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

• Author: Myra M. Tetteh,Natalie Sampson,Yolanda R. Hill‐Ashford,Kelly A. Hogan,Marya G. Zlatnik,Tracey J. Woodruff,Amy J. Schulz,Rita Loch‐Caruso,Patricia D. Koman,Donele Wilkins,Rebecca Mandell,Chris M. Coombe
• Date: 01 March 2018
• Published date: 01 March 2018
• DOI: http://doi.org/10.1002/wmh3.257

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

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

Introduction

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

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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