Birth Outcomes and Maternal Proximity to Natural Gas

Development in Rural Colorado

Lisa McKenzie, PhD, MPH

Department of Environmental and Occupational Health Colorado School of Public Health, University of Colorado

Birth Outcomes

A major birth defect occurs in 1 out of 33 births

Birth defects are responsible for 1 in 5 deaths for infants less than a year old

Estimated annual health costs of birth

defects = $2.5 billion

Birth Outcomes

Preterm Birth 12 percent of births

Greater risk of newborn death and a variety of health and developmental problems

$26.2 billion in health and economic costs in 2005

Low Birth Weight

8.1 percent of births

Birth Outcomes and Environmental Exposures

Several studies have associated maternal exposure to toluene, xylene, and benzene with an increased prevalence of birth defects.

Other studies have associated maternal exposure to particulate matter, nitrogen dioxide, and volatile organic compounds with an increased risk of

Low birth weight

Preterm Birth

Natural Gas Operations

Can emit many chemicals

Directly

Diesel Engines

Toluene and xylene are teratogens (agents that cause birth defects)

Benzene is a mutagen and a carcinogen

Cross the placenta

Historically as Close as 150 feet from residences.

Truck traffic 40 to 1365 round trips per multi-stage well (Witter 2013,

NYDEC 2011)

Dispersed and near well pad

Living along haul routes (trucks for more than 1 well/ pad)

Round the clock

~ 340,000 Coloradoans Live in within one mile of an oil or gas well drilled since the year 2000.

Human Health Risk Assessment Found a Potential Developmental Health Hazard Near Wells during

Well Completions

4

2

3

1

0

1

2

3

4

5

Neurological Effects Respiratory Effects Hematogical Effects Developmental Effects

Hazard

In

dex

End Points

Study Goal

Explore the association between a mothers proximity to natural gas development while pregnant and birth outcomes

Retrospective Cohort Study

Identify a group of subjects (the cohort): 124,832 infants born between 1996 and 2009 in rural

Colorado

Determine exposures that occurred in the past (retrospective) Proximity of mothers home at the time of birth to

natural gas development

Follow the cohort after the exposure for occurrence of a health outcome Birth Outcomes

The Cohort

124,832 infants born between 1996 and 2009

Rural areas and towns with populations less than 50,000 (Denver-Metropolitan area, El Paso County and the cities of Fort Collins, Boulder, Pueblo, Grand Junction and Greely excluded)

White Hispanic and Non-Hispanic Mothers

Singleton live births

EXPOSURE

Found all gas wells that existed in the infants birth year within 10 miles of where the mother was living on

the birth date of her infant

Ten Miles Ten Miles

Exposed Unexposed

Location of the wells in relation to the mothers home matters

Measured the distance of each gas well from the Mothers home

Inverse Distance Weighting (IDW)

inverse distance =

1

Inverse Distance Weighted Count

Calculated the inverse distance weight for each well

Then added all the inverse distance weights for wells in the 10 radius around the mothers home.

The closer a well is to the home, the more influence/weight it has in the count.

Examples for 4 wells

All wells 1 mile away: IDW = 1/1 + 1/1 + 1/1 + 1/1 = 4

All wells 5 miles away: IDW = 1/5 + 1/5 + 1/5 + 1/5 = 0.8

2 wells 1 mile away, 2 wells 2 miles away = 1/1 + 1/1 +1/2 +1/2 = 2.4

Tertiles

Exposed Group

Low (1 to 3.62 wells per mile)

High (126 to 1400

wells per mile)

Medium (3.63 to

125 wells per mile)

Birth Outcomes

Congenital Heart Defects

Neural Tube Defects (anencephalus and spina bifida)

Oral Clefts (cleft lip and cleft palate)

Preterm birth (less than 37 weeks of pregnancy completed)

Term Low Birth Weight (less than 2500 grams ~ 5 pounds)

Odds Ratios

Calculated with a logistic regression Compares the prevalence of the birth outcome in

the exposed groups (tertiles) to the birth outcome in the unexposed group Greater than one indicates a positive association Less than one indicates a negative association 1 indicates no association

Adjusted for other things that may cause the birth outcome (Mothers smoking, alcohol use, education, age, and ethnicity, elevation of mothers home, parity, and infant gender).

Results

Between 1996 and 2009, 47 Percent of Births in Rural Colorado to Mothers

with Wells within 10 miles of Residence

Cohort Characteristics - Ethnicity

0

10

20

30

40

50

60

70

80

UnexposedGroup

Low Medium High

Pe

rce

nt

White Non-Hispanic White Hispanic

Cohort Characteristics - Smoking

0

2

4

6

8

10

12

14

16

Unexposed Low Medium High

Pe

rce

nt

Smoking

Cohort Characteristics - Elevation

0

1000

2000

3000

4000

5000

6000

7000

8000

Unexposed Low Medium High

Feet

Median Elevation

Congenital Heart Defects

Low = first tertile, 1 to 3.62 wells per mile, medium = second tertile, 3.63 to 125 wells per mile, high = third tertile, 126 to 1400 wells per mile. Adjusted for maternal age, ethnicity, smoking, alcohol use, education, and elevation of residence, as well as infant parity and gender.

Specific Heart Defects Ventricular Septal Defects Pulmonary Artery and Valve Defects

Tricuspid Valve Defects

Neural Tube Defects

Low = first tertile, 1 to 3.62 wells per mile, medium = second tertile, 3.63 to 125 wells per mile, high = third tertile, 126 to 1400 wells per mile. Adjusted for elevation of residence.

Oral Clefts

Low = first tertile, 1 to 3.62 wells per mile, medium = second tertile, 3.63 to 125 wells per mile, high = third tertile, 126 to 1400 wells per mile. Adjusted for maternal age, ethnicity, smoking, alcohol use, education, and elevation of residence, as well as infant parity and gender.

Preterm Birth (< 37 weeks)

Low = first tertile, 1 to 3.62 wells per mile, medium = second tertile, 3.63 to 125 wells per mile, high = third tertile, 126 to 1400 wells per mile . Adjusted for maternal age, ethnicity, smoking, alcohol use, education, and elevation of residence, as well as infant parity and gender.

Term Birth Weight (< 2500 grams, 1 gram = 0.0022 pounds )

Low = first tertile, 1 to 3.62 wells per mile, medium = second tertile, 3.63 to 125 wells per mile, high = third tertile, 126 to 1400 wells per mile . Adjusted for maternal age, ethnicity, smoking, alcohol use, education, and elevation of residence, as well as infant parity, gender, and gestational age.

Sensitivity Analysis: Narrow Exposed and Widen Unexposed

Limitation Undercounting of Birth Defect Outcomes

Did not include fetal deaths and terminated pregnancies

Birth defects diagnosed later in life may have been missed

Tends to weaken observed associations

Limitation: Grouping Birth Defects into Board Categories

May obscure associations

May weaken observed associations

Limitation: Information on potentially important confounders not available

Maternal folate consumption

Other Exposures

Genetic Information

Prenatal Care

Socioeconomic Status

Pregnancy Complications

Affect on associations is unknown

Limitation: Exposure Misclassification Maternal residence during the first trimester

Approximately 22 30 percent of mothers relocate during pregnancy Affect on associations is unknown

Gas well existence confirmed for year of birth only. Affect on associations is unknown.

Lack of information on parents occupation and time mother spent at residence. Affect on associations is unknown

Specific activities occurring at well sites Development, producing, shut-in? Accidents Weaken observed associations

Next Steps

Prospective cohort studies for preterm and birth weight.

Case Control Studies for birth defects Confirm mothers residence in first trimester

Parents occupation

Folate consumption

Investigate specific well pad activities in first trimester

Other significant environmental exposures

Conclusions

These results suggest a positive association between greater density and proximity of natural gas wells within a 10-mile radius of maternal residence and greater prevalence of CHDs and possibly NTDs, but not oral clefts, preterm birth, or reduced fetal growth.

Further study is needed to address the limitations of this research

Why is this important? The Wall Street Journal estimates that over 15 million Americans live within one mile of an O&G well that was drilled after the year 2000 (Russell Gold October 25, 2013). Our results, results of other research teams, and the current trends in natural gas development underscore the importance of conducting more comprehensive and rigorous research on the potential health effects of oil and gas development using unconventional methods.

Acknowledgements

CSPH Colleagues: Roxana Witter, John Adgate, Lee Newman, Ruixen Guo, David Savitz, Brown University

Colorado Department of Public Health (CDPHE) and Environments Health Statistics and Colorado Responds to Children with Special Needs Sections provided outcome data for this study. CDPHE specifically disclaims responsibility for any analyses, interpretations, or conclusions.

Funding from the Colorado School of Public Health Department of Environmental and Occupational Health

McKenzie L.M., Guo, R., Witter R.Z., Savtiz, D.A. Newman L.S., Adgate J.L., Birth Outcomes and Maternal Residential Proximity to Natural Gas Development in Rural Colorado. Environmental Health Perspectives. 2014; 122 (4): 412-417. http://ehp.niehs.nih.gov/1306722/