A constant (0.5) was added to any values that equaled zero. Legionella contamination of dental-unit waters. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely. Submit reprocessing validation test reports in future dental operative unit 510(k)s and describe how reprocessing was considered in the design of the device (e.g. Monitor the water quality and microbial contamination of the dental unit waterlines using standard culturing methods at appropriate intervals to keep bacterial counts lower than 500 CFU/mL of water as recommended by ADA. Agar (1.5%) plates were seeded with an overnight culture of Escherichia coli grown at 35C in tryptic soy broth. Risk of Exposure to Legionella in Dental Practice. Municipal water contains microorganisms that may be considered safe for drinking water, but could potentially cause patient infections when used during dental procedures. The bacteria were swabbed onto the surface of the agar and exposed to ultraviolet irradiation (254 nm) for 20 minutes to inactivate the E. coli culture. Water samples (minimum volume of 10 ml) were filtered through a 0.2 m porosity polyethersulfone-based membrane.4 The membranes were placed in 2 ml of the sample water and bacteria were dislodged by vortexing for one minute. Read your instructions carefully and follow the tips on our product selection guide to be most effective in your protocol. Dental offices tend to be more easily exposed to water contamination, largely because their waterlines differ to regular plumbing in both uses and set up (8). NOTE: Error bars denote standard deviations. Applied and Environmental Microbiology, Apr. And we know most dental practices are, but it can be tempting to shave efforts wherever possible. Dental Waterlines: Understanding and Controlling Biofilms and Other Contaminants. Ensure your customers are notified promptly of any available updated Instructions for Use. The site is secure. in dental unit water samples. Finally, pay special attention to the areas where water needs to be warm for your patient. 
Pederson ED, Stone ME, Ragain JC, Jr, Simecek JW. Pneumonia associated with a dental unit waterline. And we get it - it's tougher and tougher to run a practice with the increasing demands from outside regulators, internal dynamics, and the growing costs to practice. The signed rank test was used to compare levels of HPC in the initial and flushed samples. J Pediatr Infec Dis 2017; 6(3):e116-e112. Choose the right treatment products, and follow the instructions on how to use them precisely. Karas passion extends to helping other hygienists understand the latest protocols, products, and research all with the goal to push the dental hygiene profession forward. One recent report that made national headlines highlighted the tragic story of a seven-year-old girl, who had to have four teeth and part of her jaw bone removed as a result of infection (13). The results of this study indicate that flushing can substantially reduce the level of HPC bacteria present in water used for dental treatment. Retrieved fromhttp://www.ada.org/en/member-center/oral-health-topics/dental-unit-waterlines, 2) American Lung Association. Thirteen (32.5%) of the initial samples were positive for the presence of Legionella by the PCR procedure. Unlike the municipal waterlines leading to your office or your house, dental waterlines are made of a small-bore plastic tubing. How Clean Are the Waterlines in Your Operatory?
Shocking your waterlines is the process of using a strong disinfecting agent to rid your lines of nearly all bacteria. The HPC procedures used in this study are limited to the recovery of cultural planktonic organisms in the water. Eight (61.5%) of the 13 samples positive for Legionella spp. Your municipal lines are made of copper, which as a dissociated ion is antimicrobial / bacteriostatic. sharing sensitive information, make sure youre on a federal Staphylococcus aureus in Healthcare Settings. Without proper cleaning and disinfection, waterborne microorganisms can collect in the dental unit waterline and form a biofilm, a layer of microorganisms or bacteria adhered to the surface of the dental unit waterline, that can become dislodged and enter the water stream. Legionella spp.
Bethesda, MD 20894, Web Policies A patient becomes sick or even hospitalized, apparently because they visited a dental office. after the flushing process. Some of them are even immune to chemicals, making contamination more difficult to prevent. As you prevent contamination,use a cleaning product to flush all tubing in the operatory this can be one of the dirtiest areas in your water supply. Careers. Levels of bacteria were reduced by 1.5 log10CFU/ml using PCA, 1.2 log10 CFU/ml for R2A, and 1.1 log10 CFU/ml for SBA. Peralta G, et al. At the same time, even a small chance of infection for your patients should lead your office to take action. Each treatment product is different and requires different shocking intervals, but after testing hundreds of thousands of dental unit waterlines with every product available, we know for sure that every treatment product can fail and that improper shocking is often the reason. Curiosity Killed the Plaque Ep. The That includes asking yourself whether the waterlines in your dental office are clean, and if you are taking proactive steps to ensure they can cause no harm to your patients. Daily updates and efforts are a must. Plates were observed daily using an inverted microscope (200X). These, in turn, serve as a breeding ground of planktonic microorganisms that that can further contaminate the water (11). The clinician-patient relationship involves a high level of trust, and much of it relates to keeping any individual who walks in the door healthy. Sometimes things are sold one way and work another. But it was in 2000 that the public first became aware of dental unit waterline contamination. Legionnaires Disease. In addressing this issue, the American Dental Association (ADA) has proposed that water used in dental treatment contain a bacterial level of 200 CFU/ml.2 The flushing of dental water lines has been shown to decrease the levels of planktonic bacteria in the water, but this practice has not been shown to affect the biofilm that accumulates in the water lines.3,4 To date, the effectiveness of flushing has been measured by comparing HPC levels present in initial and post-flushing samples. These two culture isolates were further analyzed by the PCR assay and were identified as L. pneumophila. Today's Digital Media, LLC d/b/a Today's RDH.
Retrieved fromhttp://www.cdc.gov/HAI/organisms/staph.html, 5) Centers for Disease Control and Prevention. For surgical procedures, use sterile irrigating solutions, such as sterile water or saline. Please refer to the FDA Guidance document Requests for Feedback and Meetings for Medical Device Submissions: The Q-Submission Program.. We recommend that the reprocessing instructions for your device be updated to contain comprehensive reprocessing instructions based on validation. Additional information on the regulatory requirements (general controls) for dental operative units can be found here. This study was designed to determine the role of flushing dental water lines for the removal of heterotrophic plate count bacteria, Legionella spp., and free-living protozoa. Standard methods for the examination of water and wastewater. Protozoa were detected using a killed bacterial plate procedure. Using this procedure, greater than 70% of the samples were below this limit after flushing. While flushing of dental unit water lines has been recognized as an important strategy for controlling microbial levels in dental water systems, recommendations regarding the efficacy of flushing have changed in recent years. The close association between these organisms and biofilms in dental unit water lines13 suggests that other strategies beyond flushing would be required to effectively address the issue of biofilm removal. Chemicals should be another consideration in your choice of product. A similar story highlighted a serious eye infection by a dental hygienist in Washington after her eye was exposed to water from her ultrasonic scaler. See How Different Dental Waterline Treatment Types Perform in Real-World Practices. Microbial contamination of dental unit water lines: prevalence, intensity and microbiological characteristics.
It was not a pretty picture. After a dentist passed away in California about two decades ago, water samples showed that Legionella bacteria persisted in much higher levels at his office than at home. Before Kara currently lives in Vancouver, Washington, just outside Portland, Oregon, with her husband, Ben, and their four Chihuahuas. Bacterial counts were log transformed prior to conducting the analyses. Retrieved fromhttp://www.cdc.gov/legionella/clinicians/diseasespecifics.html, 6) Centers for Disease Control and Prevention. Dental Outbreak (Mycobacterium), An official website of the United States government, Recalls, Market Withdrawals and Safety Alerts, Temporomandibular Disorders (TMD) Devices, Guidelines for Infection Control in Dental Health-Care Settings 2003, Reprocessing Medical Devices in Health Care Settings: Validation Methods and Labeling, Deciding When to Submit a 510(k) for a Change to an Existing Device, Requests for Feedback and Meetings for Medical Device Submissions: The Q-Submission Program, Centers for Disease Control and Prevention. Use the dental unit without following the cleaning and disinfection procedures in the manufacturers reprocessing instructions. Stagnant water, of course, can facilitate bacteria growth. The SBA medium yielded a mean of 2.20 log10CFU/ml in the initial samples and 1.08 log10CFU/ml in the flushed samples. Approximately one-half of the samples were collected from syringes that had not been used within the past 24 hours. New Dental Waterline Regulations Coming to Washington State. Depending on the device design, sampling locations may include the connection to the water source, the dental handpiece connection, and a mid-point between these.
The mean level of bacteria present in the initial samples using PCA was 3.36 log10 CFU/ml and 1.84 log10CFU/ml in flushed samples. This should include infection control measures such as, but not limited to, monitoring water quality. aU.S. However, the presence of pathogens in dental unit water lines is not consistent with accepted infection-control principles.2 Legionella spp. (2010, Aug). One of the other unique differences about dental waterlines is their slow flowrate. Cochran's test for related observations was used to determine if there were significant differences between the methods used for the analysis of Legionella spp. First - and like all infection control measures - it requires professionals dedicated to patient safety. In fact, at the OSAP Dental Infection Boot Camp in 2017, infection control experts Shannon E. Mills, DDS, John A. Molinari, PhD, and others commented that it was the number 1 challenge facing dental professionals over the next 5 years. Next, cleaning your waterlines requires shocking them. Retrievedfromhttp://www.lung.org/lung-health-and-diseases/lung-disease-lookup/nontuberculosismycobacteria/learn-about-ntm.html?referrer=https://www.google.com/, 3) Atas, R.M., et. This bacterium is especially difficult to treat with antibiotics, making the surgery and removal necessary. Why, When, and How to Test Dental Unit Waterlines, Dental Water Treatment Product Selection Guide, Three Necessary Aspects of Every Dental Waterline Treatment Protocol, Dental Water Testing - A Comprehensive Guide, Calling All California Dental Pros to Higher Water Safety Standards - Assembly Bill 1277, Copyright 2018 - ProEdge Dental Water Labs, Cleaning and Maintaining Dental Unit Waterlines - Dentistry's Dirty Little Secret. The flushing process reduced the level of heterotrophic plate count bacteria by 1.1 to 1.5 log10 CFU/ml. Pediatric dental clinic-associated outbreak of Mycobacterium abscessus infection. They are safe for your patients and your equipment, but maintain the clean lines your shocking protocol already established. That's why it'sour team's goal to help professionals and practices feeling that tension to continue giving their patients the absolute best economically and effectively. Before sharing sensitive information, make sure you're on a federal government site. As top dental professionals and industry experts continue helping dedicated dental professionals practice with the highest standard of care through effective dental unit waterline safety, it won't matter if "the secret" gets out because more and more waterlines will be clean. Environmental Protection Agency, Cincinnati, OH, bPrivate practice, Williamstown, KY; Kentucky Dental Association. Dental practitioners should adopt appropriate infection control procedures for dental unit waterlines based on the manufacturers instructions for use. Conduct an assessment to evaluate if additional validation testing is necessary to provide up-to-date comprehensive reprocessing instructions. This is the part of a comprehensive dental unit waterline maintenance protocol that allows continuous treatments like tablets, straws, cartridges, and liquid drops to work effectively.
Microbial contamination of dental unit water lines: current preventive measures and emerging options. Five (83%) of the six initial samples and five (83%) of the six flushed samples that were positive for Legionella spp. Using the two most common procedures (PCA and R2A) for HPC analysis in drinking water, only 20% or less of the initially drawn samples had bacterial counts below the recommended levels. Each sample was analyzed for HPC bacteria, Legionella spp., and free-living protozoa. Our team recommends at least quarterly testing of your dental waterlines to ensure your patients and practice are safe. The American Dental Association maintains that testing the only way to ensure your treatment product is working and suggests monitoring your waterlines consistently. In a statement that year, the ADA highlighted the importance that no more than 200 colony-forming units (CFU) of aerobic mesophilic heterotrophic bacteria at any point in time in the unfiltered output of the dental unit.(1). The CDC has highlighted the fact that this is a common environment for the production and reproduction of bacteria, fungi, and protozoa (11). Orange County Health Care Agency. The warmer the water, the more easily bacteria can grow. using cultural, immunological, and molecular procedures and for the occurrence of free-living protozoa using a killed bacteria plate procedure. (2014, May). That means staying away from bleach-based products, which might kill bacteria but also damage your equipment and emit chloroform (9). Centers for Disease Control and Prevention (US) Recommended infection control practices for dentistry, 1993. Over 60% of dental practices have at least one failing waterline when they test. Also, you dont want to expose yourself, your staff, or your patients to any potential harm, even if the risk is low. Twelve (30%) of the flushed samples gave positive results for the genus Legionella, and the same three samples that were initially positive for L. pneumophila were also positive in the flushed samples. Always properly dispose of single use disposable items after they have been used. Contact the manufacturer of the dental unit to obtain the most up-to-date instructions or with any questions regarding the reprocessing of the dental unit. MMWR 2003:52(No.RR-17)-Accessed September 6, 2017, Centers for Disease Control and Prevention. Retrievedfromhttps://www.ncbi.nlm.nih.gov/pubmed/22004039, 13) Ross, E. (2016,Sept 30). Kara Vavrosky, RDHEP, is a Co-founder and Chief Content Officer of Todays RDH, a digital media company for dental hygienists, encompassing a daily publication, podcast, virtual continuing education events, and self-study continuing education. and non-tuberculosis mycobacteria. The levels of bacteria in the samples showed considerable variation between the analytical methods. government site. Bacteria in biofilms in the dental water units would only be detected by these procedures if they were being sloughed off into the bulk water. We often think of the small tube as creating a river-like flow, but its much more like a pond with a small drain.
Pederson ED, Stone ME, Ragain JC, Jr, Simecek JW. Pneumonia associated with a dental unit waterline. And we get it - it's tougher and tougher to run a practice with the increasing demands from outside regulators, internal dynamics, and the growing costs to practice. The signed rank test was used to compare levels of HPC in the initial and flushed samples. J Pediatr Infec Dis 2017; 6(3):e116-e112. Choose the right treatment products, and follow the instructions on how to use them precisely. Karas passion extends to helping other hygienists understand the latest protocols, products, and research all with the goal to push the dental hygiene profession forward. One recent report that made national headlines highlighted the tragic story of a seven-year-old girl, who had to have four teeth and part of her jaw bone removed as a result of infection (13). The results of this study indicate that flushing can substantially reduce the level of HPC bacteria present in water used for dental treatment. Retrieved fromhttp://www.ada.org/en/member-center/oral-health-topics/dental-unit-waterlines, 2) American Lung Association. Thirteen (32.5%) of the initial samples were positive for the presence of Legionella by the PCR procedure. Unlike the municipal waterlines leading to your office or your house, dental waterlines are made of a small-bore plastic tubing. How Clean Are the Waterlines in Your Operatory? Shocking your waterlines is the process of using a strong disinfecting agent to rid your lines of nearly all bacteria. The HPC procedures used in this study are limited to the recovery of cultural planktonic organisms in the water. Eight (61.5%) of the 13 samples positive for Legionella spp. Your municipal lines are made of copper, which as a dissociated ion is antimicrobial / bacteriostatic. sharing sensitive information, make sure youre on a federal Staphylococcus aureus in Healthcare Settings. Without proper cleaning and disinfection, waterborne microorganisms can collect in the dental unit waterline and form a biofilm, a layer of microorganisms or bacteria adhered to the surface of the dental unit waterline, that can become dislodged and enter the water stream. Legionella spp.
Bethesda, MD 20894, Web Policies A patient becomes sick or even hospitalized, apparently because they visited a dental office. after the flushing process. Some of them are even immune to chemicals, making contamination more difficult to prevent. As you prevent contamination,use a cleaning product to flush all tubing in the operatory this can be one of the dirtiest areas in your water supply. Careers. Levels of bacteria were reduced by 1.5 log10CFU/ml using PCA, 1.2 log10 CFU/ml for R2A, and 1.1 log10 CFU/ml for SBA. Peralta G, et al. At the same time, even a small chance of infection for your patients should lead your office to take action. Each treatment product is different and requires different shocking intervals, but after testing hundreds of thousands of dental unit waterlines with every product available, we know for sure that every treatment product can fail and that improper shocking is often the reason. Curiosity Killed the Plaque Ep. The That includes asking yourself whether the waterlines in your dental office are clean, and if you are taking proactive steps to ensure they can cause no harm to your patients. Daily updates and efforts are a must. Plates were observed daily using an inverted microscope (200X). These, in turn, serve as a breeding ground of planktonic microorganisms that that can further contaminate the water (11). The clinician-patient relationship involves a high level of trust, and much of it relates to keeping any individual who walks in the door healthy. Sometimes things are sold one way and work another. But it was in 2000 that the public first became aware of dental unit waterline contamination. Legionnaires Disease. In addressing this issue, the American Dental Association (ADA) has proposed that water used in dental treatment contain a bacterial level of 200 CFU/ml.2 The flushing of dental water lines has been shown to decrease the levels of planktonic bacteria in the water, but this practice has not been shown to affect the biofilm that accumulates in the water lines.3,4 To date, the effectiveness of flushing has been measured by comparing HPC levels present in initial and post-flushing samples. These two culture isolates were further analyzed by the PCR assay and were identified as L. pneumophila. Today's Digital Media, LLC d/b/a Today's RDH.
Retrieved fromhttp://www.cdc.gov/HAI/organisms/staph.html, 5) Centers for Disease Control and Prevention. For surgical procedures, use sterile irrigating solutions, such as sterile water or saline. Please refer to the FDA Guidance document Requests for Feedback and Meetings for Medical Device Submissions: The Q-Submission Program.. We recommend that the reprocessing instructions for your device be updated to contain comprehensive reprocessing instructions based on validation. Additional information on the regulatory requirements (general controls) for dental operative units can be found here. This study was designed to determine the role of flushing dental water lines for the removal of heterotrophic plate count bacteria, Legionella spp., and free-living protozoa. Standard methods for the examination of water and wastewater. Protozoa were detected using a killed bacterial plate procedure. Using this procedure, greater than 70% of the samples were below this limit after flushing. While flushing of dental unit water lines has been recognized as an important strategy for controlling microbial levels in dental water systems, recommendations regarding the efficacy of flushing have changed in recent years. The close association between these organisms and biofilms in dental unit water lines13 suggests that other strategies beyond flushing would be required to effectively address the issue of biofilm removal. Chemicals should be another consideration in your choice of product. A similar story highlighted a serious eye infection by a dental hygienist in Washington after her eye was exposed to water from her ultrasonic scaler. See How Different Dental Waterline Treatment Types Perform in Real-World Practices. Microbial contamination of dental unit water lines: prevalence, intensity and microbiological characteristics. It was not a pretty picture. After a dentist passed away in California about two decades ago, water samples showed that Legionella bacteria persisted in much higher levels at his office than at home. Before Kara currently lives in Vancouver, Washington, just outside Portland, Oregon, with her husband, Ben, and their four Chihuahuas. Bacterial counts were log transformed prior to conducting the analyses. Retrieved fromhttp://www.cdc.gov/legionella/clinicians/diseasespecifics.html, 6) Centers for Disease Control and Prevention. Dental Outbreak (Mycobacterium), An official website of the United States government, Recalls, Market Withdrawals and Safety Alerts, Temporomandibular Disorders (TMD) Devices, Guidelines for Infection Control in Dental Health-Care Settings 2003, Reprocessing Medical Devices in Health Care Settings: Validation Methods and Labeling, Deciding When to Submit a 510(k) for a Change to an Existing Device, Requests for Feedback and Meetings for Medical Device Submissions: The Q-Submission Program, Centers for Disease Control and Prevention. Use the dental unit without following the cleaning and disinfection procedures in the manufacturers reprocessing instructions. Stagnant water, of course, can facilitate bacteria growth. The SBA medium yielded a mean of 2.20 log10CFU/ml in the initial samples and 1.08 log10CFU/ml in the flushed samples. Approximately one-half of the samples were collected from syringes that had not been used within the past 24 hours. New Dental Waterline Regulations Coming to Washington State. Depending on the device design, sampling locations may include the connection to the water source, the dental handpiece connection, and a mid-point between these.
The mean level of bacteria present in the initial samples using PCA was 3.36 log10 CFU/ml and 1.84 log10CFU/ml in flushed samples. This should include infection control measures such as, but not limited to, monitoring water quality. aU.S. However, the presence of pathogens in dental unit water lines is not consistent with accepted infection-control principles.2 Legionella spp. (2010, Aug). One of the other unique differences about dental waterlines is their slow flowrate. Cochran's test for related observations was used to determine if there were significant differences between the methods used for the analysis of Legionella spp. First - and like all infection control measures - it requires professionals dedicated to patient safety. In fact, at the OSAP Dental Infection Boot Camp in 2017, infection control experts Shannon E. Mills, DDS, John A. Molinari, PhD, and others commented that it was the number 1 challenge facing dental professionals over the next 5 years. Next, cleaning your waterlines requires shocking them. Retrievedfromhttp://www.lung.org/lung-health-and-diseases/lung-disease-lookup/nontuberculosismycobacteria/learn-about-ntm.html?referrer=https://www.google.com/, 3) Atas, R.M., et. This bacterium is especially difficult to treat with antibiotics, making the surgery and removal necessary. Why, When, and How to Test Dental Unit Waterlines, Dental Water Treatment Product Selection Guide, Three Necessary Aspects of Every Dental Waterline Treatment Protocol, Dental Water Testing - A Comprehensive Guide, Calling All California Dental Pros to Higher Water Safety Standards - Assembly Bill 1277, Copyright 2018 - ProEdge Dental Water Labs, Cleaning and Maintaining Dental Unit Waterlines - Dentistry's Dirty Little Secret. The flushing process reduced the level of heterotrophic plate count bacteria by 1.1 to 1.5 log10 CFU/ml. Pediatric dental clinic-associated outbreak of Mycobacterium abscessus infection. They are safe for your patients and your equipment, but maintain the clean lines your shocking protocol already established. That's why it'sour team's goal to help professionals and practices feeling that tension to continue giving their patients the absolute best economically and effectively. Before sharing sensitive information, make sure you're on a federal government site. As top dental professionals and industry experts continue helping dedicated dental professionals practice with the highest standard of care through effective dental unit waterline safety, it won't matter if "the secret" gets out because more and more waterlines will be clean. Environmental Protection Agency, Cincinnati, OH, bPrivate practice, Williamstown, KY; Kentucky Dental Association. Dental practitioners should adopt appropriate infection control procedures for dental unit waterlines based on the manufacturers instructions for use. Conduct an assessment to evaluate if additional validation testing is necessary to provide up-to-date comprehensive reprocessing instructions. This is the part of a comprehensive dental unit waterline maintenance protocol that allows continuous treatments like tablets, straws, cartridges, and liquid drops to work effectively.
Microbial contamination of dental unit water lines: current preventive measures and emerging options. Five (83%) of the six initial samples and five (83%) of the six flushed samples that were positive for Legionella spp. Using the two most common procedures (PCA and R2A) for HPC analysis in drinking water, only 20% or less of the initially drawn samples had bacterial counts below the recommended levels. Each sample was analyzed for HPC bacteria, Legionella spp., and free-living protozoa. Our team recommends at least quarterly testing of your dental waterlines to ensure your patients and practice are safe. The American Dental Association maintains that testing the only way to ensure your treatment product is working and suggests monitoring your waterlines consistently. In a statement that year, the ADA highlighted the importance that no more than 200 colony-forming units (CFU) of aerobic mesophilic heterotrophic bacteria at any point in time in the unfiltered output of the dental unit.(1). The CDC has highlighted the fact that this is a common environment for the production and reproduction of bacteria, fungi, and protozoa (11). Orange County Health Care Agency. The warmer the water, the more easily bacteria can grow. using cultural, immunological, and molecular procedures and for the occurrence of free-living protozoa using a killed bacteria plate procedure. (2014, May). That means staying away from bleach-based products, which might kill bacteria but also damage your equipment and emit chloroform (9). Centers for Disease Control and Prevention (US) Recommended infection control practices for dentistry, 1993. Over 60% of dental practices have at least one failing waterline when they test. Also, you dont want to expose yourself, your staff, or your patients to any potential harm, even if the risk is low. Twelve (30%) of the flushed samples gave positive results for the genus Legionella, and the same three samples that were initially positive for L. pneumophila were also positive in the flushed samples. Always properly dispose of single use disposable items after they have been used. Contact the manufacturer of the dental unit to obtain the most up-to-date instructions or with any questions regarding the reprocessing of the dental unit. MMWR 2003:52(No.RR-17)-Accessed September 6, 2017, Centers for Disease Control and Prevention. Retrievedfromhttps://www.ncbi.nlm.nih.gov/pubmed/22004039, 13) Ross, E. (2016,Sept 30). Kara Vavrosky, RDHEP, is a Co-founder and Chief Content Officer of Todays RDH, a digital media company for dental hygienists, encompassing a daily publication, podcast, virtual continuing education events, and self-study continuing education. and non-tuberculosis mycobacteria. The levels of bacteria in the samples showed considerable variation between the analytical methods. government site. Bacteria in biofilms in the dental water units would only be detected by these procedures if they were being sloughed off into the bulk water. We often think of the small tube as creating a river-like flow, but its much more like a pond with a small drain.