Application of the kurtosis statistic to the evaluation of the risk of hearing loss in workers exposed to high-level complex noise.
OBJECTIVE
Develop dose-response relations for two groups of industrial workers exposed to Gaussian or non-Gaussian (complex) types of continuous noises and to investigate what role, if any, the kurtosis statistic can play in the evaluation of industrial noise-induced hearing loss (NIHL).


METHODS
Audiometric and noise exposure data were acquired on a population (N = 195) of screened workers from a textile manufacturing plant and a metal fabrication facility located in Henan province of China. Thirty-two of the subjects were exposed to non-Gaussian (non-G) noise and 163 were exposed to a Gaussian (G) continuous noise. Each subject was given a general physical and an otologic examination. Hearing threshold levels (0.5-8.0 kHz) were age adjusted (ISI-1999) and the prevalence of NIHL at 3, 4, or 6 kHz was determined. The kurtosis metric, which is sensitive to the peak and temporal characteristics of a noise, was introduced into the calculation of the cumulative noise exposure metric. Using the prevalence of hearing loss and the cumulative noise exposure metric, a dose-response relation for the G and non-G noise-exposed groups was constructed.


RESULTS
An analysis of the noise environments in the two plants showed that the noise exposures in the textile plant were of a Gaussian type with an Leq(A)8hr that varied from 96 to 105 dB whereas the exposures in the metal fabrication facility with an Leq(A)8hr = 95 dB were of a non-G type containing high levels (up to 125 dB peak SPL) of impact noise. The kurtosis statistic was used to quantify the deviation of the non-G noise environment from the Gaussian. The dose-response relation for the non-G noise-exposed subjects showed a higher prevalence of hearing loss for a comparable cumulative noise exposure than did the G noise-exposed subjects. By introducing the kurtosis variable into the temporal component of the cumulative noise exposure calculation, the two dose-response curves could be made to overlap, essentially yielding an equivalent noise-induced effect for the two study groups.


CONCLUSIONS
For the same exposure level, the prevalence of NIHL is greater in workers exposed to non-G noise environments than for workers exposed to G noise. The kurtosis metric may be a reasonable candidate for use in modifying exposure level calculations that are used to estimate the risk of NIHL from any type of noise exposure environment. However, studies involving a large number of workers with well-documented exposures are needed before a relation between a metric such as the kurtosis and the risk of hearing loss can be refined.
Zhao
Yi-Ming
YM
Center for Clinical Epidemiological Research, Peking University Third Hospital, Beijing, People's Republic of China. yimingzhao115@163.com
Qiu
Wei
W
Zeng
Lin
L
Chen
Shan-Song
SS
Cheng
Xiao-Ru
XR
Davis
Robert I
RI
Hamernik
Roger P
RP
D000328:Adult; D001299:Audiometry; D001309:Auditory Threshold; D016208:Databases, Factual; D004781:Environmental Exposure; D005260:Female; D006317:Hearing Loss, Noise-Induced / Q000453:epidemiology / Q000209:etiology*; D006801:Humans; D008297:Male; D009623:Noise, Occupational / Q000009:adverse effects*; D016011:Normal Distribution; D015995:Prevalence; D011336:Probability; D018570:Risk Assessment; D011795:Surveys and Questionnaires