/ Evaluation of the Increased Accident Risk From Workplace Noise Esko Toppila(1), Rauno Pääkkönen(1), Ilmari Pyykkö(2) 1=Finnish Instutute of Occupational Health 2=University of Tampere

/ Noise directive NOISE -duration - level - intermittency -impulsivness Accident risk Hearing loss - Ototoxic substances - Vestibulotoxic substances ? Individual susceptibility

/ Specific accident risk related statements 1.The indirect effects on workers' health and safety resulting from interactions between noise and warning signals or other sounds have to be observed in order to reduce the risk of accidents 2.In exceptional situations where, because of the nature of the work, the full and proper use of individual hearing protectors would be likely to cause greater risk to health or safety than not using such protectors

/ What we know about noise and accidents ? Risk factors in a shipyard (Moll van Charante, Mulder, 1990) –Noise > 82 dB –Noise and hearing loss in 43% of accidents Accident reports in Finland –Railroad worker with hearing handicap died because of not hearing an approaching train (2) Similar event with 4 deads in United Kingdom –Radio equipped hearing protectors and ice hockey game (2) Morata & al, 2005 –Hearing warning signals and loosing direction information is complained by workers with hearing handicap or using HPE Germany –Traffic noise and limitations for attenuation of HPD

/ Girard &al, workers, five year follow-up

/ Origin of interaction between noise and accident risk Noise –Reduced speech intelligibility –Possibility of hearing warning sounds –Reduced capacity to localize the sounds Hearing handicap –Increases the risk Hearing protectors –cause on artificial hearing loss -> possible increase of accident risk

/ How to proceed ? Sound Speech Hearing Loss of localisaton intelligibility warnings concentration Risk assessment Evaluation of the characteristic of hearing handicap Corrective actions

/ Risk assessment Sound direction –Moving vehicles? –Possibility to collide ? –Yes -> sound location must be evaluated Speech intelligibility –Accidents possible due to missunderstanding –Yes -> Evaluate speech intelligibility Warning signals present –Evaluate the audibility of warning signas using ISO 7731 –Correct with hearing loss and attenuation of HPDs Loss of concentration –Consequences of wrong manoeuvring ?

/ Why correct the audibility of warning signals? Speech consonants Speech Consonant Musicians HPD Normal plug/muffs Hearing loss

/ Evaluation of Speech intelligibility using ANSI S3.5 Frequency (Hz)Speech levelNoise level Hearing loss +HPD atten SII= SII depends on speech intelligibility requirements Easy speech SII >0.3 Complicated speech SII >0.7

/ Comparison of audiogram (mean of kHz) and self-evaluated hearing Normal hearing Mild hearing Moderate loss hearing loss Mean threshold shift at speech frequencies( kHz) Not enough if elevated accident risk

/ Practical example: railway yard Noise sourceNoise characteristicsMax level (dB) Locomotive breakshigh frequency noise >2.5 kHz over 115 dB Wheel noise in turnings high frequency noise >2.5 kHz over 115 dB Typhoons high freq.0.8 and 1.6 kHzover 115 dB Typhoons low freq0. 5 kHzover 115 dB Pressured air4 -8 kHz115 dB Average noise level 85 dB -> use of HPD mandatory Accident risk caused by moving trains

/ Requirement for hearing in railway yard work Condition1 kHz2 kHz3 kHz4 kHz When work starts *20 25 When working **25 Conditionspeech freqs. (0.5- 2kHz 3-4 kHz When entering to work 2o40 When working*4060 *Speech must be understood from 2-4 m distance * or hears whisper from 5 m with both ears ** or hears conversation from 5 m with both ears Railway Medical Services recommendation Finnish railway requirements

/ Problems and solution Normal hearing inspection rate is every 3 years –What to do with those whose hearing is near to the limit ? Increase the inspection rate -> expensive HPDs increase the effect of hearing loss -> what should be the requirement for hearing when wearing HPDs Solution: Use of level dependent HPDs

/ Advantages of the solution The sound exposure of railroad yard men could be reduced below 85 dB without compromising the safety of workers No more discomfort due to the high noise levels When using hearing protectors, the hearing level was always better than without protectors. Thus the requirement of hearing was always fulfilled at work and very frequent hearing tests were not anymore mandatory The overall costs of the solution are lower than the cost of the previous solution: The price of electronic muffs was lower than the cost of frequent visits to otologists

/ Conclusions Noise causes an increased accident risk The risk is elevated for those with hearing handicap –HPDs may still increase the risk Electronic hearing provide a good mean for reducing the accident risk for workers with hearing handicap Evaluation of increased accident risk is difficult –Hearing handicap and working conditions must be analyzed in parallel