Hearing loss noise induced? A systematic review of Noise exposure in working life and health Arve Lie, NIOH, Oslo, Norway

Transcription

1 Hearing loss noise induced? A systematic review of Noise exposure in working life and health 2013 Arve Lie, NIOH, Oslo, Norway 1

2 Background The Petroleum Safety Authority and The Labour Inspection Authority need more knowledge on noise and health Noise exposure in working life and NIHL are regarded as an important Norwegian challenges Impulse noise as a cause of NIHL There are other medical conditions related to noise Hypertension, CVD, tinnitus, others Prevalences (self reported) Hearing loss or tinnitus (11%) * Work related hearing loss or tinnitus (3%)* Financial support of NOK from the Ministry of Labour *Survey of living conditions in Norway

3 Reported NIHL in mainland and offshore Norway 3

4 Requests How to identify noise susceptible workers Will NIHL speed up the age related hearing loss? What is the impact on hearing of impulse noise vs continuous noise exposure? How to differentiate between NIHL and presbycusis How to predict a future hearing loss based on the current noise exposure 4

5 Short answers How to identify noise susceptible workers Ask! (family) Will NIHL speed up the age related hearing loss? No What is the impact on hearing of impulse noise vs continuous noise exposure? Impulse noise is worse How to differentiate between NIHL and presbycusis Difficult How to predict a future hearing loss based on the current noise exposure ISO 1999:1990 Annex E 5

6 Normal hearing 3-6 khz, ISO 1999 Annex B 6

7 Noise exposure and expected hearing loss 3-6 khz, median value, ISO 1999: 1990 Annex E 7

8 The Norwegian classification system of hearing loss Class 1: HL of db at either of 3-6 khz or =20 db at all of 3,4 and 6 khz Class 2: HL of >40 db at either 3-6 khz and HL =< 20 db at 2 khz Class 3: As class 2, but hearing loss of 2 khz > 20 db 8

9 Hearing loss class 1-3 vs age and sex in a Norwegian population (HUNT) 9

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11 Occupations and NIHL The NIHL was considerable in developed countries in the 1960s and 1970s Norwegian population based survey from 1998 (HUNT) indicates a great reduction in NIHL =Danish and Swedish data International estimates that 7 21 % av HL is work related, most in developing countries (Nelson 2005, Dobie 2008) Norway= 3%? (unpublished findings from HUNT) Occupations at risk Military, agriculture, construction industry, offshore(?) (Nursery schools and musicians have a close to normal hearing) Published research and unpublished Norwegian audiometric data indicate that offshore workers may have a normal hearing 11

12 Genetics and hearing Genetics explain 40% av the variation in hearing loss No simple genetic test to identify suscceptibles to NIHL 12

13 Vibration and hearing Vibration + noise will probably increase the risk of NIHL It is, however, difficult to differentiate vibration from noise exposure Support from experimental studies 13

14 Chemicals and hearing Additive or synergistic effect on hearing at close to TLV exposure of styrene, CS 2, toluene, Pb, Hg and CO? Exposure to chemicals should be considered in the prevention of NIHL See: Johnson A-C, Morata TC. Arbete och Hälsa 142. Occupational exposure to chemicals and hearing impairment. Gothenburg: University of Gothenburg,

15 Leisure time noise and hearing NIHL and the use of firerarms is well documented Only minimal impact on hearing of other types of exposures (ex: PMPs) on a group level 15

16 Impulse noise and hearing Impulse noise is probably more deleterious than continuous noise at the same levels of exposure Mechanical and biochemical overload of the hair cells > 125 db? Experimental studies on animals Impulse noise adding factor of 5 db? (Denmark) 16

17 Hearing loss. Conclusion Most important factors Age (sex, genetics) Other important factors Occupational noise exposure, use of firearms, social group, ethnicity, ear diseases Less important? CVD, hypertension, cholesterol, diabetes, smoking, leasure time noise exposures, vibration, chemicals 17

18 Diagnostic guidelines for NIHL ACOEM (Kirchner 2012) Target: Hear cells in organ of Corti Symmetrical hearing loss Develops gradually Low risk at exposures < 85 db(a) Most of the hearing loss during the first years of exposure Starts at 3-6 khz and spreads to the low frequency and high frequency area Audiometric notch My comment: Common also among non-noise exposed (Oseih-Lah 2010, Nondahl 2009) A TTS of 10 db or more is a risk indicator of NIHL Tinnitus is also a risk indicator 18

19 Conclusion The occupational noise exposure and the prevalence of NIHL is declining in the western world Reported NIHL: Steady state in mainland Norway and increasing in the offshore sector Overdiagnosis in Norway? The hearing offshore may be quite normal Other noise related health effects Increases the risk of stress, irritabilty, occupational accidents, hypertension and CVD Noise reduction measures in working life is still important 19

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21 Noise the 3 db trading factor Measured in decibel Logarithmic scale 85 db in 8 hrs 88 db in 4 hrs 91 db in 2 hrs 94 db in 1 hr 97 db in ½ hr 100 db in 15 min. Etc. 21

22 Litterature search 22

23 The audiometric notch 23

24 Audiometric notches and exposure to noise in railway workers 24