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Published online 17 December 2008 | Nature | doi:10.1038/news.2008.1310
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Drinking water contamination mapped
Wide-ranging survey reveals low levels of some drugs and pesticides in US tap water.
The most comprehensive survey so far has found a slew of drugs, personal care products, pesticides and other contaminants in drinking water being delivered to millions of people across the United States. None of the compounds appeared at levels thought to be immediately harmful to human health.
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Note how writer Naomi Lubick stresses low levels of each single pollutant and mentions neither differences in individual susceptibility nor mixture-effects (additive, synergistic) nor hormesis (ultra-low-dose effects). In other words, she's reporting the findings while using rhetoric which belittles those findings. The rationale which guides her choice of words and concepts is widely used in "regulatory" processes and in most news articles about pollutants.
There are several issues that the previous author (Binstock) notes that may bear expansion. One is the biomagnification of these materials within the food web. Another is the impact of these materials on biofilms that are found in drinking water pipes. While the regulatory agencies may be finding small amounts in the environment----say within standing water, the issue here is that standing water usually carries low levels. Accumulation in other systems must be considered. The typical difference in concentrations found in between standing water and say the concentrations within sediment at the bottom of a lake can be several magnitudes. This impacts the food web. Additionally, many of the materials will bioaccumulate in crop tissue, whether within the fodder crops fed to food animals or in direct line to the human food chain such as root crops. When we looked at pesticides decades ago when I was a grad student in toxicology at Davis, we noted that a good way to clean up some contaminated soils was to plant carrots. Many of these economic poisons had endocrine disrupting impacts. These contaminants wind up in the fatty tissue and are later released during lactation, either human or animal. They also work in such small concentrations that impacts on embryogenesis are a concern. I recently attended the international water and pharmaceuticals conference at Research Triangle Park. While many of these issues were discussed, some did not seem to reach into the final conclusion, so it may not be merely an absence on the part of the regulatory community but a reluctance to discuss that is far wider spread. As to biofilms. The water flowing through the drinking water pipes of America has the potential to have an adverse impact on public health. As a colleague noted----?We are faced with a problem: how to address the fact that pharmaceuticals are now found widely in the environment and even in the municipal drinking water supply of many communities. How should we understand this finding? How do we explain it to the public? What steps need to be taken to understand the impact of pharmaceuticals? What steps need to be taken to protect the environment and the drinking water supply that are now confronted with small doses of very powerful drugs? As the population ages, and as more people take long term courses of medications, we can only anticipate that with current technology, the levels of pharmaceuticals in the environment and drinking water supply will continue to increase.? There is a need to look at the impact of pharmaceuticals found in the water and the subsequent synergistic impact upon antibiotic resistance within biofilms [1] that form within the potable water delivery systems. The work of Amy Pruden [2] demonstrates that antibiotic resistant genes (ARGs) are not affected by the levels of chlorine presently utilized by drinking or wastewater treatment systems. Further, this same work demonstrated that the typical filtering systems employed by treatment works did not select-out these genetic fragments. Thus both pathogens and their genetic fragments as well as pharmaceuticals may be able to impact biofilms found within water pipes. Since these biofilms do shed, this is an increased risk to consumers. Because sewer plants are unable to effectively deal with pathogens, their genetic fragments or through-put of pharmaceuticals, the public needs to be aware of these short comings. It is generally established that about 95% of the pharmaceuticals entering the sewer plant can not be controlled. The pharmaceuticals enter the wastewater treatment plant and exit intact or as metabolites, in either the effluent or the sewage sludge biosolids. To give you some appreciation for the combined result of the above dynamics, consider the following. The college spends two weeks each semester of the introductory medical microbiology class dealing with the microbiology of water. One of the students in the medical micro class, who worked part time at a local outlet of a national pharmacy brought in some presumed sterile water that was used to mix prescription drugs. This water was run for bacterial content and showed multi-antibiotic resistance to 11 of the 12 antibiotics in our Kirby Bauer suite. We thought that this must be contamination so the test was repeated several times with the same result. It was not contamination. We surmised that a biofilm had developed within the equipment. The source was the local potable supply, and thus was not suspected. Remember, this was water used to mix prescriptions. If the city had increased the residual chlorine, this might have prevented the issue to some extent but one must remember that ARGs are not impacted by current levels of chlorine and with shedding biofilms, the risk may remain. Also, one must appreciate the import of the work by Matt Wook Chang [3] on the effect of chlorine on enhancing virulence factors. Thus it is conceivable that added chlorine may also increase virulence. How does this all combine to impact the immune system? Assuming a competent immune system may, in today's world, be a fallacy. What of chlorine resistant pathogens? How do these impact the immune system's dependence upon hypochlorite, especially if one is given a bacteriostatic antibiotic? There seems to be a tendency amongst groups within industry as well as the regulatory community to down-play the inability of sewer works to effectively deal with pharmaceuticals. It would be helpful for the groups as a whole to acknowledge that most municipal wastewater treatment plants as currently designed and operated are not capable of removing a significant level of pharmaceuticals and also that many treatment works can not effectively deal with ARGs. In fact, sewer processes enhance antibiotic resistance and then release this mix to the environment. With many of these sewer plants dumping effluent into the nation's rivers, the down-river cities are thus at potential risk. The result of this combined unknown has potentially important impacts on public health that warrant increased attention to allow for a better perspective. Industry needs to acknowledge publicly that they are aware that wastewater treatment plants are not capable of effective containment or management of pharmaceuticals and pathogens. Any public information plan on the presence and persistence of pharmaceuticals in the environment and in drinking water needs to acknowledge the role of wastewater effluents and biosolids in the dispersion of these compounds, the pathogens and their genetic fragments. It would be reckless to ignore fact that the treatment technology for our toilet and industrial wastes cannot manage these compounds. I was in communication with the Conference's Group 4 scientists discussing public education needs and they indicated that there is a reluctance to discuss these issues because it was felt that comments on wastewater and drinking water pharmaceutical residuals would be unacceptable since the public would not be able to deal with the information and would go into a dissociative state. [1] Detection of Escherichia coli in biofilms from pipe samples and coupons in drinking water distribution networks. Juhna T, Birzniece D, Larsson S, Zulenkovs D, Sharipo A, Azevedo NF, Ménard-Szczebara F, Castagnet S, Féliers C, Keevil CW. Riga Technical University, Department of Water Engineering and Technology, 16/20 Azenes Street, Riga LV 1048, Latvia. talisj@bf.rtu.lv Appl Environ Microbiol. 2007 Nov;73(22):7456-64. Epub 2007 Aug 24. Fluorescence in situ hybridization (FISH) was used for direct detection of Escherichia coli on pipe surfaces and coupons in drinking water distribution networks. Old cast iron main pipes were removed from water distribution networks in France, England, Portugal, and Latvia, and E. coli was analyzed in the biofilm. In addition, 44 flat coupons made of cast iron, polyvinyl chloride, or stainless steel were placed into and continuously exposed to water on 15 locations of 6 distribution networks in France and Latvia and examined after 1 to 6 months exposure to the drinking water. In order to increase the signal intensity, a peptide nucleic acid (PNA) 15-mer probe was used in the FISH screening for the presence or absence of E. coli on the surface of pipes and coupons, thus reducing occasional problems of autofluorescence and low fluorescence of the labeled bacteria. For comparison, cells were removed from the surfaces and examined with culture-based or enzymatic (detection of beta-d-glucuronidase) methods. An additional verification was made by using PCR. Culture method indicated presence of E. coli in one of five pipes, whereas all pipes were positive with the FISH methods. E. coli was detected in 56% of the coupons using PNA FISH, but no E. coli was detected using culture or enzymatic methods. PCR analyses confirmed the presence of E. coli in samples that were negative according to culture-based and enzymatic methods. The viability of E. coli cells in the samples was demonstrated by the cell elongation after resuscitation in low-nutrient medium supplemented with pipemidic acid, suggesting that the cells were present in an active but nonculturable state, unable to grow on agar media. E. coli contributed to ca. 0.001 to 0.1% of the total bacterial number in the samples. The presence and number of E. coli did not correlate with any of physical and/or chemical characteristic of the drinking water (e.g., temperature, chlorine, or biodegradable organic matter concentration). We show here that E. coli is present in the biofilms of drinking water networks in Europe. Some of the cells are metabolically active but are often not detected due to limitations of traditionally used culture-based methods, indicating that biofilm should be considered as a reservoir that must be investigated further in order to evaluate the risk for human health. ++++++++++++++++ [2] Comment in: Environ Sci Technol. 2007 Apr 1;41(7):2651-2. Antibiotic resistance genes as emerging contaminants: studies in northern Colorado. Pruden A, Pei R, Storteboom H, Carlson KH. Environ Sci Technol. 2006 Dec 1;40(23):7445-50. Department of Civil and Environmental Engineering, Colorado State University, Fort Collins, Colorado 80523, USA. apruden@engr.colostate.edu This study explores antibiotic resistance genes (ARGs) as emerging environmental contaminants. The purpose of this study was to investigate the occurrence of ARGs in various environmental compartments in northern Colorado, including Cache La Poudre (Poudre) River sediments, irrigation ditches, dairy lagoons, and the effluents of wastewater recycling and drinking water treatment plants. Additionally, ARG concentrations in the Poudre River sediments were analyzed at three time points at five sites with varying levels of urban/agricultural impact and compared with two previously published time points. It was expected that ARG concentrations would be significantly higher in environments directly impacted by urban/agricultural activity than in pristine and lesser-impacted environments. Polymerase chain reaction (PCR) detection assays were applied to detect the presence/absence of several tetracycline and sulfonamide ARGs. Quantitative real-time PCR was used to further quantify two tetracycline ARGs (tet(W) and tet(O)) and two sulfonamide ARGs (sul(I) and sul(II)). The following trend was observed with respect to ARG concentrations (normalized to eubacterial 16S rRNA genes): dairy lagoon water > irrigation ditch water > urban/agriculturally impacted river sediments (p < 0.0001), except for sul(II), which was absent in ditch water. It was noted that tet(W) and tet(O) were also present in treated drinking water and recycled wastewater, suggesting that these are potential pathways for the spread of ARGs to and from humans. On the basis of this study, there is a need for environmental scientists and engineers to help address the issue of the spread of ARGs in the environment. ++++++++++++++++++++ [3] Toxicogenomic response to chlorination includes induction of major virulence genes in Staphylococcus aureus. Chang MW, Toghrol F, Bentley WE. Environ Sci Technol. 2007 Nov 1;41(21):7570-5 School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore. Despite the widespread use of chlorination for microbial control in aqueous environments, cellular response mechanisms of human pathogens, such as Staphylococcus aureus, against chlorination remain unknown. In this work, genome-wide transcriptional analysis was performed to elucidate cellular response of S. aureusto hypochlorous acid, an active antimicrobial product of chlorination in aqueous solution. Our results suggest that hypochlorous acid repressed transcription of genes involved in cell wall synthesis, membrane transport, protein synthesis, and primary metabolism, while amino acid synthesis genes were induced. Furthermore, hypochlorous acid induced transcription of genes encoding major virulence factors of S. aureus, such as exotoxins, hemolysins, leukocidins, coagulases, and surface adhesion proteins, which all play essential roles in staphylococcal virulence. This work implies that chlorination may stimulate production of virulence factors, which provides new insight into host-pathogen interactions and effects of chlorine application for microbial control