Setting the PVC Record Straight

Setting the PVC Record Straight

I have worked in the PVC industry for nearly 30 years and feel strongly about the misinformation concerning PVC that appeared earlier this year in

Environmental Building News. Our industry is determined to be a good neighbour, committed to minimising environmental impact, and dedicated to providing good, long-life products. Just as important, we are committed to making sure our products are accurately portrayed in the media. Here are some items that need clarification.

While the mercury cathode cells used to produce vinyl chloride monomer can cause major pollution problems, the majority are operated at acceptable government standards. The cost of replacing such modern technology would be enormous, without any significant environmental improvement.

You suggest that chlorine was initially an unwanted by-product of caustic soda production. In fact, early alkali production, from soda ash, was intensely polluting. The electrolysis process replaced older processes, producing alkali and chlorine for which there were already established markets.

You mention the toxic by-products of VCM production, but you provide no data on the quantities or fate of these by-products. There are by-products from most chemical processes, but this is a concern only if they have a significant impact on people and the environment. A recent study at our plant in Rafnes, Norway, found that the production of 850,000 tonnes of VCM also produced 6 grams of dioxins, only 0.934 grams of which were actually emitted to the air or water. This compares with 20 grams or so emitted from wood-burning stoves during the same period.

Your history of the PVC industry states that polymerisation was done in “open vats.” This misinterprets a common industry expression—“open autoclave.” VCM polymerisation has always been carried out in pressure vessels, and worker exposure only occurred between batches when autoclaves were open for cleaning. Since the 1970s, when the carcinogenicity of VCM was identified, a great deal of energy, expertise and money has been directed to “closed autoclave” technology, which eliminates opening the autoclave so workers are no longer at hazard from VCM exposure.

As to plasticisers, you say that the use of DEHP in PVC for medical devices was suspended in 1987 because it was suspected to be a carcinogen. You failed to record that has not been confirmed. DEHP is still the plasticiser of choice.

There are proper concerns about heavy metals going to incinerators or landfills. PVC represents only 10% of the 7-8% of plastics in MSW, and the vast majority of that is packaging waste where heavy metals are not used. Disposal of long-life applications in landfills brings no significant leaching of heavy metals.

Regarding dioxin, no special precursors are needed to produce dioxins. All that is necessary is to subject a mixture of carbon, hydrogen, oxygen and chlorine to high temperature and then cool slowly: dioxins will be produced—albeit in small quantities. Which is why barbecues in your yard produce dioxins, as do wood-burning stoves—in Denmark, about as much as MSW incinerators. Therefore, the “convincing but not definitive” evidence of health effects should include any source of dioxins and certainly include “natural” processes as well as industry.

As to accidental fires, the evidence is that the killer in most accidental fires is odourless, tasteless carbon monoxide. Hydrogen chloride has about the same toxicity as carbon monoxide but is detectable by humans at concentrations far below danger levels and gives a very strong warning of fire. Moreover, temperatures high enough to decompose the DEHP used in wire insulation also decompose PVC, and humans cannot survive at those temperatures with or without a fire.

In the case of recycling, PVC can and is being recycled. There are well-established pilot projects for recycling bottles, flooring, cable insulation and windows. The main problem is that the supply of material to recycle is limited because most PVC applications are long-term.

Concerning the individual criticisms of such long-proven products as PVC pipe, siding, electrical insulation, flooring and windows, I could point out the merits at length of each one. However, the point is that in each of these applications, strict guidelines exist for their use. Further, these products have been field-tested for years, and their success with architects, builders and building and home owners testifies to their effectiveness and value.

Thank you for the opportunity to set the record straight on these issues. I hope in the future, as your readers continue to make decisions about the building products they recommend and use, they will consider the value, durability and proven environmental performance of PVC products. I will be happy to provide additional information or answer any questions you or your readers have regarding the PVC industry and the products it makes.

John Baldwin

Manager, Environmental Affairs

Hydro Polymers Ltd., Aycliffe

England