Poisoning - Lead Exposure

Introduction

A 3-year-old boy is brought to the emergency department by the paramedics for seizures. The parents narrated that they noticed a decrease in the child’s appetite for several days now and that he was not playing as much with his siblings as before. There was no history of previous seizures. He had no signs of infection except for the occasional cough. The possibility of head trauma preceding the seizure seemed unlikely by history. He requires 2 IV anticonvulsants to terminate and control the seizure activity.

Although you are contemplating infectious meningitis and managing the child in that line, should toxic ingestion or exposure also be considered as a differential diagnosis in this case?

Lead is a well-known metal used in the manufacturing of various industrial products. It is also, however, a deleterious substance and subtle poison. Table 1 enumerates the known sources of lead.

Table 1: Sources of childhood lead poisoning

Environmental sources

• Antique toys, cribs, or furniture
• Contaminated foodstuffs: homegrown vegetables, imported spices, calcium supplements, flour
• Cosmetics (eg, kohl, surma, ceruse)
• Crafts (ceramic glazes, paint pigments, stained glass–making materials)
• Decorative exterior home features (eg, ‘‘pewter-look’’ fencing) Drinking water (especially first morning draw, hot water)
• Dust
• Folk remedies (eg, litarigio, greta, azarcon, alkohl, bali bali, coral, ghasard, liga, pay-loo-ah, reuda)
• Herbal products Imported toys, crayons Imported ceramics or pewter Imported soldered pots, kettles Methamphetamine
• Moonshine whiskey
• Paint
• Plaster, putty
• Soil

Exposures from activities

• Burning painted wood
• Hobbies (eg, target shooting, stained glass making, glazing pottery)
• Home renovation
• Occupations (eg, auto repair, mining, smelting, demolition, battery manufacture, remodeling, construction, painting, pipe fitting, plumbing, shipbuilding, welding, bridge reconstruction, firing range instructors)

Reference: Woolf AD, Goldman R, Bellinger DC: Update on the Management of Childhood Lead Poisoning. Pediatr Clin N Am. 2007; 54: 271-294.

Clinical Presentation of Lead Poisoning

The symptoms of lead poisoning in children were first reported in 1892 in Australia. To date, research and interest in lead poisoning have increased, particularly with regards to its varied yet non-specific clinical presentations, especially in children. The effects of lead toxicity are recognized to be multi-systemic. In children, the organ systems that are more commonly adversely affected are the central nervous system and the hematopoietic or hematologic system. Lead is known to be absorbed through the gastrointestinal tract by ingestion, through the lungs by inhalation, and through the skin by surface contact. Absorption through the intestinal tract by oral ingestion is the predominant and more common route for the pediatric population, especially for young children (1-6 years) and children or individuals with developmental challenges, who demonstrate and exhibit hand-to-mouth behavior and in who risk of exposure to lead is higher. Rates of gut absorption are also dependent on the nutritional status of the individual. Lead absorption through the intestinal tract increases when dietary intake of iron, calcium, phosphorus, or zinc is low.

Neurologic and Neurodevelopmental Findings and Symptoms of Lead Poisoning in Children

The developing nervous system in the pediatric population makes it more sensitive and susceptible to lead-induced damage and injury. Early and more common non-specific neurologic symptoms of lead exposure and poisoning in children are headache, irritability and labile mood, behavioral changes, hyperactivity or decreased activity, delay or loss of developmental milestones, hearing and speech problems, and poor attention span. More significant exposure to lead may cause symptoms in children that are more likely to lead to a medical evaluation, such as headache, ataxia, somnolence, signs indicative of increased intracranial pressure and intracranial hypertension, lethargy, seizures, status epilepticus, stupor, and even coma.

Hematologic Findings and Symptoms of Lead Poisoning in Children

There are 3 well-recognized deleterious effects of lead on the hematologic and hematopoietic systems of children: 1) disruption of heme synthesis; 2) reduction of circulating levels of hemoglobin; and 3) microcytic hypochromic anemia. These 3 adverse effects result from the disruption and inhibition of the hematopoietic processes by lead.

Lead poisoning has neither pathognomonic symptoms nor typical clinical findings. When symptoms do occur, they are usually nonspecific. It would be prudent to consider lead poisoning whenever a small child presents with peculiar symptoms that do not match any particular disease entity.

Evaluation and Assessment

Lead screening typically starts at age 6 months to 12 months. Lead screening guidelines vary regionally, but the recommended minimum screening is at 1 and 2 years. The CDC and the American Academy of Pediatrics recommend that children under age 6 be tested for lead if they:

• Live in or regularly visit a house or daycare center built before 1950
• Live in or regularly visit a house built before 1978 that has been remodeled in the last six months
• Have a brother, sister, housemate or playmate who is being treated for lead poisoning
• Live with a parent whose job or hobby involves exposure to lead
• Live near an active smelter, battery recycling plant or other industry likely to release lead into the air
• Have been seen eating paint chips or dirt
• Have low levels of iron in the blood (anemia)
• Have never been tested for lead

Table 2 discusses the guidelines for questions to ask regarding a child’s environmental history.

Table 2: Guidelines for questions to ask regarding a child’s environmental history

Paint and soil exposure

• What is the age and general condition of the residence?

• Is there evidence of chewed or peeling paint on woodwork, furniture, or toys? How long has the family lived at that residence?

• Have there been recent renovations or repairs in the house?

• Are there other sites where the child spends significant amounts of time? What is the character of indoor play areas?

• Do outdoor play areas contain bare soil that may be contaminated? How does the family attempt to control dust/dirt?

Relevant behavioral characteristics of the child

• To what degree does the child exhibit hand-to-mouth activity? Does the child exhibit pica?
• Are the child’s hands washed before meals and snacks?

Exposures to and behaviors of household members

• What are the occupations of adult household members?
• What are the hobbies of household members? (Fishing, working with ceramics or stained glass, and hunting are examples of hobbies that involve risk for lead exposure.)
• Are painted materials or unusual materials burned in household fireplaces?

Miscellaneous questions

• Does the home contain vinyl mini-blinds made overseas and purchased before 1997?
• Does the child receive or have access to imported food, cosmetics, or folk remedies?
• Is food prepared or stored in imported pottery or metal vessels?

Reference: Managing Elevated Blood Lead Levels Among Young Children: Recommendations from the Advisory Committee on Childhood Lead Poisoning Prevention, March 2002.

Blood Lead Levels in Children

The recommended and most commonly used diagnostic test is the concentration of lead in whole (venous) blood.

Experts now use a reference level or “blood lead level of concern” of 5 micrograms per deciliter to identify children with blood lead levels that are much higher than most children’s levels. The recommendation was based on a growing number of scientific studies that show that even low blood lead levels can cause lifelong health effects. This reference value is based on the 97.5th percentile of the National Health and Nutrition Examination Survey (NHANES)’s blood lead distribution in children. The current reference value is based on NHANES data from 2007-2008 and 2009-2010. CDC will update the reference value every 4 years using the two most recent NHANES surveys.

Poisoning - Management

Managing Elevated Blood Lead Levels Among Young Children

The recommendations from the Advisory Committee on Childhood Lead Poisoning Prevention (ACCLPP) are detailed in Table 3. Important Note from CDC: This document refers to a blood-lead level of 10 micrograms per deciliter (µg/dL) as the CDC level of concern for adverse health outcomes in children. This terminology is outdated and readers are referred to the ACCLPP recommendations of 2012. However, the 2012 document does not recommend changes to the guidelines for the evaluation and treatment of children with BLLs = 15 µg/dL or those requiring chelation (BLLs = 45 µg/dL) published here.

Nutritional Management

Managing a child’s nutrition, particularly when elevated blood lead levels are noted, is imperative. Since adequate stores of calcium, iron, phosphorus, and zinc decrease the gut absorption of lead, despite exposure, appropriate intake of food and sources of these minerals is indicated. The following are the guidelines for nutritional management in children with elevated blood lead levels:

• Consumer adequate amounts of bioavailable calcium and iron
• Consume at least 2 servings daily of foods high in vitamin V, such as fruits, vegetables, and juices
• Eat in areas that pose a low risk for lead exposure.
• Participate in a special supplemental nutrition program.

Follow up blood lead monitoring

Table 4: Schedule for Follow-up Blood Lead Testing

Chelation Therapy

Table 5 enumerates and briefly describes the commonly used chelation agents in the management of lead poisoning. While chelation therapy is considered the mainstay in the treatment of children with elevated blood lead levels (=45 µg/dL), caution must be observed, and consult with relevant experts is strongly recommended.

Table 3: Recommended actions based on Blood Lead Levels (BLL)

Table 4: Schedule for Follow-up Blood Lead Testing

Table 5: Medicines used to treat childhood lead poisoning

2.3-dimercaptopropanol; British anti-Lewisite, dimercaprol

• Only given parenterally (intramuscular)

• Usual dose is 75 mg/m2 body surface area every 4 hours

• Dissolved in peanut oil

• Contraindicated in children allergic to nuts or those who have glucose-6-phosphatase deficiency

• Can cause kidney dysfunction or zinc depletion

Calcium disodium ethyleneaminetetraacetate; edetate disodium calcium

• Only given parenterally (intramuscular or intravenous)

• Usual maximum dose is 1000 mg/m2 body surface area/d

• Can cause kidney dysfunction

DMSA

• Comes as 100-mg capsules only

• Usual dose is one to four capsules, depending on child’s weight, given three times daily for 5 days, then twice daily for 14 days

• Can cause elevated liver enzymes (uncommon) or skin rash (uncommon)

• Contraindicated in children who have hepatic insufficiency or those who have ongoing exposure to lead

• Capsules should be aired out before contents are mixed with food

D-penicillamine (3-mercapto-D-valine)

• Available as 250-mg capsule or tablet

• Do not give with milk, milk products, or iron supplements

• Give in juice or jelly on an empty stomach

• Often causes mild upset stomach or loose stools

• Can cause skin rash or zinc/iron depletion (common) or kidney or marrow dysfunction (uncommon)

• Usual dose is 10 to 15 mg/kg/d

• Contraindicated in children who have renal insufficiency or ongoing exposure to lead

• Capsules should be aired out before contents are mixed with food

Information for Parents

Parents and families may check the following link for helpful information and education on lead exposure and the prevention of lead exposure: http://www.cdc.gov/nceh/lead/parents.htm