|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.