Need to also ensure that th ere are adequate facilities for storage, cleaning, replacement, and disposal of gloves. 32_Smedley_Chap32.indd 662 1/2/2013 12:54:32 PM GLOVES 663 Table 32.4 Glove selection Protection against Glove type (examples) Penetration and abrasion Leather, Kevlar Thermal Terrycloth (protect against heat and cold) Neoprene (handling oils at low temperature) Fire Chromated leather gloves Chemical protection Neoprene, natural rubber, nitrile, butyl, PVA, PVC, Vitron Table 32.5 Glove materials for chemical protection Glove type Protection against Limitations Prone to swelling with some solvents Nitrile (synthetic rubber) Oil-based chemicals, lubricants, aliphatic solvents and aqueous chemicals PVC Aqueous chemicals, e.g. acids and alkalis Protection for some solvents limited because of plasticizers Neoprene Gasoline, oil, lubricants PVA Most organic solvents Soluble in water Butyl Strong acids Poor resistance to oils and lubricants Viton Chlorinated solvents and aromatic hydrocarbons Poor resistance to ketones Powdered gloves may cause allergic reactions and sensitization Latex Aqueous chemicals Further information HSE (2009). Managing skin exposure risk at work , HSG262. HSE Books, Su dbury. Available at: M http://www.hse.gov.uk/pubns/priced/hsg262.pdf 32_Smedley_Chap32.indd 663 1/2/2013 12:54:32 PM CHAPTER 32 Prevention and control of exposure 664 Protective clothing Protective clothing includes separates (jacket, trousers), aprons, over alls, coveralls, and body suits. Applications \200 Chemical work protecting against accidental spillages: use aprons \200 Contact with sprays or jets of chemicals: use coveralls \200 Wet working: using water s prays for cleaning, use rubbers, plastic, water-repellent coatings, waterproofs, breathable fabrics Radiant heat from welding, foundries: \202 ame-retardant, insulating, and heat-resistant fabric Electrical and electrostatic hazards: materials which resist build-up of static electricity. Precautions \200 When selecting protective clothing consider the chemical resistance and protection, protection against mixtures, and breakthrough times recommended by the manufact urer Store used/contaminated clothing separate from clean clothing \200 Inspect for wear and t ear/loose seams and damage \200 Do not wear loose protective clothing close to moving mac hines \200 Clean clothing following the manufacturer \200\231s instructions. 1 If protect ive gloves or clothes are worn incorrectly this may increase the risk to the individual. \200 Contaminant may get inside the protective device (glove) and be occluded, resulting in higher exposure Prolonged use may cause moisture (sweat) on skin which can act as an irritant Reduces heat loss, which may increase likelihood of heat stress \200 Latex gloves may cau se an allergic reaction in susceptible individuals ( b p. 202, Latex allergy) Gloves worn near moving equipment and machinery parts may be caught in the equipment, drawing the worker \200\231s hand into the moving machinery. Further information HSE (1992). Personal protective equipment at work regulations 1992 (as amended). HSE Books, Sudbury. HSE (1992). A short guide to personal protective equipment at work regulations 1992 . HSE, Sudbury. Available at: M http://www.hse.gov.uk/pubns/indg174.pdf 32_Smedley_Chap32.indd 664 1/2/2013 12:54:32 PM This page intentionally left blank CHAPTER 32 Prevention and control of exposure 666 Eye and face protection Types of eye and face protection Eye protection can be divided into three basic types: \200 Safety spectacles: separate lenses in metal or plastic frame wit h side shields Goggles: \202 exible plastic frame with one or two lenses and \202 exible headband. With the rim in contact with the face, goggles provide eye protection from all si des Face shields or visors: one large lens with a frame and adjustable head harness or mounted on helmet. Can be worn with prescription lenses. Protects the face, but eyes are not fully enclosed. Applications Eye protection is required for the following hazards: \200 Splashes of chemi cals, e.g. acids or body \202 uids \200 Chipping and debris from use of power-driven to ols on metals, woods, etc. Molten metal, radiant heat sparks, or hot liquid splashes from furnaces \200 Intense ligh t (lasers) and other optical radiation likely to cause risks to the eye, e.g. UV light from welding. Selecting eye and face protection Table 32.6 shows examples of eye protection for different hazard types. Table 32.6 Eye protection and hazards Hazard Eye protection equipment Examples Flying swarf Chiseling Impact Spectacles with toughened lenses/side screens Dust Goggles Air-fed positive pressure hood with visor Grinding Shot-blasting Molten metal Goggles Casting and pouring Face shield or visor Radiation (non-ionizing) Goggles, tinted Face shield or visor with correct protective shade Sunglasses Welding and lasers (UV radiation) Casting and pouring molten metal/glass (IR radiation) Out door work (UV radiation) Exposure to gasses, vapors, liquids, dusts, biological agents Chemical or biological Goggles Face shield or visor 32_Smedley_Chap32.indd 666 1/2/2013 12:54:32 PM EYE AND FACE PROTECTION 667 Precautions \200 Issue eye protection on a personal basis and ensure that it \201 ts pr operly \200 Stored in a protective case \200 When cleaning, follow manufacturer \200 \231s instructions \200 Do not use when the visibility (scratched and worn lenses) is red uced or the headband is damaged or worn Lens may mist: use anti-mist sprays or ventilation eye protection. Standards for selection, use and maintenance BS 7028: 1999 Eye Protection for Industrial an d Other Uses. Guidance on Selection, Use and Maintenance . Further information and guidance HSE (2009). European standards and markings for eye and fa ce protection , OM 2009/3. Available at: M http://www.hse.gov.uk/foi/internalops/fod/om/2009/03app3.pdf British Standards on eye protection. Available at: M http://www.bsigroup.co.uk/DualSearch/ ?q=eye+protection 32_Smedley_Chap32.indd 667 1/2/2013 12:54:32 PM This page intentionally left blank Section 7 Toxicology 33 Principles of toxicology 671 33_Smedley_Chap33.indd 669 1/2/2013 12:56:02 PM This page intentionally left blank 671 Chapter 33 Principles of toxicology Toxicology and dose \200\223response 672 Toxicokinetics and types of toxic effect 674 Asses sment of toxicity and evaluation of toxicological data 676 Occupational exposure limits 678 33_Smedley_Chap33.indd 671 1/2/2013 12:56:02 PM CHAPTER 33 Principles of toxicology 672 Toxicology and dose \200\223response Toxicology is the study of the adverse effects of chem icals in humans and other living organisms. It plays a fundamental role in chemical risk as sessment. Dose \200\223response relationship The dose \200\223response relationship refers to the cor relative relationship between exposure to a chemical (dose) and the effect that occurs (res ponse). Classi \201 cation of dose \200\223response Two types of dose \200\223response relationshi p exist. Graded dose \200\223response This relates to the occurrence of effects in an individual , w ith the response varying in severity according to dose. Quantal dose \200\223response This relates to the distribution of a speci \201 c response within a population . For many chemicals, the quantal dose \200\223response relationship is charac- terized by a normal frequency distribution, represented in a frequency histogram b y a bell-shaped curve. This distribution re \202 ects differences in susceptibility to che micals within a population (biological variation), indi- cating the presence of sensitive i ndividuals and resistant individuals. Dose \200\223response parameters Several parameters can be derived from the dose \200\223re sponse relationship. \200 NOAEL : the dose at which no observable adverse effects occur \200 Lowest observable adverse effect level (LOAEL) : the lowest dose at which adverse effects are observed Threshold : the dose below which the probability of an individual responding is zero LD50 : median lethal dose, a single dose of substance that can be expected to cause death in 50% of experimentally exposed animals. This value is determined in acute systemic toxicity tests and is used to indicate the relative acute toxicity of a s ubstance. Patterns of dose \200\223response \200 With essential elements and vitamins, the shape of the graded dose \200\223response relationship in an individual is U-shaped, representing adverse effec ts which occur at low doses (de \201 ciency) and at high doses (toxicity) (Fig. 33.1) With genotoxic carcinogens, the response (development of cancer) is considered not to have a threshold (i.e. there is no dose that is associated with zero risk) (Fig. 33.2). 33_Smedley_Chap33.indd 672 1/2/2013 12:56:02 PM TOXICOLOGY AND DOSE \200\223RESPONSE 673 e s n o p s e R Region of homeostasis Deficiency Toxicity Dose Fig. 33.1 Dose \200\223response relationship for an essential substance. 100 e s n o p s e R % A B NOAEL Dose Fig. 33.2 Comparison of dose \200\223response for two compounds (A) with no threshold and ( B) with threshold. 33_Smedley_Chap33.indd 673 1/2/2013 12:56:02 PM CHAPTER 33 Principles of toxicology 674 Toxicokinetics and types of toxic effect Toxicokinetics The toxicokinetics of a substance i s the quantitation and time course of four components: \200 Absorption \200 Distributio n \200 Metabolism \200 Excretion. The toxicokinetics of a substance determines its conc entration at the tar- get organ/tissue and consequently determines its toxicity. Absorption This is the process by which substances cross membranes in the body and enter th e bloodstream. Main routes of absorption are the respiratory tract (inhalation), the skin ( dermal), and the GI tract (oral). Distribution This is the translocation of substance within the body after it has been absor bed into the blood. Metabolism (or biotransformation) This is the process by which a substance, once it is abso rbed, is changed into one or more chemically different substances (metabolites). Excretion This is the process by which a substance and/or its metabolites are elimi- nated from the body. Route and rate of excretion vary according to the substance, the most common routes being: \200 Urine \200 Feces \200 Exhaled breath. Excretion of the substance (or its metabolites) may be used for biological monitoring purposes. Types of toxic effect Several terms are used to describe the toxic effects that are associa ted with exposure to a substance. Frequently used terms are de \201 ned in the following s ection. \200 Acute effects : resulting from short periods of exposure to a relatively hig h concentration/dose of chemical, e.g. irritation of eyes, skin, and respiratory tract (tol uene, arsenic), and central nervous system depression ( n -hexane) Chronic effects : caused by repeated or prolonged exposure to a relatively low concentration/dose of chemical, e.g. central nervous toxicity (toluene), can cer of respiratory tract, skin, and liver (arsenic), and peripheral neuropathy ( n -hexane) Local effects : occur at the site of \201 rst contact with a substance 33_Smedley_Chap33.indd 674 1/2/2013 12:56:02 PM TOXICOKINETICS AND TYPES OF TOXIC EFFECT 675 Systemic effects : occur only after the substance has been absorbed into the body Immediate effects : these develop soon after exposure takes place. In contrast, delayed eff ects only become apparent some time after exposure has taken place; perhaps months or years later Reversible effects : subside once exposure ceases \200 Irreversible effects remain follow ing cessation of exposure; in some cases, irreversible effects may become progressive. Speci \201 c toxic effects Carcinogenesis Carcinogenesis is a multistage process in which exposure to a substance leads to genetic damage within the cell, resulting in uncontrolled prolif- eration of cells and ultimately the occurrence of a tumor. Carcinogenic substances are generally divided into: \200 Genotoxic mechanism: those which cause cancer by direct damage to the genetic material Non-genotoxic mechanism: those which cause cancer by indirect damage to the genetic material. Mutagenesis This is a permanent change in the genetic material of a cell (DNA), involv- ing a single gene, a block of genes, or an entire chromosome, which is passed on to the next g eneration of cells. A mutation in germ cells (repro- ductive cells such as sperm and ova an d their precursors) can result in genetic damage that is passed on to offspring (heritable genetic defects). A mutation in somatic cells (non-reproductive cells) may lead to the deve l- opment of cancer. Respiratory sensitization A state of speci \201 c airway hyper-responsiveness that is indu ced in some individuals by certain substances (respiratory sensitizers or asthmagens). Immu nological or irritant mechanisms may be involved. Skin sensitization An immunologically mediated skin reaction which occurs in some individu- als as a result of skin contact with certain substances. 33_Smedley_Chap33.indd 675 1/2/2013 12:56:02 PM CHAPTER 33 Principles of toxicology 676 Assessment of toxicity and evaluation of toxicological data Assessment of toxicity EU legis lation requires that chemicals placed on the market must undergo a risk assessment to deter mine the risks to humans and the environment. An important part of the risk assessment proc ess involves determining the intrinsic harmful properties of the substance (hazard identi \201 cation) using toxicological data. Toxicological testing Toxicological data may come from animal, human, or in vitro studies, or be based on structure \200\223activity relationships (SARs). Toxicological data for new substances and, when necessary, for existing substances are obtained using standardized tes t methods which are contained in Annex V of Directive 67/548/EEC. The standardized toxicity tests are conducted in laboratory animals or using in vitro systems. \200 Existing subst ances: any substance listed in the European Inventory of Existing Commercial Chemical Subst ances (EINECS). All substances which were commercially available in EU between January 1971 and September 1981 appear in EINECS, comprising 100,204 substances. An EINECS number is as signed to each substance.