Congenital Heart Defects and Maternal Proximity to Oil and Gas

Development

Lisa McKenzie, PhD, MPH lisa.mckenzie@ucdenver.edu

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

A congenital heart defect occurs in 18 out of every 1000 Colorado births

Congenital Heart Defects and Environmental Exposures

Some studies have associated congenital heart defects or birth defects in general with maternal exposure to:

• toluene, xylene, and benzene

• Air pollution

• Stressful life events

Weld County. (Denver Post file photo)

Erie Colorado. (RJ Sangosti/ The Denver Post) Crude oil and condensate spilled into the Poudre River a half mile east of Windsor, upriver from Greeley, (Marc Stewart, 7News)

Oil and 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

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

High School

Special needs housing

Park

Multi-well Pad

Our Preliminary Study (McKenzie et al 2012)

Explore the association between maternal exposure to natural gas development and birth outcomes, using a dataset with individual-level birth data and geocoded natural gas well locations.

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 mother’s home at the time of birth to

natural gas development

• Follow the cohort after the exposure for occurrence of a congenital heart defect.

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

Found all gas wells that existed in the infant’s 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 mother’s home matters

Measured the distance of each gas well from the Mother’s home

Inverse Distance Weighting (IDW)

inverse distance =

1

𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑜𝑓 𝑤𝑒𝑙𝑙 𝑓𝑟𝑜𝑚 𝑚𝑜𝑡ℎ𝑒𝑟′𝑠 ℎ𝑜𝑚𝑒

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 mother’s 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 miles per mile)

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 congenital heart defect (Mother’s smoking, alcohol use, education, age, and ethnicity, elevation of mother’s home, parity, and infant gender).

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

with Wells within 10 miles of Residence

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

Current Study

Goal: Develop rigorous exposure assessment approaches that will link specific well activity and emissions models to birth data to estimate maternal exposures in the three months before conception and in the first two months of her pregnancy.

Five Case Control Studies

Figure 1. Cases and Controls

175533 births

200 Ventricular Septal Defects

42 Tricuspid Valve Defects

200 Pulmonary Artery and

Valve Defects

200 Aortic Artery and

Valve Defects

126 Conotruncal

Defects

200 Controls

252 Controls

168 Controls

200 Controls

200 Controls

Three months before and first two months of pregnancy

Air Toxics Emission Intensity for each well and other air pollution sources

• How much Oil, Condensate and Gas Produced

• Phase of production • Use of green completions

Ask about possible confounders

Why is this important?

Oil and gas development operations, which are rapidly increasing and emit known and suspected teratogens, may be associated with congenital heart defects, which have significant health consequences. The human fetus is especially sensitive to environmental chemical exposures and our preliminary work indicates that congenital heart defects may increase as maternal proximity to natural gas development increases. Our current study will address several limitations in the preliminary study.

Multi-well Pad

Acknowledgements

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

• Colorado Department of Public Health (CDPHE) and Environment’s 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 for preliminary study from the Colorado School of Public Health Department of Environmental and Occupational Health

• Funding for current study is supported by an award from the American Heart Association

I have no conflicts of interest to declare

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/