ABNORMAL NORMAL 10 6

1. SPINAL RADIOGRAM ABNORMAL NORMAL 106

2. OCCUPATIONAL HEARING LOSS BY: MORTEZA DAVOODI M.D.

3. INTRODUCTION • Despite widespread institution of hearing conservation programs in noisy industries, NIHL is currently one of the most common occupational diseases. • Although NIHL is permanent, irreversible, and prevalent, it is preventable. • In addition to the major problem of NIHL, the ear is susceptible to other environmental factors.

4. Safe noise exposure • It is impossible to establish to any clear-cut distinction between “safe” and “unsafe” noise exposure. • Because of the normal variation in susceptibility between individuals, it is not possible scientifically to set a realistic standard for exposure to noise that will protect everyone who is exposed. • Generally, limits are set with the intention of protecting 90% or more of an exposed population.

5. How hearing maybe impaired • Infection of the ear • Infection of external ear • Chronic infection of the middle ear • Obstruction or injury by physical agents • Impacted cerumen • Foreign bodies • Trauma to the ear (Slag burns) • A sudden, intense pressure wave • Prolonged noise exposure • Barotrauma (aerotitis) • Middle ear damage due to rapid changes in altitude • Radiation induced damage • Radiation to head and neck

6. How hearing maybe impaired • Toxic agents • Quinine and its derivatives • Organic solvents, heavy metals, CO, NSAIDS, cisplatin, furosemide, Tobacco (nicotine) and aspirine (salicylates) are possible causes in hypersusceptible patients. • Antibiotics : • streptomycin, neomycin, kanamycin, paromomycin, rifampin, aminoglycosides , vancomycin, • symmetrical progressive high frequency SNHL • Diseases : • Meningitis, tumors, mumps, measles, scarlet fever, diphtheria, respiratory infections

7. Differential diagnosis of SNHL(Nonoccupational Hearing Loss) • Presbycusis • Gradual symmetrical progressive high frequency SNHL • Hereditary hearing impairment (HHI): • Is distinguished by a family history and early age at onset. e.g; otosclerosis (Can be conductive, mixed, or SNHL) • Metabolic disorders • DM, Thyroid dysfunction, renal failure, autoimmune disease, hyper-lipidemia and hyper-cholesterolemia • SNHL that is bi-lateral, progressive, and high frequency

8. Differential diagnosis of SNHL(Nonoccupational Hearing Loss) • Sudden SNHL • Sudden onset usually within 1 or 2 hours in the absence of precipitating factors • Almost always unilateral • Can be exhibited at low frequencies, flat or high frequencies hearing loss. • The degree of HL can be from mild to severe . • Infectious origin: • Bacteria or virus infections including meningitis and encephalitis. • HL can be unilateral, but is usually bilateral. • Mumps may cause a rather severe, most typically unilateral SNHL

9. Differential diagnosis of SNHL(Nonoccupational Hearing Loss) • CNS disease: • Cerebellopontine angle tumors especially acoustic neuroma maybe present progressive SNHL that is unilateral. • MS : sudden unilateral hearing loss that typically recovers to some degree. • Menieres disease • Fluctuating low frequency or flatunilateral SNHL, fullness or pressure in the affected ear, tinnitus and episodic disabling vertigo

10. Exteraauditory effects of noise • Alterations in blood pressure • Due to release of adrenocortical hormones and sympathomimetic mediators • Adverse influences on existing illnesses • Hyperlipoproteinemia and diabetes • Pregnancy and noise: • It is unclear what effect exposure to noise during pregnancy may have on the unborn child, in terms of increased rate of miscarriage, low birth-weight, or prematurity.

12. CLINICAL EVALUATION OF HEARING LOSS • Detailed work and health history • Age • Family history • Ototoxic chemicals and drugs • Presence of tinnitus • Noise exposure (occupational and non occup.) • Hearing loss onset, progression, fluctuation and symmetry. • the use of hearing protection devices • Radiation to the head and neck • Head injury • CNS infections • Complete otologic examination, • Audiologic examination

13. Importance of the history • A careful evaluation of the workers medical, occupational, and family history is probably the most important step in the diagnostic procedure.

14. The following factors regarding past and present occupations should be evaluated • Job titles • Type of work performed • Duration of each type of activity • Dates of employment for each job activity • Condition of PPE used and frequency and duration of periods of use • Nature of noise exposure include frequency, intensity and average duration

15. Estimation of noise exposure • It is estimated that workers in an 85 dB environment will have to speak loudly, • While those in 85-90 dB will have to shout to communicate at arm length. • As the surrounding noise reaches 95 db , communications only occurs with shouting, even if the workers stand next to each other.

16. NOISE INDUCED HEARING LOSS • Acoustic trauma • SNHL • CHL • Mixed • Tinnitus • Can more severe than NIHL, especially in the low and middle frequencies. • Disequilibrium • In addition to immediate hearing loss, affected individuals may also complain of vertigo, tinnitus and pain. • The injury may be unilateral or bilateral, depending upon the direction of blast. • SNHL from acoustic trauma may exhibit some recovery from initial levels; patient need to be followed for 4 to 6 month. • Temporary threshold shift(TTS) • Permanent threshold shift (PTS)

17. Chronic NIHL • Defining Characteristics

18. Audiometric test rooms • TABLE D-1 - MAXIMUM ALLOWABLE OCTAVE-BAND SOUND PRESSURE LEVELS FOR AUDIOMETRIC TEST ROOMS ________________________________________ • Octave-band center • frequency (Hz)............... 500 1000 2000 4000 8000 • Sound pressure level (dB) ... 40 40 47 57 62 _______________________________________________________________

19. Factors Affecting NIHL • Noise Intensity or Sound Pressure • Frequency or Pitch • Length of Daily Exposure • Duration of Exposure in Years • Individual Susceptibility • Other Factors (disease, genetics, lifestyle, age, etc.)

20. Come Again Beg Pardon You Say Something? Excuse Me Say What Speak Up Huh? NOISE INDUCED HEARING LOSS • Clinical presentation of NIHL: • Irreversible and usually bilaterally symmetric SNHL, • High frequency hearing loss in the region around 4000 Hz, with recovery at higher frequencies. • Often accompanied by high frequency ringing tinnitus. • Persons with NIHL typically complain of being able to hear but not understand speech.

21. Scale of Hearing Impairment Threshold (dB HL)Degrees of Impairment -10 – 25 Within normal limits 26 – 40 Mild HL 41 – 55 Moderate HL 56 – 70 Moderate to severe HL 71 – 90 Severe HL > 90 Profound HL

25. There are a number of indicators that will suggest the need for careful consideration of causes other than noise • CHL • MIXED hearing loss • Indicates that exposure to noise is not the only cause • Inconsistent responses during different tests • Indicates the possibility of malingering or functional loss • If SRT is 15dB or more than the average of the pure tone levels at 500, 1000, and 2000 Hz, a psychogenic loss or malingering should be suspected. • A pronounced loss in one ear

26. No exposure to continuous, intermittent, or impact noise of a peak C-weighted level of 140 dB shall occur. No exposure shall exceed a time weighted average of 115 dBA for continuous noise. Noise Exposures

27. Asymmetric hearing loss • Greater noise exposure in one ear • Most indoor factory environment, are highly reverberant so that one ear rarely receives significantly more noise than the other. • Non occupational noise sources (Hunters). • Menieres disease • Sudden idiopathic SNHL • Acoustic neuromas

28. Audiometric surveillance for NIHL • The OSHA hearing conservation program mandates audiometric surveillance of workers who are exposed to noise levels equal to or exceeding 85 db on an 8h TWA. (when beginning work and then annually). • This routine audiometric testing can be performed by an audiometric technician who has completed the necessary education and training requirements. • For the base line audiogram, the individual should not have been exposed to loud noise for at least 16h prior to testing, to avoid TTS. • Subsequent surveillance tests do not require noise free interval. • OSHA regulations require testing at the frequencies of 500, 1000, 2000, 3000, 4000, 6000 and 8000 Hz.

29. Audiometric surveillance for NIHL • The results of the periodic audiogram should be compared to thebase line. If the employees test shows a shift from base line in excess of 10 db for the average hearing level at 2000, 3000, and 4000 Hz in either ear (STS) a retest may be performed within 30 days. If the shift persists, the employee must be informed in writing within 21 days, fitted with hearing protectors if not already using them, refitted and counseled if already using protectors, and referred for a clinical audiologic evaluation and/or otologic evaluation if appropriate.

33. Calculations and Application of Age Corrections to Audiograms(This appendix is non-mandatory ) • In determining whether a standard threshold shift (STS) has occurred, allowance may be made for the contribution of aging to the change in hearing level by adjusting the most recent audiogram. If the employer chooses to adjust the audiogram, the employer shall follow the procedure described below. This procedure and the age correction tables were developed by the National Institute for Occupational Safety and Health in a criteria document.

34. Calculations and Application of Age Corrections to Audiograms(This appendix is non-mandatory ) • I. Determine from Tables F–1 or F–2 the age correction values for the employee by: • A. Finding the age at which the most recent audiogram was taken and recording the corresponding values of age corrections at 1000 Hz through 6000 Hz; • B. Finding the age at which the baseline audiogram was taken and recording the corresponding values of age corrections at 1000 Hz through 6000 Hz. • II. Subtract the values found in step (I)(B) from the value found in step (I)(A). • III. The differences calculated in step (II) represented that portion of the change in hearing that may be due to aging.

35. Example: Employee is a 32-year-old male. The audiometric history for his right ear is shown in decibels below.

36. Table F–1—Age Correction Values in Decibels for Males

37. Table F–1—Age Correction Values in Decibels for Males

38. Go to Table F–1 and find theage correction values (in dB) for 4000 Hz at age 27 and age 32.

39. CRITERIA FOR REFERAL OF INDIVIDUALS TO AN OTOLARYNGOLOGIST • Baseline audiogram • Average hearing levels at 500, 1000, 2000, and 3000 Hz greater than 25 db in either ear. • Difference in average hearing level between the better and poorer ears of more than 15db at 500, 1000, and 2000 Hz, or more than 30 db at 3000, 4000, and 6000 Hz. • Periodic audiograms • Change for the worse in average hearing level in either ear compared to the base line audiogram of more than 15db at 500, 1000, and 2000, or more than 20db at 3000, 4000, and 6000 Hz. • Audiometric findings are inconsistent

40. CRITERIA FOR REFERAL OF INDIVIDUALS TO AN OTOLARYNGOLOGIST • Ear pain • Drainage • Dizziness • Severe persistent tinnitus • Fluctuating or rapidly progressive hearing loss • Presence of accumulated cerumen or other foreign materials within the ear canal.

41. PREVENTION • A hearing conservation program has consisted of at least seven identifiable elements: • Monitoring hearing hazards • Engineering and administrative controls • Audiometric evaluation • Personal hearing protective devices • Education and motivation • Record keeping • Program evaluation “By showing the worker his personal record of hearing sensitivity, the nurse or physician has a most effective device for the promotion of hearing protection.”

42. HEARING PROTECTIVE DEVICES (HPDs) • What is the best hearing protector? The answer is: “the best protector is the one properly fitted and the one you wear.”

43. HEARING PROTECTIVE DEVICES (HPDs)

44. HEARING PROTECTIVE DEVICES (HPDs) • Earplugs • Custom molded • Provide satisfactory attenuation if properly fitted. • Require cleaning and maintenance • Offer few advantages over the less expensive foam plugs. • Expandable foam plug • Are usually quite comfortable to wear and they also can provide high noise attenuation values.

45. Proper Use of Hearing Protection Earplugs must be properly inserted source: http://www.cdc.gov/niosh/mining/topics/hearingloss/earplug.htm • 1. Rollthe earplug up into a small, thin "snake" with your fingers. You can use one or both hands. • 2. Pullthe top of your ear up and back with your opposite hand to straighten out your ear canal. The rolled-up earplug should slide right in. • 3. Holdthe earplug in with your finger. Count to 20 or 30 out loud while waiting for the plug to expand and fill the ear canal. Your voice will sound muffled when the plug has made a good seal. • Check the fitwhen you're all done. Most of the foam body of the earplug should be within the ear canal. Try cupping your hands tightly over your ears. If sounds are much more muffled with your hands in place, the earplug may not be sealing properly. Take the earplug out and try again. Illustrations and Photo courtesy of NIOSH

46. HEARING PROTECTIVE DEVICES (HPDs) • Earmuffs • The cup material should be rigid and of large volume so as to provide the best low frequency attenuation levels. • Since earmuffs do not require insertion into the ear canal, they are more hygienic and less likely to cause external ear canal infections. • They are easier to remove and replace in conditions of intermittent noise exposure. • The singular disadvantage to these devices is that they are cumbersome and bulky. • In conditions of extremely high noise, it may be necessary to wear both earplugs and earmuffs together.

47. Noise reduction ratings • NRRs are based on laboratory attenuation data and achieved under ideal conditions. • Actual noise reduction achieved under field conditions using any HPDs will be much lower than the assigned NRR.

48. Noise reduction ratings • Weighting Scale Adjustment: • If workplace noise levels are determined using the “C” scale (dBC) on the monitoring instrumentation, the assigned NRR may be subtracted directly from the actual measured TWA noise levels • If workplace noise levels are determined using the “A” scale (dBA) on the monitoring instrumentation, the assigned NRR must be reduced by 7db before being subtracted from the actual measured TWA noise levels

49. Noise reduction ratings • 50% Derating: • In order to more accurately predict the NRR of HPDs during actual use, a 50% derating of the assigned NRR (after weighting scale adjustment) should be applied to determined its “relative performance”. • OSHA does not require the 50% derating.

50. Derate by Type • Derate the hearing protector attenuation by type using the following requirements: • A. Subtract 7 dB from the published Noise Reduction Rating (NRR). • B. Reduce the resulting amount by: • 1. 20% for earmuffs, • 2. 40% for form-able earplugs, or • 3. 60% for all other earplugs.