Collective Roots is a non-profit located in East Palo Alto, California that advocates local food production.
They have discovered the safe and productive benefits of portable micro gardens (aka sub-irrigated planters (SIPs) like the EarthBox.
One good example of safe gardening is the nearby Google headquarters (aka Googleplex) garden. It is a joint project of Google and The Growing Connection, a UN organization. They chose to plant the garden in EarthBoxes, one of many portable micro garden options.
With safety as the primary goal, the first intelligent step is to have your soil tested for toxic metals contamination before growing any edible plants in the ground.