Effect of Air Pollution on Birth Outcomes in Pittsburgh

Effect of Air Pollution on Birth Outcomes in Pittsburgh

Evelyn Talbott, Dr.P.H., M.P.H. Xiaohui Xu, MD, PhD

Pei Chen Lee, PhD Ravi Sharma, PhD Judith Rager, MPH Stacey Benson, MS

University of Pittsburgh,

Graduate School of Public Health

May 7, 2013

Collaborators • Ravi K. Sharma, PhD, Assistant Professor, Department of Behavioral and

Community Health Sciences, , University of Pittsburgh, Graduate School of Public Health

• Xiaohui Xu, MD, PhD, Assistant Professor, Department of Epidemiology & Biostatistics, College of Public Health and Health Professions, University of Florida

• Pei Chen Lee, PhD, Assistant Professor, Department of Health Care Management, National Taipei University of Nursing and Health Sciences, Taipei, Taiwan

• Luann L. Brink, PhD, Visiting Assistant Professor of Epidemiology, University of Pittsburgh, Graduate School of Public Health

• Judith Rager, MPH, Senior Research Specialist, University of Pittsburgh, Graduate School of Public Health

• Stacey Benson, MS, Graduate Student, Department of Epidemiology, University of Pittsburgh, Graduate School of Public Health

• *Funding for these studies provided Centers for Disease Control: Academic Partners in Environmental Public Health Tracking:1 U19EH000103-02( 2005-2010)

Objectives

• Define adverse birth outcomes, air pollution exposures and biological mechanisms of disease.

• Present results of some early studies, a overview of the literature related to AP and birth outcomes and present studies specific to Pittsburgh.

• Air pollution at both national and local levels as will be described in this presentation has a significant impact on the risk of adverse birth outcomes.

• These outcomes are associated with ambient levels currently still seen in Pittsburgh and in other locations.

Definitions -Outcomes -Burden -Risk Factors -Exposures

Lit Review

-Early Studies -Overall Findings -Summary

Biological Mechanisms

Pittsburgh Studies

-Xu et al. -Lee et al. -Lee et al.

Define Outcomes

• What are adverse birth outcomes?

Preterm Birth (PTB) • <37 completed weeks of gestation

Low Birth Weight (LBW)

• <2500 grams or 5.5 pounds

Intrauterine Growth Restriction (IUGR) • Small for gestational age (SGA): ≤10th percentile

for weight of all fetuses at that gestational age

References: Sibai BM. Obstet Gynecol. 2003;102(1):181-192 Ross and Mansano. 2008. http://emedicine.medscape.com/article/261226-overview

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Burden of Disease

• Low birth weight (LBW)is a leading cause of neonatal mortality (death before 28 days of age). LBW infants are more likely to experience physical and developmental health problems or die during the first year of life than are infants of normal weight.1,2

• In 2009, 8.2 % of US infants were born in the LBW (< 5.5 lb) category. In 2006, the rate of LBW was the highest recorded in four decades (8.3 %).

• In 2009, the rate of LBW was much higher among infants born to African American women (13.6 %) compared to 7.2% in Caucasians.

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White Black Other All Races

Pre

va

len

ce

of

Lo

w B

irth

We

igh

t (%

) PA Allegheny County US

Data from the Commonwealth of Pennsylvania - Department of Health, Health Statistics and Research 2010 and the National Vital Statistics Report. Vol 61, Number 1

*

* Other is the designated category for PA, for the US it is designated Hispanic

Prevalence of Low Birth Weight: 2010

Healthy People 2010 Goal was 5%

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Risk factors

References: Slattery MM and Morrison JJ. Lancet. 2002;306:1489-1497; Berkowitz GS et al., Epidemiology. 1998;9:279-285; Villar et al., Am J Obstet Gynecol. 2006;194:921-931 Severi et al., Fetal Diagn Ther. 2000;15:8-19.

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Preterm Birth Low Birth Weight IUGR

Incidence 12% in the US in 2000 8% About 10%

Risk Factors -age of mother

-race

-parity : number of children

-previous preterm birth

-prenatal care after the first

trimester

-preexisting diabetes mellitus

-infections

-smoking during pregnancy

-multiple births

-age/race

-maternal smoking

-gestational age

-multiple births

-chronic hypertension

-pregnancy-associated

hypertension

-preexisting diabetes

-smoking

-multiple births

-placenta abnormalities

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Define Exposures

• What is ambient air pollution?

Source: google pictures

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• Six principal pollutants, which are called "criteria" pollutants

– Particulate Matter (PM10 ,PM2.5,and TSP)

– Ozone (O3)

– Carbon Monoxide (CO)

– Nitrogen Dioxide (NO2)

– Sulfur Dioxide (SO2)

– Lead

Define Exposures (Cont.)

Source: National Ambient Air Quality Standards (NAAQS)

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Possible Biological Mechanisms

Reference: Slama et al., Environ Health Perspect. 2008;116:791-798

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Is Ambient Air Pollution a Risk Factor for Adverse Birth Outcomes? Early Studies:

Reference: Williams et al., Soc Biol. 1977; Spring;24(1):1-9

• First study that connected air pollution and risk of LBW was in the LA Basin (Williams et al., 1977)

– The hypothesis was based on the finding that women who smoked 1+ packs cigarettes/day have babies that are 100-300 grams less than nonsmoking mothers.

– A systematic sample of 1500 women who delivered in 1973 was selected and exposure to light, moderate, or high air pollution levels was assigned based on residence at birth.

– Average readings were accumulated over trimesters.

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Los Angeles Basin circa 1960’s Outline



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Williams et al.

• CO, NO2 and O3 pollutants were monitored. These generally co-exist with particulates which were not used in the analysis.

• The women were stratified by smoking history .

• Among non smoking women, the birth weight difference between heavy and light pollution areas was a 277 gram difference (p<.05) after adjusting for parity, education, etc.

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Early International Study of Preterm Delivery and Air Pollution: acute effects: Xu et al. 1995

Reference: Xu et al., Arch Environ Health. 1995;50:407-415

• Prospective study of preterm delivery among 25,370 resident women in four Beijing Provinces. Women were registered at their OB/GYN hospitals from early pregnancy until delivery in 1988.

• Pollution (TSP and SO2) and temperature were recorded daily.

• Results: – Levels of these pollutants in China in 1988 were quite high

(SO2 100 ug/m3 and TSP =375 ug/m3)

– A significant dose dependent association was noted between gestational age and SO2 and TSP. Adjusted odds ratio for preterm delivery (<37 wks) was 1.10 (1.01-1.20) for each 100 ug/m3 of TSP.

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Early International Study of Preterm Delivery and Air Pollution: acute effects: Xu et al. 1995

Reference: Xu et al., Arch Environ Health. 1995;50:407-415

– High pollution days resulted in a skewed distribution of preterm birth to the left.

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Ambient air pollution, birth weight, and pre term birth: A systematic review and Meta-analysis

Stieb et al. Environmental Research 117:2012, 101-111

• Review of 62 studies of the association of air pollution and LBW and PT birth (1980-2011)

• Most studies reported reduced birth weight and increased odds of LBW in relation to exposure to carbon monoxide (CO), nitrogen dioxide (NO2), and PM2.5 and PM10

• Pooled estimates of a decrease in birth wt. ranged from 11.4 g ( 95% CI -6.9 to -29.7) /1 ppm of CO to 28.1 g (-11.5--44.8) per 20 ppb of NO2 .

• An increase in risk for LBW ranged from 5% increase per 10 ug/m3 PM2.5 to 10% increase per 20 ug/m3 PM10 based on entire pregnancy.

• Results were less consistent for ozone and SO2

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Change in Birth

Weight (g) per

20 ug/m3

increase PM10

Stieb et al., Envirnmt Res. 2012; 117:100-111

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Sources of Pollution in Allegheny County

Summary

Pollutant Primary Sources

Ozone (O3) Formed in hot, sunny conditions from vehicle, commercial, and industrial emission

Particulate Matter (PM)

Coke plants, steel mills, power plants, road dust, vehicles

Sulfur Dioxide (SO2) Power plants, coke plants Carbon Dioxide (CO) Motor vehicles Nitrogen Dioxide (NO2) Power and industrial plants,

motor vehicles

Reference:2006 Air Quality Annual Report, ACHD

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Pittsburgh and Allegheny County Studies

Relationship between PM2.5 and PM10

and Birth Outcomes (Study 1)

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PM10 Air Pollution Exposure During

Pregnancy and Term Low Birth Weight in

Allegheny County, PA Xu X, Sharma RK, Talbott EO, Zborowski JV, Rager JR, Arena

VC, Volz CD

International Archives of Occupational Environmental Health,

(2011) 84: 251:257

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Objectives

Air Pollution

• To evaluate the association between PM10 and term

low birth weight (full term births <2500 g) from 1994-

2000 in Allegheny County after controlling for other

factors.

• To use PM10 data spatially and temporally generated with

inverse-distance interpolation.

• To estimate PM10 levels corresponding to the first,

second and third trimesters of pregnancy.

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PM10 exposure data

• Quarterly measures of PM10 in census tracts (CT) in Allegheny County were obtained from the RAND Center for 1993-2000

• The data were generated based on the inverse-distance interpolation related to proximity to air pollution monitors

• Quarterly PM10 from CT was aggregated to neighborhood in the city or municipality outside the city

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Birth Cohort

Air Pollution

• A total of 100,595 singleton birth records were available for Allegheny County between 1994 and 2000

• 92,447 singleton term births (≥37 completed weeks gestation)

• A total of 2,058 (2.2%) term low weight birth infants occurred over the entire study period.

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Statistical Analysis

• Dependent variable: Term Low birth weight (TLBW) – Birth weight < 2,500 g

and gestational age ≥37 weeks)

• Independent variables: – Exposure: Trimester-

specific PM10 (continuous variable)

– Confounding factors: • maternal age, race,

education, smoking status, etc.

• Logistic regression was applied for estimating the association between PM10 and TLBW

• Odd Ratios (ORs) per inter-quartile range change in trimester-specific PM10 was estimated

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Results: Distribution of characteristics of term singleton births by low birth weight status

Term LBW Characteristics

CASE

(N=2,058)

Control

(N=90,389)

OR (95%CI)

Maternal

age

<20 307 (14.9) 7,620 (8.4) 1.69 (1.49-1.93)

20-29* 949 (46.1) 39,907 (44.1) 1.0

30-34 463 (22.5) 27,628 (30.6) 0.71 (0.63-0.79)

35-39 282 (13.7) 13,002 (14.4) 0.91 (0.80-1.04)

>=40 57 (2.8) 2,232 (2.5) 1.07 (0.82-1.41)

Maternal

race

White* 1,250 (60.9) 72,087 (79.8) 1.0

Black 731 (35.6) 15,808 (17.5) 2.67 (2.43-2.93)

Other 73 (3.5) 2,392 (2.7) 1.76 (1.38-2.24)

Maternal

education

<9 43 (2.1) 641 (0.7) 4.51 (3.27-6.22)

9-11 313 (15.2) 6,662 (7.4) 3.16 (2.74-3.64)

12 761 (37.0) 27,512 (30.4) 1.86 (1.66-2.08)

13-15 425 (20.6) 20,884 (23.1) 1.37 (1.20-1.56)

>=16 * 516 (25.1) 34,690 (38.4) 1.0

Maternal

tobacco

use

Yes 879 (43.1) 16,103 (17.9) 3.48 (3.18-3.80)

No 1,160 (56.9) 73892 (82.1) 1.0

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Percentiles of PM10 concentrations during the first, second, and third trimesters

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Trimester (monthly average) Mean 25% 50% 75% 95%

1st 28.7 25.1 28.3 32.2 37.4

2nd 28.2 24.9 27.6 31.3 36.9

3rd 28.1 24.9 27.3 31.0 36.6

Risks for term low birth weighta according to trimester-specific exposure to PM10

OR (95%CI) * Exposure period

OR 95% CI

1st Trimester 1.13

b 1.02-1.25

2nd

Trimester 1.10 1.00-1.22

3rd

Trimester 1.05 0.96-1.16

* ORs were estimated by per inter-quartile range increase (per 7 μg/m3) after adjustment for

maternal age, maternal race, maternal education, smoking, weight gain, gender of infant,

gestation age, parity, previous LBW or preterm birth, level of prenatal care and birth season

aAll singleton births with gestational age ≥37 weeks bp<0.05

Odds Ratios of term LBW per interquartile range of PM10 shows a 13%

increase in the risk of term LBW in the first trimester of exposure and

10% in the second trimester after adjustment for other confounding

factors.

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Studies 2 and 3: Study Population from the Prenatal Exposures and Pre-eclampsia Prevention (PEPP) Study

“Particulate Air Pollution Exposure and C-reactive Protein During Early Pregnancy”

Lee, Pei C., Talbott, EO, Roberts, JM, Catov, JM, Sharma, RK, Ritz, B

Epidemiology, Volume 22, Number 4, July 2011, 524-531

“Ambient Air Pollution Exposure and Blood Pressure Changes During Pregnancy”

Lee, P C, Talbott, EO, Roberts, JM, Catov, JM, Sharma, RK, et al.

Journal of Environmental Research 117 (2012) pg46-63

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Study Population

• Prenatal Exposures and Pre-eclampsia Prevention (PEPP) Study (Roberts et al.) n=2,211

– a prospective cohort study recruited through Magee clinics and private practices

– healthy women aged 14-44 who enrolled in the study before 16 weeks of gestation

– between 1997 and 2001 Air Pollution

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Exposure Assessment

• Space-time ordinary Kriging interpolation method (provides an estimate of exposure spatially)

• Particles of less than 10 µm diameter (PM10) and less than 2.5 µm diameter (PM2.5), carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2), and ozone (O3) at the zip-code level.

• Note: PM2.5:1999-2001. Air Pollution

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Demographic characteristics of study population (CRP) (N=1,696)

a Adjusted for all other covariates in the table b Missing observations for maternal BMI at enrollment (n=72); maternal race other than White and African-American (n=36); and maternal cigarette exposure during early pregnancy (n=14)

Continuous Measures Mean std Gestational weeks at sample collection (weeks)

10.2 4.0

Maternal BMI at baselineb (kg/m2)

26.5 6.7

Maternal age (years) 24.8 5.9 Categorical Measures N % Maternal race/ethnicityb White 1,033 62.2 African American 627 37.8 Maternal education Less than high school 348 20.5 High school 651 38.4 Less than 4 years college 390 23.0 Above College/Bachelor 307 18.1 Parity First birth 1,023 60.3 Second or subsequent birth 673 39.7

Maternal cigarette exposure during early pregnancyb n % Active (smokers) 553 32.9 Passive (non-smokers) 707 42.0 None 422 25.1 Household income (thousands) Less than 10 434 25.6 10 to less than 20 342 20.2 20 to less than 50 341 20.1 50 or more 297 17.5 Unknown 282 16.6 Year entering the study 1997 205 12.1 1998 306 18.0 1999 380 22.4 2000 488 28.8 2001 317 18.7 Season of sample collected Spring (March-May) 535 31.5 Summer (June-August) 428 25.2 Fall (September-November) 370 21.8 Winter (December-February) 363 21.4

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The descriptive statistics of air pollution (0-7 day averages), 1997-2001

a For summer season only (April to September)

Percentile Mean ± SD 0th 25th 50th 75th 95th 100th

PM10 (µg/m3) 26.1 ± 8.3 10.7 19.9 24.4 31.2 42.2 58.7 PM2.5 (µg/m3) 16.4 ± 5.3 7.1 12.8 15.2 18.7 26.2 40.8 O3 a(ppb) 29.9 ± 7.1 4.4 25.6 30.3 34.3 41.6 51.4 CO (ppm) 0.5 ± 0.2 0.0 0.3 0.5 0.6 0.9 1.4 SO2 (ppb) 8.4 ± 3.3 1.5 6.1 7.9 10.1 14.4 25.4 NO2 (ppb) 18.8 ± 3.8 8.2 15.9 18.7 21.1 25.1 33.4

Pearson Correlation PM10 PM2.5 O3 CO SO2 NO2

PM10 (µg/m3) 1 PM2.5 (µg/m3) 0.9 1 O3 a(ppb) 0.5 0.5 1 CO (ppm) 0.1 0.0 -0.1 1 SO2 (ppb) 0.1 0.2 0.1 0.3 1 NO2 (ppb) 0.1 0.1 0.0 0.6 0.4 1

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C-Reactive Protein

• C-Reactive Protein is an inflammatory marker that has been linked to heart disease risk as well as inflammatory and immune responses to the lungs.

• A recent study by Ernst et al (August, 2011) noted that elevated CRP levels in early pregnancy were associated with lower fetal weight in the 3rd trimester and an increased risk of small for gestational age offspring.

• CRP increases as gestational weeks increase, and low grade inflammation during pregnancy has been related to preterm birth.

Summary

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CRP – Statistical Analysis

• Multiple Logistic Regression (CRP < 8 ng/mL and ≥ 8 ng/mL)

• Dependent variables: CRP concentrations

• Independent variables: air pollution concentrations, maternal age, race, pregnancy history, BMI, maternal education, season of birth, and household income Air Pollution

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Air Pollution and CRP Results

• PM2.5 exposures were associated with increased CRP concentrations in early pregnancy (<22 weeks). CO, SO2, and NO2 were not associated with CRP levels

• An increase of 4.6 ug/m3 of PM2.5averaged over 7 days before the blood draw , was associated with a 21% ↑risk for high C-reactive protein (CI=1.02-1.43)

• It appears that particulate pollution is related to elevated concentrations of a systemic inflammatory biomarker in women early in their pregnancy.

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Pei et al. study 3: Blood Pressure

• Pregnancy-induced hypertension (PIH) contributes to complications in approximately 7% to 10% of pregnancies in the United States

• A rise in systolic or diastolic blood pressure from early pregnancy to mid third trimester is associated with spontaneous preterm birth (Zhang et al. 2007)

• No study to date has linked air pollution to blood pressure changes during pregnancy

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BP Material and Methods

• Maternal blood pressure (including systolic (SBP) and diastolic pressure (DBP)) during each prenatal care visit were abstracted from hospital records. – Min visit: 3; max visit: 16; average visits: 11

• Excluded – Chronic hypertension and diabetes (N=32)

– Missing blood pressure information (N=84)

– Second-time participants in the PEPP study and Zip-code outside of Allegheny County (N=411)

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Blood Pressure Statistical Analysis

• First trimester exposure

– Considered systolic and diastolic pressure changes separately

– (average of the 2 measurements taken during the last prenatal care visits) – (average of the blood pressure measurements in the first 20 weeks of gestation)

– multiple linear regression analyses including a robust cluster variance estimator

20wks delivery V1 V2

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• Adjusted for important risk factors as well as season and year of entering the study

• Effect modifier: race (Africa-American, Caucasian)

• Studied entire population and stratified by smoking

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BP Statistical Analysis (cont.)

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Increase in average blood pressure (in mmHg) between the first 20 weeks of gestation and late pregnancy per IQR increase in 1st Trimester of air pollution exposure

a All models were adjusted for: maternal age, race, parity, number of cigarettes smoked during pregnancy, multivitamin or prenatal vitamin used during pregnancy, maternal pre-pregnancy BMI, and season and year of enrolment (for PM10 and O3: 1997 to 2001; for PM2.5: 1999 to 2001)

Change in BP (95% CI)

N Crude Adjusteda

For the entire population

PM10 (µg/m3)

SBP 1684 1.09 ( 0.38 to 1.81) 1.18 ( 0.01 to 2.26)

DBP 1684 0.47 (-0.20 to 1.14) 0.48 (-0.35 to 1.30)

PM2.5 (µg/m3)

SBP 1128 0.12 (-0.71 to 0.94) 0.40 (-0.66 to 1.46)

DBP 1128 0.23 (-0.42 to 0.87) 0.38 (-0.41 to 1.18)

O3 (ppb)

SBP 1684 1.32 (0.57 to 2.08) 1.47 (-0.10 to 3.04)

DBP 1684 0.75 (-0.05 to 1.54) 0.74 (-0.48 to 1.95)

For non-smokers

PM10 (µg/m3)

SBP 1104 1.13 (0.33 to 1.94) 1.88 ( 0.84 to 2.93)

DBP 1104 0.41 (-0.37 to 1.18) 0.63 (-0.50 to 1.76)

PM2.5 (µg/m3)

SBP 726 0.17 (-0.83 to 1.17) 0.84 (-0.33 to 2.00)

DBP 726 0.33 (-0.37 to 1.20) 0.60 (-0.27 to 1.47)

O3 (ppb)

SBP 1104 1.40 ( 0.05 to 2.30) 1.84 (1.05 to 4.63)

DBP 1104 0.65 (-0.29 to 1.59) 1.13 (-0.46 to 2.71)

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Paper 4: Association Between Air Pollution and Adverse Birth Outcomes

“First Trimester Exposure to Ambient Air Pollution, Pregnancy Complications and Adverse Birth Outcomes in Allegheny County.”

Lee ,PC, Roberts, J, Catov, J, Talbott, EO

Journal of Maternal Child Health, 2013, vol 17: 545-555

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Study Population

• Singleton births between 2000 and 2003 in Allegheny County N= 34,705

• Birth records (Birth Registry) through Magee Hospital which covers 60% of AC births (MOMI study)

• The information for each live birth includes: demographic information, geographic information (x and y coordinates), maternal pregnancy history and some risk factors of PTB, IUGR and gestational hypertension.

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• Exposure Assessments – Ambient air pollution including O3, PM10 and PM2.5

during 1st trimester • Using Space –time ordinary Kriging interpolation method

– Individual level (x and y coordinates)

• Statistical Analysis – Logistic Regression

– Dependent variables: Preterm Birth/Intrauterine Growth Restriction/Gestational Hypertension

– Independent variables: air pollution, maternal age, race, pregnancy history, BMI, maternal education, marital history, season of birth, smoking during pregnancy and household income (at census level)

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Adverse Birth Outcomes: Methods

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Results

• PM2.5 but not O3 exposures was associated with pre-eclampsia: (adjusted )OR=1.15, 95% CI=(0.96-1.39) per 4.0 ug/m3 > in PM2.5

• Gestational Hypertension: for PM2.5 OR=1.11 , 95% CI=(1.00-1.23)

• Pre term delivery: for PM2.5 OR=1.10, 95% CI=(1.01-1.20); for O3 ORs=1.23, 95% CI=(1.01-1.50).

• Data suggests that first trimester exposure to particles, mostly PM2.5 and ozone may increase the risk of developing pre-eclampsia and GD as well as preterm delivery.

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Conclusions

• Air Pollution (PM2.5 and O3) at both national and local levels as studied in these investigations have been shown to have a significant impact on the risk of adverse birth outcomes.

• These outcomes were associated with ambient levels currently still seen in Pittsburgh and in other locations.

• More research needs to be done on the effect of multiple pollutants as well as other air toxics not studied as extensively in the region.

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Documents

Effect of Air Pollution on Birth Outcomes in Pittsburgh