Dr Joanna Dowle (Senior Advisor, Hazardous Substances Reassessments) outlines the long and varied history of lead’s uses, despite its toxicity, and how the EPA is managing the risks from this substance.
27 October 2023
Lead was one of the first metals discovered and used by humans, with evidence of its use dating back to 6,500 BCE.
Lead is a normal part of the earth’s crust, usually combined with other elements such as oxygen and sulphur. Lead metal is easily obtained by roasting the lead ore galena (natural mineral form of lead) in hot air, leaving metal that is soft, easily worked, and corrosion resistant.
Unfortunately, it’s also highly toxic and no amount of lead is considered safe. It accumulates in the body and can lead to permanent damage of the brain and nervous system, can lead to anaemia and kidney damage, and can impair fertility or even cause death.
Lead is also toxic to plants, animals, and even micro-organisms.
How lead has been used
Civilisations throughout the ages have found many uses for lead – from plumbing to pottery glazes, and from stunning stained glass to soldering electronics in the more modern era.
Here are just a few of the ways lead has found its way into homes and affected lives over millennia.
Pipes and plumbing
The ancient Romans used lead for making water pipes and lining the channels of some aqueducts. In fact, that’s where we get our word 'plumber' and 'plumbing' from: the Latin word for lead is plumbum. That is also the reason why the chemical symbol for lead is Pb.
Ceramic glaze
The Romans used lead oxides to coat earthenware (which is a porous form of clay) with a glaze – a thin, glass-like coating which makes the ceramic waterproof. A similar technique was also used in China for more than 2,000 years. Unfortunately, if improperly fired in the kiln, the lead from the glaze could leach out of the coating.
Weights
Lead was also used as weights for weighing goods for trade, for fishing sinkers, and for leadline weights (to measure depth) and sounding weights. Lead is also still used for diving weights.
Construction materials
In medieval times, lead was used for roofing as it was resistant to fire. For example, the roof of Westminster Abbey is made of lead. In addition, lead was used for coffins, cisterns, tanks, and gutters, and for making decorative objects.
Stained-glass windows
Lead was used in the creation of stained-glass windows. The metal that holds the coloured glass pieces is lead, which is why these windows are also often called leadlight windows.
Printing presses
In the fifteenth century, one of history’s greatest advancements was possible in part due to lead – the printing press used moveable type made of a lead alloy.
Soldering electronics
In modern times, lead was used in solder to create permanent bonds between two metal pieces, which is especially useful in the manufacture of electronics. This is now banned.
Petrol additive
A compound of lead – tetraethyl lead – was used for many decades as an additive in petrol to boost vehicle performance and fuel economy. This is now banned.
Lead-acid batteries
Lead is currently used in lead-acid batteries, like the one in your internal combustion engine car.
Toxic beauty
Pigments containing lead, especially white lead, have been used in cosmetics since ancient times.
This seems horrifying given what we now know about its toxicity, but white lead make-up was used extensively in various cultures to achieve a highly prized pale complexion. Other lead pigments were also used in various cosmetics, including lipstick, rouge, and eyeliner.
Even though lead toxicity has been known for a long time – the first written account of lead poisoning dates to the 2nd Century BCE – lead-based creams and makeups made their way onto the dressing tables of women well into the 19th and early 20th centuries.
Recipe for disaster?
Lead white is the synthetic lead carbonate hydroxide (or basic lead carbonate) and it is one of the oldest synthetic pigments. It has been made since antiquity using a process later named the ‘stack’ or ‘Dutch’ process.
In this process, thin sheets of lead were placed in jars over acetic acid (that is, vinegar) vapours in the presence of moisture and carbon dioxide. This was usually done by surrounding the jars in fermenting matter such as horse manure or waste grape skins, which give off the required carbon dioxide and moisture, and also provide a constant source of heat.
The action of the acetic acid on the thin metal causes a chemical reaction, leaving a white deposit of basic lead carbonate. The white 'mould', as it’s often called, is scraped off, dried, ground into a powder and sold as lead white, or flake white.
Painting with poison
Lead-containing paint is known to have been used as far back as the 4th Century BCE.
Pigments such as chrome yellow (lead chromate), red lead (lead oxide), and white lead (lead carbonate) can be added to paints to give them colour, but lead is also added to help drying or as a corrosion inhibitor.
Various lead-containing pigments were widely used as artist’s paints, house paints, and industrial paints well into the 20th Century.
Red lead, in particular, has superb anti-corrosion properties to stop rust forming. For this reason, it has been used extensively for priming structural steel work, such as with bridges.
When part of the surface coating, lead is encapsulated and safe. Unfortunately, the production, use, and decomposition such as weathering, peeling, or chipping of lead paint releases lead into the air, dust, and soil. From there, people and the environment can be exposed to lead.
As lead toxicity became better understood, it was banned from various uses.
In the 1970s, most international jurisdictions banned lead as a key ingredient in all paints.
Unfortunately, lead paint can still be found in older houses built prior to the ban. This means any renovations undertaken on houses from that era must be done so with extreme care.
Painter's madness
Many great artists, including Michelangelo, Caravaggio, van Gogh, and Frida Kahlo, displayed a variety of mental disorders.
Today, we believe some may be due to lead poisoning from continual exposure to lead-containing paints.
Sometimes called 'painter’s madness', lead poisoning affected not just the great masters, but anyone exposed to lead paint.
Red lead bridges
Bridges are one major type of infrastructure that have historically used large amounts of red lead paint.
One estimate suggests 90 tonnes of red lead primer were used on the Sydney Harbour Bridge.
The red lead used on the Golden Gate Bridge was chosen by the architect for its striking colour, which he thought blended well with the natural setting.
Spotting a forgery
In 2015, pigment analysis on a painting similar to the portrait above by New Zealand painter Gottfried Lindauer, revealed a forgery.
Assumed to have been painted by Lindauer, who died in 1926, the analysis revealed a lack of lead, which the painter routinely used in his other paintings.
More importantly, the white pigment titanium dioxide was also found, which was only available from the 1930s.
Levelling down
The group standards that manage surface coatings and colourants in New Zealand have limits on how much trace lead can be in paints.
However, the current limits are still too high for comfort. We are proposing to update these group standards to further reduce the allowable lead levels in paint, down to 90 ppm. This will bring us in line with other international regulators such as Australia, Canada, and the US.
This low limit is considered by the World Health Organisation and the United Nations Environment Programme as technically achievable.
We also propose to remove exclusions to the lead limits, tighten testing requirements, and introduce the same lead limits into the corrosion inhibitors group standards.
Learn more about how we manage risks from lead
Lead is not permitted in any cosmetics, which are regulated under the Cosmetic Products Group Standard.
Paints are regulated by the EPA, but always remember that paints (even without lead) can be harmful for you.
Author bio
Dr Joanna Dowle did her PhD in marine natural products chemistry at Victoria University of Wellington, followed by two post-doctoral studies in peptide and protein synthesis at the University of Chicago and the University of Auckland.
Joanna joined the EPA in 2020 and is currently a Senior Advisor in the EPA’s Hazardous Substances Reassessments Team. She is leading the EPA’s project to reduce the trace lead levels allowed in paints.