CLEAN Lessons Learned
Making Confidence Our Travel Companion: Managing the environment to reduce transmission in public transport
Returning to public transport, especially after the removal of mask mandates, had led to widespread uncertainty.
With a focus on rebuilding confidence in our public transportation systems through scientific understanding, this session was Part 1 of a two-part series titled “Making Confidence our Travel Companion.”
We joined experts as they examined the technological challenges and opportunities in the transportation sector, guided by some of our leading scientists and practitioners in indoor air quality and bioaerosol research, pathogen detection and monitoring, infection control and decontamination, public transport air management systems, and emergency response to airborne threats.
- Importance of Confidence: The return to public transport, especially post-mask mandates, necessitated rebuilding confidence for passengers. Ensuring safety became a priority.
- Public Transport and Airflow: Joshua Pitcher highlighted the similarities between bus and train air management systems, emphasizing the challenges posed by horizontal air movement.
- Alternative Filtration: Ted Cowan and Yair Hazi discussed electrostatically charged filter media and its effectiveness. Over time, however, electrostatic filters can lose efficiency as they become coated with dust.
- Emerging UV Technology: Both Brett Cole and Zaheer Nasar touched on the utilization of UV technology, particularly in settings like public transport, to disinfect air. The efficacy and safety of UV were underscored, with the concern of ozone production being highlighted.
- IoT in Air Quality Monitoring: Brett Cole emphasized the potential of Internet of Things (IoT) technologies to monitor and improve air quality in real time.
- Ventilation Design: The importance of understanding the existing ventilation design when retrofitting public transport systems was emphasized by Zaheer Nasar.
- Pathogen Detection in Public Transport: There’s an emerging interest in real-time pathogen detection within transport systems. Zaheer Nasar and Yair Hazi provided insights with differing opinions on the feasibility and effectiveness of such systems.
- Public Perception vs. Scientific Evidence: Zaheer Nasar highlighted the challenge of correlating public perception with scientific evidence, especially regarding public transport safety.
- Secondary Exposure Issues: Brett Cole stressed the importance of ensuring that while solving one problem (like pathogens), we don’t create secondary issues, like ozone production.
- Holistic Approach Needed: The session underscored the need for a holistic approach that combines technology, science, and public assurance to ensure safe and confidence-inspiring public transport systems.
IBEC’s COO, Board founding member, and Secretary
Ted has more than 30 years of experience in disaster preparedness and emergency management, strategic and operational planning, training, exercise coordination, and operational support. He brings a unique combination of analytical, lessons learned, and vulnerability experience assessment proficiency. He has a command of requirements development related to disaster response and the formulation of comprehensive mitigation strategies.
Managing Director & Chief Occupational Hygienist at Biosafety Pty Ltd
Brett Cole is Managing Director/Chief Occupational Hygienist – Biosafety International/Member of Indoor Air Quality Association of Australia and Education & Training Committee (ETC) of Association for Biosafety for Australia and New Zealand.
Zaheer Nasar, PhD
Academic Fellow in Atmospheric Aerosols at Cranfield University.
His research interest lies in the physicochemical and biological characterization of aerosols, their spatio-temporal dynamics in different environments, societal impacts, and developing control measures, with a specific focus on particulate matter (PM) and bioaerosols, across natural and indoor environments.
Former faculty member at the Columbia University’s Mailman School of Public Health, Department of Environmental Health Sciences
Dr. Hazi is a highly skilled and experienced environmental health scientist with a proven and diverse record of accomplishment in government consulting, industry, and academia.
For over 20 years, she has conducted research on public health emergency management, focusing on community resilience, behaviorally realistic emergency plans, public engagement in disaster planning, post-epidemic recovery, and crisis and emergency risk communication.
Ted Cowan 00:06
Partners and IBEC members, welcome to our July “Lessons Learned” panel discussion. Today, we are delighted to have attendees and panelists from around the world join us to consider how we can travel with more confidence during times of high respiratory infection spread. Initially, this introduction was to be joined by my colleague Claire Bird, the Executive Secretary of IBEC. However, due to technical difficulties amidst the realities of COVID, she’s currently unable to tune in. This panel discussion marks the first installment of a two-part transportation webinar series. It focuses on how our transport mechanisms can shield us, harnessing current innovations in the transport realm. Our subsequent session in August will turn its attention to the protection strategies employed during travel itself. At IBEC, we’re anchored in the belief that discussions should be rooted in scientific understanding. Given the longevity with which pandemic viruses might persist, our approach to future planning calls for strategies that extend beyond simply addressing airborne transmission and the immediate threat of COVID. With this framework in mind, I’d like to initiate today’s discussion. By way of introduction, my professional journey began in the Navy as a helicopter pilot, later transitioning into the spheres of emergency management and disaster planning. My extensive involvement in pandemic planning, especially post the H1N1 episode in 2009-2010, illuminated the need for a different approach when COVID made its appearance. This realization led to the inception of IBEC. Today’s panel holds a special significance for me, given my foundational ties to aviation and transportation. The brunt of COVID’s impact was significantly felt in the transportation sector, especially within the realm of public transportation. Even today, many regions around the globe report public transportation ridership levels that languish well below pre-COVID benchmarks. The shift to remote work and a preference for personal vehicles over public transit, predominantly stemming from COVID-related apprehensions, is notable. Yet, in parallel, there’s a burgeoning global consensus on the pivotal role of public transit as a conduit to reduce carbon emissions. This posits public transportation as a cornerstone in the larger initiative to combat climate change, urging a pivot from individual vehicles to more carbon-efficient transit alternatives. Today’s dialogue, therefore, intersects with two monumental challenges of our time: climate change and the management of infectious diseases. As we navigate through this session, we encourage active participation. Previous attendees might recall the chat feature on the platform; please feel free to submit your questions in real-time. We’ll collate and address these during our Q&A segment towards the session’s culmination.
To commence today’s proceedings, I’d like to introduce Dr. Zaheer Nasar. Dr. Nasar is an esteemed academic fellow specializing in atmospheric aerosols at the School of Water, Energy, and Environment, Cranfield University, UK. His expansive research delves deep into understanding the dynamics of indoor and outdoor pollutant emissions, their sources, and the corresponding exposure patterns, ultimately focusing on addressing the adverse impacts of compromised air quality. Dr. Nasar’s meticulous research zeroes in on the intricate physical, chemical, and biological intricacies of aerosols, weaving in the broader societal implications. With an unwavering commitment to creating pragmatic solutions, he confronts both current and future environmental and public health challenges, spanning across both natural and constructed environments. Prior to his association with Cranfield University, Dr. Nasar contributed his expertise at the School of Biological Science, University of Essex, and the University College London, working on a myriad of projects exploring the nuances of air pollutant dynamics. Dr. Nasar, the floor is yours. Please share with us your insights and what you deem paramount for today’s discussion.
Zaheer Nasar 04:53
Thank you, Ted, for that comprehensive introduction. Engaging with the wider public and building confidence is paramount. Viruses, or as I often refer to them, particles, have coexisted with us. The inherent risk lies in their concentration and the duration of exposure. I’d like to take this opportunity to provide a brief overview of my work, centralizing on the comprehensive understanding of airborne particles. My approach bifurcates into two core elements: characterizing aerosol emissions and understanding their relation to public health implications and controls. A holistic perspective, understanding the intersection between particles, environmental dynamics, and human exposure is pivotal. Harnessing advancements in real-time data analytics and systems thinking, I aim to transform our understanding of aerosols. Governments globally are ramping up support for research in air quality and airborne disease transmission, especially in the wake of the COVID-19 pandemic. I’m honored to be part of multiple projects spearheaded by research councils within the UK. My scholarly pursuits encompass aerosol characterization, real-time diagnostics of indoor air quality, environmental control strategies for airborne diseases, and the resilience of bio-infrastructures. Considering today’s theme, transportation environments present unique complexities, shaped by diverse pollutant sources, varying environmental conditions, and distinct occupancy patterns. My work strives to understand these intricacies, assessing the efficacy of various control measures within the ambit of transport environments.
Ted Cowan 10:35
Thank you very much, Dr. Nasar. I’m eagerly anticipating our discussion and truly value your presence on this panel. Next, I’d like to introduce Dr. Yair Hazi, a former colleague with whom I collaborated in the federal sector. Dr. Hazi is an esteemed environmental health scientist, showcasing a vast and diverse track record across government, consulting, industry, and academia. With expertise in the chemical, biological, radiological, and nuclear domains, Yair has specifically honed skills in detection, program development, coordination, management, threat agent detection technologies, citywide emergency preparedness, and response planning. Furthermore, he has specialized in biological remediation, recovery, air modeling, aerosol science, technology, Homeland Security, and the Homeland Security Exercise and Evaluation Program. Boasting over 15 years of experience as a federal consultant, Dr. Hazi has expertly managed and coordinated a complex, federally funded urban biological threat agent detection and response program, seamlessly working with multiple stakeholders from various government tiers. Recognized as a subject matter expert, he has been a pivotal member of several scientific technical working groups, addressing key issues around biological attack preparedness, as well as environmental and public health responses. Prior to his current endeavors, he served on the faculty at Columbia University’s Mailman School of Public Health in the Department of Environmental Health Sciences, undertaking research on the impact of indoor and outdoor pollution on vulnerable populations. An acclaimed author, he has significantly contributed to academic journals and has been an invited speaker at numerous national conferences in the US. Dr. Hazi, could you enlighten us with your perspective and contribution to today’s panel discussion?
Yair Hazi 12:23
Thank you, Ted, for the comprehensive introduction. I’m honored to be part of this significant panel and am optimistic about a constructive and insightful dialogue. As you pointed out, there’s an understanding that pandemic viruses, like COVID, might persist among us for an extended period. Consequently, our focus should be on how to travel safely amidst elevated infection rates. In the upcoming minutes, I intend to shed light on prevalent technological solutions designed to control the spread of the virus, specifically targeting environments like the New York City subway system, a primary mode of transportation in the city. At this juncture, I’d like to share some slides to provide visual context. To optimize bandwidth, especially with other family members currently using Zoom, I’ll momentarily turn off my camera and resume video once I conclude my presentation.
The NIOSH hierarchy of controls offers a robust framework to discern effective control measures, be it in organizations, workplaces, or communities, and is instrumental in gauging optimal methods to reduce exposure to hazards. The pyramid’s broad base represents the most effective controls, tapering down to the least effective ones. In the case of transportation systems, the total elimination of the COVID source isn’t feasible. However, during the pandemic’s peak, many chose to avoid using these systems, leading to a precipitous decline in ridership in New York City, with subway use plunging to 8% and buses to 23% compared to pre-COVID numbers.
Substitution, which involves replacing the hazard with a less perilous alternative, isn’t directly achievable either. Still, the surge in remote work and distance learning can be construed as a form of substitution. Engineering controls, on the other hand, involve strategies like physical barriers and enhanced ventilation, isolating individuals from hazards without eliminating them. These need to be complemented with measures like masks for optimal efficacy.
The sheer size and complexity of retrofitting control systems, especially in large fleets like New York City’s Metropolitan Transportation Authority, present substantial challenges. The Authority’s rolling stock encompasses over 200,000 commuter rail cars and nearly 6,500 subway cars, serving millions daily.
In conclusion, I’d like to share an animation clip sourced from The New York Times, elucidating the movement of air and particles within a subway car. The visualization underscores the challenges in retrofitting such environments with control technologies. Do keep in mind, while viewing, the distinct color codes: recirculated air is denoted by yellowish-brown arrows, fresh air by purple arrows, and filtered cool air by blue arrows. The dual supply ducts, represented by yellow lines, run along the ceiling on either side, aiding in air recirculation. With that, I look forward to our discussion.
Ted Cowan 22:28
Thank you, Yair. I sincerely value your input. Our journey takes us from the UK, through New York, and now to Australia. Let me introduce our next panelist, Joshua Pitcher. Joshua is a chartered engineer and a proud fellow of Engineers Australia. With over 25 years in the field of engineering, Joshua has dedicated more than half of his career to the transport sector. He’s deeply rooted in electronics, signal processing, systems engineering, and in recent times, has shifted to technical leadership. In 2012, Joshua became an integral part of Nora Bruns, Australia, taking the role of engineering manager for Merit, the HVAC brand of Mora Brands. Steering a formidable team of 35 engineers from diverse specialties, Joshua delves into custom HVAC developments tailored for rail, mining, heavy industry, and defense sectors. Merit, with almost half a century of experience in HVAC systems, has global footprints. If you’ve been on a train in cities like Hong Kong, Taiwan, Vancouver, Doha, Rio, Bangalore, or even the east coast of Australia, chances are high that your comfort was courtesy of an air conditioning unit designed by Joshua’s team down under. Boasting state-of-the-art R&D facilities, including wind tunnels, rapid prototyping software, and FBA modeling capabilities, Merit invests nearly half a billion euros annually in R&D. This commitment ensures that they remain pioneers in HVAC technology. Since 2020, Joshua and his dedicated team have invested time and resources into researching and validating air purification and filtration technologies for passenger rail, emphasizing the dual responsibility of HVAC systems to provide both conditioned and clean air. Over to you, Joshua.
Joshua Pitcher 24:19
Thank you, Ted, for such a gracious introduction. It’s truly an honor to be amidst this group of experts. I might feel a tad out of my depth among all these doctors, and potential doctors as I learned earlier, but I’m here to share insights from my field, focusing on how we’ve assessed and implemented novel technologies for public transport. My tenure in the HVAC industry spans a decade, and the recent years have been especially enlightening. The pandemic threw into sharp relief the vulnerability of public transport passengers and underscored the pivotal role my domain could play in enhancing safety. Even as the risk profile of COVID has evolved – with the advent of vaccines and deeper understanding of the virus – the health implications persist. There’s an ongoing potential to effect widespread health improvements, both now and for future scenarios. My engineering pursuits concentrate on validating and introducing these innovations into public transport, always aiming to direct palpable benefits to the passengers. Thank you for having me here.
Ted Cowan 25:37
Thank you, Joshua. Your insights are invaluable. And, drawing from my time as a helicopter pilot, I can empathize with your sentiments about being amid a sea of doctors. Moving on, our next contributor is Brett Cole from Australia. Representing Biosafety International, Brett was a pioneer, being the inaugural international voice in the US Technical Working Group focusing on COVID-19 decontamination in early 2020. This experience catalyzed the conception of the IBEC Clean 2020 Summit Series that debuted in June 2020, running through its sixth iteration earlier this year. Brett’s expertise, spanning over two decades, bridges contamination control across high containment arenas in life sciences, healthcare, and food & beverages. Backed by formal training in environmental microbiology, chemistry, and subsequently in occupational hygiene and toxicology, Brett’s portfolio includes academic research in microbiology, high-level disinfection medical devices, contamination control engineering, infectious and contaminated water management, facility microbial testing, and decontamination endeavors. His global footprint covers Australia, New Zealand, North America, Asia, and the Pacific, handling a plethora of contamination projects. During the COVID-19 crisis, Brett collaborated with two federal government taskforces focusing on PPE, ventilators, and IAQ guidelines for contamination validation in buildings. Brett, we’re eager to hear from you.
Brett Cole 27:32
Thank you so much, Ted. Being part of IBEC’s initiative is indeed a privilege. One overarching lesson from COVID-19 is the irreplaceable value of accurate, timely, and scientifically endorsed information, guiding the masses towards safer futures. Research underscores the pivotal role of individual awareness in the realm of public transport. Studies from China indicate that well-informed individuals exhibit a higher propensity to return to public transport. This sentiment of safety is pivotal. Our unique challenge encompasses the unpredictable nature of public transport, with its transient population, fluctuating loads, frequent high-touch surfaces, prolonged vehicle operation times, and the inherent challenge of consistent visual messaging in crowded situations. Today, as we unravel novel methodologies and innovations aimed at making transport safer, I hope our discourse will dispel misinformation, instill confidence, and emphasize the critical role of public transport safety. Thank you for this opportunity.
Ted Cowan 33:16
Thank you, Brett. At this juncture, we’ll start delving into some questions for our panel. We have a set of predetermined questions, but I’d like to remind our audience to submit their queries via the chat. We’ll ensure they are addressed promptly. Let’s start with you, Zaheer. Could you highlight the knowledge gaps concerning how public transport microenvironments might contribute to infectious disease transmission pathways? What obstacles do we face when trying to differentiate between surface and airborne transmission routes?
Zaheer Nasar 34:02
Certainly, Ted. From an academic standpoint, there are multiple ways to approach this. But one of the most pressing research gaps revolves around understanding the interaction between biotic (living) and abiotic (non-living) factors. For instance, when someone exhales a particle, it contains a biological component, like the virus, surrounded by non-biological elements. This combination is then exposed to environmental conditions as it travels through the air from the source to the receptor. Applying this concept to public transport microenvironments, we must examine the conditions, both resulting from design and operation, which influence this particle’s behavior in the air.
One of the significant challenges lies in discerning the interaction between the biological and non-biological components of these particles. This is crucial because while we have a clear understanding of factors that amplify exposure risks (like overcrowding and environmental elements like temperature and humidity), the factors that increase the risk of infection are less clear.
To simplify, when someone exhales the SARS-CoV-2 virus, it’s not in a pure form but mixed with other elements. This combined particle undergoes transformations as it’s exposed to various factors before becoming a droplet nuclei, which can then be inhaled. The significant challenge we’re currently trying to understand is how these environmental factors affect the viability of the biological particles in the air.
Our knowledge allows us to model and predict particle behavior based on their size. But until recently, due to methodological challenges, we had limited knowledge about the biological component’s contribution to the particle’s total behavior. Fortunately, advancements have equipped us with real-time systems that can more accurately assess the biological composition of these airborne particles.
Ted Cowan 38:27
Thank you for that perspective, Zaheer. Would any other panelists like to comment or add to Zaheer’s insights?
Brett Cole 38:35
Yes, Ted. I’d like to expand on the latter part of the query about distinguishing between surface and airborne transmission routes. As our understanding evolves, thanks to the invaluable work from researchers like Zaheer, it becomes apparent how pivotal this knowledge is in guiding public behavior. Recall the early days of the pandemic: the primary concern was fomite transmission, or transmission via touch. We invested significantly in surface cleaning and innovative disinfectants. Some even claimed to protect surfaces for up to 90 days!
However, as the discourse shifted to airborne transmission, the emphasis changed. We began discussing air change rates, HEPA filtration, and even using carbon dioxide levels as a proxy for infection risk. It’s clear that the pendulum has swung towards airborne considerations. Not to say that fomite transmission isn’t essential, but our foundational research now focuses primarily on airborne routes.
This evolution in understanding is crucial. As we continue to understand these pathways better, individuals can make informed decisions, increasing their comfort and safety in public transport. Often during this pandemic, I felt we were re-learning what we already knew, applying established knowledge to new scenarios. Such adaptability and reapplication will be key as we move forward.
Ted Cowan 40:59
Does anyone else have input before we proceed? Joshua, given the prevailing global advice for indoor environments, which emphasizes increasing ventilation, opening windows, and adjusting HVAC dampers, is this advice applicable for public transport?
Joshua Pitcher 41:21
Thank you, Ted. There’s a stark contrast between indoor spaces in buildings and those within public transport. One key difference is the space itself. Buildings typically have a more expansive internal volume and are sparsely populated, with limited common touch points. Using my workplace as an example: I have my own workspace, chair, keyboard, and personal items. The density there is around one person per 16 square meters. In contrast, for public transport like trains, the design can accommodate up to five passengers per square meter. Furthermore, the internal height in trains, especially in double-decker trains in Sydney, isn’t much more than 2.1 meters. This difference in density affects how air flows and interacts within these spaces.
Buildings benefit from increased ventilation as the vast internal space and multiple air paths help disperse and replace air efficiently. However, in public transport, such as trains, almost all the air in the compartment passes by virtually every passenger due to the design of the air conditioning systems. This makes it imperative to reduce person-to-person transmission within that single air cycle. While trains are well-ventilated, enhancing this ventilation further might not be straightforward. Increasing the intake of fresh air can strain existing air conditioning systems, leading to inadequate heating or cooling. Additionally, increasing ventilation can amplify other issues like noise and door pressurization.
Moreover, retrofitting thousands of existing train cars is a monumental task. For instance, even if each car took two days to upgrade – which is a highly optimistic estimate – it translates to a multi-year endeavor for a large fleet.
Lastly, we must consider touch-points within public transport. Even as we focus on air quality, high-touch areas within public transport vehicles like handles, grab rails, and seats remain a concern, further emphasizing the need for comprehensive sanitation measures.
Ted Cowan 47:31
Thank you, Joshua. Would anyone else like to weigh in on this discussion?
Yair Hazi 47:37
To add to Joshua’s points on ventilation, some trains can benefit from enhanced ventilation. Unlike building HVAC systems, which are adjustable, current subway cars are fixed at a 25% fresh air intake. Perhaps future designs could incorporate adjustable ventilation systems similar to buildings. Another possible lesson from this pandemic is the airflow direction. For instance, the design used in the San Francisco Bay Area subways, where airflow is directed from wall to floor, might be more effective than the current side-to-side airflow in many trains.
Joshua Pitcher 48:56
Absolutely, Yair. Comparing airflow in trains to that in aircraft showcases the differences. Aircrafts, with their top-to-bottom airflow, manage air quite effectively. New train designs might benefit from focusing on this vertical air movement over the prevalent horizontal flow. This then leaves the challenge of managing risks in the existing fleet.
Ted Cowan 50:01
Considering this conversation, I’d like to address a question from our audience. It pertains specifically to the cleanliness of air. How clean is the tunnel air that’s pulled into transit modules, such as those in New York City, London, or Beijing subways? And how proficient are filters in eliminating bio-infectious aerosols from passengers? Are there any quantitative models available for reference?
Joshua Pitcher 50:33
To provide some practical insights before the experts dive in deeper, we know tunnels contain water particles and debris. MERV seven or MERV eight filters effectively remove dust and debris, particularly particles larger than about five microns. These are the particles that might provoke respiratory reactions in individuals. However, these filters aren’t designed to tackle microbial particles, which can be much smaller. That’s why there’s a shift towards discussions about HEPA filters. While HEPA filters are known for their efficacy, retrofitting them into public transport systems presents challenges. They can introduce pressure drops and increase resistance, leading to issues with air conditioning performance and energy usage. A potential solution could be alternative technologies like electrostatic filters, which offer sub-micron particle filtration without the usual pressure drop associated with high-efficiency filters.
Ted Cowan 53:51
This leads nicely into our next topic. While we’ve touched upon filtration, the built space has seen a shift towards HEPA filtration. Are there any emerging technologies or adaptations that might be suitable for public transport given its unique challenges compared to traditional building spaces?
Brett Cole 54:39
Numerous emerging technologies are being explored. Joshua and Dr. Nasar mentioned UVC technology, which has been around for a while and is well-recognized for its effectiveness. We’re now trying to adapt such proven technologies to new contexts, such as public transport. Ionization systems, traditionally used for mold remediation, might offer solutions. Additionally, there are disinfectants that claim to protect surfaces from viral transmission. While many of these technologies aren’t necessarily novel, the challenge lies in adapting them to public transport systems. It’s crucial to understand how they can be retrofitted, their effectiveness against airborne diseases, and potential side effects, such as ozone production.
Zaheer Nasar 56:31
Yair has indeed provided a comprehensive overview of the current technologies. Brett highlighted that many of these technologies have been with us for the past 20-40 years. Primarily, these engineering controls have shown efficacy in healthcare built environments and biological containment facilities. The challenge now is to determine how we can translate these controls, especially the engineering ones, to public transport.
Alongside the various methods of filtration, UVGI (Ultraviolet Germicidal Irradiation) has a track record of being effective. But introducing such technologies to public transportation is not without its complexities. Some technologies might be more apt for in-vehicle environments, while others may be best suited for associated infrastructure.
Emerging technologies that were researched and developed post the SARS outbreak from places like Hong Kong include the use of antimicrobial surfaces. While these surfaces have shown promise in lab settings, their real-world application, like within trains paired with photocatalytic oxidation systems, remains debatable.
Moreover, a pertinent question remains: How do we define biologically clean air for public environments? And at what point do increasing ventilation rates become counterproductive or result in diminishing returns?
As academic researchers, our endeavors should be directed towards solutions driven by the demands and requirements of the industry rather than just supply-driven innovations.
Ted Cowan 1:01:39
That’s a valuable point to consider. Would anyone else like to contribute to this discussion?
Yair Hazi 1:01:41
To expand on that, when we discuss the implementation of these viable technologies, the primary concern for transportation systems becomes how to integrate these current technologies in a way that’s compatible with existing infrastructure and systems. For instance, specific train car manufacturers are now exploring the concept of modular HVAC systems. These systems can be seamlessly swapped out, providing flexibility in response to changing needs. Hence, technology manufacturers should closely collaborate with transportation agencies to cater to the distinct challenges of public transportation.
Brett Cole 1:02:49
Adding to what’s been discussed, any antimicrobial treatment necessitates the right balance of concentration and exposure duration. Whether we’re talking about UV or disinfectants, they need a specific concentration and a sufficient exposure time to be effective. So when retrofitting any technology, it’s vital to ensure that it’s placed where it can guarantee the required air residence time for maximum efficacy.
Furthermore, given the lack of standard exposure levels for bioaerosols, it’s crucial to note that individuals react differently to these. Crafting a safe environment in public transport demands a combination of various technologies. It’s a layered approach, and there’s no single solution that will cater to all requirements.
Ted Cowan 1:04:51
Thank you for that, Brett. Let’s shift our focus a bit and address another question from our audience. While we’ve delved deep into the intricacies of rail, what about buses? Do public buses have similar high ventilation rates as trains? Can the existing ventilation systems in buses handle the pressure that comes with MERV 13 filters? What would be the challenges associated with upgrading these filters specifically for buses?
Zaheer Nasar 1:05:32
To address that, we recently hosted a seminar in the UK, where we engaged with industry representatives. We learned that ventilation in buses can vary significantly. While intercity buses are equipped with mechanical ventilation systems, many city buses predominantly rely on natural ventilation. During the pandemic, a strategy was adopted wherein windows on these buses remained consistently open. While this ensured ventilation, it inadvertently led to a surge in heating costs due to the continuous heat loss.
When we discuss mechanical ventilation in buses, the principles are somewhat similar to train cabins. However, buses that are naturally ventilated present their unique set of challenges, which need tailored solutions.
Joshua Pitcher 1:07:25
While I don’t have extensive experience with buses, I can say that air flows in buses are contextually similar in terms of horizontal air movement to trains. Buses typically house a unit towards the rear, allowing one return air inlet at the back, with ducting that usually spans the ceiling length. This creates the familiar problem of horizontal airflow passing over many passengers. As for specific fresh air quantities or the impact of filters, I’d recommend reaching out to the original equipment manufacturers of the buses. They could offer analysis regarding the resistance an advanced filter might introduce, and its implications on airflow, comfort, and more. It’s worth noting there are technologies available that offer high filtration efficiencies without a significant pressure drop, but each comes with its own pros and cons.
Ted Cowan 1:08:44
Joshua, following that, could you shed light on whether the installation of electrostatically charged filter media can enhance filtration without the need for higher MERV filters?
Yair Hazi 1:09:04
Initially, electrostatic filters seem promising. However, in heavy-load environments like the New York City subway system, these filters lose efficiency as they accumulate dust. Unlike traditional filters which become more efficient with loading, electrostatic ones decline in performance. As the fibers of these filters get coated with more dust, they lose their electrostatic capability. Thus, an initially efficient electrostatic filter can quickly drop to the performance level of a lower MERV-rated filter within a few days.
Ted Cowan 1:09:56
Pivoting a bit, given the concerns about ozone production, is there an optimal UV wavelength for antimicrobial activity that doesn’t yield harmful airborne gasses?
Brett Cole 1:10:17
We’ve extensively researched UV in various settings. While traditional UV operates around 254 nm, there’s interest in the far-UV range, approximately 220 nm, which reportedly doesn’t generate ozone. However, regardless of the UV wavelength, it’s essential to ensure effective exposure to achieve the desired antimicrobial effect. Additionally, while technologies like UV can foster a sense of safety, it’s imperative to ensure they’re genuinely effective and don’t inadvertently introduce issues like ozone production or physical damage to other components.
Ted Cowan 1:12:03
Considering this, are there other technologies, especially newer ones, that can efficiently mitigate microbial threats without introducing potential side effects?
Brett Cole 1:12:49
Indeed, UV light technology has evolved. Traditional mercury-based globes were notorious for producing ozone. Later, Teflon coatings reduced this problem. Now, we also have UV LEDs. The challenge remains ensuring effective exposure without secondary exposure issues like ozone generation. The primary objective is to ensure we aren’t solving one problem while inadvertently introducing another.
Ted Cowan 1:14:19
Would anyone else like to share their thoughts on this?
Joshua Pitcher 1:14:23
When examining UV, it’s crucial to consider various factors. While its antimicrobial properties are well-known, there are challenges. For instance, retrofitting UV systems requires ensuring effective exposure times, especially in compact air conditioners. Newly designed systems can be tailored to allow for optimal UV exposure. Another concern is power consumption. Also, UV can damage non-metallic components, similar to how prolonged sunlight exposure damages plastics. Addressing all these challenges is crucial for effective retrofitting.
Zaheer Nasar 1:16:08
While much of our discussion has centered on retrofitting in-duct systems, there’s been growing interest in the UK to use established technologies like UV in more portable forms. Consider negative air ionization, a technology familiar in hospital operation theaters, where it might be implemented wall-based rather than as a part of the duct system. This opens up potential methods to integrate some of these technologies differently. Imagine an existing system that’s centrally controlled with an added layer of intervention on top. However, the evidence on the effectiveness of portable air treatment systems is debated. In controlled environments, they may work well, but real-world effectiveness can be questionable, especially for UV which relies on exposure and irradiance. We need to understand the flow rates and how much space the system can ventilate. With emerging low-cost infrastructure and initial capital investment to build these systems using new LED systems, there’s potential in this area. Some suggest combining antimicrobial methods with portable UV to see the combined impact of integrated interventions.
Brett Cole 1:18:19
I’ve worked on retrofitting high-level UV in buildings. Positioned up high, the UV light and fan system is separate from the built-in HVAC system. It circulates and irradiates the air before reintroducing it into the room. However, in places with high air change rates, like theaters and transport, the effectiveness may plateau. The question then arises: is there a need for them at all? But, emerging application technologies, such as high-level UV retrofits and portable air cleaners with HEPA filters, are promising based on recent research.
Zaheer Nasar 1:19:39
Ventilation design is crucial, especially for portable systems. With systems mounted on walls, displacement ventilation is needed. The design goal should be to lift potentially contaminated air above the breathing zone, giving it an additional cleaning boost before returning it. Each transportation system, even within the UK, has different ventilation systems, occupancy rates, and seating designs. But by leveraging our scientific understanding of airborne disease transmission and available solutions, we can confidently implement layered interventions. We need to ensure the public feels safe in these environments. Communicating evidence-based solutions to both the industry and the public is essential.
Ted Cowan 1:21:31
Zaheer, you raise an excellent point about building public confidence. Tying back to Brett’s comments about Maslow’s hierarchy, there’s a need for reliable studies to inform and assure the public. Are there any known published studies linking infection transmission to public transport?
Zaheer Nasar 1:22:52
Several studies have examined airborne disease transmission in public transport, primarily using TB as an archetypical airborne disease. But directly linking exposure to the development of disease is challenging. Often, mathematical models are used to estimate potential transmission. Some studies, based on TB transmission, have been conducted in ships and air cabins. But for COVID-19, I’m not aware of comprehensive meta-analyses comparing the safety of public transport to other environments like homes or offices. In the coming years, emerging studies might shed more light on this issue, especially with recent projects in the UK tracking infection rates in various venues.
Ted Cowan 1:26:22
Thank you, Zaheer. I’d like to pose another question to the group as we near the end of this session. With the future in mind and considering the plan for an event around biosurveillance, is there a role for pathogen detection technology to monitor airborne pathogens in public transport? If beneficial, what would the technology need to offer, and in which use-case scenarios could it be applied? If anyone has insights, please share. Brett, I’ll start with you since you’re at the top of my screen.
Brett Cole 1:27:24
Certainly, Ted. There are promising technologies available. Via aerosol detection, for instance, has been employed extensively in the pharmaceutical and healthcare sectors for years. Regardless of the technology, its validation is vital, ensuring it accurately measures and offers clear guidance on actions to take if high levels of bio aerosols are detected. Emerging IoT technology has potential in this area, provided it doesn’t cause unwarranted panic and supports the goal of fostering confidence in using public transport.
Ted Cowan 1:28:20
Thank you, Brett. Joshua, your thoughts on bio-detection?
Joshua Pitcher 1:28:35
Absolutely. Given that these technologies operate invisibly, the public must be informed of their efficacy. We face both a public safety issue and the challenge of earning public trust. People need to feel that these systems are working effectively. Measures such as monitoring and reporting can significantly boost public confidence.
Ted Cowan 1:29:15
Thank you, Joshua. Zaheer, your insights?
Zaheer Nasar 1:29:20
I’m quite interested in detection technology. There are bio aerosol detection systems initially developed for defense applications that have since transitioned to public health use. These systems can provide real-time information about the presence and concentration of bio aerosols in the air. There’s potential for systems that both alert to and treat airborne pathogens. Current detection systems are research-grade and bulky, making them suitable for larger installations like airports but less so for public transport. But emerging IoT technologies can monitor the environment for conditions conducive to airborne disease transmission.
Yair Hazi 1:31:48
I’m not particularly supportive of biological detection technology for transportation systems. My experiences in New York City have shown that background interference often skews readings. External factors, like a passing diesel truck or nearby food vendors, can compromise the readings. I haven’t seen any technology suited for deployment in environments like the New York City transportation system. Additionally, once you detect something, the subsequent actions aren’t always clear. Deploying such technologies in places like New York City requires stringent scrutiny and regulatory oversight.
Ted Cowan 1:33:09
That’s a valuable perspective, Yair, and underscores why we’ll dedicate an entire session to this subject. To all panelists, thank you for your insights and time. I look forward to our next session on this topic. Thank you to everyone who joined us today.
American Industrial Hygiene Association (AIHA)
AIHA is the association for scientists and professionals committed to preserving and ensuring occupational and environmental health and safety (OEHS) in the workplace and community. Founded in 1939, we support our members with our expertise, networks, comprehensive education programs, and other products and services that help them maintain the highest professional and competency standards. More than half of AIHA’s nearly 8,500 members are Certified Industrial Hygienists, and many hold other professional designations. AIHA serves as a resource for those employed across the public and private sectors and the communities in which they work.
Have a question about the event?
Connect with IBEC experts directly! Drop your queries below, and let's further the dialogue on preventing the spread of infectious diseases.