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 to 5 years collected for the National Health and Nutrition Examination Survey (NHANES).
  • This replaced 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 <10 mcg/dL.

Epidemiology

There are >500,000 U.S. children 1 to 5 years of age with BLLs >5 micrograms per deciliter (mcg/dL).

• 24 million housing units have hazards from lead-based paint.
• In 2015, lead poisoning became national news when the water supply in Flint, Michigan was found to have significantly elevated lead levels. Due to the change in water source, the percentage of Flint children with elevated BLLs may have risen from about 2.5% in 2013 to as much as 5% in 2015.
• 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 to 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 United States Environmental Protection Agency (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 δ-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 neuropsychological 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.