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. http://www.environmentalhealthnews.org/ehs/news/2014/may/biosolids-contaminants

 

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Nylon 6 and Nylon 6,6

5 06 2012

Nylon is a synthetic polymer called a polyamide  because of the characteristic monomers of amides in the backbone chain.  Polyamides are also naturally occurring – proteins such as wool and silk are also polyamides.

We commonly see two basic types of nylon used in fabrics: nylon 6 and nylon 6,6:

  • Nylon 6,6:  Two different molecules (adipic acid and hexamethylene diamine)  are combined to create repeat units of 6 carbon atoms, thus the name nylon 6,6.
  • Nylon 6:  Only one type of molecule is used in the formation of nylon 6, which also has 6 carbon atoms.  The repeat unit for type 6 nylon is made from caprolactam (also called ε-caprolactam).

Remember polyester is also a polymer (as are lots of naturally occurring things).  And like polyester, the nylon polymers are theoretically unreactive and not particularly harmful, but that’s not true of the monomers:

  • A small % of the monomers escape during production (off gassing or into water), which have environmental consequences.
  • With production expected to be over  4.4 million pounds/year by 2020, burden on water treatment facilities is immense.
  • Monomers are precipitated out during treatment, so they are present in the sludge.

The manufacture of both nylon 6,6 and nylon 6 uses cyclohexane as a precursor [1] – and cyclohexane is made from benzene, “one of the most challenging processes in the chemical industry”.[2]  Benzene is listed as a human carcinogen by the US Department of Health and Human Services.  It is associated with acute myeloid leukemia (AML), aplastic anemia, myleodysplastic syndrome (MDS), acute lymphoblastic leukemia (ALL), and chronic myeloid leukemia (CML)[3]  The American Petroleum Institute (API) stated in 1948 that “it is generally considered that the only absolutely safe concentration for benzene is zero.” [[4]

But the real culprits are the generation of unwanted by-products of nylon manufacture:  ammonium sulfate [5] in the case of nylon 6 and nitrous oxide in the case of nylon 6,6.

For nylon 6, the conventional synthesis route to caprolactam uses toxic hydroxylamine (NH2OH) and, in the last two steps, concentrated sulfuric acid. Every metric ton of caprolactam produces up to 4.5 tons of ammonium sulfate as a by-product [6].  As with many chemicals now in use, there is no data to evaluate ammonium sulfate as to toxicity to humans, though it has been shown to affect development, growth and mortality in amphibians, crustaceans, fish, insects, mollusks, and other organisms.[7]

In addition, waste water generated during production of nylon-6 contains the unreacted monomer, caprolactam. Owing to the polluting and toxic nature of ε-caprolactam, “its removal from waste streams is necessary”[8]

In evaluating the chief components of nylon 6,6  (hexamethlylenediamine and adipic acid), we find a darker situation.   Hexamethlylenediamine is a  petroleum derivative,  with the usual consequences of petroleum processing. It is considered “mildly toxic”[9] (though in one study, ten administrations of 700 mg/kg to mice killed 3 of 20[10]).   But the production of the other monomer,  adipic acid,  requires the oxidation of cyclohexanol or cyclohexanone by nitric acid, a process which produces nitrous oxide (N2O) –  a greenhouse gas 300 times more potent than CO2.[11]  A study published in 1991 credits the production of nylon – and the concurrent by-product of nitrous oxide – as contributing as much as 10% to the increased observance of atmospheric N2O.[12]  And this is a great concern, so much so that there is increased talk of our “nitrogen footprint”.

Nitrogen is one of the 5 elements (the others are carbon, hydrogen, oxygen, and phosphorus) that make life possible. It is essential for the creation of DNA, amino acids and proteins. 79% of the earth’s atmosphere is made up of nitrogen, but living things can’t use it in this form called dinitrogen (N2).  So in the nitrogen cycle, lightning  converts N2 into nitrate, which is carried to Earth by rain, where it enters the food chain.  When organisms die, bacteria recycles the nitrogen in them and it returns to the atmosphere.  Pretty elegant, isn’t it?

From: Nitrous Oxide Focus Group

But we have disrupted this nitrogen cycle.  A study by University of Virginia environmental scientist James Galloway and colleagues reported that from 1970 to 2008, world population increased by 78% and reactive nitrogen creation grew 120%.[13] The turning point, according to the International Nitrogen Initiative, came in 1909 when humans figured out how to combine hydrogen with N2 to create ammonia – which was used to produce fertilizer. Humans have introduced additional reactive nitrogen into the environment by expanding the production of soybeans, peanuts and alfalfa, (leguminous) crops which host nitrogen-fixing bacteria that convert N2 into reactive nitrogen. We use ammonia to manufacture nylon, plastics, resins, animal and fish feed supplements, and explosives. Fossil fuel burning industries and vehicles produce nitrogen emissions, and nitrogen is a component of the electronics, steel, drug, missile and refrigerant industries.

A single nitrogen molecule can cascade through the environment affecting air and water quality, human health and global warming in numerous ways(click here for a summary):

  • Runoff from agriculture—from fertilized crops fed to animals, from manure, and from biofuel and crops—enters rivers and streams and can contaminate groundwater. When nitrogen-loaded runoff makes its way to the ocean, it can result in eutrophication, where algae bloom, then die, depleting the oxygen and suffocating plants and animals. Runoff from urban areas, sewage treatment plants, and industrial wastewater also contribute to eutrophication.
  • Nitrogen is also a component of acid rain, which can acidify soils, lakes and streams. While some trees may utilize the extra nitrogen to grow, others experience foliage damage and have reduced tolerance for stress.
  • Our air quality is affected by nitrogen emissions from vehicles, fossil fuel burning industries (like coal), and the ammonia from agriculture, which cause ground-level ozone. High concentrations of ozone affect human respiratory and cardiovascular health and disrupt photosynthesis in plants.
  • Climate change is both influenced by and exacerbated by nitrogen. For example, nitrogen may stimulate plant growth, resulting in more carbon dioxide uptake in some forests.

Scientists have stressed the need to reduce fossil fuel emissions, improve wastewater treatment, restore natural nitrogen sinks in wetlands, and both reduce the use and increase the efficiency of nitrogen fertilizers. Galloway’s study also underscores the importance of better management of animal waste from the concentrated animal feeding operations that produce most of our meat today.

Another concern of using nylon is that all nylons break down in fire and form hazardous smoke.  Also smoke from burning nylon at a landfill emits the same chemicals,  typically containing  hydrogen cyanide, nitrous oxide (N2O) and dioxins[14].

Because nylon 6,6 is made from two different molecules, it is very difficult to recycle and/or repurpose.  Trying to separate and re-use them is like “trying to unbake a cake”.  However, nylon 6, because it is made from only one molecule, can easily be re-polymerized, and therin lies it’s claims to environmental superiority.  But  nylon production uses a lot of energy – about double that of polyester.  If recycling it uses about half the energy as is needed to produce virgin nylon, then recycled nylon and virgin polyester use about the same amount of energy.

Nylon 6 is becoming the new green darling of designers – but unless the recyling process captures all emissions, treats wastewater and sludge and also recaptures the energy used, the claim is tepid at best.  And nylon, unlike polyester, does degrade,  but slowly[15], giving it plenty of time to release its chemical load into our groundwater

I couldn’t find any data on the toxicity of nylon as fabric, but the government of Canada has evaluated nylon 6,6 because it is also used in cosmetics, and classified it as a “medium human health priority”; it is also on the Environment Canada Domestic Substance List.[16]  Another study found that some of the chemicals in nylon kitchen utensils migrated into food.[17]


[1] The remaining less than five percent of installed caprolactam capacity is via the cyclohexane photonitrozation process of Toray, which goes directly from cyclohexane to the oxime, or the SNIA Viscosa process, which utilizes toluene as feedstock and proceeds via oxidation-hydrogenation-nitrozation.  http://www.chemsystems.com/about/cs/news/items/PERP%200910_1_Caprolactam.cfm

[2] Villaluenga, J.P. Garcia, Tabe-Mohammadi, A., “A review on the separation of benzene/cyclohexane mixtures by pervaporation processes, Journal of Membrane Science, Vol 169, issue 2, pp. 159-174, May 2000.

[3] Smith, Martyn T. (2010). “Advances in understanding benzene health effects and susceptibility”. Ann Rev Pub Health 31: 133–48. DOI:10.1146/annurev.publhealth.012809.103646.

[4] American Petroleum Institute, API Toxicological Review, Benzene, September 1948, Agency for Toxic Substances and Disease Registry, Department of Health and Human Services

[6] Hoelderich, Wolfgang and Dahlhoff, Gerd, “The Greening of Nylon”, Chemical Innovation, February 2001, Vol 31, ppg. 29-40 and Weston, Charles et al, “Ammonium Compounds”, Encyclopedia of Chemical Technology, June 20, 2003, http://onlinelibrary.wiley.com/doi/10.1002/0471238961.0113131523051920.a01.pub2/abstract

[8] Kulkarni, Rahul and Kanekar, Pradnya, “Bioremediation of e-Caprolactum from Nylon 6 waste water…” MICROBIOLOGY, Vol 37, Number 3 1997

[10] “Handbook of Toxic Properties of Monomers and Additives”, Victor O. Sheffel, CRC Press, Inc., 1995

[11] 2007 IPCC Fourth Assessment Report (AR4) by Working Group 1 (WG1), Chapter 2 “Changes in Atmospheric Constituents and in Radiative Forcing” which contains information on global warming potential (GWP) of greenhouse gases

[12] Thiemens, Mark and Trogler, William, “Nylon Production: An unknown source of atmospheric nitrous oxide”, Science, February 1991, vol 251, pp 932-934

[13] Galloway, JN, and Gruber,  “An Earth-system perspective of the global nitrogen cycle.” Nature 451, 2008, 293-296.

[15] For nylon fabric, current estimates are 30 – 40 years.





A non organic future?

25 05 2011

According to the World Population Clock at the Office of Population Research at Princeton University, the population of the world is now 6.92 billion people.  We’re supposed to reach 7 billion by the end of October of this year, according to the United Nations.  This is much faster than anyone had expected and represents an increase of one billion people in just 12 years[1].

Hania Zlotnik,  director of the population division in the UN department of economic and social affairs, says  “What is astounding is that the last two billion have been reached in record time… it’s not about how many people there are but where they are:  most of these people are being added in the poorest countries of the world.”  That means those countries least able to handle these new citizens, and they’re already the most vulnerable to famine.

Whether there is a reasonable chance of slowing the population growth rate is still being hotly debated, but all agree that these new numbers are causing shockwaves in many areas.   One area which is attracting lots of attention looks at how we’re going to feed all these people.  And because we’re proponents of using organically grown fibers (and organic agriculture in general), we think it’s important to investigate these arguments about the benefits of organic vs. conventional agriculture.

At the start of 2011, according to The Economist in a special report  about feeding the  world, “The 9 billion – people question“, the “fact that agriculture has experienced two big price spikes in under four years suggests that something serious is rattling the world’s food chain.”   World food prices have risen above the peak they reached in early 2008.  The food industry is in crisis – and certainly the era of cheap food is over.   There are mounting concerns that we cannot feed even the current population, let alone the 9 billion people expected by 2050.

According to The Economist:  The world looks to farmers to do more than just produce food. Agriculture is also central to reducing hunger (which is not quite the same thing) and provides many people’s main route out of poverty. Food is probably the biggest single influence on people’s health, though in radically different ways in poor countries than in rich ones, where the big problem now is obesity. Food is also one of the few pleasures available to the poorest.

In The Economist’s view (which is held by many scientists, food companies, plant breeders and international development agencies)  traditional and organic agriculture is a luxury of the rich.  They say that this type of farming could feed Europeans and Americans well.   But it cannot feed the world.

Central panel: The Garden of Earthly Delights" by Hieronymus Bosch

Pedro Sanchez, Director and Senior Research Scholar at the Earth Institute of Columbia University, says  If you ask me point blank whether organic-based farming is better than conventional, my answer is no.  There are just too many of us, we just need too many nutrients.  And those nutrients come from plants that need nutrients that organic fertilizers can’t always provide.”

And Mark Rosegrant, of the International Food Policy Research Institute, points out that  organic production tends to have somewhat lower yields compared to non-organics. He says going all organic would require a whole lot more land. Organic farming is, he says, a niche market. It’s not bad, per se, but it’s not an important part of the overall process to feed 9 billion people.

Needless to say, we’re interested in finding out more about this topic!  We’ll start our own series (feeding and clothing 9 billion!) next week – the subject is really complex and we will need several weeks to do it justice.