| 
|
The following is a response to Henry Vere’s article, “As Pure as the Fallen Snow,” appearing on page 24 of the May/June issue of Onsite Water Treatment. To view the original article, please visit www.onsitewater.com/ow_0705_as.html.
By Edward McGowan
I keep hearing that reclaimed wastewater is as pure as the driven snow, as if it is coming out of a snowmaking machine. Some say this is cleaner than irrigation water, but what is clean? Takashi Asano, P.E., discusses bacteria and notes that, at least in California, this is 2.2 coliform count per 100 milliliters. But is that really true, or is that what the lab tests show, and how accurate are these lab tests?
Well, it turns out that these tests may not be very reliable or accurate. The tests in question use the most probable number (MPN). That system may not fully consider what Frank Pecarich, a retired soil scientist from the US Bureau of Reclamation, noted as a stealth condition within bacteria. This stealth condition is termed viable but non-culturable (VBNC), and the typical lab test does not recognize this. There are a variety of these stealth conditions besides VBNC.
The Water Environment Research Foundation (WERF) did some recent studies on VBNC and in its studies confirmed earlier studies that noted that standard tests understated actual conditions by several magnitudes [see: Examination of Reactivation and Regrowth of Fecal Coliforms in Anaerobically Digested Sludge, WERF Report: Biosolids and Residuals (03-CTS-13T), by M.J. Higgins and S. Murthy].
Additionally, the lab tests dictated by the standards are run on vegetative bacterial indicators that require only low-level disinfection for a kill—but the standards do allow some of these to survive. This logically raises questions about pathogens coming through that are more robust—those requiring high-leveldisinfection. High-level disinfection is required for enteric pathogens as found on semi-critical medical devices, such as scopes inserted into the lower gastrointestinal tract. If that high level of disinfection is needed to control such pathogens, then how is it that low-level disinfection, as found used for sewer plants, can be considered as adequate? Thus, from a logical point, if the indicators are surviving (ignoring for a moment the VBNC), then one might conclude that the more robust will survive in greater numbers. Additionally there are different systems for survival that are not considered by the standards, and some of the newly emerging infectious diseases are also not considered. All this raises a considerable series of legitimate questions on how current standards are protective of public health. Then, on top of that there is the transfer of genetic information from dead pathogenic bacteria into live non-pathogenic bacteria, thus rendering them pathogenic. This is a well-known fact; it was first demonstrated in 1928 by Fred Griffith.
The standards also use a technology-based (not actually tested) viral level that is assumed to parallel the bacterial indicators. These technology-based shadow systems are based on an assumption that if the water has a certain clarity (reduced turbidity) and the coliform counts are under a certain number, then the virus levels will be acceptable. First, such shadow systems assume that humans and machinery never experience errors. Second, this system assumes that the VBNC are non-existent. Third, this system assumes that there is a direct correlation between turbidity reduction and pathogenicity, but that parallel is elusive and actually has not been scientifically documented. This elusiveness has been noted by the California Department of Health Services. Fourth, if the load of virus is reduced by 5 log units from whatever starting number, by legal definition (not necessarily reality) there are by definition no viruses.
Fifth, the data assume responses in a population with totally competent immune systems. We know, in fact, that a substantial portion of the population does not have a competent immune system. This would include the very young, the very old, those on immunosuppressive medications for cancer or an organ transplant, those with autoimmune diseases, diabetics, those with HIV/AIDS, pregnant women, and so on.
Additionally, none of the reflection in the article really discussed the transfer of genetic material conferring antibiotic resistance or virulence. This is not a criticism of the paper but merely an observation. We have run some bacteriology tests on tertiary treated disinfected recycled Title 22 water and found multidrug-resistant bacteria. A 2004 WERF paper that studied sewer plants from coast to coast noted problems not only with reclaimed water but with the standards as well. The WERF study noted that plants in their production of recycled water actually met standards somewhere between 33% and 66% of the time. Giardia cysts were found in 84% of the final recycled/reclaimed water samples. Enteric viruses were detected in 31% of the final effluents of two-thirds of the studied facilities and Cryptosporidium oocysts in 71% of the final recycled/reclaimed effluents. Viable Cryptosporidium oocysts were detected in 30% of the final recycled/reclaimed effluents in two-thirds of the tested facilities. The study concluded that the standards did not protect public health.
The contained pathogens and their resistance can be transferred to people from surfaces; this is well documented. It is also recognized that the background resistance is rapidly building in many areas. The current issue of Emerging Infectious Diseases (August 2007), a technical journal put out by the Centers for Disease Control (CDC), notes that the level of community acquired methicillin Staphylococcus aureus (CA MRSA) increased four-fold between 2001 and 2005. Some say that is just part of progress and we will need to live with it because the economics are just not there to effectively deal with the issue. Actually, that may be an accurate appraisal. As noted by Pecarich, politics plays a major role in this decision. From an enterprise position, that stance of shifting costs makes good fiscal but poor economic sense. These shifted costs are classically called externalities.
Additionally, by adopting that enterprise position, we see the damages shifting onto other sectors such as through increased health care costs, which are accelerating. The added costs for dealing with antibiotic resistance in the hospital setting, although substantially adding to the overall bill, is not just related to the patient directly impacted with a resistant infection. In our teaching hospital, we have been using vancomycin since about 2003 as a prophylactic pre-op on a regular basis for certain procedures precisely because the levels of community-acquired and hospital-associated resistance had rocketed. Vancomycin was once the drug of last resort and had been held by CDC in that status—not any more!
This has a ripple effect. From purely another economic perspective, the drug makers are slowing down their efforts on developing new antibiotics. Resistance to antibiotics in the levels of serious pathogens now reaching out into the community is advancing. We are seeing the development of cross-resistance between various types of antibiotics. Thus the pathogens are becoming harder to control. Drugs still in their initial clinical trials are seen encountering resistance or cross-resistance. These new drugs, after millions being expended, are then withdrawn, and many have not even entered the marketplace. The drug-makers are now less enthusiastic about new drugs in this field. These are drugs for acute symptoms. That is not where the money is. The money is in long-term medications for chronic disease—something you will need for the rest of your life, not for a mere two-week course.
What are the chances for inadvertent acquisition of resistance from environmental contamination such as through reclaimed water? Pat Rusin and Chuck Gerba conducted research, as reported in the Journal of Applied Microbiology, about the passage from finger to mouth of pathogens found on typical household objects. This relates directly back to artificial snow. In the snow, how does one pull off one’s glove—bite on that snow-soaked glove and pull it off? Others have documented mechanical vectors for pathogens. What about boots, poles, etc.? Most municipal parks that use reclaimed wastewater have signs up saying not to drink, but blast through some powder coming down a slope and one is often bathed in a fog of snow.
These bacteria are thus able to colonize niches in humans, through inhalation and ingestion. Once ingested, the genetic material may be transferred to normal flora and subsequently to pathogenic bacteria found in humans making later treatment with particular antibiotics ineffective.
We, as humans, have fecal veneers on us; this is natural. Women are taught to wipe away from the perineum so as to limit the deposition of a fecal veneer near the urogenital area. The ability of bacteria to colonize niches and orifices of the body is well documented. If those colonizing bacteria are also antibiotic resistant, then this may represent an increased health care risk.
Also, one must consider transfer of genetic information from these organisms to more robust organisms. As reported in the September 2005 issue of Emerging Infectious Diseases, the resistance is transferred to the normal flora, which may last up to four years. Additionally, these might contribute to increased resistance in higher-grade pathogens through interspecies transfer.
The 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. Erythromycin is one such macrolide. Erythromycin is very resistant to sewage treatment and also accumulates in the environment with reclaimed water—or blown artificial snow.
This then brings into question the current paradigm on infection and its dose response to a certain load of a particular pathogen (i.e., infective dose/50s—the dose will cause 50% of the people to develop an infection?). In medicine there are rules of thumb. A certain load (number) of bacteria is needed to cause infection. Lateral transfer of mobile genetic elements conferring resistance to the human flora is not considered in this old paradigm. With the prodigious capacity for the gut bacteria to multiply, once the lateral genetic transfer has taken place, very small original numbers—well below the old paradigms, can be multiplied into impressive numbers. Do the math—take a division rate of 20 minutes for bacteria in nice warm conditions with lots of nutrients—like inside your body. That is three doublings each hour—run that out for 24 hours and see what you get for an answer—impressive, isn’t it?
So, assuming that one does get a bug, what is the downside? A 2003 study followed surgical patients with the subsequent results. Pre-op nasal cultures found Staphylococcus aureus 100% antibiotic susceptible (i.e., not resistant). Pre-op prophylactic antibiotics were administered. Following surgery, cephalosporin was administered. Ninety percent of the patients went home at post-op day two without infectious complications. Nasal bacteria counts on these patients had dropped from 10/5 to 10/3 but were now a mix of sensitive, borderline, and resistant Staphylococcussp. By comparison, prior to surgery, all of the patients’ Staphylococcus samples had all been susceptible to antibiotics. For the patients remaining in the hospital and who were switched on post-op day five to a second-generation cephalosporin (ceftazidine), these patients showed bacterial counts up 1,000-fold when assayed on post-op day seven and most of these were methicillin-resistant Staphylococcus aureus. These patients were switched to a two-week course of vancomycin. Cultures from those remaining in the hospital on day 21 revealed vancomycin-resistant Enterococcus and Candida. Vancomycin-resistant Enterococci infections can produce mortality rates of between 42% and 81%, as reported in Antibiotics—Actions, Origins, Resistance, by C. Walsch (March 2003). Vancomycin is not a benign drug. The adverse reactions include death.
Since viruses and phages are also involved, their capacity to resist sewage treatment and then 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 pathogen 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 the human flora, the emerging picture is worrisome.
Further, there are opportunities and interrelationships between microbes that can degrade antibiotics (e.g., antibiotic-resistant bacteria) and those that can degrade metals as well as pesticides that are already found in reclaimed water. In many cases, the involved cellular machinery is the same or similar, i.e., a duality.
This duality may have some interesting synergistic survival advantages for the microbes but bad-for-human-health effects when considering reclaimed water is made into snow. Thus, are we shooting ourselves in the foot?
So while snow machines may generate profits for one sector, they may generate considerable costs in others. If the standards that control these enterprises that depend on reclaimed water are truly reflective of health and environmental impacts, that would be one thing and we could make choices. But the standards are based on science that is way behind the curve and is old. That is just simply dangerous in today’s environment.
Edward McGowan has a degree in medicine and a doctorate related to water-quality control.
OW - November/December 2007 |
