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Lead toxicology

Lead is a highly toxic poison that affects most body systems,

resulting in death at high exposures, and a range of adverse

physiological and behavioural impacts at lower exposures.

There is no safe threshold of exposure. Unlike many other trace

metals it has no physiological function. It acts as a neurotoxin,

affecting multiple aspects of animal (and thus human)

behaviour and causing brain damage at low levels of exposure

in the absence of other symptoms. Developing individuals

(children) are particularly at risk (Flora

et al.


Its physical properties


density, malleability, low melting

point, tensile strength and resistance to corrosion in particular

– together with availability and relative cheapness, has meant

that the metal has long been of value to human society.

Indeed, our word‘plumbing’derives from the lead’s Latin name


owing to its use in Roman water supply systems.

Lead in antiquity

The history of environmental pollution by lead is as long

as its history of use by human society (Settle and Patterson

1980, Hong

et al.

1994, Hernberg 2000). Both the Egyptians

and Hebrews used lead and the Phoenicians mined the ore

in Spain


2,000 BCE. Hernberg (2000) notes the earliest

written account (on an Egyptian papyrus scroll) as a record

of homicidal use of lead compounds. Two thousand years

ago, lead was in wide and regular use by the Greeks and

Romans given its ready accessibility as a by-product of silver

production, and the practical consequences of its physical

properties. Significant lead production commenced



years ago with the discovery of smelting techniques for lead

sulphide ores (galena). Its geological co-occurrence with silver

(of significance for coinage) resulted in an increasing extent

of lead production over the next 2,000 years, with mining

and smelting in Spain representing c. 40% of worldwide lead

production during Roman times (Hong

et al.

1994). Roman

production has been estimated at 60,000 tonnes per annum

for 400 years (Hernberg 2000). The environmental emission of

air-borne lead particles from these early Roman mining and

smelting activities have given a record of changing deposits

not only within the Greenland ice-cap (the first evidence of

anthropogenic hemispheric-scale lead pollution (Hong

et al.

1994)), but also in wetlands across the whole of Europe (Shotyk

et al.

1998, Renberg 2001). The source has been isotopically

distinguished from naturally occurring emissions sources such

as sea spray and volcanic eruptions.

Archaeological evidence exists to demonstrate both the

significant contamination of local environments with lead (



et al.

2014), and the toxicity resulting from production

and some aspects of use (Waldron 1973, Retief and Cilliers 2005

and references therein). Indeed, the risk of acute poisoning

had been recognised by Pliny the Elder in the first century CE:

“While it is being melted, all the apertures in the vessel should

be closed, otherwise a noxious vapour is discharged from the

furnace, of a deadly nature, to dogs in particular.”

Pliny noted

that lead poisoning was common among shipbuilders, whilst

Dioscerides – a physician in Nero’s army in the same period –

observed that “Lead makes the mind give way.”

The main uses of lead at this time were for plumbing; for

domestic utensils made from lead and pewter (an alloy of lead

and tin) or use of pottery with lead glazes; and as a sweetener

used in the production and storage of wine. Lead plates were

dipped in wine during fermentation to counter-act the acidity

of grape juice, and lead acetate (“sugar of lead”) added to

sweeten the taste. Use of lead-lined storage vats also resulted

in significant concentrations within wine (Waldron 1973,

Needleman and Gee 2013).

There is no doubt that there was significant exposure to lead

frommultiple sources in Roman society. However, the extent to

which chronic exposure to lead was significant in the collapse

of the Roman civilisation remains academically contested and

has been reviewed by Gilfillan (1965), Nriagu (1983) and Retief

and Cilliers (2005) among others.

Global lead production fell with exhaustion of Roman lead

mines around 2,000 years ago leading to parallel declines in

lead concentrations in Greenland ice and European wetlands,

presumably related to reduced smelting activity (Settle

and Patterson 1980, Hong

et al.

1994, Shotyk

et al.


Renberg 2001).

Regulation of some sources of lead poisoning