Audiometric Findings in Workers Exposed to Low Levels of Styrene and Noise

Abstract

Audiometry and exposure measurements were conducted on workers from fiberglass and metal products manufacturing plants and a mail distribution terminal (N = 313). Workers exposed to noise and styrene had significantly worse pure-tone thresholds at 2, 3, 4, and 6 kHz when compared with noise-exposed or nonexposed workers. Age, noise exposure, and urinary mandelic acid (a biologic marker for styrene) were the variables that met the significance level criterion in the multiple logistic regression. The odds ratios for hearing loss were 1.19 for each increment of 1 year of age (95% confidence interval [CI], 1.11-1.28), 1.18 for every decibel >85 dB(A) of noise exposure (95% CI, 1.01-1.34), and 2.44 for each millimole of mandelic acid per gram of creatinine in urine (95% CI, 1.01-5.89). Our findings suggest that exposure to styrene even below recommended values had a toxic effect on the auditory system.

Chemical exposure and hearing loss

“…Several clinical and epidemiological studies confirmed an association between exposure to solvents (styrene, toluene, xylenes, solvent mixtures, and jet fuels) in the workplace and increased prevalence of hearing loss, as well as poor hearing thresholds beyond the traditional 4 kHz noise-related audiometric notch. [83][84][85][86][87][88][89][90][91][92] For an extensive review of human studies, see Johnson and Morata 93 (available online at https:// gupea.ub.gu.se/handle/2077/23240).…”

Occupational Chemical-Induced Hearing Loss

“…In the study of Muijser et al (1988), high frequency hearing thresholds were significantly increased in those workers with the greatest exposure to styrene. Also, Morata et al (2002) found an additive damage effect of styrene for pure-tone thresholds at 2, 3, 4 and 6 kHz. The odds ratio for hearing loss estimated by Morata et al (2002) was 2.44 times greater for each increment of 1 mmol of mandelic acid (a biologic marker of styrene exposure) per gram of creatinine in urine.…”

“…Also, Morata et al (2002) found an additive damage effect of styrene for pure-tone thresholds at 2, 3, 4 and 6 kHz. The odds ratio for hearing loss estimated by Morata et al (2002) was 2.44 times greater for each increment of 1 mmol of mandelic acid (a biologic marker of styrene exposure) per gram of creatinine in urine. Morata et al (2002) suggested that styrene can affect the mid-audiometric frequency of 2 kHz, which is in agreement to the findings of Sliwinska-Kowalska et al (2001).…”

“…The odds ratio for hearing loss estimated by Morata et al (2002) was 2.44 times greater for each increment of 1 mmol of mandelic acid (a biologic marker of styrene exposure) per gram of creatinine in urine. Morata et al (2002) suggested that styrene can affect the mid-audiometric frequency of 2 kHz, which is in agreement to the findings of Sliwinska-Kowalska et al (2001). Morata et al (2002) also stated that styrene even below recommended values had a toxic effect on the auditory system.…”

Walk-through survey report: styrene and noise exposures during fiber reinforced plastic boat manufacturing at U.S. Marine Incorporated, Arlington, Washington.

“…9,10 Styrene has been shown to be a potent ototoxicant by itself, and can have a synergistic effect when presented together with noise or ethanol. 11,12,13,14 The primary sources of environmental evaluation standards and guidelines for the workplace are: 1) the OSHA Permissible Exposure Limits (PEL), 15 2) The NIOSH Recommended Exposure Limits (REL), 16 and 3) the American Conference of Governmental Industrial Hygienists= (ACGIH ® ) Threshold Limit Values (TLV ® ). 19 Employers are mandated by law to follow the OSHA limits; however, employers are encouraged to follow the most protective criteria.…”