Yusho incident

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Yusho incident: contamination of rice oil with PCB in Japan. In the year 1968, patients with chloracne came to the dermatology clinic in Fukuoka, and this disease was connected with the consumption of a batch of rice oil which was contaminated (2000-3000 mg/kg [ΣPCB in fat]) with Kanechlor 400, a PCB used in the heat exchanger leaking to the rice oil. The average estimated intake per person was 633 mg PCBs and 3.4 mg PCDFs among some other chemicals. This has been estimated to be 154,000 pg/kg/day (I-TEq per body weight per day) or 100,000 times higher than average background intake. The earliest signs of toxicity were enlargement and hypersecretion of Meibomian glands in the eyes, swelling of the eyelids and pigmentation of skin and mucous membranes. Many different skin problems followed, including darkening of the skin, hyperkeratosis and chloracne. Babies born to Yusho mothers were smaller than normal, they showed a dark brown pigmentation, and some of them had gingival hyperplasia and dentition at birth. The total number of patients was about 1,200 which is rather small number to evaluate effects on cancer reliably, but there seems to be an excess of cancer deaths among the male patients. Japanese research groups have concluded that the main signs and symptoms were due to the minor contaminants, i.e. PCDFs of the PCB contaminating rice oil. International Programme on Chemical safety concluded in 1993 that the intoxications of Yusho and Yu-Cheng were caused mainly by a combined effect of PCBs (especially coplanar ones) and PCDFs. For more information on Yusho see "Yusho; A human disaster caused by PCBs and related compounds", ed. By M. Kuratsune, H. Yoshimura, Y. Hori, M. Okumura, Y. Masuda, Kyushu Univ. Press, Fukuoka, 1996.

See also

• Yushō disease in Wikipedia