Basics
Description
- Lead poisoning is one of the most common pediatric environmental health problems, most often involving systemic intoxication with inorganic lead. Lead poisoning is an older term that is less specific than an actual blood lead level (BLL).
- The Centers for Disease Control and Prevention (CDC) considers an elevated BLL to be ≥5 mcg/dL.
- This "reference value " is based on the 97.5th percentile for lead levels of children aged 1 " 5 years collected for the National Health and Nutrition Examination Surveys (NHANES).
- This replaces the previous "level of concern " terminology for levels ≥10 mcg/dL based on the Advisory Committee on Childhood Lead Poisoning Prevention (ACCLPP) recommendations in light of many studies demonstrating cognitive and behavioral effects at BLL less than 10 mcg/dL.
Epidemiology
A recent national survey estimates that 38 million housing units have lead-based paint (1/3 of all U.S. housing).
- 24 million housing units have hazards from lead-based paint.
- ¢ ¼ 83% of American pre-1978 privately owned units contain some lead-based paint.
Prevalence
The prevalence of elevated BLLs and the geometric mean BLLs have decreased significantly in the past 20 years.
- ¢ ¼450,000 American children aged 1 " 5 years are estimated to have BLLs of ≥5 mcg/dL.
- Racial income disparities persist due to disparities in housing quality, nutrition, and access to health care.
Risk Factors
- Young children with more oral behaviors
- Children with developmental delays/mental retardation
- Children with pica
- Residence in older homes with flaking or deteriorating lead-based paint
- Renovation or remodeling of older homes without lead hazard controls in place
- Recent immigration from countries where ambient lead contamination is high (i.e., where leaded gasoline is still used)
- Use of lead-glazed ceramic pottery
- Use of traditional therapies containing lead (e.g., Azarcon, some Ayurvedic and Chinese medicines)
- Ingestion of lead-containing candies from Mexico
General Prevention
- Primary prevention: removal of potential environmental lead hazards prior to exposure
- The ACCLPP focuses on primary prevention as it emphasizes that there is no "safe " level of lead and the effects of lead are likely irreversible.
- Clinicians should provide anticipatory guidance to all parents about lead exposure pathways and the prevention of exposures.
- Secondary prevention: screening for elevated BLLs
- Minimum screening recommendations: blood lead test for children at 1 and 2 years and for those 36 " 72 months old who have not had previous screening
- Screening children immigrating from other countries and screening pregnant and lactating women and their neonates and infants for lead exposure prior to or during pregnancy and lactation
- Tertiary prevention: case management and environmental remediation for children with lead poisoning
- Control measures
- Abatement of building-based (residential) lead hazards by removal, encapsulation, or enclosure of lead-containing structures
- Control of environmental lead dust exposure and ingestion by good housekeeping (wet dusting and mopping of household dust); personal hygiene (cleaning of child 's hands, toys, personal items, wiping feet on mats prior to entering the home), and hiring certified renovators who are EPA-approved to perform renovations that may disrupt lead-based paint
- Removal of any other known lead source from the child 's environment
Pathophysiology
- Lead adversely affects many organ systems including neurologic, hematologic, GI, renal, and reproductive.
- Many toxic effects result from inhibition of enzymes involved in heme biosynthesis, as the electropositive metal binds to negatively charged sulfhydryl groups on active sites of ´-aminolevulinic acid dehydratase (ALAD), ferrochelatase, porphobilinogen synthase, coproporphyrinogen oxidase, and other enzymes.
- Divalent lead also acts competitively with calcium in various biologic systems.
- Children absorb lead more efficiently from the GI tract and are more likely than adults to ingest lead through hand-to-mouth activities.
- Because the developing, immature CNS is susceptible to toxic effects of lead, the neuropsychologic effects of lead poisoning on fetuses/young children are of particular concern. Even relatively low BLLs are associated with IQ deficits, attention-related behaviors, and poor academic achievement.
Diagnosis
History
- It is important to assess for risk factors for exposure, as most children are asymptomatic.
- Etiology/common sources of lead:
- Ingestion of lead-based paint or contaminated dust or soil through residence in or visitation of older (pre-1980), deteriorated housing
- A parental occupation or hobby involving lead exposure (e.g., construction or battery plant work, stained glass window or pottery making)
- Use of remedies, cosmetics, pottery, toys, or consumer products containing lead
- Ingestion of contaminated water, food, or beverages
- Typical symptoms:
- Most children are asymptomatic; many clinical manifestations are nonspecific. A cluster of complaints including anorexia, intermittent abdominal pain, constipation, sporadic vomiting, change in mental status (e.g., irritability or lethargy), decreased play activity, and change in developmental status (e.g., regression of developmental milestones) may herald this condition.
- Lead encephalopathy
- Can present with change in consciousness, ataxia, persistent vomiting, seizures, and coma
- Often presents after a prodrome of symptoms mentioned above
Physical Exam
As patients are generally asymptomatic, physical exam is not generally helpful at lower lead levels.
- Symptomatic and/or encephalopathic patients may have acute GI, neurologic, hematologic, and systemic manifestations.
- Assess for developmental delay.
Diagnostic Tests & Interpretation
Lab
- Blood lead test, either venous or capillary (but must be drawn in lead-free tube):
- Results may be reportable to local health authorities.
- The test result is a measure only of recent lead exposure and does not indicate total body burden of lead.
- Capillary testing is associated with more false-positive results. If abnormal, a venous lead should be sent.
- A confirmed elevated BLL is defined as a child with a venous blood sample ≥5 mcg/dL.
- CBC: to assess for anemia
- Iron deficiency anemia is often seen concomitantly.
- Anemia related to lead toxicity is typically normocytic and normochromic; a microcytic, hypochromic anemia may be seen with a mixed etiology.
- Basophilic stippling is sometimes seen on peripheral blood smear.
- Free erythrocyte protoporphyrin
- Marker of lead-induced inhibition of heme synthesis
- Can be useful clinically to follow the recovery from heme synthesis inhibition during management
Imaging
- Abdominal radiograph: Look for radiopaque foreign material suggestive of ingestion of lead paint chips or other lead-containing foreign body, when ingestion of such is suspected in the history or with very high BLLs.
- Long bone radiographs are not recommended for routine screening.
Differential Diagnosis
Consider lead poisoning as the etiology for the following diagnoses:
- Seizures, altered mental status, and/or coma
- Anemia
Alert
Failure to diagnose results from the following:
- Delay in checking a blood lead test in the presence of clinical signs, symptoms of lead poisoning, or neuropsychologic disorders
- Failure to inquire about lead exposure possibilities
Treatment
Treatment for most individuals is focused on environmental management to prevent further lead exposure. Medications are only required at higher BLLs.
General Measures
- Environmental management
- Remove children from the lead source(s).
- Should occur when venous lead levels are recurrently 10 mcg/dL (CDC class IIA) and higher; could be done for lower BLLs as resources allow
- Reduction of lead levels in the household
- Consultation with a qualified lead abatement contractor is advised.
Medication
- Chelation therapy
- Should complement environmental management in all children with venous levels of ≥45 mcg/dL using parenteral calcium disodium ethylenediaminetetraacetate (Ca-EDTA; calcium disodium versenate) or oral agents such as meso-2,3-dimercaptosuccinic acid (DMSA, succimer, Chemet)
- Chelation of children with levels <45 mcg/dL is not recommended, as evidence suggests it does not reverse or diminish neuropsychological effects of lead.
- Outpatient therapy can take place if a lead-safe environment has been identified and compliance is expected.
- Succimer is given at 10 mg/kg (or 350 mg/m2) q8h for 5 days, then q12h for 14 more days. Weekly monitoring for neutropenia, platelet abnormality, and increased liver enzymes is recommended.
- Children with symptomatic lead poisoning or with levels of ≥70 mcg/dL should be admitted immediately to a hospital for parenteral chelation with both IM dimercaprol (British anti-Lewisite, BAL) and IV or IM calcium disodium EDTA. Because there are many issues involved with administration of both chelating agents, consultation with a clinician experienced in lead toxicity treatment is advised.
- Children with encephalopathy constitute a medical emergency and should receive the preceding treatment in an intensive care setting with attentive neurosurgical support.
- Ingested lead-containing foreign bodies should be evacuated with whole-bowel irrigation using a polyethylene glycol electrolyte solution.
Issues for Referral
- Close communication with the local health department is essential before, during, and after admission.
- Referral may be made to early intervention or development assessment programs, social workers, therapists, neurologists, or other specialists, as needed.
Inpatient Considerations
Admission Criteria
Admit all symptomatic children, those with BLLs ≥70, and those with BLLs ≥45 for which one cannot ensure a lead-safe environment and/or compliance with oral medication.
Discharge Criteria
Consider discharge when symptoms have resolved, BLL has significantly declined, and a lead-safe discharge environment has been identified.
Follow-up Recommendations
Patient Monitoring
- Prompt environmental follow-up of current lead exposure situations and investigation for additional exposure (e.g., with family moves, visitation of new residences) should occur.
- Follow-up venous lead levels should be performed for those with BLLs ≥5 mcg/dL about every 1 " 3 months, with less frequent follow-up after levels decline.
- Follow-up venous levels should be performed 1 " 3 weeks following chelation therapy, with frequent monitoring thereafter until levels have decreased significantly and no new lead exposure is apparent. BLLs will increase from the nadir level immediately after treatment to rebound to a level between this and the pretreatment level.
Diet
- Nutritional support with calcium and iron supplementation should be given if intake is inadequate; deficiencies of these increase lead absorption from the GI tract.
- The recommendation for adequate intake of calcium is 500 mg/day, which can typically be achieved through a regular healthy diet.
- There is currently no evidence that supplementation of calcium beyond the recommended "adequate intake " is beneficial for children with elevated BLLs.
- Iron repletion should be initiated with 3 mg/kg of elemental iron for those children who are found to be iron deficient.
- Iron supplementation should be withheld during chelation therapy.
- Additionally, it is recommended to consume at least two servings daily of foods high in vitamin C, such as fruits, vegetables, and juices.
Prognosis
There is an increased risk for long-term neuropsychological sequelae, which increases with lead exposure and absorption that is more intense, of longer duration, and begins at an early age when the CNS is still developing.
- Recurrent episodes of symptomatic lead poisoning increase the risk for permanent sequelae.
- Subtle effects may be missed until school entry.
Complications
- Acute encephalopathy
- Seizures
- Coma
- Death (predominantly owing to cerebral edema)
- Mental retardation
- Cognitive, behavioral, attentional, and neurodevelopmental impairment
- Anemia
- Fanconi syndrome
- Abdominal colic
- Adverse reproductive outcomes
Additional Reading
- Advisory Committee on Childhood Lead Poisoning Prevention of the Centers for Disease Control and Prevention. Low Level Lead Exposure Harms Children: A Renewed Call for Primary Prevention. Atlanta, GA: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention; 2012.
- American Academy of Pediatrics Committee on Environmental Health. Lead exposure in children: prevention, detection and management. Pediatrics. 2005;116(4):1036 " 1046. [View Abstract]
- Bellinger DC. Very low lead exposures and children 's neurodevelopment. Curr Opin Pediatr. 2008;20(2):172 " 173. [View Abstract]
- Binns, HJ, Campbell C, Brown MJ. Interpreting and managing blood lead levels of less than <10 microg/dL in children and reducing childhood exposure to lead: recommendations of the Centers for Disease Control and Prevention Advisory Committee on Childhood Lead Poisoning Prevention. Pediatrics. 2007;120(5):e1285 " e1298. [View Abstract]
- Canfield RL, Henderson CR Jr, Cory-Slechta DA, et al. Intellectual impairment in children with blood lead concentrations below 10 microg/dL per deciliter. N Engl J Med. 2003;348(16):1517 " 1526. [View Abstract]
- CDC response to Advisory Committee on Childhood Lead Poisoning Prevention Recommendations in "Low Level Lead Exposure Harms Children: A Renewed Call for Primary Prevention. "
- Centers for Disease Control and Prevention. Guidelines for the Identification and Management of Lead Exposure in Pregnant and Lactating Women. Atlanta, GA: Centers for Disease Control and Prevention; 2010.
- Centers for Disease Control and Prevention. Preventing Lead Poisoning in Young Children. Atlanta, GA: Centers for Disease Control and Prevention; 2005.
- Lanphear BP, Hornung R, Khoury J, et al. Low-level environmental lead exposure and children 's intellectual function: an international pooled analysis. Environ Health Perspect. 2005;113(7):894 " 899. [View Abstract]
- Lanphear BP, Matte TD, Rogers J, et al. The contribution of lead-contaminated house dust and residential soil to children 's blood lead levels. Environ Res. 1998;79(1):51 " 68. [View Abstract]
Codes
ICD09
- 984.9 Toxic effect of unspecified lead compound
- 984.0 Toxic effect of inorganic lead compounds
ICD10
- T56.0X4A Toxic effect of lead and its compounds, undetermined, init
- T56.0X1A Toxic effect of lead and its compounds, accidental, init
SNOMED
- 38342005 toxic effect of lead compound (disorder)
- 72446009 Toxic effect of inorganic lead compound
- 216662006 Accidental poisoning by lead paints (disorder)
FAQ
- Q: What is lead abatement?
- A: Lead abatement is removal of a lead hazard from the environment either by replacing it (e.g., installing a new window), enclosing the area with the lead source (e.g., installing paneling), removing the lead-based paint from a surface (burning or dry sanding methods should never be used), or encapsulating the area (placement of a specific coating over the lead-containing surface, which prevents access to the lead hazard).
- Q: Is lead abatement permanent?
- A: Often, lead paint that is chipping or peeling is removed from a home. Any areas with intact lead-based paint may become deteriorated with aging, leading to new lead hazards, although ongoing maintenance and repair may prevent this.
- Q: Why didn 't my child 's brother and sister get lead poisoning at the same age since they lived in the same house?
- A: Children are different; some do much more hand-to-mouth activity than others, which is the main way that children get lead into their bodies. Also, your home may not have had the same lead dangers (hazards) when the siblings were younger.