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Spring 2006
The Effects of Lead
Exposure on School Performance
Rita Gergely,
Chief, Lead Poisoning Prevention Bureau
Iowa Department of Public Health
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Lead adversely affects
nearly all organ systems in the body. It is especially harmful to the
developing brains and nervous systems of children under the age of 6 years.
Very high blood lead levels can cause severe brain damage in children, and
can be lethal.
Blood lead levels as low
as 10 micrograms per deciliter (μg/dL) can affect a child’s intelligence,
hearing, and growth. Reducing a child’s lead exposure can stop additional
harm, but will not reverse the damage. A child is considered to have
lead-poisoning at a blood lead level of 10 μg/dL. The Centers for Disease
Control and Prevention (CDC) identified this level because it is the |
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level at which health
effects can become significant. This is the level at which CDC
recommends
treatment to keep the blood lead level from increasing.
A number of studies
estimate that a child’s IQ will drop by one to three points for every
increase of 10 μg/dL of lead in a child’s blood. In a community, the
presence of lead-poisoned children is associated with an increase in the
number of children with developmental deficits and learning disorders, and
this places an additional burden on our educational system.
Critical transition points.
Many children do not
show any developmental delays when diagnosed as lead-poisoned, so health
care providers and those conducting developmental assessments may falsely
assume that they will not show developmental delays later on. However, many
lead-poisoned children do show developmental delays when they are older. It
is important to track the behavior and development of lead-poisoned children
into the school years to determine whether they have any problems.
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According to the CDC,
the effects of lead poisoning on a child’s classroom performance may not
appear until the child reaches certain “critical transition points” in
school. CDC defines these critical transition points as: |
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1st grade |
When children begin to acquire
basic skills such as reading and arithmetic |
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4th grade |
When
children begin to use basic skills to learn material |
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6th
- 7th
grade |
When students begin to use
higher-order planning and organizational skills to complete
long-term projects |
Lead poisoning is associated with difficulties with these types of skills.
While most of these studies took place in the United States, two studies
done in Australia under a different educational system found similar
results. The first study showed a 4- to 6-month delay in reading skills for
a group of children with high levels of lead in the blood, when compared to
a group with low lead levels. A follow-up study showed that the high-lead
group continued to have lower reading scores at the age of 18 years.
If a child with lead
poisoning has difficulty at one of these transitions, the child is at
increased risk of having trouble with later transitions. Even children who
made early transitions smoothly should be monitored carefully at later
transition points because they may have problems with developing and using
higher level skills.
Children who are
lead-poisoned in early childhood are also at an increased risk for behaviors
that interfere with learning, such as inattention, distractibility, and
impulsivity. These behaviors are characteristic of a recently identified
subtype of ADHD. While these behaviors may not be sufficient to warrant a
diagnosis of ADHD, the child may benefit from classroom and work
accommodations typically made for any child with an attention disorder.
The fact that a child
who is lead-poisoned at an early age can have developmental delays that
affect school performance later on clearly indicates the importance of
testing children for lead poisoning at intervals during childhood. The early
identification of children with mildly elevated blood lead levels can
minimize the effects of lead poisoning, and keep the damage from escalating.
At this early stage, intervention will often keep the child’s blood lead
level from increasing and will eventually cause it to drop, lessening the
effects of lead poisoning on the child’s school performance.
Resources
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