Lead poisoning refers to a build-up of lead in the body. These levels can take months or years to reach a dangerous level and, at worst, can be fatal.
Having first been mined in Anatolia at around 6500 BC, lead poisoning is one of the oldest work and environment hazards known to man.
Lead's negative health consequences have been known since at least the 1st century AD when the ancient Greek physician Dioscorides noted that lead makes the mind "give way." However, it was not until the end of the 20th century that scientists discovered how even minute quantities of lead can cause serious harm.
In this article, we will discuss the symptoms, diagnosis and treatment of lead poisoning. We will also look at how lead works as a poison as well as ways to minimize the risks of lead poisoning in the home.
Contents of this article:
Here are some key points about lead poisoning. More detail and supporting information is in the main article.
- Lead is a naturally occurring heavy metal
- All biological systems in the human body can be damaged by lead poisoning
- Children and the unborn child are particularly susceptible to lead poisoning
- An estimated 24 million American homes contain unsafe quantities of lead paint and/or dust
- The production of lead-based paint was banned in America in 1978
- An estimated 3 million workers in the US are at risk of toxic lead exposure
- Lead poisoning symptoms can include nausea, dizziness, reduced IQ and a strange taste in the mouth
- Some traditional medicines contain lead
- Lead prevents the normal functioning of vital enzymes
- Lead can reduce the total volume of brain tissue.
What is lead poisoning
Lead is a naturally occurring heavy metal.
Lead is a heavy metal and a particularly strong poison. It can accumulate in the body if it enters the mouth or is inhaled. Lead can also enter through splits in the skin or via mucous membranes.
Once inside the body, lead can damage all of the systems within it, including the heart, bones, kidneys, teeth, intestines, reproductive organs and the nervous and immune systems
Children, especially those under the age of 6, are particularly sensitive to lead poisoning. It can irreversibly damage mental and physical development.1
The most common sources of lead poisoning are from lead-based paint in older buildings, lead-based dust and contaminated water, air or soil.
Children are more at risk from lead poisoning for a number of reasons:
- They are more likely to pick up lead contamination from the soil and to then consume it
- They are also closer to ground level more frequently and, therefore, more at risk of breathing in dust from the floor.
Young children absorb lead in their stomach up to 10 times more readily than adults and, because their bodies are still developing, the risks are further increased.2,3
The Centers for Disease Control and Prevention (CDC) estimate that at least 24 million American homes harbor deteriorated lead-based paintwork and lead-contaminated dust. Four million of these homes contain young children.4
Children who live in less developed countries are at the highest risk of lead poisoning because legal controls on the usage of lead are not as strict as in the US.
Adults who work in auto repair shops or do home improvements can also be at risk of lead poisoning, especially if their home was built before lead-based paint was banned in 1978. An estimated 3 million workers in the US are at risk of toxic lead exposure.5
Symptoms of lead poisoning
Worryingly, the symptoms of lead poisoning do not become apparent until a dangerous amount of lead is already present in the body. Occasionally, lead poisoning can occur from a single high dose, but more often it is a gradual build-up.
Symptoms of lead poisoning vary across age groups:
Lead poisoning in children
- Slowed body growth
- Reduced IQ
- Loss of skills
- Loss of appetite and weight loss
- Abdominal pain
- General fatigue
- Hearing loss and reduction in other senses
Lead poisoning in adults
Lead poisoning can cause hallucinations.
- Abdominal pain - generally the first sign if a high dose of lead is ingested
- Raised blood pressure
- Joint and muscle pain
- Tingling, pain, numbness in the extremities
- Memory loss and decline in mental functions
- Unusual taste in the mouth (often described as metallic)
- Difficulty sleeping
- Mood disorders
- Reduction in sperm volume and quality
- Miscarriage or premature birth.
Causes of lead poisoning
Lead is a natural element found in the earth's crust. Human activity such as mining, burning fossil fuels and manufacturing has made it much more widespread and accessible.
Although it is no longer used in paint or fuel in the US, it is still present in batteries, pottery, pipes, solder, some cosmetics and roofing.
Lead as a constituent in paint was banned in 1978, but in some older residences, it may still be present. The majority of lead poisoning cases in children are due to eating old lead-based paint chips.
Brass plumbing fixtures and pipes made or soldered using lead and can release lead into tap water. Lead solder used in the manufacture of food cans is banned in the US, but is still used in some countries.
Lead poisoning from other sources
Traces of lead in the soil can remain for long periods of time.
- Soil: lead that arrived in the soil from lead-based gasoline or paint can survive for many years. Areas next to old walls or by the sides of roads can be particularly affected
- Dust: paint chips or contaminated soil can form dust particles
- Toys: old toys might have been colored with lead-based paint. Although this is illegal in the US, toys from other countries may still use lead-based paints
- Traditional cosmetics: kohl, used as an eyeliner, has been found to contain high levels of lead
- Stained glass: making stained glass involves using lead solder
- Pottery: some ceramic glazes contain lead.
Lead poisoning from traditional medicine
Although, as mentioned above, old paint chips are the most prevalent cause of lead poisoning in the US, there are other less common sources of lead; these include some traditional medicines:
- Daw tway: a digestive aid used in Thailand, containing high levels of lead and arsenic
- Ghasard: an Indian tonic
- Ba-baw-san: Chinese herbal remedy for colic in babies
- Litargirio: a peach-colored powder used as a deodorant, particularly in the Dominican Republic
- Greta (also called azarcon): a Hispanic powdered remedy for upset stomachs. It is also used to soothe teething babies. Some preparations contain 95% lead.
How lead damages the body
As mentioned earlier, lead damages every system in the body that it encounters. Here, we will discuss ways in which lead impacts enzymes and the nervous system, two of its most damaging interactions:
Lead's effect on enzymes
Much of the damage lead produces is due to an interruption in the work of enzymes - proteins that carry out multiple functions within the human body.6
Like other metals present in the body, lead binds to enzyme co-factors (helper molecules). But, whereas other metals carry out necessary roles such as switching enzymes off or on, lead binds to co-enzymes without causing the appropriate action. This can essentially prevent the enzymes from carrying out their work.
Lead negatively impacts delta-aminolevulinic acid dehydratase (ALAD) and ferrochelatase; these enzymes help form a vital component of blood called heme.
Lead's effect on the nervous system
The organ most severely effected by lead poisoning is often the brain.
The brain is the organ worst affected by lead - particularly the prefrontal cortex and anterior cingulate cortex, areas responsible for high-level functions, mood regulation and decision-making.
The barrier between the blood supply and the brain (the blood-brain barrier) protects the brain from many toxins, but lead passes easily through this protective layer.
Once in the brain, lead interferes with the development of synapses, the production of neurotransmitters and the structure of ion channels.
Lead also strips the myelin coating from nerves; this layer is essential for the successful transmission of messages.
Many neurotransmitters are hindered by lead, including glutamate in the hippocampus which is vital for learning and laying down memories.7
Lead has been found to trigger programmed cell death (PCD) in the brain. PCD is a normal function of the human body; it helps clear away old and broken cells, but, if PCD gets out of hand, fully functioning cells can be wrongly destroyed and not replaced.8
Diagnosis of lead poisoning
The American Academy of Pediatrics (AAP) recommend that children should be tested for lead levels at ages 1 and 2.
The test involves a simple prick of the finger and a blood test. If the levels of lead are over 5 μg/dL (micrograms per 100 milliliters), the doctor will recommend more regular checks. The CDC estimate that half a million children under 5 have blood lead levels of 5 μg/dL or higher.4
Testing the blood for the presence of lead is a relatively simple procedure.
The CDC and World Health Organization (WHO) state that a blood lead level of 10 μg/dL or above is a cause for concern. In adults, symptoms tend to start at 40 μg/dL or higher.
There are no safe levels of lead in the body. In other words, any lead in the body at all warrants investigation.
Other tests for lead poisoning include:
- Bone marrow biopsy
- Erythrocyte protoporphyrin (a test for iron deficiency)
- Complete blood cell count and coagulation tests
- X-ray of long bones and abdomen.
Treatment of lead poisoning
As with most types of poisoning, the first step is to identify and remove the source of the poison. If the problem is old paint, it may be best to seal in the paint rather than to chip it, sand it or burn it off, which could increase the quantities of lead in the air.
If simple removal of the lead is not enough to rectify blood levels, there are two common courses of action:
- Chelation therapy: this involves medication that binds with the lead and allows it to be passed in the urine
- Ethylenediaminetetraacetic therapy: adults with blood levels of lead above 45 μg/dL may be prescribed drugs that include ethylenediaminetetraacetic (EDTA) acid.
If there are concerns that someone has eaten a life-threatening amount of lead in one dose, the following procedures might be called for:
- Bowel irrigation: flushing out the entire gastrointestinal tract with large volumes of polyethylene glycol solution
- Gastric lavage: also called gastric suction or stomach pumping. This involves washing out the stomach via a tube inserted into the throat.
Preventing lead poisoning
If lead is present in the pipework, run the tap for 1 minute before use.
Simple measures that can help reduce the risk of lead poisoning include:
- Run water: in older properties where lead pipes or fittings are used, run the cold water for at least 1 minute before use. Do not use the hot water tap for cooking or drinking
- Avoid soil: prevent children from playing in the soil. Perhaps provide a sandbox and plant grass to cover patches of bare soil
- Diet: a healthy diet rich in calcium and iron can help lower lead absorption
- Install a filter: if water tests high for lead, consider installing an effective water filtering device, or switch to bottled water
- Washing: wash children's hands regularly to lower the risk of swallowing fragments of lead from soil and dust
- Cleaning: keep the environment as free from dust as possible. Wipe floors with a damp mop and clean surfaces with a damp cloth. This keeps the dust from lifting back into the air and being breathed in
- Containers: do not store wine, vinegar-based dressings or spirits in lead crystal decanters for long periods of time as lead can leech into the liquid
- Canned foods: avoid canned foods from other countries as some have not yet banned lead from manufacturing processes.
Recovery from lead poisoning
Adults who have experienced relatively minor lead poisoning may recover completely. As children are still developing, they may not fully recover and retain permanent IQ and attention deficits.
Other body systems such as the kidneys and nerves might also be irreparably damaged. Depending on severity, recovery can take months or years.
Wealth in the Middle Ages did not necessarily mean better health. According to research published in the Journal of Archaeological Science: Reports, the rich were more likely to be exposed to toxic heavy metals such as lead and mercury.
A new study suggests that the female hormones estrogen and estradiol may protect the brain against the toxic effects of lead. It found that young boys with higher levels of lead in their blood performed worse on cognition tests than those with lower levels, while this was not the case for girls, who appeared hardly affected by the chemical element.