The use of leaded paint indoors and of leaded gasoline were particularly dangerous, but there are still numerous potential sources of lead exposure, especially in certain industries, but also for the average person. Exposure has decreased, but the safe blood lead level has also been reduced as we become increasingly aware of the harms of sub-clinical lead poisoning.

Two interesting properties of lead's toxicity that weren't mentioned in the article are its potency and its ability to accumulate. A blood lead level of 10 ug/dL is often listed as a threshold for concern (though for children 5 ug/dL or less is more appropriate). A typical blood volume for an adult is around 50 dL (according to Wikipedia), so 10 ug/dL would mean that there are 500 ug of lead in your blood. Lead has a density of 11.3 g/cm^3, so 500 ug has a volume of 44.2 nL. If you have every used a 2 uL pipette, you would have an idea of how small of a volume 44.2 nL is (for those who haven't, it's somewhere in the range of a grain of sand http://en.wikipedia.org/wiki/Orders_of_magnitude_%28volume%2...). Although not all the lead we ingest is absorbed and lead is distributed throughout various organs, this should give a sense of how potent of a toxin lead is. Lead is also cleared from the body fairly slowly, so the amount of exposure per day needed to build up to a toxic level is even lower. These two properties, combined with the ubiquity of lead in our society, the long timescales over which it causes harm, and widespread ignorance of or apathy towards its harms are why I find it a particularly frightening toxin.

One source that could be relevant to some in the HN crowd is electronics solder. Although Europe banned the use of lead in electronic components and solder in most applications in 2006 with RoHS, leaded solder is still mostly legal and common in the US (it looks like CA has partially adopted RoHS http://en.wikipedia.org/wiki/Restriction_of_Hazardous_Substa...). It is fairly easy to use leaded hand solder safely, but it is also entirely plausible that a child with inadequate training or supervision could ingest a significant amount of lead while soldering, from the small flakes of solder that accumulate on your workbench, dust, or lead oxides on a sponge. I had no idea how toxic lead was when I taught myself to solder in high school, and I'm glad I didn't do it much then for that reason.

I have recently started using Sn96.5Ag3Cu0.5 (lead free) solder, and although it is somewhat more expensive that leaded solder, with proper tools, plated PCBs, and correct technique it is really quite easy to use. I have some aggressive rosin-activated flux on hand (that requires cleanup) but I haven't needed to use it so far. I would highly recommend trying out Sn96.5Ag3Cu0.5, especially if you're sharing a workspace with children, who are far more susceptible to lead for various reasons.

A fair number of materials that you might encounter can contain lead as an additive, including plastic, brass, bronze, steel (http://en.wikipedia.org/wiki/Free_machining_steel), and metal/hobby/industrial/artist paints. It's always worth looking up what hazardous compounds may be present in something before putting a grinder to it (again, something I hadn't mastered in high school).

More along the lines of the article, here is another particularly egregious historical use of lead as a color in candy. In this case the compound, lead (II) chromate, also contained hexavalent chromium, another particularly hazardous chemical (http://books.google.co.uk/books?id=aC9NAAAAMAAJ&pg=PA93&dq=%...).

user:	cmatteri
created:	July 24, 2012
karma:	27