EPA/600/R-23/375
APDA Environmental Protection Januaiy 2024
M m Agency www.epa.eov/isap
Integrated Science
Assessment for Lead
Appendix 10: Cancer
January 2024
Center for Public Health and Environmental Assessment
Office of Research and Development
U.S. Enviromnental Protection Agency
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DISCLAIMER
This document has been reviewed in accordance with the U.S. Environmental Protection Agency
policy and approved for publication. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
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DOCUMENT GUIDE
This Document Guide is intended to orient readers to the organization of the Lead (Pb) Integrated
Science Assessment (ISA) in its entirety and to the sub-section of the ISA at hand (indicated in bold). The
ISA consists of the Front Matter (list of authors, contributors, reviewers, and acronyms), Executive
Summary, Integrated Synthesis, and 12 appendices, which can all be found at https://assessments.epa.gov/
isa/document/&deid=3 59536.
Front Matter
Executive Summary
Integrated Synthesis
Appendix 1. Lead Source to Concentration
Appendix 2. Exposure, Toxicokinetics, and Biomarkers
Appendix 3. Nervous System Effects
Appendix 4. Cardiovascular Effects
Appendix 5. Renal Effects
Appendix 6. Immune System Effects
Appendix 7. Hematological Effects
Appendix 8. Reproductive and Developmental Effects
Appendix 9. Effects on Other Organ Systems and Mortality
Appendix 10. Cancer
Appendix 11. Effects of Lead in Terrestrial and Aquatic Ecosystems
Appendix 12. Process for Developing the Pb Integrated Science Assessment
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CONTENTS
DOCUMENT GUIDE 10-iii
LIST OF TABLES 10-v
LIST OF FIGURES 10-vi
ACRONYMS AND ABBREVIATIONS 10-vii
APPENDIX 10 CANCER 10-1
10.1 Introduction and Summary of the 2013 Pb ISA 10-1
10.2 Scope 10-3
10.3 Mechanistic Pathways and Markers of Carcinogenesis 10-4
10.3.1 Introduction 10-4
10.3.2 Animal Models of Carcinogenicity 10-5
10.3.3 Genotoxicity 10-6
10.3.4 Oxidative Stress 10-7
10.3.5 Cell Viability, Cytotoxicity, Apoptosis 10-8
10.3.6 DNA Damage Repair Enzymes and Gene Expression 10-8
10.3.7 Epigenetic Regulation of Gene Expression 10-9
10.3.8 Gene Expression and Extracellular Matrix 10-10
10.3.9 Inflammation 10-10
10.3.10 Summary of Mechanistic Pathways and Markers of Carcinogenesis 10-11
10.4 Cancer Incidence and Mortality 10-11
10.4.1 Epidemiologic Studies of Overall Cancer Incidence 10-12
10.4.2 Epidemiologic Studies of Overall Cancer Mortality 10-12
10.4.3 Epidemiologic Studies of Lung Cancer 10-13
10.4.4 Epidemiologic Studies of Brain Cancer 10-13
10.4.5 Epidemiologic Studies of Breast Cancer 10-14
10.4.6 Epidemiologic Studies of Other Cancer 10-14
10.4.7 Summary of Cancer Incidence and Mortality 10-16
10.5 Biological Plausibility 10-18
10.6 Summary and Causality Determination 10-22
10.7 Evidence Inventories - Data Tables to Summarize Study Details 10-28
10.8 References 10-41
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LIST OF TABLES
Table 10-1 Summary of evidence for a likely to be causal relationship between Pb exposure and
cancer 10-25
Table 10-2 Epidemiologic studies of exposure to Pb and cancer effects 10-28
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LIST OF FIGURES
Figure 10-1 Potential biological pathways for cancer from exposure to Pb. 10-19
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ACRONYMS AND ABBREVIATIONS
ALAD S-aminolevulinic acid dehydratase
AQCD Air Quality Criteria Document
APE-1 human AP endonuc lease
BLL blood lead level
BMI body mass index
BW body weight
Cd cadmium
CGI CpG island
CI confidence interval
CLL chronic lymphatic lymphoma
CLL/SLL chronic lymphocytic leukemia/small
lymphocytic lymphoma
CPS Cancer Prevention Study
CRP C-reactive protein
d day(s)
DLBCL diffuse large B-cell lymphoma
EPIC European Prospective Investigation
into Cancer and Nutrition
FL follicular lymphoma
GFAAS graphite furnace atomic absorption
spectrometry
GFR glomerular filtration rate
HR hazard ratio
ICD International Classification of Diseases
ICP-MS inductively coupled plasma mass
spectrometry
IC50 half maximal inhibitory concentration
IARC International Agency for Research on
Cancer
IL interleukin type
ISA Integrated Science Assessment
KNHANES Korea National Health and Nutrition
Examination Survey
LINE long interspersed nuclear elements
In natural log
MM multiple myeloma
MMP matrix metalloproteinase-
NHANES National Health and Nutrition
Examination Survey
NHL non-Hodgkin lymphoma
NSDHS Northern Sweden Health and Disease
Study
NTP National Toxicology Program
OR odds ratio
Pb lead
PCR polymerase chain reaction
PECOS Population, Exposure, Comparison,
Outcome, and Study Design
PIR poverty-income ratio
PND postnatal day
ppm parts per million
PRMT protein arginine methyltransferase
Q quartile
RR relative risk
ROS reactive oxygen species
SCE sister chromatid exchange
SD standard deviation
Se selenium
TK thymidine kinase type
UC urothelial carcinoma
WHO World Health Organization
Zn zinc
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APPENDIX 10 CANCER
Summary of Causality Determinations for Pb Exposure and Cancer
This appendix characterizes the scientific evidence that supports the causality
determination for lead (Pb) exposure and cancer. The types of studies evaluated within
this appendix are consistent with the overall scope of the ISA as detailed in the Process
Appendix (see Section 12.4). In assessing the overall evidence, the strengths and
limitations of individual studies were evaluated based on scientific considerations
detailed in Table 12-5 of the Process Appendix (Section 12.6.1). More details on the
causal framework used to reach these conclusions are included in the Preamble to the
ISA (U.S. EPA, 2015). The evidence presented throughout this appendix supports the
following causality conclusion:
Outcome
Causality Determination
Cancer
Likely to be Causal
The Executive Summary, Integrated Synthesis, and all other appendices of this Pb ISA
can be found at https://assessments.epa.gov/isa/document/&deid=359536.
10.1 Introduction and Summary of the 2013 Pb ISA
This appendix evaluates the toxicological and epidemiologic literature related to the potential
contributions of Pb exposure to cancer effects, including cancer incidence and mortality. The 2013
Integrated Science Assessment for Lead (hereinafter referred to as the 2013 Pb ISA) continued to support
the conclusions of the 2006 Pb Air Quality Criteria Document (AQCD) that Pb is a well-established
animal carcinogen (U.S. EPA, 2013, 2006). In the 2013 Pb ISA (U.S. EPA, 2013), the toxicological
literature provided consistent evidence of the carcinogenic potential of Pb and possible contributing
modes of action, including genotoxic, mutagenic, and epigenetic effects. The development of cancer is a
multistep process that involves the progressive accumulation of mutations, leading to upregulation of
oncogenes and loss of function of tumor suppressor genes resulting in uncontrolled cell growth and
invasion of cancer cells within organ tissue. Based on the toxicological literature reviewed in the 2013 Pb
ISA, Pb appears to have some ability to induce DNA damage. Additionally, Pb has the ability to alter
gene expression through epigenetic mechanisms and interact with proteins, which may be another
potential means by which Pb induces carcinogenicity (U.S. EPA, 2013). Pb may act at a post-translational
stage to alter protein structure of zinc (Zn)-finger proteins, which can in turn alter gene expression, DNA
repair, and other cellular functions. In summary, cancer develops from one or a combination of multiple
mechanisms including modification of DNA via epigenetics or enzyme dysfunction and genetic instability
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or mutation. These modifications then provide cancer cells with a selective growth advantage and thus, Pb
may contribute to epigenetic changes and chromosomal aberrations.
Multiple longitudinal epidemiologic studies reviewed in the 2013 Pb ISA (U.S. EPA. 2013)
examined the associations between cancer incidence and mortality and Pb exposures, estimated with
biological measures and exposure databases. The 2013 Pb ISA (U.S. EPA. 2013) reported mixed results
for cancer mortality studies. While a high-quality National Health and Nutrition Examination Survey
(NHANES) study demonstrated an association between blood Pb and increased risk of cancer mortality,
other studies reported weak or null associations. Overall, the epidemiologic studies reviewed in the 2013
Pb ISA were well-conducted with control for important potential confounders such as age, smoking, and
education. The epidemiologic studies of cancer incidence in the 2013 Pb ISA reported no associations
between various measures of Pb and overall cancer incidence. These studies were limited by their
ecological or cross-sectional study designs and a few studies did not collect biological measurements, nor
did they control for potential confounders. Additionally, consistent evidence from animal toxicological
studies demonstrated that Pb exposures can lead to cancer, genotoxicity, or epigenetic modification.
Carcinogenicity in animal toxicology studies of Pb exposure were reported in the kidneys, testes, brain,
adrenals, prostate, pituitary, and mammary glands, albeit at high doses of Pb. Furthermore, based on the
previous existing bodies of evidence, International Agency for Research on Cancer (IARC) has classified
inorganic Pb compounds as "probably carcinogenic to humans"1 and the National Toxicology Program
(NTP) has listed Pb and Pb compounds as "reasonably anticipated to be human carcinogen/'2 Overall, the
consistent and strong body of evidence from toxicological studies on tumor incidence and potential modes
of action, when considered together with the inconsistent epidemiologic evidence, was judged sufficient
to conclude that there is likely to be a causal relationship between Pb exposure and cancer.
'The International Agency for Research on Cancer (IARC) classifies carcinogens into four groups. The
categorization of "probably carcinogenic to humans" (Group 2A) applies when IARC has made at least two of the
following evaluations, including at least one that involves either exposed to humans or human cells or tissues:
limited evidence of carcinogenicity in humans; sufficient evidence of carcinogenicity in experimental animals; and
strong evidence that the agent exhibits key characteristics of carcinogens. If there is inadequate evidence of
carcinogenicity in humans, there should be strong evidence in human cells or tissues that the agent exhibits key
characteristics of carcinogens. More information on IARC cancer classifications can be found in the IARC
Monographs on the Identification of Carcinogenic Hazards to Humans Preamble (IARC. 2019).
2The National Toxicology Program (NTP) prepares the Report on Carcinogens (RoC) on behalf of the Secretary of
Health and Human Services and follows an established, multi-step process for the review and evaluation of selected
substances. The classification of "Reasonably Anticipated to be Human Carcinogen" is defined as limited evidence
of carcinogenicity from studies in humans, which indicates that causal interpretation is credible, but that alternative
explanations, such as chance, bias, or confounding factors, could not adequately be excluded; or there is sufficient
evidence of carcinogenicity from studies in experimental animals, which indicates there is an increased incidence of
malignant and/or a combination of malignant and benign tumors (1) in multiple species or at multiple tissue sites, or
(2) by multiple routes of exposure, or (3) to an unusual degree with regard to incidence, site, or type of tumor, or age
at onset; or there is less than sufficient evidence of carcinogenicity in humans or laboratory animals; however, the
agent, substance, or mixture belongs to a well-defined, structurally related class of substances whose members are
listed in a previous Report on Carcinogens as either known to be a human carcinogen or reasonably anticipated to be
a human carcinogen, or there is convincing relevant information that the agent acts through mechanisms indicating it
would likely cause cancer in humans (NTP. 2023).
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10.2 Scope
The scope of this appendix is defined by Population, Exposure, Comparison, Outcome, and Study
Design (PECOS) statements. The PECOS statements define the objectives of the review and establish
study inclusion criteria thereby facilitating identification of the most relevant literature to inform the Pb
ISA.3 In order to identify the most relevant literature, the body of evidence from the 2013 Pb ISA was
considered in the development of the PECOS statements for this Appendix. Specifically, well-established
areas of research; gaps in the literature; and inherent uncertainties in specific populations, exposure
metrics, comparison groups, and study designs identified in the 2013 Pb ISA inform the scope of this
Appendix. The 2013 Pb ISA used different inclusion criteria than the current ISA, and the studies
referenced therein often do not meet the current PECOS criteria (e.g., due to higher or unreported
biomarker levels). Studies that were included in the 2013 Pb ISA, including many that do not meet the
current PECOS criteria, are discussed in this appendix to establish the state of the evidence prior to this
assessment. With the exception of supporting evidence used to demonstrate the biological plausibility of
Pb-associated cancer incidence and mortality, recent studies were only included if they satisfied all
components of the following discipline-specific PECOS statements:
Epidemiologic Studies:
Population: Any human population, including specific populations or lifestages that might be at
increased risk of a health effect.
Exposure: Exposure to Pb4 as indicated by biological measurements of Pb in the body - with a
specific focus on Pb in blood, bone, and teeth; validated environmental indicators of Pb
exposure5; or intervention groups in randomized trials and quasi-experimental studies.
Comparison: Populations, population subgroups, or individuals with relatively higher versus
lower levels of the exposure metric (e.g., per unit or log unit increase in the exposure metric,
or categorical comparisons between different exposure metric quantiles).
Outcome: Cancer incidence and cancer mortality.
3The following types of publications are generally considered to fall outside the scope and are not included in the
ISA: review articles (which typically present summaries or interpretations of existing studies rather than bringing
forward new information in the form of original research or new analyses), Pb poisoning studies or clinical reports
(e.g., involving accidental exposures to very high amounts of Pb described in clinical reports that may be extremely
unlikely to be experienced under ambient air exposure conditions), and risk or benefits analyses (e.g., that apply
concentration-response functions or effect estimates to exposure estimates for differing cases).
4Recent studies of occupational exposure to Pb were considered insofar as they addressed a topic area that was of
particular relevance to the National Ambient Air Quality Standards (NAAQS) review (e.g., longitudinal studies
designed to examine recent versus historical Pb exposure).
5Studies that estimate Pb exposure by measuring Pb concentrations in particulate matter with a nominal mean
aerodynamic diameter less than or equal to 10 |im3 (PMio) and particulate matter with a nominal mean aerodynamic
diameter less than or equal to 2.5 |im3 (PM2.5) ambient air samples are only considered for inclusion if they also
include a relevant biomarker of exposure. Given that size distribution data for Pb-PM are fairly limited, it is difficult
to assess the representativeness of these concentrations to population exposure [Section 2.5.3 (U.S. EPA. 2013)1.
Moreover, data illustrating the relationships of Pb-PMio and Pb-PNfc.s with blood Pb levels (BLL) are lacking.
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Study Design: Epidemiologic studies consisting of longitudinal and retrospective cohort studies,
case-control studies, cross-sectional studies with appropriate timing of exposure for the health
endpoint of interest, randomized trials and quasi-experimental studies examining
interventions to reduce exposures.
Experimental Studies:
Population: Laboratory nonhuman mammalian animal species (e.g., mouse, rat, Guinea pig,
minipig, rabbit, cat, dog) of any lifestage (including preconception, in utero, lactation,
peripubertal, and adult stages).
Exposure: Oral, inhalation, or intravenous routes administered to a whole animal (in vivo) that
results in a (blood lead level) BLL of 30 (ig/dL or below" 7
Comparators: A concurrent control group exposed to vehicle-only treatment or untreated
control.
Outcome: Cancer and cancer-related outcomes, such as genotoxicity, epigenetic, and mutagenic
effects.
Study design: Controlled exposure studies of animals in vivo. In vitro mechanistic studies are
supplemental evidence.
10.3 Mechanistic Pathways and Markers of Carcinogenesis
10.3.1 Introduction
The 2013 Pb ISA (U.S. EPA. 2013) reported consistent positive evidence from multiple animal
chronic Pb exposure studies ranging in duration between 18 months to 2 years as well as from animal
studies involving windows of Pb exposure such as gestation and lactation leading to cancers in adult
offspring. Additionally, consistent mechanistic and genotoxicity evidence for cellular and DNA damage
from multiple lines of evidence (human and animal in vitro models) provided further support for
mechanistic pathways of Pb inducing carcinogenicity. The mechanistic toxicological literature evaluated
in the 2013 Pb ISA (U.S. EPA. 2013) found that most evidence clearly supports Pb-induced
carcinogenicity in animal models, but the exact chain of events supporting a mode of action has not been
completely characterized. Furthermore, the IARC (IARC. 2006) classified inorganic Pb compounds as
"probably carcinogenic to humans" (Group 2A), while NTP listed Pb and Pb compounds as "reasonably
anticipated to be human carcinogens" (NTP. 2012). The reports from IARC and NTP based their
6Pb mixture studies are included if they employ an experimental arm that involves exposure to Pb alone.
7This level represents an order of magnitude above the upper end of the distribution of U.S. young children's BLLs.
The 95th percentile of the 2011-2016 National Health and Nutrition Examination Survey (NHANES) distribution of
BLL in children (1-5 years; n = 2,321) is 2.66 (ig/dL (Eganet al.. 2021) and the proportion of individuals with
BLLs that exceed this concentration varies depending on factors including (but not limited to) housing age,
geographic region, and a child's age, sex, and nutritional status.
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conclusion on evidence primarily from animal cancer bioassays of continuous exposure to Pb. While
no PECOS-relevant animal studies of Pb exposure and cancer have been published since the 2013 Pb
ISA, a number of recent in vitro studies have examined the potential mechanistic pathways by which
Pb exposure could result in cancer initiation and/or promotion. These mechanistic studies are evaluated
in more detail in the sections below: 10.3.2 Animal Models of Carcinogenicity; 10.3.3 Genotoxicity;
10.3.4 Oxidative Stress; 10.3.5 Cell Viability, Cytotoxicity, Apoptosis; 10.3.6 DNA Damage Repair
Enzymes and Gene Expression; 10.3.7 Epigenetic Regulation of Gene Expression; 10.3.8 Gene
Expression and Extracellular Matrix; and 10.3.9 Inflammation.
10.3.2 Animal Models of Carcinogenicity
The toxicological literature reviewed in previous AQCDs established that Pb has been shown to
act as a carcinogen in animal toxicology models, albeit at relatively high concentrations. Chronic oral Pb
acetate exposure for male and female rodents has consistently been shown to be a kidney carcinogen in
multiple separate studies, inducing adenocarcinomas and adenomas after chronic exposure. The kidneys
are the most common target of Pb-induced carcinogenicity (Kasprzak et al.. 1985; Koller et al.. 1985;
Azar et al.. 1973; Van Esch and Kroes. 1969). Other common targets of Pb-induced carcinogenicity
include the testes, brain, adrenals, prostate, pituitary, and mammary gland (IARC. 2006). The typical
cancer bioassays used by IARC or NTP as evidence of Pb-induced carcinogenicity were designed using
rodents, typically males but occasionally both sexes, that were continuously exposed to Pb acetate in
chow (i.e., 1,000 or 10,000 ppm Pb acetate) or drinking water (i.e., 26 or 2,600 ppm Pb acetate) for
18 months to two years in duration, the typical lifespan of a rodent (Kasprzak et al.. 1985; Koller et al..
1985; Azar et al.. 1973; Van Esch and Kroes. 1969).
The 2013 Pb ISA (U.S. EPA. 2013) focused on the importance of exposure windows for Pb-
induced cancer bioassays in animal toxicology models. Gestational and lactational exposure of rats to
inorganic Pb-induced (500, 750 or 1,000 ppm Pb acetate in drinking water) carcinogenicity in adult
offspring (Waalkes et al.. 1995). In another study, Tokar et al. (2010) considered Pb-induced
carcinogenesis in mice with early life Pb exposure (gestation, lactation and continued until 8 weeks of
age) and examined tumorigenesis in homozygous metallothionein I/II knockout mice and their
corresponding wild-type controls (groups of ten mice each). The dams/mothers were exposed by drinking
water to 2,000 or 4,000 ppm Pb acetate in utero, through birth and lactation, and then, postnatally, to
drinking water until 8 weeks old and compared with untreated controls. The Pb-exposed metallothionein
I/II knockout mice had increased testicular teratomas and renal and urinary bladder preneoplasia. The
tumor burdens of Pb-exposed wild-type mice were not statistically significantly different than controls.
The data suggest that metallothionein can protect against Pb-induced tumorigenesis. The study did not
address whether metallothionein in humans would have any impact on Pb-induced carcinogenesis. The
animal toxicology studies show that Pb is a well-established animal carcinogen in studies employing
high-dose Pb exposure over a continuous, extended duration of exposure (i.e., 2 years), which is typical of
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cancer bioassays. Studies show early-life maternal Pb exposure can contribute to carcinogenicity in
offspring and suggest that metallothionein is protective against cancer in this pathway.
Since the 2013 Pb ISA, there are no new PECOS-relevant animal studies that have examined
cancer endpoints. Several recent in vitro mechanistic studies have examined markers of potential
carcinogenicity pathways as characterized by the IARC 10 key characteristics of carcinogenic
mechanistic pathways (Smith et al.. 2016). These in vitro mechanistic studies, which are categorized as
supplemental under the PECOS criteria and do not abide by the blood Pb cutoff of 30 (ig/dL, are short-
term in nature, and principally inform mechanistic pathways that inform association to Pb exposure (see
Section 10.2). These in vitro mechanistic studies are detailed below in Sections 10.3.3-10.3.9.
10.3.3 Genotoxicity
Multiple toxicological and epidemiologic studies reviewed in the 2013 Pb ISA (U.S. EPA. 2013)
examined the relationship between Pb exposure and DNA and cellular damage. These studies reported
consistent evidence of genotoxicity, oxidative stress, and related gene expressions. Genotoxic effects are
effects from Pb exposure as measured by multiple lines of evidence such as DNA damage repair. In the
case of DNA strand break detection, in vivo and in vitro studies using the comet assay (measured by
multiple indices such as tail length, single cell electrophoresis, and others) yielded multiple positive
results in various species (Yediou et al.. 2010; Nava-Hernandez et al.. 2009; Tapisso et al.. 2009;
Alghazal et al.. 2008; Kermani et al.. 2008; Xu et al.. 2008; Gastaldo et al.. 2007; Xu et al.. 2006). The
toxicological evidence was supported by several epidemiologic studies that reported associations between
blood Pb and DNA and cellular damage (Khan et al.. 2010; Olewinska et al.. 2010; Shaik and Jamil.
2009; Wiwanitkit et al.. 2008; Duvdu et al.. 2005).
Since the 2013 Pb ISA (U.S. EPA. 2013). there have been additional supplemental studies using
comet assays that continue to indicate DNA strand breakage occurs after Pb exposure across multiple
species (Jiang et al.. 2020; Yadav et al.. 2019; Ali. 2018; Nariva et al.. 2018; Siddarth et al.. 2018; Shah et
al.. 2016; Ahmad et al.. 2015; Mckelvev et al.. 2015; Zhang et al.. 2014; Roy et al.. 2013; Shakoori and
Ahmad. 2013). In addition to DNA and cellular damage, there was a recent study of gamma-H2AX foci
formation from the phosphorylation of the Ser-139 residue of the histone variant H2AX, which is an early
cellular response to the induction of DNA double-strand breaks, with Pb exposure increased these foci
formation (Liu et al.. 2018).
The 2013 Pb ISA (U.S. EPA. 2013) noted Pb-induced micronucleus formation in both the
toxicological and epidemiologic studies reviewed (Shaik and Jamil. 2009; Tapisso et al.. 2009; Alghazal
et al.. 2008). The recently published literature contains multiple studies identifying Pb-induced
micronucleus formation in the human lymphoblastoid cell line (Alimba et al.. 2016) and in human
lymphocytes from healthy volunteers (Nariva et al.. 2018; Shah et al.. 2016; Roy et al.. 2013).
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Sister chromatid exchange (SCE), exchanges of homologous DNA material between chromatids
on a chromosome and are a test for mutagenicity or DNA damage as well as other chromosomal
aberrations in toxicological studies, was outlined extensively in the 2013 Pb ISA (U.S. EPA. 2013). In a
study of mice, the SCE in bone marrow was elevated after treatment with Pb acetate and increased in
time, with co-exposure to cadmium (Cd) or Zn further increasing SCE levels (Tapisso et al.. 2009).
Similarly, recent in vitro studies found Pb-induced damage both in cell lines (Alimba et al.. 2016;
Banfalvi. 2014) and in human peripheral blood lymphocytes (Yadav et al.. 2019; Nariva et al.. 2018; Shah
et al.. 2016).
10.3.4 Oxidative Stress
At cellular level, Pb is known to induce oxidative stress either by generation of free radicals or
through depletion of antioxidants (Ercal et al„ 2001). Pb-induced free radicals initiate DNA oxidation and
subsequent DNA damage (Hsu and Guo, 2002) as well as mitochondrial damage and intracellular
depletion of glutathione (Sabath and Robles-Osorio, 2012).
Since the 2013 Pb ISA, multiple studies have investigated Pb-induced oxidative stress and
diverse biomarkers in the context of genotoxicity and carcinogenic mechanisms. All these studies used
in vitro cell culture (human and mammalian animal) systems exposed to either Pb acetate or Pb nitrate of
varied concentrations/doses and durations. Some of these studies also examined the effect of antioxidant
treatment on the reversal of oxidative stress endpoints and of genotoxic endpoints resulting from Pb-
induced oxidative stress. Nariya et al. (2018) observed dose (Pb acetate; 0.379 |ig/m 1 and 37.9 (ig/ml) and
duration (24 or 69 hours) dependent increases in oxidative stress and genotoxicity (chromosomal
aberrations, micronuclei) and reversal of these effects when treated with antioxidant and anti-
inflammatory curcumin (1.43 (ig/ml). Similarly, Yadav et al. (2019) observed reversal of Pb nitrate (50-
350 |ig/m 1 for 24 hours) induced genotoxicity (as assessed by comet assay and sister chromatid exchange)
by pretreatment of human peripheral blood lymphocytes with antioxidant, anti-inflammatory
bioflavonoid, "morin'. at concentrations of 15-60 |ig/m 1.
Three recent studies evaluated Pb-induced oxidative stress and its effects on DNA damage. Liu et
al. (2018) used thymidine kinase (TK) 6 cells exposed to Pb acetate (0-480 mM) for 6-24 hours and
observed the formation of 8-OH guanosine adducts and gamma-H2AX foci, markers of DNA double-
strand breaks. Pottier et al. (2013) also observed a dose dependent (Pb-nitrate; 0-1000 mM) loss of
telomeres in clone B3 of the human EJ30 bladder carcinoma cell line. In these cells, formation of foci
(indicative of cell transformation) was found only above 100 mM Pb. Jiang et al. (2020) observed Pb-
induced DNA damage mediated by oxidative stress and inflammation mechanism in human lung cells at
no-observed-adverse-effect level of 4 (ig/ml Pb. Ali (2018) also observed Pb-induced DNA damage
mediated by oxidative stress in human lung cells at half maximal inhibitory concentration (IC50) dose of
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Pb. Furthermore, the IC50 dose of Pb-induced DNA damage was found to be reversed when treated with
antioxidants (i.e., vitamin E or garlic extract) (Ali. 20 IS).
10.3.5 Cell Viability, Cytotoxicity, Apoptosis
Toxicant-induced oxidative stress, if left uncontrolled or depleted of cellular antioxidant
resources, eventually leads to DNA or chromatin damage and cell death or apoptosis. Since the 2013 Pb
ISA, a limited number of in vitro cell culture studies that observed Pb-induced oxidative stress further
investigated cytotoxicity mechanisms. Ali (2018) found a dose dependent increase in cell viability and
cytotoxicity in association with Pb exposure. In addition, garlic, vitamin E, and the combination mitigated
these effects to different levels. The cytotoxicity was found to be associated with alterations in the
expression of pro-apoptotic genes (bcl2, Bax, P53) and significant increase in Bax/Bcl2 ratio suggesting
their role in an apoptotic mechanism of cytotoxicity. Jiang et al. (2020) also observed a dose-dependent
decrease in cell viability associated with changes in the expression of specific proapoptotic genes (caspase
3, 8, and 9). Similarly, Siddarth et al. (2018) observed increased expression of caspase 3 and an increased
number of annexin V positive cells by flow cytometric analyses, suggesting an apoptotic mechanism for
cell death. These studies also found reversal of these effects when treated with diverse antioxidants (see
Section 10.3.4 on oxidative stress). Ghosh et al. (2018) observed significant Pb chloride (5 mM and
10 mM) induced decreases in cell viability of A549 human lung and MCF-7 human breast cancer cell
lines as assessed by trypan blue exclusion, MTT assay, and neutral red dye uptake methods.
10.3.6 DNA Damage Repair Enzymes and Gene Expression
Cells are equipped with robust, diverse DNA damage response mechanisms consisting of specific
DNA repair pathways to remove damage and effect repair at different stages of the cell cycle. Since the
2013 Pb ISA, two in vitro studies have investigated the role of DNA damage repair enzymes by studying
their expression after Pb exposure. Mckelvey et al. (2015), using the RT2 Profiler polymerase chain
reaction (PCR) array system, found that exposure to Pb nitrate (40 |ig/m 1 and 80 |ig/m 1) impacted diverse
DNA damage and signaling pathways in the HepG2 (human hepatocellular carcinoma) cell line. These
investigations were carried out in the context of protection conferred by diverse chemical forms of
selenium (Se) to Pb-induced DNA damage. The potential role for the changes in genotoxicity was
complemented by the comet assay and other methods (discussed in Section 10.3.1). Both doses of Pb
nitrate led to increased expression of several genes and the study reported differential fold increases
between the 40 |ig/m 1 and 80 |ig/m 1 doses. The two most significant increases were found in the
expression of GADD45G (growth arrest and DNA-damage inducible, gamma) and PPP1R15A (protein
phosphatase 1, regulatory subunit 15 A) by 26- and 12-fold, respectively, in cells exposed at 40 mg/ml.
Smaller increases were reported in cells exposed at 80 mg/ml (4- and 6-fold, respectively). The ATM
gene that functions as a main sensor of DNA damage and is involved in DNA double-strand break (DSB)
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repair was found to be suppressed by Pb nitrate. In this study the protection conferred by diverse Se-based
compounds sodium selenite (Sel-Ni), selenium yeast (SeY), seleno-methionine (Sel-M), and sodium
selenate (Sel-Na) were also investigated in the gene expression of Pb-induced DNA repair enzymes. It
was observed that SeY and Sel-M influenced the Pb-induced expression of LIG1 (ligase I, DNA) and
XRCC3, two important genes involved in the base excision repair pathway, indicating that Pb-induced
oxidative stress might influence the expression and regulation of these enzymes and that these Se
compounds confer protection against it.
10.3.7 Epigenetic Regulation of Gene Expression
The 2013 Pb ISA reported that the ability of Pb to alter gene expression through epigenetic
mechanisms and to interact with proteins may be a means by which Pb induces carcinogenicity (Patch
2013; Li et al.. 2011; Wright et al.. 2010; Pilsner et al.. 2009). Cancer develops from one or a combination
of multiple mechanisms including modification of DNA via epigenetics or enzyme dysfunction and
genetic instability or mutation. These modifications can then provide the cancer cells with a selective
growth advantage, in which Pb may contribute to epigenetic changes and chromosomal aberrations.
Additionally, epigenetic modifications may lead to cancer by altering cellular functions without altering
the DNA sequence. The most studied epigenetic change is methylation alterations. A small number of
studies included in the 2013 Pb ISA show that Pb can induce epigenetic changes, but do not clearly tie
these effects to Pb-induced carcinogenesis and genotoxicity (Patel, 2013; Li et al., 2011; Wright et al.,
2010; Pilsner et al., 2009). Since the 2013 Pb ISA, additional studies have examined Pb-induced
epigenetic modifications and the degree to which these modifications may underlie Pb-induced
carcinogenicity. These studies are discussed below.
The role of epigenetic mechanisms such as DNA methylation (and demethylation), histone
modifications, and non-coding RNAs in the regulation of gene expression is well established. Promoter
methylation of DNA repair genes is a common event in tumorigenesis. Two recent in vitro cell culture
studies investigated the potential effects of Pb on epigenetic regulation of gene expression. Liu et al.
(2018), using methylation-specific PCR (M-PCR) that specifically enhances promoter methylation,
investigated TK-6 cells exposed to Pb acetate at different time points. Expression of several DNA repair
genes (XRCC1, hOGG-1, BRCA1, and XPD) was inhibited in this assay, suggesting a role for alterations
in methylation profiles of these genes.
Histone and non-histone proteins are methylated by a family of protein arginine methyltransferase
(PRMT) enzymes. One of the isoforms of this enzyme, PRMT5, is an oncogene and plays a critical role in
cancer progression by promoting cell proliferation and inhibiting apoptosis; moreover, it is overexpressed
in many forms of human cancers (Dai et al., 2022; Stopa et al., 2015; Bao et al., 2013; Nicholas et al„
2013). Using in vitro culture systems (A549 and MCF-7 cell lines) exposed to Pb chloride (5 and 10 |iM)
for 24 and 48 hours, Ghosh et al. (2018) investigated Pb-induced, global DNA hypomethylation and
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methylation status specific to PRMT5 promoter CpG islands (CGIs). Pb-chloride exposure was found to
reduce global methylation levels and either completely or partially demethylate only the upstream
PRMT5 promoter CGI. Additional confirmational studies using bisulfite sequencing indicated an
approximately five-fold reduction in the methylation by Pb chloride. These two recent studies (Ghosh et
al.. 2018; Liu et al.. 2018) suggest the potential for Pb exposure to alter epigenetic control of gene
expression.
10.3.8 Gene Expression and Extracellular Matrix
A single recent study examined gene expression related to cancer progression as assessed by
epithelial-to-mesenchymal transition and invasiveness in Renca cells, a murine renal cortical
adenocarcinoma cell line (Akin et al.. 2019). In these cells, Pb-induced a concentration-dependent (0,
0.625, 1.25 (j,M) decrease in E- cadherin expression with no alteration in catenin expression, a substantial
increase in matrix metalloproteinase-9 (MMP9; involved in cell migration) expression, significantly
reduced cell aggregates, and increased cell migration and invasion. Pb exposure also enhanced wound
healing in a functional "scratch" assay.
10.3.9 Inflammation
Inflammation is positively associated with the development and progression of cancer (Zhao et
al.. 2021). Two in vitro cell culture studies investigated markers of inflammation after Pb exposure using
a cancer cell line (Jiang et al.. 2020; Lin et al.. 2015). Lin et al. (2015) investigated Pb nitrate-induced
(0.1 |iM) inflammation using human stomach adenocarcinoma cells. Pb nitrate was found to induce
expression of the proinflammatory gene, interleukin type 8 (IL-8), in a time-dependent manner. Detailed
molecular characterization studies on upstream events indicated transcription factor activator protein 1 to
be a major transcription factor responsible for this activation while another transcription factor, NF-kB,
played only a minor role. Lin et al. (2015) conducted additional experiments using promoter reporter
assay. These experiments indicated that induction of IL-8 is mediated by activation of extracellular
regulator kinase 1/2 and epidermal growth factor receptor upstream of extracellular regulated kinase 1/2
pathway, an important mediator of cytokine secretion. The observation of Pb-induced expression of the
proinflammatory cytokines IL-8 and tumor necrosis factor-a in BEAS-2b human lung cells by Jiang et al.
(2020) also confirms the role of inflammation in Pb exposure. Additional experiments suggest that Pb-
induced oxidative stress may be the initial event triggering this response (Yadav et al.. 2019; Nariva et al..
2018).
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10.3.10 Summary of Mechanistic Pathways and Markers of Carcinogenesis
The toxicological literature provides consistent evidence for the carcinogenic potential of Pb, and
the findings of Pb-induced genotoxic, mutagenic, and epigenetic effects are consistent with the
conclusions drawn in the 2013 Pb ISA. Among the toxicological literature reviewed in the 2013 Pb ISA,
laboratory studies in animals consistently report cancer following chronic Pb exposure for 18 months or
two years to high concentrations, such as 10,000 ppm Pb acetate in diet or 2,600 ppm Pb acetate in
drinking water. Chronic Pb exposure to male and female rodents has consistently induced kidney and
brain carcinogenesis in multiple separate studies, inducing various tumors (i.e., adenocarcinomas,
adenomas, and gliomas). Pb has also been shown to cause mammary gland, prostate, adrenal, and
testicular tumors in animals. Developmental Pb acetate exposure also induced tumors in offspring whose
dams received Pb acetate in drinking water during pregnancy and lactation.
In the absence of any new cancer bioassay studies using animal models, much of the toxicological
evidence evaluated here comes from in vitro studies using several mammalian cell culture systems
(micromolar to millimolar concentrations). These studies provide evidence supporting the Pb-induced
activation of diverse mechanistic pathways that are normally associated with carcinogenesis. The new
studies continue to support that exposure to multiple forms of Pb (i.e., Pb ions such as Pb acetate, Pb
nitrate, or Pb chloride) induces cellular oxidative stress that triggers a set of biological pathways leading
to DNA damage, cytotoxicity, and apoptosis. In several cases, the observed effects were exposure related
and were both dose dependent and duration dependent. The molecular alterations are diverse in nature,
including modified expression of various genes, epigenetic regulatory changes, and activation of upstream
mediators for specific oncogenic pathways. Some of the studies also demonstrated that antioxidant
administration prior to (or simultaneous with) treatment with Pb protected against Pb-induced effects.
Studies of DNA damage and repair after Pb exposure, where oxidative stress seems to be involved,
provide additional evidence in support of these observations. In addition, Pb-induced oxidative stress is
implicated in multiple organ (liver and kidney) toxicity in animals and supports a strong role for this
molecular pathway in Pb-induced toxicity and cancer. Most of the biological pathways implicated in Pb
carcinogenesis reviewed here are part of the IARC-identified 10 key characteristics, further supporting
conclusions derived in 2013 Pb ISA (U.S. EPA. 2013).
10.4 Cancer Incidence and Mortality
Recent studies have included epidemiologic evaluations of the associations between Pb exposure
and both specific cancers (such as breast cancer and lymphoid malignancies), and overall cancer (cancer
of any type). Table 10-1 provides an overview of the study characteristics and results for the
epidemiologic studies that reported effect estimates.
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10.4.1
Epidemiologic Studies of Overall Cancer Incidence
The epidemiologic studies reviewed in the 2013 Pb ISA (U.S. EPA. 2013) found no positive
associations between various biological markers of Pb exposure and overall cancer incidence. The few
epidemiologic studies evaluated were limited by the ecologic or cross-sectional study designs.
Additionally, these studies were limited by the lack of biological measurements of Pb and the lack of
adjustment for potential confounders. There were no recent PECOS-relevant epidemiologic studies of
overall cancer incidence and Pb exposure.
10.4.2 Epidemiologic Studies of Overall Cancer Mortality
The 2013 Pb ISA (U.S. EPA. 2013) reviewed several epidemiologic studies that examined the
associations between blood Pb concentrations and cancer mortality. The findings of these studies were
inconsistent. More specifically, the findings were inconsistent among participants from NHANES III. In
one NHANES III analysis, the cohort of 13,946 (n for cancer mortality = 411) was followed for 12 years
and individuals with BLLs greater than 10 (ig/dL were excluded from the study (mean baseline BLL was
2.58 (ig/dL) (Menke et al.. 2006). There were null associations between blood Pb and cancer mortality
(hazard ratio [HR] of highest tertile [>3.63 |ig/dL| compared with lowest tertile [<1.93 |ig/dL|: 1.10
[95% CI: 0.82, 1.47]). Another NHANES III study, which was restricted to individuals 40 years and older
at the time of blood Pb collection and included 9,757 (N for cancer mortality = 543) individuals with all
BLLs (including those greater than 10 (.ig/dL). reported positive associations between blood Pb and
cancer mortality (Schober et al.. 2006). The RRs were 1.69 (95% CI: 1.14, 2.52) for individuals with
BLLs of at least 10 (ig/dL and 1.44 (95% CI: 1.12, 1.86) for BLLs of 5-9 (ig/dL, compared with
individuals with BLLs less than 5 (ig/dL. Overall, while the epidemiologic studies reviewed in the 2013
Pb ISA (U.S. EPA. 2013) were well-conducted longitudinal studies with control for wide range potential
confounders, the studies were limited by the small number of cancer mortality cases, which reduces
precision of the measures of associations.
There are a limited number of recent epidemiologic studies which examined the associations
between exposure to Pb and overall cancer mortality (Table 10-2). Total mortality is discussed in
Section 9.8 in Other Health Effects. Multiple population-based studies found inconsistent associations
between blood Pb concentrations and overall cancer mortality (Bvun et al.. 2020; Duan et al.. 2020; van
Bemmel et al.. 2011). A subset of NHANES III data (1984-1994) that included adults over the age of 40
(n = 3,223), in study participants with elevated BLLs (>5 (.ig/dL). there were null associations with overall
cancer mortality (HR: 1.083 [95% CI: 0.983, 1.194]), compared with those with lower BLLs (<5 (ig/dL)
(van Bemmel et al.. 2011). Furthermore, the hazard ratio was nearly unchanged when the data were
stratified by an S-aminolevulinic acid dehydratase (ALAD) genetic polymorphism (ALADGG) that may
influence a person's susceptibility to lead poisoning. In another NHANES study (1999-2014), which
included adults over the age of 20 (n = 26,056), blood Pb was positively associated with cancer mortality
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(1.47 [95% CI: 1.22, 1.78]) in the fully adjusted models (Duan et al.. 2020). In the 2007-2015 Korea
National Health and Nutrition Examination Survey (KNHANES), Bvun et al. (2020) reported positive
associations between blood Pb and cancer mortality, among the 7,308 study participants, who were at
least 30 years of age at baseline. Compared with the lowest tertile (blood Pb <1.91 (.ig/dL). the HRs for
cancer mortality in the second (blood Pb between 1.91 and 2.71 (ig/dL) and third (blood Pb >2.71 (ig/dL)
tertile of blood Pb were 3.42 (95% CI: 1.65, 7.08) and 2.27 (95% CI: 1.09, 4.70), respectively. The nature
of the concentration response relationship appears to be non-linear, but the imprecision in the estimates
ultimately limits the ability to make any inferences about the relationship.
In summary, there are a limited number of recent epidemiologic studies that examined the
association between blood Pb concentrations and overall cancer mortality (Table 10-2). These recent
studies used exposure data from population-based national surveys linked to mortality records. The
NHANES studies reported null associations between BLLs and overall cancer mortality. The median and
geometric mean of BLLs among the NHANES studies were all below 10 (ig/dL (median range:
1.49 (ig/dL to 7.5 (ig/dL; geometric mean: 2.26 (ig/dL). In the population-based study in South Korea,
there were positive associations with cancer mortality among participants with BLLs less than 10 (ig/dL.
Because the participants in the population-based South Korean study would likely have had higher past
Pb exposures due to when the leaded gasoline was banned in South Korea, uncertainty exists as to the Pb
exposure level, duration, frequency, and timing associated cancer mortality. Additionally, while these
epidemiologic studies were conducted in well-established cohorts, there is uncertainty in their
interpretation because the overall follow-up period was short (<11 years). These studies also had a small
number of cancer mortality cases, which resulted in reduced precision across the studies. There was a lack
of control for some potential influential confounders such as co-morbidities and body mass index (BMI).l
10.4.3 Epidemiologic Studies of Lung Cancer
The epidemiologic studies reviewed in the 2013 Pb ISA of Pb (U.S. EPA. 2013) exposure and
lung cancer reported no evidence of an association. The studies available for review were conducted in
occupational cohorts and only included male study participants, which limits the generalizability of the
results. A few of the studies did not obtain Pb biomarker exposure levels or only used air sampling
measurements. Furthermore, these studies may be confounded by other workplace exposures and
covariates, such as smoking, that were not considered. There were no recent PECOS-relevant
epidemiologic studies of Pb exposure and lung cancer.
10.4.4 Epidemiologic Studies of Brain Cancer
The 2013 Pb ISA (U.S. EPA. 2013) reviewed a few studies of brain cancer and occupational Pb
exposure. The associations between occupational Pb exposure and brain cancer incidence and mortality
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varied depending on the tumor type or genetic variant. The implications of the results from these studies
were limited because they did not have individual-level biological Pb measurements, relied on self-
reported occupational exposure history, and did not control for potential confounding by other workplace
exposures. There were no recent PECOS-relevant epidemiologic studies of Pb exposure and brain cancer.
10.4.5 Epidemiologic Studies of Breast Cancer
The epidemiologic studies reviewed in the 2013 Pb ISA (U.S. EPA, 2013) of Pb exposure and
breast cancer suggested that women with breast cancer may have higher BLLs than those without breast
cancer. These studies were limited by their study designs, small sample sizes, and with one study, the
method of Pb exposure measurement. There were also some inconsistent results among studies that
compared breast tissue Pb concentrations between breast tumor and control samples.
Since the 2013 Pb ISA, a few epidemiologic studies of Pb exposure in blood and breast cancer
have been published (Table 10-2). Gaudet et al. (2019) examined associations of circulating levels of Pb
with breast cancer risk in three case-control studies nested withing three prospective longitudinal cohorts
in the United States, Italy, and Sweden. Among the three cohorts, there were consistent null associations
between circulating BLLs and breast cancer, both when Pb exposure was evaluated continuously
(RR= 1.00) and when categorized into quintiles (RR range: 0.65-1.10). In a cross-sectional study of
NHANES data, Wei and Zhu (2020) reported increased odds of breast cancer across quartiles of BLLs.
The odds of breast cancer were 2.52 (95% CI: 1.35, 4.73) in the second quartile (0.8 - 1.2 (ig/dL), 2.01
(95% CI: 1.05, 3.84) in the third quartile (1.2-1.8 (ig/dL), and 2.63 (95% CI: 1.36, 5.09) in the highest
quartile £1.8 (ig/dL), compared with the lowest quartile (<0.8 (ig/dL).
Overall, the current epidemiologic studies evaluating the associations between breast cancer and
blood Pb reported inconsistent findings, with a cross-sectional NHANES study finding increasing odds of
breast cancer across blood Pb quartiles, while another study using three longitudinal cohorts did not find
associations between breast cancer and blood Pb. The inconsistency in findings may be related to
differences in study design, biomarkers of exposure as Wei and Zhu (2020) measured Pb in whole blood,
while Gaudet et al. (2019) measured Pb levels in stored erythrocytes, timing of exposure (blood draws
were obtained from 1990-2006 in Gaudet et al. (2019), while Wei and Zhu (2020) used data from 2003-
2012), and range of Pb levels.
10.4.6 Epidemiologic Studies of Other Cancer
The epidemiologic literature reviewed in the 2013 Pb ISA (U.S. EPA. 2013) for associations
between Pb exposures and other specific cancers reported varying associations among occupational
cohorts. Positive associations were observed between occupational exposure to Pb and adenocarcinoma of
the esophagus and stomach cancer, but there were inconsistent associations with occupational Pb
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exposure and rectal cancer and occupational leaded gasoline exposure and stomach cancer. These
occupational cohort studies were limited to the study populations consisting of only men, no personal,
biological, or exposure measurements for Pb, and no control for potential confounding by other
occupational exposures. The current epidemiologic literature examining the associations of Pb exposure
and specific cancer outcomes remains limited. Table 10-2 provides an overview of the current
epidemiologic study details.
A single study evaluated the association between BLLs and urothelial carcinoma in a hospital-
based case-control study in China (Chung et al.. 2017). Study participants were recruited between 2011
and August 2014, resulting in 209 cases matched to 417 controls based on age (range: 26-96 years) and
gender. Cases has slightly higher Pb blood levels (mean: 2.81 (ig/dL) than controls (mean: 2.56 (.ig/dL).
There were increased odds of urothelial carcinoma (OR: 1.66 [95% CI: 1.05, 2.61]) in the highest quartile
(>2.99 (ig/dL) of blood Pb compared with the lowest (<1.76 (ig/dL). There was also increased risk of
urothelial carcinoma in the highest tertile of blood Pb (>2.73 (ig/dL) for both current smokers (OR: 1.76
[95% CI: 0.69, 4.46]) and non-smokers (OR: 1.48 [95% CI: 0.91, 2.39]).
In a hospital-based case-control study in China, Lin et al. (2018) examined the BLLs and
associations with gastrointestinal cancers. There were 167 gastrointestinal cancer cases (70 esophageal,
51 gastric, and 46 colorectal), which were newly diagnosed and previously untreated, and 112 controls
included in the study. The BLLs were slightly higher among cases (median: 6.003 (ig/dL) than controls
(median: 5.384 (ig/dL). The 75th percentile of the BLL (9.09 (ig/dL) of cases was used as a cutoff to
assign study participants as either low (<75th percentile) or high (>75th percentile) blood Pb. There was
an increased odds of 2.32 (95% CI: 1.01, 4.94) of gastrointestinal cancers for those with high BLLs,
compared with those with low BLLs. When stratifying by clinical characteristics among cases with high
BLLs (>9.09 (ig/dL, 75th percentile), there were positive, but imprecise associations due to the small
number of cases (i.e., <20 cases) (see Table 10-2).
Kelly et al. (2013) and Deubler et al. (2020) examined the associations between Pb exposure in
blood erythrocytes and lymphoid malignancies, specifically B-cell non-Hodgkin lymphoma (NHL) and
multiple myeloma (MM), in large prospective cohorts in the United States, Italy, and Sweden. Kelly et al.
(2013) conducted a case-control study nested within two prospective cohorts in Italy (n = 84 cases and
n = 84 controls) and Sweden (n = 186 cases and n = 186 controls). Lymphoma cases were identified
between 2-16 years of follow-up and controls were matched on gender, age, center (Italy or Sweden), and
date of blood collection. With increasing quartiles of pre-diagnostic exposure levels of Pb, Kelly et al.
(2013) reported null associations with B-cell NHL (OR: 0.93 [95% CI: 0.43, 2.02]) for the total study
population (both cohorts), and the null associations remained when stratified by sex [OR for males: 0.74
(95% CI: 0.27, 2.04); OR for females: 0.42 (95% CI: 0.12, 1.47)]. When comparing the highest quartile of
pre-diagnostic exposure levels of Pb to the lowest, there was increased odds of 1.63 (95% CI: 0.45, 5.94)
for MM among the total study population, but this association was imprecise due to the small sample size.
There were insufficient numbers to stratify by males, but for females there was no association between
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MM and the highest quartile of pre-diagnostic exposure levels of Pb (OR:0.74 [95% CI: 0.14, 3.83]).
When further stratified by NHL subtype, there were null associations: diffuse large B-cell lymphoma
(OR: 0.60 [95% CI: 0.26, 1.40]), B-cell chronic lymphatic lymphoma (OR:0.71 [95% CI: 0.32, 1.57]),
MM (OR: 1.04 [95% CI: 0.57, 1.90]), and follicular lymphoma (OR: 1.17 [95% CI: 0.52, 2.63]) per one
unit increase in log-transformed pre-diagnostic exposure levels of Pb. There were null associations for
females for MM (OR: 1.28 [95% CI: 0.53, 1.96]), follicular lymphoma (OR: 1.91 [95% CI: 0.54, 6.78]),
diffuse large B-cell lymphoma (OR:0.29 [95% CI: 0.07, 1.18]), or B-cell chronic lymphatic lymphoma
(OR:0.79 [95% CI: 0.17, 3.60]) per one unit increase in log-transformed pre-diagnostic exposure levels of
Pb. There were null associations between males and MM (OR:0.83, 95% CI: 0.35, 1.96), diffuse large B-
cell lymphoma (OR:0.97 [95% CI: 0.35, 2.64]), B-cell chronic lymphatic lymphoma (OR:0.63 [95% CI:
0.23, 1.74]), or follicular lymphoma (OR:0.80 [95% CI: 0.25, 2.55]) per one unit increase in log-
transformed pre-diagnostic exposure levels of Pb.
Deubler et al. (2020) also conducted a case-control study, but among participants of the Cancer
Prevention Study-II Nutritional Cohort (CPS-IINC) to assess the risk of lymphoid malignancies, B-cell
NHL and MM, with pre-diagnostic erythrocyte Pb levels. There were 375 cases and 750 controls. There
were positive associations with overall lymphoid malignancy (RR: 1.088 [95% CI: 1.009, 1.173] per 1-
SD (1.76 (ig/dL) increase of erythrocyte lead concentrations), all B-cell NHL (RR: 1.093 [95% CI: 1.005,
1.19] per 1-SD increase of erythrocyte lead concentrations), and follicular lymphoma (RR: 1.114 [95%
CI: 1.085, 1.798] per 1-SD increase of erythrocyte lead concentrations), but null associations with diffuse
large B-cell lymphoma, chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), other
B-cell lymphoma, and MM. When stratified by sex, for males, there were positive associations between
overall lymphoid malignancy (RR: 1.131 [95% CI: 1.027, 1.246] per 1-SD (1.81 (ig/dL) increase in
erythrocyte Pb), all B-cell NHL (RR: 1.151 [95% CI: 1.03, 1.286] per 1-SD increase in erythrocyte Pb),
CLL/SLL (RR: 1.274 [95% CI: 1.016, 1.598] per 1-SD increase in erythrocyte Pb), but null associations
with diffuse large B-cell lymphoma, follicular lymphoma, other B-cell lymphoma, and MM. Among
females, there was a positive association with follicular lymphoma (RR: 2.158 [95% CI: 1.07, 4.353] per
1-SD (1.56 (ig/dL) increase in erythrocyte Pb), but null associations with all B-cell NHL, diffuse large B-
cell lymphoma, CLL/SLL, other B-cell lymphoma, and MM.
10.4.7 Summary of Cancer Incidence and Mortality
The epidemiologic studies reviewed in the 2013 Pb ISA (U.S. EPA. 2013) reported inconsistent
findings across cancer endpoints. Among the studies that evaluated Pb exposure and overall cancer
incidence, there were no positive associations with various biological markers of Pb exposure. The
epidemiologic studies of overall cancer incidence were limited by the lack of biological measurements of
Pb and the lack of adjustment for potential confounders. The epidemiologic studies that examined the
associations between Pb concentrations and cancer mortality found inconsistent associations. Although
the studies were well-conducted longitudinal studies with control for a wide range of potential
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confounders, the studies were limited by the small number of cancer mortality cases, which reduces
statistical power to determine the presence of an association. The epidemiologic studies of Pb exposure
and lung cancer reported no evidence of an association. The studies available for review were conducted
in occupational cohorts and only included male study participants, which limits the generalizability of the
results. A few of the studies did not obtain Pb biomarker exposure levels or only used air sampling
measurements. Furthermore, these studies may be confounded by other workplace exposures and
covariates, such as smoking, that were not considered. There were a limited number of studies of brain
cancer and occupational Pb exposure. The associations between occupational Pb exposure and brain
cancer incidence and mortality varied depending on the tumor type or genetic variant. The implications of
the results from these studies were limited because they did not have individual-level biological Pb
measurements, relied on self-reported occupational exposure history, and did not control for potential
confounding by other workplace exposures. The epidemiologic studies reviewed relating to Pb exposure
and breast cancer suggested that women with breast cancer may have higher BLLs than those without
breast cancer. These studies were limited by their study designs, small sample sizes, and, with one study,
the method of Pb exposure measurement. There were also some inconsistent results among studies that
compared breast tissue Pb concentrations between breast tumor and control samples. The epidemiologic
literature reviewed for specific cancers and associations with Pb exposure reported varying associations
among occupational cohorts. Positive associations were observed between occupational exposure to Pb
and adenocarcinoma of the esophagus and stomach cancer, but there were inconsistent associations with
occupational Pb exposure and rectal cancer and occupational exposure to Pb in gasoline and stomach
cancer. These studies were limited to the study populations consisting of only men, no personal biological
or exposure measurements for Pb, and no control for potential confounding by other occupation
exposures.
While there were no recent PECOS-relevant epidemiologic studies of Pb exposure and overall
cancer incidence, lung cancer, and brain cancer, there were a limited number of recent epidemiologic
studies that examined the association between Pb concentrations and overall cancer mortality, breast
cancer mortality, and mortality from other cancers.
The recent PECOS-relevant epidemiologic studies reviewed were inconsistent across cancer
endpoints and support the conclusions from the 2013 Pb ISA (U.S. EPA. 2013). There were inconsistent
findings in large population-based studies examining the relationship between Pb exposure and overall
cancer mortality. While these recent epidemiologic studies were conducted in well-established cohorts,
the overall follow-up period was short (<11 years), there were a small number of cancer mortality cases
resulting in reduced precision across the studies, and there was a lack of control for some confounders
such as co-morbidities. Of note, the cohorts in the recent epidemiologic literature would generally be
expected to have had appreciable past exposures to Pb; however, the extent to which adult BLLs in these
cohorts reflect the higher exposure histories is unknown as to the extent to which these past Pb exposures
(magnitude, duration, frequency) may or may not elicit cancer incidence and/or mortality.
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Recent epidemiologic studies evaluating the associations between breast cancer and blood Pb
reported inconsistent findings, with an NHANES study finding increasing odds of breast cancer in higher
quartiles of blood Pb, while another study using three longitudinal cohorts in Italy, Sweden, and United
States did not find associations between breast cancer and blood Pb. The inconsistency in findings may be
related to difference in study design, biomarker of exposure, timing of exposure, range of Pb levels, and
difference in controlling for potential confounders (age at menarche, pregnancy history, oral contraceptive
use, female hormone use, and menopause status).
The recent epidemiologic literature for site-specific cancers and Pb exposure is limited, reporting
varied associations. The small body of evidence across various site-specific cancer endpoints limits the
ability to judge coherence and consistency across these studies, although the positive associations
reported demonstrate that Pb exposure could result in physiological responses that contribute to some
site-specific cancers. While these studies did control for a wide range of potential confounders, the studies
were limited by small number of cases, relatively short time between exposure and outcome, potential
differences in Pb exposure based on study location, and different biomarkers of exposure.
Overall, there were inconsistent findings in the limited number of epidemiologic studies assessing
associations between Pb exposure and cancer endpoints. While many of these studies utilized large
population-based cohorts, they were limited by the small number of cases, short follow-up time, range of
Pb levels, biomarkers of exposure, information of past Pb exposure, and lack of control of some potential
confounders.
10.5 Biological Plausibility
This section describes the biological pathways that potentially underlie cancer effects resulting
from exposure to Pb. Figure 10-1 graphically depicts these proposed pathways as a continuum of
pathophysiological responses—connected by arrows—that may ultimately lead to the apical cancer events
associated with exposures to Pb at concentrations observed in some epidemiologic studies (e.g., cancer
incidence and mortality). Most studies cited in this subsection are discussed in greater detail earlier in this
Appendix. Note that the structure of the biological plausibility sections and the role of biological
plausibility in contributing to the weight-of-evidence analysis used in the current Pb ISA are discussed in
Section 10.6.
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Altered binding
and transport
proteins, protein
confirmational
changes,
enhanced tissue
accumulation
r
Oxidative stress
Genotoxicity
Pb
and
and
Exposure
mitochondrial
| DNA damage and
dysfunction
repair
L
Epigenetic and
transcriptional
and translation
modifications
Note: The boxes above represent the effects for which there is experimental or epidemiologic evidence related to Pb exposure, and
the arrows indicate a proposed relationship between those effects. Solid arrows denote evidence of essentiality as provided, for
example, by an inhibitor of the pathway or a genetic knockout model used in an experimental study involving Pb exposure. Shading
around multiple boxes is used to denote a grouping of these effects. Arrows may connect individual boxes, groupings of boxes, and
individual boxes within groupings of boxes. Progression of effects is generally depicted from left to right and color-coded (gray,
exposure; green, initial effect; blue, intermediate effect; orange, effect at the population level or a key clinical effect). Here,
population level effects generally reflect results of epidemiologic studies. When there are gaps in the evidence, there are
complementary gaps in the figure and the accompanying text below. The structure of the biological plausibility sections and the role
of biological plausibility in contributing to the weight-of-evidence analysis used in the ISA are discussed in Section 10.6.
Figure 10-1 Potential biological pathways for cancer from exposure to Pb.
The development of cancer is a multistep process that involves the progressive accumulation of
mutations leading to upregulation of oncogenes and loss of function of tumor suppressor genes resulting
in uncontrolled cell growth and invasion of cancer cells within organ tissue. Pb is well-known to cause
cancers in animal models, however, the carcinogenic potential of Pb in humans is not well defined. As
discussed in the 2006 Pb AQCD, the ability of Pb to cause neoplastic transformation in human cells is
limited and is confounded by the fact that some studies utilize Pb chromate. Thus, observed effects may
be related to the effects of chromate as opposed to effects of Pb. Despite this, Pb possesses several
characteristics that were identified by the IARC that are common of human carcinogens (Smith et al..
2016). In addition, Pb is known to act on several pathways that could plausibly lead to cancer
development. The multifaceted pathway outlined in Figure 10-1 connects Pb exposure to cancer incidence
via Pb-protein binding, direct mutagenicity, genotoxicity, inflammation, oxidative stress, and epigenetic
changes. Together, the experimental evidence can provide plausibility for the carcinogenic potential
of Pb.
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The most direct pathway to Pb-induced carcinogenesis would involve mutagenesis in response to
Pb treatment that over time would result in cell transformation. As discussed in the 2006 Pb AQCD, there
is little evidence of the mutagenic potential of Pb (U.S. EPA, 2006). A recent study suggests that Pb can
directly interact with the DNA causing conformational change (Zhang et al., 2014). In this study Pb
caused increased markers of DNA damage although it is not clear if the binding of Pb was responsible for
the observed DNA damage. The potential for Pb to directly induce DNA mutations remains limited and,
as mentioned in the 2006 Pb AQCD, may only occur at very high concentrations.
The strongest data for potential carcinogenesis comes from experiments related to oxidative
stress-induced genotoxicity. The role of oxidative stress in the pathway of cancer is well documented
(Haves et al., 2020). Oxidative stress can result in the damage of proteins, lipids, and DNA. Pb exposure
is well known to cause oxidative stress in several organ systems. Oxidative stress is controlled by a
balance between the formation of reactive oxygen species (ROS) and the actions of antioxidant defenses.
As discussed in the 2013 Pb ISA, multiple in vitro experiments using diverse mammalian cell cultures
exposed to Pb compounds (Pb acetate, Pb chloride, Pb nitrate and divalent Pb ions) for different durations
result in increased production of ROS (U.S. EPA, 2013). This is supported by more recent studies that
consistently report increased ROS levels, decreased antioxidant defenses, and increased markers of
oxidative damage in Pb-exposed cells (see Section 10.3.2). The source of increased generation of ROS in
the context of cancer is not clear but could result as a byproduct of Pb-induced inflammation or Pb
displacement of biologically relevant ions in enzymes, especially those involved with metabolism and
energy production in the mitochondria.
Oxidative stress that damages DNA or impairs DNA repair can lead to mutation and subsequent
cellular transformation. As discussed in the 2013 ISA and in more recent studies, several markers of DNA
damage have been shown to be increased in Pb-exposed cells including 8-OH-deoxy guanine adducts (Liu
et al.. 20IS), alterations in comet DNA content, comet tail movement (Siddarth et al., 2018; El Makawy et
al., 2015; Shakoori and Ahmad, 2013), and DNA double strand breaks (as assessed by H2Ax foci) (Liu et
al., 2018; Shah et al., 2016; Pottier et al„ 2013) as well as diverse genotoxicity measures like micronuclei
formation (Martini et al., 2020; Alimba et al., 2016; Shah et al., 2016; El Makawy et al., 2015) and SCE
(Turkez et al., 2012). Similar increases in bone marrow micronuclei and increased comet tail movement
are seen in animal studies following Pb exposure (Olatunji-Ojo et al„ 2020; Okesola et al., 2019;
Nascimento and Martinez, 2016; El Makawy et al., 2015). In addition, the DNA repair rate has been
shown to be reduced in Pb treated cells (Martinez-Alfaro et al„ 2012). For example, the base excision
repair capacity of the DNA repair enzyme APE-1 is decreased by Pb treatment (Hernandez-Franco et al„
2018). Another study showed reduced DNA repair was associated with decreased glutathione suggesting
that oxidative stress might drive the reduction of DNA repair (Martinez-Alfaro et al., 2012). This data is
further bolstered by an experiment in humans exposed occupationally to Pb that show increased markers
of DNA damage and reduced DNA repair capacity (Jannuzzi and Alpertunga, 2016). In many
experimental cases, treatment with antioxidant compounds can protect against DNA damage (Okesola et
al., 2019; Siddarth et al„ 2018; El Makawy et al„ 2015) suggesting that oxidative stress is necessary for
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Pb-induced genotoxicity. This data supports a solid line in Figure 10-1 from oxidative stress to
genotoxicity.
Pb can also plausibly promote cancer development through induction of inflammation.
Inflammation is a hallmark of a pro-cancer environment. Induction of inflammation could be direct effect
by increased secretion of pro inflammatory markers. In addition, inflammation can result from cell
damage caused by oxidative stress. The 2013 Pb ISA and 2006 Pb AQCD discuss evidence that Pb
treatment can trigger the production of inflammatory mediators in vitro as well as in many organ systems
(U.S. EPA, 2013, 2006). More recent in vitro evidence supports these findings in the context of cancer
cell lines (Jiang et al., 2020; Lin et al., 2015). Many natural compounds that demonstrate anticancer
activity in vitro possess both anti-inflammatory and antioxidant capacity suggesting that inflammation
could be playing a role in the development of cancer.
Excessive DNA damage, as a result of inflammation and oxidative stress, can activate cell death
pathways. Cancer can arise when mutated cells suppress cell death pathways. Alternatively, cell death
often triggers compensatory expansion of surrounding cells. With chronic injury, a constant repair process
activation can trigger hyperplastic growth and degradation of extracellular matrix that can promote
cellular transformation and tumor invasiveness. While there is evidence that Pb treatment in vitro can lead
to cell death (see Section 10.3.5), there is no evidence to suggest that Pb can cause resistance to cell
death. However, there are some indications that Pb can stimulate cellular regrowth that over time could
potentially promote cellular transformation. Wang et al. (2013) showed that Pb treatment of CL3 cells
resulted in increased cell cycle progression. Another recent study showed that Pb treatment can lead to
increased MMP expression resulting in greater cell migration in a wound healing assay (Akin et al.,
2019). Together, there is strong evidence that Pb can cause cell death but the role of Pb in the
development of apoptosis resistance or uncontrolled cell growth remains speculative.
Over time, accumulation of mutations that promote tumor growth and blunt anti-tumor defenses
can lead to cell transformation and increased cancer incidence. In vitro assays can measure transformation
as an increase in morphologically distinct cells (i.e., a foci). As discussed in the 2013 ISA, data from
cellular transformation assays have shown that Pb acts as a promoter of cellular transformation in animal
cells in vitro. In support of this, a recent study showed that Pb pretreatment of Balb/c-3T3 cells prior to
transformation with n-methyl-n-nitrosoguanidine and 12-O-tetradecanoylphorbol-13-acetate resulted in
increased foci formation suggesting that Pb can help to promote transformation (Hernandez-Franco et al.,
2018).
Changes in regulation of gene expression through epigenetic mechanisms represent another
plausible pathway by which Pb can promote tumor formation. The 2013 ISA provided limited evidence
from human studies that tibia Pb levels could be inversely related to global methylation markers (U.S.
EPA, 2013). A new study of infant blood spots showed a general decrease in methylation at 33 CpG sites
with increasing BLLs (Laurino et al., 2020). Interestingly, pathway enrichment analysis suggested that
differentially methylated sites corresponded to cell morphogenesis and cell adhesion. This suggests that
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changes in epigenetics regulation could play a role in changes in cell adhesion which could be important
in the context of tumor invasiveness and metastasis. Increased methylation was also seen in the promoter
regions of several DNA repair genes following Pb exposure which correlated with decreased repair
protein levels (Liu et al.. 2018). Alterations of methyltransferases levels following Pb exposure in vitro
has also been reported and correlate with increased expression of an oncogene (Ghosh et al.. 2018).
Insight into the mechanism of epigenetic regulation by Pb was provided by Rabbani-Chadcgani et al.
(2011) who showed that Pb nitrate bound to rat liver chromatin. When analyzed separately, Pb bound
histones with higher affinity than to DNA (Rabbani-Chadcgani et al.. 2011). The affinity of Pb nitrate was
greater than Ni nitrate in these studies. Though the biological effects of histone binding were not
investigated, it is possible that binding of Pb to histone chromatin or histones could result in epigenetics
changes through alterations in accessibility of DNA or histones to modifying enzymes. Overall, there is
evidence that Pb can affect epigenetic markers of genes that could affect cancer development.
Pb has been shown to replace biologically relevant ions within cellular proteins which can cause
confirmational changes that can impair target protein function. Thus, direct binding of Pb to cellular
proteins could form another plausible pathway to promote tumor formation. For example, Pb can compete
with Zn in Zn finger domains which are present in several transcription factors (Ghering et al.. 2005;
Huang et al.. 2004; Hanas et al.. 1999). Pb-induced conformation changes in cellular proteins could have
widespread effects on cellular functions and could theoretically promote cellular transformation. The
potential of Pb to directly bind and alter cellular protein function represents another pathway by which Pb
exposure could result in cell transformation and tumorigenesis.
Together, mechanistic toxicological data provides several possible pathways through which Pb
exposure can result in the tumorigenesis that is seen in animal studies and that is reported in some
epidemiologic studies. The evidence is strongest for a pathway that involves Pb-induced inflammation
and oxidative stress which causes subsequent DNA damage that, in conjunction with suppression of
proper DNA repair mechanisms, can lead to mutations that could result in neoplastic transformation.
There is also increasing evidence for the plausibility of epigenetic changes caused by Pb to promote
tumorigenesis. Given the widespread impacts of Pb on cellular proteins there are other plausible pathways
for tumor formation including direct mutagenesis and chronic tissue damage with subsequent cell cycle
disruption, although the evidence for these pathways is more limited.
10.6 Summary and Causality Determination
The 2013 Pb ISA concluded that there was a "likely to be a causal relationship" between Pb
exposure and cancer (U.S. EPA. 2013). This causality determination was made on the basis that the
toxicological literature provides consistent evidence of the carcinogenic potential of Pb and possible
contributing modes of action, including genotoxic, mutagenic, and epigenetic effects. The toxicological
literature provided strong evidence for cancer following long-term exposure (i.e., 18 months or 2 years) to
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high concentrations of Pb (>2,6000 ppm) in drinking water. The consistent evidence indicating Pb-
induced carcinogenicity in animal models was substantiated by findings from multiple high-quality
toxicological studies in animal and in vitro models from different laboratories. Carcinogenicity in animal
toxicology studies with relevant routes of Pb exposure has been reported in the kidneys, testes, brain,
adrenals, prostate, pituitary, and mammary gland, albeit at high doses of Pb. Epidemiologic studies of
cancer incidence and mortality reported inconsistent results; one strong epidemiologic study demonstrated
an association between blood Pb and increased cancer mortality (Schober et al.. 2006). but the other
studies reported weak or no associations (Khalil et al.. 2009; Weisskopf et al.. 2009; Menke et al.. 2006).
Although there are no recent PECOS-relevant animal toxicological studies evaluating the
relationship between Pb exposure and cancer endpoints, the animal studies available in previous reviews
continue to provide strong support for the carcinogenic potential of high Pb exposures (chronic
10,000 ppm Pb acetate diet or 2,600 ppm drinking water Pb acetate) (Tokar et al.. 2010; Waalkes et al..
1995; Kasprzak et al.. 1985; Koller et al.. 1985; Azar et al.. 1973; Van Esch and Kroes. 1969). Recent in
vitro studies report Pb activation of pathways that are relevant and frequently reported to be involved in
cancer development and/or progression, particularly pathways mediated by oxidative stress, genotoxicity,
and inflammation. Other mechanistic pathways that may be involved in Pb-induced carcinogenesis
include cell cycle regulatory genes, epigenetics, apoptosis, and necrosis with predictive regenerative
proliferation. Additionally, new areas of research involving MMPs and metallothionines have emerged
and provide evidence of other potential mechanistic pathways through which Pb exposure could
contribute to cancer. This recent evidence has added to our understanding of how Pb exposures may
activate the mechanistic pathways that can result in cancer.
Recent epidemiologic studies that examined the associations between Pb exposure and overall
cancer mortality reported inconsistent results, similar to the epidemiologic studies evaluated in the 2013
Pb ISA (U.S. EPA. 2013). The recent studies of overall cancer mortality used exposure data from
population-based national surveys linked to mortality records. While there were positive associations
between blood Pb and overall cancer mortality in large population survey studies in the United States and
Korea (Bvun et al.. 2020; Duan et al.. 2020). there were null associations in another NHANES study (van
Bemmel et al.. 2011). These epidemiologic studies were conducted in large, well-established population-
based cohorts, but there are still limitations. These include short overall follow-up periods (<11 years), a
small number of cancer mortality cases resulting in reduced precision across the studies, and a lack of
control of some confounders such as co-morbidities. There were a limited number of recent
epidemiologic studies evaluating the associations between Pb exposure and site-specific cancers. The
studies reviewed reported inconsistent findings. While several of the studies were well-conducted in large
cohorts, there remain uncertainties in the biomarkers of exposure (blood versus erythrocytes), timing of
exposure, years of follow-up, range of Pb levels, exposure circumstances (magnitude, duration, timing,
and frequency) and differences in controlling for potential confounders (co-morbidities, BMI, age at
menarche, pregnancy history, oral contraceptive use, female hormone use, and menopause status).
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In summary, the collective body of evidence is sufficient to conclude that there is likely to be
a causal relationship between Pb exposure and cancer. The key evidence for this causal determination
is in Table 10-1. There continues to be strong evidence from in vivo toxicological studies and from
studies of mechanistic pathways indicating the carcinogenic potential of Pb exposure, including
inflammation; oxidative stress; and genotoxic, mutagenic, and epigenetic effects. Recent mechanistic
research further identifies biologically plausible molecular pathways through which Pb could contribute
to the initiation and/or progression of cancer, and these pathways are consistent with the IARC 10 key
characteristics of carcinogenic mechanistic pathways (Smith et al.. 2016). Several of these pathways are
consistent with the reported mechanistic pathways associated with Pb carcinogenicity reported in the
2013 Pb ISA. Recent epidemiologic studies provide inconsistent evidence of associations between Pb
exposure and cancer incidence and/or mortality, for either overall or site-specific cancer. More
specifically, the small body of epidemiologic evidence across various site-specific cancer endpoints limits
the ability to judge coherence and consistency across these studies, although the positive associations
observed in a small number of studies at relevant BLLs demonstrate that Pb exposure could result in
physiological responses that contribute to urothelial carcinoma, gastrointestinal cancer, non-Hodgkin's
lymphoma, and multiple myeloma. Despite uncertainty due to inconsistent findings across epidemiologic
studies, animal toxicology studies and in vitro mechanistic studies provide strong evidence for the
carcinogenic potential of Pb exposures.
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Table 10-1 Summary of evidence for a likely to be causal relationship between Pb exposure and cancer
RatiDet5m°naCtionaality KeV Evidence' Key References' Pb Biomarker Levels Associated with
Consistent evidence from Consistent findings across multiple Azar et al. (1973)
multiple animal studies with
chronic Pb exposure
toxicology studies using 18-mo or2-yr
cancer bioassays in rats wherein
rodents are fed chow or received
drinking water enriched with Pb
acetate and show tumor development.
Kasprzak et al. (1985)
Kolleret al. (1985)
Van Esch and Kroes (1969)
See Section 10.3.2
Chronic 10,000 ppm Pb acetate diet or
2,600 ppm drinking water Pb acetate,
no blood Pb measurement available.
Gestational and lactational Pb
exposure induced carcinogenicity in
adult offspring.
Waalkes et al. (1995)
Tokaret al. (2010)
See Section 10.3.2
500, 750, and 1,000 ppm Pb in drinking
water, no blood Pb measurement
available.
Most evidence clearly
supports biological
plausibility
Consistent toxicological evidence for
mutagenicity, carcinogenicity, and
genotoxicity of Pb reported by multiple
laboratories in humans, animals and in
vitro models using multiple assays
(micronuclei, SCE, comet).
See subsections in Section 10.3
Toxicology evidence of DNA and cellular
damage:
Tapisso et al. (2009)
Alqhazal et al. (2008)
Gastaldo et al. (2007)
Xu et al. (2008)
Nava-Hernandez et al. (2009)
Yediou et al. (2010)
Xu et al. (2006)
Kermani et al. (2008)
Epidemiology evidence of DNA and cellular
damage:
Wiwanitkit et al. (2008)
Duvdu et al. (2005)
Khan etal. (2010)
Olewihska et al. (2010)
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Rationale for Causality
Determination3
Key Evidence"
Key Referencesb
Pb Biomarker Levels Associated with
Effects0
Some evidence for epigenetic
changes. Bone Pb levels were
inversely associated with LINE-1
methylation in a study of adult men
Shaik and Jamil (2009)
Wright etal. (2010)
Patel (2013)
Study showed inverse association
between maternal postpartum bone Pb
levels and Alu and LINE-1 methylation Pilsner etal. (2009)
in cord blood.
Occupational battery workers had
ALAD hypermethylation compared with
controls; cell culture study of high dose Li et al. (2011)
Pb exposure caused ALAD
hypermethylation.
Toxicological evidence of
clastogenic (SCE,
micronucleus formation,
chromosomal aberrations),
mutagenic, and genotoxic
effects with Pb chromate
Wise etal. (2010)
Grlickova-Duzevik et al. (2006)
Saverv et al. (2007)
Camvre et al. (2007)
Stackpole et al. (2007)
Li Chen et al. (2009)
Wise et al. (2009)
Wise etal. (2011)
Some toxicological studies employ Pb
chromate when investigating the
clastogenic, mutagenic, and genotoxic
effects of Pb. The effect of the
chromate ion in contributing to these
effects cannot be ruled out.
Holmes et al. (2006a)
Wise et al. (2006a)
Holmes et al. (2006b)
Wise et al. (2006b)
Yipptai r?nrm
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Rationale for Causality
Determination3
Key Evidence"
Key Referencesb
Pb Biomarker Levels Associated with
Effects0
Epidemiologic evidence is
limited and inconsistent
Epidemiologic studies of overall cancer
mortality have inconsistent findings.
These are high-quality, longitudinal
studies and control for potential
confounders, such as age, smoking,
and education. The follow-up period
was short (<11 yr). There is uncertainty
related to exposure patterns resulting
in likely higher past Pb exposure.
There was the lack of control of
potential important confounders such
as co-morbidities.
Overall Cancer Mortality: See Section 10.4.2
In the mortality studies, the majority of
the study participants' BLLs were <10 |jg/
dL (NHANES medians ranged from 1.49
to 7.5 |jg/dL and KNHANES geometric
mean was 2.26 |jg/dL).
Epidemiologic studies of specific
cancer sites were limited. Many of the
epidemiologic studies examining
specific cancer sites were case-control
studies and not all included potentially
important confounders, such as
smoking and co-morbidities. There is
uncertainty related to exposure
patterns resulting in likely higher past
Pb exposure and impact of difference
biomarkers (blood vs. stored
erythrocytes).
Specific Cancer:
Breast Cancer: See Section 10.4.5
Other Cancer: See Section 10.4.6
In studies of breast cancer, the majority
of the study participants' BLLs were
<10 ug/dL (medians ranged from 1.15-
8.78 pg/dL).
In studies of other cancer, the majority of
the study participants' BLLs were
<10 pg/dL (medians ranged from 3.05-
9.191 pg/dL and means ranged from
2.56-2.81 pg/dL).
aBased on aspects considered in judgments of causality and weight of evidence in causal framework in Table I and Table II of the Preamble to the ISAs (U.S. EPA. 2015).
bDescribes the key evidence and references, supporting or contradicting, contributing most heavily to causality determination and, where applicable, to uncertainties or
inconsistencies. References to earlier sections indicate where the full body of evidence is described.
°Describes the Pb biomarker levels at which the evidence is substantiated.
ALAD = 6-aminolevulinic acid dehydratase; BLL = blood lead level; KNHANES = Korea National Health and Nutrition Examination Survey; LINE = long interspersed nuclear
elements; mo = month; NHANES = National Health and Nutrition Examination Survey; Pb = lead; SCE = sister chromatid exchange; yr = year.
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10.7 Evidence Inventories - Data Tables to Summarize Study Details
Table 10-2 Epidemiologic studies of exposure to Pb and cancer effects
Reference and
Study Design Study PoPulatlon
Exposure Assessment
Outcome
Confounders
Effect Estimates and 95%
Clsa
Overall Cancer Mortality
Menke et al.
{2006)t
U.S.
NHANES III (1988-
1994), mortality
follow-up in 2001
(12 yr follow-up)
Cohort
NHANES III
n = 13,946, >20 yr
Blood
Blood was measured by
GFAAS with Zeeman
correction
Mean: 2.58 |jg/dL
Blood Pb Tertiles:
T1: <1.93 |jg/dL
T2: 1.94-3.62 pg/dL
T3: >3.63 pg/dL
Age of Measurement
Mean 44.4 yr
Overall cancer mortality
Cause of death was
determined by the underlying
cause of death listed on
death certificates. ICD-9
codes (codes 140 to 239)
were used for deaths
between 1988 and 1998 and
ICD-10 codes (C00-C97 and
D00-D048) were used for
deaths during 1999 and
2000.
Age at Outcome: Age at
death
Cox proportional
hazard regression
analysis adjusted
age, race/ethnicity,
sex, urban residence,
cigarette smoking,
alcohol consumption,
education, physical
activity, household
income, menopausal
status, BMI, CRP,
total cholesterol,
diabetes mellitus,
hypertension, GFR
category
HR:
T1
T2
T3
Reference
0.72 (0.46, 1.12)
1.10 (0.82, 1.47)
Schober et al.
(2006)1-
U.S.
NHANES III (1988-
1994), mortality
follow-up in 2006
-8.55 yr of follow-
up
NHANES III
n = 9,686, >40 yr of
age
Blood
Blood was measured by
GFAAS with Zeeman
correction
Age of Measurement:
>40 yr
Blood Pb Tertiles:
Overall cancer mortality
Deaths due to malignant
neoplasm (ICD-10 codes
C00-C97)
Age at Outcome: Age at
death
Cox proportional
hazard regression
analysis adjusted for
sex, age,
race/ethnicity,
smoking, education
level
Relative Risk (RR):
T1: Reference
T2: 1.44 (1.12, 1.86)
T3: 1.69 (1.14, 2.52)
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Reference and
Study Design
Study Population
Exposure Assessment
Outcome
Confounders
Effect Estimates and 95%
Clsa
Cohort
T1 < 5 (median 2.6 |jg/dL)
T2 5-9 (median 6.3 |jg/dL)
T3 > 10 (median
11.8 |jg/dL)
van Bemmel et al.
(2011)
U.S.
NHANES III (1984-
1994), mortality
follow-up in 2007
(-7.8 yr of follow-up
for low blood Pb
and -7.5 yr of
follow-up for high
blood Pb)
Cohort
NHANES
n: 3,349 (BLL <5 pg/dL
n: 2,532; BLL >5 ug/dL
n: 817)
NHANES III (1984-
1994) general
population restricted to
the participants who
were successfully
genotyped, excluding
those under the age of
40; those with no
baseline blood Pb
measurements;
missing data on ALAD
genotype, education,
and date of study entry
Blood
Blood was measured by
GFAAS
Age at Measurement:
40+
Median for BLL <5 pg/dL:
2.6 pg/dL
Median for BLL >5 pg/dL:
7.5 pg/dL
Max: 52.9 pg/dL
Overall cancer mortality
Mortality from malignant
neoplasm (ICD-10 codes
C00-C97)
Age at Outcome:
Age at death was defined as
the time to event
Cox proportional
hazard regression
models were adjusted
for age, education,
sex, smoking status,
race/ethnicity, ALAD
genotype
HR: 1.08 (0.98, 1.19) for BLL
>5 pg/dL, compared to
<5 pg/dL
HR for ALADGG: 1.08 (0.99,
1.19) for BLL >5 pg/dL,
compared to <5 pg/dL
Duan et al. (2020)
U.S.
1999-2014,
mortality follow-up
in 2015 (-7.1 yr of
follow-up)
Cohort
NHANES
n: 26,056
NHANES participants
aged 20 yr or older,
not pregnant, or
missing covariate data
Blood
Blood was measured by
multielement atomic
absorption spectrometer
with a Zeeman background
correction (NHANES 1999-
2002) or ICP-MS (after
2003)
Age at Measurement:
average age: 45.9 yr
Medianb: 1.49 pg/dL
75thb: 2.31 pg/dL
Overall cancer mortality
Death certificates were used
to determine the source and
cause of death, specifically
cancer-specific mortality
(codes C00-C97)
Age at Outcome:
Age at death
Poisson regression
models estimated the
RR and adjusted for
sex, age, age
squared, and ethnicity
(Model 1); plus
education, PIR,
cotinine category,
BMI, and physical
activity (Model 2);
plus hypertension and
diabetes (Model 3)
RR per one unit increase in
blood Pb
Model
1:
1
65
(1
38,
1
97)
Model
2:
1
47
(1
22,
1
77)
Model
3:
1
47
(1
22,
1
78)
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Reference and
Study Design
Study Population
Exposure Assessment
Outcome
Confounders
Effect Estimates and 95%
Clsa
Bvun et al. (2020)
Korea
2007-2015,
mortality follow-up
in 2018 (between 3
and 11 yr of follow-
up)
Cohort
KNHANES
n: 7,308
Individuals with a BLL
less than 10 |jg/dL,
who were aged 30 yr
and over at the
baseline examination,
and who were not
diagnosed with cancer
or ischemic heart
disease
Blood
Blood was measured by
GFAAS with Zeeman
background correction
Age at Measurement:
30+ yr
Geometric mean: 2.26
(±1.52) |jg/dL
Blood Pb tertiles:
T1: <1.91 |jg/dL
T2: 1.91-2.71 pg/dL
T3: >2.71 pg/dL
Overall cancer mortality
Deaths identified from all
non-accidental causes (the
International Classification of
Disease tenth revision: ICD-
10, A00-R99) and cancer
(ICD-10, C00-97).
Age at Outcome:
Age at death
Cox proportional
hazard models: Initial
models (Model 1)
were adjusted only for
age and sex.
Subsequent models
(Model 2) were
additionally adjusted
for household
income, education,
occupation, smoking
status, drinking
frequency, BMI, and
physical activity. Final
models (Model 3)
were further adjusted
for intake of high-
lead-containing food
intake (grains,
vegetables, and
seafood).
HR
Model 1:
Reference
3.19 (1.47, 6.91)
2.41 (1.17, 4.96)
Model 2:
Reference
3.46 (1.65, 7.26)
2.26 (1.09, 4.69)
Model 3:
Reference
3.42 (1.65, 7.08)
2.27 (1.09, 4.70)
Breast Cancer
Gaudetetal. (2019)
United States,
Sweden
Italy,
CPS-II n: 21,956;
EPIC-ltaly n: 32,578;
NSHDS n: 40,256
U.S. CPS-II: 1998-
2001; EPIC-ltaly:
1993-1998;
NSHDS: 1990-
2006
Cohort
Blood (erythrocytes)
Blood was measured by
ICP-MS
Age at measurement:
Median age (range): CPS-
II: 68 (47-85); EPIC-ltaly:
52 (35-70); NSHDS: 50
(30-61)
Median0: CPS-II:
2.53 pg/dL; EPIC-ltaly:
8.78 pg/dL; NSHDS:
3.897 pg/dL
Breast cancer
CPS-II: Cancer incident to
blood draw diagnosed
through June 30, 2011 were
self-reported on follow-up
questionnaires and
subsequently verified by
obtaining medical records or
through linkage with state
registries when complete
medical records could not be
obtained. Deaths were
obtained through linkage of
the cohort with the National
Death Index.
Logistic regression
models estimated the
relative risk (RR);
adjusted for race,
blood draw date and
age for CPS-II; and
age, year of blood
collection,
menopausal status
and Italian study
center for EPIC-ltaly
and NSHDS
CPS-II:
RR per each unit increase in
blood Pb (continuous): 1.00
(0.99, 1.00)
Quintile RR:
Q1
Reference
Q2
00
o
1.49)
Q3
1.07 (0.79,
1.45)
Q4
0.94 (0.69,
1.28)
Q5
0.94 (0.69,
1.28)
EPIC-ltaly:
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Reference and
Study Design
Study Population
Exposure Assessment
Outcome
Confounders
Effect Estimates and 95%
Clsa
Breast cancer cases
included 816 cases
from CPS-II, 294 from
EPIC-ltaly and 325
from NSHDS. Each
case was paired with
one control. Eligible
controls were selected
among those who
were alive and cancer-
free at the time of the
case's diagnosis and
matched on race
(CPS-II), birthdate
(within 6 mo in CPS-II
and within 2.5 yr in
EPIC-ltaly and
NSHDS), menopausal
status (NSHDS, EPIC-
ltaly), study center
(EPIC-ltaly) and blood
draw date (within 6 mo
in CPS-II and within
the same year in
EPIC-ltaly and
NSHDS).
75thc: CPS-II: 3.442 pg/dL;
EPIC-ltaly: 11.21 pg/dL;
NSHDS: 5.288 pg/dL
Blood Pb Quintiles0:
CPS-II:
Q1
0-1.68 pg/dL
Q2
1.69-2.28 pg/dL
Q3
2.29-2.88 pg/dL
Q4
2.89-3.76 pg/dL
Q5
3.77-14.84 pg/dL
EPIC-ltaly:
Q1
2.40-6.35 pg/dL
CM
a
6.36-7.99 pg/dL
Q3
8.00-9.99 pg/dL
Q4
10.00-12.50 pg/dL
Q5
12.51-39.18 pg/dL
NSHDS:
Q1
0.80-2.64 pg/dL
Q2
2.65-3.57 pg/dL
Q3
3.58-4.54 pg/dL
Q4
4.55-5.53 pg/dL
Q5
5.54-22.37 pg/dL
EPIC-ltaly: Newly identified
cancer cases were identified
through automated linkages
to cancer and mortality
registries, municipal
population offices and
hospital discharge systems.
In Naples, follow-up
information was collected
through periodic personal
contact.
NSHDS: Newly identified
cancer cases were identified
through linkage with the
Swedish Cancer Registry and
the local Northern Sweden
Cancer Registry.
Age at Outcome: Age at
diagnosis
RR per each unit increase in
blood Pb (continuous): 1.00
(0.99, 1.00)
Quintile RR:
Q1
Q2
Q3
Q4
Q5
Reference
0.94 (0.57, 1.56)
0.96 (0.57, 1.61)
0.74 (0.43, 1.25)
0.77 (0.45, 1.33)
NSDHS:
RR per each unit increase in
blood Pb: 1.00 (0.99, 1.01)
Quintile RR:
Q1
Q2
Q3
Q4
Q5
Reference
1.09 (0.68, 1.76)
0.99 (0.61, 1.60)
0.65 (0.39, 1.08)
1.06 (0.66, 1.71)
10-31
-------
Reference and
Study Design
Study Population
Exposure Assessment
Outcome
Confounders
Effect Estimates and 95%
Clsa
Wei and Zhu (2020) NHANES
n: 9,260
U.S.
2003-2012 Female participants
20 yr of age or older
Cross-sectional
Blood
Blood was measured by
ICP-MS
Age at measurement:
20+ yr
Geometric
mean:1.09 |jg/dL
Median: 1.15 |jg/dL
Max: 25 |jg/dL
Blood Pb Quartiles:
Q1
Q2
Q3
Q4: >1.8 |jg/dL
<0.8 |jg/dL
0.8 to <1.2 |jg/dL
1.2 to <1.8 |jg/dL
Breast cancer
Self-reported cancer
diagnosis was obtained from
the medical conditions
questionnaires. Participants
were being asked a question
"Have you ever been told by
a doctor or other health
professional that you had
cancer or a malignancy of
any kind?'. Participants who
answered "yes" were
subsequently asked "What
kind of cancer was it? Only
women who reported "no
cancer" diagnosis or a
"breast cancer" diagnosis
were included in our study
population. The study
population was categorized
into with breast cancer and
without breast cancer in the
analytical models.
Age at Outcome:
age at diagnosis
Logistic regression
models were adjusted
for age, race/ethnicity,
poverty status,
education, BMI,
physical activity, age
at menarche,
pregnancy history,
oral contraceptive
use, female hormone
use, cigarette
smoking, and alcohol
consumption
OR
Q1
Q2
Q3
Q4
Reference
2.52 (1.35, 4.73)
2.01 (1.05,
2.63 (1.36,
3.84)
5.09)
10-32
-------
Reference and
Study Design
Study Population
Exposure Assessment
Outcome
Confounders
Effect Estimates and 95%
Clsa
Other Cancers
Chung et al. (2017)
Taichung
Taiwan
June 2011-August
2014
Case-control
n: 209 patients with
UC and 417 control
patients
UC patients aged 26-
96 yr, whose
diagnoses were
evaluated by a
pathologist. Matched
control participants
with cases according
to gender and age
(±3 yr) from patients
undergoing adult
health examinations.
Blood
Blood was measured by
ICP-MS
Age at Measurement:
Mean age for cases:
67.18 ± 10.79; mean age
for controls: 66.20 ± 10.06
Mean for cases: 2.81 |jg/dL
Mean for controls:
2.56 |jg/dL
Blood Pb Quartiles:
Q1: <1.76 |jg/dL
Q2: 1.76-2.31 pg/dL
Q3: 2.31-2.99 pg/dL
Q4: >2.99 pg/dL
Other cancers: Urothelial
carcinoma
Patients with UC comprised
outpatients or inpatients
among men and women
aged 30-90 yr old; UC cases
were limited to patients with
urinary tract urothelial
carcinoma, whose diagnoses
were evaluated by a
pathologist.
Age at Outcome:
Mean age for cases:
67.18 ± 10.79; mean age for
controls: 66.20 ± 10.06
Logistic regression
models were adjusted
for age, gender,
smoking
OR
Q1
Q2
Q3
Q4
Reference
0.68 (0.40, 1.15)
1.05 (0.64, 1.70)
1.66 (1.05, 2.61)
OR for smokers:
T1
T2
T3
Reference
1.71 (0.63, 4.60)
1.76 (0.69, 4.46)
OR for non-smokers:
T1
T2
T3
Reference
0.72 (0.43, 1.22)
1.40 (0.91, 2.39)
Blood Pb Tertiles for
Smoking Status:
T1: <1.98 pg/dL
T2: 1.98-2.73 pg/dL
T3: >2.73 pg/dL
10-33
-------
Reference and
Study Design
Study Population
Exposure Assessment
Outcome
Confounders
Effect Estimates and 95%
Clsa
Lin etal. (2018)
Chaoshan,
China
June-December
2014
Case-control
n: 180 cases and 120
controls
Participants recruited
were native inhabitants
living in the Chaoshan
area (including the
cities of Shantou,
Chaozhou, and
Jieyang, and other
neighboring areas).
Cases and controls
had no distinction
between geographic or
cultural groups since
they were the native
aborigines in
Chaoshan.
Blood
Blood was measured by
GFAAS
Age at Measurement:
Cases mean age: 59.065;
Controls mean age: 47.09
Median0 for cases:
6.003 |jg/dL
Median0 for controls:
5.384 |jg/dL
75th° for Cases:
9.086 |jg/dL
75thc for Controls:
7.627 |jg/dL
Blood Pb Quartiles:
Q1: <25th percentile
Q2: 25th-50th percentile
Q3: 50th-75th percentile
Q4: >75th percentile
Other cancers:
Gastrointestinal cancers
All cases were newly
diagnosed and previously
untreated. Clinical
characteristics, including
basic medical data, were
obtained from medical
records. Controls (n = 112)
were recruited and found no
disease in the subsequent B-
ultrasound, imaging
examination, and
hematological examination.
Age at Outcome:
Cases mean age: 59.065;
Controls mean age: 47.09
Logistic regression
models were adjusted
for gender, age,
tobacco smoking, and
alcohol drinking
OR
Q1
Q2
Q3
Q4
Reference
0.683 (0.328, 1.423)
0.865 (0.410, 1.822)
2.32 (1.01, 4.94)
OR for Clinical Stages:
I: Reference
II: 2.099 (0.451, 9.759)
III: 1.458 (0.419, 5.074)
IV: 0.613 (0.210, 1.789)
OR for T Classification:
T1+T2: Reference
T3+T4: 4.752 (1.299, 17.389)
OR for N Classification:
NO: Reference
N1+N2+N3: 3.000 (0.822,
10.945)
OR for M Classification:
M0: Reference
M1: 4.546 (0.757, 27.317)
10-34
-------
Reference and
Study Design
Study Population
Exposure Assessment
Outcome
Confounders
Effect Estimates and 95%
Clsa
Kelly etal. (2013)
Italy and Sweden
Italy: 1993-1998;
Sweden: 1990-
2006
Case-control
E n vi roGe n o M a rke rs
Study
n: Italy: n = 47,749;
Sweden: n = 95,000
The
E n vi roGe n o M a rke rs
study is based on
participants from two
existing prospective
cohort studies: EPIC-
Italy and the NSHDS.
EPIC-ltaly: 47,749
volunteers aged 35-
70 yr were enrolled in
five participating
centers across Italy.
The NSHDS includes
participants from the
Vasterbotten. A total of
95,000 healthy
individuals aged 40-60
were invited for
inclusion in the project
between 1990 and
2006.
Blood (erythrocytes)
Blood was measured by
ICP-MS
Age at Measurement:
Mean age for cases:
53.08 yr
Mean age for controls:
53.09 yr
Median0: 9.191 |jg/dL in
Italy
Median0: 4.499 |jg/dL in
Sweden
Erythrocyte Pb Quartiles0
for B-cell NHL:
Q1
Q2
Q3
Q4
1.5423-3.9286 pg/dL
3.9504-5.8763 pg/dL
5.8832-8.7218 pg/dL
8.7531-40.0843 pg/dL
Erythrocyte Pb Quartiles0
for B-cell NHL for Males:
Q1
Q2
Q3
Q4
Other cancers: B-cell non-
Hodgkin's lymphoma and
multiple myeloma
Lymphoma cases that
occurred within the two
cohorts between 2 and 16 yr
of follow up were identified.
Lymphoma cases were
classified into subtypes
according to the SEER
ICD-0-3 morphology codes.
All eligible B-cell NHL cases,
including multiple myeloma
were included.
Age at Outcome:
mean age for cases: 53.08 yr
mean age for controls:
53.09 yr
Conditional logistic
regression models
were adjusted for sex,
age, center, batch
and sample date
1.5423-4.4989 pg/dL
4.5444-6.1498 pg/dL
6.1904-10.0201 pg/dL
10.0528-
37.8943 pg/dL
Erythrocyte Pb Quartiles0
for B-cell NHL for Females:
Q1: 1.7019-3.6079 pg/dL
Q2: 3.6719-5.4739 pg/dL
OR:
B-cell NHL:
Total study population
Q1: Reference
Q2: 0.93 (0.51, 1.67)
Q3: 0.91 (0.47, 1.79)
Q4: 0.93 (0.43, 2.02)
p for trend: 0.849
Males:
Q1: Reference
Q2: 0.57 (0.23, 1.37)
Q3: 0.83 (0.35, 1.99)
Q4: 0.74 (0.27, 2.04)
p for trend: 0.742
Females:
Q1
Q2
Q3
Q4
Reference
0.62 (0.23, 1.65)
0.54 (0.20, 1.46)
0.42 (0.12, 1.47)
p for trend: 0.17
MM:
Total study population:
Q1: Reference
Q2: 1.30 (0.44, 3.86)
Q3: 1.17 (0.38, 3.59)
Q4: 1.63 (0.45, 5.94)
p for trend: 0.533
Males:
Insufficient data for models
Females:
Q1: Reference
10-35
-------
Reference and
Study Design
Study Population
Exposure Assessment
Outcome
Confounders
Effect Estimates and 95%
Clsa
Q3: 5.5401-7.7823 pg/dL
Q2:
0.71 (0.20,
2.57)
Q4: 7.8313-40.0843 pg/dL
Q3:
0.71 (0.19,
2.61)
Q4:
0.74 (0.14,
3.83)
Erythrocyte Pb Quartiles0
for MM:
Q1
Q2
Q3
Q4
1.1199-3.5133 [jg/dL
3.5184-5.1973 pg/dL
5.2459-7.9079 [jg/dL
8.1448-67.2484 pg/dL
Erythrocyte Pb Quartiles0
for MM for Males:
Q1
Q2
Q3
Q4
1.9898-3.6049 [jg/dL
3.8613-5.2578 pg/dL
5.2808-9.3128 pg/dL
9.7683-67.2482 pg/dL
Erythrocyte Pb Quartiles0
for MM for Females:
Q1
Q2
Q3
Q4
1.1199-3.0604 pg/dL
3.2928-4.8623 pg/dL
4.9859-7.5424 pg/dL
7.6344-22.0943 pg/dL
p for trend: 0.692
OR by NHL subtype
associated with a one unit
increase in log transformed
exposure levelsd:
MM:
Total study population: 1.04
(0.57, 1.90)
Males: 0.83 (0.35, 1.96)
Females: 1.28 (0.53, 3.08)
DLBCL:
Total study population: 0.60
(0.26, 1.40)
Males: 0.97 (0.35, 2.64)
Females: 0.29 (0.07, 1.18)
B-cell CLL:
Total study population:
0.71 (0.32, 1.57)
Males: 0.63 (0.23, 1.74)
Females: 0.79 (0.17, 3.60)
FL:
Total study population:
1.17 (0.52, 2.63)
Males: 0.80 (0.25, 2.55)
Females: 1.91 (0.54, 6.78)
10-36
-------
Reference and
Study Design
Study Population
Exposure Assessment
Outcome
Confounders
Effect Estimates and 95%
Clsa
OR for BLL >10 pg/dL:
B-cell NHL:
Total study population: 1.10
(0.60, 2.02)
Males: 0.93 (0.44, 1.98)
Females: 1.50 (0.53, 4.21)
MM:
Total study population: 1.29
(0.48, 3.45)
Males: 0.80 (0.21, 2.98)
Females: 2.50 (0.49, 12.89)
Deubler et al.
(2020)
U.S.
1992-1993 (1998-
2001)
Case-control
Cancer Prevention
Study-ll Nutrition
Cohort (CPS-II NC)
n: 375 B-cell NHL or
MM cases (95 DBLCL,
90 CLL/SLL, 62 FL, 76
MM and 52 other
B-cell lymphoma) and
750 matched controls
The CPS-II NC was
initiated in 1992 to
1993 and enrolled
184,185 men and
women aged 40 to 90
(median = 62.0) yr
residing in 21 states.
Participants self-
reported exposure
information and cancer
diagnoses by
completing an initial
baseline questionnaire
in 1992 to 1993 and
biennial follow-up
Blood (erythrocytes)
Blood was measured by
ICP-MS
Age at Measurement:
Average age of cases at
the time of blood draw:
69.8 yr
Average age of controls at
time of blood draw: 69.9 yr
Median0: 3.05 pg/dL
Maxc: 13.88 pg/dL
Erythrocyte Pb Quartiles0:
Entire cohort:
Q1: Oto <2.1008 pg/dL
Q2: 2.1008 to
<3.0268 pg/dL
Q3: 3.0268 to <4.094 pg/dL
Q4: >4.094 pg/dL
Other cancers: B-cell NHL
and multiple myeloma
Self-reported cancer
diagnoses were verified
through medical records or
state cancer registry linkage.
Verified incident B-cell NHL
(B-NHL) and MM were
identified from CPS-II NC
participants who were
cancer-free at time of blood
collection (1998 and 2001).
B-NHL cases were further
categorized into the following
subtypes using the 2008
WHO classification scheme:
CLL/SLL, DLBCL, FL, MM,
and other B-cell lymphoma.
Age at Outcome:
Average age at diagnosis:
75 yr
Conditional logistic
regression models
estimated relative
risks (RR) adjusted
for smoking status
(current, former,
never), average
alcohol consumption
(none, <1,1, >2,
missing drinks per
day) and multivitamin
use in the week prior
to blood draw (yes,
no, missing), based
on a 10% change in
the parameter
estimates criterion
RR:
Overall lymphoid malignancy
Entire cohort: 1.088 (1.009,
1.173) per 1-SD (1.76 pg/dL)
increase of erythrocyte Pb
concentration
Males: 1.131 (1.027, 1.246)
per 1-SD (1.81 pg/dL)
increase of erythrocyte Pb
concentration
Females: 1.013 (0.886, 1.158)
per 1-SD (1.56 pg/dL)
increase of erythrocyte Pb
concentration
RR for Overall lymphoid
malignancy and erythrocyte
Pb quartiles:
Entire cohort:
Q1
Q2
Q3
Q4
Reference
1.35 (0.94, 1.95)
1.06 (0.71, 1.56)
1.52 (1.02, 2.25)
10-37
-------
Outcome
Confounders
Effect Estimates and 95%
Clsa
Males:
Q1:
Reference
Q2:
1.53 (0.93,
2.52)
Q3:
1.41 (0.84,
2.38)
Q4:
1.85 (1.10,
3.12)
Females:
Q1:
Reference
Q2:
0.98 (0.57,
1.67)
Q3:
1.04 (0.61,
1.78)
Q4:
0.92 (0.51,
1.65)
RR:
All B-cell NHL:
Entire cohort: 1.093 (1.005,
1.19) per 1-SD (1.76 pg/dL)
increase of erythrocyte Pb
concentration
Males: 1.151 (1.03, 1.286) per
1-SD (1.81 pg/dL) increase of
erythrocyte Pb concentration
Females: 1.013 (0.869, 1.18)
per 1-SD (1.56 pg/dL)
increase of erythrocyte Pb
concentration
Reference and
Study Design
Study Population
questionnaires
beginning in 1997.
Exposure Assessment
Males:
Q1: Oto <2.4736 pg/dL
Q2: 2.4736 to
<3.2876 pg/dL
Q3: 3.2876 to
<4.4026 pg/dL
Q4: >4.4026 pg/dL
Females:
Q1: Oto <1.8132 pg/dL
Q2: 1.8132 to
<2.5087 pg/dL
Q3: 2.5087 to
<3.6404 pg/dL
Q4: >3.6404 pg/dL
DLBCL
Entire cohort: 1.088 (0.943,
1.256) per 1-SD (1.76 pg/dL)
increase of erythrocyte Pb
concentration
Males: 1.07 (0.897, 1.276) per
1-SD (1.81 pg/dL) increase of
erythrocyte Pb concentration
Females: 1.183 (0.895, 1.565)
per 1-SD (1.56 pg/dL)
10-38
-------
Reference and
Study Design
Study Population
Exposure Assessment
Outcome
Confounders
Effect Estimates and 95%
Clsa
increase of erythrocyte Pb
concentration
CLL/SLL:
Entire cohort: 1.083 (0.916,
1.28) per 1-SD (1.76 pg/dL)
increase of erythrocyte Pb
concentration
Males: 1.274 (1.016, 1.598)
per 1-SD (1.81 pg/dL)
increase of erythrocyte Pb
concentration
Females: 0.736 (0.524, 1.034)
per 1-SD (1.56 pg/dL)
increase of erythrocyte Pb
concentration
FL:
Entire cohort: 1.397 (1.085,
1.798) per 1-SD (1.76 pg/dL)
increase of erythrocyte Pb
concentration
Males: 1.301 (0.951, 1.78) per
1-SD (1.81 pg/dL) increase of
erythrocyte Pb concentration
Females: 2.158 (1.07, 4.353)
per 1-SD (1.56 pg/dL)
increase of erythrocyte Pb
concentration
Other B-cell lymphoma:
Entire cohort:0.93 (0.717,
1.206) per 1-SD (1.76 pg/dL)
increase of erythrocyte Pb
concentration
Males: 1.022 (0.674, 1.549)
per 1-SD (1.81 pg/dL)
10-39
-------
Reference and
Study Design
Study Population
Exposure Assessment
Outcome
Confounders
Effect Estimates and 95%
Clsa
increase of erythrocyte Pb
concentration
Females: 0.803 (0.502, 1.284)
per 1-SD (1.56 pg/dL)
increase of erythrocyte Pb
concentration
MM:
Entire cohort: 1.114 (0.932,
1.332) per 1-SD (1.76 pg/dL)
increase of erythrocyte Pb
concentration
Males: 1.111 (0.887, 1.392)
per 1-SD (1.81 pg/dL)
increase of erythrocyte Pb
concentration
Females: 1.148 (0.81, 1.627)
per 1-SD (1.56 pg/dL)
increase of erythrocyte Pb
concentration
aEffect estimates are standardized to a 1 |jg/dL increase in blood Pb or a 10 |jg/g increase in bone Pb, unless otherwise noted. If the Pb biomarker is log-transformed, effect
estimates are standardized to the specified unit increase for the 10th-90th percentile interval of the biomarker level. Effect estimates are assumed to be linear within the evaluated
interval. Categorical effect estimates are not standardized.
bUnits assumed to be pg/dL (written as pg/L in the paper).
°Blood Pb measurements were converted from pg/Lto pg/dL.
dEffect estimates unable to be standardized.
fFrom 2013 Pb ISA.
ALAD = 6-aminolevulinic acid dehydratase; BLL = blood lead level; BMI = body mass index; CLL = Chronic Lymphatic Lymphoma; CLL/SLL = chronic lymphocytic leukemia/small
lymphocytic lymphoma; CPS-II = Cancer Prevention Study-ll (CPS-II) LifeLink Cohort; CRP = C-reactive protein; DLBCL = diffuse large B-cell lymphoma; EPIC- = European
Prospective Investigation into Cancer and Nutrition; FL = follicular lymphoma; GFAAS = graphite furnace atomic absorption spectrometry; GFR = glomerular filtration rate;
HR = hazard ratio; ICD = International Classification of Diseases; ICP-MS = inductively coupled plasma mass spectrometry; KNHANES = Korea National Health and Nutrition
Examination Survey; MM = multiple myeloma; NHANES = National Health and Nutrition Examination Survey; NHL = non-Hodgkin's lymphoma; NSDHS = Northern Sweden Health
and Disease Study; OR = odds ratio; Pb = lead; PIR = poverty-income ratio; RR = relative risk; SD = standard deviation; UC = urothelial carcinoma; WHO = World Health
Organization.
10-40
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