24 noise vibration and occupational medicinePresentation Transcript
OCCUPATIONAL MEDICINE• Branch of medicine which is devoted for the promotion and protection of workers health.• Early diagnosis and treatment of diseases of occupational origin, and rehabilitation of disablement of workers.
Historical Background• Paracelsus, 1493 – 1541.• Bernardino Ramazzini, 1633 – 1714.• Charles Turner Thackrah,1795 – 1833.• Promulgation of Factory Act, 1819.• Appointment of Certifying Factory Surgeon, 1884.
Occupational Health Hazards• Physical agents : Heat, Light, Cold, Humidity, Air pressure, Vibrations, Noise, E.M.F., Injurious force, Dusts, Radiant energy.• Chemical agents : Noxious gasses, Aerosols, Corrosives, Solvents, Metals and Metal fumes, Insecticides and Herbicides.
• Biological agents : Bacterias, Viruses, Fungi, Molds and other biological agents.• Mechanical agents : badly maintained machines, Lack of protective devices .• Social factors : Job security and working conditions, work related tensions and worries, family pressures.
• Noise : Hearing impairment, hearing loss.• Light : headache, loss of concentration and miners nystagmus.• E.M.F.: Headache, sleep disturbances, risk of blood and brain cancer.• Radiant energy :a) Cosmic radiation :- Cataract, skin cancer. b) U.V. radiation :- Skin and bone cancer.• Injurious force : injuries and accidents.
• Ionising radiation : a) acute effects :- Radiation burns, acute radiation syndrome. b) delayed effects :- Genetic mutations, cancers, teratogenesis. Dusts : organic and inorganic :- Respiratory diseases, Pneumoconioses. Chemical agents : Burns, Occupational dermatoses and cancers. Biological agents : Various agent specific diseases. Social factors : Nature of work and working hours, Jealousy in promotions, poor housing, less pay, separation from family and lack of job satisfaction.
Noise Noise is often defined as “unwantedsound”, but this definition is quitesubjective. A better definition of noise is “wrongsound, in the wrong place, and thewrong time, leading to healthhazard”. Noise has become a veryimportant stress factor in theenvironment of man and the term “NoisePollution” has been accepted. Noise is also one of the most commonof all the occupational hazards.
Sources of noise – they are manyand varied. These are automobiles, factories,industries – woodcutters, textiles, primarymetals, petroleum and coal, chemicals,printing and publishing, aircraft etc. The domestic noises from the radios,TV sets, vacuum cleaners, elevators etc.add the quantum of noise in daily life. Properties – noise has two importantproperties – intensity or loudness, and - frequency.
INTENSITY Intensity or loudness dependsupon the amplitude of thevibrations, which initiated thenoise. The intensity of noise ismeasured in decibels (dB). Whenwe say that sound is 60 dB, itmeans that it is 60 dB more intensethan the smallest distinguishablenoise. Normal conversationproduces a noise of 60-65 dB.
Acceptable noise levels (dB/A)Acceptable noise levels (dB/A)Residential: Bed room 25 Living room 40Commercial: Office 35-45 Conference 40-45 Restaurants 40-60Industrial: Workshop 40-60 Laboratory 40-50Educational: Class room 30-40 Library 35-40Hospitals: Wards 20-35
Sound levels of some noisesSource of noise Sound Level (dB/A)Wishper 10Speech, 2-3 people 73Speech on radio 80Music on radio 85Children shouting 79Children crying 80Vacuum cleaner 76Piano 86Jet take off 150
It has been observed that the humanear responds in a non-uniform way todifferent sound pressure levels, that is, itresponds not to the real loudness of asound, but to the perceived intensity. A weighting curve A has beenconstructed, which takes into account thesubjective effects of the sound. Soundpressure levels are therefore expressed indB (A). This is in decibels conforming tothe weighting curve A and reflects theperception of that sound emission by thenormal human ear.
Community noise levels160 Mechanical damage150140 Threshold of pain130120 Motor car horn110 Train passing station10090 Recommended maximum (85 dB)80 Printing-press70 Heavy street traffic60 Normal conversation5040 Quiet library3020 Whispering10
FREQUENCY The frequency is denoted inHertz (Hz). One Hz is equal to onewave per second. The human earcan hear frequencies from about20 to 20 000 Hz, but this range isreduced by age and othersubjective factors. The range offrequencies below 20 Hz are infra-audible, and those above 20 000Hz are ultra-sonic.
Measurement of noise The basic instruments used instudies on noise are: 1. Sound level meter, whichmeasures the intensity of sound in dB ordB (A) 2. Octave-band frequencyanalyzer, which measures the noise inoctave bands. The resulting plot showsthe “sound spectrum” and indicates thecharacteristics of the noise, whether itis mainly of high frequency, lowfrequency or of variable frequency.
3. Integrating sound level meterand Noise dose meter or “dosimeter”(for measuring mainly of industrial noise).For measuring of non-steady noiseexposures, such as those that occur inintermittent or impulse noise, an integratedsound level meter is most convenient to use,which measure simultaneously theequivalent, peak and maximum sound levels. The noise dose meter or “dosimeter”is a form of integrating sound level meterthat can be worn in shirt pocket or attachedto the worker’s clothing. Data form thedosimeter may be computerized or printed
Measuring procedures in the workplace There are two basic approaches to measuring noise in the workplace:• The exposure of each worker, worker type or worker representative may be measured. The noise dosimeter is the preferable instrument for this purpose.• Noise levels may be measured in various areas, creating a noise map for the determination of risk areas. In this case, a sound level meter would be used to take readings at regular points in a coordinate network.
Effects of noise exposure Auditory effects• Auditory fatigue – it appears in the 90 dB region and greatest at 4000 Hz.• Deafness or hearing loss – this is the most serious pathological effect. When this occurs as a result of occupation in industries, it is called “occupational hearing loss”. Hearing loss may be temporary or permanent. The temporary one results from a specific exposure to noise and disability disappears after about 24 hours. Repeated or continuous exposure to noise above 85-90 dB may result in a permanent hearing loss.
Non – auditory effects Annoyance – a primarypsychological aspect; neuroticpeople, especially workersoccupationally exposed to highnoise become often irritated andimpatient and disruptproduction, which also reducesthe efficiency of work witheconomic losses.
Non – auditory effects Physiological changes – anumber of temporary psychologicalchanges occur in the human body asa direct result of noise exposure.These are: a rise in blood pressure, arise in intracranial pressure, anincrease in heart rate and breathingand an increase in sweating, increasein catecholamines production,alteration in the functions ofgastrointestinal and endocrinesystems etc. General symptoms asfatigue, nausea, visual disturbancesmay also occur.
Control of noise Careful planning of cities – in planning cities, the following measures should be taken to reduce noise:• Division of the cities into zones with separation of areas concerned with industry and transport and separation of residential areas from the main streets by means of wide green belts. House fronts should lie not less than 15 meters from the road and the intervening space should be thickly planted with trees and bushes.
Control of vehicles – heavyvehicles should not be routed into narrowstreets; traffic on residential streetsshould be reduced. Improving of the acousticinsulation of buildings – from theacoustic standpoint, the bestarrangement is construction of detachedbuildings than a single large building.Installations that produce noise ordisturb the occupants within dwellingsshould be prohibited. Buildings should besound-proof where necessary.
Control of industrialnoise – control of noise atsource is possible inindustries. The use ofwritten specifications todefine the requirements forequipment, its installation,and acceptance should be astandard practice. Once theequipment is installed andexcess noise identified,there are:
- Engineering controls available.Such are: replacement oradjustment of machines,lubrication of machine parts,reducing noise by using soundabsorptive materials on wallsand ceilings in work areas, byusing sound barriers along thetransmission path or completeenclosure of individual machines,isolation of the operator by providinga relatively soundproof booth.
- Personal hearing protection – itis recommended for all workers whoare consistently exposed to noiselouder than 85 dB in the frequenciesabove 150 Hz, and is performed byuse of hearing-protective devices.Workers must be regularly rotatedfrom noisy areas to comparativelyquiet posts in factory. Periodicalaudiogram check-ups are alsoimportant for worker’s healthprevention. Workers have the right toclaim compensation if they havesuffered a hearing loss.
Vibration Vibration is oscillatory motion. Whole-body vibration occurs whenthe body is supported on a surfacewhich is vibrating (e.g., when sitting ona seat which vibrates, standing on avibrating floor or surface). Whole-bodyvibration occurs in all forms of transportand when working near some industrialmachinery – buldozers, excavators,eorest machines, mine and quorryequipment, concrete productionproduction etc.
Hand-transmitted vibration isvibration that enters the bodythrough the hands. It is caused byvarious processes in industry,forestry, agriculture, mining, andconstruction where vibrating tools orworkpieces are grasped or pushed bythe hands or fingers. The main parameters of vibrationthe health effects depend on are:
Magnitude Oscillatory displacements of an objectinvolve a velocity in one direction and thena velocity on the opposite direction. Thischange of velocity means that the object isconstantly accelerating, first in onedirection and then in the oppositedirection. The magnitude of an oscillationcan be quantified by its displacement, itsvelocity or its acceleration. The units ofacceleration are meters per second(m/s2).
The magnitude ofvibration can be expressedas the distance between theextremities reached by themotion (the peak-to-peakvalue) or the distance fromsome central point to themaximum deviation (thepeak value), this is alsocalled amplitude.
FrequencyThe frequency of vibration, whichis expressed in cycles per second(Hz), affects the extent to whichvibration is transmitted to thebody (e.g. to the surface of a seator the handle of a vibratory tool),the extent to which it istransmitted through the body(e.g. from the seat to the head),and the effect of vibration inthe body.
The relation between thedisplacement and the acceleration of amotion are dependent on the frequency ofoscillation; a displacement of one mmcorresponds to a very lowacceleration at low frequencies but avery high acceleration at highfrequencies.
The effects of whole-bodyvibration are usually greatest at therange from 0.5 to 100 Hz. For hand-transmitted vibration, frequenciesas high as 1000 Hz or more mayhave adverse health effects.Frequencies below about 0.5 Hz cancause motion sickness.
The frequency content ofvibration can be shown in spectra.For many types of vibration thespectra are complex, with somemotion occurring at allfrequencies. Nevertheless, thereare often peaks, which show thefrequencies at which most ofthe vibration occurs.
Direction Vibration may takeplace in three directions –x-axis (fore-and-aft), y-axis(lateral) and z-axis(vertical). Vibration is usuallymeasured at the interfacebetween the body and thevibration.
Duration Human responses to vibration dependon the total duration of vibration exposure. Many occupational exposures areintermittent, vary in magnitude frommoment to moment or contain occasionalshocks. The severity of such complexmotion can be accumulated in a mannergiving appropriate weight to short periodsof high magnitude vibration or low periodsof low magnitude vibration. Differentmethods for calculating doses areused.
Measurement and evaluation of exposure Vibration measurements are made toprovide assistance for the development ofnew tools, to check these tools atpurchase, to verify maintenanceconditions, and to assess human exposureto vibration at workplace. Vibration-measuring equipmentgenerally consists of a transducer (usuallyan accelerometer), an amplifying deviceand amplitude indicator.
Whole-body vibrationshould be measured at theinterfaces between the bodyand the source of vibration. Forseated persons this involves theplacement of accelerometers onthe seat surface beneath theischial tuberosities of subject. Vibration is sometimesmeasured at the seat back or atfeet and hands.
The presence of otheradverse environmental factors,especially sitting posture,should be also be considered. It is assumed that for healtheffect estimation the totalexposure, rather than theaverage exposure, is important,and so a dose measure isappropriate.
Hand-transmittedvibration Vibration measurements should bemade on the tool handle or workpiececlose to the surface of the hand(s) wherethe vibration enters the body. In several (and the Bulgarian)standards hand-transmitted exposure isassesses in terms of four-hour and eight-hour energy-equivalent frequency-weighted acceleration calculated bymeans of equations.
Prevention The prevention of injuries or disorderscaused by vibration requires theimplementation of administrative, technicaland medical procedures. Appropriate adviceto manufacturers and users of vibrating toolsshould also be given. Administrative measures should includeadequate information and training to instructthe operators of vibrating machinery to adoptsafe and correct work practices. Sincecontinuous exposure is believed to increasevibration hazard, work schedules should bearranged to include rest periods.
HEALTH EFFECTS OFHAZARDS• Heat : Heat cramps, Heat exhaustion, Heat stroke, Heat syncope.• Cold : Chill blains, Frost bite, Hypothermia.• Humidity : Loss of body fluids, Dehydration.• Vibrations : Injury and inflammation of bones, joints and soft tissues.• Abnormal pressure : Pressure bends, Caissons disease, Air embolism.
Exposure Assessment at Work Place.1. Measurement of the level of hazard in REM (Relevant Exposure Medium).4. Measurement of Environmental factors I.e. temperature, humidity, & Air movement .3. Measurement of concentration of air borne contaminants ( Dust, Gases, Vapours & Particles .)4. Collection of Samples from other exposure media.
Exposure Assessment of Individual Worker1. Measurement of the concentration of harmful agents and their metabolites in biological samples of exposed worker ( Urine, Blood, Sputum & exhaled air).5. Assessment of intensity of biochemical & histological changes due to exposure.8. To carry out specialized investigation procedures ( biological Assays for responses to toxins , cytogenetic assays).
Health Hazards of Power plant workers• 1) Temperature : Workers are exposed to high degree of temperature at boiler rooms, turbine rooms and other work stations closer to boilers.• 2) Health effects : heat exhaustion due to loss of body fluids due to excessive sweating. Signs and symptoms :- Person feels weakness , Low body temperature, rapid pulse ,
• 3) Heat cramps : Due to loss of electrolytes from the body.• Signs and symptoms :- Painful cramps of calf muscles and abdominal muscles.• 4) Heat stroke : Due to exposure to excessive temperature.• Signs and symptoms :- high body temperature i.e. 108 F – 112F, increased frequency of urination, giddiness and loss of consciousness.• 5) Prevention and control : Proper ventilation and air conditioning of work place, Use of loose fitting clothes, provision of effervescent salt drinks to affected workers, Physical fitness of workers.
• Exposure to Noise : Exposure at boiler rooms , turbine rooms and other work stations. Type of noise :- a) steady wide band noise from continuously operating motors and machines. b) Impact noise from steam let outs.• Effects : social deafness :- person is habituated for loud talking could not appreciate whisper, hearing impairment, Occupational hearing loss, lack of concentration, annoyance, mental stress, hyper tension and peptic ulcer.
• Permissible level of noise for humans : 60 to 85 decibels or 185 Hertz .• Prevention and control : a) pre- placement and periodic medical examination of exposed workers. Use of protective devices such as ear muffs and ear plugs. Enclosing noise producing machines, reduction of noise by fitting mufflers and silencers to noisy machines. Sound proofing of work stations .
Coal and other Dusts• Exposure at coal handling plant, tippling stations, boiler rooms.• Respirable dust : dust particles of 0.3 to 5 microns in size.• Effects of dust inhalation : respiratory disorders like pneumoconiosis and progressive massive fibrosis of lungs.• Prevention and control : pre- placement and periodic medical examination of exposed workers.
• Proper ventilation of working place.• Good house keeping.• Use of personal protective devices such as masks and respirators by exposed workers.• Dust suppression measures like wet mopping of the floor, use of aerosol sprays.
Health effects of Radiation• Exposure at atomic power plants, near Nuclear Reactor, monitoring panels and other work stations.• Permissible level of radiation for humans : Five rems /year.• Effects of radiation : high degree of exposure due to accidental leakage of Nuclear Reactor causing radiation burns, acute radiation syndrome, Cancer of the skin, blood and bones, still births, intrauterine foetal death, abortions, shortening of life span.
Prevention and Control• Pre- placement and periodic medical checkup of workers.• Shielding the source of radiation : the source of X-rays, gamma rays and particulate radiation should be enclosed in radio protective material such as lead and concrete of suitable thickness.• Distance from the source of radiation : the controls should be located as far as possible or remotely operated.
Electromagnetic Field in the Power Plant• E.M.F. generates magnetic flux density at work place and near over head high tension power transmission lines, electrical sub stations and power generation plants.• Safety limits : maximum field strength should not exceed 10 Kv /M.• Recommended continuous exposure limit : 5 gauss with a maximum of 50 gauss for 2 hours.
Effects on HumanHealth• Sleep disturbances.• Headache.• Increased susceptibility to respiratory infections.• Increased risk of blood and brain cancer.
Prevention and Control• Insulation and shielding of machines.• Barrier operation of machines.• Continuous monitoring of E.M.F. level at work place.• Periodic medical checkup of exposed workers.
Hazards due to social factors• Workers are affected by industrial psychoses and neuroses.• Tensions and worries arising out of social environments in the industry i.e. poor intra and inter- personal relations , poor housing conditions, separation from family, job satisfaction and sickness absenteeism.• Sickness absenteeism is related to low productivity and low workers morale .• Level of absenteeism in the country : to the tune of 8 – 10 days / head /year.
Prevention & Control2. Periodic Medical Examination of Workers.4. Provision of good housing facility & Recreational activities.6. Good intra & inter personal relations in the factory.8. Health Education & Addiction control programmes in the Factory.