Assessments of Residential and Workplace Environmental Microbiology Exposure


Monday, May 23, 2016, 10:30 AM - 12:30 PM


Exposure of Residential Occupants to In-Home Sewage

H. Burge, EMLab PK, San Bruno, CA

Situation/Problem: In healthy people, gut microbial populations are formed of nonpathogenic microbes that are necessary for the maintenance of a healthy digestive system. These and any ongoing disease organisms will be in the sewage. In general, gastrointestinal organisms within residences are shared by hand to mouth transfer, not from sewage. Exposure to gut organisms occurs when using the toilet, and especially when flushing. Gastrointestinal pathogens are shared within families in this way as well. Sewage spills include toilet overflows during flushing, and backup of sewage from a blockage outside the home. In single family residences the sewage from both of these events includes only those organisms that were present in the occupants and visitors and thus are likely to include organisms to which the occupants have already been exposed. A backup from a main sewer line exiting a multifamily unit will contain organisms from all of the occupants in the building. These spills are likely to contain a variety of pathogens to which all individuals in the building have not been exposed. The risks associated with sewage contact are for the most part infections. Once out of the human body microorganism populations dwindle at an exponential rate. Once a spill has spread across the floor, the entrained organisms attach to surfaces and as the area dries, the death rate increases. Once completely dry, relatively few organisms will have survived, and both living and dead organisms will be firmly attached to surfaces and are very unlikely to enter the air.

Resolution: The risk of contracting a GI disease from cleaning up sewage from a single family residence is very low. Cleanup of sewage from a multifamily common line may contain pathogens that could cause disease, and these could cause illness in some people provided the spill is cleaned while still wet. It is advisable to have these spills cleaned by a professional. Professionals have a relatively low risk of contracting a disease because they use protection and are trained how to avoid hand to mouth exposure.

Results: This information should allay fears that are common in homeowners, and reassure professionals of the minimal risks associated with cleaning dry sewage spills.

Lessons learned: Residential in-home sewage spills are of little hazard to single family residents. Sewage backup from on the property also carries little risk for occupants. Multifamily sewage may have pathogens to which all the residents of the complex have not been exposed. These should be handled by a trained professional.



Airborne Mycobacterium Tuberculosis Profiles in a Hospital with a Nosocomial TB Outbreak

Y. Yen, Kaohsiung Medical University, Kaohsiung, Taiwan

Objective: The main purpose of this study was assessing the airborne Mycobacterium tuberculosis profiles in ta hospital to identify high risk areas. In addition, the difference of airborne Mycobacterium tuberculosis concentration before and after ventilation improvement was also evaluated.

Methods: The airborne samples were collected by a Nuclepore filter with sampling time of 8 hr. at sampling flow rate of 20 L/min. A total of 192 air samples were taken from negative pressure isolation wards, medical wards, waiting rooms and consulting rooms of medical department and pediatric department in the period of December 2005 to July 2006. The concentration of airborne M. tuberculosis was quantitatively determined by the ABI 7700 real time quantitative polymerase chain reaction (real time qPCR) system.

Results: It was found that the positive rate of airborne M. tuberculosis is 6.25%. In addition, all positive samples were in the wards of chest and infectious disease division in the internal medicine department. The airborne M. tuberculosis ​​​concentration was in the range of 54 copies/m3 to 1109 copies/m3. The highest concentration was found in the nursing station of chest division. After improvement of ventilation system, no M. tuberculosis was detected in the air. In addition, the airborne bacteria concentrations were also declining after the improvement. Our results showed that the improvement of air conditioning may reduce the risk of M. tuberculosis exposure. In addition, it was found a good correlation between M. tuberculosis and airborne bacteria.

Conclusions: In regard to the culturable bacteria and fungi concentration in the air, 122 samples were analyzed in the hospital. According to the IAQ Recommended Values of Taiwan EPA, the failure rate was 64% and 8% for bacteria and fungi, respectively. In addition, the airborne bacteria concentrations in the nursing station of chest division were all higher than the recommended values, even after the improvement of ventilation.



Inspection of Building Water Systems for Legionella Control

L. Nguyen Weekes, InAIR Environmental Ltd., Ottawa, ON, Canada

Situation/Problem: Legionnaire’s disease is again a topic of great interest to IAQ practitioners as the incidence of this disease worldwide is on the rise. Several professional organizations (e.g. ASHRAE and the American Industrial Hygiene Association) and governmental agencies (e.g. Canada’s Public Works and Government Services) have recently produced or reissued guidance documents on the design, operation and maintenance of building water systems in order to prevent the growth of Legionella bacteria on building water systems.

Resolution: The emphasis of the existing documentation is on the proper operation and maintenance of building water systems and the creation of a Legionella Bacteria Control Management Plan (LBCMP) for these buildings. In order for these Management Plans to be effective, a detailed inspection of building water systems is essential to determine where the potential for bacterial growth exist.

Results: This presentation will provide experienced tips and examples on how to inspect different building water systems and how to evaluate the risk for Legionella contamination within these systems. Examples will include centralized water systems and compartmental systems as well as the design trend in newer buildings such as high energy efficiency buildings and their water systems.

Lessons learned: Based on the lessons learned from the inspections, recommendations can be made on how to correct the design, operation or maintenance issues that might lead to a Legionella growth.



2015 Bronx Legionellosis Outbreak: A Consultant's Perspective

C. Cooper, VERTEX companies, Kingston, NY; S. Zouak, Airtek Environmental Corp, Long Island City, NY

Situation/Problem: A Legionellosis Outbreak is defined by the US Centers for disease Control as two or more confirmed cases of Legionellosis occurring in the same locality within a six-month period. Between July and August, 2015, more than 120 cases of Legionellosis were identified in the South Bronx, a corner of New York City's northernmost borough, resulting in 12 deaths. This was largest outbreak of Legionnaires' disease in New York City's history. In response the City issued, and shortly thereafter New York State issued emergency regulations affecting cooling tower owners and operators State wide requiring inspection, disinfection, and testing of all cooling towers and evaporative condensers with a 30 day compliance deadline. In addition, these new regulations include requirements for tower owners to develop and implement written maintenance plans by March 1, 2016 in accordance with ANSI/ASHRAE Standard 188-2015 and, thereafter, annual certification reporting of tower compliance.

Resolution: These new regulations have far reaching implications, primarily on increased monitoring, testing, maintenance and surveillance for these systems. Although the CDC, the New York State Department of Health and a variety of industry groups have all published guidelines for maintaining cooling towers and potable water systems to prevent the spread of Legionella bacteria, prior to these regulations cooling towers and potable water systems in New York were unregulated and no tower registration was required. For the first time under these new regulations, owners in New York are required to register, test, and annually certify and report their testing and maintenance program.

Results: Our presentation will briefly review the chronology of the Bronx outbreak, report the current status and requirements of the NYS cooling tower and potable water systems regulatory programs for control of Legionella, and will describe case examples for bringing two university campuses, a hospital, and several retirement homes all located in the south Bronx into compliance with these new Legionella regulations. We describe: investigating the water systems, implementing safe inspection and sampling programs, assessing the data, drafting written compliance plans, and working with these institutions to implement their plan elements.

Lessons learned: Important elements identified for implementing new Legionella control programs include integration of program inspection, testing, records maintenance and reporting elements into existing facilities management and operations infrastructure, effective training for maintenance personnel, and routine third party auditing.



Survey for Exposure to Human Pathogens from Pigeon Droppings in a Petroleum Refinery

P. Owens, Shell Oil Company, Martinez, CA

Situation/Problem: Pigeon live and roost in petroleum refineries thus droppings accumulate on elevated platforms, ground level walkways and other surfaces workers contact. During routine refinery operations workers may walk on surfaces where dropping have accumulated or may handle equipment with residue of droppings.

Resolution: To help investigate workers’ health risks, a risk assessment, including an exposure survey, was initiated. A literature review indicated the possibility for human pathogens to be present in some pigeon droppings. A survey of the refinery pigeon droppings was conducted to evaluate the presence of human pathogens in bulk droppings. Several air samples were collected to evaluate the likelihood of pathogens becoming airborne from routine work. A variety of locations and environmental conditions were sampled. Air samples were taken during routine and worst-case exposure scenarios.

Results: In bulk samples, pathogens were detected at a rate similar to published percentages; 22 detected in 126 samples (17%). The least harmful pathogen was detected most frequently (C. neoformans, 22%), and the most harmful was detected less frequently (H. capsulatum, 9%). The risk of personnel exposure to airborne avian pathogens appears low; only one detectable air sample. Given the IRRST control banding guidance, the exposure control measures seem sufficient: frequent gentle water wash down areas to reduce aged feces accumulation, half-facepiece air purifying respirators with P-100 cartridge during any potential feces aerosolization, predators, nets where feasible, noise deterrents, and hygiene practices. And the ongoing birth control agent treatment appears to be an effective, humane method to greatly reduce the refinery pigeon population.

Lessons learned: One lesson learned from this survey is, it is possible to for human pathogens to exist within refinery pigeon droppings. Another lesson learned is controlling the pigeon population is the best proactive method to reduce the risk of exposure. And lastly, it appears the risk of pathogen exposure and infection is low during routine refinery work.



A Count-Based Method for Improved Quality Control Acceptance Limits of EMLAP Air Direct Fields of Testing

M. Saleh, Sporometrics, Toronto, ON, Canada

Objective: AIHA-LAP, LLC accredited laboratories are required to perform 10% retesting of samples as part of their quality control program. There are several statistical methods suggested in guidance documents but they do not include a count based approach. The objective of this research was to correlate the coefficient of variation to different spore loads to create more accurate acceptability limits for inter/intra analyst comparisons.

Methods: Our method was based on daily reference slide counts of varying spore concentrations; ranging from 0 spores to >100 spores per slide. Data was collected by daily readings from six analysts and the coefficient of variation was determined for each spore load.

Results: Results of the statistical analysis of this data show that coefficient of variation and spore load have an exponential decay relationship (x-0.5), with a coefficient that is dependent on the analytical method used (i.e. magnification, percentage of sample read, etc.).

Conclusions: In conclusion, this model (vs. a pooled CV model) improves acceptability thresholds at very low and very high counts and reduces false negative QC failures. From a laboratory analysis perspective, this model is easy to adopt into current quality control practices, makes inter/intra analyst comparisons more realistic and improves the quality of results.