DES MOINES, Iowa (AP) -- Parts of downtown Des Moines have been so transformed in the past decade by new apartments, trendy shops and microbreweries, it's sometimes hard to reconcile the present with the not-so-distant past.
But one strong reminder of the city's heritage remains: the stench. A pungent smell of rancid meat regularly wafts through all the shiny new development, a reminder of the region's less polished history as a pork processing center.
"You can't escape it," said Brandon Brown, president of the Des Moines Downtown Neighborhood Association, calling it "very frustrating."
Many cities eager for new investment and vitality have welcomed urban housing and entertainment venues into older sections of town that housed grittier industries, only to be stumped by what happens when someone like Brown, who moved into an upscale downtown apartment, actually wants to enjoy a latte or meal at an outdoor patio.
After decades of downplaying or simply ignoring the problem, Des Moines officials recently began a comprehensive study that will lead to tighter regulations on some smelly manufacturing plants to finally clear the air.
Similar difficulties are cropping up in other cities with smelly businesses, especially rendering plants that are common in agricultural regions and even some big cities. Angry residents are deluging officials with complaints and filing lawsuits, while some leading companies are installing new equipment, making payments to neighbors or even closing down.
No one tracks such disputes, but Iowa State University professor Jacek Koziel, who studies air quality and livestock odors, said he thinks the conflicts may be increasing. Sometimes, as in Des Moines, it's because more noses are nearer the bad smells, but in other spots, it's that residents are simply pushing harder for changes.
"It's very common in this juncture of animal agriculture in general and meat packing plants or feed processing plants," Koziel said. "It's very tough. For us engineers, we know there are technologies to minimize the impact but then come all the fiscal realities of doing that."
In Des Moines, residents and workers have for decades complained about the smells from an industrial area little more than a mile from downtown, describing the scent as putrid or akin to animal waste. Brown takes a more charitable view, labeling the smell "yeasty."
People typically blame two companies: pork processor Pine Ridge Farms and rendering plant Darling Ingredients. Although the city created an odor board and odor hotline, its efforts were ineffective and largely abandoned until recently, when people who moved into expensive apartments that had replaced warehouses and scrap yards complained of nauseating smells periodically settling over their neighborhoods.
City officials agree there's a problem, but say they need more data before deciding what to do.
"You've got to know what is the truth that's out there, and then make the plans work for each of the industries," said SuAnn Donovan, deputy director of Des Moines' Neighborhood Services Department. The new study will take air samples and figure out a baseline for air quality.
Iowa is an agricultural powerhouse and Donovan is quick to note that the city wants to work with Pine Ridge, Darling and other companies.
Darling didn't respond to an inquiry about its Des Moines operations.
Pine Ridge Farms is owned by meat industry giant Smithfield, which said in a statement that its pork plant, which employs about 1,000 people, opened in 1937 and slaughters about 4,000 hogs daily. As more people moved nearby, the company said, it had invested millions of dollars on new technology, such as air treatment equipment, to reduce odors.
"We also follow a rigorous daily cleaning schedule during and after each production run," the statement said. "At the end of each week, we perform a top-to-bottom deep cleaning to keep odor to a minimum."
Even with efforts to reduce smells, rendering is an especially pungent business. The plants use heat, centrifuges and other techniques to convert waste animal tissue into fats and proteins for many uses, including as animal feed, fertilizer and cosmetics. There are more than 200 plants in the U.S. and Canada, according to recent estimates.
In Fresno, California, a citizens group filed a lawsuit against a Darling rendering plant that produced a stench so strong that residents complained of health problems. Last year, the company agreed to close the plant. Another rendering plant near the Sacramento suburb of Rancho Cordova that had operated for more than 50 years also opted to close after concluding it couldn't coexist with new nearby housing.
Rendering plants in an industrial area of Los Angeles have been ordered to abide by strict new rules. And in Denver, where new urban development has been especially extensive, there have been sharp clashes between new residents and old industries.
"People moving in are savvy and they're not afraid to complain," said Greg Thomas, the city's director of environmental quality.
Residents in South St. Paul, Minnesota, filed a class action lawsuit over fumes from a rendering plant, and neighbors received up to $1,000 payments as part of a $750,000 settlement.
Still, though, smells of rancid meat remain.
"The lawsuit didn't seem to make a difference," said Chris Robinson, who lives less than a mile from the plant. "Just last night, my husband couldn't sit out on the deck. It's still really bad."
Brown, of Des Moines, said with new outdoor projects underway, from a soccer stadium to a whitewater rafting course, the city has little option but to clear the air.
"You don't want the smell to contaminate the experience," Brown said.