Lead

Properties of Lead

Lead's key properties as a metal include:

• A low melting point

• Workability

• Corrosion resistance

• Poor electrical conduction

• High toxicity

Toxicity Properties

Lead has high toxicity. Even just 5 µg/dL of lead in the bloodstream can cause lead poisoning. Symptoms of lead poisoning include fatigue and pain. In children, it can lead to developmental delays and learning difficulties.

Neurotoxicity

Lead toxicity typically affects the CNS.

Lead neurotoxicity occurs when lead exposure alters normal CNS activity, causing damage. Symptoms can be immediate or delayed.

Liposolubility

Lead is liposoluble, meaning that it can dissolve in fats. This property allows it to enter organs such as the brain and the liver.

Bioaccumulation

Lead can build up in the bodies of animals, including humans. Over time, this can lead to lead poisoning. Unlike many pollutants, lead is not subject to biomagnification.

Lead is mostly stored in the bones, which reduces the risk of lead transmission to other animals in the food chain.

Natural Sources of Lead in the Environment

Lead occurs naturally in soils, at low rates of 10 to 50 mg/kg. Lead tends to accumulate in the upper layers of soil, closest to the surface, where it is held very tightly by particles of clay and organic matter.

Small amounts of lead in the soil can be transferred to plants – but not always. Lead availability to plants depends on how tightly it is held by soil particles and its solubility.

• In neutral soils (around pH 6.5), the lead is held tightly by the soil, and it has low solubility. It is not easily taken up by plants.

• In acidic soils (around pH 5) lead is held less tightly, and is more soluble, so it can be taken up by plants.

If lead is taken up by plants, it has the potential to be passed to any animals (including humans) who eat the plants.

Uses of Lead

Lead has been widely used since Roman times due to its corrosion resistance and workability.

Since discovering its toxicity, lead has been discontinued from a range of products:

• Pipes (including solders)

• Paint and glazes

• Insecticides

• Hair dyes

• Petrol additive

• Radiators

When storing or disposing of waste lead, the lead is kept at a high pH to reduce solubility and toxicity.

However, lead is still used in a few products. Despite its toxicity, it has some unique and useful properties.

• Car batteries often contain lead. These batteries perform better at lower temperatures than other kinds of battery. Furthermore, they're a cost-effective method for storing enough energy to start a vehicle.

• Lead's high density and ability to absorb vibrations make it an excellent shield against harmful radiation. As a result, lead is used in X-ray machines and nuclear reactors.

• High density lead linings are commonly used in the storage of corrosive liquids.

Lead Pollution in the Environment

Because of lead's widespread use for centuries, lead pollution is a significant environmental problem.

Soils can become contaminated with lead pollution from manufacturing processes, mining, burning materials containing lead, or water runoff. Water itself can become contaminated if it travels through a source of lead, such as pipes.

A notable domestic source of lead pollution is paint chips from old lead-based paint. Furthermore, some countries use lead in traditional medicine and cosmetics, such as Kohl.

Effects of Lead Pollution on the Environment

Once the environment has experienced lead pollution and contamination, it can have a range of negative effects on plants, animals, and humans.

Plants

Excess lead in the soil can cause a number of toxicity symptoms in plants, including stunted growth and chlorosis.

Lead can inhibit photosynthesis, disrupt water and mineral balances, impact seedling development, and alter the plant's hormones.

At very high lead concentrations of 10000 to 40000 mg/kg, lead can affect the soil community, killing bacteria and fungi. Many of these microorganisms have mutualistic relationships with plants.

If lead poisoning disrupts the soil community, it can have severe effects on plant growth and nutrient cycling.

Humans

Lead can enter the human body by consuming contaminated food and water, or inhaling dust or fumes that contain lead. Once in the body, it's stored in the bones and blood, giving rise to a range of unpleasant symptoms. Large doses of lead can cause pain, weakness, headaches, memory loss, anaemia, organ damage, and even death.

Unborn Babies

Lead exposure can cause miscarriage and stillbirths in pregnant women. Alternatively, it can cross the placenta and cause damage to the unborn baby's nervous system.

Children

Children are at significant risk of irreversible long-term effects of lead poisoning. In particular, lead influences brain development and reduces IQ and attention span, whilst increasing antisocial behaviour and risk of psychiatric problems in later life.

Additionally, children are more likely to ingest lead than adults. Young children regularly put objects in their mouth. Eating sweet-tasting lead paint chips is a common cause of lead poisoning in children.

Lead-based paint chips are often eaten by small children, and can easily contaminate soils. Unsplash

I hope that this article has explained what lead is and why it poses a risk for you. This highly toxic metal can contaminate the environment, leading to lead poisoning if ingested. Lead poisoning is a particular problem for children, who may experience irreversible health and developmental problems.

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