Inner ear damage from toy cap pistols and fire-crackers

Preloaded D-methionine protects from steady state and impulse noise-induced hearing loss and induces long-term cochlear and endogenous antioxidant effects

Objective

Determine effective preloading timepoints for D-methionine (D-met) otoprotection from steady state or impulse noise and impact on cochlear and serum antioxidant measures.

Design

D-met started 2.0-, 2.5-, 3.0-, or 3.5- days before steady-state or impulse noise exposure with saline controls. Auditory brainstem response (ABRs) measured from 2 to 20 kHz at baseline and 21 days post-noise. Samples were then collected for serum (SOD, CAT, GR, GPx) and cochlear (GSH, GSSG) antioxidant levels.

Study sample

Ten Chinchillas per group.

Results

Preloading D-met significantly reduced ABR threshold shifts for both impulse and steady state noise exposures but with different optimal starting time points and with differences in antioxidant measures.

For impulse noise exposure, the 2.0, 2.5, and 3.0 day preloading start provide significant threshold shift protection at all frequencies. Compared to the saline controls, serum GR for the 3.0 and 3.5 day preloading groups was significantly increased at 21 days with no significant increase in SOD, CAT or GPx for any impulse preloading time point. Cochlear GSH, GSSG, and GSH/GSSG ratio were not significantly different from saline controls at 21 days post noise exposure.

For steady state noise exposure, significant threshold shift protection occurred at all frequencies for the 3.5, 3.0 and 2.5 day preloading start times but protection only occurred at 3 of the 6 test frequencies for the 2.0 day preloading start point. Compared to the saline controls, preloaded D-met steady-state noise groups demonstrated significantly higher serum SOD for the 2.5–3.5 day starting time points and GPx for the 2.5 day starting time but no significant increase in GR or CAT for any preloading time point. Compared to saline controls, D-met significantly increased cochlear GSH concentrations in the 2 and 2.5 day steady-state noise exposed groups but no significant differences in GSSG or the GSH/GSSG ratio were noted for any steady state noise-exposed group.

Conclusions

The optimal D-met preloading starting time window is earlier for steady state (3.5–2.5 days) than impulse noise (3.0–2.0). At 21 days post impulse noise, D-met increased serum GR for 2 preloading time points but not SOD, CAT, or GpX and not cochlear GSH, GSSG or the GSH/GSSG ratio. At 21 days post steady state noise D-met increased serum SOD and GPx at select preloading time points but not CAT or GR. However D-met did increase the cochlear GSH at select preloading time points but not GSSG or the GSH/GSSG ratio.

Estudio del nivel sonoro de las armas de avancarga utilizadas en fiestas populares y recreación histórica

Introducción y Objetivos: Las manifestaciones populares asociadas al uso festivo de armas antiguas o réplicas de avancarga tienen numerosas y antiguas referencias a lo largo de nuestra geografía, pero se carecía de estudios de los noveles sonoros derivados de su uso. Se diseño un trabajo que permitiera analizar los niveles de ruido generados, para poder orientar medidas de protección a sus usuarios. Material y método: Se recogieron datos de 24 armas de 22 tipos distintos, determinando distintos puntos de medición, y se analizaron los resultados sonométricos en función de los tipos de arma, distancia al tirador y rango de frecuencias. Resultados: Los datos obtenidos demuestran unos mayores niveles de sonido para los tonos graves, con medias de 102 a 117dB medidas a un metro del tirador, con poca atenuación en distancias a 5 y 10 metros y sin diferencias clínicamente relevantes derivadas del tipo de arma, distancia o carga de pólvora. Conclusiones: Los niveles de sonido generado por las armas de avancarga aconsejan recomendar las medidas adecuadas de protección, no hallándose diferencias clínicamente relevantes para los distintos tipos de armas utilizadas.

[Inner ear damage due to leisure and broadband noise. An experimental study on initial and permanent functional and morphological damage]

The initial and permanent effects of leisure noise (toy pistols, rock music) compared to broadband noise were examined in 68 guinea pigs. Auditory threshold shifts at 1.5, 2, 3, 4, 6, 8, 12 und 16 kHz were registered before and immediately after exposure as well as on days 1, 2, 3, 5,7 and 21 post-exposure using the auditory brain stem response (ABR) technique. In order to examine cilia and hair cell damage in eight cochlear frequency regions (<0,4 kHz, 0,4-0,8 kHz, 0,8-1.5 kHz, 1.5-3 kHz, 3-5 kHz, 5-11.5 kHz, 11.5-26 kHz und >26 kHz), cytocochleograms were performed immediately after exposure and on days 1, 7 and 21.Frequency dependent functional or morphological damage was found which depended on the type of trauma tested. All results were highly significant ( P<0.001). The results show that partial recovery of hearing occurred within 3 days of acute acoustic trauma induced by toy pistols and within 1 day after exposure to rock music or broadband noise. There was no further recovery of hearing within the following 18 and 20 days, respectively. Furthermore, permanent threshold shifts after exposure to rock music or broadband noise were not associated with cilia and/or hair cell damage.

Noise level analysis of commercially available toys

There have been several isolated reports of hearing loss due to noise levels from toys. Guidelines for noise production by toys is regulated by the Voluntary Product Standards PS 72-76: Toy Safety Act of 1969. To determine the current risk of noise induced hearing loss from toys currently on the market, 25 toys were purchased at a national toy store chain and sound levels were measured at distances approximating ear level (2.5 cm) and a child's arm length (25 cm) from the surface of the toy. Testing revealed peak sound levels ranging from 81 to 126 dBA at 2.5 cm and 80 to 115 dBA at 25 cm from the surface of the toy.

Noise levels from toys and recreational articles for children and teenagers

This study examined the noise level emitted by toys and recreational articles used by children and teenagers. The results indicate that many of the items tested emit sufficiently intense noise to be a source of noise induced hearing loss in school-age children. While the baby toys provided noise exposure within the limits of national regulations, they are most intense in a frequency range that corresponds to the resonance frequency of the external auditory canal of very young children. Hobby motors emit noise that may require protection depending upon the length of use. Fire-crackers and cap guns emit impulse noises that exceed even conservative standards for noise exposure.