So popular and yet so toxic: PVC
ARCHITECT'S VIEWPOINT
The other day I came across a plastic house. Not the futuristic World's Fair variety -- this was just an ordinary old house that had been "improved" with a brace of glaring-white vinyl windows, lots of wavy vinyl siding and some flimsy looking vinyl gutters and downspouts. As icing on the petrochemical cake, it was ringed by a white vinyl picket fence.
If there were any termites left in the place, they must have been pretty hungry.
Vinyl is, of course, the plastics industry's more euphonious name for polyvinyl chloride, or PVC. It is the second-largest commodity plastic in the world, second only to polyethylene. About 30 million tons of the stuff were churned out worldwide in 2005, and the trend since then is upward.
Not surprisingly, the building industry is the world's biggest consumer of PVC, with about 36% of production used for pipes. An additional 13% goes to vinyl window frames and 17% to other building applications such as coatings and vinyl flooring (the latter, not to be confused with more eco-friendly linoleum, shows up in two out of three American kitchens).
Salt and petroleum
Like many other environmentally troubling man-made materials, PVC starts out innocuously enough: Its raw ingredients are salt and petroleum.
Saltwater is electrolyzed to produce chlorine, which is then combined with ethylene obtained from oil to produce ethylene dichloride. This compound is processed at a high temperature to create a vinyl chloride monomer that is finally polymerized to form a polyvinyl chloride resin. Various additives make the resin suitable for different uses and protect it from its archenemy, ultraviolet light.
The final result is a material that's cheap and easily processed, which is one reason millions of tons of PVC are gobbled up each year in the form of vinyl windows, siding, gutters, flooring and other economy-grade building products.
Alas, when these not-very-substantial products end up in the landfill -- which they usually do much sooner than the traditional materials they aim to displace -- there's trouble.
A number of environmental authorities consider PVC to be the most toxic plastic in the environment.
Bury it in a landfill, and it just sits there. Burn it, and it produces dioxin, a toxic chemical compound that's a teratogen, mutagen and carcinogen.
Only advantage is cost
PVC has proved its usefulness in many applications.
