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UNIVERSITY OF COLORADO | COLORADO STATE UNIVERSITY | UNIVERSITY OF NORTHERN COLORADO
Human Health Risks Associated with
Development of Unconventional
Natural Gas Resources Impact of Unconventional Natural Gas Drilling Operations on
the Environment and Public Health
February 18, 2014
Lisa M. McKenzie, PhD, MPH
Research Associate
Department of Environmental and Occupational Health
University of Colorado
Roadmap
• Human Health Risk Assessment of Air Emissions from Development of Unconventional Natural Gas Resouces (Mckenzie, Witter, Newman, Adgate, Science
of the Total Environment, 424, 2012)
• Birth Outcomes and Proximity of Maternal Residence to Natural Gas Development in Rural Colorado (McKenzie, Guo, Witter, Savitz,
Newman, and Adgate, EHP, Advanced Publication 2014).
Battlement Mesa
The proposal
Citizen Request
“On behalf of Battlement Mesa citizens, BCC
members have requested the county and state
to conduct a "Health Impact Assessment" (HIA)
before a Special Use Permit (SUP) is approved
to any company drilling within the Battlement
Mesa PUD.”
Battlement Concerned Citizens, November 6, 2009
Data Assessment – Mann-Whitney comparison
NGD Area and Well Completions
Chemical p-value
1,2,3-Trimethylbenzene 0.0501
1,2,4-Trimethylbenzene <0.001
1,3,5-Trimethylbenzene <0.001
1,3-Butadiene 0.996
Benzene <0.001
Cyclohexane <0.001
Ethylbenzene <0.001
Isopropylbenzene 0.251
Methylcyclohexane <0.001
m-Xylene/p-Xylene <0.001
n-Hexane <0.001
n-Nonane <0.001
n-Pentane 0.06
n-Propylbenzene 0.0501
o-Xylene <0.001
Propylene 0.991
Styrene 0.272
Toluene <0.001
Human Health Risk Assessment
• “Screening” Risk Estimates Using EPA methods – EPA Reference Concentrations (RfCs), inhalation unit risks, and other health-
based guidelines when RfCs or cancer potency estimates not available
– Exposure scenarios
– Chronic and subchronic assessments of risk for nearby residents
• Quantitative Risk Assessment – Non Cancer (Systemic): Hazard Index
• Ratio of estimated exposure to RfC and/or health-based guidance level
• Index sums potential effects of multiple chemicals
• Are these greater than 1?
– Cancer: Lifetime Excess Cancer Risk, multiple chemicals • Are risks greater than 1 in a million ?
• Are risks greater than 1 in 10,000 ?
Exposed Populations
Two Populations
– Residents living within the PUD at residence not near well pad.
– Residents living within the PUD at a residence near well pad.
– Divided exposures into “near” and “far” from well pads based on citizen
odor complaints • Residents living within ½ mile of a well pad were considered as living near a well pad
based on odor complaints filed with COGCC in July and August 2010 (COGCC 2010).
• Self reported eye irritation, breathing problems, coughing, and pneumonia
• COGCC confirmed the odor complaints
Exposure Scenarios
Site Specific Durations: Based on Operator’s Information
– Subchronic: Short-term, “high exposure” well completion scenario,
resident living near two well pads under development, 20 months total
• 2 weeks to complete each well
• 20 wells per pad
• 2 well pads
– Chronic: 30 year exposures to well production emissions/natural gas
area emissions, noncancer and cancer risk estimates • 5 years of well development (drilling and completions)
• 20 to 30 years of production
EPA Defaults for “reasonable maximum exposure”:
Frequency: 350 days/per year, 24 hours/day
Non-Cancer Hazard Indices by Duration
of Exposure and Distance from Source
0.4 0.2
1
5
0
1
2
3
4
5
6
Chronic, Far Subchronic, Far Chronic, Near Subchronic, Near
Hazard
In
dex
Exposure Scenario
Level above which health
effects may occur
Non-Cancer Hazard Indices by Health Endpoint:
Near Wells, 20 Month Exposure Scenario
4
2
3
1
0
1
2
3
4
5
Neurological Effects Respiratory Effects Hematogical Effects Developmental Effects
Hazard
In
dex
End Points
Excess Lifetime Cancer Risks
6 10
0
10
20
30
40
50
60
70
80
90
100
110
Residents > 1/2 mile Residents ≤ 1/2 mile
Excess C
an
cer
Ris
k p
er
on
e M
illio
n In
div
idu
als
Exposure Scenario
Summary of Excess Lifetime Cancer Risk
EPA's Target of 1 in a
million
Risk where EPA
requires remediation
Risk Assessment Uncertainties and
Limitations • Small sample size: limited data exists on emission
around well completion sites
• Non-methane pollutant emissions appear to vary substantially by field type, number of well heads, completion process, and controls in place
• Limited suite of volatile compounds explored, but not other primary or secondary pollutants (e.g., aldehydes, diesel exhaust, ozone, PM, etc.)
• These data do not tell us how far is far enough nor how close is too close to well development sites
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.
Thousands of Rural Coloradoans Live in the
Vicinity of Natural Gas Operations
Retrospective Cohort Study
Explore the association between a mother’s
proximity to natural gas development while
pregnant and birth outcomes using:
• Birth certificate data
• Birth defects surveillance data
• Geocoded well locations
• Information on spud dates and gas production
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
Located 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
Measured the distance of each gas well from the
Mother’s home
Inverse Distance Weighted Count
• Calculated the inverse distance weight for each
well
• Summed 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.
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)
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)
Inverse Distance
Weighted Well Counta
0 Wells
within 10
Miles
Low Medium High Cochran-Armitage
Trend Test p-
valued
Live Births (N) 66,626 19,214 19.209 19,793
CHDs
Cases (N) 887 281 300 355
Crude OR 1 1.1 1.2 1.3 < 0.0001
Adjusted OR (95% CI)b 1.1 (0.93, 1.3) 1.2 (1.0, 1.3) 1.3 (1.2, 1.5)
NTDs
Cases (N) 27 6 7 19
Crude OR 1 0.77 0.90 2.4 0.01
Adjusted OR (95% CI)c 0.65 (0.25, 1.7) 0.80 (0.34, 1.9) 2.0 (1.0, 3.9)
Oral Clefts
Cases (N) 139 31 41 40
Crude OR 1 0.77 1 0.97 0.9
Adjusted OR (95% CI)b 0.65 (0.43, 0.98) 0.89 (0.61, 1.3) 0.82 (0.55, 1.2) aLow = 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. bAdjusted for maternal age, ethnicity, smoking, alcohol use, education, and elevation of residence, as well as infant parity and gender. cAdjusted only
for residence elevation because of low numbers. dCochran-Armitage trend test performed as two tailed test on unadjusted logistic regression.
Inverse Distance Weighted Well Counta
0 Wells within 10
Miles
Low Medium High Cochran-Armitage Trend
Test p-valued Preterm Birth
Live Births (N) 65,506 18,884 18,854 19,384
Cases (N) 4,849 1,358 1,289 1,274
Crude OR 1 0.97 0.92 0.88 < 0.0001
Adjusted OR (95% CI)b 0.96 (0.89, 1.0) 0.93 (0.87, 1.0) 0.91 (0.85, 0.98)
Term Low Birth Weight
Full Term Live Births
(N)
60,653 17,525 17,565 18,104
Cases (N) 2,287 525 471 432
Crude OR 1 0.79 0.70 0.62 < 0.0001
Adjusted OR (95% CI)b 1.0 (0.9, 1.1) 0.86 (0.77, 0.95) 0.9 (0.8, 1)
Mean difference in birth weight (grams)c
0 5 (-2.2, 13) 24 (17, 31) 22 (15, 29)
aLow = 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 .
bAdjusted for maternal age, ethnicity, smoking, alcohol use, education, and elevation of residence, as well as infant parity and gender. cAdjusted
for maternal age, ethnicity, smoking, alcohol use, education, and elevation of residence, as well as infant parity, gender, and gestational age. dCochran-Armitage trend test performed as two tailed test on unadjusted logistic regression.
Limitations
• Undercounting of Birth Defect Outcomes
• Obscuring of Outcomes by Grouping
• Information on some potentially important
confounders not available (i.e. maternal folate
consumption)
• Exposure Misclassification
– Maternal residence during the first trimester
– Specific activities occurring at well sites
Conclusions
• Short term exposures to air emissions from well sites are potentially in the range of health concern for nearby residents
– Emissions include mutagens and teratogens (e.g. benzene, xylenes, and toluene)
– Health concerns include neurological, respiratory, and developmental effects.
– Much is dependent on distance, local meteorology and topography
• 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 natural gas (and oil) development using unconventional methods.
Acknowledgements • CSPH Colleagues: Roxana Witter, John Adgate, Lee Newman, Ruixen Guo,
David Savitz, Brown University
• Garfield County Public Health: Jim Rada, Paul Reaser, and GC BOCC funding
• 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.
• Additional funding from the Colorado School of Public Health Department of Environmental and Occupational Health
Garfield County Emissions Inventory
Prepared for Garfield County
Prepared by the Colorado Department of Public Health and Environment
Air Pollution Control Division
October 2009
Inverse Distance Weighted Well Counta 0 Wells within 10 Miles Low Medium High
Conotruncal Defects
Cases (N) 40 14 13 15
Adjusted OR (95% CI)c 1 1.1 (0.57, 2.2) 1.1 (0.55, 2.0) 1.2 (0.6, 2.2)
Ventricular Septal Defects
Cases (N) 210 68 59 84
Adjusted OR (95% CI)b 1 1.3 (0.96, 1.8) 1.1 (0.81, 1.5) 1.5 (1.1, 2.1)
Endocardial Cushion and Mitrovalve Defects
Cases (N) 39 14 12 12
Adjusted OR (95% CI)c 0.81 (0.42, 1.6) 0.80 (0.41, 1.5) 0.67 (0.33, 1.32)
Pulmonary Artery and Valve Defects
Cases (N) 137 52 62 66
Adjusted OR (95% CI)b 1 1.3 (0.89, 1.8) 1.5 (1.1, 2,1) 1.6 (1.1, 2,2)
Tricuspid Valve Defects
Cases (N) 9 5 8 8
Adjusted OR (95% CI)c 1 2.6 (0.75, 9.1) 3.9 (1.3, 11) 4.2 (1.3, 13)
Aortic Artery and Valve Defects
Cases (N) 75 22 21 24
Adjusted OR (95% CI)b 1 1.1 (0.68, 1.9) 1.0 (0.62, 1.8) 1.2 (0.73, 2.1)
Patent Ductus Arteriosis
Cases (N) 59 18 17 15
Adjusted OR (95% CI)b 1 1.0 (0.56, 1.8) 0.96 (0.55, 1.7) 0.83 (0.44, 1.5)
aLow = 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. bAdjusted for maternal age, ethnicity, smoking, alcohol use, education, and elevation of residence, as well as infant parity and gender. cAdjusted only for residence elevation of because of low numbers.