"The Racial Ecology of Lead Poisoning: Toxic Inequality in Chicago Neighborhoods, 1995-2013 - Robert J. Sampson, Alix S. Winter"

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THE RACIAL ECOLOGY OF LEAD
POISONING
Toxic Inequality in Chicago Neighborhoods,
1995-2013
Robert J. Sampson
Department of Sociology , Harvard University
Alix S. Winter
Department of Sociology , Harvard University
Abstract
This paper examines the racial ecology of lead exposure as a form of environmental inequity,
one with both historical and contemporary significance. Drawing on comprehensive data from
over one million blood tests administered to Chicago children from 1995-2013 and matched
to over 2300 geographic block groups, we address two major questions: (1) What is the
nature of the relationship between neighborhood-level racial composition and variability
in children’s elevated lead prevalence levels? And (2) what is the nature of the relationship
between neighborhood-level racial composition and rates of change in children’s prevalence
levels over time within neighborhoods? We further assess an array of structural explanations
for observed racial disparities, including socioeconomic status, type and age of housing,
proximity to freeways and smelting plants, and systematic observations of housing decay
and neighborhood disorder. Overall, our theoretical framework posits lead toxicity as a major
environmental pathway through which racial segregation has contributed to the legacy of
Black disadvantage in the United States. Our findings support this hypothesis and show
alarming racial disparities in toxic exposure, even after accounting for possible structural
explanations. At the same time, however, our longitudinal results show the power of public
health policies to reduce racial inequities.
Keywords: Lead Poisoning , Inequality , Segregation , Neighborhoods , Chicago ,
Public Health
INTRODUCTION
The link between racial segregation and multiple social adversities is a central feature of
the American landscape. A well-documented fact is the nexus of concentrated poverty
and the spatial isolation of African Americans (Massey and Denton, 1993 ; Wilson [1987]
2012 ), a connection that spans decades and remains stubbornly persistent. Nation-
wide, for example, close to a third of Black children born between 1985 and 2000
Du Bois Review, (2016) Page 1 of 23 .
© 2016 Hutchins Center for African and African American Research 1742-058X/16 $15.00
doi:10.1017/S1742058X16000151
1
THE RACIAL ECOLOGY OF LEAD
POISONING
Toxic Inequality in Chicago Neighborhoods,
1995-2013
Robert J. Sampson
Department of Sociology , Harvard University
Alix S. Winter
Department of Sociology , Harvard University
Abstract
This paper examines the racial ecology of lead exposure as a form of environmental inequity,
one with both historical and contemporary significance. Drawing on comprehensive data from
over one million blood tests administered to Chicago children from 1995-2013 and matched
to over 2300 geographic block groups, we address two major questions: (1) What is the
nature of the relationship between neighborhood-level racial composition and variability
in children’s elevated lead prevalence levels? And (2) what is the nature of the relationship
between neighborhood-level racial composition and rates of change in children’s prevalence
levels over time within neighborhoods? We further assess an array of structural explanations
for observed racial disparities, including socioeconomic status, type and age of housing,
proximity to freeways and smelting plants, and systematic observations of housing decay
and neighborhood disorder. Overall, our theoretical framework posits lead toxicity as a major
environmental pathway through which racial segregation has contributed to the legacy of
Black disadvantage in the United States. Our findings support this hypothesis and show
alarming racial disparities in toxic exposure, even after accounting for possible structural
explanations. At the same time, however, our longitudinal results show the power of public
health policies to reduce racial inequities.
Keywords: Lead Poisoning , Inequality , Segregation , Neighborhoods , Chicago ,
Public Health
INTRODUCTION
The link between racial segregation and multiple social adversities is a central feature of
the American landscape. A well-documented fact is the nexus of concentrated poverty
and the spatial isolation of African Americans (Massey and Denton, 1993 ; Wilson [1987]
2012 ), a connection that spans decades and remains stubbornly persistent. Nation-
wide, for example, close to a third of Black children born between 1985 and 2000
Du Bois Review, (2016) Page 1 of 23 .
© 2016 Hutchins Center for African and African American Research 1742-058X/16 $15.00
doi:10.1017/S1742058X16000151
1
Robert J. Sampson and Alix S. Winter
were raised in high-poverty neighborhoods compared with just 1% of White chil-
dren (Sharkey 2013 ). The racial stratification of America’s urban neighborhoods is
not just about group differences in income—affluent Blacks typically live in poorer
neighborhoods than the average lower-income White resident (Perkins and Sampson,
2015 ). Black neighborhoods also disproportionately experience higher rates of unem-
ployment, single-parent families, teenage childbearing, violence, incarceration, and high
school dropout (Sampson 2012 ).
Less studied but equally important is the neighborhood divide by race in the fun-
damentals of physical health and well-being. As with compounded social deprivation,
indicators of compromised health, such as infant mortality, low birth weight, heart
disease, and cancer, tend to be the highest in racially-segregated, poor neighborhoods
(Krieger 2014 ; Williams and Collins, 2001 ). The recognition that Black neighbor-
hoods endure a disproportionate share of physical health burdens is not new. Over a
hundred years ago, W. E. B. Du Bois demonstrated that Blacks in Philadelphia dwelled
“in the most unhealthful parts of the city” (1899, p. 148). Near the middle of the twen-
tieth century, St. Clair Drake and Horace Cayton mapped “disease and death” (1945,
p. 205) in Black Metropoli s, revealing higher rates of tuberculosis and infant mortality
in Chicago’s Black communities. Although health conditions have generally improved
since these classic works, contemporary research largely confirms that Black neighbor-
hoods still rank higher on multiple indicators of poor physical health (Acevedo-Garcia
and Lochner, 2003 ).
Yet as the crisis in Flint Michigan revealed (Goodnough 2016 ), there is a major
health scourge that has not been subjected to the same analytic scrutiny at the neigh-
borhood level as other health indicators—lead poisoning. Unlike longstanding health
concerns, it was not until relatively recently that a sizable body of research built up
and converged in concluding that lead is a major neurotoxin that impairs cognitive,
physical, and behavioral functioning, even at relatively low levels (Rogan and Ware,
2003 ). As the National Research Council argued just over twenty years ago: “Science
and society have been remarkably slow to recognize and respond to the full range of
harm associated with lead exposure” (1993, p.1). So too, we argue, have science and
society been slow to recognize the racial ecology of lead poisoning as a major form
of health inequality. In particular, although Black children have been shown to be
at higher risk of lead exposure than White or Hispanic children (Lanphear et al.,
1996 ), surprisingly little research has systematically examined the magnitude of lead
poisoning in minority communities. The structural sources of racial disparities in lead
poisoning at the neighborhood level are also sparsely researched. And just as impor-
tant, there is little, if any, research that explores whether the large rates of decline in
lead exposure since the 1990s have been evenly experienced in Black, Hispanic, and
White communities.
Our paper fills this void by exploring the racial stratification of lead exposure
as an underappreciated source of ecological inequity, one with both historical and
contemporary significance. Drawing on comprehensive data from over one million
blood tests administered to Chicago children compiled over the years 1995-2013 and
matched to over 2300 geographic block groups, we address two major questions:
(1) What is the nature of the relationship between neighborhood-level racial compo-
sition and variability in children’s elevated lead prevalence levels? And (2) what is the
nature of the relationship between neighborhood-level racial composition and rates
of change of children’s prevalence levels within neighborhoods? We enlist a rich set
of structural covariates that may explain observed racial disparities, including socio-
economic status, type and age of housing structures, proximity to freeways and smelt-
ing plants, and videotaped observations of housing decay and neighborhood disorder.
:
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SOCIAL SCIENCE RESEARCH ON RACE 2016
The Racial Ecology of Lead Poisoning
Overall, our theoretical framework posits lead toxicity as an environmental pathway
through which racial segregation has contributed to the legacy of racial inequality in
the United States. Our findings support this claim and show alarming racial disparities
in toxic exposure. But at the same time, our longitudinal results show the power of public
health policies to reduce racial inequities.
THE ECOLOGY OF TOXIC INEQUALITY
The science of lead poisoning has evolved sharply in recent decades. Although lead
was recognized to have potentially harmful effects since the beginning of the twentieth
century, research pinpointing its consequences for children’s psychological, behav-
ioral, and cognitive development coalesced in the 1970s (Needleman et al., 1979 ).
Since then, evidence of a direct relationship between early childhood lead exposure
and developmental outcomes has accumulated at a rapid pace, especially with respect
to cognitive functioning (Bellinger et al., 1991 ) and antisocial behavior (Needleman
et al., 1996 ). The threshold at which lead exposure is considered to be safe has also
been continually lowered. By 1991, the Centers for Disease Control and Prevention
(CDC) recommended monitoring for children with blood lead levels (BLL) ≥ 10 μg/dL.
However, researchers subsequently showed negative consequences among children
with even lower levels of exposure (Canfield et al., 2003 ). Bruce Lanphear and col-
leagues summarize the shift in thinking: “The impact of low-level environmental lead
exposure on the health of the public is substantial” (2005, p. 899). In 2012, the CDC
went further to declare that there is no safe level of lead exposure, changing its rec-
ommendation to BLL ≥ 5 μg/dL as the “reference level” at which children should be
monitored.
The bulk of research to date has focused on the sources and consequences of
elevated BLL at the individual level. In nationally-representative samples, non-
Hispanic Black children and Mexican American children have consistently exhib-
ited higher prevalence rates of elevated BLL ( ≥ 10 μg/dL) than non-Hispanic White
children (Jones et al., 2009 ; Pirkle et al., 1998 ). From 1999-2004, the prevalence
rates of BLL ≥ 10 μg/dL among non-Hispanic Blacks, Mexican Americans, and
non-Hispanic Whites were 0.03, 0.01, and 0.01, respectively, having declined from
0.11, 0.04, and 0.02 in 1991-1994 (Jones et al., 2009 ). Racial disparities in BLL at
the individual level have been found to be partially attributable to differences in
exposure from the home environment and surrounding soil, as the homes of Black
children tend to be in worse physical condition (e.g., peeling paint) than those of
White children (Lanphear et al., 1996 ).
A small but growing body of work has considered the relationship between neigh-
borhood characteristics, such as poverty rate or racial composition, and individuals’
BLL (e.g., Lanphear et al., 1998 ). Only a limited number of studies have examined
ecological prevalence rates of elevated BLL and their correlates, and even fewer
have done so longitudinally. In Rhode Island, for example, researchers found relation-
ships between prevalence rates of BLL ≥ 10 μg/dL in 1994-1996, as measured at
the individual level by the Rhode Island Department of Health and aggregated by
the researchers, and measures from the 1990 Census of neighborhood socioeconomic
status, including poverty and unemployment rates, as well as the age of housing stock
at both the block group and Census tract levels (Krieger et al., 2003a ). Another study
in North Carolina posited that clusters of elevated BLL in rural counties with larger
Black populations stem from Black families’ occupancy of deteriorating homes with
lead-based paint that were first built by wealthy White families who have since moved
:
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Robert J. Sampson and Alix S. Winter
away (Hanchette 2008 ). Nationally, a positive relationship has been found between
the percentage of Black children under age sixteen and average air lead concentrations
at the county level, while the percentage of White youth were found to be inversely
related to air lead concentrations (Stretesky 2003 ). Finally, Tonny Oyana and Florence
Margai ( 2010 ) identified “hot spots” of high prevalence rates of BLL ≥ 10 μg/dL in
Chicago. The Westside, Southside, and Far Southside areas had the highest risks of
elevated BLL in 1997, 2000, and 2003, and were associated with lower median house-
hold incomes, older housing stock, and higher percentages of Black, Hispanic, and
Asian residents.
Research Framework and Questions
Although prior studies signal a neighborhood-level relationship between racial com-
position and prevalence rates of elevated BLL, important questions remain. For one,
there are few systematic data on the magnitude of lead poisoning in Black communi-
ties both before and after public housing and health departments undertook large-
scale efforts at lead abatement in housing. The evidence we do have shows that the
prevalence of lead poisoning reached extraordinary levels in certain inner-city contexts
as recently as the 1990s. Oyana and Margai ( 2010 ), for example, discovered that over
75% of children in some Westside communities of Chicago surpassed CDC guide-
lines for BLL. We build on this finding by exploring the prevalence of lead poisoning
across all neighborhoods in Chicago over a nineteen year period, 1995-2013. We
document and map the geographic concentration of both initial levels and rates of
decline in lead poisoning.
Second, we explore the nature of the relationship between lead toxicity and racial
composition. We are guided by research on neighborhood effects and the link between
the spatial foundations of inequality and racial stratification. As noted above, a long-
standing finding in the United States is that Black disadvantage relative to Whites is
sustained in large part by the connection between segregation and concentrated
poverty—what Douglas Massey and Mitchell Eggers ( 1990 ) term the ecology of
inequality. In this respect, neighborhood effects are a major source of how endur-
ing racial inequality is produced and maintained (Sampson 2012 ; Sharkey 2013 ). The
ecology of inequality has major theoretical implications for health as well, exempli-
fied in Massey’s ( 2004 ) biosocial model of stratification. He advances environmental
stress as a major example of how racial inequality gets into the body to produce allo-
1
static load.
Specifically, the wear and tear associated with life in under-resourced and
violent neighborhoods to which African Americans are disproportionately exposed
are hypothesized to translate into elevated rates of physical and mental health prob-
lems, deficits in cognitive skill development, and disrupted capacity for learning.
A body of recent research supports this hypothesis and shows how incidents of extreme
violence undermine children’s cognitive functioning and behavior in school, with con-
sequences for short-term academic performance and long-term developmental trajec-
tories (Sharkey and Sampson, 2015 ).
We extend these ideas to conceptualize toxic inequality at the neighborhood level
and empirically examine the magnitude of the association between the spatial isola-
tion of African Americans and the prevalence of lead poisoning. We also assess a set
of theoretically-plausible mechanisms that may account for this association. Further,
we explore the nature of neighborhood-level rates of decline in lead exposure since
policy efforts to eradicate lead paint in housing were ramped up in the mid-1990s,
specifically asking: (1) Has the racial gap in lead exposure remained persistent
in an era of substantial declines overall? And (2) have declines been unevenly
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The Racial Ecology of Lead Poisoning
experienced across communities of color? By directly addressing these questions and
examining the racial ecology of both persistence and change in lead toxicity across
neighborhoods, we are able to decompose the critical features of a major health hazard
in the contemporary era.
DATA, MEASURES, AND ANALYTIC STRATEGY
We begin by painting a descriptive portrait of the prevalence of elevated BLL in
Chicago across neighborhoods and over time. To measure neighborhood-level lead
toxicity, we use lead test results from the Chicago Department of Public Health
(CDPH) for all children ages one through five tested for lead exposure by “block
group” and year from 1995-2013. Block groups are relatively compact groupings, in
ecological terms, and include just over 1000 people, on average, in Chicago, making
them an appropriate unit for examining neighborhood-level exposure to lead. The
BLLs of children in Chicago are tested following a recommended schedule of four
tests by thirty-six months of age, with additional testing until six years of age if
needed. The majority of lead tests are conducted using venous blood samples, and
the remainder using capillary blood samples. The CDPH data include approximately
77,500 lead tests per year, ranging from 54,703 in 1995 to 84,232 in 2009, with an
average of thirty-three (SD = 32) lead tests per block group per year. The data allow
us to estimate the number of children in each block group-year with BLL ≥ 6 μg/dL
and BLL ≥ 10 μg/dL. In light of the CDC’s most recent recommendation of BLL
≥ 5 μg/dL as the level “of concern” as well as recent findings indicating the conse-
quences of low levels of exposure (Chiodo et al., 2004 ), we focus on children with
BLL ≥ 6 μg/dL. For comparison, we also calculated yearly block group-level preva-
lence rates of BLL ≥ 10 μg/dL.
To examine variation in the prevalence rates of elevated BLL across Chicago’s
neighborhoods, we map the prevalence rates of BLL ≥ 6 μg/dL for the 2223 block
groups for which we have CDPH data for 1995. To examine change in prevalence
rates over time, we then convert each block group’s annual prevalence rates (45,229 block
group-year pairs) to annual prevalence rates using a three-year moving average. We use
these moving averages to calculate average block group-level prevalence rates of ele-
vated BLL for each year, 1996-2012.
Having uncovered the overall neighborhood-level trend in lead toxicity over
time, we next begin to unpack whether and how this trend varies by neighborhood-
level racial composition. We matched our block group-level prevalence rates of
elevated BLL to block group data on racial/ethnic composition, obtained from the
1990 Decennial Census, and calculated the proportion of individuals in each block
group who identify as non-Hispanic White, as non-Hispanic Black, or as Hispanic.
We then calculate average, neighborhood-level prevalence rates for each year, strat-
ified by neighborhood racial/ethnic composition (44,681 block group-year pairs),
measured by whether block groups are predominantly ( ≥ 70%) non-Hispanic White
(29.3% of block group-year pairs), non-Hispanic Black (38.2% of block group-year
pairs), or Hispanic (6.8% of block group-year pairs). Since absolute levels of preva-
lence rates changed across our study period, we also examine which block groups fall
within each year’s top quintile of prevalence rates, allowing for a consistent compari-
son of the racial/ethnic compositions of the neighborhoods with the highest elevated
BLL over time.
In the second phase of our analysis, we use hierarchical linear models (HLM) to
assess whether neighborhoods’ longitudinal trajectories of prevalence vary significantly
:
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