High levels of dioxin have been detected in river fish, apparently after they consumed food contaminated by microorganisms from soil carrying the deadly chemical, an Ehime University research team said Wednesday. According to a five-year study by the group, led by Tadaaki Wakimoto, a professor of environmental chemistry at the university, the contamination levels of dioxin in fish in reservoirs were between 10,000 and 100,000 times higher than the levels of the water itself. Dioxin is a cancer-causing chemical typically produced when waste containing plastic is burned. The research team is calling for a review of current environmental standards for soil and water quality because they do not take these data and methods of pollution into consideration. The government has set the maximum tolerable dioxin levels at 1 picogram of dioxins per liter of water and 1,000 picograms per gram of soil. One picogram is a trillionth of a gram. The team has traced the way in which dioxin pollutes the air, soil and water of the Matsuno plains in Ehime Prefecture, discovering that contamination levels in rivers, ponds and reservoirs rise after after it rains. The higher the dioxin levels of mud at the bottom of reservoirs, it said, the higher the contamination level of the water. The team concluded that the dioxin enters the water attached to microorganisms in soil. "Based on the data we have gathered, some fish can be highly polluted with dioxin despite being in an environment that meets the government's maximum tolerable (dioxin) standards," Wakimoto said. The Environment Agency said its standards do not take into account the route by which dioxin attached to soil travels into bodies of water, eventually accumulating in fish and animals, because there was a "lack of sufficient data to back up (the existence of) such a route" when the regulations were drafted. "We may consider new regulations for water pollution by dioxin if soil is confirmed to be an origin of contamination," an agency official said. "At this moment, however, we don't believe soil can be a major pollution source."