Hog Farm Pollution 

The 10 million hogs that now populate North Carolina's coastal region produce 19 million tons of waste every year (52,000 tons daily) that must be reused or disposed of. The state's hog production has increased over 270% since 1990, averaging increases close to 40% each year. 

Scientists have now identified several critical ways in which current methods of handling hog waste have severe impacts on nearby communities and the environment. Open-air waste lagoons and sprayfields (techniques used to manage waste) make a significant contribution to nitrogen pollution, groundwater contamination, and horrible odors that assail neighbors. 

Preliminary studies have found that hog waste poses human health threats. The presence of pathogens (disease-causing organisms) in hog waste applied to land, antibiotic resistance, dust, and heavy metals in lagoon sludge are potential concerns. Despite the known and potential environmental problems associated with hog factories in North Carolina, hog production operations are insufficiently monitored. In fact, the extent of leakage of hog waste from lagoons into groundwater and the release of nitrogen into the air from hog waste are not inspected, measured, or monitored at all. Consider these problems associated with hog factories: 

Nitrogen and Phosphorus Pollution in Valuable Coastal Waters

What is nitrogen and phosphorus pollution? What does it do?
Nitrogen and phosphorus serve as fertilizers but, in excess quantities, can pollute water and air. When nitrogen and phosphorus get in the wrong place at high concentrations, they stimulate algal growth which leads to "low dissolved oxygen levels" (i.e., robs the water of oxygen). Low dissolved oxygen can kill fish and other aquatic life.

Overenrichment of nitrogen in coastal waters in North Carolina from a wide variety of sources (municipal waste water treatment plants, urban runoff, agricultural runoff, as well as animal waste runoff) has resulted in algal blooms, fish kills, and shellfish diseases (DWQ, 1996; DWQ, 1995). Pfiesteria, a toxic microorganism that can kill fish, has been associated with nitrogen and phosphorus-polluted waters, although current scientific evidence is still inconclusive.

How do hog factories contribute to nitrogen pollution?
Hog waste contains large amounts of nitrogen and phosphorus that, during the treatment process, are released into the air, leak from waste lagoons into the ground, and drain and leach from fields into rivers, streams, and estuaries. Hogs in North Carolina generate over 640,000 pounds of nitrogen per day or 233 million pounds per year. They generate over 213,000 pounds of phosphorus per day or 77.9 million pounds of phosphorus per year (North Carolina State University, 1997) . The 10 million hogs concentrated in eastern North Carolina are producing far too much nitrogen, more than can be productively used by crops (Lander, et al, 1998).

The majority of this nitrogen ends up in the air as ammonia, a highly reactive and biologically-available form of nitrogen, which then rains back down onto land and waters. Ammonia is released from hog waste throughout the disposal process -- first directly from the hog house, then from the open-air waste lagoon, and finally by being shot into the air on to the sprayfield. 

Nitrogen on the ground as ammonia can quickly convert to nitrates, which can drain from fields into waterways if overapplied or applied when plant needs are low. Nitrate is highly soluble and moves quickly through soil and groundwater. Drainage ditches crisscrossing fields in the flat, sandy soils of rural North Carolina act as conduits to rivers and streams for hog waste which has seeped into shallow groundwater below sprayfields, especially after the frequent rains which are common to the coastal region. If improperly applied to fields that are wet or already saturated with nitrogen, runoff and leaching are far more likely to send the extra nutrients into waterways. 

Nutrient pollution can occur when waste is applied too close to ditches or streams. Poorly managed hog factories may directly pour hog waste into rivers and streams. For example, in 1995, a large waste lagoon burst and dumped 22 million gallons of hog waste into the New River. (In contrast, the Exxon Valdez disaster of 1989 spilled 11 million gallons of oil into Alaska's Prince William Sound.) 

Waste lagoons, even with clay liners, allow waste to leach into the ground below the lagoon. In fact, specifications allow leakage through the clay liners at a rate up to 0.036 inches per day. This does not sound like a large amount. However, if one considers that lagoons are often acres in size and leaking day after day, it adds up to a huge volume. At the maximum allowable rate, a three acre lagoon could legally leak more than a million gallons a year. Given eastern North Carolina's shallow depth of groundwater, waste leaked from lagoons gets into the groundwater. No one knows how much is leaking from the nearly 4,000 lagoons in North Carolina because there is no requirement that hog factories monitor leakage. Groundwater contaminated with nitrogen in turn threatens coastal surface waters, since groundwater supplies water to rivers, streams, and estuaries. In fact, approximately 70% of the water flow in the rivers of eastern North Carolina depends on groundwater (Gilliam et al, 1997).

Contamination of Groundwater Drinking Wells

Nitrates from hog waste can contaminate drinking wells. Monitoring has shown that a number of shallow groundwater drinking wells located down gradient of hog and chicken farms contain significant concentrations of nitrate. Recent state analyses found 10% of the wells near large hog and chicken operations have abnormally high levels of nitrates in the drinking water (Rudo, 1998). 

The concentration of nitrates in groundwater below sprayfields used by hog and chicken operations has been measured at 10 to 50 parts per million (Showers, 1998; Crouse, 1998). The public health standard is 10 parts per million. High levels of nitrates are dangerous to humans, especially pregnant women and babies, and are associated with a number of public health concerns such as abortions and "blue baby syndrome" (a disease affecting the blood's ability to absorb oxygen).

Concerns are also being expressed about phosphorus building up in agricultural soils. Animal waste applied to land typically contains levels of phosphorus far in excess of crop needs. Once thought to be safely locked in soils, phosphorus loss in surface runoff is now being reported (Sharpley et al, 1998). Movement of this phosphorus into surface streams can extend the range of harmful algal blooms from nitrogen-limited estuaries into phosphorus-limited freshwater streams. 

Air Pollution from Nitrogen Ammonia

Hogs in North Carolina release over 167 million pounds or almost 69 tons of nitrogen into the air per year, or over 458,000 pounds per day (based upon 1997 hog population estimate and emission factors from Battye, et al., 1994). Blown down wind, this ammonia nitrogen subsequently rains down on sensitive rivers, estuaries, and coastal waters in North Carolina, possibly impacting waters as far away as the Chesapeake Bay (Dennis, 1997). Studies in the North Carolina region where hog factories are clustered show that ammonia measured in rain has doubled in the last decade (Cornelius, 1997). Current hog waste practices discharge more airborne ammonia nitrogen than all other state livestock and industrial sources combined (Aneja, 1997). This is true despite the fact that North Carolina is #1 in the country in turkey production and #4 in broilers (chickens).

Results from ongoing research on the fate and transport (where it lands) of the atmospheric ammonia nitrogen emissions from hog operations are not yet available. However, preliminary analysis indicates that hog factories pour more nitrogen pollution through the air alone into eastern North Carolina estuaries than all of the discharges from municipal waste water treatment plants and industrial factories combined (Rudek, 1997). Agricultural nitrogen emissions in 1995 were estimated to load more than 2 million pounds of nitrogen per year to the Neuse River Estuary alone. This is comparable to the estimated 2.1 million pounds of nitrogen per year delivered to the Neuse estuary from municipal wastewater treatment plants in 1995. 

Using waste lagoons and sprayfields promotes the atmospheric dumping of ammonia nitrogen. Neither North Carolina nor the U.S. Environmental Protection Agency currently regulates any air emissions from hog operations.

Odor and Other Air-Related Impacts to Public Health and Quality of Life

Neighboring communities suffer from horrible odors emitted by hog factories. The truth of this is best told by the people who live near hog factories. See The Human Factor on this website. 

Listen to Karen Priest, community activist and working mother of two, whose Bladen County home is surrounded by hog factories. 

"I feel like I'm raising my kids in one of those third world countries that we see some celebrity on TV trying to raise money for because of the sewage running through their village. It's been nearly four years since I opened the windows of my own home. 

What memories will my children take with them when they leave home? Will they only remember home being the place that smelled like hog waste? Will they only remember the birthday party when a friend asked if she could call her mother to come get her because she couldn't stand the smell? Will these be my children's memories of home?" 6/11/98 

Recent studies show that odor and associated air pollution from hog factories are now being linked to human health effects. The National Institute for Occupational Safety and Health has issued warnings for several years to workers in animal confinement operations about job-related asthma and the threat of death from manure-pit gases if ventilation systems fail to work adequately. In a review of air-related illnesses in workers at confined hog operations, it was found that 11% had asthma-like symptoms, one-third had a flu-like illness called organic dust toxic syndrome, more than half suffered upper-airway inflammation, and as many as 70% had some form of bronchitis (Donham and Thu, 1995). (There have been no manure pit gas-related deaths reported in North Carolina, and no published research on the other air-related illnesses.) Hog factory workers can get acute symptoms after as little as two hours a day exposure in a confinement atmosphere. Asthma and other respiratory conditions show up more after six years of working in animal confined facilities. For workers who already have asthma or allergies, the most severe symptoms are more likely to develop (Donham and Thu, 1995). 

Limited studies have been conducted which also have found statistically significant increases in acute or chronic respiratory problems associated with residents near large-scale hog facilities. In Iowa, a study found neighbors of hog facilities had respiratory problems similar to those of workers in hog confinement operations (Donham, 1998). Scientists have not yet proved that gases and dust from hog factories directly cause respiratory illness, but the complaints and occurrences of the asthma- and bronchitis-like symptoms are reported in these studies. 

Other research has found increased psychological stress in residents near hog factories that is related to frequent exposure to intense hog odors. A study of North Carolina residents who had lived by hog factories an average of five years reported significantly more tension, depression, anger, and fatigue than residents not exposed to hog odor at home (Schiffman, 1998).

Dust from large-scale animal operations is a potential health threat, especially to workers in confined animal facilities. The dust comes mainly from hog manure, hog skin, feed, and small fragments of insects. The tiny particles in dust can aggravate asthma and allergies, damage the lungs, carry viruses, or cause illnesses such as toxic dust syndrome (Donham and Thu, 1995).

Additional Potential Threats to Public Health and the Environment

Pathogens -- disease-causing organisms

Using current waste systems on hog factories, hog waste being applied to land contains 100 to 10,000 times the number of pathogens in human waste that is treated and applied to land through municipal treatment systems. Although fecal coliforms and E. Coli (common indicators of pathogenic contamination) can be reduced about 99% in lagoons operated and maintained by current best management practices, research shows these pathogen indicators in hog lagoon effluent were still "at levels well above state standards and federal guidelines for maximum allowable fecal coliform concentrations in municipal wastewater applied to land". Research indicates that groundwater wells for home use that are near animal waste land application sites are at risk of contamination by pathogens and other contaminants. Freshly applied hog waste may contain such high levels of pathogens that runoff from rain could degrade the quality of nearby surface waters (Sobsey, 1998). 

Antibiotic resistance

Antibiotics are used in large-scale hog production for two reasons: (1) to cure sick animals, and (2) to improve life expectancy and weight gain and prevent sickness. This latter use, which has increased massively since the 1950s, is far more widespread, and controversial. Overuse of antibiotics in hog production has the potential to create antibiotic resistant pathogens for both hogs and humans. Animal producers are using the same antibiotics for animal production as are used by humans for diseases shared by hogs. Resistant pathogens can be transferred from animals to humans and vice versa (Harvard, 1997-a). Research shows that bacteria associated with some livestock are now 3 to 5 times as resistant to antibiotics as those associated with humans (Harvard, 1997-a). We are "playing with fire" because overuse of antibiotics is a known mechanism to encourage development of disease resistant germs (Harvard, 1997-a; Sobsey, 1998).

Research to fully understand the relationship and potential for antibiotic resistance from animals to humans is ongoing. To date, the studies have shown tendencies and indications for this public health threat, but no conclusions (Harvard, 1997-a). 

Disposing of heavy metals from waste lagoons

Heavy metals in the sludge of waste lagoons can pose serious cleanup problems. Hog feed is fortified with heavy metals, notably copper and zinc, which can be toxic to plants and animals, even at low concentrations. Most of these heavy metals end up in the hog's waste, and, ultimately in a solid sludge that accumulates at the bottom of the waste lagoon for as long as 10 to 20 years -- until it is removed. By that time, the concentration of heavy metals can be high, making environmentally-safe disposal difficult.

In North Carolina, there is no requirement to measure the levels of heavy metals in lagoon sludge until it is removed. 

Greenhouse gases

Greenhouse gases are accumulating in our atmosphere and threaten to drastically alter the climate over the coming decades. The open air anaerobic lagoons used to treat animal waste produce and release methane, nitrous oxide, and possibly other greenhouse gases. In the coming years, efforts to reduce greenhouse gas emissions from all sectors of our society (as well as globally) will likely accelerate. Research into greenhouse gas emissions from animal waste treatment is needed. However, enough is known today to warrant inclusion of greenhouse gas emission reduction as a target in efforts to improve animal waste management.