LEAD POISONING: THE SILENT EPIDEMIC
by J. Gordon Millichap, MD, professor emeritus of pediatrics and neurology, Northwestern University Medical School, who adapted the material for this article from his new book, Environmental Poisons in Our Food: a practical guide to hazards associated with food and water, and ways to avoid them (ISBN 0-9629115-7-7, PNB • Publishers, P.O. Box 11391, Chicago, IL 60611).
Tom, aged two, like many toddlers and some pregnant mothers, had a craving for unnatural items of food. This unusual appetite known as "pica" is harmless in adults but may have tragic consequences in young children. While his mother may have had a taste for chipped ice, Tom preferred to eat chips of peeling paint, dirt, and paper. Unfortunately, all three items may contain lead, and the paint applied to his pre-1950s home was heavily contaminated.
A visit to the pediatrician at three years of age because of irritability, listlessness, and sleep disturbances uncovered an anemia and a moderate delay in development. Tom had not begun to speak in sentences and had not mastered his new tricycle, achievements expected in children of his age. A supplement of iron to his diet corrected the anemia, he became less irritable, and his speech and coordination improved.
Tom's intelligence was not a concern until his entry to kindergarten at age five years. The teachers complained of inattentiveness, distractibility, and hyperactivity -- symptoms that suggested a diagnosis of attention deficit disorder. A Stanford-Binet test by the school psychologist revealed an unexpected borderline low intelligence score. A complete physical and neuralgic evaluation was clearly indicated.
The pediatric neurologist, a physician trained in both pediatrics and neurology, found that Tom could neither hop nor walk a balance beam, his eye-hand coordination was impaired, and his reflexes showed subtle abnormalities. The electroencephalogram report showed nonspecific, moderate, and diffuse irregularity without evidence of epilepsy or localized brain damage. The differential diagnosis included possible birth trauma, thyroid deficiency, or toxic and nutritional factors. The early history of "pica" prompted the suspicion of lead poisoning as the cause of Tom's intellectual and behavioral difficulties and his failure to achieve in school. A blood test for lead content of 25 mcg/dL supported the diagnosis. The lead level was far above the 10 mcg now accepted as the threshold for neurobehavioral toxicity in young children.
What can be done to help Tom learn? How can the lead be removed from Tom's blood and brain? Where did the lead come from and how can it be avoided? Is the brain damage permanent?
These were some of the questions posed by the anxious parents. Tom was enrolled in special education programs and a smaller classroom. He later received remedial reading instruction to correct a dyslexia, a complication of lead exposure at an early age.
Tom no longer suffered from irritability, sleep disorders, and other symptoms of lead poisoning, and his blood lead level was not high enough to require chemical treatments that chelate or combine with lead and accelerate its removal from the blood and tissues. The chelation chemicals, Versenate®, BAL®, or Chemet®, are restricted for use in patients with blood lead levels above 45 mcg/dL and in those with acute symptoms of headache, seizures, or loss of consciousness. Attention to the diet, including supplements of calcium and iron, were the only medical treatments advised.
The removal of the child from the source of lead and the removal of the lead from Tom's home and environment were the cornerstones of therapy.
When the paint chips from the peeling windows proved to be the primary source of lead, the landlord had the premises professionally vacuumed, scrubbed with high-phosphate detergents, and then repainted with unleaded paint. The program cost $7,000! Tom and his mother, who was pregnant again, were required to evacuate the premises until the abatement of the lead paint had been completed.
A test of the soil around the house showed a mean lead content of 200 parts per million and, to the landlord's relief, not a high enough contamination to demand costly soil removal and replacement.
A recent study of lead-contaminated soil abatement in Boston, published in the Journal of the American Medical Association (JAMA), April 7, 1993, showed that soil abatement around homes results in only a modest decline in blood lead levels of exposed children. The median surface soil lead levels fell from 2,075 parts per million before abatement to 105 parts per million after abatement. Urban children with lead exposure were not appreciably benefited by the reduction in the level of lead in the soil.
Tom was encouraged to wash his hands before eating. His mother was advised to wash his toys periodically and to use a moist mop on the floors to remove any lead containing dust and dirt.
What was Tom's progress after these treatment programs?
The teachers noticed gradual improvements in Tom's attention span and school performance. The pediatrician tested the blood at intervals and found a reduction in the lead level and an increase in iron measured as ferritin.
Could the improvements in learning be a direct result of the reduction in the blood lead level?
In a study at the Department of Pediatrics, Albert Einstein College of Medicine, Bronx, New York, also published in JAMA, the effects of lowering blood lead levels on cognitive performance were measured in lead-poisoned children whose pre-treatment blood lead levels were found to be as high as 25 to 55 mcg/dL. When the children were retested after an interval of six months, the Stanford index of intelligence had increased 1 point for every decrease of 3 mcg/dL in blood lead level. At short term follow-up,improvements in intelligence test performance also correlated with treatment for anemia.
The authors of the study propose a link between the decline in blood lead following treatments and the improvements noted in intelligence. However, they admit a possible contribution from the iron supplement therapy for anemia or from other factors in the unexpected cognitive benefits of lead chelation. These questions notwithstanding, the ability to reverse the brain damage caused by lead poisoning in early childhood is a remarkable and exciting development.
What is the extent of this "silent epidemic" in the United States? What can be done to eliminate the hazard of lead and its subtle though tragic effects on the developing nervous systems of children?
An estimated three million children in the United States and seventy percent of those under five years of age living in larger cities have blood lead levels greater than 10 mcg/dL, sufficient to cause learning and behavior problems that are often unrecognized or diagnosed late.
Public health agencies have attempted to reduce the risks of lead exposure and poisoning by enforcing a drinking water standard for lead of 15 parts per billion, reducing the lead content of canned foods, and eliminating lead additives in gasoline. Lead in residential paints was banned in 1977, but lead-based paint remains the primary source of lead exposure for children.
Methods of preventing lead ingestion include the following:
Screening tests for children.
In many States, physicians or health care providers are required by law to screen children six months to six years of age for lead poisoning, in accordance with guidelines proposed by the American Academy of Pediatrics. All children are at risk for lead poisoning in our industrialized society, but those under six years and those living in older housing are the groups with the highest priority for screening.
Situations alerting to the immediate necessity for screening tests for lead include the following:
Lead poisoning requires a coordinated approach.
Patients affected by lead are diagnosed by doctors and nurses providing routine health care. Local health departments visit high-risk neighborhoods to set up screening clinics. State laboratories arrange for testing of blood samples. Public health officials work in collaboration with these professionals and agencies to prevent lead exposure and poisoning. Let us hope that these efforts in the future will eliminate this "silent epidemic" and prevent the intellectual deficits suffered by Tom and others like him. The ubiquitous exposure of children to a preventable environmental disease is an unfortunate reflection on our society.
In the words of warning of Rene Dubos, scientist and philosopher, more that twenty years ago:
The problem of lead poisoning is so well-defined, so neatly packaged with both causes and cures known, that if we don't eliminate this social crime, our society deserves all the disasters that have been forecast for it.
Article from NOHA NEWS, Vol. XIX, No. 3, Summer 1994, pages 1-2.