Question
We are wanting to build a greenhouse but have heard a lot about platic and toxins.  Would the plastic used in greenhouses leach toxins into the ground when it becomes warm and condensation drips into the soil?

Answer
Not if you use Lexan, a double layer sheet of polycarbonate with air layers inbetween.  There is no condensation, and it provides an insulation barrier.  Very long lasting and comes in sheets 4 feet wide and as long as you need them to be up to 20 feet.  And, it is not expensive relative to how short the life span of ordinary plastic is.  We have had it on our greenhouse for 12 years, no problems.  Easy to work with, just cut with a circular saw, drill holes in it and screw it down to a frame using screws with little rubber washers, available at most hardware stores.  Lexan is usually available at home depot or lowes.