Here's the response I received from the San Francisco Public Utilities Commission about their safety testing of their sludge compost that was given away free to San Francisco gardeners:
Thanks for your inquiry about the San Francisco Public Utilities Commission (SFPUC)'s Biosolids Compost Program. As you have mentioned on your email, the test results for the biosolids compost given away in fall 2009 posted online are the same reports that are printed and made available at each of our giveaway events. Repeated test results have shown the metal concentrations in the biosolids compost given away by the SFPUC were comparable to the compost found in a gardening store. The testing standards and test results must meet compliance standards set through the EPA's Part 503 Rule.
The nine pollutants regulated by EPA's Part 503 Rule were selected after a 1984 Risk Assessment that included more than 200 inorganic and organic pollutants. In order to responsibly regulate a pollutant certain information must be available in order to conduct a risk assessment. Such information includes toxicity, fate and transport (from within the biosolids matrix preferably), reasonable routes of exposure, and the dose to which the subject would be exposed. For those 200 pollutants, a hazard quotient (HQ) was calculated which is a measure for potential adverse effects to public health or the environment. Some 25 pollutants had a HQ of greater than one, which called for a full effect characterization through a comprehensive risk assessment. Fourteen pathways of exposure were evaluated with numerous conservative assumptions built in through which it was ensured that all reasonably anticipated adverse effects were captured. Ten pollutants were determined to be necessary to regulate (later reduced to nine in 2001).
The SFPUC is currently undertaking a comprehensive test of our biosolids compost, including heavy metals and pollutants of concern. In an effort to be completely transparent, these tests go above and beyond any current regulatory requirements for either biosolids compost or what is readily available as soil amendment from commercial gardening stores.
Our test results will be available to the public as soon as they are completed. I hope this information helps you in the meantime. Please feel free to contact me if you have any questions or need additional information.
I'd like to call out a gaping flaw that appears in the EPA's method of determining what to regulate in sludge as it is described here. There are literally tens of thousands of chemicals that can show up in sludge. Testing a mere 200 of them can hardly guarantee the safety of sludge. And the proof for that is in the pudding - when Andy McElmurray applied sewage sludge from Augusta, GA on his fields where he grew crops to feed his cows, the cows died. McElmurray went out of business. And milk was sold in the supermarket with high levels of thallium - a rat poison - in them. Thallium is NOT one of the chemicals that the EPA deemed hazardous enough to regulate. And it's not even a common chemical found in sludge, to the best of my knowledge. But that doesn't mean that it's never found in sludge or that the regulations keep us safe from it.
On another note, I'm encouraged that SFPUC promises to make its results fully available to the public once they are complete. However, it's been MONTHS since they supposedly initiated this testing. How long does it take? And what are they doing that requires so long? Shopping around for a lab that gives them the results they want? Sending back positive results for re-testing until they come back negative? Or, on the other hand, are they really doing the world's most complete testing of their sludge compost to ensure that it's 100% safe for applications in gardens where food is produced? I hope it's the latter. |
