Plastics Society's Tin Ear: Conflict Minerals in Building Materials

James Vallette | February 07, 2012 | Materials

My primary work here in the Pharos Project is to figure out what's inside building materials. Often this research takes me into unexpected territory. A recent look into the manufacturing process of flooring finishes brought my attention to the compound stannous octoate. Examining its life cycle chemistry led me into a virtual tour of a very bleak place: the artisanal cassiterite mines of war-ravaged Congo.

Stannous octoate is a substance that can contain materials mined from hell on earth. It is based on tin, and tin comes from the smelting of cassiterite, some of which originates from mining operations that fuel conflict in eastern Congo. Some of this tin winds up in cell phones, car parts, and yes, building materials such as spray polyurethane foam insulation and PVC flooring. Organotins are also used in anti-microbial treatments. Fire retardant treatments can contain inorganic tin chemicals.

According to ITRI, an industry research group based in the UK, the plastics industry is the largest consumer of tin chemicals, which account for about 14 percent of the global usage of tin. Almost two-thirds of tin chemicals are organotins used as either stabilizers in PVC formulations or catalysts in PVC and polyurethane production. ITRI says that 15% of the PVC stabilizer market is organotin-based. The OSPAR Commission classifies organotins as persistent, bioaccumulative, and toxic.

As a result of a 2010 law[1] requiring the Securities and Exchange Commission (SEC) to develop conflict minerals regulations for tin and other metals[2] sourced from conflict mines in eastern Congo, tin will be subject to groundbreaking "Conflict Minerals Rules" for supply chain responsibility and disclosure.

The plastics industry, through their trade association the Society for the Plastics Industry (SPI), is asking that it be exempted from these regulations.[3] This contrasts sharply with initiatives to reduce the use of conflict minerals in other industry sectors. For example, the cell phone industry is responding through initiatives like the Public-Private Alliance for Responsible Minerals Trade which plans to create "validated, certified and traced supply chain routes, to be audited using agreed-upon standards and mechanisms, for a significant portion of the gold, tin, tantalum, and tungsten supply in the eastern DRC and Rwanda by the end of 2012."

The plastics industry argues that supply chain disclosures of tin would threaten proprietary formulation and manufacturing process. Yet industry literature and patents are loaded with references to organometallic catalysts and formulations. Nor is it difficult to determine the likely composition of organometallic catalysts used in the manufacture of a plastic. Indeed HBN has done so in the past using a loaned XRF analyzer gun. You can sign up for a free webinar to learn how to use one yourself.

Supply chain awareness and transparency allows consumers and manufacturers to decide whether they want conflict minerals in their building materials. Transparency also sorts good actors from lazy actors, or worse. Absent supply chain, country-of-origin documentation, and full ingredient disclosure, consumers should assume that some of their building products contain materials that originated in the warlord-controlled mines of eastern Congo.

We know that tin chemicals are used in PVC and polyurethane production, and biocidal and flame retardant treatments. What I cannot figure out, and what the Society of The Plastics Industry does not want us to know, is where the tin comes from.


[1] The Dodd-Frank Wall Street Reform and Consumer Protection Act.

[2] Tungsten, tantalum, and gold

[3] The Society for the Plastics Industry in a November 9, 2011, letter to the SEC, says the Conflict Minerals Provisions of the Dodd-Frank Act should not cover compounds that its members produce and consume.

It asks the SEC to "explicitly exempt" catalysts, polymerization aids, and stabilizers in plastic materials and coatings "from the reporting and recordkeeping requirements of the regulation." The SPI argues their case on three grounds:

Tin is chemically transformed in the manufacture of organometallic compounds ("these substances are no longer metals or alloys thereof");

Supply chain tracking burdens would create an "onerous burden on plastics manufacturers" because there "are no reasonable mechanisms in place for the purchaser to track which region the constituents of the chemical were mined or obtained";

And, the regulation would threaten confidentiality of manufacturing processes.

The Society of the Plastics Industry argues, "because any disclosures would be part of a company's public filings with the SEC, a company in effect would be obligated to release proprietary formulation and manufacturing information regarding its products to comply with the law... The use of a specific catalytic complex in a manufacturing process typically is afforded the highest degree of confidentiality within the industry."