I found this article very exciting. Serum PCB Concentrations and Cochlear Function in 12-Year-Old Children. by Trnovec et al. 2010, in which they describe associations between hearing function and PCB exposures in Slovakian kids. (In regular terms: PCB exposure in children probably causes hearing deficits). My forebears were deaf, graduated from the American School for the Deaf, were members of Deaf Baseball and Football teams, and from all the old pictures we have, seem to have had absolutely fun and wonderful lives, so I've never really considered Deafness a disability. However, hearing deficits make it hard for children to learn to read, and they do not get the full range of information available to children without hearing deficits. This can be a problem that may put them at a disadvantage in terms of conventional measures of school and life success. See Banai et al. 2009 for some recent interesting work in this area.
Trnovec et al. also observed differences between ears (no, not that some kids heads were filled with Kapok and some weren't) with the left ear showing a stronger deficit than the right. This does lead one to wonder if people are left earred or right-earred and that the same effect might not be seen if they had recruited only right-handed or left-handed children. This is also more complex than it seems because you can be right handed and "goofy footed" i.e. left foot dominant. I am goofy footed, but its only apparent when I'm out surfing.
Here is a link for understanding the systems through which Trnovec are evaluating correlations of PCB exposure with hearing. http://www.est-med.com/OAE/understanding-using_OAE%20von%20Kemp.pdf
Trnovec, T., Šovčíková, E., Pavlovčinová, G., Jakubíková, J., Jusko, T., Husťák, M., Jurečková, D., Palkovičová, L., Kočan, A., Drobná, B., Lancz, K., & Wimmerová, S. (2010). Serum PCB Concentrations and Cochlear Function in 12-Year-Old Children Environmental Science & Technology, 44 (8), 2884-2889 DOI: 10.1021/es901918h