The most well-documented impacts of agriculture runoff on human and ecological health are primarily related to nutrient pollution in water, where nitrogen and phosphorous from fertilizers cause oxygen-starved “dead zones” in water.
Now, scientists and government agencies are also examining the impacts of agriculture runoff as a significant source of emerging contaminants, substances that may pose a health risk when they enter food or water systems.
Emerging contaminants (ECs) — which include hormones, antibiotics, steroids, nanomaterials, human pharmaceuticals, and personal care products — are difficult to measure or identify, but they pose special threats to human and ecological health. However, few regulations prevent agriculture operations from releasing ECs into the environment.
“Emerging contaminants are a perfect example of how regulations are behind the technology,” said Patty Lovera, assistant director of Food & Water Watch, “We are releasing contaminates from agriculture when we still do not fully understand them, and our current regulations do not keep us safe from them.”
What are emerging contaminants?
“An emerging contaminant is defined by how difficult it is to measure,” said Dr. Daniel D. Snow, who studies emerging contaminants at the University of Nebraska-Lincoln. “In the ’70s and ’80s, we did not have the technology to measure these substances at the very low levels which they occur.”
Over time, new technology has made the study of certain substances more accessible. So an EC is not necessarily a new substance; rather, an EC may have existed previously, but scientists are just now recognizing its presence or significance.
While a single agreed-upon definition of an EC does not exist, the U.S. Food and Drug Administration (FDA) defines an EC as “a chemical or material characterized by a perceived, potential, or real threat to human health or the environment or by a lack of published health standards. A contaminant also may be ‘emerging’ because of the discovery of a new source or a new pathway to humans.”
Certain ECs used in industrial livestock production
Agriculture can be both a source and a recipient of a wide range of ECs. Perhaps most notably, the use of ECs such as antibiotics and hormones has become standard industry practice in industrial livestock production.
In July 2013, the U.S. Environmental Protection Agency (EPA) published a review of contaminants in livestock and poultry manure. The review states that, while EPA’s past reports on water quality and manure have focused on nutrient issues, the goal of this document was to summarize the growing body of information on other contaminants in manure.
Specifically, the EPA review addresses two major ECs — antimicrobials and hormones.
Antimicrobials are administered to livestock and poultry for disease treatment and prevention. But some antimicrobials are also administered for non-therapeutic purposes such as to promote animal growth and feed efficiency.
As for hormones, livestock naturally excrete some hormones, but they are also administered to improve meat quality, promote animal growth, control reproduction, and increase milk production.
ECs released from nonpoint agricultural runoff
“Nonpoint” agriculture runoff occurs when water — whether from rain, snowmelt, or irrigation — moves over land while picking up and carrying away pollutants, which it eventually deposits in water bodies. By comparison, a point-source pollutant is discharged from a single point such as a sewage treatment plant.
According to EPA, agriculture runoff is “the leading source of water quality impacts on surveyed rivers and lakes, the second largest source of impairments to wetlands, and a major contributor to contamination of surveyed estuaries and ground water.”
Agriculture activities that cause nonpoint runoff “include poorly located or managed animal feeding operations; overgrazing; plowing too often or at the wrong time; and improper, excessive, or poorly timed application of pesticides, irrigation water, and fertilizer.”
In 2012, Alistair B.A. Boxall of the University of York published a comprehensive article on ECs and agriculture for the Organization for Economic Co-Operation and Development (OECD).
“Once an EC is released to or from an agriculture source,” Boxall explained, “it may be degraded, stick to soil particles, taken up by plants, leach to groundwater, or transported to surface waters through runoff and drainage water. The extent will depend on physical properties of the EC as well as the land and climate conditions.”
ECs may pose risk to human and ecological health
The EPA review explains that antimicrobial and hormone use in livestock production has recognized impacts on human and ecological health. For example, the use of antimicrobials in livestock production has contributed to antimicrobial-resistant pathogens, and it may compromise the effectiveness of medications in treating infections.
And hormones are endocrine disrupters, so they may affect the reproductive biology and health of aquatic organisms when they enter water sources.
Overall, EPA still has many questions about the impacts of these substances. The EPA review concludes: “The extent to which antimicrobial resistant human infections are related to the use of antimicrobials in livestock and poultry is unclear and would benefit from further research.”
“More research on the use, occurrence, fate, and transport of natural and synthetic hormones from production facilities and cropland treated with manure is necessary to fully understand their potential impact,” the review added.
Challenges to understanding agriculture-source ECs
The Boxall article identifies challenges to studying ECs from agriculture sources, whether from nonpoint runoff or not. They include: the very low levels which ECs typically occur, challenges of distinguishing between natural and human-made materials, and determining whether current analytical methods are appropriate for certain ECs.
More generally, analysis is time consuming, costly, and requires highly sophisticated equipment.
“It is easier to get funding to research wastewater treatment discharge,” Snow said. “In general, agencies are most likely to fund studies to treat point rather then nonpoint sources because point sources are easier to control.”
For example, the majority of studies related to the impacts of hormones — which are released from human as well as livestock waste — on water bodies have focused on discharge from wastewater treatment facilities rather than from livestock operations.
“[ECs] are used because they are biologically active. We use them in agriculture because they cause an effect, whether for reproduction or control. Because they are biologically active, they can have some unintentional consequences such as when they occur in places we don’t intend them to be. We probably have some responsibility to understand what those unintended consequences are.”
Current regulations do not limit EC release into the environment
The primary statute governing chemical use in the U.S. is the Toxic Substances Control Act (TSCA). TSCA was adopted in 1976 and has not since been significantly amended despite advancements in technology and new understandings of ECs. Most groups, including consumer advocates, science associations, and government agencies, agree that TSCA needs to be updated to ensure chemical safety.
In May 2013, U.S. Sens. Frank Lautenberg and David Vitter introduced the Chemical Safety Improvement Act with strong bipartisan support. Improvements to TSCA would include mandating safety evaluations for all chemicals used in commerce, requiring new chemicals to be deemed safe before entering the market, and making more information about chemicals publicly available.
In addition to improving TSCA, some groups have focused on regulating specific ECs.
The Natural Resources Defense Counsel (NRDC), for example, has won two decisions against FDA (one is on appeal) for the agency’s failure to withdraw approval for non-therapeutic uses of penicillin and tetracyclines in animal feed when FDA acknowledged more than 30 years ago that using antibiotics in livestock production poses human health risks.
“Ideally, antibiotic use will be replaced with better management practices,” said NRDC staff attorney Avi Kar.
Kar pointed out that Denmark, a large pork exporter, banned antibiotics in feed more than a decade ago and uses better management practices. Since then, Denmark’s livestock production has grown.
Others groups are focusing on the limitations of the Clean Water Act. Lovera said that the unknowns and potential threats surrounding ECs are just one piece of the 30-year battle under the Clean Water Act to impose meaningful regulations on industrial livestock operations.
Food & Water Watch recently filed a lawsuit against EPA over the agency’s failure to collect basic information on concentrated animal feeding operations (CAFOs) such as the name, location, and number of animals.
“How are we supposed to regulate CAFOs and what they are emitting if we don’t even know where they are?” Lovera asked.
Additionally, the EPA review on contaminates in manure emphasizes that estimating the use of antimicrobials and hormones in livestock production is extremely challenging because operators are not required to disclose what they administer to livestock or poultry.
Food Safety News