Download CDC lowers blood lead limits for young children

17/10/2012
Health Canada’s Blood Lead Response
Guidelines: implications for medical practice,
public health and occupational medicine
Tom Kosatsky, BCCDC
OEMAC 2012
Trends in action level for childhood lead poisoning
(1970–1990, CDC, USA)
Also,
Canada
1994
CDC lowers blood lead limits for
young children
In May 2012, the U.S. Centers for Disease Control
and Prevention (CDC) updated its guidance on
the level of lead in a child’s blood it considers
harmful. Children with a blood lead level of 5
micrograms per deciliter (μg/dL) are considered
by CDC to have more exposure to lead than
97.5% of their peers. This policy changed CDC’s
long-standing guidance, which had
recommended action at 10 μg/dL.
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17/10/2012
“
Draft 2011Guidelines
“
“No safe level of
lead exposure has
been identified”
Linear models for each cohort study in the pooled analysis, adjusted for maternal IQ, HOME
score, maternal education, and birth weight. The figure represents the 5th to 95th percentile
of the concurrent blood lead level at the time of IQ testing.
“No safe level of lead exposure has been identified”
Log-linear model for concurrent blood lead concentration along with linear models for
concurrent blood lead levels among children with peak blood lead levels above and
below 10 μg/dL.
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17/10/2012
“Lead has toxic effects on many organ
systems at all life stages”
“Lead has toxic effects on many organ
systems at all life stages”
(Needleman, 1990)
Population significance of a 5 point IQ reduction
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“Current levels of environmental lead
exposure in Canada can be harmful”
“Subpopulations
already
experiencing
health
inequalities are
the most
vulnerable to
lead”
Childhood Lead Poisoning from Commercially
Manufactured French Ceramic Dinnerware --- New York
City, 2003
Lead Poisoning Associated with Ayurvedic
Medications --- Five States, 2000-2003
“Simple and inexpensive actions can reduce lead exposure”
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17/10/2012
With regulation of lead in gasoline, child BLLs have plummeted
“The role of the physician is to identify and manage
those individuals who are not fully benefiting from the
efforts of government and public health agencies to
reduce lead exposure in the general population.
In order to identify patients with atypical blood lead
levels, it is necessary to select those for testing who are
most likely at risk. This practice is equivalent to case
finding where a “case” is a patient who has a blood lead
concentration that is greater than or equal to the 95th
percentile of the expected age specific distribution of
blood lead in the general population”.
“Who and When to Test?
Patient reveals potential for lead-related health concerns
Patient expresses concern about lead exposure
Patient reveals presence of (selected) risk factors
Housing/Residence
Living in or regularly visiting older homes or buildings with chipping
paint or ongoing renovations or remodelling.
Infrequent or ineffective housekeeping that results in the
accumulation of dust.
Family and Behavioural Factors
Having a sibling, housemate or playmate known to have had an
atypical blood lead level.
Living in poverty.
Newcomer from at risk countries
Food/Consumer Products
Use of leaded crystal or pewter food ware.
Vegetarian or vegan diet (risk of low iron and calcium status).
Use of foreign made food, candies, cosmetics or holistic, herbal,
and alternative medicines or folk remedies that are not licensed for
sale in Canada (these items generally do not meet English and
French labelling requirements).”
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17/10/2012
“What is the health risk?
Concentrations above 20 μg/dL (0.96 μmd/L) are
associated with overt symptoms and clinically
relevant outcomes.
An increase in blood lead levels from 1 to 15 mg/dL:
Average reduction of 7 (95% confidence intervals
4 to 10) full
scale IQ points in school-aged children.
Average increase in adult systolic blood pressure
of 4-7 mm Hg
An increase in blood lead levels from 1 to 10 mg/dL:
Average reduction of 6 (95% confidence intervals
4 to 9) full scale IQ points in school-aged children.
Average increase in adult systolic blood pressure
of 3-4 mm Hg
An increase in blood lead levels from 1 to 5 mg/dL:
Average reduction of 4 (95% confidence intervals
3 to 6) full scale IQ points in school-aged children.
Average increase in adult systolic blood pressure
of 1-2 mm Hg
Few data on the potential health effects associated
with blood lead concentrations < 1 μg/dL since, until
recently, few people had low blood lead
concentrations”.
Figure illustrates the estimate of the 95th percentile of the blood lead
concentration in the general population (solid line) and the 95th percentile upper
confidence limit of the estimate (dashed line).
Management by Blood Lead Level
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“Follow these actions for all individuals:
Provide nutritional advice on the value of
adequate calcium, iron, and vitamin C intake
to reduce absorption or increase the excretion
of lead.
Provide patient with educational materials on
sources of environmental lead exposure and
reduction strategies. Check with your local
public health unit for their educational
materials”.
Age-specific estimates of the 95th Percentile Blood Lead Concentrations
Note: The data include US
NHANES 2007-2008 for ages
2 to 6 years combined with
Canadian CHMS data from 6
to 79 and considered
representative of the general
Canadian population.
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17/10/2012
If blood lead concentration ≥ the 95th percentile
based on the age of your patient, and <20 μg/dL
(0.96 μmol/L), follow the recommendations for all
individuals and:
Take an environmental lead exposure history in
order to identify and begin to manage risk
factors for elevated blood lead levels.
Re-test blood lead in 90 days to determine any
temporal trend in the patient's blood lead
concentration.
If blood lead concentration persists ≥ the 95th
percentile for age of your patient, follow the
recommendations for all individuals and:
Assess patient for iron status.
Continue to monitor (every 90 days) until the
blood lead level is no longer > 95th percentile.
Test blood lead concentrations of others living
in the same household.
Notify the local public health authority if
community exposure source is suspected”.
For children of
5-18 years the 95th
percentile blood lead
is at or slightly
over the laboratory
detection limit
“The challenge for the physician is to help the individual
identify the potential source(s) of lead that may be
causing the atypical blood lead levels.”
“Local public health inspectors have the skills and training to
assess community spaces, including child care centres and
schools, rental units and community housing to identify
potential sources of environmental lead exposure.”
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Toxicokinetics of lead
Elimination of
transferred
maternal lead
Equilibrium
with bone
lead stores
“Exposure” is largely historic
The bad old days
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The many residual sources of lead
Challenge of
source
identification
Cochrane Summariesbeta
Independent high-quality evidence for health care decision making
Many educational and environmental
household interventions to prevent lead
exposure in children have been studied. This
review of 14 studies found that educational
and dust control interventions are not
effective in reducing blood lead levels of
young children. There is currently insufficient
evidence that soil abatement or combination
interventions reduce blood lead levels and
further studies need to address this.
Household interventions for preventing domestic
B, Woolfenden S, Lanphear B, Ridley GF, Livingstone N
lead exposure in children Yeoh
Published Online:
April 18, 2012
Ineffectiveness of interventions
Follow these actions for all individuals:
Provide nutritional advice on the value of
adequate calcium, iron, and vitamin C
intake to reduce absorption or increase
the excretion of lead.
Managing a Child’s Nutrition
Although the effectiveness of nutritional
interventions has not been established, the
following recommendations are common sense
and are appropriate advice for all children,
including those with elevated BLLs:
• Consume adequate amounts of bioavailable
calcium and iron.
• Consume at least two servings daily of foods high
in vitamin C, such as fruits, vegetables,
and juices.
• Eat in areas that pose a low risk for lead
exposure; for example, at a table rather than on
the floor.
• Participate in the Special Supplemental Nutrition
Program for Women, Infants, and Children (WIC)
if the family is eligible. Recommendations from the
Advisory Committee on Lead Poisoning Prevention. CDC, 2002
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Low Blood Lead Levels Do Not Appear to Be
Further Reduced by Dietary Supplements
We found no statistically significant
relationships between the PbB concentrations
and micronutrient ((calcium, magnesium,
sodium, potassium, barium, strontium,
phosphorus, zinc, iron (limited data), and
copper)). In adults and older children with low
PbB concentrations and minimal exposure to
Pb, microntrient supplementation is probably
unnecessary.
Brian L. Gulson,1 Karen J. Mizon,1 Michael J. Korsch,2 and Alan J.
Taylor3 Environ Health Perspectives 2006 August; 114(8): 1186–1192.
ALSO Two-thirds of calcium supplements failed to meet the 1999 California criteria for
acceptable lead levels (1.5 µg/daily dose of calcium) in consumer products.
What went awry?
“
“
Why not treat at the
95th percentile?
1. Low analytic precision around the current 95th
percentile BLL for critical age groups
2. BLL does not simply represent current exposure
3. Effective source identification is unlikely at suboutlier BLLs
4. Recommended educational and environmental
household interventions to prevent lead exposure
in children are ineffective
5. Dietary supplementation is unlikely to reduce and
may raise BLL
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17/10/2012
Potential implications for occupational practice
• Inconsistency between action levels (ACGIH) for
workers versus the general population
• May spur more testing of current and former
workers as part of general medical practice
• Ineffective advice to workers to manage nonoccupational exposures
• Movement of occupational blood lead management
from regulatory to the medical practice/public health
domains
alternatives to the “n rmative approach”
•
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Limit recommendations for testing to individuals likely to have a must-intervene blood lead
level (20 mcg/dL in the draft document) .
In advising physicians, other than for patients with must-intervene blood lead levels, emphasize
universal rather than individual measures to lower blood lead.
Provide physicians with the population distribution of blood lead by age and gender. Suggest
practical ways that patients who wish to do so can recognize sources and reduce their lead
exposure; differentiate this advice for infants, children, workers and older adults.
Target for intervention those groups at highest levels of exposure, or in whom the
consequences of exposure are greatest. An example of the former would be new Canadians,
and of the latter women of childbearing age, where nutritional mitigation, and occasionally
environmental investigation and remediation, can prevent inter-generation transmission of
lead. Surveys are likely to be more effective than screening as a guide to finding these groups
and developing ways to reduce their exposure.
Identify new and unusual sources by investigating children with blood lead levels over 10
mcg/dL and adults over 20-25mcg/dL, as at these levels there is a reasonable expectation that
an exposure source can be identified. Develop a national database to promote recognition of
emerging patterns.
Support lead source identification and mitigation at the community level.
Tom Kosatsky*
BCCDC and NCCEH
[email protected]
604 7072447
* Opinions expressed here are those of the author
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