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27 September 1999
Dr. Ricardo Martinez, Director
National Highway Traffic Safety Administration
400 7th Avenue SW
Washington DC 20590
Subject: Consideration of the Effects of Airbag Deployment on Hearing and Balance
Dear Dr. Martinez:
The Acoustical Society of America has become aware of the potential deleterious effects to the health and safety of hearing and balance due to the deployment of air bags. We realize airbags save lives in many automobile accidents, but we are writing to ensure that you are also aware of studies indicating that airbags cause some individuals to sustain permanent injuries to their hearing and balance capabilities. The Society is, therefore, asking NHTSA to consider amending its current position regarding airbags to reflect new data indicating the association of hearing and balance disabilities with airbag deployment.
The Acoustical Society of America, a scientific organization which began in 1929, has more than 7,000 members worldwide. We host two internationally-attended meetings per year, with participation from approximately 2,000 attendees. At our 136th Meeting at Norfolk, Virginia last year, we hosted a special session on the Acoustical Effects of Airbag Deployment. A brief summary of the presentations at this session indicates;
I. More than 100 cases of individuals suffering permanent hearing loss, tinnitus, hyperacusis (painful over-sensitivity to noise), and disequilibrium (balance disorders) are in the literature. This is especially noteworthy since there are now no formal means of reporting auditory injuries from airbag deployments. Also there are no concerted research efforts in this field at the present time.
II. Theoretical predictions based on a mathematical model of auditory hazard, and confirmed by animal and human experiments, demonstrate it is likely that more than 90% of individuals will be at risk for hearing or balance disorders when current airbags are deployed under conditions involving open windows, unanticipated deployments, and heads turned so that an ear faces the airbag. Under the best cases, the risk ranges from less than 1% to a few percent of individuals who will be affected. The theory also suggests that auditory and balance hazards can be materially reduced while maintaining the other potential safety benefits of airbag performance.
III. Data suggest that conclusions of the "National Conference on Medical Indications for Air Bag Disconnection" (July, 1997) are not correct in stating that: a) hearing loss has not occurred with airbag deployment, b) tinnitus is not associated with hearing loss, and c) individuals with existing conditions of hyperacusis or tinnitus are not at greater risk for additional difficulties following airbag deployment.
Airbag deployment poses a risk to the hearing and balance capabilities in some individuals. We therefore would like to support recommendations previously provided to you by the American Academy of Otolaryngology - Head and Neck Surgery (AAO/HNS) and the National Hearing Conservation Association (NHCA), suggesting that NHTSA consider adopting policies to cover warning labels and airbag deactivation options for drivers and passengers.
Given the above information, we believe your policies should be updated to consider:
1. Including scientific evidence which demonstrates airbag deployment can result in hearing loss, tinnitus, hyperacusis and balance disorders for some individuals under certain deployment situations.
2. Developing a systematic data reporting and analysis method to quantify the risk of auditory injury along with the usual benefits of avoiding physical injury in order that society can accurately assess the risk/benefit associated with airbag deployment.
3. Providing an education program describing the potential damage to hearing and balance capabilities associated with the 160 to 170 dB impulse sound generated by airbag deployment.
4. Supporting the need for study of acoustical criteria for deactivation options in airbag design (such as now available through Rule 49 CFR Parts 595 and 571).
5. Modifying present airbag systems to include warning label that accurately state the liabilities associated with airbag deployment, and consideration of deactivation in new designs.
The Acoustical Society of America will continue to sponsor technical sessions reporting the newest data on hearing and balance disorders resulting from airbag deployment, and encourage researchers to develop designs that minimize potential health hazards. We will continue to provide you with updates regarding the scientific progress made in these areas and invite you to co-host such sessions with us in the future. In the meantime, we hope you will consider the technical results mentioned and the five policy recommendations we have provided above, and would be happy to provide acoustical information for your web page on airbags. We would appreciate receiving a response regarding the above requests and offers. In addition we hope to have an opportunity to meet with you and your staff to review this information we have presented. Please feel free to contact our Executive Director, Charles Schmid, at (516-576-2360), if you have further questions or to arrange a meeting to discuss these issues.
Patricia K. Kuhl, President
Acoustical Society of America