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What San Francisco Found in Their Own Sludge

by: Jill Richardson

Thu Apr 08, 2010 at 15:38:46 PM PDT

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San Francisco HAS done tests of their own sludge in the past, and I've got a copy of the results. Now, the stuff tested isn't the same as the stuff that was given out to gardeners as "compost." But it was one ingredient in that compost, along with sludge from 8 other counties and yard waste.

San Francisco's own tests of its sludge looked for heavy metals, PCBs, dioxins, volatile and semivolatile organic compounds, and pesticides. They didn't look for pharmaceuticals, steroids, hormones, or anything living (bacteria, parasites, etc). And they found some concerning stuff. Details below.

Jill Richardson :: What San Francisco Found in Their Own Sludge
Just a note on these chemicals... what I would like to be able to tell you is where they came from, how they could be prevented from getting into sludge, what their risks are, at what concentrations they are dangerous, and whether or not they are absorbed by plants if they are in the soil where the plants go (and at what concentrations). That is not necessarily information I have though. I did the best I could. I realize these are all very relevant pieces of information. If something is dangerous in the soil but plants don't absorb it, then it could be no big deal (unless there are kids playing in the soil and that makes it a big deal). On the flipside, if plants absorb something and its concentration increases in the plant tissue, that is a VERY big deal. I'm not ignoring the importance of this. Right now I'm just giving you what I could find with the hope that I can learn more and report it soon.

1,2-Dibromo-3-Chloropropane (a.k.a. DBCP)
DBCP is a nematicide (nematode killer) that was used as a soil fumigant until it was banned in 1979 for everything except Hawaiian pineapples. It was banned for Hawaiian pineapples in 1985. It was sold under trade names Nemagon and Fumazone. The maximum amount allowed in drinking water is 2 parts per billion. In 2009 tests, it was present in the sludge from San Francisco's Oceanside facility at 89 ppb.

According to the EPA, the safe level of DBCP is zero and health effects are as follows:

Short-term: EPA has found DBCP to potentially cause the following health effects when people are exposed to it at levels above the MCL for relatively short periods of time: kidney and liver damage and atrophy of the testes.

Long-term: DBCP has the potential to cause the following effects from a lifetime exposure at levels above the MCL: kidney damage and antifertility; cancer.

In California, it is a Prop 65 carcinogen and male reproductive toxin.

Bis(2-ethylhexyl) phthalate (a.k.a. DEHP)
DEHP is used as a plasticizer for PVC plastic (which is used in a lot of packaging materials). The safe amount set by the EPA is zero, and the maximum amount allowed in drinking water is 6ppb. This was found in sludge from San Francisco's Southeast facility at 370ppb. According to the EPA, health effects are as follows:

Short-term: EPA has found phthalate to potentially cause the following health effects when people are exposed to it at levels above the MCL for relatively short periods of time: mild gastrointestinal disturbances, nausea, vertigo.

Long-term: Phthalate has the potential to cause the following effects from a lifetime exposure at levels above the MCL: damage to liver and testes; reproductive effects; cancer.

DEHP is a Prop 65 carcinogen and male reproductive toxin.

4-Isopropyltoluene (a.k.a. p-cymene or p-isopropyltoluene)
Despite documented health risks associated with p-cymene, it's actually allowed by the FDA as a food additive. On one hand, it occurs naturally in a few essential oils, which made me think that perhaps it wasn't a big deal. On the other hand, they must have been testing for it in the sludge for a reason. So far as I can determine, only Maine has regulations for p-cymene maximum concentrations in its drinking water. The limit in Maine is 70 ppb. P-cymene showed up in San Francisco's sludge at 540ppb for the sample taken at the Southeast facility and at 420ppb for the sample taken at the Oceanside facility. For more information, I recommend checking out Toxnet, which documents human health effects of p-cymene.

Dioxins and Furans
Dioxins according to the EPA:

The term Dioxin is commonly used to refer to a family of toxic chemicals that all share a similar chemical structure and a common mechanism of toxic action. This family includes seven of the polychlorinated dibenzo dioxins (PCDDs), ten of the polychlorinated dibenzo furans (PCDFs) and twelve of the polychlorinated biphenyls (PCBs). PCDDs and PCDFs are not commercial chemical products but are trace level unintentional byproducts of most forms of combustion and several industrial chemical processes. PCBs were produced commercially in large quantities until production was stopped in 1977. Dioxin levels in the environment have been declining since the early seventies and have been the subject of a number of federal and state regulations and clean-up actions; however, current exposures levels still remain a concern.

Why Are We Concerned?

Because dioxins are widely distributed throughout the environment in low concentrations, are persistent and bioaccumulated, most people have detectable levels of dioxins in their tissues. These levels, in the low parts per trillion, have accumulated over a lifetime and will persist for years, even if no additional exposure were to occur. This background exposure is likely to result in an increased risk of cancer and is uncomfortably close to levels that can cause subtle adverse non-cancer effects in animals and humans.

What Harmful Effects Can Dioxin Produce?

Dioxins have been characterized by EPA as likely to be human carcinogens and are anticipated to increase the risk of cancer at background levels of exposure.

First, here are the totals found for dioxins:
Total Tetradioxin: 30.4ppt at Southeast, 54.7ppt at Oceanside.
Total Pentadioxin: 250ppt at Southeast, 394ppt at Oceanside.
Total Hexadioxin: 127ppt at Southeast, 171ppt at Oceanside.
Total Heptadioxin: 962ppt at Southeast, 1500ppt at Oceanside.

And here's what came up for individual specific chemicals:
1,2,3,6,7,8-HEXACHLORODIBENZO-P-DIOXIN: Found in the Southeast sludge sample at 20.1 parts per trillion (ppt) and in the Oceanside sludge sample at 27.7ppt.

1,2,3,7,8,9-HEXACHLORODIBENZO-p-DIOXIN: This was found in the Oceanside sludge sample at 13.3ppt. Florida regulates the amount of this in their drinking water, permitting no more than 0.25ppt.

1,2,3,4,6,7,8-HEPTACHLORODIBENZO-p-DIOXIN: This was found at 497ppt in Southeast sludge and at 834ppt in Oceanside sludge.

OCTACHLORODIBENZO-P-DIOXIN: This was found at 4750ppt in Southeast sludge and at 5900ppt in Oceanside sludge.

The remaining dioxins tested below the detection limit.

Totals for furans:
Total tetrafuran: 76.4ppt at Southeast, 68.5ppt at Oceanside
Total pentafuran: 84.5ppt at Southeast, 69.2ppt at Oceanside
Total Hexafuran: 122ppt at Southeast, 114ppt at Oceanside
Total Heptafuran: 246ppt at Southeast, 283ppt at Oceanside

2,3,7,8-TETRACHLORODIBENZOFURAN: This was found at 4.53ppt in sludge samples from Southeast and at 3.26ppt in sludge samples from Oceanside.

1,2,3,4,6,7,8-HEPTACHLORODIBENZOFURAN: This was found at 112ppt in sludge samples from Southeast and at 123ppt in sludge samples from Oceanside.

1,2,3,4,7,8,9-HEPTACHLORODIBENZOFURAN: This was found at 13.7ppt in sludge samples from Southeast and at 16.4ppt in sludge samples from Oceanside.

OCTOCHLORODIBENZOFURAN: This was found at 534ppt in sludge samples from Southeast and at 605ppt in sludge samples from Oceanside.

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Quite an interesting gang... (4.00 / 2)
Keep the info coming!

In the next installment, (4.00 / 2)
metals, I hope.

[ Parent ]
yeah (4.00 / 2)
I have those #s, didn't do my homework on them. For all I know (and hope) the levels of metals in the sludge is harmless.

"I can understand someone from Iowa promoting corn and soy, but we are not feeding the world, we are feeding animals and soft drink companies." - Jim Goodman

[ Parent ]
I'm feeling better and better about (4.00 / 3)
horse shit every day.....

Normal people scare me.... But not as much as I scare them.

As long as... (4.00 / 2)
...they don't hang around places like KinBuc Landfill or Bayonne Barrel & Drum, &c!


[ Parent ]
PCBs (4.00 / 2)
I know a heckuva lot about PCBs, and I never realized many of them are in the dioxin group.

Us organic types have know this for years (4.00 / 3)
which is why we have NEVER allowed sewage sludge in organic

More questions than answers (4.00 / 1)
Was this a single "grab" sample?  When was it collected?  
What proportion of the finished product comes from the sludge represented by this sample?
What subsequent treatment/processing is done to the sludge after this sampling, but before packaging?
Are these results reproducible?  (I'm especially skeptical of the DBCP and DEHP results.  Phthalates are notorious for a high rate of false-positives, and DBCP isn't a common sludge contaminant.)

As for the dioxins & furans, you should find some comparable testing for finished compost made without sewage sludge, and see if there's a significant difference. In any case they are not much of a threat in soil at these concentrations, and they are not taken up by plants (partly because they have extremely low mobility).

The big question with any test result is, so what?  Meaning, are these concentrations high enough to cause a potential health risk through any likely route of exposure?  This is where it gets really tricky, because most of the regulatory levels are based on drinking-water exposure, which obviously doesn't apply here.  By mixing this stuff with other organic matter and composting it, the concentrations are likely to decrease even further, and then it gets spread onto or mixed into soil.  Dermal contact would be a concern if the concentrations were high enough, but not at these "trace" levels.  SO it's either direct ingestion of soil - possible but unlikely - or plant uptake.  Some chemicals, like dioxins, are nearly immobile in soils and are not taken up by plants; others (like phthalates) are biodegradable in biologically active soils, so the concentrations tend to diminish fairly rapidly.

Bottom line, these results do not indicate the sludge is "toxic" as alleged by OCA.  (It may or may not be, but these results don't settle the question.)  If this is really all they found - no PAH? - it looks like pretty good stuff to me.  Wish I could get some for free!

Can I ask who you work for (4.00 / 2)
and what your relationship is to the sewage industry?

The vast majority of sludge used in the "compost" came from other counties, not San Francisco. And sludge from those 9 counties was 1/3 of the total make-up of the "compost."

"I can understand someone from Iowa promoting corn and soy, but we are not feeding the world, we are feeding animals and soft drink companies." - Jim Goodman

[ Parent ]
contaminant source (4.00 / 1)
We've asked ourselves where some of these contaminants come from. I just had a disturbing thought - I wonder how much of it is excreted from our own bodies.

[ Parent ]
Maybe you can... (0.00 / 0)
...point us to an instance of where just one single grab sample showing such results would differ so wildly and vastly enough from a composite sample so as to render these particular findings of no concern?

And for that matter, do you have any evidence that these results came from just one grab sample (why would SFPUC have released the results without mentioning other findings, and if they did come up with these results based just upon one grab sample why wouldn't they have followed up?), or are you just trying to discredit this information by insinuation?

Tell you what, there's an easy way to end this controversy.  Tell your bosses or your PR rep, whatever, to come on out from behind the recent rash of pseudonymous new users showing up here, arguing semantics and whatnot, and prove once and for all that there's nothing to be concerned about here.

[ Parent ]
Sludge in Australia (4.00 / 1)
You might be interested in this:

Organochlorine pesticides are called 'persistent' for a reason. - Environmental Health News.

Despite having phased out the use of organochlorine pesticides in the 1990s, the chemicals continue to be detected in sewage sludge in Australia, according to a study that is the first to examine this issue on that continent.

The findings are important because they show that the chemicals can linger long after they have been banned. As in many countries, the sewage sludge - the solid part of processed sewage - is often recycled and used to fertilize crops. This suggests the pesticides are still  present in agricultural areas of Australia.

The low levels now found in the sludge are in most cases below government regulatory standards and international policy agreements.

Organochlorine pesticides are a class of chemicals that were used to control insect pests since the 1940s. They were mostly phased out of use in the last part of last century due to their longevity, a trait that made them effective for long term pest control, but also increased concerns of potential health outcomes such as cancer in humans and ecosystem disruption.  The chemicals are still detected in people even though have been phased out in many parts of the world. Some countries still use them - mainly DDT - to control mosquitoes that carry malaria.

In this study, the investigators gathered published data about the amounts and sources of the chemicals found in sewage sludge around the world, including the United States, Canada, China and several European countries. They also obtained similar data gathered from five Australian waste water treatment plants between 1995 and 2006. They analyzed and compared the amounts and sources of several organochlorine pesticides - aldrin, chlordane, dieldrin, heptachlor, hexachlorbenzene and DDT - in the sewage sludge over time and among countries.

Researchers first detected the suite of chemicals in sludge in the 1980s and have monitored them since. In some cases, it has taken as long as 15 years after the chemicals were phased out for levels to drop below detection.

Of the organochlorine pesticides monitored, DDE - the breakdown metabolite of the insecticide DDT - and dieldrin are still found at detectable levels in some countries, suggesting it takes even longer for these two compounds to break apart. In Australia, low concentrations of dieldrin and chlordane were detected in sewage sludge for up to 10 years after the pesticides were no longer being used.

These are important finding for countries continuing to use, or that have only recently discontinued use, of organochlorine pesticides. The authors indicate that sewage sludge may not be the only recyclable media that may still contain these persistent pesticides.

While the chronic health effects from low level and long term exposure are poorly characterized, the presence of these persistent chemicals in sewage-based fertilizers will be an environmental factor to consider in future research on the health of people who live in agricultural communities.

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