New Study Links human skin flakes and bacteria to foul odors in HVAC Systems

Skin Flakes cause HVAC Odors

Current research from Hong Kong Baptist University (HKBU) has found that by-products produced by bacteria consuming dead human skin flakes emit urine-like and body odor types of smells that are distributed through a building via the HVAC system.

The study was conducted under the leadership of Dr. Lai Ka-man, Associate Professor of the Department of Biology at HKBU. Dr. Lai’s team revealed that human skin flakes (skin squames), which are naturally shed, can be returned into the HVAC system’s air handling units (AHU), accumulate and become a food source for the bacteria living within.

It is estimated that a single human can shed between 30,000-40,000 skin flakes every hour, or close to a million over a 24-hour period [source: Boston Globe]! Some of these cells aggregate with other microscopic compounds to settle on surfaces into what we commonly call “dust”. Other airborne skin squames have been found to absorb UV radiation and ozone then safely degrade. However, the HKBU study found that a significant number of skin squames can populate the inside of the AHU even when filters are in use and no visible signs of dust are present.

How are the odors produced?

Skin cells consist of keratins that are structural proteins. They also contain other microbial nutrients like fatty acids, lipids and other natural metabolites. The study found that Keratins consumed by bacteria are broken down to ammonium. When limited amounts of carbon are available in the environment it can lead to excessive amounts of ammonium being emitted which can lead to a urine-like or cat’s litter box smell. Further, when other nutrients from skin squames are also consumed by bacteria they can degrade into various volatile short-chain fatty acids that produce the smell of human body odor or what is sometimes referred to as “dirty sock syndrome”.

“Skin flakes, a common constituent in dust flora of indoor environments, can have ozone reducing capabilities by oxidation. However, their elevated concentrations within HVAC systems may be an odor-causing nuisance, and problematic from a hygienic point of view.” Says Dr. Rajiv Sahay, Director of Environmental Diagnostics Laboratory at Pure Air Control Services, “These cells nurture several microbiomes which can adversely impact healthy living. We have noticed higher concentrations of these particulates in HVAC systems in comparison to other building locations while investigating indoor contaminants.”

The HKBU team also investigated and compared microbial samples from AHU’s with and without odor complaints. After studying the biological properties of the isolated bacteria, they reported that the Staphylococcus species emitted from the HVAC system to be one of the odor causing units.

Dr. Lai Ka-man, AP, Dept. of Biology of HKBU, center.
Dr. Lai Ka-man, AP, Dept. of Biology of HKBU, center.

How do these odors affect building occupants?
“Air quality in indoor environments is associated with people’s health and well-being. These odors can lead to discomfort and low productivity” Says Dr. Lai, “Odor problems are due to a dirty air conditioning system – Therefore, cleaning the system is the general practice to eliminate the odor.”

A recent Harvard study backs up the findings that poor indoor air quality can lead to lower cognitive function and productivity. In addition, odors, if severe enough, can also cause allergic-type reactions like itchy eyes, nasal drips and even headaches.

Minimizing the Odors and Risks

As Dr. Lai pointed out cleaning the HVAC system on a regular basis can reduce both skin squames and bacteria. But not all cleaning methods are the same. Conventional AHU and Duct cleaning only mitigate a small portion of the factors that contribute to the accumulation of dust and microbial proliferation. Consider that the pump/spray method of AHU coil cleaning uses very low pressure to spray chemicals on the surface of the evaporator coil fins. This is a quick way to temporarily reduce odors, but what about deeper inside of the coil and the rest of the interior of the AHU? Steam coil cleaning is a far more effective and thorough method to ensure the whole interior of the AHU, as well as completely throughout the coils are completely disinfected.

“Our exclusive PURE-Steam coil cleaning process utilizes high temperature, low pressure steam to hygienically clean the entire AHU.” Says Alan Wozniak, President of Pure Air Control Services, “It’s the only Green Clean Institute certified eco-friendly HVAC cleaning process out there!”

Downstream of the AHU is the ductwork. Traditional duct cleaning generally is done by quickly brushing and vacuuming the ducts and vents. This process can actually stir up debris and recirculate through the building for a period time. Again, a more careful and hygienic method is recommended. One that employs containment, HEPA vacuums and even disinfecting mists like Pure Air’s PURE-Decon service. It is recommended that AHU and Duct cleaning be performed on a yearly basis.

Finally, specific filters that are regularly changed can help capture airborne skin flakes before they enter the AHU.

“The size of skin squames is generally larger than 10 micrometers (or 0.001 centimeters).” Dr. Lai says, “A filter that can effectively capture particles less than this size should help improve the odor problem.”

In conclusion, when ammonia and body odor types of smells arise the likely culprit is skin flakes and bacteria in the HVAC system. Best practice is to test the conditions of building and systems to establish the nature and severity of the issue. Then a plan can be established to remediate the situation. Of course, maintaining a proactive, hygienic, HVAC and Duct cleaning program will always help to ensure skin squames and bacteria are kept to a minimum while indoor air quality remains optimal.

Further Reading

The study entitled “Skin squames contribute to ammonia and volatile fatty acid production from bacteria colonizing in air-cooling units with odor complaints” was published in Indoor Air (DOI: 10.1111/ina.12439). Another related study entitled “Viable airborne microbial counts from air-cooling units with and without complaints of urine and body odors” was published in Aerobiologia (DOI: 10.1007/s10453-016-9466-y).

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Environmental Measure Aides Asthma Interventions

A newly developed Environmental Scoring System (ESS) proved useful in a variety of home-based asthma intervention programs despite differences in settings, staffing, populations, and administration.

The ESS was developed by the Massachusetts Department of Public Health to help address the highest asthma prevalence in adults among US states. Massachusetts is also confronting one of the highest percentage of children with uncontrolled asthma and the associated high rates of emergency department visits, hospital admissions and school absenteeism, according to rankings by the Centers for Disease Control and Prevention (CDC).

Zhao Dong, MS, ScD, Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA, and colleagues who tested the ESS in several community-based programs considered these healthcare challenges, and the efforts to address them.

“There is evidence that asthma disparities can be substantially reduced by comprehensive care, both through the health care system and through home-based intervention programs,” they wrote.

The ESS yields a composite score ranging from 0 to 6 from a binary score of 0 or 1 for each of 6 asthma triggers: dust, mold, pests, smoke, pets, and chemicals. In preliminary assessments, the ESS was reduced at the end of a series of home visit interventions. The questions remained as to whether the ESS could be incorporated into various and differing intervention programs and relate to clinical outcomes.

“Given the large variability in the implementation of specific asthma programs and design of survey questions to collect information on asthma triggers, it is unclear whether ESS would be a good approach for measuring environmental triggers and predicting asthma outcomes across different programs and populations,” Dong and colleagues wrote.

In an editorial accompanying the evaluation of the ESS, Delaney Gracy, MD, MPH, Chief Medical Officer, Children’s Health Fund, New York, NY, emphasized the importance of developing and validating such tools.

“In a time when our health system is increasingly focused on quality measures, value-based care incentive models, and quantitative impact assessment, well-designed tools, methods and comparative values are keys to meaningful data and the assimilation of information that can drive change,” Gracy wrote.

Dong and colleagues evaluated the ESS in 6 community asthma intervention programs, including the Boston Public Health Commission Asthma Home Visit Program (BPHC), the Boston Children’s Hospital Community Asthma Initiative (CAI), and Tufts Medical Center Floating Hospital for Children Asthma Prevention and Asthma Initiative (Tufts).

Among all participants, the completion of intervention visits was marked by an increase in the average of total scores on the Asthma Control Test, corresponding to reduction in symptoms, and a reduction in the number of emergency department visits and in ESS scores. The magnitude and statistical significance of the changes varied between programs, however.

Dong and colleagues found that statistically significant reduction in total ESS was primarily driven by reduction in the mold score in the BPHC and CAI  programs.

“Nevertheless, total ES was able to capture the overall variability in environmental triggers over visits regardless of the performance of each individual score,” they wrote.

All the studied programs improved asthma outcomes to varying degrees, and the ESS tool appeared to be widely implementable, without much variation of program and survey designs, Dong and colleagues indicated.

Gracy welcomed evidence that the measure could be useful to the intervention programs.

“This type of tool has the potential to be very important in creating needed cross-program comparisons, setting benchmarks of success, accumulating impact data to support intervention reimbursement, and facilitating the impact assessment of individual programs,” Gracy wrote.

The study, “Evaluation of the Environmental Scoring System in Multiple Child Asthma Intervention Programs in Boston, Massachusetts,” was published online in the American Journal of Public Health.

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Missouri Maps and Reports Radon Testing in Public Schools

The Missouri Department of Health and Senior Services provides radon information for the public, including data on radon testing in public schools. Most of the state’s counties are in Zone 2, the USEPA classification, where predicted average indoor radon screening levels would be from 2 to 4 pCi/L. Eleven counties are in Zone 1, where predicted average indoor radon screening levels greater than 4 pCi/L, the recommended USEPA action level.

Interactive mapping of radon testing in public schools allows filtering by county and school name in order to zoom to results or statewide data can be viewed of all counties and districts. Selections include public schools and districts tested. Map background may be chosen.

Tabular data breaks out data per the school year (August through May). The data are available from the department’s Bureau of Environmental Epidemiology, Indoor Air Quality Database.

For the school year 2013-2014, elevated levels of radon were reported in 13.79% of the 145 structures tested. The number of school districts tested was 28, with 107 schools being tested. Classrooms tested equaled 3050 and of those 82 had elevated results. The estimated number of people potentially exposed, which includes students, teachers and others, was 114,402. During the school year 2014-2015 the number of potentially exposed dropped to 91,962.

For more information about radon in Missouri, contact:
Bureau of Environmental Epidemiology
Telephone: 573-751-6102 or (toll-free) 866-628-9891

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Air Quality Visibly Bad From Brush Fires Burning In Ventura, Sylmar

VENTURA (CBSLA) — With two large brush fires burning in Los Angeles and Ventura counties, air quality was visibly bad Tuesday, even with strong winds blowing much of the smoke out onto the ocean.

Our radar picking up smoke from the – poor air quality… blaze has now burned 45,000 acres with zero containment

A large bank of smoke from the Thomas Fire was visible from SKY2 over Ventura, Santa Paula and Ojai. The strong winds that are pushing flames west are similarly scattering plumes of gray smoke out over the region.

Further inland, the Creek Fire burning over Sylmar is giving an apocalyptic hue to the morning commute along the 5 Freeway.


Horrible air quality in the valley this morning due to the as viewed from Mulholland Drive. Most of the valley can’t be seen from up here.

Further inland, the Creek Fire burning over Sylmar is giving an apocalyptic hue to the morning commute along the 5 Freeway.

SMOKE ADVISORY: the near and is affecting our air quality:

A smoke advisory issued by the South Coast Air Quality Management District says that wind-blown smoke is making the air most hazardous in the San Fernando Valley and Malibu areas. The agency says everyone in these areas should avoid vigorous outdoor or indoor exercise, and people with respiratory or heart disease, pregnant women, seniors, and children were urged to remain indoors.

More than 50 miles away, officials from the Santa Monica-Malibu Unified School District said that even though classes are in session, students are being kept indoors due to smoky conditions.

“School is in session; however, we will be running on an indoor schedule today, including for physical education, lunch and recess,” a statement from Superintendent Ben Drati posted on the district’s website said.

The Thomas Fire also forced the Getty Center to close to the public “to protect collections from smoke from fires in the region,” according to Getty officials. The Villa in Pacific Palisades is also closed, per its usual Tuesday schedule.

Southern California is enduring its second day of destructive Santa Ana winds that are being blamed for whipping up flames from both brush fires and sending embers beyond fire lines to start new fires.

Red Flag warnings, signifying the risk of wildfires, remain in effect across most of Los Angeles County and down south into Orange County. Tuesday’s warnings are scheduled to expire at 6 p.m., but forecasters say Santa Ana winds could persist into Friday or Saturday.

The gusty winds also have the potential to bring down trees and power lines, and already brought down several big rig trucks along the 210 Freeway in Fontana.

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42 Lenox Hill Cooling Towers Tested Positive For Legionella Bacteria, City Says

42 Lenox Hill Cooling Towers Tested Positive For Legionella Bacteria, City Says

LENOX HILL, NY — After testing every cooling tower in the Lenox Hill neighborhood following a June outbreak of Legionnaires’ disease, the city Department of Health found that more than 40 towers tested positive for trace amounts of Legionella bacteria, a department spokesman told Patch.

The city tested the neighborhood’s 116 cooling towers and found that 42 towers had trace amounts of the bacteria, the Department of Health spokesman said. Of those 42 towers that tested positive, 24 had levels that could cause the disease to spread to humans, according to the spokesman The city has ordered buildings to fully clean and disinfect the towers that tested positive, but has not identified where the towers that tested positive are located.”During the field investigation, disease detectives closely monitored laboratory reports for any additional cases while water ecologists sampled every cooling tower in the cluster area,” the spokesman said in a statement sent to Patch.

“Approximately 100 Health Department personnel were involved in the response as they sought to prevent additional cases and raise awareness. The Health Department has the most sophisticated disease monitoring system of any municipal health department in nation – every day, disease detectives monitor hospital emergency departments and laboratory reports for over 75 reportable diseases, and water ecologists quickly respond to environmental hazards related to Legionnaires’ and other diseases to keep New Yorkers safe.”The tests were conducted after the city identified a Legionnaires’ disease cluster in the Lenox Hill neighborhood in June. During the outbreak seven people were hospitalized after contracting the disease. Of those seven people, one person who was elderly and had “significant underlying health conditions” died, the Department of Health said in June.After the June 16 outbreak one more person who worked in the area became sick with Legionnaires’ disease and was hospitalized, but has recovered, a Department of Health spokesman said.The city has closed its investigation into the Legionnaires’ cluster even though it was unable to discover the source of the outbreak. The Department of Health is rarely able to match a patient’s DNA with the source of an outbreak such as a cooling tower, a department spokesman told Patch.Legionnaires’ symptoms include fever, cough, chills, muscle aches, headache, fatigue, loss of appetite, confusion and diarrhea and generally surface two to 10 days after contact with the bacteria Legionella. Common culprits in the spread of the Legionella bacteria include cooling towers, whirlpool spas, hot tubs, humidifiers, hot water tanks, and evaporative condensers of large air-conditioning systems, the Department of Health said.The disease cannot be spread from one person to another, the Department of Health said in a statement.

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Sick Building: Fungi Release Toxin Directly Into Air, Study Finds

Toxins from mold can aerosolize directly into the air, which may help explain one cause of sick building syndrome, French researchers said Friday.

Mold growing in buildings can make people sick, especially people who are allergic to various fungi. It’s also known that various molds and fungi produce mycotoxins — chemicals that can sicken and even kill people and animals.

What’s not been entirely clear is how mold growing in and on walls or elsewhere in buildings might make people sick.

Jean-Denis Bailly of the University of Toulouse in France and colleagues tested three common types of fungi that can grow inside buildings and found that their mycotoxins could and did disperse into the air until normal conditions.

“These toxins can subsequently be aerosolized, at least partly, from moldy material,” they wrote in their report in the journal Applied and Environmental Microbiology, published by the American Society for Microbiology.

“This transfer to air requires air velocities that can be encountered in ‘real life conditions’ in buildings.

The three species they tested were Penicillium brevicompactum, Aspergillus versicolor and Stachybotrys chartarum, all of which grew on wallpaper in their lab.

They all also produce mycotoxins.

Related: These diseases are a growing threat, U.N. says

“It is estimated that, in Northern Europe and North America, 20 percent to 40 percent of buildings display macroscopically visible (visible to the eye) fungal growth,” they wrote.

“For instance, Aspergillus versicolor, a potent producer of sterigmatocystin (STG), is one of the most frequent fungal contaminant of indoor environments that can be found together on building materials, in dust or in the air samples.”

 Here are unexpected places mold might be lurking in your home: Rossen Reports Update 4:44

The team first grew the three fungi on ordinary wallpaper, and then tested to see if the toxins they produce could get into the air without some sort of interference, such as tearing down walls.

Related: EPA workers say their building is a sick one

“We demonstrated that mycotoxins could be transferred from a moldy material to air, under conditions that may be encountered in buildings,” Bailly said in a statement.

The pieces were as small as or smaller than spores and “could be easily inhaled by occupants and deeply penetrate into (the) respiratory tract,” they wrote.

“It seems important to take these data in consideration for risk assessment related to fungal contamination of indoor environment and the possible toxicity associated to inhalation of these toxins.

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