Lead
TXP-2
Introduction
In the 2nd century BCE, Dioscorides noted, "Lead makes the mind give way." In modern times, lead has been heavily used in paint and as a gasoline additive. Even low levels of lead exposure cause subtle brain damage in children; this was recognized and acted upon only in the last thirty years. It is now well documented that even blood lead levels below 10 µg/dL can harm the developing brain. Lead has no beneficial biological effects.
Lead is naturally present in soil and water at very low levels, but people have caused extensive distribution of lead in the environment. Lead's physical properties of low melting point, easy malleability, corrosion resistance, and easy availability make it well suited to applications both ancient and modern. It is found alongside gold and silver, making lead both a by-product and a contaminant during the smelting of these precious metals. The earliest recorded lead mine dates from 6500 BC, in Turkey.
