An Important First Study is Published
Corporations that engage in mining and
manufacturing are extremely fortunate that Americans cannot be
randomly assigned to places of residence. This prevents researchers
from doing true experiments--that is, randomly assigning people to experimental and control groups to study the effects of air,
water and soil pollution on public health. As a result, when
epidemiologists, who study the spatial distribution of health and illness, find evidence of illness concentrated in the
vicinity of sources of industrial pollution, it its always possible
for corporations to claim that something else—known or unknown—is
responsible. Correlation does not mean causation.
On Wednesday, what is to my knowledge
the largest scientific study relating proximity to natural gas wells to human health, conducted by a team led by Peter Rabinowitz of the
Yale School of Medicine, was released online by the peer-reviewed
journal Environmental Health Perspectives.
Previous evidence of an association between natural gas drilling and
illness had come either from case studies or convenience—that is,
nonrandom—samples.
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| Photo by Ruhrfisch |
The study was done in Washington County, south of Pittsburgh, which had 624 active
natural gas wells, 95% of which utilized hydraulic fracturing. A set
of 38 contiguous rural communities were selected for study, to avoid
urban areas unlikely to have ground-fed wells. Within these
communities, 760 geographic points were randomly chosen and the
nearest residence was selected for study. Some sites were excluded
due to duplication, because there were no homes nearby, or because
the house did not have a ground-fed well. This left 255 eligible
households, 180 (71%) of which agreed to participate. Forty-seven
households refused to participate, and researchers were unable to
contact residents of the remaining homes.
Participants were interviewed in their homes in the summer of 2012 by trained survey
researchers who followed a prepared script. The survey made no
reference to natural gas drilling. Researchers were unaware of the
home's proximity to the nearest gas well. (Of course, this
precaution failed if a drilling rig was visible from the front
porch.) An adult member of the household was asked questions
assessing the health status and symptoms of each member of the
household—a total of 492 people. Participants were paid $25.
Participating households were divided into those within 1 kilometer
(.6 miles) of a natural gas drilling site, those between 1 and 2 km,
and those more than 2 km from the nearest site.
Respondents were
asked about six types of health problems: dermal, upper respiratory,
lower respiratory, gastrointestinal, neurological and cardiovascular.
The following variables were statistically controlled: age, gender,
education, occupation, the presence of smokers or pets in the home,
and awareness of nearby environmental hazards. Statistically significant results were obtained in two of the six health areas,
dermal and upper respiratory.
- Upper respiratory symptoms, such as coughing, itchy eyes and nosebleeds, were reported by 39% of those living within a km of a drilling site but only 18% of those who lived more than 2 km away. Both the near and intermediate groups reported significantly more upper respiratory symptoms than the far group.
- The number of people suffering from dermal problems was smaller, but the association was stronger. Thirteen percent of those living nearest to a gas well suffered from skin problems, such as rashes, itching and burning, but only 3% of those living the farthest away. The near group reported significantly more dermal symptoms than the far group.
The authors do not
claim that their data show a causal relationship between drilling and
health problems. However, they speculate that, if natural gas
drilling is responsible for these skin and respiratory issues, it could have happened through three pathways: (1) pollution of ground
water, including the water in their wells; (2) air pollution from the
drilling site; and (3) stress due proximity to a drilling site.
Noise is a particularly potent stressor. Supporting the stress hypothesis is the fact that those who were aware of nearby environmental
hazards reported more skin and respiratory symptoms, although the
relationship between proximity and symptoms was still significant
when the effect of awareness was statistically removed.
Whenever a
relationship between industrial pollution and illness is found, the
most likely alternative explanation is the indirect involvement of
social class. Locations that are close to sources of pollution are
usually undesirable places to live. Property values are lower and
people living nearby have lower incomes. We know that, for a variety
of reasons, lower income Americans are in poorer health. However,
this explanation is weakened somewhat by the fact that almost all the
natural gas wells in Washington County were drilled within the last
5-6 years. This allowed less time for migration to occur and for
pockets of poverty to form around the drilling sites.
Because the
researchers relied on self-report data, it's possible that people
living close to drilling sites exaggerated their symptoms—although
they might also have had reasons to minimize them. The fact that the
results were still strong when awareness of environmental hazards was
controlled argues against this interpretation. Future researchers
should consider conducting actual medical examinations of the
participants. This would of course be much more expensive and
logistically challenging.
The 71% completion
rate is well above average for surveys. However, it might be argued
that people experiencing illnesses that they attributed to local
drilling were more anxious to tell their story, and that this
contributed to an overestimation of the percentage with health
problems. However, the refusal rate did not vary significantly with
distance from the nearest drilling site.
The health problems
detected in the study were among the least serious included in the
survey. Since most of those surveyed had only been living near a gas
well for a short time, the authors say they were not surprised that
diseases with longer latencies, such as heart conditions or cancers,
were not yet associated with proximity to a drilling site.
The research was
supported by a grant from Pittsburgh's Heinz Foundation, along with
four other non-profit sources. The authors thanked the Southwest Pennsylvania Environmental Health Project for “assistance with the community survey.” They conclude by calling for further research,
including “longitudinal assessment of the health of individuals
living in proximity to natural gas drilling activities, medical
confirmation of health conditions, and more precise assessment of
contiminant exposures.”
To be continued in Part 2.
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