Pig Odors Raise Human Blood Pressure

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Living near an industrial-scale hog farm could be hazardous to your health.

Just 10 minutes of exposure to smells from swine operations in North Carolina was enough to raise the blood pressure of people who lived nearby, found a new study.

North Carolina’s swine farms lie disproportionately close to low-income, non-white communities, causing the farms to be fingered by some advocates as a classic example of environmental racism, said lead author Steve Wing, an epidemiologist at the University of North Carolina, Chapel Hill.

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To study the health effects of eastern North Carolina’s hog farms, Wing and colleagues partnered with community-based organizations, which helped them connect with residents who were skeptical of the researchers’ intentions.

“Most participants were African-American,” Wing said at a recent meeting of the Council for the Advancement of Science in Raleigh. “People were peeking out to see why a white person was in the neighborhood. There was a lot of distrust of scientists. We never would have been able to conduct this study without our community partners.”

For about two weeks, 101 adults who lived in 16 neighborhoods within 1.5 miles of industrial swine farms sat outside their homes twice a day for 10 minutes each time. Afterwards, they recorded the strength of the ambient smell on a scale from zero to eight and they took blood-pressure measurements. At the same time, the researchers recorded levels of various pollutants in the air.

For every extra point reported on the odor scale, participants’ blood pressure went up by small but incremental amounts, the researchers reported in the journal Environmental Health Perspectives. Compared to times when there was no smell detected, level-eight odors were associated with a two-mmHg rise in diastolic blood pressure (the bottom number). And higher levels of hydrogen sulfide gas were associated with a three-mmHg rise in systolic blood pressure (the top number).

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Previous studies have linked bad odors from swine farms with higher levels of stress in nearby residents as well as with irritation to eyes, noses and throats. The new findings, Wing said, are “a sign that the environment is related not only to our perception, but to our physiology.”

And even though measured blood-pressure increases were small, every little bit adds up.

“This region is known as a stroke belt,” Wing said. “We don’t need additional environmental exposures leading to additional blood pressure increases.”

IMAGE: Pigs in CAFO (concentrated animal feed operation) (CREDIT: U.S. Geological Survey)

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