posted January 9, 2006
The land application of sewer sludge (biosolids) is not the benign activity proffered by some. First, the current standards under which biosolids are produced and land-applied are not only antiquated but also seriously dangerous. I will get into this momentarily. Contrary to popular myth, many serious pathogens (bacteria, viruses, protozoa, and helminths) escape the low-level disinfection used under current standards for producing biosolids. Further, biosolids contain not only antibiotics and heavy metals, but also myriad other toxins and endocrine disrupters. These materials combine to further augment the existing antibiotic resistant pathogens found in biosolids. In fact, the very process of making biosolids generates antibiotic resistant pathogens. The World Health Organization recently stated that antibiotic resistance has reached the point of a global health crisis.
Further, by land application of biosolids under current standards, there is ample opportunity to allow for the intermixing of genetic material necessary at the macro and micro levels to augment a pandemic, such as bird flu. We know, for example, that Canadian geese now carry and disburse antibiotic resistance. How did these birds obtain the genes that confer resistance and thus transmit it through their feces? These birds are often encountered on sludge-applied farmlands. We also know that other forms of wildlife and internationally migratory birds frequent these areas. There is virtually no way they can be consistently excluded. Thus the opportunity to find the necessary mixing of genetic information to cook up entirely novel pathogens through enter-species and entra-species mixing is highly augmented by land application of biosolids.
Now about the standards. First, the indicator bacteria used by the standards and regulatory community are those that are easily killed. This gives a skewed view and a false sense of security. Biosolid standards allow for the survival of 2 million viable but otherwise easily killed coliform bacteria per gram of sludge. The size of a gram is about the same size as a small sugar cube. If you crushed a sugar cube, you would see a pile of sugar grains - and this looks like a lot of grains. The allowed number of live bacterial indicators that remain after biosolids are processed and land applied, however, dwarfs that number. There are 454 grams in a pound and 2000 pounds in a ton. The average loading of biosolids may be in tons per acre. If you do the math, the result is a mind-boggling number of bacteria, viruses, and other pathogens.
The viability or survival of these indicators is much longer that one would suspect - sometimes into the next growing season. In many instances, biosolids are top-dressed on pastureland. Cattle can be returned to graze on this pasture after 30 days. Thus what of the more robust pathogens that are ignored by the current standards and low-level disinfection? This also says nothing of the amount dirt and contaminated crop consumed by cattle as they graze. Cattle consume large amounts of dirt as they graze. This also says nothing about the dog that runs across the field and then enters your car and home. This is not an adequately controlled activity when the risks are considered.
The risk of transfer to you under these circumstances, considering the potential failure of an antibiotic to control a serious pathogen, is too much to dismiss. Actually EPA has no real health risk data for pathogens, let alone having done health risk assessments for antibiotic resistance. Recent data in the medical literature indicate that once within the bacteria of the gut flora, these resistant genes can remain as long as four years, assuming no other antibiotic usage. Not only that but because of the large number of gut bacteria and phages, the chance for genetic shifting and thus development of new strains for resistance, hence pathogens becomes thus augmented.
But the point I want to make is this. If the easily killed indicators survive in such large numbers, then what about the more robust pathogens that would require medium or high-level disinfection. Since they are more robust, they are likely to be found in much larger numbers. Nonetheless, the current standards ignore this logic. Sewer plants can not attain medium to high-level disinfection - the level needed to really do the job. Another critical item ignored is the fact that the levels of antibiotic resistance are increasing and biosolids are a serious source of emerging antibiotic resistant pathogens. The regulators are ignoring this aspect and thus your health is at risk.
To get some idea of this I sought, through a Freedom of Information Act request, information from U.S. EPA on its progress of looking at biosolids and antibiotic resistance. The agency has yet to answer the request that was sent to it and acknowledged in February of last year. I did a web based search of the EPA web site and there was no information when the key words "biosolids + antibiotic resistance" were combined. This looked at the entire EPA web site. Here are those results.
We have searched the entire EPA site and found the following results. You may also return to searching for the same terms within Environmental Sciences.
No matches found for high level disinfection + biosolids; 494732 files searched.
No matches found for plasmids + biosolids; 494732 files searched.
No matches found for transposons + biosolids; 494732 files searched.
No matches found for mobile genetic elements + biosolids; 494732 files searched.
No matches found for virulent pathogens + biosolids; 494732 files searched.
No matches found for antibiotic resistance + biosolids; 494732 files searched.
No matches found for antimicrobial resistance + biosolids; 494732 files searched.
Results for the same terms within Environmental Sciences also produced nothing.
EPA was told to look at resistance by the National Academy of Sciences back in 2002. It evidently has done little if anything in this area. Actually if it did look long and hard at this subject, it would also have to admit it has been putting the nation’s citizens at considerable risk by promoting land application of biosolids. Interestingly it, as of late, is no longer promoting the land application of biosolids. For a clientele-captured agency (an agency that protects not the citizens but the industry it was developed to regulate) it has failed in its duty of protecting the public.
Dr. Edo McGowan
Carpinteria, Calif.
edo_mcgowan@hotmail.com
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