Because "we have to make sure producers are not inconvenienced".
The Radiation Council of the Ministry of Education and Science issued its response after deliberating on the new safety standard for radioactive cesium in food submitted by the Ministry of Health and Labor.
First, from Mainichi Shinbun (2/2/2012):
Report on new standard for radioactive cesium: 100 becquerels/kg for infant food
The Radiation Council of the Ministry of Education and Science has been deliberating on the new safety standards for radioactive cesium in food set by the Ministry of Health and Labor. On February 2, the council compiled its report that said it would be OK to loosen the standards for food and milk for infants from 50 becquerels/kg to 100 becquerels/kg. In the next meeting, the council will submit its final report to the Ministry of Health and Labor.
The majority of the council expressed the view that "for all age groups including infants, the annual [internal] radiation exposure would be within 1 millisievert even if they continue to consume food with 100 becquerels/kg of radioactive cesium", and all agreed that the health of children would be well protected. Some said the new standards would be too harsh for fishermen and farmers, and the standards might negatively affect the recovery of the disaster-affected areas. The council's report also says "all stakeholders should participate in deciding the new standards".
In December, the Ministry of Health and Labor revised the existing provisional safety standard of 500 becquerels/kg of radioactive cesium and prepared the new standards of 50 becquerels/kg for infant food, 50 becquerels/kg for milk, and 100 becquerels/kg for other food items. The new standards will be officially decided after the Radiation Council's deliberation and comments from the public and enforced starting April.
Asahi Shinbun on the same subject has this additional information about who else the Radiation Council cares about - entities that do the radiation testing.
[The council] will ask for considerations in using the new standard in April so that there are no confusions in testing and no negative effect on the producers.
To limit the annual radiation exposure to 1 millisievert and below, [the council] points out that the general food standard [of 100 becquerels/kg] is amply safe for the children's health without setting a special standard for food for infants. The council questions the basis for the stricter standard, and worries about the negative effect on what people eat in the disaster-affected areas and on the industries there.
No need to treat infants and toddlers differently when it comes to radioactive materials in food. 100 becquerels/kg radioactive cesium is safe enough for everyone. March on, brave little soldiers.
By the way, the annual radiation exposure they are talking about here is "internal" exposure in addition to the natural background internal exposure from ingesting food. It doesn't even include extra internal radiation from inhaling radioactive materials, and does not include external radiation exposure.
Public comments count nothing, as people in Japan are still finding out. It is to give them an illusion that what they have is democracy. Public meetings, public comments are the formalities only for the power that be to say "See, we listen to the citizens because we hold these meetings and solicit comments from the citizens."