Germicidal Ultraviolet Light (GUV) and Disease Transmission Reduction

This report summarizes a Founders Pledge shallow investigation into germicidal ultraviolet (GUV) light as a public health and pandemic prevention intervention. The report provides an overview of different types of GUV and outlines crucial considerations for grantmakers and policymakers. Additionally, we suggest potential “impact multipliers,” or features of the world that can guide effective giving under uncertainty about the cost-effectiveness of different interventions. Note that this report is scoped to focus specifically on GUV; for a comparison of other indoor air quality interventions, we recommend the recent report Air Safety to Combat Global Catastrophic Biorisk.¹ Our report is a cross-worldview investigation — Rosie Bettle’s research usually focuses on current generations and global health interventions, while Christian Ruhl’s research usually focuses on global catastrophic risks. GUV could have benefits both for a near-term reduction in the global burden of disease and for the prevention and mitigation of future catastrophic pandemics.

UV light has long been used for its germicidal effects, for instance for water treatment.² A less well-known application of UV light, until recently, is for airborne disease transmission reduction; UV light (of the appropriate wavelengths) can inactivate pathogens, rendering them unable to replicate and cause infection. However, some wavelengths of UV light are damaging to skin and eyes—meaning that these UV sanitization systems need to either avoid direct contact with people, or must be of a sufficiently short wavelength such that the UV cannot penetrate the outer surface of people’s skin and eyes. We review different types of GUV systems and wavelengths to determine whether funding this space could be impactful. On installation types:

• Full-room UV systems, where light is shone throughout the room. Far-UVC full room systems take advantage of recent developments in our understanding of which wavelengths can be safely used in occupied settings to inactivate pathogens.
• Upper-room UV systems, which have been used for decades and rely on air flow in the room to circulate air upwards, where viral particles within the air are inactivated by the UV light.³
• In-duct UV systems, where the air is sanitized by UV light as it passes through an HVAC system, as well as portable GUV systems, which function similarly to in-duct systems.

On wavelengths:

• Conventional UVC of 254 nm light, which has a long history of (upper room) deployment, but is damaging to human eyes and skin.⁴
• “Far-UVC” between 200-235 nm, which has some advantages and a potentially high upside as well as remaining uncertainties around safety.

We find evidence that GUV is a potentially impactful intervention towards improving indoor air quality that could reduce the transmission of pathogens and consequent pandemic risk (including for bioengineered pathogens); one recent analysis suggested that outfitting US public buildings with these systems could reduce overall population transmission of respiratory viruses between 30% and 75% (N.B., more research is needed on real-world estimates of transmission reduction, as discussed below, and there are large uncertainties surrounding such estimates).⁵ In turn, air quality improvement appears to have been relatively neglected by mainstream funders such as government bodies and science funders, perhaps due to a historical belief that airborne transmission was not a key transmission route of respiratory disease.⁶ Hence, we believe this cause area is promising for effective philanthropy.⁷

We then compare the different GUV systems (full-room, upper room, and in-duct systems) and wavelengths (far-UVC and conventional GUV), focusing on safety and efficacy. We are optimistic about the potential of far-UVC technology and its large upside especially for extreme pandemic events, and find that existing evidence suggests that this technology may have advantages for a wide range of applications. Nonetheless, we believe that more safety studies are needed both to reduce real uncertainties (especially with regards to eye damage, long-term exposure effects, effects on vulnerable populations, and uncovering unknown risks) and to bolster public confidence. In addition, a key uncertainty of far-UVC technology is its potential to increase indoor air pollution—these externalities and the necessary measures to mitigate them may push against future cost-effectiveness of far-UVC technology. Moreover, although GUV technology is highly effective at reducing the amount of airborne pathogens, it remains unknown how well such reduction translates into disease transmission reduction, and how far-UVC differs from 254 nm GUV in different contexts (e.g. there are some theoretical reasons to believe that far-UVC may be especially useful for certain extreme events).⁸ We are therefore wary of over-hyping far-UVC technology over other indoor air quality interventions, especially existing GUV technology. Bearing in mind that existing GUV technology (such as 254 nm upper room systems) are already fairly effective, we argue that philanthropists should favor “wavelength-agnostic” advocacy rather than advocating for a specific UV system or wavelength—we don’t think the evidence for superiority of far-UVC is sufficiently strong as of late 2023 as to outweigh the risks of focusing specifically upon this technology, and potentially locking in inferior technology or turning the public against all GUV by rushing far-UVC deployment. Either way, we emphasize that — contrary to some public portrayals — GUV of any kind will not be a silver bullet for pandemics, but should be thought of as one potentially powerful tool in the health security toolbox, as part of a varied and layered defense.

We then identify specific impact multipliers within this space, with the aim of identifying promising funding opportunities. These include (1) leveraging societal resources via advocacy, since very large resources will be needed to roll out GUV technology (and we think it is possible that government funding bodies might move to produce more funding here), (2) focusing on high-income countries first, where there are already resources to potentially develop and use these technologies, (3) shaping research and design incentives (since there is a commercial interest here, we think it might be possible to promote private sector investment and therefore minimize the amount of philanthropic money needed), and (4) focusing on public perception over rapid deployment. With regards to the last point, we think there is a risk that (if GUV is rolled out poorly) public backlash might prevent the deployment of GUV for a very long time, perhaps when pandemic risk is higher than at present. With these impact multipliers in mind, we identify several potential funding opportunities; funding journalists to write about GUV (thereby potentially influencing fund managers and policy makers, and increasing public acceptance of GUV)⁹, funding public advocacy groups, shaping market incentives to promote private sector research, and directly funding safety and efficacy studies. Our top recommendation is advocacy to leverage societal funds for large-scale research programs on real-world GUV pathogen transmission reduction.

Overall, we think this is a promising area and recommend proceeding to investigate potential funding opportunities within this space.

Notes

1. Gavriel Kleinwaks et al., “Air Safety to Combat Global Catastrophic Biorisk” (1DaySooner and Rethink Priorities, 2023). ↩

2. “Catskill–Delaware Ultraviolet Water Treatment Facility, New York - Water Technology,” accessed August 29, 2023. ↩

3. In practice, many far-UVC systems may also be upper-room systems. Thanks to Vivian Belenky for this point. ↩

4. The 254 nm peak is for traditional low-pressure mercury lamps. This may shift as technology changes. Thanks to Jake Swett for this point in a round of external reviews. ↩

5. “… by using the complete described program of air quality interventions to address transmission in public spaces, overall transmission in the population can be reduced by 30-75%, with a median estimate of 52.5%.” Gavriel Kleinwaks et al., “Air Safety to Combat Global Catastrophic Biorisk” (1DaySooner and Rethink Priorities, 2023), 20. Note though that this estimate does not appear to count for the efficacy of existing indoor air quality measures; as far as we understand, this estimate measures ‘reduction in population transmission as a result of adoption of air quality measures in all public spaces, relative to having no indoor air quality measures in place’. ↩

6. Jose L. Jimenez et al., “What Were the Historical Reasons for the Resistance to Recognizing Airborne Transmission during the COVID-19 Pandemic?,” Indoor Air 32, no. 8 (2022): e13070. ↩

7. For more, see Chia C. Wang et al., “Airborne Transmission of Respiratory Viruses,” Science 373, no. 6558 (August 27, 2021): eabd9149. ↩

8. Max Görlitz writes, for example, “Crucially, we don't know how well this translates into an actual reduction in total number of infections. Of course, on priors, you would expect a reduction in the number of airborne pathogens to result in reduced infection risk. Yet the real world is messy and a lot could depend on air circulation in the specific environment, transmissibility of the pathogen, susceptibility of people etc.” Max Görlitz, “Thoughts on Far-UVC after Working in the Field for 8 Months,” Effective Altruism Forum, 2023. ↩

9. As discussed below, however, such work may be challenging to do well, and has several downside risks. See Leveraging Societal Resources via Advocacy for more. ↩