Isabel “Izzy” Medeiros, MS Student, Civil and Environmental Engineering, University of New Hampshire, [email protected]
James P. Malley Jr., Ph.D., Editor-in-Chief, UV Solutions and Professor of Civil and Environmental Engineering, University of New Hampshire, [email protected]
Owners and operators of UV technology are an important stakeholder group. These professionals have limited time and often prefer to remain anonymous when providing feedback. For this quarter, the Operator’s Corner is populated by feedback provided through direct contact with key transportation stakeholders that have experience in applying UV disinfection during COVID-19.
During the COVID-19 pandemic, there was a significant uptick in the use of UV disinfection on buses, trains and airplanes. The goal of this article is to track what has occurred in the two years following the COVID-19 pandemic.
Buses
Efforts by the US Department of Transportation-Federal Transit Administration (USDOT-FTA) included the often-cited “COVID-19 Research Demonstration Program: Efficacy of UV Lights in Transit Applications,” prepared by Rock Region Metropolitan Transit Authority. Quoting from the final project report (FTA Report Number 0259, September 2023), the study can be summarized as follows:
“To demonstrate the efficacy of UV light in disinfecting applications for COVID-19, Rock Region METRO (METRO) in Arkansas performed this research project under contract with Environmental Services Company (ESC) and the University of Arkansas for Medical Sciences (UAMS) in support of the Federal Transit Administration (FTA) Office of Research, Demonstration & Innovation. The tests were conducted with no passengers on board, after the vehicles were in service during normal operating hours. This project has one main objective. To assess the effectiveness of UV light systems in disinfecting the COVID-19 virus, the team will: a) Test the interior surfaces of transit buses for COVID-19 after the use of a chemical disinfectant and b) Test the interior surfaces of transit buses for COVID-19 after the use of UV disinfectant lights. A secondary objective is to compare the effectiveness of UV light systems to reduce bacteria (Escherichia coli and total coliform) on the same surfaces.
…Overall, this study provides limited preliminary data supporting the effectiveness of UV light for the decontamination of vans used for public transit. The results for E. coli are inconclusive – and the results for SARS-CoV-2 as well – as total coliform bacteria on seatbacks and wheelchair lift handles are equivocal. However, the results for total coliforms from the paired handrail samples indicate that UV exposure may have successfully reduced bacterial load. In addition, the doses of UV radiation recorded from each sampled van far exceed the doses needed to inactivate most coronaviruses and bacterial species. These results, taken together and interpreted within the context of prior literature documenting the germicidal effects of UV radiation, indicate that UV light may be as effective as, or more effective than, chemical fogging. Nevertheless, additional studies are recommended.”
The promising nature of this study led several metropolitan transit authorities to experiment with using UV disinfection on their buses, including NJ Transit, which produced the following findings (Report: NJT-RUCAIT-20-008, August 2020):
“This project was designed as a rapid effort to evaluate ultraviolet (UV) disinfection technologies with a specific emphasis on UV-C (ultraviolet germicidal wavelength) efficacy and practicality for surface disinfection of bus interiors. With more than 3,700 vehicles in NJ TRANSIT’s fleet, the deployment of any modern technology must be carefully weighed against alternatives to ensure it achieves the desired results. The study LiDAR surveyed six vehicle types and developed virtual environment 3D models for a NABI 40-ft bus and a mini-bus used for paratransit. Using the operational constraints, these models were used to run simulations to determine UV-C source placement. The model showed for the 40-ft bus that 65.61%, and for the mini-bus that 70.88%, of visible surfaces would receive a direct line of sight dosage. Field testing then was conducted using UV-C sources and a spectrometer. All but three (3) mini-buses and six (6) measured NABI locations received dosages more than the established threshold required to achieve a 10.6 mJ/cm2 kill dosage. However, even these locations still receive some level of irradiation. This confirmed the simulation results and implied that the true percentage of the bus receiving a kill dosage is much higher than the model prediction, which could not predict reflected light. However, any gap in coverage of a critical or high-touch surface, like a wheelchair seatbelt, raises overall efficacy concerns for UV-C disinfection of surfaces. Although UV-C for disinfection is highly effective, there are several pragmatic considerations, too. In comparison to chemical disinfection via spray and air-dry procedures, using a portable UV-C source does not appear to save labor time or cost. In comparison to the simplicity and speed of spraying an EPA List N-approved chemical disinfectant, the time and coordination of UV-C may not be practical for fleet-wide deployment. The research team also reviewed available literature concerning HVAC systems and their ability to remove virus particles from the air. If performance permits, the HVAC should be upgraded to MERV 13 or a better filter, or the highest compatible filter, at a minimum MERV 8. For in-duct ion and photocatalytic oxidation systems, the research team has health and efficacy concerns. Similarly, due to the rapid air exchanges within the bus HVAC system and the low UV-C exposure time of air in in-duct UV-C devices, it is unclear if they achieve the full kill dosage required. However, repeated in-duct UV-C exposure may result in a net cumulative dosage that weakens or kills some unknown percentage of virus.”
The authors of this article reached out to major metropolitan areas in the top 10 cities by population in the US: New York City, Los Angeles, Chicago, Houston, Phoenix, Philadelphia, San Antonio, San Diego, Dallas and San Jose. Contacts indicated that, during COVID-19, half of these cities piloted some form of UV technology in their buses. As of this writing, there are no systems on the buses that still are in operation. Some bus maintenance garages have retained UV disinfection lamps as part of their routine bus maintenance and cleaning protocols.
Trains
In May 2022, the NY Metropolitan Transportation Authority (MTA) entered a pilot project with Columbia University that used UV disinfection on MetroNorth and Long Island RailRoad commuter trains at their maintenance facilities using equipment provided by PURO Lighting of Lakewood, Colorado. The Uttar Pradesh (India) Metro Rail Corporation (UPMRC), a joint-venture company that operates the Lucknow Metro, Kanpur Metro and Agra Metro, followed the lead of MTA and installed UV disinfection as part of its maintenance protocol for trains operated by Lucknow Metro, which serves about 100,000 riders per day and has maintained that practice as of this writing. UV disinfection is provided using conventional LPHO systems provided by Vehant Technologies, India.
(Courtesy of NYC-MTA)
And, during and after the pandemic, work on using UV for trains continued aggressively in Italy. The group Light Progress developed a summary of its activities that showed the effectiveness of using UV for disinfection of trains and, in particular, adding UV disinfection to the HVAC systems of trains. This included the latest generation of trams operated by Azienda Trasporti Milanesi (ATM) for Milan, Italy. 1
Feedback on the current state of UV disinfection use on trains for the top 10 US cities found similar results to those for the buses in that current use on trains is not common. However, some maintenance facilities have maintained UV disinfection as part of their maintenance garage protocols, and others indicated new generations of subway cars and trains cars are being reviewed for purchase that offer options for having UV disinfection systems incorporated into their HVAC systems.
Airplanes
During the COVID-19 pandemic, the UV sector was updated routinely about the state of airplane disinfection robots provided by companies such as Honeywell Aerospace’s UV Cabin System (formerly Dimer GermFalcon) and Collins Aerospace’s licensing and use of the Boeing Lilac-UV system. A follow-up of those early 2020 practices was performed for this article by contacting the International Air Transportation Association (IATA).
IATA indicated about 50% of its members include UV disinfection as part of the deep-cleaning protocols for aircraft. These protocols normally are conducted every 30 to 45 days during routine downtime (often at night). IATA also indicated that some of its members have reported a continued preference for HEPA filters for onboard air system purification and have not adopted UV disinfection advances for air purification or bathroom maintenance on aircrafts when occupied by passengers.
This article found almost universal agreement among managers of all modes of transportation that concern over inadvertent passenger exposure to UV wavelengths remains the primary concern and strongly influences how they use UV disinfection in their systems. No examples could be found of UV disinfection being practiced in any of these modes of transportation when passengers are present in the vehicle.
References
