We put up with a lot of crap—literally.

Last year, at least 4.7 billion gallons of hog manure in the U.S. came from one company, Smithfield foods, the nation's leading pork producer. The feces load will rise if U.S. regulators green-light a proposed merger that would bring the firm under the auspices of a China-based company. That increase could also promote the growth of antibiotic-resistant bacteria and increase health risks for hog farm workers and the communities living around them.

Under a proposed multibillion-dollar deal, Hong Kong–based Shuanghui International Holdings would buy Virginia-based Smithfield Foods. The stated purpose of the merger, the companies say, is to efficiently increase pork production. If the deal goes as planned, Smithfield will ultimately export more meat to China, where the appetite for pork continues to climb upward even as Americans buy less of it. But with that expected production boost comes an uptick in hog feces left in the U.S.—and subsequent health and environmental risks.

The impacts of industrial-scale hog production like Smithfield’s have played out in the courts and medical journals for decades—largely from the way the firms handle the waste. The majority of hog feces from Smithfield sits in earthen lagoons where it naturally ages for six to 12 months before the slurry is then sprayed on agricultural fields as fertilizer.

Studies on communities living around such farms have indicated individuals exposed to the odors and emissions from around the lagoons have more respiratory complaints and increased asthma symptoms. Moreover, when hogs are raised in crowded environments in industrial-scale farms they require greater quantities of antibiotics (pdf) to promote growth and compensate for unsanitary conditions. That antibiotic use is linked with increased antibiotic resistance in humans.

Indeed, researchers in particular worry that antibiotic-laden hog manure can seep into the water and air as well as bodies of people surrounding such farms, with subtle implications both for health and for the spread of antibiotic resistance. In one study high concentrations of antibiotic and multidrug-resistant bacteria were detected inside and downwind of an industrial-size swine production facility, but not upwind. Other work linked antimicrobial-resistant bacteria in groundwater and private drinking wells to swine facilities located upstream. This month more than 580 residents of eastern North Carolina—the state with the most Smithfield hogs—filed complaints against the company, charging that the pollution from that hog production deprives them of the use and enjoyment of their property.

Smithfield, which operates across 12 states, brought 15.8 million hogs to market in fiscal 2012—and each hog, according to the company, produced an average of 1,100 to 1,300 liters of manure during its lifetime (including the water used to push the pig feces into pits below their pens). Smithfield says there will be no changes to the company’s production practices or its sustainability plan. “It will be the same old Smithfield—only better,” Larry Pope, company president and chief executive officer, told the Senate Committee on Agriculture, Nutrition and Forestry on July 10. “Without this opportunity to grow outside of the United States there is no opportunity for U.S. pork producers to expand.”

With the deal, Shuanghui is getting something more important than more meat, charges Usha Haley, professor of management and expert on emerging markets at West Virginia University. The company would also be acquiring the clout of Smithfield’s name and knowledge of U.S. production practices and technology, she says. The merger would then help fuel China’s shift toward even more hog farms that adopt Smithfield’s vertically integrated processes—namely, industrial-size farms that raise pigs in close quarters and dispose of their waste through the lagoon-and-spray method, thereby threatening to reproduce the same health and antibiotic-resistance issues in China.

In fact, China’s State Council in 2011 said that it planned to put $385 million a year toward construction of large-scale hog farms for five years, moving toward consolidation. Already, China is shutting down backyard pig farms in favor of such operations, said Daniel Slane, commissioner of the U.S.–China Economic and Security Review Commission, in testimony to the Senate committee.

Critics of the environmental and health implications of the merger say the deal will also create operations that would be far less transparent for communities around the farms. Right now, Smithfield is a publicly traded company so it puts out annual reports that give insight into its practices as required by the U.S. Securities and Exchange Commission. “After the acquisition, Smithfield will cease to be publicly traded, and information on operations will come through Chinese reports,” Haley says. Although SEC filings would no longer be required, communities could still learn something about its waste management and production practices because the company would need to provide information for various kinds of environmental permits, says Tarah Heinzen, an attorney with the Environmental Integrity Project. Smithfield declined to comment for this article.

Food safety issues, alongside concerns about U.S. competitiveness, prompted Committee Chair Debbie Stabenow (D–Mich.) at the hearing to press Smithfield’s CEO, asking if pork products from China—even repackaged meat from the U.S. that would be reimported back to the country—could eventually end up on American dinner plates. In the past China has had to cope with rampant food safety violations, and Shuanghui has committed infractions, including one incident in which customers reportedly became ill after eating maggot-infested sausages. “Chinese product cannot be imported into the United States today,” and the two companies are not trying to change that, Pope says. “There is no discussion about that.”

The proposed Smithfield merger is being reviewed by the U.S. inter-agency body called the Committee on Foreign Investment in the United States. For now, hog farming communities are holding their collective breath.