Leaching has been a topic of concern since I started planning the garden in my Crown Heights Brooklyn backyard. I am concerned with the possibility of leaching in the garden, which is why I am building planter boxes with legs - to deter any chemicals from seeping into the wood and roots of the plants.
Buildings in Brooklyn are being renovated all the time and contractors throw everything into the backyard during demolition. Pictured above are pipes in my backyard as flowers were pushing to the surface after a long winter. I have since removed the pipes, but you can be certain those pipes and other rubbish have been a fixture in the backyard for many, many years. It's hard to know what dangerous chemicals are infiltrating into the soil, but you can be sure that lead poisoning is a real threat.
According to this article on lead poisoning, it is common in urban areas to have high levels of lead in the soil because of leaded gasoline and paint. Lead-based paint was banned in 1978 but Crown Heights Brooklyn was being developed in the early 1900's and a lot of buildings on my street were built in the 40's and 50's, preceding the ban.
Arsenic in Pressure Treated Wood?
Years ago, there was concern about using pressure treated wood to build planter boxes because it contained arsenic. In the research I have done, this isn't an issue since the use of this dangerous chemical in pressure treated wood was banned for consumer use by the EPA in 2003. (Any pressure treated lumber manufactured for consumer use after that date has no arsenic in it.)
Helpful articles to check out: