Toxicity of lead

Lead salts are extremely toxic. The ingestion of a soluble lead salt can cause acute poisoning, and long-term exposure to a source of the metal (e.g. old water pipes, Pb-based paints) may result in chronic poisoning. Organolead(IV) compounds such as Et₄Pb, used as an anti-knock additive to leaded motor fuels, attack the nervous system. In a relevant piece of research, analysis of wines produced between 1962 and 1991 from grapes grown in roadside vineyards has shown some correlation between a decrease in Pb content and the introduction of unleaded fuels. Sequestering agents such as [EDTA]^4- are used to complex Pb²⁺‏ ions in the body, and their removal follows by natural excretion. Joints between metals, including those in electronic components, have traditionally used SnPb solders. However, in the European Union, new environmental legislation aims to phase out this use of lead by 2006 or 2007; a move to lead-free solders is also being made in Japan and the US. Eutectic SnPb solder exhibits many desirable properties(e.g. low melting, easily worked and inexpensive) and it is a challenge for research and development initiatives to find alloys for lead-free solders that replicate these properties. Solders based on Sn with Ag, Bi, Cu and Zn as alloying metals are the most promising candidates, and of these SnAgCu (3–4% by weight of Ag and 0.5–0.9% by weight of Cu) solders are the front runners for use in the electronics industry.