Neurological Effects of Lead Toxicity in Children

The central nervous system effects of lead toxicity are not a new discovery. But widely aired news of lead contamination in the Flint, Michigan water supply is raising public awareness of the prospect of lead ingestion and making parents more aware of the symptoms of lead toxicity. Attentiveness to the subtle signs of lead-induced illness can be helpful to practicing neurologists as parents and teachers could begin to notice indicators of toxicity earlier than before, making it more likely for children to get a timely diagnosis and receive treatment at a more optimal stage in their neurological development. 

The data about pediatric and neonatal lead exposure

Childhood lead exposure causes neuropsychological manifestations of central nervous system damage. The most commonly documented manifestation of elevated blood lead levels in childhood is attention deficit hyperactivity disorder. Numerous population based studies point to a strong correlation between elevated blood levels in children and symptoms of attention deficit.

Exposure to lead can cause serious neurological harm to a child even before birth. Elevated blood lead levels in pregnant women results in fetal exposure, causing neurodevelopmental problems. A recent pilot study in China found that there was an inverse relationship between maternal blood lead levels and neonatal behavioral neurological assessment scores. Blood levels as low as 5 ug/dl during the first trimester of pregnancy had an adverse effect on neurodevelopment.

Diagnosis 

Given the recent news of contaminated lead, there will undoubtedly be an increase in the number of children presenting for evaluation of possible lead toxicity. The Centers for Disease Control and Prevention already recommends blood lead level testing for all refugee children. The threshold for children who have a possible environmental risk of lead exposure or who have symptoms of lead toxicity is very low.

The symptoms of lead toxicity include headaches, irritability, attention problems, and low IQ scores. A careful history and neurological evaluation can help define whether the symptoms are acute or chronic. A blood lead level can determine whether the child has lead toxicity, even if a child is asymptomatic. Kids who are at risk of lead exposure or who have known lead exposure are expected to have a better overall prognosis if they are diagnosed and treated before symptoms develop.

Children who have a blood lead level of 10 ug/dl or higher are considered to have a high lead level and should have environmental intervention. Children who have a lead level over 45 ug/dl require chelation treatment in addition to environmental intervention.

Treatment 

Whether children have symptoms or positive blood tests or not, lead exposure should be discontinued.

Chelation therapy is an oral or injectable medication that binds to lead in order to remove it from the body. Dimercaprol (BAL) is one chelating agent that is to be injected intramuscularly. CaNa₂EDTA is another chelating agent that is injected intravenously. Both treatment regimens are known to have mild to moderate side effects. 

How often do you talk about lead exposure with pediatric patients or with pregnant patients?

References:

Liu J, et al. Lead exposure at each stage of pregnancy and neurobehavioral development of neonates. Neurotoxicology. 2014 Sep;44:1-7.

Kim S, et al. Lead, mercury, and cadmium exposure and attention deficit hyperactivity disorder in children. Environ Res. 2013 Oct;126:105-110.

Agency for Toxic Substances and Disease Registry. Lead toxicity. How should patients exposed to lead be treated and managed? http://www.atsdr.cdc.gov/csem/csem.asp?csem=7&po=13