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

Lead Toxicity
How should patients exposed to lead be evaluated?

Learning Objectives

Upon completion of this section, you will be able to

• describe the CDC’s recommendations for blood screening
• describe key features of the exposure history
• name the symptoms of low dose lead toxicity
• describe how exposure dose and symptoms can vary
• describe key features of the physical examination.

Introduction

Because children may be exposed to levels of lead which could adversely affect their health without exhibiting clinical symptoms, it is vital that primary care providers adopt a preventive approach to determine which of their patients may be at risk.

Primary care providers can adopt a preventive approach by asking questions to assess a patient’s potential for exposure to lead and/or by following statewide protocols for screening. Where the potential for exposure exists, a patient’s blood lead levels (BLL) should be tested.

This section focuses on preventive screening, physical examination, and signs and symptoms. Recommended tests are discussed in the next section.

Preventive Assessment and Screening

A primary care provider may identify individuals who may be exposed to potentially dangerous levels of lead before symptoms of lead poisoning manifest themselves. It is often possible and many times crucial for the primary care provider to screen appropriately, manage patients, and facilitate appropriate environmental and nutritional intervention.
Recognition of a lead exposure often depends on the initial reporting of high BLLs by primary care providers.

• In the case of children, CDC recommends that states develop statewide plans for BLL screening (CDC 1997a).
• These plans and practices vary from state to state (NCHH 2001), and may advocate universal screening of children from high-risk areas at ages one or two and of all children up to age seven who have not previously been screened. Alternatively, they may call for targeted screening based on responses to several questions intended to determine risk more selectively (e.g., type and age of house and whether or not patient’s family is a Medicaid recipient).
• Some local health departments, such as the City of Chicago, recommend testing every six months beginning at six or nine months of age.
• Contact your state or local health department to see if your state has a lead screening plan.
• If your pediatric patient falls into a category such as Medicaid where screening is required or recommended, it is important to follow the guidelines and screen the patient. It is equally important to report a positive test to the appropriate agency(s).
• For occupationally exposed adults, OSHA is responsible for issuing standards and regulations that pertain to workplace exposures (http://osha.gov/SLTC/lead/index.html). However, the primary care provider should be aware if a patient fits into an occupational group exposed to lead and whether the BLL is being monitored, when evaluating the patient.

Lead Exposure Risk Questions

The first step in identifying individuals with potential lead exposure is to determine through appropriate questioning whether or not any of the typical lead exposure pathways are cause for heightened concern. (In the case study, the fact that the previous pediatrician apparently did not pursue this line of questioning constitutes a missed opportunity for preventive action.)

• Many health departments can provide physicians with personal risk questionnaires and/or localized risk information to help in this process (see the “Sources of Information” section).
• Another useful resource is the CDC publication, “Managing elevated blood lead levels among young children” (CDC 2002).

Here are some of the issues a physician might discuss with the patient and/or family (see also Case Studies in Environmental Medicine: Taking an Exposure History” [ATSDR 1992]).

• condition of household pets
• drinking water source and type of pipes
• family history, including possibility of maternal/family exposure and potential use of unusual medicines or home remedies
• frequency of visits to houses or facilities built before 1950
• hobbies of all family members
• home remodeling activities
• location, age, physical condition of current residence, school, and day-care center, etc. (to identify potential for lead paint as well as proximity to industrial facilities, hazardous waste sites, and other potential lead sources)
• nutritional status
• occupational history of all home occupants
• past living conditions (international background is important)
• siblings or playmates who have been diagnosed with lead poisoning
• use of imported or glazed ceramics.

Lead is most harmful to children under six years of age.

• Every child who has a developmental delay, behavioral disorder, or speech impairment, or who may have been exposed to lead, should be screened with a blood lead test.
• Equally important, siblings, housemates, and playmates of children with suspected lead toxicity probably have similar exposures to lead and should be screened.

Individuals with potentially high lead exposure should be screened with a blood lead test.

• They (and/or their parents) should also receive lead education, including:
  • behavioral interventions
  • guidance on appropriate nutrition
  • environmental interventions (see “Treatment and Management” section).
• Physicians may want to consider giving parents anticipatory guidance prenatally and before a child reaches one year of age.
• Physicians should take advantage of the programs and printed materials available through state and/or local health departments in providing this guidance.

Physical Examination

In addition to the environmental/family history assessment and BLL screening described above, physicians should conduct a complete physical examination of patients with potential exposure to lead.

It is important to keep in mind, however, that even a complete physical examination may not identify subtle neurological effects that may be associated with low-level lead exposure in children.

The physical examination should include special attention to these systems

• neurological
• hematological
• cardiovascular
• gastrointestinal
• renal

Areas of special concern for health care providers.

• Carefully evaluate the nervous system, including behavioral changes.
• Check blood pressure to evaluate whether the patient is hypertensive and pay special attention to the renal system in those who are positive for hypertension.
• Check for a purplish line on the gums (lead line). This is rarely seen today, but if present, usually indicates severe and prolonged lead poisoning.

Areas of special concern for children by health care providers.

• Hearing, speech, and other developmental milestones should be carefully evaluated and documented.
• Since iron and calcium deficiencies are known to enhance the absorption of lead and to aggravate pica, it is especially important to assess the nutritional status of young children.
• The opening case study illustrates a second missed opportunity: despite the delayed growth (20th percentile) and speech indicators discovered during the preschool physical (at age four), no BLL test was ordered at that time.
• When the neurological exam, milestones, or behavior suggest it, further neurobehavioral testing, or evaluation for ADHD, may be indicated.

Signs and Symptoms

• Most patients who suffer from lead poisoning are asymptomatic, hence the importance of exposure assessment and screening. There is a continuum of signs and symptoms depending on level and duration of lead exposure (see Table 4.)
• At the low exposure levels found today, most children will be asymptomatic, but these levels may still impair the health of children and adults. With increasing exposure dose, the severity of symptoms can be expected to increase.
• Because of differences in individual susceptibility, symptoms of lead exposure and their onset may vary.
• The impaired abilities may occur at BLLs ranging from 10 to 25 µg/dL, whereas in symptomatic lead intoxication, BLLs generally range from 35 to 50 µg/dL in children and 40 to 60 µg/dL in adults.
• Severe toxicity (high exposure dose) is frequently found in association with BLLs of 70 µg/dL or more in children and 100 µg/dL or more in adults.

The impaired abilities that may be associated with lead exposure in an apparently asymptomatic patient are listed in Table 4. Also shown are overt symptoms of lead toxicity associated with ongoing exposure. In interpreting this table, it is important to remember that

• Some of the hematological abnormalities of lead poisoning are similar to those of other diseases or conditions. In the differential diagnosis of microcytic anemia, lead poisoning can usually be ruled out by obtaining a venous blood lead concentration; if the BLL is less than 25 µg/dL, the anemia usually reflects iron deficiency or hemoglobinopathy. Two rare diseases, acute intermittent porphyria and coproporphyria, result in heme abnormalities similar to those of lead poisoning, too.
• Patients exhibiting neurological signs due to lead exposure have been treated only for peripheral neuropathy or carpal tunnel syndrome, delaying treatment for lead intoxication.
• Failure to diagnose correctly lead-induced gastrointestinal distress has led to inappropriate abdominal surgery.
• Current health effects (e.g., neurological/developmental) resulting from past exposure, even without current exposure, may also need intervention, if, for example, special education is needed, or if the danger of exposure is still present and/or to prevent exposure in others.

Keep in mind that dividing the signs and symptoms by exposure dose from lowest to high is somewhat artificial — the signs and symptoms generally increase with increasing BLL but in some individuals may appear at variance with these designations. The importance for the clinician is to recognize ongoing lead exposure, interrupt that exposure, and treat the patient as appropriate.

Lowest Exposure Dose Signs and Symptoms: Impaired Abilities (patient may appear asymptomatic)

• Decreased learning and memory
• Lowered IQ
• Decreased verbal ability
• Impaired speech and hearing functions
• Early signs of hyperactivity or ADHD

Low Exposure Dose Signs and Symptoms

• Myalgia or paresthesia
• Mild fatigue
• Irritability
• Lethargy
• Occasional abdominal discomfort

Moderate Exposure Dose Signs and Symptoms

• Arthralgia
• General fatigue
• Difficulty concentrating/Muscular exhaustibility
• Tremor
• Headache
• Diffuse abdominal pain
• Vomiting
• Weight loss
• Constipation

High Exposure Dose Signs and Symptoms

• Paresis or paralysis
• Encephalopathy—may abruptly lead to seizures, changes in consciousness, coma, and death
• Lead line (blue-black) on gingival tissue
• Colic (intermittent, severe abdominal cramps)

Key Points

• Because children may be exposed to potentially adverse levels of lead without exhibiting clinical symptoms, it is vital that primary care providers adopt a preventive approach to determine which of their patients may be at risk.
• While important for monitoring the effects of lead exposure and, in some cases, for identifying the symptoms of lead poisoning, the physical examination alone will not always reveal when a patient is at risk from elevated lead exposure.
• The first signs of lead poisoning in children are often subtle neurobehavioral problems that adversely affect classroom behavior and social interaction.
• Developmental, speech, and hearing impairments are not uncommon in lead-exposed children (ATSDR 2005).
• Most persons with lead toxicity are not overtly symptomatic.
• Some of the health effects of lead exposure on the various organ systems (see “Physiological Effects” section) are permanent or latent and may appear after exposure has ceased.

Progress Check