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Personal Music Players & Hearing

11. Conclusions on health risks of personal music players

  • 11.1 Are users of personal music players exceeding current sound exposure limits?
  • 11.2 What are the risks of prolonged exposure to loud sounds from personal music players?
  • 11.3 Under what condition can listening to personal music players be considered safe?
  • 11.4 What further research is needed?

11.1 Are users of personal music players exceeding current sound exposure limits?

The SCENIHR opinion states:

4. OPINION

The SCENIHR was asked to assess, in the light of current scientific data and knowledge:

  1. Whether the exposure to noise* from devices like personal music players and mobile phones with this function, at levels corresponding to current permissible noise emissions may cause quantifiable health risks, in particular hearing loss and/or hearing impairment to the user, and to specify the relevant outcomes;
  2. In case health risks are identified, the SCENIHR is asked:
    1. to identify the level of noise emission safeguarding the health of citizens, taking into account the intensity, length and number of exposures to users of personal music players and mobile phones with the same function and
    2. to identify priority issues for further research.

Background.

The increase in unit sales of portable music players (PMP) including MP3 playback function has been phenomenal since their introduction in the EU around four years ago. Estimated units sales range between 184‑246 million for all portable audio devices and range between 124‑165 million for MP3 players. There was a marked increase in overall portable audio devices sales in 2005 and sales were maintained in the following years with more than 50 million devices being sold per year by 2007. Mobile phones are sold by similar numbers of units every year. However, at present the availability of the MP3 functionality is not widespread in these handsets (maybe ten percent) while their frequency of use remains as yet unknown.

Although the data for the portable audio market are accessible, there are no demographics easily available on these sales, nor any information on how many devices an individual may buy over a given time period, how long they last before being discarded and how long and in what situations they are used. Thus, it is hard to estimate the proportion of the population that has access to portable audio or to MP3 players, and how many use them on daily basis. However, it may be estimated on rather conservative way that in EU the number of users of devices like personal music players and mobile phones with this function, are in tens of millions daily.

The digital formats of sound recording and reproduction currently available (e.g. MP3) make it possible to reach high levels of sound output with virtually no distortion, that could possibly cause a risk to human hearing originating from the inappropriate use of portable music players.

As shown by many studies, noise-induced hearing loss (NIHL) is a function of sound level and duration of exposure. The fundamental unit of noise exposure measurement is A-weighted decibel [dB(A)]. This unit corresponds well with the physiological sensitivity of human ear and it has been generally adopted in scientific literature.

Noise at Work Regulations (Directive 2003/10/EC, came into force in 2006) establish a minimal action level of hearing protection to the limit of 80dB(A) for an 8 hour working day (or 40 hour working week) assuming that below this level the risk to hearing is negligible. The exposure to sound at the level exceeding 80 dB(A) is considered a risk if it continues at that level for 8 hours a day, five days a week for tens of years. The 8-hour equivalent level (Lequ,8h) is a widely used measure for the risk of hearing damage in industry. On the basis of equal energy, level and time of exposure may be traded with halving of time of exposure with every doubling in level (+3dB). Using the equal energy basis it may be deduced that the exposure to 80 dB(A) for 40 hours would be equivalent to the exposure to 83 dB(A) for 20 hours and 89 dB(A) for 5 hours per week. However, because the model was built on the basis of tens of years of exposure, such calculation for exposures of short length should be interpreted with caution.

Although all the above regulations and limits apply to the workplace, the fact that they rely on the exposure level and duration means that they can equally be applied to other situations where sound has a detrimental effect such as that from personal music players (PMPs); whether use in workplace, or under leisure situations.

The free-field equivalent sound pressure levels measured at maximum volume control setting of PMPs range around 80-115 dB(A), across different devices. Differences between different types of ear-phones may modify the level by up to 7-9 dB. In the worst case scenario, it is possible to estimate maximum levels of about 120 dB(A). The hazard to hearing from listening to the music at such levels might be extremely high, as it is considered that levels exceeding 80 dB(A) may pose a risk.

Question 1:

SCENIHR is asked whether the exposure to noise from devices like personal music players and mobile phones with this function, at levels corresponding to current permissible noise emissions may cause quantifiable health risks, in particular hearing loss and/or hearing impairment to the user, and to specify the relevant outcome.

Answer:

It is estimated that the number of young people with social noise exposure has tripled (to around 19%) since the early 1980s, whilst occupational noise has decreased. It should be recognised that exposure to different types of noise and sounds can have cumulative effects in hearing impairment.

There is evidence in the scientific literature that the levels of exposure to sounds from using PMP on regular basis range widely from 60 dB(A) to 120 dB(A) among PMP users, but a vast majority of listeners use it at a level below 80-85 dB(A). The type of music and environment may influence exposure levels. The mean weekly exposure time spent on listening to music ranges from below 1 to 14 hours, and is typically longer for men than for women. It has been estimated that the average, A-weighted, eight hour equivalent sound exposures levels (referred to “Noise at Work Regulations”) from PMPs range from 75 to 85 dB(A), producing minimal risk of hearing impairment for the majority of PMP users.

However, a certain proportion of users are at a higher risk due to the levels patterns and duration of their listening preferences. Considering the daily (or weekly) time spent on listening to music through personal music players and the typical volume control settings, approximately 5% to 10% of the listeners are at risk of developing permanent hearing loss after 5 or more years of exposure – the best estimate available on the limited data (which may be an underestimate based on unpublished information) suggests that this may be between 2.5 and 10 million people in EU. Those are the individuals listening to music over 1 hour a day at high volume control setting.

* Please note that throughout this opinion, the term ‘noise’ is used consistently in the context of all disease and malfunction patterns, while the word ‘sound’ is used consequently to clarify that the concern is the voluntary listener of personal music players and not the observer of the listening situation. For details see paragraph 3.3.1]

Source & ©: SCENIHR,  Potential health risks of exposure to noise from personal music players and mobile phones including a music playing function (2008), Section 4. Opinion, Background, Answer to question 1.

Note: The European Directive 2003/10/EC on the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (noise) is available at:
 http://eur-lex.europa.eu/en/

11.2 What are the risks of prolonged exposure to loud sounds from personal music players?

The SCENIHR opinion states:

Literature data indicate that the consequences of prolonged exposure to loud sounds from the PMPs may possibly result in:

  • TTS: Temporary (hearing) threshold shift
  • PTS: Permanent (hearing) threshold shift
  • Tinnitus: Ringing in the Ears
  • Poor Speech Communication in Noisy Conditions
  • Change in behaviour with the environment (pedestrian/driving behaviour while listening, acoustic isolation during use)
  • Non-auditory effects

It has been shown that acute exposure to music listened through PMPs at the level between 94-104 dB of sound pressure level (dB SPL) leads to around 10dB of temporary threshold shift, but in sensitive individuals may cause up to 30dB shift. Although the data are very limited they confirm that reversible hearing impairment may occur in some individuals. Clearly 30 dB temporary threshold shift could affect performance on listening-sensitive tasks such as driving or communicating.

There are major discrepancies between the results of the studies on permanent noise-induced hearing loss (NIHL) in PMP users. Both, positive and negative studies have been published. The discrepancies could arise from different study designs and methodology. Most of these studies showed none or only small permanent effect of using PMP on hearing in the majority of users, if short term consequences were assessed with audiometric hearing threshold. It is difficult to conclude with the available data whether the exposure to PMP music in teenage may influence hearing in older age. This is due to a lack of long-term studies using sensitive measures of hearing impairment.

A few studies indicate that tinnitus and hearing fatigue occur more frequently in teenagers exposed to music, including PMP users, than in those unexposed.

Harmful, lasting and irreversible non-auditory effects of excessive listening to PMP can be expected in three areas: (1) cardiovascular effects, (2) cognition and (3) distraction and masking effects. It was shown that noise exposure to 66 dB(A) for 15 min, and down to 55 dB(A) for aircraft noise may cause impaired learning and memory of a text, and we assume the same to be true for music from PMPs.

Prolonged exposure to chronic aircraft noise has been shown to impair cognition in children, but there is also one indication that children may recover from the noise induced cognitive deficit when the noise exposure stops. To what extent this recovery is dependent upon the age of the children in question and the accompanying general growth in cognitive development, we do not know. Thus, we can not say with any precision across age groups how long a noise induced cognitive deficit will last when the noise exposure has ceased.

As regards the physiological non-auditory effects of listening to PMPs, increased blood pressure and ischemic heart disease are of principal relevance. However, at present, there is not sufficient evidence to state that music from PMPs constitutes a risk for hypertension and ischaemic heart disease in children and young adults.

Source & ©: SCENIHR,  Potential health risks of exposure to noise from personal music players and mobile phones including a music playing function (2008), Section 4. Opinion, Background, Answer to question 1.

11.3 Under what condition can listening to personal music players be considered safe?

The SCENIHR opinion states:

Question 2:

In case health risks are identified, the SCENIHR is asked:

  1. to identify the level of noise emission safeguarding the health of citizens, taking into account the intensity, length and number of exposures to users of personal music players and mobile phones with the same function and
  2. to identify priority issues for further research

Answer 2a, level of noise emission safeguarding the health of citizens:

Based on workplace studies, the probability of acquiring a hearing loss is negligible at levels below 80 dB(A), and this level might be regarded as safe , no matter how long (daily or weekly) the exposure to sounds from PMPs. It still remains uncertain whether this threshold can be applied to young children.

For higher levels (above 80 dB(A)), the safety of the sound exposure levels to hearing is determined by the time (hours a day) spent on listening to music through the PMPs. With caution, this allowable time can be calculated by using the equal energy rule and the 3 dB exchange rate as it was described in the background. Assuming that an average PMP user listens for 7 hours per week (1 hour/day), this would exceed the Noise at Work Regulations if the sound level for the PMP exceeded 89 dB(A). However, since these devices have been introduced in the market only very recently, there is inevitably insufficient population data on hearing impairment. In assessing the likelihood of hearing loss, consideration of other environmental sources of high level sound emissions need to be taken into account.

As for non-auditory effects of sound exposure from PMPs, no level of noise emission safeguarding the health could be established so far.

Source & ©: SCENIHR,  Potential health risks of exposure to noise from personal music players and mobile phones including a music playing function (2008), Section 4. Opinion, Answer to 2a.

11.4 What further research is needed?

The SCENIHR opinion states:

Answer 2b, priority issues for further research:

In the face of an increasing population at risk of hearing loss and tinnitus due to i) increasing PMP use and acceptance in the EU and ii) the possibility to use PMPs at high sound levels, there is a lack of data concerning:

a) the current PMP use pattern, duration, output level, choice of loud levels and exposure of users to other high level sound sources.

b) the contribution of loud sounds to hearing loss and tinnitus, as well as cognitive and attention deficits in children and young people.

c) long-term studies using more sensitive hearing impairment measures to assess the impact of PMPs on hearing and to identify the potential sub-groups more ‘at risk’ (e.g. children, genetic sub-groups and environmental sub-groups such as those who commute to work or school in noisy surroundings).

d) biological basis of individual susceptibility to noise and the benefits from pharmacological treatment.

e) whether excessive voluntary PMP-listening leads to lasting and irreversible cognitive and attention deficits after the cessation of the noise.

Source & ©: SCENIHR,  Potential health risks of exposure to noise from personal music players and mobile phones including a music playing function (2008), Section 4. Opinion, Answer to 2b.


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