Effects of Lead Poisoning on Our Children's Brains

The recent news about high levels of lead in Flint, Michigan's water supply has reignited our interest in and concern about lead poisoning, specifically the effects on brain function and academic achievement. The purpose of this blog post is to provide a brief review of the scientific research about the effects of lead on brain development and function and provide advice about next steps for concerned parents and teachers.

What are the dangers of lead?

Lead is a heavy metal. When consumed or inhaled, lead is poisonous to many parts of the body including our heart, blood vessels, and kidneys. But lead is particularly harmful to the brain and other parts of the nervous system. Physicians and neuroscientists have known about the effects of lead on the brain for over a century.  In 2008, Robert Brochin and his colleagues at Georgetown University School of Nursing and Health Sciences provided an understandable description of the effects of lead on the brain. Essentially, lead blocks brain receptors important to plasticity - the brain's capacity to change through experience. Blockage of these receptors interferes with the brain's ability to permanently take in and store new information - to learn. Teachers will quickly recognize the implications for academic success. And there is a long history of research documenting the effects of high to low levels of lead exposure on academic achievement.

Exposure to large doses of lead may cause bodily symptoms that are severe enough to require a doctor visit. Unfortunately, though, the effects of smaller doses of lead poisoning may not be immediately apparent, because the effects on learning and memory may be gradual and may sometimes be attributed to other factors like poverty or environment. It is important to recognize that lead exposure is not restricted to Flint's water supply, although it is highly publicized and therefore we are all aware of it. Reports are mounting nationwide of other large urban areas undergoing testing and having evidence of higher than acceptable lead levels in their drinking water or from other sources.

In an excellent recent summary of the research on lead exposure and academics prepared by the Expert Panel on Educational Services for Children Affected by Lead, the authors review studies on low levels of lead exposure in areas of the county as diverse as North Carolina, Connecticut, Chicago, Detroit, Milwaukee, Rhode Island, New York, Massachusetts and Ohio, which show a consistent link between low-level lead exposure and school achievement. The Expert Panel Report concludes that "lead exposure is responsible for a significant and modifiable effect on the achievement gap...and [result in] substantial costs to local communities".

The EPA website provides an excellent summary on how to protect your family from lead exposure from common sources of lead contamination in our soil, yards and playgrounds with suggestions for preventing contamination:

• Lead is naturally-occurring, and it can be found in high concentrations in some areas. In addition, soil, yards and playgrounds can become contaminated when exterior lead-based paint from houses or buildings flakes or peels and gets into the soil. Soil may also be contaminated from past use of leaded gasoline in cars, from industrial sources, or even from contaminated sites, including former lead smelters.
• Lead in soil can be ingested as a result of hand-to-mouth activity that is common for young children and from eating vegetables that may have taken up lead from soil in the garden. Lead in soil may also be inhaled if re-suspended in the air, or tracked into your house - thereby spreading the contamination.

The good news is that there are steps we can take to prevent lead exposure in our children, there are medical interventions that can be used if high blood levels of lead are detected, and, there are neuroscience-based interventions that have been shown to improve attention and learning capacity after other types of neurotoxic exposure that offer promise for use with children exposed to lead.

How to prevent lead contamination

The first step we should all consider if there is a possibility of lead exposure in our environment is prevention. The EPA website link provided above includes some suggestions for families.  Their suggestions include:

• If your house or apartment was built before 1978, you can have a certified contractor inspect your home for possible lead-based paint.
• If you live in an older apartment, notify a landlord immediately if you suspect deteriorating paint.
• Clean surfaces such as floors and windowsills weekly and carefully wash the cleaning utensils used.
• Take precautions before remodeling an older home because disturbing surfaces with lead-based paint can result in dangerous amounts of lead dust throughout the home.
• Make certain children wash their hands often, keep play areas clean, and prevent children from chewing on painted surfaces such as window sills and furniture.
• Provide children balanced diets since there is evidence that children with good diets absorb less lead. (Stewart and Schwartz, 2007)
• Finally, the EPA suggests checking the exterior of your home, including porches and fences, for flaking or deteriorating lead-based paint that may contaminate soil in your yard or be tracked into your house. To avoid tracking contaminated soil into your house, put doormats outside and inside all entryways, and remove your shoes before entering. 

How to assess for lead in the blood stream

If you suspect a child might have been exposed to even mild levels of lead, or if you see any indications of a marked change in cognitive function, the first step is to consult with a physician who can test for levels of lead in the blood stream. The physician may recommend a type of medical treatment that eliminates lead from the body. The physician, school or other professional may also recommend the child receive neuropsychological testing.

What skills are affected by lead exposure?

Cognitive skills that may be affected in children exposed to lead include attention, executive function, visual-spatial skills, speech and language skills, and motor skills.  A brief summary of the research on the cognitive effect of lead exposure is summarized below, you can also read the full report by the U.S. Department of Health and Human Services Expert Panel.

• Attention
  • For many years, professionals have observed attentional problems associated with lead exposure including distractibility, inattention, and impulsivity. The various behavioral manifestations of attentional problems have been measured and quantified in a number of childhood lead studies over the past three decades. (Needleman  et al., 1979 and 2004)
  • Psychologists and other clinicians who treat lead-poisoned children have noted that they have a higher risk for developing ADHD.
• Executive Functions
  • Neuroscientists have shown that the dopamine neurotransmitter system is particularly sensitive to lead (Cory-Slechta 1995). Dopamine is important for executive functions mediated by the prefrontal cortex. Those dopaminergic executive functions like organization skills, self-control and working memory seem especially vulnerable to lead exposure.
• Visual-Spatial Skills
  • Visual-motor integration deficits are among the most consistently associated with early lead exposure.  Studies employing specific measures of visual-motor integration skills, such as the Developmental Test of Visual Motor Integration, and the Bender Visual-Motor Gestalt Test, have consistently revealed problems in this area when young children are exposed to lead.
• Behavioral Challenges
  • Disturbances in behavior and social conduct are very common among victims of lead poisoning.
• Speech and Language
  • Poorer phonological, lexical, and sentence processing measures were found among children with higher bone lead concentrations In the Pittsburgh Youth Study. (Campbell et al., 2000).
  • A brain imaging study using Functional Magnetic Resonance Imaging (fMRI) among a subset of young adults in the Cincinnati Lead Study (Yuan et al., 2006) indicated that elevated childhood levels of lead in the blood resulted in an atypical brain reorganization of language function in the young adults.
  • Elevated blood levels of lead may also be associated with small but significant deficits in hearing and central auditory processing although those research findings are mixed.
• Fine and Gross Motor Skills
  • Problems with gross and fine motor development were also shown in the Cincinnati study that were associated with elevated levels of lead identified during infancy and the preschool years. Poorer scores were observed on measures of bilateral coordination, visual-motor control, upper limb speed and dexterity, as well as a fine motor composite score.

How can we help children who have been exposed to lead?

Many community and school-based resources are available for intervention with children who have been identified as having been exposed to lead.  An exhaustive list is provided in the 2015 Expert Panel on Lead publication.

There are also neuroscience-based interventions that have been shown to be effective with childhood exposure to other types of neurotoxic agents. Neuroscience-based interventions which are specifically designed to enhance brain plasticity in children and shown to be effective with specific types of learning issues associated with lead exposure, like attentional, reading and specific language impairment show promise for those impairments seen in children with lead exposure. In addition, although there are not as yet controlled studies of neuroscience-based interventions with children exposed to lead, there is controlled research with children who have been exposed to other neurotoxic agents that offer promise. For example, Zou and colleagues published research demonstrating that the Fast ForWord programs provided an effective intervention with children successfully treated for brain tumors with radiation and chemotherapy. Development of reading skills is vulnerable to disruption in children treated for brain tumors. As in the case of neurotoxic exposure to lead, remedial and preventive interventions are needed to prevent and/or remediate reading and other learning difficulties faced by cancer survivors.  The researchers used brain imaging and found that the group of brain tumor survivors who used Fast ForWord showed a trend toward normalization of brain function compared with a control group. They also found that standardized reading scores as well as the patterns of brain activation provided evidence of long-term benefits from the neuroscience-based reading intervention.

References

Brochin, R., Leone, S., Phillips, D., Shepard, N., Zisa D. &  Angerio, A. (2008) The Cellular Effect of Lead Poisoning and Its Clinical Picture. THE GEORGETOWN UNDERGRADUATE JOURNAL OF HEALTH SCIENCES 5 (2).

Campbell TF, Needleman HL, Riess JA, Tobin MJ. 2000. Bone lead levels and language processing performance. Developmental Neuropsychology 18:171–86.

Cory-Slechta DA. 1995. Bridging human and experimental animal studies of lead neurotoxicity: Moving beyond IQ. Neurotoxicology Teratology 17:219–21.

Educational Services for Children Affected by Lead Expert Panel. Educational interventions for children affected by lead. Atlanta: U.S. Department of Health and Human Services; 2015.

Needleman HL, Gunnoe C, Leviton A, Reed R, Peresie H, Maher C, et al. 1979. Deficits in psychologic and classroom performance of children with elevated dentine lead levels. New England Journal  of Medicine, 300:689–95.

Stewart, W., and Schwartz, B. (2007). Effects of lead on the adult brain: A 15-year exploration. American Journal of Internal Medicine, 50, 729-39.

U.S. Environmental Protection Agency. Protect your family from lead in your home. Accessed on March 29,2016.

Yuan W, Holland SK, Cecil KM, Dietrich KN, Wessel SD, Altaye M, Hornung RW, et al. 2006. The impact of early childhood lead exposure on brain organization: A functional magnetic resonance imaging study of language function. Pediatrics 118:971–7.

Zou, P.,  Conklin, H.M., Scoggins, M.A.,   Li, Y., Li, X.,Jones, M.M.,Palmer, S.L.,Gajjar, A. & Ogg, R.J. (2015) Functional MRI in medulloblastoma survivors supportsprophylactic reading intervention during tumor treatment. Brain Imaging and Behavior. Springer, published online May 2015.