Those buckets are generally high density polyethylene (#2 plastic).

They're one of the safest when it comes to breakdown caused by heat/environment. Leaching should be extremely minimal and plant roots do a pretty good job at exclusion anyway.

Agree. Plastic doesn't actually "leach" it just slowly degrades/breaks down over years - depending on the amount of exposure to sun and weather and heat.

I will suggest however that before putting the work into this project you review some of the many discussions over on the Tomato forum here about the problems with trying to grow tomatoes in upside down hangers such as this. It isn't all it is hyped up to be, :)

Dave

Food has been transported in plastic buckets for many years and some are labeled as food safe. Whether that might include the buckets sold by the big box stores is not known. Many organic growers would not consider using plastic containers if only because they are made of non renewable resources.