miles: scientists like ken buesseler would like some academic rigor.would want to have someone other than the operator in charge of disposing of this check those numbers in the tanks. and, equally as important, as an oceanographer, i would want to be out there now measuring for this suite, this range of different radionuclides in the seawater, on the seafloor, in the sea life, just to establish those baselines very clearly. miles: water from the tanks containing tritium will flow to this spot at about 100 gallons a minute, where it will be mixed and diluted. lake barrett: clean water is brought in from the ocean through three 1000-horsepower pumps. each flow about 33,000 gallons per minute. miles: the water will flow through this large tunnel to a discharge point two-thirds of a mile offshore. a two-square-mile area around it will be closed to fishing. inside the plant, tepco has built fish tanks filled with flounder. some are exposed to the diluted tritium. the utility says it will closely monitor their health. it's an effort to assure the public. but

be certainly a factor of 10 what the level should be in drinking water >> marine radio chemist ken buesselerst at the woods hole oceanographic institution. he says every nuclear power plant in the world releases tritium tainted water. >> with four hundred or so nuclear power plants around the world releasing tritium, it would be hard to single out this particular site and say, no, you can't, the others are ok. the other 399 sites are releasing it and the ocean contains tritium already from those atmospheric nuclear weapons testing going back to the 1950's and 1960's. >> regardless, japan's neighbors are crying foul. >> japan has yet to produce solid scientific proof to convince the international community that it's safe. >> if it were china, going to release some radioactive water into the ocean, the western media will be explode. >> state run media in china has led a chorus of condemnation along with pacific island nations, and until a recent election, south korea. but japan says the critique from its regional rivals deliberately ignores the science, and is hypocritical. china is the fastes

. >> marine radio chemist ken buesseler is a senior scientist at the woods hole oceanographic institutiony you can't just keep collecting more and more water. what's being considered also is releasing some of this water back to the ocean. >> every nuclear power plant in the world routinely discharges tritiated water, and now tepco and the japanese government are planning to do the same here. this has triggered a chain reaction of anger and concern from fishermen nearby -- fishermen nearby and other countries throughout the region. more on that when we continue our series. for the pbs "newshour," i'm miles o'brien in futaba, japan. ♪ geoff: a recent government study estimates nearly half of america's tap water could contain toxic "forever chemicals" known as pfas. as stephanie sy reports, there are thousands of these chemicals and exposure to them can lead to serious health outcomes. stephanie: last month, the u.s. geological survey tested the nation's drinking water and found at least 45% of samples had one or more forever chemicals. the study also found contamination centered in urban ar