Sewage sludge (also known as ‘biosolids’) refers to the semi-solids left over from municipal waste water treatment. Current legal disposal options include incineration, landfill, and land application to agricultural land, rangeland, or forests.
The resources on this page provide a scientific overview of health impacts from land application. Risk assessment is complex because Sludge Contains Highly Varied Amounts of Organic Chemicals, Toxic Metals, Chemical Irritants, and Pathogens. Furthermore, the effects of their interactions, long-term build-up in soils, leaching into waterways, and uptake into crops and the food system have not been well-studied. Thus, little is known about the long-term human heath and Ecological Consequences of Sludge Application. There is, however, clear scientific documentation of the sometimes deadly Direct Human Health Consequences of Land Application. Furthermore, by bringing together and concentrating varied pathogens and antibiotics, Wastewater Treatment Selects Antibiotic Resistant Bacteria, a health problem worldwide.
The paucity of scientific research is not accidental. Journalists and researchers have chronicled how the EPA’s Conflicts of Interest and those of other institutions, including the NAS, USDA, municipalities, and universities, obstruct sludge research and further undermine risk assessment and regulation.
EPA’s Sludge Regulation fails to incorporate existing scientific information and to protect the public. Yet while many scientific experts recommend a total ban on sludge application to land, EPA and others continue to promote it. Sludge is sold to the public as nutrient-rich garden compost and portrayed to farmers as a valuable fertilizer.
Even ending land application, however, is only a partial solution. Alternatives, incineration and landfill, are also hazardous. Ensuring ecosystem and human health requires Reformulating the Problem with the explicit goal of preventing sludge formation. This will require organic wastes and industrial wastes be kept separate and treated at their source.
For an illuminating non-technical introduction to the origins of sewerage systems and the creation and disposal of toxic sludge see: Civilization & Sludge: Notes on the History of the Management of Human Excreta by Abby A. Rockefeller.
New and Classic Articles
Sludge Contains Highly varied amounts of
Organic Chemicals, Toxic Metals, Chemical Irritants, and Pathogens
Report: EPA Unable to Assess the Impact of Hundreds of Unregulated Pollutants in Land-Applied Biosolids on Human Health and the Environment. Report #19-P-0002, November 15, 2018
The EPA identified 352 pollutants in biosolids but cannot yet consider these pollutants for further regulation due to either a lack of data or risk assessment tools. Pollutants found in biosolids can include pharmaceuticals, steroids and flame retardants. For the podcast, full report and a summary report see: https://www.epa.gov/office-inspector-general/report-epa-unable-assess-impact-hundreds-unregulated-pollutants-land.
Targeted National Sewage Sludge Survey Sampling and Analysis Technical Report. January 2009; EPA 822-R-08-014.
Section six of this EPA report contains the survey summary. This lists the maximum and minimum levels of different heavy metals, pharmaceuticals, organic chemicals, steroids and hormones, and other pollutants that were found in the sludge samples tested. High levels were found in all pollutant categories, for example PBDEs (brominated flame retardants) and ciprofloxacin and triclosan (antibiotics). Only a small subset of the toxic chemicals in use in the U.S. were surveyed. For the second part of the report and appendices see: http://water.epa.gov/scitech/wastetech/biosolids/tnsss-overview.cfm#results.
Harrison, Ellen Z., et al. “Organic Chemicals in Sewage Sludges.” Science of the Total Environment 367.2 (2006): 481-497.
Summarizes the peer-review literature and government reports on organic chemicals in sewage sludge. While “tens of thousands of organic chemicals are currently in use… sludge concentration data could only be found for 516 organic chemicals.” Identifies the many areas where more research is needed on levels, fate, and toxicity of chemicals to “humans and non-human receptors”. Without this information accurate risk assessment is impossible and sewage sludge application cannot be considered safe.
McBride, M. B. “Toxic Metals in Sewage Sludge-Amended Soils: Has Promotion of Beneficial Use Discounted the Risks?.” Advances in Environmental Research 8.1 (2003): 5-19.
Excellent scientific analysis of heavy metals in sludge and their uptake by crop plants. Uptake of metals varies widely between different types of metals and plants. McBride reveals that “several critical generalizing assumptions about the behavior of sludge-borne metals in soil-crop systems, built into the US EPA risk assessment for metals, have tended to underestimate risks and are shown not to be well justified by published research.” McBride advocates a more science-based precautionary approach to toxic metal additions to soils.
Lewis, David L., and David K. Gattie. “Pathogen Risks From Applying Sewage Sludge to Land.” Environmental Science & Technology 36.13 (2002): 286A-293A.
Lewis and Gattie review the list of known pathogens reported in land applied sewage sludge. They assess the disease risk from these pathogens and point out this risk will be greatly exacerbated by chemical toxins also present in sludge. For example, chemical irritants can predispose skin to infection. Such chemical-pathogen interactions must be taken into account in order to develop science-based policies that adequately protect the public. Lewis and Gattie’s insightful analysis is still valid today.
Ecological Consequences of sludge application
Colman, Benjamin P., et al. “Low Concentrations of Silver Nanoparticles in Biosolids Cause Adverse Ecosystem Responses Under Realistic Field Scenario.” PloS One 8.2 (2013): e57189.
Nanosilver is a biocide. It is commonly used as an anti-microbial in textiles, food packaging, and biomedical applications (e.g. catheters). It enters sewage systems from industrial and other sources, including consumer products (e.g. toothpaste and cosmetics). Coleman et al. showed that nano-silver applied at realistic levels through a common route of exposure (sewage sludge application to farm or rangeland) can adversely affect plants and microbes.
Efromymson RA et al. Final Report: “Evaluation of Ecological Risks Associated with Land Application of Municipal Sewage Sludge.” Oak Ridge National Laboratory ORNL/TM-13703. Sep.30. 1998.
Analysis of the ecological risks arising from the toxic contaminants and excess nitrogen in sewage sludge applied to different land environments (e.g. forest and rangeland). The researchers outlined the complexity of the ecological interactions involved and concluded that there were too many interactions, unknowns, and uncertainties for a definitive risk assessment to be made. Therefore sludge application to these land environments cannot be considered safe. Accurate risk assessment would require understanding the long- and short-term effects of sludge application on soil microbes, plant life and wildlife. It would also require understanding the build-up of contaminants and excess N over time with multiple applications, and their movement from land environments into groundwater, lakes, rivers and oceans.
Direct Human Health Consequences of Land Application
Lowman, Amy, et al. “Land Application of Sewage Sludge: Community Health and Environmental Justice.” Environmental health perspectives 121.5 (2013): 537-542.
In-depth interviews with people living near sewage sludge land-application sites. Interviewees describe health and other quality of life problems, as well as lack of support from public officials. “The most commonly reported symptoms were eye, nose, and throat irritations and gastro-intestinal symptoms (nausea, vomiting, diarrhea). Other symptoms reported by more than one respondent include cough, difficulty breathing, sinus congestion or drainage, and skin infections or sores.”
Czajkowski, Kevin P., et al. “Application of GIS in Evaluating the Potential Impacts of Land Application of Biosolids on Human Health.” A chapter in Geospatial Technologies in Environmental Management. Springer Netherlands, 2010. 165-186.
Using a geographic information system (GIS) and an epidemiological health survey, researchers found statistically higher reports of ill-health symptoms and diseases near “biosolids permitted fields“.
Khuder, Sadik, et al. “Health Survey of Residents Living Near Farm Fields Permitted to Receive Biosolids.” Archives of Environmental & Occupational Health 62.1 (2007): 5-11.
“The findings suggest an increased risk for certain respiratory, gastrointestinal, and other diseases among residents living near farm fields on which the use of biosolids was permitted.” Exposed residents were defined as those living within one mile of fields applying biosolids.
Ghosh, Jaydeep. “Bioaerosols Generated from Biosolids Applied Farm Fields in Wood County, Ohio.” Dissertation. Bowling Green State University, 2005.
Ghosh’s research found that bacterial levels increased after sludge application, then decreased “to control level 13 days after application, except for Staphylococcus aureus, which was highest 13 days after application.” He surmised the increase “might be responsible for reported health problems in nearby residents during the post-application period.”
Harrison, Ellen Z., and Summer Rayne Oakes. “Features: Investigation of Alleged Health Incidents Associated with Land Application of Sewage Sludges” New Solutions: A Journal of Environmental and Occupational Health Policy 12.4 (2003): 387-408.
Documents numerous reports of health incidents from people around the country who live near sewage sludge application sites. Also documents compliance with sludge regulation at application sites. Reported health incidents ranged from “headaches and respiratory problems to death.” The researchers found that “Compliance with the regulations does not ensure protection of public health.” They suggest that “surface-applied Class B sludges present the greatest risk and should be eliminated.” They also advise reconsideration of land application of Class A sludges. Class A sludges have undergone additional treatment intended to reduce pathogen levels compared to Class B sludges. Class A sludges are tested for 2 pathogens and 10 metals and can be applied to land without restriction.
Lewis, David L., et al. “Interactions of Pathogens and Irritant Chemicals in Land-Applied Sewage Sludges (Biosolids).” BMC Public Health 2.1 (2002):11.
Sewage sludge, applied to farmland or residential land, contains pathogens and toxic chemicals. Lewis et al. report results from their health survey of residents living within approximately 1 km of biosolid land application sites. Residents “generally complained of irritation (e.g., skin rashes and burning of the eyes, throat, and lungs) after exposure to winds blowing from treated fields. A prevalence of Staphylococcus aureus infections of the skin and respiratory tract was found. Approximately 1/4 of 54 individuals were infected, including 2 mortalities (septicaemia, pneumonia).”
Wastewater Treatment Selects Antibiotic Resistant Bacteria
Resistance of pathogens to antibiotics and the evolution of multidrug resistant bacteria is an acknowledged international health crisis. Certain human-created environments have been identified as major sources of multidrug-resistant bacteria. These include water treatment plants and concentrated animal feeding operations (CAFOs) (Silbergeld et al. 2008; PEW Initiative: Key Resources on Antibiotics, Superbugs and Industrial Farming; Centers For Disease Control and Prevention (CDC): Antibiotic Resistance and Food Safety).
Zhang, Yongli, et al. “Wastewater Treatment Contributes to Selective Increase of Antibiotic Resistance Among Acinetobacter spp. ” Science of the Total Environment 407.12 (2009): 3702-3706.
Wastewater treatment plants and sewage sludge concentrate both antibiotics and pathogens from numerous sources (e.g. industry, hospitals, homes). “The activated sludge process probably provides a favorable environment with high microbial biomass and selective pressure for horizontal gene transfer of antibiotic resistant genes…” See also: Czekalski, Nadine, et al. “Increased Levels of Multiresistant Bacteria and Resistance Genes After Wastewater Treatment and Their Dissemination into Lake Geneva, Switzerland.” Frontiers In Microbiology 3 (2012). The link between pathogen resistance to antimicrobials and sewage sludge is also noted in Marshall, Bonnie M., and Stuart B. Levy. “Food Animals and Antimicrobials: Impacts on Human Health.” Clinical Microbiology Reviews 24.4 (2011): 718-733.
EPA’s Conflicts of Interest
Snyder, Caroline. “Baltimore Sludge Pilot Project Puts Children at Additional Risk” A letter to International Journal of Occupational and Environmental Health 14.3 (2008): 241.
Documents how a pilot sludge application project — initially proposed as a way to protect children from lead poisoning — instead exposed children living in the test area to even greater risk. The pilot project was based on the assumption that sewage sludge can reduce the bioavailability of lead. Snyder discusses why “the experiment raises a number of important scientific, legal, and ethical questions.”
Snyder, Caroline. “The Dirty Work of Promoting “Recycling” of America’s Sewage Sludge” International Journal of Occupational and Environmental Health 11.4 (2005): 415-427.
This article documents how the EPA works with the commercial sludge disposal industry to promote the farmland application of toxic sewage sludge. EPA and industry tactics include attacking and suppressing the research of independent scientists; funding industry-friendly science; and defending data known to be fraudulent. EPA uses taxpayer money to promote the use of toxic sludge on farmland and cover up its harmful effects. Rather than fund epidemiological or ecological studies into the harmful effects of farmland application, EPA funds workshops to explore whether illnesses reported by sludge victims are “psychosomatic”. A thoroughly documented, well written history of the role of conflicted scientists (including the NAS) and EPA managers in promoting the use of toxic sludge against the public interest.
Stauber, John and Sheldon Rampton. Chapter Eight: “The Sludge Hits the Fan” in Toxic Sludge Is Good For You: Lies, Damn Lies And The Public Relations Industry. Common Courage Press (2002)
Municipal wastewater treatment plants treat industrial as well as municipal waste water. The resulting sewage sludge is thus a complex mix of chemicals, pesticides, pharmaceuticals, acids, heavy metals, radioactive material (e.g. from medical use), and human disease pathogens. Journalists Stauber and Rampton investigate the legalization of farmland application of toxic sludge (i.e. as biosolids) and its marketing to consumers as safe organic compost. They uncover a murky story of collusion between local and federal government, EPA, and the commercial sludge industry, including allegations of links with organized crime.
EPA’s Sludge Regulation
Harrison, Ellen Z., and Murray McBride. “Case for Caution Revisited: Health and Environmental Impacts of Application of Sewage Sludges to Agricultural Land.” Cornell Waste Management Institute, Dept. of Crop and Soil Sciences, Rice Hall, Cornell University, Ithaca, NY, URL: http://cwmi. css. cornell. edu/case. (2009).
Published by the Cornell Waste Management Institute, this invaluable report summarizes key issues in biosolid safety and lists relevant scientific papers. These raise concerns about the agricultural application of sewage sludge and its effects on livestock, human health and the environment. New research documents hazards due to pathogens, heavy metals, endocrine disruptors, antibiotics (including microban), flame retardants and other persistent organic pollutants. Given the known hazards and risks of land application, the researchers argue current sludge regulation does not protect the public. They discuss some alternatives to land application.
Gattie, David K., and David L. Lewis. “A High-Level Disinfection Standard for Land Applying Sewage Sludges (Biosolids).” Environmental Health Perspectives 112.2 (2004): 126.
Gattie and Lewis scientifically assess hazards like bacterial regrowth after sludge application, the production of bacterial toxins, and chemical-pathogen interactions. They propose new high standards for sludge treatment and careful and appropriate monitoring. They suggest this would reduce the adverse health consequences from land application of biosolids.
Harrison, Ellen Z., Murray B. McBride, and David R. Bouldin. “Land Application of Sewage Sludges: an Appraisal of the US Regulations.” International Journal of Environment and Pollution 11.1 (1999): 1-36.
After presenting the current state of scientific knowledge, the researchers conclude that “current US federal regulations governing the land application of sewage sludges do not appear adequately protective of human health, agricultural productivity or ecological health.” They find “US standards are far less protective than those of many European countries and Canadian provinces. This is due to both policy choices such as a ‘do no harm’ philosophy applied in some northern European countries and also to many gaps and non-conservative assumptions in the risk assessment performed by US Environmental Protection Agency.”
Reformulating the Problem
Rockefeller, Abby A. “Sewers, Sewage Treatment, Sludge: Damage Without End.” NEW SOLUTIONS: A Journal of Environmental and Occupational Health Policy 12.4 (2003): 341-346.
“It is in the nature of sewering and sewage treatment to compound environmental problems in the process of moving sewage and in attempting to remove from sewage the pollutants it carries. Spreading sewage sludge on land is but the latest in the compounding of environmental damage from sewerage. This practice must be banned and there must be a federal reorientation of all technology dealing with human excreta and the waste materials from industry and society that now are carried away by sewers. The reorientation must center on biologically based on-site pollution prevention and resource recycling technologies mandated through a revised Clean Water Act.”
Other Websites with Scientific Resources
Cornell Waste Management Institute: Sewage Sludge Links to scientific and policy documents on health and risk assessment, rules, use, and guidelines for sludge.
Sludgefacts.org “Collect(s), analyze(s), and disseminate(s) scientific information about the risks of land applying sludges” and “advocate(s) regulatory reform that protects public health, agriculture, and the environment.”
Sludge News Technical Resources Links to scientific articles or abstracts describing sewage sludge research.
SourceWatch: Scientific Studies of Sewage Sludge Excellent source of scientific studies on different sludge issues — especially its toxic constituents but also hazards from land application and human exposure. Describes findings and links to articles.
[Resources on this page provided by C. Snyder, reviewed by D. Lewis, March 2014, with Introduction and additional resources added by A. Wilson June 2014 and later.]