Aviation Fuel—Fuel for Hearing Loss

It has long been common knowledge that working around aircraft jet engines can damage your hearing. But new research indicates that the danger is not just from exposure to noise alone.

These recent findings not only throw new light on the ways that environmental hazards in the workplace can impact on your hearing but also redefine the very nature of hearing loss itself.

Noise isn’t the only hearing hazard

A number of studies have suggested there is a link between exposure to fuel and hearing loss. A 2005 study of military workers found that three years of exposure to jet fuel raised the chances of hearing loss to 70%[1]. But until now it has been difficult to isolate the effect of the fuel from that of noise alone.

However, recent research[2] at Lorma Linda University has identified a clear connection between exposure to jet aircraft fuel (jp-8) and hearing loss in rats. In this study rats exposed to noise and jet fuel suffered a much greater hearing loss than those animals exposed to noise alone.

Jp-8 is a fuel designed for use in military aircraft but it is very similar to the fuel used in domestic airlines and this raises concerns about the hearing health of not only pilots, engineers, other airport staff and even frequent flyers but also for workers in the hydrocarbon industry such as delivery truck drivers and gas station attendants.

In fact, many fuels contain aromatic hydrocarbons such as toluene, ethyl benzene, and styrene that share similarly ototoxic properties. According to an earlier Lorma Linda University study, “exposure to these agents over a period generally of 4–16 weeks yields a persistent auditory impairment that is particularly severe at mid-frequencies.”[3]

This is hearing loss but not as we know it

Although these aromatic compounds are known to cause the death of hair cells it is evident that this is not the whole picture. One of the interesting issues to arise out of this research is that ototoxic chemicals in the fuel clearly inhibit the brain stem’s ability to process sound rather than simply cause a physical hearing loss.

Testing showed that the subjects were able to physically hear the sounds but the brain was unable to decipher them—a situation somewhat similar to dyslexia but for the ears. Before dyslexia was recognised many people with dyslexia suffered considerable learning difficulties, stress and isolation and we may be seeing something similar with this kind of undiagnosed and unrecognised hearing loss.

According to the study’s author, “It is possible that a large population of military personnel who are suffering from the effects of jet fuel exposure may be misidentified because they would exhibit normal hearing thresholds but harbor a “hidden” brainstem dysfunction.”[4] This issue may, of course, extend far beyond the military and will probably apply to anyone handling fuel on a regular basis.

These findings raise a number of challenges around hearing safety. Researchers don’t know exactly how jp-8 is inducing hearing loss but scientists suspect that the ototoxic chemicals present in the fuel may depress levels of the crucial antioxidant Glutathione (GSH) thereby increasing the body’s susceptibility to noise induced damage in the hearing cells.

Furthermore, these chemicals are having a detrimental effect on the brain’s ability to process sound at exposure levels far below what was considered to be safe.

Although considerably more research is needed at this point to fill in the gaps in our knowledge it is clear that we need to be cautious when handling fuel of any type.

What can I do to protect my hearing from this threat?

When handling fuel, especially in confined spaces, make sure you wear appropriate protection such as respirators and gloves and avoid inhaling fumes. There is evidence that ototoxic chemicals may also have an effect through the skin so be careful to avoid any accidental splashes making contact with exposed skin.

In your workplace you may need to take an active role to ensure that this issue is treated as a health and safety issue. It is important to educate your employers and fellow employees about the dangers of fuel but your hearing is a precious gift so it is worth taking these steps to protect it.

Come and visit us at your local House of Hearing clinic– we can advise you on all aspects of hearing health and our friendly, expert service is second to none.

[1] http://www.cdc.gov/niosh/nioshtic-2/20037378.html

[2] http://www.research.va.gov/currents/spring2014/spring2014-11.cfm

[3] http://toxsci.oxfordjournals.org/content/98/2/510.full


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