RAW MATERIALS: PVC is a unique plastic. It’s the only polymer whose primary raw material is not fossil fuels. In PVC’s case, 57% of its raw material is derived from salt (sodium chloride).
ADDITIVES: Flexible PVC uses two main additives: plasticizers and stabilizers. The plasticizers keep the product flexible, while the stabilizers prevent thermal decomposition when the product is heated up. Heat stabilizers are mostly made of tin, along with calcium and zinc, or organic stabilizers and plasticizers are increasingly made of bio-based materials or DOTP, a terephthalate that is widely considered to be benign.
STABILITY: PVC is touted for its stability and inertness. PVC without plasticizers is inflexible, and it’s often used for long-term functions, like as underground pipes, because of its inherent stability at a molecular level. Vinyl monomer has been detected in landfills, and studies by the California Air Resources Board have shown it to derive from natural processes. Some PVC from the 1970s or earlier was known to have monomer in it that had not converted, but this doesn’t happen with today’s processes. When it does break down, say through pyrolysis (thermal decomposition in the absence of oxygen), hydrogen chloride is released, prohibiting any conversion back to monomer.
TOXIC ISSUES: Incinerating vinyl produces dioxin, thanks to the chlorine in its chemistry. For the same reason, other materials with chlorine present similar hazards; all animals and plants release dioxins upon incineration. The real issue with dioxins and other dangerous chemicals is exposure, and dioxin volume from PVC incineration falls well below danger levels and is far lower than dioxin released from forest fires and barbeques.
VINYL MONOMER: Vinyl chloride is dangerous. Back in the 1970s, when it was even used as a propellant in aerosol sprays, workers at PVC plants got cancer from exposure. After that, production processes were put in place to prevent exposure, and since then there have been no issues. However, it’s still a dangerous chemical. Toward the end of 2012, a train derailment in New Jersey spilled 180,000 gallons of vinyl chloride into a creek, potentially exposing many neighborhoods to the carcinogen.