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Lead Poisoning

Medical Experts

Contributor

Boyd

Jessica M. Boyd, PhD, FCACB, DABCC (TC)

Associate Professor (Clinical), University of Utah

Medical Director, Clinical Toxicology, Trace and Toxic Elements, ARUP Laboratories

Lead poisoning and lead toxicity can occur at any age, but they most commonly occur in children and in those with chronic occupational exposure. Toxicity is generally more concerning in children due to their higher sensitivity to lead. In children, lead exposure can result in brain damage, nervous system damage, developmental delay, and hearing and speech problems. In adults, lead exposure can cause adverse reproductive outcomes in women, hypertension, renal damage, and cognitive dysfunction.^, Lead poisoning can also disturb heme synthesis and cause symptoms similar to those of porphyrin disorders, including abdominal pain, nausea, and rapid heart rate.^,

Quick Answers for Clinicians

What is important to know about specimen collection for lead testing to avoid contamination?

Because detection limits for lead are calculated in parts per billion, minimizing environmental contamination at collection is important to provide accurate and clinically useful results. The collection site for blood samples must be properly cleaned before specimen collection to avoid contamination, especially in the case of capillary blood specimens (i.e., collected by the fingerstick method) used for initial screening.

When should patients be screened for lead exposure during pregnancy?

The CDC does not recommend routine screening for lead exposure during pregnancy. If lead exposure is suspected in a pregnant individual, venous blood lead testing should be performed at the earliest point of contact with the patient. Thresholds and time intervals for retesting, medical evaluation, and response may vary by state and regulatory body. Contact the relevant state health department or applicable regulatory agency for specific guidance on medical management recommendations.

Indications for Testing

Laboratory testing for lead poisoning is indicated in adults when a known or suspected exposure has occurred or symptoms of lead poisoning are observed. Children, who are more adversely affected by lead exposure, should be screened for lead poisoning.^, The Occupational Safety and Health Administration (OSHA) requires that workers with potential occupational exposure be routinely screened at least every 6 months. Testing recommendations and requirements can differ between states and regulatory bodies.

Screening

The CDC recommends targeted screening of children at a higher risk of exposure (e.g., due to living in older homes and other risk factors). Children who are enrolled in Medicaid are required to be tested at 12 months and 24 months of age, or at 24-72 months of age if not previously screened for lead exposure.

The American Academy of Pediatrics recommends risk assessment or screening as appropriate at 6, 9, 12, and 18 months of age and annually from 2-6 years of age.

Individual public health programs might have additional requirements or recommendations.

Laboratory Testing

Blood Testing

The best way to measure lead exposure is with a venous blood lead test. Capillary blood tests are used for initial screening for lead poisoning but are not definitive due to the higher risk of contamination with capillary collections. If a capillary test result shows a blood lead level (BLL) equal to or above a standard reference value, a confirmatory venous blood lead test is recommended. BLLs are highly responsive to changes in exposure, which means that test results may not reflect the total lead burden on the body. A single test cannot differentiate between high-level acute exposure and lower-level chronic exposure, so follow-up testing is necessary.^, Thresholds and time intervals for retesting, medical evaluation, and response vary by state and regulatory body. Contact the relevant state health department and/or applicable regulatory agency for specific guidance on medical management recommendations.

Urine Testing

Urine lead testing can be used to assess chronic lead exposure; however, blood is the preferred specimen for routine testing. Urine lead testing has been used to monitor chelation therapy, but this method has not been established and cannot be used as a substitute for BLL testing.

Monitoring

A safe BLL has not been identified for children.^, Children with an elevated BLL should be monitored until environmental conditions are resolved per state health department requirements.

Employees who are exposed to lead should have a baseline BLL determined at job placement and be monitored based on BLL (recommendations vary between health authorities and states). OSHA’s lead standards require that medical monitoring of lead exposure include zinc protoporphyrin measurements.

Other Testing

Lead poisoning can present similarly to porphyrin disorders; therefore, laboratory testing may be helpful in differentiating between the more common lead exposure and other, less common health conditions. Biomarkers of impaired heme synthesis such as blood zinc protoporphyrin, aminolevulinic acid dehydratase (ALAD) activity in erythrocytes, and serum ALA have been used to detect lead exposure but have been mostly replaced with blood lead measurements. Zinc protoporphyrin measurements were previously used to screen for lead poisoning in children, but these measurements are no longer recommended as they are not sensitive enough to detect lead exposure at current blood lead reference values set by the CDC. Refer to the ARUP Consult Porphyrias topic for testing specific to porphyrin disorders.