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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.

BackgroundSome experimental and human data suggest that exposure to polychlorinated biphenyls (PCBs) may induce ototoxicity, though results of previous epidemiologic studies are mixed and generally focus on either prenatal or postnatal PCB concentrations exclusively.ObjectivesOur aim was to evaluate the association between pre- and postnatal PCB concentrations in relation to cochlear status, assessed by distortion product otoacoustic emissions (DPOAEs), and to further clarify the critical periods in development where cochlear status may be most susceptible to PCBs.MethodsA total of 351 children from a birth cohort in eastern Slovakia underwent otoacoustic testing at 45 months of age. Maternal pregnancy, cord, and child 6-, 16-, and 45-month blood samples were collected and analyzed for PCB concentrations. At 45 months of age, DPOAEs were assessed at 11 frequencies in both ears. Multivariate, generalized linear models were used to estimate the associations between PCB concentrations at different ages and DPOAEs, adjusting for potential confounders.ResultsMaternal and cord PCB-153 concentrations were not associated with DPOAEs at 45 months. Higher postnatal PCB concentrations at 6-, 16-, and 45-months of age were associated with lower (poorer) DPOAE amplitudes. When all postnatal PCB exposures were considered as an area-under-the-curve metric, an increase in PCB-153 concentration from the 25th to the 75th percentile was associated with a 1.6-dB SPL (sound pressure level) decrease in DPOAE amplitude (95% CI: -2.6, -0.5; p = 0.003).ConclusionsIn this study, postnatal rather than maternal or cord PCB concentrations were associated with poorer performance on otoacoustic tests at age 45 months.

Abstract: 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 &y& Elsevier]