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The aim of this study was to examine the hypothesis that organochlorine pesticides (OCPs), hexachlorobenzene (HCB), β-hexachlorocyclohexane (β-HCH), and 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (p,p'-DDT) and its metabolite 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene (p,p'- DDE) are ototoxic to humans. A multivariate general linear model was designed, in which the statistical relation between blood serum concentrations of HCB, β-HCH, p,p'-DDT, or p,p'-DDE at different ages (at birth, 6, 16, and 45 months) and the distortion product otoacoustic emissions (DPOAEs) was treated as multivariate outcome variables. Polychlorinated biphenyl (PCB) congeners and OCPs were strongly correlated in serum of children from our cohort. To ascertain that the association between DPOAEs at a given frequency and concentration of a pesticide is not influenced by PCBs or other OCP also present in serum, we calculated benchmark concentrations (BMCs) relating DPOAEs to a serum pesticide alone and in presence of confounding PCB-153 or other OCPs. We found that BMCs relating DPOAEs to serum pesticides are not affected by confounders. DPOAE amplitudes were associated with serum OCPs at all investigated time intervals, however, in a positive way with prenatal exposure and in a negative way with all postnatal exposures. We observed tonotopicity in the association of pesticides with amplitude of DPOAEs as its strength was frequency dependent. We conclude that exposure to OCPs in infancy at environmental concentrations may be associated with hearing deficits.

Experimental evidence from animals indicates that exposure to polychlorinated biphenyls (PCBs) causes deterioration of the outer hair cells (OHCs) of the cochlea. To test this hypothesis in humans, we measured serum PCB concentrations in 574 12-year-old children residing in three districts in the Slovak Republic using high-resolution gas chromatography with microelectron capture detection. As a marker of cochlear status, we measured transient evoked (TE) and distortion product (DP) otoacoustic emissions (OAEs), and assessed the cross-sectional association between serum PCBs and OAEs. Median total PCB concentrations were 352.8, 150.5, and 134.9 ng/g lipid in Michalovce, Svidnik, and Bratislava, respectively. In multivariate regression models where otoacoustic measures were modeled as a function of log (base 10) PCB concentrations with adjustment for gender, age, and site of examination, dioxin-like PCBs, nondioxin-like PCBs and a PCB grouping targeting upregulation of hepatic uridine 5'-diphospho-glucuronosyltransferase were significantly associated with lower TEOAE powers at 1000 and 1500 Hz. At 1500 Hz, we observed a strong association with sum of PCBs and DL-PCBs, in the left ear only. The DPOAEs at 1000 Hz were associated with all four PCB groupings. The results of this study show that PCBs may affect the OHCs of the cochlea, a result consistent with findings from animal studies published to date.

Objective: The aim of this normative study was to examine cochlear status and possible ear asymmetry and gender effect in transient evoked and distortion product otoacoustic emissions in a group of healthy 12-year-old children in Slovakia., Methods: Two hundred and twenty-nine 12-year-old children from Slovakia with normal hearing were included in this study. Adolescents with acute infection, abnormal otoscopic findings and abnormal tympanometry were excluded. Pure tone audiometry was performed in standard conditions in a sound proof room. Recordings of transient evoked (TE) and distortion product otoacoustic emissions (DPOAEs) were performed using an ILO 292 USB Echoport. Parameters of hearing thresholds and OAEs were compared using correlation analysis and Wilcoxon test., Results: We found highly statistically significant associations between the hearing thresholds for the left and right ears. When comparing pure tone audiometry with OAEs no significant correlation was found. In TEOAE a significant gender effect and side effect in TEOAE SNR were found. On the other hand there was no side effect in TEOAE response level. In DPOAE neither gender nor side effects were determined., Conclusions: This is the first comprehensive information on cochlear status among Slovak adolescents. The TEOAEs were significantly higher in girls than boys, but the ear asymmetry in TEOAE was not significant. For DPOAE responses ear asymmetry and gender did not play a role. The data obtained are a basis for population hearing screening, especially for hearing screening programs in infants and children in Slovakia. Moreover data from particular age group represent a link between data from infants and adults., (Copyright (c) 2009 Elsevier Ireland Ltd. All rights reserved.)