Lead poisoning : Symptoms, Causes, Diagnosis , Management and Prevention

Lead poisoning : Symptoms, Causes, Diagnosis , Management and Prevention

Lead poisoning is one of the most common diseases of toxic environmental origin and accounts for about 0.6% of the global burden of disease. Lead is a naturally occurring heavy metal found in the earth’s crust.  It is soft, malleable, and melts at a relatively low temperature. It is easily moulded and can be combined with other metals to form alloys.

It is widely used in many products such as lead-acid batteries for motor vehicles, pigments, paints, solder, stained glass, lead crystal glassware, ammunition, ceramic glazes, jewellery, and toys and in some cosmetics and traditional medicines.

Mining, smelting, manufacturing and recycling activities, and the continued use of leaded paint, leaded gasoline, and leaded aviation fuel (in some countries) are important sources responsible for environmental contamination. Drinking water supplied through lead pipes or pipes joined with lead solder may contain lead. Widespread use of lead has resulted in to extensive environmental contamination and health problems in many parts of the world. Humans also suffer from lead intoxication through the food chain.

Lead is a cumulative toxicant (increasing in quantity in the body over many years) that affects multiple body systems (neurologic, hematologic, gastrointestinal, cardiovascular, and renal systems). Young children are more susceptible to toxic effects of lead and can suffer with permanent adverse effects on their health. Adults exposed to lead are at increased risk of developing high blood pressure and kidney damage. Exposure of pregnant women to high levels of lead can cause miscarriage, stillbirth, premature birth and low birth weight and malformations.

Lead has no essential role in the human body. No safe level of lead exposure has so far been established. Even blood lead concentrations as low as 5 µg/dl may result in decreased intelligence in children, behavioural difficulties and learning problems; therefore prevention from exposure is important. The phasing-out of lead from petrol is a major international public health achievement but still global consumption of lead is increasing because of increasing demand for energy-efficient vehicles.

Lead paint can cause a long-lasting hazard to health in all age groups. Since leaded paint is a continuing source of exposure in many countries, World Health Organization (WHO), along with the United Nations Environment Programme has formed the “Global Alliance to Eliminate Lead Paint”. Its broad objective is to promote a phase-out of the manufacture and sale of paints containing lead and eventually to eliminate the risks involved with such paints.

Symptoms:

Most individuals when exposed to lower levels of lead show no symptoms. When symptoms of lead poisoning appear they are non specific and cannot be differentiated. Lead can seriously affect health of children.

Symptoms may be related to gastrointestinal system, central nervous system, musculoskeletal and cardiovascular system.

  • Gastrointestinal symptoms are anorexia, nausea, vomiting, abdominal pain, constipation, metallic taste. The combination of recurrent or intermittent abdominal pain, vomiting and constipation is commonly known as lead colic and should raise the suspicion of lead poisoning.
  • Central nervous system-Lead affects children’s brain development resulting in reduced intelligence quotient (IQ), behavioural changes such as reduced attention span and increased antisocial behaviour, poor concentration, headache, fatigue, malaise, language and speech delay. High levels of exposure can cause ataxia, seizure, coma even death.
  • Children who survive severe lead poisoning may be left with mental retardation and behavioural disorders.
  • The neurological and behavioural effects of lead are irreversible.
  • Musculoskeletal – Muscle and joint pain (chronic)
  • Other chronic effects -Short stature, weight loss, weakness

Physical examination –

  • Signs of increased intracranial pressure, lead lines in teeth, hypertension (high blood pressure) may be present.
  • Studies have shown that blood lead levels as low as 5ug/dL may result in adverse pregnancy outcomes, including spontaneous abortion, premature birth, stillbirth, birth defects, and decreased intellect and/or behavior problems in the child.

Causes:

Lead is a heavy metal with a bluish-grey colour. It has a low melting point, and can be combined with other metals to form alloys. It is widely used in products such as pipes; storage batteries; pigments and paints; glazes; vinyl products; weights, shot and ammunition; cable covers; and radiation shielding.

Lead used for these purposes come from mined ores (primary) or from recycled scrap metal or batteries (secondary). Today, most of the lead in global commerce is secondary and is obtained from recycling lead-acid batteries. Improper recycling of used lead batteries causes environmental pollution and health damage.

People can get exposure to lead mainly through inhalation and ingestion.

  • Inhalation of lead particles generated by burning materials containing lead, for example, during smelting, recycling, stripping leaded paint, and using leaded gasoline or leaded aviation fuel; and air pollution by smoke arising from the open burning of waste and can transport lead for long distances.
  • Ingestion of lead-contaminated dust, water (from leaded pipes), and food (from lead-glazed or lead-soldered containers), food chain.

The use of some traditional cosmetics and medicines can also result in lead exposure.

Young children have a higher risk for exposure because they have frequent hand-to-mouth activity, and they absorb lead more easily than do adults.

Toys are important source of children’s exposure to lead. Lead is a problem in toys for two reasons: (a) the toy may be painted with leaded paint; and (b) the toy itself is made of lead.

Children who work as scavengers, street vendors, car repairers and ship dismantlers are at increased risk of lead poisoning. (These children may also suffer from nutritional deficiencies, which further enhances the adverse effects and increases the absorption of lead).

An enormous amount of electronic waste is generated each year worldwide and large numbers of workers involved in separating lead, mercury and other metals from the waste for recovery and recycling are exposed to lead.

Lead stored in bones is released into blood during pregnancy and becomes a source of exposure to the developing foetus. Pica during pregnancy can cause maternal and fetal exposure to lead.

Workers (in industries that use lead) can bring home lead-laden dust on their clothes, shoes and vehicles, resulting in contaminated dust in their homes can cause lead poisoning in the spouses and children.

Lead paint that is peeling, chipping, chalking or cracked is a health hazard.

Diagnosis :

Symptoms of lead poisoning are not specific. The diagnosis of lead poisoning can be suspected if possible source of exposure to lead is found during routine questions such as peeling paint in old housings combined with such behavior in children as pica, chewing on surfaces, and placing nonfood items in the mouth or proximity to open burning of waste or recycling of car batteries. Symptoms may be absent in spite of significant poisoning. Routine assessment of nutritional and developmental milestones is performed in children.

Environmental investigation is carried out to identify potential sources of lead exposure.

Laboratory investigation-

Blood lead level (BLL)- Human exposure is usually assessed through the measurement of lead in blood.
Haematology – Hypochromic anaemia, red blood cells with basophilic stippling, elevated protoporphyrin levels (erythropoietic protoporphyria (EPP) or zinc protoporphyrin (ZPP)
Liver Function test shows  elevated transaminase levels (acute poisoning),
Other -Hyperuricaemia, hypocalcaemia
Urine -Proteinuria, glucosuria and aminoaciduria (acute poisoning)

Radiological investigation shows lead lines in the metaphyses of long bones (chronic poisoning).

Management :

Medical interventions and treatments vary depending on the confirmed blood lead level. Simply avoiding exposure to lead might be enough to reduce low levels of lead in blood.

In more severe cases chelation therapy is recommended. In this treatment a medication given by mouth / injection binds with the lead so that it’s excreted in urine. (While chelating agents can bind to lead in blood, they are ineffective in removing lead from the deep bone stores).

Nutritional counseling is given about intake of foods containing calcium, iron and vitamin C. (Adequate iron is required to decrease lead absorption. Foods high in calcium will help to maintain adequate calcium bone stores and lead will not get stored in bones. Vitamin C is needed for the absorption of iron. Children with empty stomach absorb more lead than children with full stomachs).

Prevention:

Prevention is the best way to deal with lead poisoning. Protecting children from exposure to lead is important to lifelong good health. No safe blood lead level in children has been identified, even low levels of lead in blood have been shown to affect intelligence quotient (IQ), ability to pay attention, and academic achievement. The effects of lead exposure cannot be corrected. The most important step parents and others can take is to prevent lead exposure before it occurs (primary prevention).

Further efforts are required to continue to reduce the use and release of lead to reduce environmental and occupational exposures, particularly for children and women of child-bearing age. Interventions include eliminating non-essential uses of lead such as lead in paint, ensuring the safe recycling of lead-containing waste, educating the public about the importance of safe disposal of lead-acid batteries and computers, and monitoring of blood lead levels in children, women of child-bearing age and workers.

Secondary prevention focuses on the early detection of lead poisoning. Secondary prevention strategies work to reduce the effects of lead in patients with identified elevated blood lead levels (EBLL’s).

World Health Organization (WHO) and the United Nations Environment Programme jointly initiated the “Global Alliance to Eliminate Lead Paint” to achieve international goals to prevent children’s exposure to lead from paints containing lead and to minimize occupational exposures to lead paint. Its broad objective is to promote a phase-out of the manufacture and sale of paints containing lead. International Lead Poisoning Prevention Week provides an opportunity to mobilize political and social commitment for further progress.

Health tips to prevent lead exposure-

  • Women should be counseled about effects of pica during pregnancy.
  • Children should get a healthy diet sufficient in Iron, calcium and vitamin C and should get four to six small meals during the day.
  • Take shoes off at the door. Lead can be brought into the living space from outside areas on shoes.
  • Hand washing is a simple yet very effective preventive measure, especially during a young child’s crawling and hand to mouth stage.
  • Provide (lead) safe toys and items to infants and toddlers.
  • Child play area and toys should be cleaned regularly.
  • If a family’s home has lead pipes, use initial water from pipes for other purposes (watering plants or flush toilets) before the first morning use.

References :

www.who.int/mediacentre/factsheets/fs379/en/

www.who.int/ipcs/lead_campaign/ILPPW_ (#BanLeadPaint)

www.who.int/ipcs/assessment/public_health/lead/en/

www.who.int/ceh/publications/leadguidance.pdf

www.who.int/mediacentre/news/notes/2013/lead

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