[USCC] Compost Digest, Vol 30, Issue 9, Item #3--Response to Frank

[Edo McGowan]

Frank, I think we are talking of the same things here. Perhaps it is is just my perspective and choice of terms. You state-------NO! I MEAN TOXINS - THINGS THAT SHOW TOXICITY. MICROBES, METALS AND ANY ORGANIC COMPOUND THAT HAS SHOWN TOXICITY AND IS IN CONCENTRATIONS TO BE CONSIDERED AT A RISK. 

It thus seems that we then need to define terms so we are not in some sort of senseless semantic argument. I will look at two terms--- TOXIN and POISON.

 TOXIN_____as defined in a scientific context, is a biologically produced substance that, in a dose related context, can causes injury to the health. It is a poisonous substance, especially a protein, that is produced by living cells or organisms and is capable of causing disease when introduced into the body tissues but is often also capable of inducing neutralizing antibodies or antitoxins.

POISON--------as defined in a scientific context is a dose-related substance that can cause injury, illness, or death, especially by chemical means. The basis of this is discussed in the writings of Theophrastus Bombastus von Hohenheim who we know as Paracelsus. 

Given the above, then pathogens would seem to fit into the context of TOXIN AND POISON, and heavy metals into POISONS.

When however one looks at transfer of genetic information, the result can be initially independent of what normally would be considered as a dose response aliquot. Thus small initial numbers can, upon ingestion, soon become very large numbers (10 to the 9th+) by transfer into the ever expanding commensal population of the gut flora. Here I’m discussing pathology caused by the transfer of antibiotic resistance or virulence islands. Thus this fits well into both the definitions of TOXIN and RISK. 

Sjolund et al. (2005) indicated that resistance in the normal flora, which may last up to four-years, might contribute to increased resistance in higher-grade pathogens through interspecies transfer. These authors go on to note that since populations of the normal biota are large, this affords the chance for multiple and different resistant variants to develop. This thus enhances the risk for spread to populations of pathogens. Furthermore, there is crossed resistance. For example, vancomycin resistance may be maintained by using macrolides [Giacometti A, et al In vitro activity and killing effect of uperin 3.6 against gram- positive cocci isolated from immunocompromised patients. Antimicrob Agents Chemother. 2005 Sep;49(9):3933-6. Robertson GT, et al. Vancomycin tolerance induced by erythromycin but not by loss of vncRS, vex3, or pep27 function in Streptococcus pneumoniae. J Bacteriol. 2002 Dec;184(24):6987-7000].

The new WERF paper that discusses finding viable but non culturable  (VBNC) pathogens but only after centrifuging, and then at magnitudes above what standard plate counts show, then raises some very serious issues for composting. I wrote about this a few years ago but it fell on deaf ears. Thus, what the compost industry has been characteristically getting from many POTWs and what has been going on the fields via land spreading is probably just a big unknown. Consequently, the belief that the sewage sludge met standards is probably just a fiction, but then, no one was willing to consider VBNC as an issue---principally because sewer plant operators and regulators are not trained in these areas, yet are responsible for protecting public health. Thus because these people don’t appreciate these issues therefore they never consider them. But that doesn’t mean they don’t exist. How then does your industry that depends on a chain of regulatory compliance know of this---are you, as an industry, actually getting stuff that is meeting standards?

 Francois Vandenesch, et al (2003) in discussing Panton-Valentine leukocidin, and community-acquired methicillin resistant Staph aureus, notes that the genetic transfer is important. Trello Beffa, et al (1996) notes that gram negative rods in high numbers are surviving at themeratures up to 82 C in open air windrows of commercial composting. Other authors, (I do not have the citations right in front of me because I am not at my base), have indicated survival at high temperatures or regrowth of pathogens following cooling. Adrian Unc and others have discussed regrowth. Thus, it is quite possible to see the horizontal transfer of genetic material conferring both virulence and resistance.   

Accordingly, the current U.S. EPA Class B biosolids with its allowed fecal coliform counts of 2 X10/6 per gram may actually constitute a large aliquot when containing MDRB and applied to areas with soil and water movement and animal or vector access. When considering the new WERF study, this limit of 2X 10/6 becomes more worrisome because it is probably a fiction.

Hassen, et al found that, gram-positive bacteria, especially micrococcus, spores of bacilli, and fungal propagules survived, and reached high concentrations in compost. Not only that, "the appearance of gram-negative rods (opportunistic pathogens) during the cooling phase may represent a serious risk for the sanitary quality of the finished product intended for agronomic reuse." (Bioresour Technol 2001 Dec;80(3):217-25).

Thus, I think you and I are actually discussing very similar issues. I want to see composting thrive, where else can you take liabilities of waste products and turn them into assets; but that conversion must be based on modern scientific rationale and not spin or ignorance.

To conclude, the following thought is a statement by the WHO chief of Communicable Disease, David Heymann, before the US Senate hearing on The Spread of Communicable Disease, in 2001.

SOME MICROBES HAVE ACCUMULATED RESISTANT GENES TO VIRTUALLY ALL CURRENTLY AVAILABLE DRUGS. THUS, THESE HAVE THE POTENTIAL TO CAUSE UNTREATABLE INFECTIONS. ACCORDINGLY, SUCH DISEASES MAY HAVE NO EFFECTIVE CURES OVER THE NEXT 10 YEARS UNLESS THERE IS SOME UNCHARACTERISTIC BREAKTHROUGH IN DRUG THERAPY. THEREFORE, IF CURRENT TRENDS CONTINUE, MANY IMPORTANT MEDICAL AND SURGICAL PROCEDURES, INCLUDING CANCER THERAPY, BONE MARROW AND ORGAN TRANSPLANT, HIP AND KNEE REPLACEMENT, AND CORONARY BYPASS SURGERY COULD NO LONGER BE UNDERTAKEN WITHOUT UNDUE RISK OF UNSTOPPABLE INFECTION.

Cheers-----------------Edo