January 16, 2006
Lead and PVC
Lead, which is every bit as bad as Mark says it is in your body, is still the standard stabilizer for PVC (polyvinyl chloride), especially in electric cable insulation, though alternatives with somewhat inferior properties are entering the market. I hope Mark doesn't throw away all his power cords, or his computer will stop and he won't be able to blog any more.
The stabilizer in essence mops up hydrochloric acid, released by the plastic as it ages, that would otherwise accelerate the degradation of the insulation. Lead exposure from plastic has to do with the surface area of the plastic exposed, exposure to sunlight and solvent environments that cause the plastic to degrade and leave lead dust on the surface, and ingestion paths. Lead in vinyl window blinds was a concern a few years ago because of the large exposed surface area and sunlight degradation, plus the constant exposure of the blinds to children touching them with moist fingers and licking the fingers or even the blinds, and dust being blown off the surface and into the room air. Plastic toys kids could chew or lick, or a large surface-area item exposed to sun and water like a raincoat, are especially bad sorts of things to use lead stabilizer in.
While acute lead poisoning cases related to plastic have occurred, including an electrician with the habit of constantly chewing on his stripped-off insulation bits and workers in vinyl mixing plants where the stabilizer was carelessly handled, I cannot find a single case of lead poisoning, even at very low levels, traceable to normal use of electric cable. Kids need to keep electric cords out of their mouths for many reasons in any case. (The lead in this insulation does present an environmental disposal problem, which is one reason the industry is looking for alternatives.)
Note that long-term performance in electric insulation is a safety-related quality, and it would be a pity if reducing tiny lead exposures from cable resulted in increased cases of amperage overdose (200 fatal electrocutions in 1998), or of fatal heat or smoke intake in houses ignited by wiring failures (about 70,000 such fires per year).
The most important reduction in lead exposure was accomplished when we got the lead out of gasoline (how it got in is one of the most appalling stories of continuing profit-driven corporate callousness in industrial history). The next was managing exposure to lead in paint (no longer sold or used, but still powdering off the outside and inside of older houses) that will need to be pursued for decades to come. Some isolated situations like the Mexican snacks sold in Latino neighborhoods that are still poisoning children remain.
My problem with the Prop. 65 notice on my DVD drive is that such legislation causes us to strain at gnats and conceals the important differences between them and the real camels in the environmental risk arena. Lead toxicity from plastic electric wires is not an important life or health risk, and plastic cable toxicity is not an important element in lead health damage. Even safer stabilizers will be better, but I'm pretty sure the displacement of rubber/fabric and the other old-fashioned types of cable insulation by pvc has been a big net gain in safety, cost, and convenience.
The language of the initiative is:
No person in the course of doing business shall knowingly and intentionally expose any individual to a chemical known to the state to cause cancer or reproductive toxicity without first giving clear and reasonable warning to such individual, except as provided in Section 25249.10.
This has no recognition of toxicity level, carcinogenicity, concentration, dosage, or path, all of which are what matter in risk, and this kind of legislation and policy is what leads to warnings that are merely silly and dilute the important warnings of real risk that we need to pay attention to. Your automobile battery, for example, is a really big hunk of lead. It's very dangerous in at least three ways: the lead sits in a pot of acid, the battery is quite heavy and could break your toe if your drop it, and it can explode if you create a spark near it when its charging. The lead, though there's lots of it there, is a disposal/pollution concern, not a use risk in this case. Like the two-odd pounds of lead in the glass in your CRT computer monitor that kept it from giving you cancer (radiation!) all those hours you looked at it.
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Thread: Energy and Environment , Thread: Technology and Society
