Technical guidance on normal levels of contaminants in Welsh soil : Lead (Pb) : January 2013

Lead (Pb) is a metallic element naturally occurring in trace amounts in the Earth’s surface environment with concentrations in rocks averaging 15 mg/kg. Generally, acid igneous rocks (e.g. granites) are higher in Pb than basic ones (e.g. basalts) and concentrations in sedimentary rocks are variable with up to 70 mg/kg in some limestones. With a low melting point, Pb ore minerals are readily smelted and the metal is easily worked. Lead therefore has a long history of use in human activities. In Wales there are a number of historical lead mining areas (e.g. the Mid Wales lead-zinc orefield) where there is a legacy of Pb contamination caused by mining and associated activities. Biologically it is considered as a non-essential element and toxic to man and animals through the food chain and soil dust inhalation or ingestion.