Several million dry tons of sewage sludge, also known as biosolids, are used as fertilizer on agricultural lands and given away or sold for use by homeowners and landscape contractors annually in the U.S. Sewage sludge is the semi-solid to solid matter left over following municipal wastewater treatment. It commonly contains nutrient-rich fecal matter along with bacteria, viruses, parasites, heavy metals, pharmaceuticals and other chemical contaminants—many known to cause health effects.
For farmers, sludge is a less expensive alternative to synthetic fertilizers, but use of sewage sludge as fertilizer for food production increases our risk of exposure to sludge
contaminants and their associated health effects. Due to the persistent nature of some of these contaminants, repeated applications to the same piece of land can increase soil contaminant levels and possibly food contaminant levels for centuries to come.
What’s in sludge?
Though the types and levels of contaminants in sludge are
variable, sludge contaminants fall into three main groups,
1. Disease-causing microbes. Sewage treatment reduces but does not eliminate disease-causing microbes in sludge. Those commonly found in sludge include: 18 human-excreted viruses, including Hepatitis A and Polio; 19 parasites, including Cryptosporidium and Giardia; and 31 bacteria, including strains causing food poisoning (Salmonella and E. coli 0157:H7), as well as more virulent, antibiotic-resistant strains.
2. Synthetic chemicals. More than 500 synthetic chemical compounds, typically derived from fossil fuels, have been identified to date in various sludges, including chemicals from medicines and consumer products such as antidepressants, steroids, flame retardants, detergents, fragrances, disinfectants and more. Other chemicals still detectable in present-day sludge, such as polychlorinated biphenyls (PCBs), have been banned from use for decades.
3. Heavy metals. Arsenic, cadmium, lead, mercury and other heavy metals are commonly detected in sludge, though concentrations have decreased for some metals over time. Also, radioactive material, both naturally occurring and from human-made sources (such as feces and urine from people undergoing radiation therapy), can be found in sludge.
While I took this information verbatim from the OCA, please follow the link to reach the PDF if you are curious about sources behind these facts (Click on "read more" under "Smart Guide on Slude Use and Food Production").
What can we do about sludge? I will be posting on this more to come, but for now: buy certified organic when possible, get to know farmers at local markets and inquire as to their farming practice, plant your own food (urban/community gardening), and get in touch with your elected officials. I will be posting sludge campaign information as it comes to my attention.
More on the history of sludge.