A new study by researchers at National Taiwan University (NTU), published by Environmental Research on February 2, shows that gestational exposure to polychlorinated biphenyls (PCBs) and polychlorinated dibenzofurans (PCDFs) caused adverse asymmetrical hearing effects in early adulthood. Conducted by Dr. Yue Leon Guo, an adjunct professor of department of environmental and occupational medicine and Institute of Occupational Medicine and Industrial Hygiene at NTU, Dr. Pau-Chung Chen, a professor and director of Institute of Occupational Medicine and Industrial Hygiene and director of department of environmental and occupational medicine at NTU, and Mr. Ming-Chieh Li, a Ph.D. candidate of Institute of Occupational Medicine and Industrial Hygiene at NTU, who is advised by Prof. Guo and Prof. Chen.

[Photo: Prof. Yue Leon Guo (the 6th from left) and Mr. Ming-Chieh Li (the 7th from left)]

PCBs and PCDFs are ubiquitous food contaminants in developed countries around the world. However, only two major events of food contamination by PCBs and PCDFs have occurred, 1968 in Japan, and 1979 in Taiwan. In 1979, approximately 2,000 people in central Taiwan were highly exposed PCBs and PCDFs due to ingestion of contaminated rice oil. The children born to mothers exposed to PCBs/PCDFs were called Yucheng children. Previous studies have shown neurological adverse effects in the Yucheng children. Besides, a higher incidence of otitis media was found in Yucheng children, as compared to their age-, gender-matched neighborhood referents. However, No auditory assessment has been performed in Yucheng children. “Therefore we conducted a follow-up study to test the hypothesis whether children gestational exposure to PCBs and PCDFs had higher risk of developing auditory deficits”, said Dr. Guo.

A total of 86 Yucheng children (51.2 percent males) and 97 referent children (50.5 percent males) were invited to participate in this study. Among the Yucheng children, 53 had estimated PCBs/PCDFs concentrations. Compared with age- and gender-matched neighborhood referents, an increased prevalence of mild hearing loss in right ear was found in Yucheng children in their early adulthood. Besides, such damage was related to gestational exposure to 2,3,4,7,8-pnCDF, but not to the marker-PCB congeners.

“This is the first paper describing adverse hearing effects in children with gestational exposure to PCDFs. Gestational exposure to PCBs has also been associated with asymmetric hearing loss in epidemiological studies. However, the mechanism of this kind of asymmetric hearing loss is not clear”, said Dr. Guo. Further studies are warranted to identify the underlying biochemical mechanisms.