Agency for Toxic Substances and Disease Registry
Case Studies in Environmental Medicine (CSEM) 

Lead Toxicity
Who Is at Risk of Lead Exposure?

Learning Objectives

Upon completion of this section, you will be able to

• identify the populations most heavily exposed to lead.

Introduction

Both children and adults are susceptible to health effects from lead exposure, although the typical exposure pathways and effects are somewhat different.

• Children who reside in pre-1978 housing facilities (and especially those in inner cities or those built before 1950) are at greatest risk for exposure, because the houses may contain lead-based paint.
• Adults who work in jobs involving lead may be occupationally exposed.
• Developing fetus are also at risk for adverse health outcomes (less than 1% have levels greater than or equal to 10 µg/dL), as levels that present risk to the fetus do not present risk to the mother.

Children

While children’s lead levels have steadily declined in recent decades, some populations of children are still at significant risk of lead poisoning.

• In particular, children who live in older housing are more likely to have elevated BLLs than the population of U.S. children as a whole.
• It is important to note, however, that no economic or racial/ethnic subgroup of children is free from the risk of having BLLs high enough to cause adverse health effects.
• Of the children reported with confirmed elevated BLLs between 1997 and 2001, approximately 17% were non-Hispanic whites, 60% were non-Hispanic blacks, 16% were Hispanic, and 7% were of other races or ethnicities. (CDC, 2003)
• The children affected are more likely to be poor and from racial/ethnic minority groups that cannot afford appropriate housing.

Because of their behavior and physiology, children are more affected by exposure to lead than are adults.

• Children absorb more ingested lead than do adults.
• Children generally ingest lead-contaminated soil and house dust at higher rates than adults because of mouthing and hand-to-mouth behaviors.
• Children who exhibit pica, a compulsive hand-to-mouth behavior and repeated eating of nonfood items, are at greatest risk.
• Children have a higher breathing rate than adults, breathing in a greater volume of air per pound.
• Being shorter than adults are, children are more likely to breathe lead-contaminated dust and soil as well as fumes close to the ground.
• In addition, the percent of lead absorbed in the gut, especially in an empty stomach, is estimated to be as much as five to 10 times greater in infants and young children than in adults. (Alexander et al. 1974; Chamberlain et al. 1978; James et al. 1985; Ziegler et al. 1978 as cited in ATSDR 1999)
• Gastrointestinal absorption of lead in children is increased by iron, calcium, zinc, and ascorbate deficiency. (Mahaffey et al. 1990 as cited in AAP 1993)

Children are more sensitive than adults are to elevated BLLs. Children’s developing brains and nervous system (and other organ systems) are very sensitive to lead.

• Childhood lead exposure has been associated with
  • higher absenteeism in high school
  • lower class rank
  • poorer vocabulary and grammatical reasoning scores
  • longer reaction time
  • poorer hand-eye coordination (AAP, 1993)
• The incomplete development of the blood-brain barrier in fetuses and in very young children (up to 36 months of age) increases the risk of lead's entry into the developing nervous system, which can result in prolonged or permanent neurobehavioral disorders.
• Children’s renal, endocrine, and hematological systems may also be adversely affected by lead exposure.

There is no known threshold exposure level (as indicated by BLLs) for many of these effects. No blood lead threshold for adverse health effects has been identifies in children.

Adults

Although children are at greater risk from lead exposure, adult exposures can also result in harmful health effects.

• Most adult exposures are occupational and occur in lead-related industries such as lead smelting, refining, and manufacturing industries.
• One frequent source of lead exposure to adults is home renovation that involves scraping, remodeling, or otherwise disturbing lead-based paint. Renovation involving lead based paint should only be undertaken after proper training, or with the use of certified personnel.
• Adults can also be exposed during certain hobbies and activities where lead is used. Some of the more common examples include
  • artistic painting
  • car repair
  • electronics soldering
  • glass or metal soldering
  • glazed pottery making
  • molding of bullets, slugs, or fishing sinkers.
  • stained-glass making
• target shooting
• Workers may inhale lead dust and lead oxide fumes, as well as eat, drink, and smoke in or near contaminated areas, thereby increasing their probability of lead ingestion.
• Between 0.5 and 1.5 million workers are exposed to lead in the workplace (ATSDR, 1999).
• If showers and changes of clothing are not provided, workers can bring lead dust home on their skin, shoes, and clothing, thus inadvertently exposing family members.
• People using paints, pigments, facial makeup, or hair coloring with lead or lead acetate also increase their lead exposure risk. Cosmetics containing lead include surma sindhoor and kohl, popular in certain Asian countries.
• Other than the developmental effects unique to young children, the health effects experienced by adults from adult exposures are similar to those experienced by children, although the thresholds are generally higher.

• Auto repairers
• Battery manufacturers
• Bridge reconstruction workers
• Construction workers
• Firing range instructor
• Gas station attendants (past exposures)
• Glass manufacturers
• Lead manufacturing industry employees
• Lead mining workers

• Lead refining workers
• Lead smelter workers
• Plastic manufacturers
• Plumbers, pipe fitters
• Police officers
• Printers
• Rubber product manufacturers
• Shipbuilders
• Steel welders or cutters

Pregnant Women and Developing Fetuses

The mother's blood lead level is an important indication of risk to the fetus and neurological problems in newborns. In addition, mothers who had exposure to lead in the past may store lead in their bones. Lead may be released from bones during times of calcium stress such as pregnancy and lactation. Pregnant women with elevated BLLs may have an increased chance of

• preterm labor
• miscarriage
• spontaneous abortion or stillbirth
• low birth weight

See What are the physiologic effects of lead exposure? for more information.

Key Points

• Today, the population at greatest risk for lead poisoning is children who live in pre-1978 older housing.
• Adults who work with lead or have hobbies involving lead may also be significantly exposed.
• Developing fetuses are also at risk for adverse health outcomes.

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