Why Does FDA Tolerate More Radiation Than EPA?

Since the Environmental Protection Agency began detecting radiation in rainwater and milk at levels above its maximum contaminant level, government officials have been downplaying the importance of EPA’s maximum contaminant level.  They would much prefer us to speak in terms of the Food and Drug Administration’s “Derived Intervention Level.”
The two levels could hardly be more different:

• EPA does not allow drinking water to contain more than 3 picoCuries per liter of radioactive istotopes like iodine-131 and cesium-137.
• FDA allows up to 4,700 picoCuries of iodine-131 in a liter of milk and up to 33,000 picoCuries of cesium-137.   link