Are biosolids safe?

25 08 2015

In a recent email from the Green Science Policy Institute, Arlene Blum mentioned that she was just back from Fluoros 2015, which aims to examine the “state of the science” on fluorinated organic compounds in the environment. Her take away was that many of these fluorinated compounds (like those found in fire retardants)  are found in vegetables such as lettuce, tomatoes and strawberries. The assumption is that these man-made chemicals are found in our vegetables because biosolids were used as fertilizer and reclaimed water was used for irrigation.

How does this happen?

First we have to know what a biosolid is: Bascially, biosolids are made from treated sewage sludge, under another (less prejudicial) name. According to the U.S. Environmental Protection Agency, biosolids are “nutrient-rich organic materials”, which contain useful amounts of plant nutrients such as nitrogen, phosphorus and micronutrients. Because it is made from treated sewage, it’s considered safe for use as fertilizer or land reclamation, and about 50% of all biosolids produced in the U.S. are being used as fertilizer, though only about 1% of cropland has biosolids applied.  But the use is growing because the cost to farmers is far less than for chemical fertilizers – by a factor of 4![1]   They can also be composted and sold for use on lawns and home gardens.

Sounds like a dream, right? Using  sewage sludge as fertilizer is a sweet way to get rid of the mountain of sludge produced in the U.S. each year.   Sludge management is an integral part of any municipal waste management system. The most common disposal method is incineration (which has its own problems) and landfills, storage in huge sludge ponds, dried in the sun or dumped in the oceans. But ocean dumping, which created vast dead moon-scapes on the ocean floor, was halted by the Ocean Dumping ban of 1987. Thus the policy of disposing of sludge by spreading it on agricultural land (a policy given the name “land application”) was born.     biosolidsGOC

The problem with biosolids is that most municipal treatment facilities are not able to remove the many chemicals found in sewage. The four main categories of potential pollutants – nutrients, pathogens, toxic organics, and heavy metals – behave differently and cannot all be managed by any single kind of treatment. The goal of “safe management” of such a complex toxic mixture cannot be met at a reasonable cost.

The EPA itself conducted the national Sewage Sludge Survey (NSSS) in 1988 to get information on pollutants found in treated biosolids. They found dozens of hazardous substances, including heavy metals, organics, PBDE’s, pharmaceuticals, steroids and hormones[2] in ALL the sludge samples the EPA took around the USA.

Rolf Halden is a professor at Arizona State University, member of the adjunct faculty at Johns Hopkins and an expert on the environmental impacts of industrial chemicals. His lab recently used treated sewage sludge to identify and prioritize persistent bioaccumulative chemicals.[3] The study found that chemicals contributed between 0.04% – 0.15% of the total dry mass of biosolids produced in the USA annually, which is equivalent to 2,866 – 8,708 tons of chemicals. The top individual chemicals found included:

  • Brominated fire retardants
    • DecaBDE
    • pentaBDE
    • 1,2-bis(2,4,6 tribromophenoxy
    • ethane
  • Surfactants
    • Nonylphenol (NP) and their ethoxylates (NPEOs) – both used in textile processing
  • Antimicrobials
    • Triclosan and triclocarban
  • Antibiotics
    • Azithromycin
    • Ciprofloxacin
    • ofloxacin

The Centers for Disease Control and Prevention (CDC) did a comprehensive exposure assessment of environmental chemicals found the U. S. population. They found about 139 organic chemicals in human blood, serum, urine and tissue samples. About 70% of the chemicals found in biosolids are also found in humans.

New studies have shown that:

  • Sewage sludge is mutagenic (it causes inheritable genetic changes in organisms), but no one seems sure what this means for human or animal health. Regulations for the use of sewage sludge ignore this information.
  • Two-thirds of sewage sludge contains asbestos. Because sludge is often applied to the land dry, asbestos may be a real health danger to farmers, neighbors and their children. Again, regulations don’t mention asbestos.
  • Governments issue numeric standards for metals. However, the movement of metals from soils into groundwater, surface water, plants and wildlife – and of the hundreds of other toxins in sludge – are poorly understood.
  • Soil acidity seems to be the key factor in promoting or retarding the movement of toxic metals into groundwater, wildlife and crops. The National Research Council (NRC) of the National Academy of Sciences gives sewage sludge treatment of soils a clean bill of health in the short term, “as long as…acidic soils are agronomically managed.” However the NRC acknowledges that toxic heavy metals and persistent organic pollutants can build up in treated soils.
  • There is good reason to believe that livestock grazing on plants treated with sewage sludge will ingest the pollutants – either through the grazed plants, or by eating sewage sludge along with the plants. Sheep eating cabbage grown on sludge developed lesions of the liver and thyroid gland. Pigs grown on corn treated with sludge had elevated levels of cadmium in their tissues. An AP story published in 2008 documented that milk sold throughout the U.S contained high levels of thallium (the primary toxin in rat poison), which had been present in the sewage sludge spread on crops fed to dairy cows.[4]
  • Small mammals have been shown to accumulate heavy metals after sewage sludge was applied to forestlands.
  • Insects in the soil absorb toxins, which then accumulate in birds.
  • It has been shown that sewage sludge applied to soils can increase the dioxin intake of humans eating beef (or cow’s milk) produced from those soils.
  • Traces of prescription drugs and household chemicals were found deep in the soil as a result of a couple of decades of use of biosolids as fertilizer.[5]

A study done in Sweden found that scientists have found antibiotic resistant “super bugs” in sewage sludge; they’re sounding the alarm about the danger of antibiotic resistant genes passing into the human food chain. Of the samples collected, 79% tested positive for the drug-resistnat vancomycin-resistant enterococci (VRE)

Astonishingly, in a November, 1990 edition of the United States Federal Register, the Environmental Protection Agency (EPA) had this to say of sewage sludge: “Typically, these constituents may include volatiles, organic solids, nutrients, disease-causing pathogenic organisms (bacteria, viruses, etc.), heavy metals and inorganic ions, and toxic organic chemicals from industrial wastes, household chemicals and pesticides.”

Not all contaminants are created equal:  some chemicals are stored in the human body, and others pass through it.  Some break down in our digestive system, and others don’t.  Each person is different, with a different body size, stage of development and metabolism.   The same chemical may wreak devastating effects if a pregnant woman eats it but may go unnoticed if eaten by a man.  And remember, chemicals are synergistic, and very little is known about interactions between low levels of large numbers of chemicals.  As an example, take the chemical triclosan, one of the antimicrobials that Rolf Halden’s lab found in highest quantities in treated sludge. Triclosan has been used for several decades in antibacterial products like soaps, deodorants and cosmetics.  It is also nearly universally found in sewage sludge.  A recently published study found that soybeans planted in soil containing triclosan took the triclosan up into their beans.

Triclosan is a suspected endocrine disruptor and recent CDC reports show more than a 40 percent increase in triclosan levels in the urine of Americans over a recent two-year period.  The amount in our bodies can’t be blamed entirely on sewage sludge; humans can absorb triclosan through their skin and those who use triclosan-containing toothpastes put the chemical directly into their mouths.   But at what point does exposure to triclosan become more than an individual body can bear?

According to the EPA, about half of all sewage sludge is applied to land, but it is only applied to about one percent of the nation’s farmland.  The likely result is that, if dangers do lurk in the sludge applied to land, we rarely find out about them.

Most people’s chances of eating enough tainted food from farms that apply sewage sludge as fertilizer to cause an acute reaction are pretty slim.  The chance that anyone who got sick would be able to correctly trace his or her illness back to the farm and to sewage sludge is even smaller.  However, a lack of easily traceable acute illnesses does not prove that sewage sludge is safe.  Health harm due to exposure to low levels of toxins over a long period of time is no more acceptable than acute problems, even if they are less obvious.

As a consumer, the only sure way to avoid food grown in sewage sludge is to buy organic food (or grow your own).  If you are a gardener and you wish to avoid sewage sludge fertilizers or composts, avoid any product that says it contains “biosolids.”  Last, if you wish to keep sewage sludge from being spread on farm fields near where you live, you can take action locally to make it illegal in your city or county.

[1] “Davison, Janet, “Earth Day: Is sewage sludge safe for farm fields?”, CBC news Canada, April 22, 2014.

[2] EPA , “Targeted National Sewage Sludge Survey Statistical Analysis Report”, revised April, 2009

[3] Halden, Rolf et al; “Wastewater treatment plants as chemical observatories to forecase ecological and human health risks of manmade chemicals”, Scientific Reports, January 2014

[4] Hellprin, John and Vineys, Kevin: “Sewage-based fertilizer safety doubted”, USA Today; 3.6.2008

[5] Bienkowski, Brian, “Farm sludge contaminates soil with drugs, other chemicals”, Environmental Health News, May 2014.