Toys and games: poorly recognised hearing hazards?BMJ 1998; 316 doi: https://doi.org/10.1136/bmj.316.7143.1473 (Published 16 May 1998) Cite this as: BMJ 1998;316:1473
European case ascertainment will help to confirm the association
- Linda M Luxon, Professor of audiological medicine () Protection aganst Noise Leisure Noise Research Group, c/o Per-Anders Hellstrom, Sahlgren's Hospital, Hearing Research Laboratory, PO Box 8417, 40275 Göteborg, Sweden
In 1995 the World Health Organisation estimated that 120 million people worldwide had a disabling hearing impairment.1 Many causes of hearing impairment are recognised, but noise exposure in childhood has been largely ignored.
There is evidence to suggest that children's hearing is particularly vulnerable to noise. Animal experiments have shown a period of particular sensitivity shortly after birth.2 Moreover, the heads, ears, and external auditory canals of children are shaped differently from those of adults, allowing greater amplification of high frequency sounds,3 which are relatively more harmful to hearing than low frequency sounds. Over the past decade the incidence of high frequency loss in schoolchildren has not decreased in Scandinavia,4 although it has in protected industrial workers. 1 2
Several studies have reported permanent sensorineural hearing loss in children related to noisy toys, games,5 fire crackers,6 and gunfire exposure.7 Squeaky, brightly coloured toys for babies and toy motor vehicles may emit sounds of 78-108 dB(A) measured at 10 cm distance,8 while at arm's length model aeroplanes may emit high pitched sounds of 112 dB(A). At the child's ear sound levels of up to 122 dB(A) for toy mobile telephones and 150-160 dB(C) (which exceeds the noise at work peak action level9) for toy weapons have been reported and may cause severe auditory damage. Certain toys may be “safe” if used properly, but if used improperly the noise level may greatly exceed the sound levels carrying risk for hearing damage— for example, if a firecracker is thrown and explodes next to the ear, or a toy gun is fired next to the head, as portrayed in videos and films.
Importantly, young children up to the age of 6 years cannot describe hearing loss, and older ones, who can complain of hearing loss or tinnitus after a loud bang, may be reassured by adults who do not understand the risk of damage. Single cases tend not to be reported in medical journals, any individual clinician is unlikely to see many cases, and few doctors have relevant experience and interest.
Reporting the relation between noisy toys and hearing loss is also problematic, as a causal association can be confirmed only when hearing loss or tinnitus is reported immediately after exposure and audiometry results from before and after the incident are available. No such cases have been published. A highly probable relation can be assumed if a normal audiogram was obtained one to three years before the alleged incident. A probable relation is established if the peak sound level of an offending toy exceeds 140 dB(C) and exposure is followed by audiometrically confirmed immediate hearing loss. A probable relation may also be identified by population studies if a worse high frequency hearing loss, with a characteristic 4 kHz audiometric notch, is identified among children who have used noisy toys than in non-users. However, pure tone audiometry is relatively insensitive for monitoring minor damage, and only children at the more sensitive end of the distribution of noise susceptibility may be affected, so such findings would depend on accurate reports of the amount of use of all types of noisy toy. Newer sensitive tests of cochlear function, such as otoacoustic emission measurements, may help in detecting minor, but definite, auditory deficits.
Toy manufacturers suggest that toy related noise induced hearing loss is rare, and they may be correct. However, the vulnerability of children's hearing to intense sound is unknown, and the lack of reports may reflect only a failure to report such incidents. Precisely because such cases are thought to be rare the approach of case ascertainment is appropriate, as well as the more usual approach of comparing retrospectively exposed and non-exposed groups. Experimental studies in children are unethical, but population studies of young people show about 10% of cases with hearing loss that might be attributable to noise.8
The European Concerted Action on Protection Against Noise has established a centre in Gothenburg that will evaluate any possibly hazardous toy and compile a European directory of clinical cases. From this central directory clearer conclusions may emerge about the prevalence of dangerously noisy toys and the consequences of such exposure in childhood. If conclusive evidence does emerge to link noisy toys and hearing damage legislation could ensure that no toy is capable of producing hazardous levels of noise.