Professor Kunihiko Takeda of Chubu University says in his April 19 blog post that:
after the Fukushima I Nuke Plant accident the government suddenly changed the procedure to measure the radiation level in vegetables, and issued a notice that "the vegetables to be analyzed for radioactive materials should be taken out of the boxes, washed carefully under running water, and then analyzed."
Professor Takeda continues (my quick translation, not necessarily literal):
That caused the total loss of confidence in the safety of the vegetables.
The reason? It is easy to remove the radioactive materials on the vegetables when they are about to be shipped, soon after having been harvested. By the time they reach the consumers, it would be difficult to remove the radioactive materials as they stick fast on the surface or have penetrated inside the vegetables.
You can't trust the radiation level numbers on vegetables and other farm produce announced by the government.
There are people from Fukushima near the nuke plant coming to Tokyo and sell their vegetables saying "see how fresh they look!" That contributes to further loss of confidence.
Why? Because vegetables contaminated with radioactive materials can be very fresh, but being fresh doesn't mean being safe. In the case of mercury poisoning in Minamata, the contaminated fish were consumed as "fresh".
Municipalities are issuing a "declaration of safety" on certain farm produce like vegetables after they scrub them clean. Don't trust the farm produce from the municipalities that have issued such a "declaration".
I receive emails from conscientious farmers who have grown vegetables that people can consume without safety worries but are now at a loss how to find out whether their produce is safe.
It's a serious business for both producers and consumers.
It is the government who's creating and spreading the "baseless rumors" by issuing the guidance "to wash vegetables under running water before analyzing".
Professor Takeda's blog continues, and I will post as I finish translating.