Japanese ingest an average 2.41 picograms of dioxins per kilogram of body weight, and fish represent the largest source of the dioxins, a study conducted by the Health and Welfare Ministry revealed Wednesday. The average, which includes coplanar PCBs, or polychlorinated biphenyls, falls below the 10 picograms set by the ministry as the tolerable daily intake (TDI). However, the World Health Organization this year revised its TDI rate, setting it at one to four picograms per kilogram of body weight. The results of the survey are likely to influence the ministry's ongoing review of its TDI rates.