Black Mayonaise

What Exactly Is the Black Mayonnaise at the Bottom of the Gowanus Canal?

Photo by Susan De Vries  by Craig Hubert

There are numerous mysteries about the Gowanus Canal. But the most baffling, not to mention terrifying, is the thick dark sludge that makes it way through the oily waters, that which has been called black mayonnaise.

Aside from its gross name — which is a pretty good descriptor, to be honest — there has rarely been an acceptable explanation of what black mayonnaise is, exactly, and how it is formed. So we reached out to Christos Tsiamis, the EPA’s Senior Project Manager for the Gowanus Superfund cleanup, and asked him to explain.

gowanus canal black mayonnaiseA core sample from the former First Street Basin near the BRT Power Station. Photo via EPA’s Gowanus Canal Facebook Group

Black mayonnaise is the “result of chemical waste that was discharged from the industries that operated along the canal as well as by New York City sewage and street runoff,” wrote Tsiamis in an email.

“The combination of the chemicals and sewage gave the sediment the soft texture of mayonnaise, while the combination of liquid tar from the manufactured-gas plants, petroleum products (such as motor and lubricating oils), decomposed organic matter and sewage gave to this sediment its black color.”

gowanus canal brooklyn superfund sitesPhoto by Hannah Frishberg

A 10-foot-high layer of black mayonnaise lays over the original native sediment at the bottom of the canal. But is it dangerous?

The answer is a resounding yes.

“It contains a multitude of chemicals (in the dozens) many of which are toxic and dangerous to human health upon repeated exposure or from consumption of fish that is caught at the canal (or at close proximity to it) over time,” wrote Tsiamis. This was determined by a risk assessment study conducted by the EPA in 2010.

Will the cleanup cleanse the canal of black mayonnaise forever? Two months of dredging, starting in December, is expected to permanently clean the bottom of the canal, according to Tsiamis. Meanwhile, the Gowanus’ two new underground holding tanks are expected to keep a good part of sewage and street run-off from overflowing into the canal during storms. “After the storm passes, the liquid held by these tanks will be pumped for treatment to the city’s treatment facilities,” he said.

Tsiamis says these measures will free the canal of black mayonnaise forever. But the EPA will be checking every five years anyway, just in case the substance inexplicably returns.

Until next time,

Garbage Girl

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Coal Tar Waste Sites~Surprise!

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Many areas of the country have sites that are a serious health concern and we don’t even know about them.  Some of them are your driveway.  Coal tar is the reason.

A study published in the journal Environmental Science and Technology is one of the first steps in understanding how this widely used carcinogen is impacting human health.  Further information can be obtained from the blog Coal Free America.   http://coaltarfreeamerica.blogspot.com/p/references.html

Coal tar is a thick, black or brown liquid byproduct of carbonized coal for the steel industry.  Coal-tar used for pavement sealants is the viscoelastic polymer resin that has 50% or more PAHs by weight and is known to cause cancer in humans.

PAHs are a group of chemical compounds (polycyclic aromatic hydrocarbon) that form whenever anything with a carbon base is burned.   PAHs are of environmental concern because several are toxic, carcinogenic, mutagenic or teratogenic (causing birth defects) to aquatic life, and seven are probable human carcinogens.  Of all known PAH sources, the highest concentrations are in coal tar and the related compound creosote. The International Agency for Research on Cancer states that up to one-third of the contents of coal-tar sealants is cancer-causing polycyclic aromatic hydrocarbons.

PAHs are substances that remain in the environment for a long time, do not decompose and bioaccumulate in the human body.   Substances that combine these characteristics represent a particular level of environmental concern labeled PBTs.  (Persistent, Bioaccumulative, and Toxic substances)

images-1And!  PAHs don’t stay put.  Wear and tear from tires and sneakers on coal tar sealed pavement breaks down the dried sealant allowing tiny PAH particles to be tracked into homes or blown through open windows. The small particles from tire abrasion can be washed off by rain and carried down storm drains into streams.  Other sealcoat particles adhere to tires and get transported to other surfaces or blown offsite by wind.

Sealcoat in high traffic areas wears down within a few months and manufacturers recommend a new application every 2 to 4 years.

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Partners for a Healthier Community gfrpartners.com

Black house dust is a source of human exposure to many contaminants, including PAHs.  Small children, who spend time on the floor and put their hands and objects into their mouths and active kids playing ball games are most vulnerable.   In 2008, the United States Geological Society measured PAHs in house dust from 23 ground-floor apartments and in dust from the apartment parking lots.   PAH concentrations in the dust from the parking lots with coal tar seal coats were an average of 530 times higher than parking lots with other surface types.  The indoor concentrations were 25 times higher.

Anything above 1.0 is considered a mutagen.  Coal tar sealants average 450.  Mutagens are physical or chemical agents that change the genetic material of an organism and  increase the frequency of mutations that can cause cancer.

Motor oil, a product that’s illegal to pour down storm drains, contains about 500 milligrams per kilogram of PAH chemicals.  Coal tar contains about 50,000 mg/kg, but we’re still spreading it on our parking lots, driveways and playgrounds with the potential for rains to wash it down storm drains.

Oddly enough, coal tar is rated Category I (safe and effective) for over the counter products to treat dandruff, seborrhoea, eczema, and psoriasis, according to the Food and Drug Administration.   Because of its use in medicines, as well, many studies have been performed over nearly a century to see if the patients who intentionally expose themselves to high level doses of coal tar for long periods of time have increased risk of cancer.  All the studies have reached the same conclusion – there is no evidence of cancer.

Brand name products using coal tar to treat  skin disorders are Betatar Gel, Cutar Emulsion, Denorex, DHS Tar, Doak Tar, Duplex T, Fototar, Ionil-T Plus, Medota,  MG 217, Neutrogena TDerm, Neutrogena TGel.

How You Can Help:

  • Create a no-shoes policy.  PAHs are easily tracked into the home, so shedding shoes before entering the home can cut back on exposure.
  • Close your windows.  Coal-tar-treated surfaces continually shed dangerous PAH chemicals, but the air levels are extremely high in the hours and days following a fresh coal-tar application.
  • Don’t trust labels.   Coal tar may not appear on the sealant bucket.  There are dozens of names for coal tar, including RT12, distilled tar, or refined tar. “Tar,” is the word you want to avoid.
  • Do your homework.  An online search of the product name plus Material Safety Data Sheet will reveal the number unique to coal tar as 65996-93-2.
  • Shop where it’s not.   Home improvement chains like Lowes, Home Depot, Ace, or Menards have all banned coal tar sealants nationwide.
  • Know the product.  Find out the exact name of the sealing product your driveway company uses.   Warn neighbors.  Applicators typically try to sell their services to an entire neighborhood.
  • Alert store managers and playground officials of the dangers of carcinogenic coal-tar sealants, and let them know that alternatives containing thousands of times fewer PAHs are readily available.
  • Speak up.  For broad-sweeping protection in your city, borough, or township, consider joining forces with concerned neighbors and lobby your local and state governments to ban the sale and application of coal-tar sealants.  These bans are popping up all over the country, from Washington, DC, to Washington state.  Look at Austin, Texas!
  • Go for gravel.  Consider building a blacktop-free driveway.  Healthier driveways made of gravel or permeable pavers helps reduce harmful motor oil runoff from your property.  That helps keep pressure off of water treatment plants and helps reduce flooding in your community.
  • Make driveway art safe!

Until next week,images

Garbage Girl