Biosolids #2: Industrial, Household, & Ag Chemicals

Written By Sarah Sorci

This is the second of several articles exploring the use of biosolids in agriculture and residential composting products. We begin with general info about contaminants in biosolids; which contaminants wastewater treatment can and cannot remove; how well plants absorb those contaminants; and more. 

The series will culminate with western New York-specific information. Where are biosolids being applied locally? Which locally-available bagged compost products are made from biosolids? In which WNY towns have residents, farmers and governing bodies experienced conflict around this issue?

This topic is heavy! We'll take a biosolids break in the next article, and explore a local park's history and management practices.

Compost: The Great Equalizer

When I've read articles about toxin-safe gardening and soil “improvement,” compost is the heroic answer for so many issues. Compost is decomposed organic matter—usually a mix of “brown,” or carbon-rich materials (dead leaves, newspaper, straw) and “green,” or nitrogen-rich materials (food scraps, grass clippings). It’s the magic wand for balancing clay soil, sandy soil—or pretty much any soil type you might have.

There is evidence that compost can reduce the bioavailability of heavy metals in the soil. This benefit isn't lost on biosolids-based composts, even though they add more heavy metals to the mix. Check out this study described by Dr. Sally Brown, professor at the University of Washington’s School of Forest Resources:

'Scientists added metal salts to soils in pots and grew plants to see how much of the metal would be taken up by plants, and at what point plants would start to die. From these studies, initial metal limits for biosolids were established. However, when the tests were repeated using real biosolids (with metals actually in the biosolids, rather than added as salts), results were very different. The same metal concentrations that killed plants when added as salts had no effect on plant yield, and plant metal concentrations were often orders of magnitude lower' (Brown). 

Brown also describes this compelling study: gardens in Baltimore were treated with local biosolids. For areas highest in lead, adding biosolids compost reduced lead availability by 64- 67% (measured by a lab extraction), compared to soil that did not receive biosolids.

This research offers some comfort when considering the biosolids that have already been applied in our community. Unfortunately, the data may not reveal the complexity of consequences when adding heavy metals and other contaminants to natural systems. And not all contaminants have the relationship with compost that these heavy metals do. 

Industrial, Agricultural, and Household Chemicals in Biosolids

In 1993, the EPA created its “Part 503(b) rules” for land application of biosolids. These rules set standards for nine heavy metals, pathogens, and nutrients-- but not for toxic organic chemicals (Institute for Agriculture and Trade Policy). The word 'organic' is used here in the chemistry sense-- molecules containing carbon. According to the Institute for Agriculture and Trade Policy (IATP), biosolids contain more than 60,000 toxic substances and chemical compounds which are not addressed by EPA regulations. 

Reasons the EPA has given for not regulating these harmful chemicals:

  • They are currently banned from use in the U.S;

  • They are detected in less than five percent of biosolids sampled nationally;

  • They exist in biosolids in concentrations that did not surpass “risk-based soil loading rates” (IATP)

According to a report by the Cornell Waste Management Institute, 

"There are… many other chemicals now in widespread usage that were not even considered when the 503 rules were promulgated. Among those are the brominated flame retardants, antibacterials, wastewater treatment flocculant polymers, organotins, surfactants, fragrance chemicals, and pharmaceuticals. Over 500 different synthetic organic chemicals have been reported in sewage sludges. Concentrations of many exceed Soil Screening levels set by EPA. None are regulated in sewage biosolids in the US. EPA eliminated organic chemicals from regulatory consideration based on insensitive analyses that had high detection limits for most organic chemicals, too high to measure levels that would be of environmental significance" (Harrison). 

While there is evidence that some heavy metals may become less bioavailable when compost is applied (including biosolids), many other contaminants do not behave this way. There is data indicating that when pesticides combine with water-soluble dissolved organic matter-- like when biosolids are added-- it can lead to faster leaching of those chemicals (Harrison). Pharmaceuticals are a concern since they are designed to be biologically active and well-absorbed by living organisms. More on pharmaceuticals in a later article. 

Some compounds also degrade into “daughter products” that may be more toxic than the original compound (Harrison). Alkylphenol ethoxylates (APEs), surfactants in paints and some household and industrial cleaning products, are one example. APEs are “a group of chemicals present in large quantities in biosolids” (Harrison). Anaerobic treatment methods at wastewater treatment plants have been found to promote their transformation into more toxic substances (Harrison). Though APEs are restricted in Europe, they are not monitored in biosolids in the US (Harrison). 

Persistent Organic Pollutants 

One problem with not regulating contaminants that are currently banned from US products is that some of those chemicals persist in the environment long after they arrive. In fact, this persistence is one reason why some of these chemicals were banned in the first place.  Dioxins are one type of Persistent Organic Pollutant (POPs). Dioxins have been found to be disruptive to reproduction and development, as well as immunity and endocrine function. They are also linked to cancer. Some forms of dioxin occur naturally, and from burning fuel or wood; PCBs are dioxin-like compounds produced by manufacturing (Nordqvist, 2017).

Products containing PCBs were banned in the US in the late 1970s, and PCB production for manufacturing has decreased by over 90% since then (Nordqvist, 2017). However, PCBs are still found in sewage sludge today due to their persistence. Like other POPs, repeated application has the potential to build up their concentration in the soil. Land application of sewage sludge has been found to increase dioxin intake of people who ingest food products from cattle raised on biosolids-amended soil (IATP). Dioxins are fat-soluble, and easily stored in the bodies of animals and humans. Over 90% of human exposure comes from our food, particularly dairy, meat, and seafood (Nordqvist, 2017). 

Other POPs that have tested high in some sludges include brominated flame retardants (PBDEs) and antimicrobial compounds triclosan and triclocarban (Harrison). 

Complexity of Natural Systems: What Research Has Not Captured

According to the New York State DEC, most sewage sludge contains “low levels” of synthetic chemicals from industrial waste, pesticides, and household products, justifying the lack of regulation of these chemicals in the federal Part 503 rules. However, a 2018 EPA report offers this summary:

“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” (EPA 2018).

It appears to me that biosolids are another case of the “do it until proven guilty” approach in US environmental policy. A USGS study on chemical contaminants in biosolids was called the “first comprehensive examination of biosolids” (USGS). This paper wasn’t published until 2006—many years after biosolids application began in the US. In 2018, USGS still states on its website that "What is not known at present is the transport, fate, and potential ecological effects of these contaminants once biosolids are applied to agricultural fields, garden plots, and landscaped plants and shrubs" (USGS). 

 We do know that exposure to biosolids can have a significant impact on the health of humans living within a mile from farm fields, as well as livestock.

One study found that "male sheep exposed to low levels of pollutants by grazing on pastures fertilized with sewage sludge developed bone tissue abnormalities" (Lind et al, 2009). Other studies found issues with cellular and hormone disruption in fetuses, and reduced fetal body weight, in sheep raised on sludge-treated pasture (Harrison). This information may have implications for fertility in humans.

A health survey in Ohio looked at individuals living within a mile of farm fields where biosolids are applied. The survey results found statistically significant increases in "excessive secretion of tears, abdominal bloating, jaundice, skin ulcer, dehydration, weight loss, and general weakness... bronchitis, upper respiratory infection, and giardiasis.... The findings suggest an increased risk for certain respiratory, gastrointestinal, and other diseases" (Khuder, 2007).

The burden of proof-- and the cost of more thorough research and sewage treatment as needed-- should rest on government agencies entrusted with our tax dollars to keep citizens and ecosystems safe. Instead, the risks and consequences are passed off to communities and consumers. The problem with environmental contamination is that it’s difficult to pinpoint causes of health issues-- especially when the average American is exposed to harmful chemicals on a daily basis in our food, water, and air.

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Sources

Sarah Sorci
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Resource for Choosing Household Products
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Biosolids, Part 1: An Orientation