Association Between Environmental Exposure to PCBs and Hearing Impairment in 8- to 9-Year-old Children

Abstract

SM1-PD-02 Introduction: A chemical plant produced PCBs between 1959 and 1984. Disposal of effluent into a river resulted in contamination of a site sized about 70 by 30 km. It accommodates approximately 250,000 inhabitants and is recognized as one of the most heavily polluted areas with PCBs in the world. The data for sum of PCB serum concentrations for 433 8- to 9-year-old children living in this area in 2002 were: mean 528.2 ng/g of serum lipids, median 321 ng/g of serum lipids and limits of the quartiles 18, 175, 321, 618, 6477 all in ng/g of serum lipids. It was reported that auditory thresholds for 1-kHz tones were elevated by approximately 25 dB in animals exposed to PCB.1 They were linked to a loss of outer hair cells.2 Therefore, hearing examination was included into our study program. Methods: The concentrations of selected PCB congeners in serum of 8- and 9-year-old children were determined using GC/ECD. Hearing examination involved pure tone audiometry (Madsen Orbiter 922), transient evoked otoacoustic emissions (Otodynamics ILO 88), auditory brainstem response (Otometrics BERA System), and tympanometry (Siemens SD-30 tympanometer). Results: The main findings are as follows: An association between negative middle ear pressure and PCB serum concentrations. Increase of the hearing thresholds at low frequencies associated with higher PCB serum concentrations. No association between the serum PCB concentrations and any of the auditory brainstem response parameters. Higher serum PCB concentrations associated with decreased emission levels of the transient evoked otoacoustic emissions. The sound pressure level of otoacoustic emissions was associated with results of several neurobehavioral tests applied in the same cohort of children and with the proportion of the permanent teeth with demarcated and diffuse opacities or hypoplasia. Discussion and Conclusions: The data of Longnecker et al3 did not support adverse effects of PCBs during early life on sensorineural hearing loss. The exposure levels were twofold higher than recent background levels in the United States. In contrast to the previous data at our much higher exposure levels, subclinical but significant increase of hearing thresholds and a decrease of sound pressure level of transient evoked otoacoustic emissions were associated wth PCBs serum concentrations. A follow-up study on the same cohort will bring additional information on related time trends.