Josh Harkinson

Josh Harkinson

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Born in Texas and based in San Francisco, Josh covers tech, labor, drug policy, and the environment. PGP public key.

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Scientists Can Predict Your City's Obesity Rate by Analyzing Its Sewage

| Tue Mar. 31, 2015 6:10 AM EDT
The sewage of fat cities like Little Rock and Toledo is easy to distinguish from that of skinny ones like Denver and San Diego.

If someone were to ask you what distinguishes skinny cities from fat ones, you might think of the prevalence of fast-food joints, the average length of automobile commutes, or the relative abundance of parks and jogging trails. But there's also another, more underground factor: their sewage.

Researchers with the University of Wisconsin-Milwaukee collected raw sewage samples from the intakes of municipal wastewater treatment plants in 71 cities around the country. Their results, published last month in mBio, the American Society for Microbiology's open-access journal, showed that the microbial content of that sewage predicted each city's relative obesity with 81 to 89 percent accuracy.

The finding actually isn't all that surprising, says lead author Ryan Newton, a visiting professor at UWM's School of Freshwater Sciences. Other studies have shown that bacterial imbalances in your intestines can lead to metabolic syndrome, obesity, and diabetes. Newton's study, however, is the first to demonstrate that those microbial differences also play out across entire populations, even after our poop gets flushed, mixed together, and sent through miles of pipes.

The UWM study was enabled by computing advances that have allowed scientists to rapidly sequence microbial populations and look for patterns in the results. Other researchers are using similar techniques to look for correlations between gut bacteria and a wide range of health conditions.

Scientists hope other data derived from sewage could help predict epidemics and track public health trends.

Newton isn't the only scientist who sees sewage as a promising place for data dives. The Massachusetts Institute of Technology's Underworlds project, which began in January, will study sewage for the presence of viruses such as influenza and polio; bacterial pathogens that cause cholera typhoid fever, and other diseases; and biochemical molecules ranging from antibiotics to illegal drugs like cocaine and methamphetamine. Scientists hope the resulting data could help predict epidemics and track other public health trends within particular neighborhoods. 

As scientists gain a better understanding of the interplay between microbes and human health, they may eventually be able to look at municipal sewage to figure out which communities would be the best to target with public health campaigns designed to, say, get people to eat less sugar or more vegetables.

And just as important, sequencing sewage could eliminate the thorny problem of doing public health surveys. Unlike people, your poop can't lie about what you had to eat.

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Illegal Pot Farms Are Literally Sucking California Salmon Streams Dry

| Fri Mar. 27, 2015 4:06 PM EDT
Outlet Creek watershed in Northern California's Mendocino County. Scott Bauer

Northern California pot farmers are using up all of the water that normally supports key populations of the region's federally protected salmon and steelhead trout.

That, at least, is the conclusion of a new study, published last week in the journal PLOS One, that examined four California watersheds where salmon and trout are known to spawn. In the three watersheds with intensive pot cultivation, illegal marijuana farms literally sucked up all of the water during the streams' summer low-flow period, leaving nothing to support the fish.

"The current scale of marijuana cultivation in Northern California could be catastrophic for aquatic species."

Author Scott Bauer, a biologist with the state department of fish and wildlife, estimated the size and location of outdoor and greenhouse pot farms by looking at Google Earth images and accompanying drug enforcement officers on raids. He did not include "indoor" grows—marijuana grown under lamps in buildings.

After visiting 32 marijuana greenhouses in eight locations and averaging the results, Bauer extrapolated his findings to all greenhouses in the study area—virtually nothing else is grown in greenhouses in this part of the country. The sites contained marijuana plants at a density of about one per square meter, with each plant (taking waste and other factors into account) using about six gallons of water a day. Overall, he calculated, pot operations within the study yielded 112,000 plants, and consumed 673,000 gallons of water every day.

And that is water the area's fish badly need. The Coho salmon population is listed as threatened under both state and federal Endangered Species Acts, and is designated as a key population to maintain or improve as part of the state's recovery plan. 

Bauer collected his data last year, at a time when California's drought had already become its worst in more than 1,200 years. When I spoke to him at the time, he told me that pot farming had surpassed logging and development to become the single biggest threat to the area's salmon. Now that that the drought is expected to extend into a fourth year, the same streams could run dry again this summer, and remain so for an even longer period of time.

Overall, the outdoor and greenhouse grows consume more than 60 million gallons of water a day during the growing season—50 percent more than is used by all the residents of San Francisco.

"Clearly, water demands for the existing level of marijuana cultivation in many Northern California watersheds are unsustainable and are likely contributing to the decline of sensitive aquatic species in the region," Bauer's study concludes. "Given the specter of climate change"—and the attendant rise of megadroughts—"the current scale of marijuana cultivation in Northern California could be catastrophic for aquatic species."

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