[abakker]

Please see: http://www.archdaily.com/160892/the-pros-and-cons-of-cargo-c...

"For instance, the coatings used to make the containers durable for ocean transport also happen to contain a number of harmful chemicals, such as chromate, phosphorous, and lead-based paints. Moreover, wood floors that line the majority of shipping container buildings are infused with hazardous chemical pesticides like arsenic and chromium to keep pests away."

and

"Reusing Containers seems to be a low energy alternative, however, few people factor in the amount of energy required to make the box habitable. The entire structure needs to be sandblasted bare, floors need to be replaced, and openings need to be cut with a torch or fireman’s saw. The average container eventually produces nearly a thousand pounds of hazardous waste before it can be used as a structure."

[patcheudor]

This! I've looked seriously into making a large shipping crate home by slowly accumulating them for storage and whatnot at my farm. Ultimately, after learning about the hazardous materials used in many, I gave up. Besides the points mentioned by abakker, one of the things that really got to me was the 'mystery box' aspect. Simply put, you don't know what they carried or what got spilled inside. Was it carrying pesticides? Did a bunch of compact florescence break inside in a storm releasing mercury into the container? There have even been reports of shipping containers which are radioactive above background levels, presumably from spilled nuclear medical waste or shipping something like Uranium ore. Before you call me nuts:

"About 20 million consignments of all sizes containing radioactive materials are routinely transported worldwide annually on public roads, railways and ships."

http://www.world-nuclear.org/information-library/nuclear-fue...

Note that sprayed on closed cell insulation does little to nothing to mitigate many of the toxins which can be found in shipping containers including mercury - it just makes it poisonous for longer. To use them for a dwelling all wood needs to be removed and they need to be sand or water blasted down to bare metal.