Examining Joint Effects of Air Pollution Exposure and Social Determinants of Health in Defining “At‐Risk” Populations Under the Clean Air Act: Susceptibility of Pregnant Women to Hypertensive Disorders of Pregnancy

Date01 March 2018
Published date01 March 2018
Examining Joint Effects of Air Pollution Exposure and
Social Determinants of Health in Def‌ining “At-Risk”
Populations Under the Clean Air Act: Susceptibility of
Pregnant Women to Hypertensive Disorders of
Patricia D. Koman , Kelly A. Hogan, Natalie Sampson, Rebecca Mandell,
Chris M. Coombe, Myra M. Tetteh, Yolanda R. Hill-Ashford, Donele Wilkins,
Marya G. Zlatnik, Rita Loch-Caruso, Amy J. Schulz, and Tracey J. Woodruff
Pregnant women are uniquely susceptible to adverse effects of air pollution exposure due to
vulnerabilities and health consequences during pregnancy (e.g., hypertensive disorders of pregnancy
[HDP]) compared to the general population. Because the Clean Air Act (CAA) creates a duty to
protect at-risk groups, the regulatory assessment of at-risk populations has both policy and scientif‌ic
foundations. Previously, pregnant women have not been specially protected in establishing the
margin of safety for the ozone and particulate matter (PM) standards. Due to physiological changes,
pregnant women can be at greater risk of adverse effects of air pollution and should be considered an
at-risk population. Women with preexisting conditions, women experiencing poverty, and groups
that suffer systematic discrimination may be particularly susceptible to cardiac effects of air
pollutants during pregnancy. We rigorously reviewed 11 studies of over 1.3 million pregnant
women in the United States to characterize the relationship between ozone or PM exposure and
HDP. Findings were generally mixed, with a few studies reporting a joint association between ozone
or PM and social determinants or pre-existing chronic health conditions related to HDP. Adequate
evidence associates exposure to PM with an adverse effect of HDP among pregnant women not
evident among non-gravid populations.
KEY WORDS: air pollution, cardiovascular disease, pregnancy
Populations that experience multiple social, physical, and chemical environ-
mental stressors are at increased risk of disease (Brulle & Pellow, 2006; Morello-
Frosch, Zuk, Jerrett, Shamasunder, & Kyle, 2011; Payne-Sturges et al., 2006;
Vesterinen, Morello-Frosch, Sen, Zeise, & Woodruff, 2017). Disparities in health
World Medical & Health Policy, Vol. 10, No. 1, 2018
doi: 10.1002/wmh3.257
#2018 Policy Studies Organization
outcomes may be produced by both environmental (e.g., physical, chemical, and
biological agents) and social factors (e.g., individual- and community-level traits
such as socioeconomic position, education, psychosocial stress, coping resources
and support systems, residential factors, cultural traditions, and institutional,
structural, and political processes such as racism and classism) (Institute of
Medicine, 1999). Residents of low to moderate income urban communities, who
are likely to be non-Hispanic Black and Hispanic, are more likely to be exposed
to multiple air pollutants in some areas of the United States (Gray, Edwards, &
Miranda, 2013; Morello-Frosch, Jesdale, Sadd, & Pastor, 2010; Morello-Frosch
et al., 2011; Schulz et al., 2016; Su, Jerrett, Morello-Frosch, Jesdale, & Kyle, 2012;
U.S. EPA, 2015; Woodruff, Darrow, & Parker, 2008; Woodruff, Parker, Kyle, &
Schoendorf, 2003). Residents of such communities experience higher rates of
adverse health effects of air pollutants due to higher rates of pre-existing chronic
conditions such as asthma, obesity, diabetes, and cardiovascular disease (Kannan,
Misra, Dvonch, & Krishnakumar, 2006; MDOCH, 2007; Wasilevich, 2008). These
vulnerabilities coincide with social stressors such as poverty, poor housing,
reduced access to nutritious foods and health care, and psychosocial stress, which
further exacerbate adverse health effects from air pollution (Bower, Thorpe,
Rohde, & Gaskin, 2014; Kannan et al., 2010). Thus, to fully characterize the
relationship between air pollution exposure and health and which populations
are at risk, the role of multiple chemical and social stressors must be considered
when creating policies that protect women susceptible to environmental expo-
sures (National Research Council, 2009).
Despite the cumulative effects of multiple chemical and social exposures and
underlying population burden of disease, many environmental policy decisions
rely on risk assessments that consider single chemical exposures rather than
combined exposures of chemicals and social stressors. This is in part a result of
the nature of the available controls (e.g., engineering devices or strategies to ban
or replace an individual chemical), legislative authority, or the methodological
goal to isolate and establish causal connections between individual chemical
exposures and health outcomes. Nevertheless, several science policy reports
highlighted the need for more systematic consideration of combined risks from
multiple chemical and social environmental stressors (Institute of Medicine, 1999;
National Research Council, 1994, 2009; Omenn, 1997; Thurston et al., 2017). A
joint European Respiratory Society/American Thoracic Society (ATS) policy
statement notes that health equity and environmental justice considerations are
relevant to population risk assessments (Thurston et al., 2017). One of these
factors is higher burdens of chronic health conditions, such as diabetes and
hypertension, that are socially patterned with higher risk among low-income
people (Brummett et al., 2011; Menke, Casagrande, Geiss, & Cowie, 2015). Air
pollution adds another burden to populations already at higher risk of disease
from exposure to adverse social and economic contexts or with higher prevalence
of chronic disease, and pollution exposures may have disparate impacts on
people in higher risk groups (Institute of Medicine, 1999; Thurston et al., 2017).
Researchers have proposed frameworks for studying the shared etiologic path-
8 World Medical & Health Policy, 10:1
ways of air pollution and negative social factors (Erickson, Ostry, Chan, &
Arbour, 2016; Institute of Medicine, 1999; Payne-Sturges et al., 2006; Solomon,
Morello-Frosch, Zeise, & Faust, 2016). To be useable in policy decisions, these
research frameworks and resulting evidence must be connected to regulatory
assessment methods (Koman & Mancuso, 2017).
In this study, to improve the identif‌ication of “at-risk” populations for
regulatory risk assessment, we f‌irst critically examine regulatory methods used to
set U.S. air pollution standards as they apply to pregnant women. We then
evaluate the disease category of hypertensive disorders of pregnancy (HDP), as
exemplars of maternal health outcomes that are currently undervalued in
regulatory decision making. Further, HDP are important causes of morbidity and
mortality for pregnant women (Dolea & AbouZahr, 2003), and as such, are major
causes of disease and death in young women. Preeclampsia is a leading cause of
maternal mortality and morbidity affecting 2–10 percent of pregnancies in the
United States (ACOG, 2013a; Sibai, Dekker, & Kupferminc, 2005; Steegers, von
Dadelszen, Duvekot, & Pijnenborg, 2010). HDP are associated with air pollution
exposure (Hu et al., 2014; Pedersen et al., 2014) and are also associated with social
determinants of health including residential poverty and race (Erickson &
Arbour, 2014; Tanaka et al., 2007).
HDP can be a harbinger of poor long-term cardiovascular health for the
mother (Amaral, Cunningham, Cornelius, & LaMarca, 2015; Lykke, Langhoff-
Roos, Lockwood, Triche, & Paidas, 2010). HDP has been linked to development of
cardiovascular diseases decades after pregnancy and therefore represents a risk
factor that undermines long-term health in women who have experienced HDP in
pregnancy (Amaral et al., 2015). Furthermore, in the decades following preg-
nancy, HDP is associated with smaller maternal brain volume and decreased
performance on tests of processing speed (Mielke et al., 2016; Nelander et al.,
2016). In addition to a predisposition to cardiovascular and neurological changes
associated with HDP in later life, women experiencing HDP are at greater risk for
end-stage renal disease (Wang et al., 2013) and diabetes (Theilen et al., 2016). The
mechanisms of long-term consequences of HDP on health are not well elucidated
but may be related to changes in anti-angiogenic and immune factors occurring
during HDP (Amaral et al., 2015), which manifest as a disease threshold later in
life (Arabin & Baschat, 2017). Pregnancy has long been described as a “stress test
for life” because pregnancy complications such as HDP often manifest later in life
as essential hypertension (Williams, 2003). In addition to the impacts on the
mother’s health, preeclampsia is a major risk factor for adverse birth outcomes
such as fetal growth restriction and preterm birth, which have health implications
for both mother and fetus (Clausson, Cnattingius, & Axelsson, 1998; Ota et al.,
2014). Racial disparities for birth outcomes have been documented, but not fully
explained. Therefore, protection of pregnant women who are particularly
vulnerable to hypertensive disorders or women who have higher odds of entering
pregnancy with chronic hypertension due to susceptibilities that are patterned by
race or ethnicity (Ghosh et al., 2014) should be a policy priority, particularly in
instances where exposure to air pollutants is more likely.
Koman et al.: Air Pollution Standards and Pregnancy 9

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