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

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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

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Editorial Gottesfeld 1747

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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.

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