Occupational styrene exposure and hearing loss: a cohort study with repeated measurements

Abstract

This study found, that chronic and intensive styrene exposure increases the hearing thresholds. At levels of about 30-50 ppm as an average inhaled styrene per work day over a period of about 15 years with higher exposure levels above 50 ppm in the past, an elevated risk for impaired hearing thresholds can be expected. The formerly published results on ototoxic effects below 20 ppm could not be confirmed. With few exceptions (at frequencies of 1,000 and 1,500 Hz) no dose-response relationship between threshold and exposure data was found. Improvements of hearing thresholds during work- and exposure-free period are possible.

Perda auditiva associada à exposição ocupacional a solventes orgânicos: uma revisão sistemática

“…The auditory thresholds for high frequency PTA were statistically different for groups with prolonged exposure to styrene levels within recommended limits (8 -12.5 kHz) 22 .…”

“…The worst PTA responses for a wide range of frequencies (0.25 -8 kHz) were found among individuals of the group exposed to the solvent [22][23][24] .…”

“…Focused on the plastic and fiberglass industries, six studies found a positive association between exposure to styrene and Hearing Loss (HL) 11,[20][21][22][23][24] , four of which featured styrene exposure levels below recommended limits [20][21][22][23] . The worst PTA responses for a wide range of frequencies (0.25 -8 kHz) were found among individuals of the group exposed to the solvent [22][23][24] .…”

Extraction of Cochlear Non-linearities with the Bispectral Analysis

“…These differences can be attributed to the effects of the styrene exposure only, as possible confounding effects of noise exposure can be excluded because workers were exposed to noise levels well below the action level of 85 dBA set by the Occupational Safety & Health Administration. Many studies in literature investigated effects of organic solvents (such as styrene) on hearing functionality, but only in few cases these effects have been evaluated using OAEs [7,22,23]. It is not possible to make a direct comparison of our results with those obtained in these last studies because of differences in mixture of organic solvents to which workers are exposed, levels of exposure, and confound effects due to combined noise exposure.…”

“…In [23], authors found that at average inhaled styrene levels of about 30-50 ppm per working day over a period of about 15 years with previous exposure to higher levels above 50 ppm increased the risk for hearing impairment, but no relationship was found between parameters extracted from TEOAEs and level of exposure.…”