bloodleadreference.pdf
Finding the Next Flint:The Need to Updatethe Blood LeadReference ValuePerry Gottesfeld, MPH
ABOUT THE AUTHOR
Perry Gottesfeld is the Executive Director of Occupational Knowledge International,San Francisco, CA.
In 2012, the US Centers for DiseaseControl and Prevention (CDC)adopted a blood lead reference value of
5 micrograms per deciliter and recog-
nized that there is no known health-
based threshold for effects in children.
Previously, the agency had identified a
“level of concern” implying that blood
lead levels (BLLs) under 10 micrograms
per deciliter were not associated with
harm. In making the switch, there was
purposeful intent to recognize that
there is no safe level of lead exposure
and therefore a new classification sys-
tem was needed to identify and prior-
itize the most highly exposed.1 The
reference value is an action level
at which the CDC recommends envi-
ronmental investigations to identify
sources of lead exposure in a child’s
home.
The reference value is intended to
identify individual children who have
greater lead exposures than others in
the same population.1 This serves to
inform parents that their children are
being exposed to lead at “elevated”
levels far in excess of the median level in
the United States (0.69 mg/dL in
2015–2016).2 Collectively, these results
also inform communities and public
health authorities of patterns in BLLs
and provide a warning of the need to
identify and reduce specific sources of
environmental lead exposure. Compar-
ing results from blood lead testing
against the population background lev-
els allows communities to analyze
trends, thereby highlighting changes in
exposure patterns.3 Conversely, the
success of efforts to remove lead from
products and abate environmental lead
hazards are measured against BLL
benchmarks over time.
In 2014, when the city of Flint, Michi-
gan, changed its drinking water source
and failed to control the pH level, the
protective mineral layer in pipes was
stripped away, allowing more lead into
the water. The prevalence of elevated
BLLs greater than 5.0 micrograms per
deciliter among children aged younger
than 6 years went from 2.4% to 4.9%
after the change in water source. This
increase was detected by physicians and
researchers looking at incremental
changes in the proportion of children
with BLLs greater than the CDC refer-
ence value.4Had the reference value not
been adopted by the CDC, it is likely that
this increase would have been
underappreciated.
There has long been a false dichotomy
between those arguing for increased
surveillance with blood lead testing
(considered secondary prevention) and
the public health paradigm of primary
prevention that seeks to eliminate
sources of exposure before they cause
harm. Although eliminating sources of
environmental lead exposure is the ulti-
mate long-term objective to stop child-
hood lead poisoning, in the interim we
also need to prioritize individuals and
communities that are overexposed to
facilitate actions to reduce harm.
IMPACTS OF LOW-LEVELLEAD EXPOSURE
There is scientific consensus that lead
exposures in children, even at levels less
than the CDC reference value of 5
micrograms per deciliter, are associated
with adverse neurological and behav-
ioral outcomes in children. Low-level
lead exposures are also linked to
hypertension and cardiovascular dis-
ease in adults.5
In 2012, the National Toxicology Pro-
gram published a comprehensive review
on the health effects of lead. The
program’s consensus was that there is
sufficient evidence for neurological
effects in children at BLLs less than 5
micrograms per deciliter. In particular,
they pointed to reduced cognitive func-
tion as measured with standardized
tests such as IQ, and increased inci-
dence of attention-related behavioral
problems and antisocial behavior at
these levels.5
At least five epidemiological studies
have demonstrated adverse outcomes
for children with BLLs less than 5
micrograms per deciliter. These out-
comes include lower reading and math
scores and attention-related behaviors.
The authors of a review of this evidence
1746 Editorial Gottesfeld
OPINIONS, IDEAS, & PRACTICEAJPH
October2021,Vol111,No.10
conclude that these impacts are seen at
BLLs as low as 2 micrograms per
deciliter.6
REVERSINGHEALTH INEQUITY
It is well recognized that elevated BLLs
are not uniformly distributed in the
United States, because of environmen-
tal injustice from living in older, poorly
maintained housing and in areas closer
to industrial emissions. Non-Hispanic
Black children are more than twice as
likely to have a BLL of 5 micrograms per
deciliter or higher and have mean BLLs
that are 50% higher than those of White
children.7,8 A recent study shows that
this difference starts before birth and
persists into childhood.9 The disparity in
BLLs remains even when controlling for
known risk factors, including housing
age, indoor household smoking, and
socioeconomic factors.8
Poverty also plays a significant role,
especially when combined with race.
Black children living in poverty are four
timesmorelikelytohaveanelevatedBLL
than White or Hispanic children, even
after controlling for other known risk
factors.8
It has been well understood that
housing age and conditions are signifi-
cant predictors of lead exposure. Envi-
ronmental lead exposures outside the
home are also contributing to disparities
in BLLs. Findings from a study involving
more than 60 000 children in Kansas
have shown that proximity to lead-
emitting industries, including lead bat-
tery manufacturing, is significantly linked
to higher BLLs.10 Another study found
that race and poverty were predictors of
soil lead levels in both urban and rural
areas. Areas of South Carolina with
higher proportions of Black children had
significantly higher soil lead levels, and
the disparities attributable to race were
greater than disparities observed with
income levels.11
Differences in lead exposures by race
and economic background have been
observed since at least the 1950s and
well documented since the 1970s.12,13
This situation has persisted for decades
even as median BLLs have dropped
precipitously, highlighting the need to
prioritize actions to abate lead hazards
in these communities.
RESPONDING TOENVIRONMENTALCONTAMINATION
Identifying and responding to children
with BLLs above the reference value
allows us to investigate, identify, and
mitigate environmental lead contami-
nation in and around homes. For exam-
ple, one study examined the findings
from Maine after the state required
environmental investigations of homes
where children’s BLLs exceeded 5
micrograms per deciliter. They con-
cluded that such inspections were
nearly as likely to identify lead hazards
that required abatement as were
inspections in homes where BLLs
exceeded 10 micrograms per deciliter.14
At the time that the CDC adopted the
reference level, there were estimated to
be more than 500000 children in the
United States with BLLs exceeding 5
microgramsperdeciliter.7However,very
few of these children had their homes
tested for lead or received any public
health services. Even today in most
states, including California, children with
BLLs below 10 micrograms per deciliter
generally do not receive environmental
inspection services to identify potential
sources of exposure.
Responding to environmental lead
hazards has been shown to be effective
at reducing BLLs among children. The
ability to identify and successfully miti-
gate exposures from paint, dust, and soil
has been repeatedly demonstrated to
reduce BLLs.15–17 In addition, occupa-
tions that result in “take home” expo-
sures and other sources, including
imported food, spices, pottery, and
home remedies, are known to contrib-
ute to childhood lead exposures that
often go undetected in the absence of
public health interventions.
NEED FOR ACTION
The CDC blood lead reference value
does not inform medical, diagnostic, or
treatment protocols for childhood lead
poisoning. Instead, it serves a dual pur-
pose: to inform individual cases (e.g.,
parents) that a child’s exposure exceeds
background levels and to serve as a
public health surveillance tool to warn
that children are being overexposed.
This was the criterion that alerted
physicians in Flint—who in turn notified
the general public, which forced
authorities to respond to the crisis. In
recent years, we have seen similar
communitywide elevated BLLs in one
area of East Chicago, Indiana, and
throughout Newark, New Jersey, serving
to inform authorities of the need to
respond to lead-contaminated soil and
lead in drinking water.18,19
Despite the demonstrated impor-
tance of revising the blood lead action
level in the past, the CDC has failed to
follow the advice of its independent
expert committees to revise the refer-
ence value based on current national
surveillance data. In 2012, the Advisory
Committee on Childhood Lead Poison-
ing Prevention set the initial value at 5
micrograms per deciliter, based on the
97.5 percentile of the National Health
and Nutrition Examination Survey
OPINIONS, IDEAS, & PRACTICE
Editorial Gottesfeld 1747
AJPH
Octo
ber2021,Vol111,No.10
(NHANES) BLL distribution for children
aged younger than 6 years at that time.
In 2017, the CDC’s Board of Scientific
Counselors recommended that the
agency adopt a revised blood lead ref-
erence value for children, using the most
recent NHANES data, that would set the
level at 3.5 micrograms per deciliter.20
In 2021, the CDC’s Lead Exposure and
Prevention Advisory Committee unani-
mously recommended that the agency
lower the blood lead action level for
children to 3.5 micrograms per decili-
ter.21 However, to date no action has
been taken by the agency.
Concerns have been raised about the
expense of public health interventions
for a larger number of children who
would be identified through an updated
reference value.22 There has been con-
troversy during each of the four times
that the CDC lowered the blood lead
action level—starting in 1970, when the
level was 40 micrograms per deciliter.23
However, the CDC is not a regulatory
agency and its guidance is not manda-
tory for state or local health depart-
ments. In fact, since the last revision in
2012, only 18 states and a small number
of local agencies have revised their
response criteria to require some action
when a child’s blood lead test exceeds 5
micrograms per deciliter.24 Some states,
including Maine, Illinois, and New York,
have passed laws in accordance with
CDC recommendations requiring envi-
ronmental assessments for children
with BLLs above the action level.25–27
It is well-known that lead poisoning
has consistently affected more vulnera-
ble populations who have greater
exposures from residing in low-income
areas, living in poorly maintained older
homes, and absorbing more lead
through poor nutrition. Efforts to prior-
itize the reduction of exposures in dis-
advantaged low-income communities
require surveillance to identify the most
highly exposed. If we fail to update our
measure of “overexposure,” we are
ignoring those who are disadvantaged
by living in a contaminated environment
or drinking contaminated water. By not
conducting environmental investiga-
tions and abating identified hazards for
all children with exposures well above
background levels, we knowingly subject
those children to ongoing harm.
If no decision is taken over time to
lower the blood lead action level, then
fewer at-risk children will be identified.
This will ultimately impede community
efforts to utilize aggregate blood lead
testing data to investigate and identify
possible sources of lead exposure. It
also keeps parents, who may be living in
a contaminated environment, unaware
of lead hazards in their home.
CORRESPONDENCECorrespondence should be sent to Perry Gottes-feld, 4444 Geary Blvd, Suite 208, San Francisco, CA94118 (e-mail: [email protected]). Reprintscan be ordered at http://www.ajph.org by clickingthe “Reprints” link.
PUBLICATION INFORMATIONFull Citation: Gottesfeld P. Finding the next Flint:the need to update the blood lead reference value.Am J Public Health. 2021;111(10):1746–1749.
Acceptance Date: May 29, 2021.
DOI: https://doi.org/10.2105/AJPH.2021.306429
CONFLICTS OF INTERESTThe author serves as an expert witness in litigationregarding lead exposures.
REFERENCES
1. US Centers for Disease Control and Prevention.Low level lead exposure harms children: arenewed call of primary prevention. 2012. Avail-able at: https://www.cdc.gov/nceh/lead/ACCLPP/Final_Document_010412.pdf. Accessed May 11,2020.
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5. National Toxicology Program (NTP). NTP mono-graph: health effects of low-level lead. 2012.Available at: https://ntp.niehs.nih.gov/ntp/ohat/lead/final/monographhealtheffectslowlevellead_newissn_508.pdf. Accessed April 20, 2021.
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14. Cluett R, Fleisch A, Decker K, Frohmberg E, SmithAE. Findings of a statewide environmental leadinspection program targeting homes of childrenwith blood lead levels as low as 5 mg/dL. J PublicHealth Manag Pract. 2019;25(1):S76–S83. https://doi.org/10.1097/PHH.0000000000000869
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18. Agency for Toxic Substances and Disease Registry.Health consultation: historical blood lead levels inEast Chicago, Indiana neighborhoods impacted bylead smelters. August 16, 2018. Available at:https://www.atsdr.cdc.gov/HAC/pha/USSmelterandLeadRefinery/US_Smelter_Lead_Refinery_HC_2018-508.pdf. Accessed May 11,2020.
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