Noise induced hearing loss
In this post, I’ll highlight just a few aspects of this occupational disease.
Legislation
In Romania, the health and safety aspects of occupational exposure to noise is regulated by Government’s Decision no.493, issued 12 April 2006 (link), which accurately translates Directive 2003/10/EC of the European Parliament and of the Council of 6 February 2003 on the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents - noise (link).
Noise exposure action and limit values
Lower exposure action value: 80 db(A)
Workers should be offered hearing protection.
Upper exposure action value: 85 db(A)
- Prevention program: technical and administrative measures to reduce noise below the 87 dB threshold
- Hearing protectors
- Medical surveillance
Noise exposure limit value: 87 db(A)
Special mentions on audiometry and hearing loss
Guidelines on performing pure tone air and bone conduction threshold audiometry, by the British Society of Audiology: http://www.thebsa.org.uk/docs/RecPro/PTA.pdf
Audiometry is afterall a subjective assessment. Even if a trained audiometric technician, audiologist or physician can do a lot to obtain accurate results, the level of patient intelligence, cooperation, or good will is still of paramount importance. An electrophysiologic measurement such as brainstem auditory evoked potentials (BAEPs, also known as auditory brainstem response, ABR) can help in determining the general degree of hearing loss without requiring a subjective response from the individual.
Interpretation of periodic audiograms should take in account age correction.
There may be asymmetric occupational noise induced hearing loss in certain cases, such as truck drivers exposed to greater noise to the ear closer to the engine exhaust.
Noise induced hearing loss may be accelerated by synergic risk factors such as cigarette smoking, noisy hobbies (recreational shooting, listening to loud music, motorcycle riding, metalworking), exposure to industrial organic solvents.
NIHL treatment
First measure to be taken is obviously discontinuing worker’s exposure to noise, to prevent further damage to the internal ear.
As for the medical treatment, although no specific treatment is available to cure, as the sensorineural hearing impairment is mainly irreversible, there are some non-specific substances which can be of help to alleviate accompanying tinnitus and to some small degree the hearing loss: vitamins, antioxidants, vasodilators.
Drugs that are currently used to this purpose are:
- Ginkgo Biloba: 2×120mg/day [commercial products Bilobil, Tanakan]
- B Vitamins (B-12 and B-3 in particular) –over 25 µg of B-12, over 25 mg for the rest daily for 6 months [commercial product Mega B Complex]
- N-acetyl cysteine: 3×200mg/day [commercial product ACC]
- Vinpocetine: 3×10mg/day [commercial product Cavinton]
There are many other suplements to help with both tinnitus and hearing loss: vitamins A, C, E, zinc, magnesium, choline, melatonin, ipriflavone, arginine, resveratrol, lecithin, L carnitine, co-enzyme q10, alpha lipoic acid, Chinese herbs, garlic. Eliminating coffeine intake could help with tinnitus in certain patients.
For instance, a March 28, 2007 in press release, University of Michigan researchers report that in a new study in animals a combination of high doses of vitamins A, C, and E and magnesium, taken one hour before noise exposure and continued as a once-daily treatment for five days, was very effective at preventing permanent noise-induced hearing loss.
This is an interesting observation and I think it could have immediate practical applications in decreasing workers sensitivity to noise in industrial settings.
A smart tool converting pascals into decibels