Scrap lead

Lead

Lead is great stuff. It’s ductile and malleable, and it resists corrosion. Quite a lot of it is used on the roof of my house, where it’s been folded into all kinds of odd shapes to keep the rain out of various nooks and crannies. The low melting point of lead is also useful if you’re soldering, and if added to petrol in the form of tetraethyl lead, it reduces engine knock and valve seat wear. Lead in ceramic glazes makes good, bold reds and yellows, and in paint it speeds up drying, increases durability and resists damage from moisture. Elsewhere, the density of the metal is useful, such as in making bullets, sailing boat keels or radiation shields.

What’s not to like?

Apart from the blood, nerve and brain disorders, the kidney damage, abdominal pains, muscle weakness, high blood pressure, anaemia, constipation, miscarriage, mood disorders, infertility, delayed puberty, learning disabilities, memory loss and reduced cognitive ability.

Apart from that, it’s great stuff.

Worryingly, when so much lead can be found in children’s toys, it has a sweet taste. In fact, the Romans used to sweeten their wine with powdered lead, which might go a long way towards explaining Nero and Calligula. In addition to ingestion, lead can be absorbed through skin contact and inhalation. When present in soil, it tends to bioaccumulate.

Roman lead ingot

Impressive corrosion resistance: a Roman lead ingot from the 1st century BC. (National Museum of Underwater Archaeology, Spain)

The Restriction of Hazardous Substances Directive (2002/95/EC) took effect on July 1st 2006. This restricted the use of six hazardous substances, including lead: a rather slow reaction to a problem originally reported by the Greek physician Nicander of Colophon in the 2nd century BC. Still, better late than never, eh?

While the elimination of lead addresses one problem, it created several new ones for the electronics industry. The melting point for lead-free solders was higher, which increased manufacturers’ energy consumption. It doesn’t flow as readily, which can cause increased defects (and makes hand-soldering more difficult), and lead-free solder tends to be more brittle than the alloy it replaces. Also, there’s the problem of “tin whiskers” – a crystalline metallurgical phenomenon whereby short circuits can occur over time. Going ‘green’ has caused the electronics industry a lot of problems.

Interestingly, although a car mustn’t have any lead in the solder on its circuit boards, it’s likely to include as much as ten kilos of lead in the battery. This is tolerated because the recycling rate for used car batteries is so good; Earth911.com suggests that 98–99% of car batteries in the USA are returned for recycling, and a typical new battery contains 60–80% recycled material. With a good closed loop for recycling (made possible because lead is valuable enough to be worth collecting) it’s possible to continue using even this dreadfully toxic material. If only we could achieve the same recycling rates for circuit boards!

Car batteries

The lead-acid battery: invented in 1859, and still going strong.

For the tetraethyl lead that is the main reason why you have 100–500 times as much lead in your body as a person who lived before the industrial revolution, you have Thomas Midgley Jr to thank. He was the mechanical engineer who did so much to promote the use of gasoline with tetraethyl lead. That wasn’t his only gift to mankind, though: he also invented Freon, the CFC refrigerant/propellant that’s done so much to harm the ozone layer. Always a prolific inventor, when Midgley contracted polio in 1940 he invented an pulley system that would allow a carer to lift him in and out of bed.

In November 1944 it malfunctioned, and strangled him to death.

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3 thoughts on “Lead

  1. Pingback: Hummer vs. Prius: surprisingly sustainable? | Capacify

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