To: Ventura County Agricultural Commissioner
To: Ventura County Health Department
To: VCSD
To: Co BOS
To: Rob Roy, VCAA
Fm: Dr Edo McGowan
12-10-06
Re: Sewage effluent and the recent Toco Bell outbreak of food borne illness
The health hazards associated with pathogens in sewage effluent have been well reported in the literature. Dozens of
known enteric pathogens may be present in the treated wastewater. Sewer plants are not designed to properly treat
incoming toxins or pathogens. In fact, sewer plants offer a medium for the mixing of pathogens that might otherwise
seldom come together. Antibiotic resistance amongst incoming pathogens is rapidly advanced. The sewer plant
augments this sharing of genetic material conferring resistance and virulence. Emerging infectious diseases are
increasing, and at least one new enteric pathogen has been discovered every year over the past decade.
Several newer papers discuss these issues. But existing and now badly antiquated standards continue in their failure to
recognize this. The recent papers by CA kinney of the USGS demonstrate that both antibiotic resistant pathogens and
levels of pharmaceuticals able to maintain resistance are found in discharged wastewater. Kummerer out of Germany
has been writing about this for several years now. Kate Brown out of New Mexico also reiterates this. Amy Pruden out of
Colorado notes that free DNA is abundant and its re-uptake will confer antibiotic resistance. Higgins and Murthy out of
WERF write on the failure of standard lab tests to note viable but non-culturable (VBNC). Thus these all point to the fact
that the standards now fail to adequately protect the population. Thus if there is infiltration of wastewater into areas
where ag wells can pull this water and thus irrigate, the issue is one that can not be ignored or see regulators throwing
up their hands saying the system is complying with standards. We can always exceed bad standards.
Unfortunately, the principal agency responsible for this area (US-EPA) has included no pathogen risk assessment within
the controlling regulations. Standards set for health have been set for a mere pittance of toxins that are found in
wastewater. Additionally, pathogens are assumed to be controlled by technology based standards, but not through
actual health risk assessments. This concept of technology based controls has been turned on its ear by the Higgins &
Murthy paper. Marker or indicator organisms employed in these tests are of limited usefulness, especially when
considering the rapid emergence of new pathogens, transfer of genetic information conferring virulence, and antibiotic
resistance and VBNC states. The lack of or limited usefulness of contained data within and upon which the regulations
are set is pointed out within the NAS/NRC 2002 report on land applied sewage sludge. Much of these data also apply to
released effluent. In essence, the NAS/NRC indicated that the data were old and had fallen considerably behind the
advancement of pathogens. In addition, the NAS/NRC, in that report, commented on the lack of data on off-site
movement as well as antibiotic resistance. Consequently compliance with these regulations does not assure protection
of public health.
This then brings into question the current paradigm on infection and its dose response to a certain load of a particular
pathogen, i.e., ID and LD 50s. Lateral transfer of mobile genetic elements conferring resistance is not considered in this
old paradigm. With the prodigious capacity for the gut bacteria to multiply, once the lateral transfer has taken place,
very small original numbers---well below the old paradigms can be multiplied into impressive numbers. Since viruses and
phages are also involved, their capacity to multiply, which dwarfs that of bacteria, must also be included. Thus there is a
need for a new paradigm; unfortunately, the regulatory community seems not to recognize this. When one considers the
multiplication within sewer plants and also within their byproducts, disbursement into the environment, the transfer to
background organisms, hence to man and his animals, then the remultiplication within commensals of the gut, the
emerging picture is worrisome.
Thus the use of the old paradigm such as ID-50 without considering the impact of the above is essentially a meaningless
exercise that grossly under represents reality. The issue of food borne disease is now a hot topic. The residuals or
adverse sequelae and morbidity of some of these pathogens are well demonstrated and frankly frightening. Once
ingested, the plasmids may be transferred to normal flora, and subsequently to pathogenic bacteria found in humans or
animals, making later treatment with particular antibiotics ineffective. Also one must consider transfer of genetic
information from these organisms to more robust organisms as highlighted by Sjolund et al. (2005) [1] indicating 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
[2].
Walsh (2003) [3] notes that resistance to antibiotics is not a matter of IF but one of WHEN. In the case below, the pre-op
patients were free of colonization with resistant bacteria. But what would be the result if there had been inadvertent
acquisition of resistance from environmental contamination such as through sewage effluent used for irrigation?
Schentag, et al. (2003), in Walsh, followed surgical patients with the subsequent results. Pre-op nasal cultures found
Staphylococcus aureus 100% antibiotic susceptible. Pre-op prophylactic antibiotics were administered. Following
surgery, cephalosporin was administered. Ninety percent of the patients went home at post-op day 2 without infectious
complications. Nasal bacteria counts on these patients had dropped from 105 to 103, [what unit?] but were now a mix of
sensitive, borderline, and resistant Staphylococcus sp. By comparison, prior to surgery, all of the patients’
Staphylococcus samples had been susceptible to antibiotics. For the patients remaining in the hospital and who were
switched on post-op day 5 to a second generation cephalosporin (ceftazidine), showed bacterial counts up 1000-fold
when assayed on post-op day 7 and most of these were methicillin resistant Staphylococcus aureus (MRSA). These
patients were switched to a 2-week course of vancomycin. Cultures from those remaining in the hospital on day 21,
revealed vancomycin resistant enterococcus (VRE) and candida. Vancomycin resistant enterococci infections can
produce mortality rates of between 42 and 81%.
Accordingly I feel that whatever conclusions have been drawn from Gale’s paper on microbial risk assessment, upon
which EPA relies, would understate the risks as the decay curves would be confounded by the above. Further, at least
in the U.S. the constant reapplication of sewage sludge or irrigation with reclaimed or infiltrated effluent, especially the
common practice when speaking of land applied biosolids that greatly exceed agronomic needs---i.e., sludge dumping
and not true agriculture---would vastly corrupt the estimates made by Gale. Additionally, the material is not easily
confined to the areas where it was applied as the Sugar Creek study [4] amply demonstrates. The Sugar Creek study is
thus applicable to release of "treated" sewer wastewater into local drainages.
Thus, in the case of Gale's work upon which EPA has relied, is in essence no risk assessment here, merely an elegant
argument that may appeal to the unenlightened and that tends to promote the concept that sewage plants actually work
to protect the public health.
The tragic issue here, is that pathogens do not respond to what is politically correct or technically expedient.