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Air Safety to Combat Global
Catastrophic Biorisk
Gavriel Kleinwaks, Alastair Fraser-Urquhart,
Jam Kraprayoon, Josh Morrison
Contents
Executive Summary..........................................................................................................................................2
Top-line summary..............................................................................................................................................................2
The problem: airborne pathogens...................................................................................................................................2
How to fix indoor air contamination..............................................................................................................................2
How can we accelerate the deployment of IAQ-related interventions?...................................................................3
Background.......................................................................................................................................................4
What is the Problem?........................................................................................................................................6
Pandemic respiratory disease...........................................................................................................................................6
How important is risk from respiratory pathogens?....................................................................................................7
Respiratory pathogens........................................................................................................................................7
Limitations.........................................................................................................................................................................9
Mechanical Interventions to Improve Air Quality...........................................................................................10
Summary of options.......................................................................................................................................................10
Ventilationandfiltration....................................................................................................................................10
Germicidal ultraviolet (GUV) light.................................................................................................................11
Cost and cost-effectiveness of different mechanical interventions.........................................................................13
Modeling the efficacy of interventions.........................................................................................................................17
Room-scale models...........................................................................................................................................17
City-scale models...............................................................................................................................................18
Integration of room- and city-scale models..................................................................................................18
How could models be improved?....................................................................................................................19
Rough Estimate of Impact..............................................................................................................................19
Bottlenecks and Funding Opportunities.........................................................................................................22
What are the bottlenecks?..............................................................................................................................................22
What can new funding accomplish?..............................................................................................................................22
Advocacy.............................................................................................................................................................23
Cost and manufacturing...................................................................................................................................24
Research..............................................................................................................................................................24
Coordination......................................................................................................................................................25
Possibilities for immediate action..................................................................................................................................26
Risk Factors.....................................................................................................................................................26
Appendices......................................................................................................................................................28
Acknowledgements.........................................................................................................................................................28
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Executive Summary
Top-line summary
• Most efforts to address indoor air quality (IAQ) do
not address airborne pathogen levels, and creating
indoor air quality standards that include airborne
pathogen levels could meaningfully reduce global
catastrophic biorisk from pandemics.
• We estimate that an ideal adoption of indoor air
quality interventions, like ventilation, filtration, and
ultraviolet germicidal irradiation (GUV) in all public
buildings in the US, would reduce overall population
transmission of respiratory illnesses by 30-75%, with
a median estimate of 52.5%.
• Bottlenecks inhibiting the mass deployment of these
technologies include a lack of clear standards, cost
of implementation, and difficulty changing regula- tion/public attitudes.
• The following actions can accelerate deployment and
improve IAQ to reduce biorisk:
• Funders can support advocacy efforts, initiatives
to reduce cost and manufacturing issues, and
research with contributions ranging from $25,000-
$200M. Applied research projects can be funded
to show the efficacy of ventilation, filtration, and
GUV in field applications.
• Businesses and nonprofits can become early
adopters of GUV technology by installing it in
their offices and allowing effectiveness data to be
collected.
• Researchers can develop models that better
tie built-environment interventions to popula- tion-level effects, conduct further GUV safety
testing, and do fundamental materials and manu- facturing research for GUV interventions. Ap- plied research can be conducted on ventilation,
filtration, and GUV applications in real settings.
The problem: airborne pathogens
Infectious diseases pose a global catastrophic risk. The
risk is especially severe, and we are far less prepared,
if it involves bioengineered pathogens. Out of the
various methods of pathogen transmission, airborne
1 Air quality standards are typically set in terms of air changes per hour (ACH) and equivalent air changes per hour (eACH).
pathogens, particularly viruses, are especially danger- ous, as they are easy to spread and difficult to com- bat. Airborne pathogens are significantly more likely
to spread indoors than outdoors, so reducing indoor
respiratory pathogen transmission could substantially
reduce global catastrophic biorisk by:
• Reducing the probability that a disease has an effec- tive reproduction number >1 and will spread at all,
or if not,
• Limiting the number of infections that occur, “flat- tening the curve” so as not to overwhelm medical
systems.
• Slowing the spread of disease to
• Provide more time for countermeasure develop- ment, and
• Discuss and implement non-pharmaceutical
interventions, like limiting large gatherings and
requiring masks.
Current indoor air standards do not consider infectious
disease risk, whereas waterborne and foodborne patho- gen deaths have been largely eliminated in many areas
due to improved water and food sanitation. Indoor
air quality, especially concerning infectious diseases,
should be a priority public good, like fire safety, food
safety, and potable water.
How to fix indoor air contamination
Known effective interventions to reduce indoor air
pathogen contamination include increased outdoor air
ventilation, high-efficiency particulate air (HEPA) filter- ing, and germicidal ultraviolet (GUV) light. Of these,
GUV technology is the most promising for pathogen
control because it can reach considerably higher levels
of equivalent air changes per hour (eACH) than filtra- tion or ventilation by directly inactivating pathogens,
could in principle be more energy efficient, is straight- forward to install as a retrofit, and produces no noise
pollution.1 Filtration is a viable option for high levels
of eACH up to CDC hospital standards (8-12 eACH),
where it is still relatively cost-effective. It also helps
to reduce particulate and chemical pollution, which is
relevant for immediate health concerns, such as chronic
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respiratory health and everyday cognitive functioning.
By contrast, high-volume ventilation is expensive, or
even impossible in many buildings due to the difficulty
of retrofitting or upgrading HVAC systems.
Currently, two different wavelengths of GUV are
utilized: 254 nm UVC and 222 nm UVC, also known
as far-UVC. People should not be directly exposed to
254 nm UVC, since it can cause skin and eye damage,
but 222 nm UVC is likely safe for direct interaction.
Most current germicidal light fixtures are 254 nm, and
therefore installed as an upper-room or in-duct system,
shielded from room occupants.
• 254 nm UVC is already more cost-effective than
other IAQ interventions and, if installed correctly, is
safe due to lack of interaction with a room’s occu- pants.
• Far-UVC can be used to reduce surface and close
contact transmission as well as airborne transmis- sion, making it potentially the most effective inter- vention for reducing global catastrophic biorisk, with
a recent review indicating strong safety evidence in
humans even after prolonged exposure. The price
of current systems is currently too high for at-scale
deployment, though there are reasons to think the
price can be lowered significantly.
We estimate that the ideal mass deployment of indoor
air quality interventions, like ventilation, filtration, and
GUV, would reduce overall population transmission of
respiratory illnesses by 30-75%, with a median esti- mate of 52.5%. (Described in the “Rough Estimate of
Impact” section.) This could completely prevent many
current diseases from spreading, and even for the most
transmissible diseases, like measles, it likely amounts
to a great reduction in transmission speed, and would
serve as an important layer of biodefense.
Overall, we can be confident that these interventions
effectively reduce pathogen load in the air, and some
previous work has been done investigating the impact
of ventilation on population-level transmission.
How can we accelerate the deployment
of IAQ-related interventions?
Despite the existence of promising technologies, sever- al bottlenecks are preventing the mass deployment of
IAQ interventions. Some significant ones include:
• Expense of improving and implementing air clean- ing technology.
• Difficulty of wide-scale change in regulations and
public attitudes towards indoor air quality.
• Difficulty in understanding the relationship between
pathogen load and infection cases.
However, significant opportunities exist to accelerate
deployment via advocacy, cost and manufacturing im- provements, and research.
• Advocacy: Some presently attractive advocacy proj- ects include: development of an anti-infection stan- dard by the American Society of Heating, Refriger- ating and Air-Conditioning Engineers (ASHRAE);
promoting use of the recently released (Non-infec- tious Air Delivery Rate) NADR standard from the
Lancet COVID Commission; recruiting high-status
businesses as early adopters who can conduct and
fund pilots; improving air quality in schools through
private and public investments; and creating an um- brella group to coordinate efforts.
• Costs and manufacturing: Advanced market com- mitments and other forms of investment could drive
down the cost of far-UVC solid-state emitters and
other interventions. Investments in training could
also increase expertise in design and installation of
GUV systems.
• Research: Attractive research opportunities include:
(a) further establishing the long-term safety of far- UVC, which can help with international deployment,
(b) creating reliable ways to test intervention efficacy,
which could include applied research programs or
controlled natural exposure challenge studies, (c)
developing guides to help organizations optimally
deploy IAQ fixtures, and (d) social research to im- prove public advocacy efforts around IAQ.
We provide a conservative estimate that the total cost
of upgrading air quality systems in all public buildings
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in the US to be $120-$420 billion (CI:90%).
We give a conservative estimate that reducing the risk
of a future pandemic as bad as COVID by 1% would
be worth $100 billion, and it seems highly likely that
this program would reduce the risk or severity of a
pandemic by more than 1%.
We think significant action to accelerate deployment
of IAQ interventions to reduce biorisk would benefit
from philanthropic funding in the range of $25,000-
200M:
• $25,000 could fund the development of a detailed
population transmission model or message-testing
surveys for IAQ public advocacy.
• $5M could fund the development of new solid-state
far-UVC light sources.
• $20M could fund a single dedicated clinical project
(e.g. something like EMIT-2) or a field demonstra- tion of GUV efficacy in reducing transmission in
high risk areas.
• $200M could fund a program combining studies to
ascertain and demonstrate the effect of indoor air
interventions with advocacy to lead to broad adop- tion (e.g. far-UVC light safety studies, real-world
efficacy studies for IAQ interventions, advocacy for
improved pandemic preparedness standards, etc.).
Background
Poor indoor air quality adversely impacts health, yet has
historically been ignored compared with other health
interventions (such as surface cleaning, handwashing,
or spray barriers). However, COVID-19 has created a
significant change in scientific attitudes towards aerosol
transmission of respiratory disease, and the harmful
impact of chemical and particulate indoor air pollution
continues to be documented in greater and greater de- tail. In this brief investigation-style report, we explore
the case for funders, founders, researchers, and existing
organizations to reduce respiratory pathogen burden
2 E.g. implementing GUV in countries where TB is endemic, we could expect to see reduction in TB transmission as a near-term benefit,
regardless of the timing of a respiratory pandemic.
3 8 out of 10 top airports for passenger traffic are in the US.
and global catastrophic biorisk (GCBR) by improving
indoor air quality. While there would be benefits to
implementation in other countries, we focus on the
United States for a few reasons2
:
1. American standards tend to influence other coun- tries (e.g. car emissions standards).
2. Globally, 1.2 billion people live in high-income
countries, for which deployment should be roughly
similar to the US.
3. We expect building changes to be implemented first
in richer countries because of their greater resources
and institutional capacity.
4. People in high-income countries fly more often on
average, so blocking or reducing pathogen transmis- sion in these countries, including the US, would do
more to reduce air travel spread.3
5. Technological investments by wealthy countries will
reduce costs, which would facilitate later deployment
in developing countries.
In addition, focusing on the US allows us to provide
a more detailed cost-benefit analysis, as the US is
well-studied and has data on important items such as
the composition of building stock.
Existing IAQ Policy and Regulation: The majority
of air quality guidance is aimed at chemical pollutants,
with little if any focus on infectious disease.
• World Health Organization: The WHO Guide- lines for Indoor Air Quality exclusively references
dangerous chemicals and gasses such as benzene,
carbon monoxide, and formaldehyde.
• State and Local Government: In the United
States, IAQ standards are typically set by individual
states and refer only to ventilation, not pollutants or
pathogens. These policies tend to derive from guide- lines published by the American Society of Heat- ing, Refrigerating, and Air-Conditioning Engineers
(ASHRAE), an influential industry group, or they are
omitted from building codes entirely.
• ASHRAE: The majority of buildings fall under the
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remit of ASHRAE Standards 62.1 and 62.2, last
updated in 2022. They call for varying amounts of
ventilation based on occupancy, use, and a constant
for area - working out to be approximately 1-2 ACH
in residences and offices (though half of studied
buildings fall below ASHRAE standards). The
current standards do not consider airborne patho- gens, though they are currently being updated to do
so. More stringent requirements can be found for
healthcare settings, defined in ASHRAE 170.
• Occupational Safety and Health Administration:
OSHA has authority to regulate air in indoor work- place settings. Its regulations tend to be fairly weak,
only address particulate and chemical pollutants, and
are primarily based upon ASHRAE guidelines. They
only apply to a healthy working adult population
and should not be considered for the general public,
which includes children and the elderly. In facilities
that are not expected to produce large amounts of
pollutants, OSHA demands only a self-certification
form, and in environments where pollutants might
be more common, only some chemicals are regu- lated, with a generic requirement for employers to
protect against known harms.
• Environmental Protection Agency: The EPA
is responsible for outdoor air quality but does not
regulate indoor air quality; it primarily focuses on
greenhouse gasses, radiation, and common hazard- ous gaseous and particulate pollutants. However,
it does provide resources for people seeking to
independently improve their indoor air quality. The
National Ambient Air Quality Standards (NAAQS)
are health-based, and as such should be applicable to
those air pollutants for which there is a standard in
all environments.
• CDC: The CDC is responsible for guidance related
to infectious disease, but is not a regulatory agency.
Its suggestions are very high-level and do not ad- dress businesses or standards.
• Lancet COVID-19 Commission: The Lancet
Commission recently released its recommendations
for Non-Infectious Air Delivery Rates (NADR),
benchmarks for ensuring good indoor air quality
that are intended for universal application. Based on
a review of existing literature, the report proposes
potential target measures for NADR for reducing
transmission of airborne pathogens, such as volu- metric flow rate per person, per floor area, or per
volume. For NADR measured by volumetric flow
rate per volume, the report proposes that a “good”
target for volumetric flow rate per volume is 4 air
changes per hour equivalents (ACHe), with increas- ing benefits in transmission reduction continuing to
at least 6 ACHe.
Prior to COVID-19, the dominant public health
paradigm treated airborne transmission as negligible
for most major respiratory diseases. This resulted in
a historical reluctance to implement air hygiene con- trols. However, interdisciplinary research inspired by
the COVID-19 pandemic has shown that airborne
transmission is a major mode of transmission for this
disease, and likely a significant one for many other
respiratory infectious diseases.
Federal efforts have been proposed to improve US in- door air quality: the American Pandemic Preparedness
Plan (AP3) proposed allocating $3.1B for “next-gen
PPE and built environment improvements” (with no
indication of the split between the two), and requested
that the 2023 budget include $88.2 billion in mandatory
funding for biodefense purposes, but neither was en- acted. Despite these setbacks, the Biden administration
released a plan to advance indoor air quality nationwide
by upgrading the filtration and ventilation of federally
owned buildings, funding air quality research and iden- tifying gaps, and providing resources and incentives for
upgrades in schools and residential buildings. Addition- ally, organizations that want to upgrade their ventilation
and air cleaning systems are encouraged to use funds
from the American Rescue Plan and Bipartisan Infra- structure Law to do so.
In this report, we use two primary metrics for air
quality: air changes per hour (ACH), referring to the
outdoor air supply airflow rate normalized by room
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The majority of aerosolized respiratory pathogen
transmission occurs indoors; in the COVID-19 pan- demic it is estimated that likely more than 90% of
transmission has occurred indoors, that the odds of
transmission are at least 20 times higher indoors than
outdoors, and superspreading events happened indoors
in locations with inadequate ventilation.
Given the above, improving indoor air quality, i.e. re- ducing indoor respiratory pathogen transmission, could
substantially reduce global catastrophic biorisk by:
1. Reducing the probability that a disease has an effec- tive reproduction number >1 and will spread at all,
or if not,
2. Limiting the number of infections that occur, “flat- tening the curve” so as not to overwhelm medical
systems
3. Slowing the spread of disease to
• Provide more time for countermeasure develop- ment, and
• Discuss and implement policies, like limiting large
gatherings and requiring masks.
Ideally, improving indoor air quality is only a part of
a portfolio for reducing global catastrophic biorisk,
alongside other interventions like advanced PPE, vac- cinations and medications, improving early pandemic
detection, and advocacy to better manage dual-use
research of concern.
How important is risk from respiratory
pathogens?
We estimate that 90-99% of COVID-19 infections
come from aerosol sources, between 40-80% of influ- enza transmission, and much6 of the overall disease
burden of other common cold viruses. The relative
importance of modes of transmission between patho- gens is very poorly quantified. For most common re- spiratory pathogens (aside from COVID-19 and to an
extent, influenza) the data required to make meaningful
quantitative predictions does not currently exist.
6 Our research indicates numbers between 20% and 90% of disease burden; figures depend highly on the specific models and scenarios
in which infections take place. Generally, substantial evidence underlies the hypothesis that all respiratory infections can be transmitted via
aerosol to some degree or another.
IAQ interventions to prevent disease primarily act on
aerosolized particles. The impact of IAQ on disease
transmission is dependent on the fraction of pathogen
transmission attributable to airborne transmission.
While some diseases, most notably COVID-19, TB,
measles, and chickenpox, are widely accepted to be
dominantly airborne, most respiratory pathogens have
historically been assumed to be primarily driven by
large droplet/fomite transmission. This assumption
now seems highly uncertain given updated research
avenues.
Respiratory pathogens
COVID-19: The vast majority of COVID-19 infection
is transmitted via aerosols, primarily indoors. Early
studies were mostly observational, with notable early
studies showing a clear case of aerosol transmission
in a restaurant and at a choir practice. Aerosol trans- mission proved so efficient that COVID was even
transmitted between individuals in rooms across the
hall from each other in a quarantine facility when their
doors were simultaneously open for under a minute.
Measles: Measles is the most contagious known
airborne pathogen, making it an important bench- mark for air safety measures. Although vaccination
is the preferred public health measure to prevent the
spread of measles, vaccine hesitancy has contributed
to recent outbreaks in some communities, indicating
the need for alternative interventions. In 2019, a series
of measles outbreaks led to 1,274 reported cases in
the US. As has long been recognized, measles is easily
transmitted through aerosols, contributing to its high
contagiousness. Case studies of superspreader events
suggest rapid measles recirculation throughout build- ings by unfiltered central ventilation systems, with one
case study indicating 35-78% of infections occurring
without close contact with the initial case. The impact
of GUV on preventing measles transmission has also
been long-studied, with scientific literature dating to
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the 1940s. A landmark UVGI study found strong pos- itive effects of upper-room irradiation in preventing
transmission in classrooms, but later studies indicated
much weaker effects in experimental setups where sub- jects also congregated in other settings, such as on the
schoolbus to and from school, indicating the need for
comprehensive treatment of all sites of congregation.
Influenza: Over the last decades, large amounts of re- search have been conducted on influenza transmission,
but consensus is far from clear. Literature reviews pro- vide convincing evidence of both closer-range/fomite
transmission, and transmission via aerosols (though not
without divergent opinions). Computational models
can also predict dominant aerosol transmission of
influenza.
Various real-world interventions and controlled studies
have been completed:
• Deployment of upper-room GUV in a hospital
during a 1957 influenza outbreak almost completely
prevented transmission, suggesting the vast majority
of transmission is airborne.
• Studies in Bangkok and Hong Kong estimated (albe- it speculatively) 41-52% of transmission in control
arms was via the aerosol route, due to increased
symptoms potentially consistent with airborne infec- tion in the intervention households.
• A recent study attempted to cause flu transmission
from deliberately infected research participants, but
(in contrast to an earlier pilot study) very few infec- tions occurred, meaning no firm conclusions were
drawn. A US-based followup, launched this year,
hopes to improve on this design by using donors
with community-acquired infections (removing the
possibility of an experimental infection affecting
shedding characteristics).
There exists highly convincing evidence of all major
transmission routes for influenza. However, it seems
reasonable to take as a lower bound 40% airborne
transmission (the lowest value in the Bangkok/Hong
Kong intervention study), and an upper bound of 80%
(based on the success of the Livermore hospital study).
Tuberculosis: TB stands out for having a potentially
indefinite incubation period. Only 5-10% of people
infected with the bacteria ever develop symptoms,
so many carry the disease for long periods without
knowing. TB is transmitted through the air by aerosol
droplets from people with active symptoms, and may
even be transmitted by some asymptomatic carriers.
Killingley, B. (2012) Investigations into Human Influenza Transmission. [Unpublished PhD thesis]
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not include the costs of post-upgrade energy con- sumption or increased operation and maintenance. If
upgrades are done primarily through ventilation, there
is substantial added energy consumption, estimated
by one expert at a 15-20% overall energy cost increase
for 10 eACH11 throughout a school, especially if the
upgrade does not explicitly target energy efficiency
through mechanisms like installing energy recovery
ventilators.
In order to estimate the cost of upgrading the general
stock of public buildings in the US, we start from a
published estimate that educational space uses 14% of
commercial floorspace in the US, and estimate that it is
between 10-20% of commercial floorspace (CI:90%).
We’ll additionally estimate that public K-12 buildings
are 30%-70% of educational floorspace (CI:90%).
Using this and a cost-estimate drawn from the earli- er CHS report on school ventilation, we estimate the
total cost of upgrading air quality systems in all the
commercial buildings in the US to be $120-$420 billion
(CI:90%).
This figure is prohibitively expensive for rapid imple- mentation. However, it assumes the cost of upgrading
systems stays fixed, but given that this field is getting
increased attention and investment, costs might come
down considerably over the next decade. For example,
we use the $15 billion estimate for upgrading school
HVAC systems. However, if air quality improvements
included GUV to achieve target standards, rather than
relying on HVAC alone, the cost could be significantly
lower due to the higher cost-effectiveness of GUV.
Also, more targeted programs addressing high-priority
public spaces as an intermediate step would be less
expensive and still reduce pandemic risk and improve
everyday health. For example, building on the estimate
of $15 billion to upgrade public primary education
facilities, we can produce the following upgrade cost
11 Although the expert provided the energy cost estimate for 10 eACH, it is uncommon for buildings to have the HVAC capacity to
achieve over 6 eACH through ventilation alone, as stated below in Table 1.
12 Order-of-magnitude check: In the US, about 1 million people have died of COVID. Government agencies typically use $1-10 million
for the value of a statistical life, i.e., how much should be spent to save a life. These figures would place the cost of COVID at $1-10 tril- lion in life loss alone, so hypothetically the US government should be willing to spend up to $10 trillion to fully avert another COVID-size
pandemic.
estimates using the percentage breakdown of commer- cial building stock:
• Healthcare facilities and hospitals, 4.7% of commer- cial floorspace: $10 billion
• Food service, 2.1% of commercial floorspace: $4
billion
• Public assembly space, 6.4% of commercial floor- space: $14 billion
• Malls, 6.8% of commercial floorspace: $15 billion
• Offices, 18.3% of commercial floorspace: $39 billion
• Religious institutions, 5.2% of commercial floor- space: $11 billion
If upgrades to public buildings were to be implement- ed across a decade in the US, ~$20 billion a year would
be spent on a complete air quality upgrade program.
For comparison, in 2021 alone, the US Department of
Defense spent $10 billion on facilities maintenance and
construction and $141 billion on weapons and systems
procurement. We use the comparison with defense
spending because biosecurity is an important com- ponent of national security and these figures demon- strate what people are willing to spend on defense, not
because we would expect government spending to fully
fund this program.
Researchers from the Institute for Progress and the
Johns Hopkins Center for Health Security demonstrate
that the COVID pandemic cost the US at least $10 tril- lion in combined economic and health losses.12 Using
their lower-bound numbers and lenient assumptions
for a future pandemic (half as destructive as COVID),
they estimate that it would be worth $50 billion to
reduce the risk of a future pandemic by 1%. Naturally,
given the optimism of these assumptions, pandemic
reduction efforts are potentially worth much more.
Based on this CHS report, we estimate that reducing
the risk of a future pandemic that is as bad as COVID
by 1% would be worth $100 billion, and it seems highly
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number may be reduced in a given population over the
month due to behavioral changes. To provide a very
rough sense of a changing epidemic, the second exam- ple (labeled “Varying R”) uses R0 until day 14, at which
point we replace R0 in the model with Rt = 1⁄2 R0
. The
code used to generate these plots can be seen here.
This transmission sketch is extremely rough on many
counts, and illustrates the need for greatly improved
models connecting building improvements with pop- ulation transmission. The elements that especially
contribute to the inaccuracy:
• As described in the introductory paragraphs, the
31 Self-correcting refers to situations like during the COVID-19 pandemic, when people appeared to dynamically adjust their behavior
based on apparent COVID-19 prevalence.
factors that went into the table had to be roughly
estimated from proxies.
• We cannot expect ideal adoption of mitigation mea- sures.
• Other pandemic-capable respiratory viruses might
have dramatically different dynamics from SARS- CoV-2.
• Further technological development of interventions
could reduce transmission even further.
• We assume there is no self-correcting behavior in
the population as a result of IAQ interventions.31
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We prioritize this program not because of obvious cost
favorability,32 but because of its capacity to address
superspreader events and international spread (e.g., by
greatly reducing transmission in airports), and because
it is a program of “passive” interventions, which do
not rely on individuals’ actions to achieve the majority
of the gains. (Contrast this with the “active” inter- ventions described in Kevin Esvelt’s “Delay, Detect,
Defend” Geneva Paper, such as equipment, resilient
production, and diagnostics.) Comprehensive pandem- ic defense programs should “stack” interventions for
dramatic reduction in transmission. The most trans- missible pathogen we know of is measles, which is
estimated to have an R0 of around 20, so an ambitious
pandemic prevention program might aim to reduce
pathogen transmission by 98%, bringing R0 of measles
to 0.4. This target would prevent a pandemic of any
measles-like or even significantly more transmissible
pathogen.
Overall, we can be confident that these interventions
effectively reduce pathogen load in the air, but we can- not precisely estimate their impact on population-lev- el transmission without a more robust and detailed
model.
Bottlenecks and Funding Oppor- tunities
What are the bottlenecks?
1. Highly general, imperfect metrics: Existing air
quality metrics, such as those set by ASHRAE, are
not ideal targets for air quality interventions with the
goal of reduced infection. Targets should be found- ed on both pathogen load in a room and pathogen
load that an individual receives. The Lancet Commi- sion’s NADR may be a good metric to implement
widely.
2. Difficulty in understanding the relationship
between pathogen load and infection cases: The
relationship between inhaled pathogen load and
infection cases is unclear in general, and will be dif- ferent for different pathogens. Even given better es- 32 We have not done a cost comparison with other programs.
timates of pathogen load through a detailed model,
the research necessary to experimentally determine
the relationship between air quality and infection
rates will be complex and costly.
3. Expense of existing air cleaning systems: Install- ing GUV lights and more portable air cleaners in
rooms is expensive on a per-unit basis, and upgrad- ing ventilation systems by increasing filtration capac- ity and/or outdoor air supply involves not only up- front expense, but the additional increase in energy
costs over the lifetime of a building. Retrofits must
be made with energy efficiency in mind. In many
cases, the party responsible for such upgrades/in- stallations may not be the party to benefit from the
upgrades, or may consider the benefits uncertain.
4. Expense of improving air cleaning technology:
Improving air cleaning technology will require large
investments, particularly when considering that the
far-UVC systems needed to eliminate pathogens at a
conversational distance requires both technological
development and safety/efficacy testing. Invest- ments in both certification and testing of systems is
needed so that consumers know that they are getting
a quality product when purchasing.
5. Difficulty of wide-scale change: Wide-scale
improvements in air quality may require changes
to building codes, similar to improvements in fire
safety. Policy change can be enormously slow, and
building codes are typically the purview of individ- ual municipalities or counties, which would frag- ment a push for any policy beyond the adoption of
ASHRAE standards. Alternatively, there could be a
campaign for voluntary corporate adoption, which
would require expensive indoor air quality improve- ments to carry a significant positive reputation.
6. Public distrust of UV light: People may primar- ily associate UV light with cancer risk, and it may
be difficult to communicate technical safety details,
such as the safety of upper-room installations or the
difference between bands in the UV spectrum.
7. Public acceptance and excitement about clean
indoor air: Greater public awareness, understand- ing, and support for indoor air quality among
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• Tax subsidies: Governments could subsidize
installation of basic, known effective interventions
in schools, offices, restaurants, and other congregate
settings. (Addresses bottlenecks 3, 5, and 6.)
• Inspections and data collection on IAQ: Estab- lishments are already subject to regular health and
safety inspections, so it could be mandated that
inspectors carry a suite of indoor air quality moni- tors that measure key air pollutants such as PM2.5,
TVOC, CO, NO2
, and carbon dioxide will generate
baseline data that serves as a proxy measure for
eACH and improved indoor air quality. (Addresses
bottleneck 5.)
• Establishing an umbrella organization for IAQ
coordination: If effective leadership can be found,
it could be useful to develop a central organization
to manage the IAQ projects above, funnel funding
to projects, publish analyses of projects’ effective- ness, and oversee research and market-shaping activ- ities. (Could address all bottlenecks.)
Cost and manufacturing
Two of the key bottlenecks to the mass deployment of
IAQ interventions are the costs of existing air cleaning
systems and the costs associated with improving air
cleaning technology. There are funding opportunities
and mechanisms that could address these bottlenecks.
Given the current high relative cost of far-UVC lamps,
funding could be targeted at developing solid-state
far-UVC emitters to replace KrCl lamps (currently ex- pensive and produced by only a few manufacturers33).
As described above, frequency-doubling blue lasers on
monolithic chips is one such promising approach that
could significantly reduce the cost and increase the
efficiency and reliability of far-UVC emitters relative
to KrCl lamps. If prototypes are successful, it will be
possible to rapidly scale up manufacturing to produce
a high volume of these chips, as they are based on
common materials used for existing ubiquitous white
LEDs. In the case of 254 nm fixtures, there are also
high-power UVC-LEDs that have been recently devel- oped that use relatively little energy to operate and have
33 Some known manufacturers include: Ushio, Eden Park Illumination, and Sterilray. Ushio is the current leader in terms of lamp effica- cy/lifetime/filter quality, and was on the scene earliest.
a long operational lifespan. These may benefit from ad- ditional investment to reduce the costs of at-scale pro- duction. There could be research subsidies and prizes
for fundamental materials and manufacturing research.
At later stages of technological readiness, an advanced
market commitment (AMC), funded by government,
philanthropy, or business, could spur development of a
product by committing to a purchase once technology
meets certain specifications. AMCs already have a track
record, including examples such as Operation Warp
Speed, which incentivized COVID vaccine develop- ment and acquired COVID vaccines in the US.
As of right now, it is possible to create far-UVC LEDs,
but their efficiency is very low and it is unclear whether
they can be manufactured in a reliable and cost-ef- fective way. The blue LED was only developed in the
1990s and was considered a major breakthrough at the
time; even lower-wavelength LEDs are likely to require
the development of new semiconductors and new
manufacturing methods. However, if far-UVC LED
manufacturing can be made reliable at a high quality, it
will be possible to meet mass demand. Another option
for supporting this LED development is direct invest- ment or funding for fundamental materials and man- ufacturing research. Such funding could take the form
of, for example, support for PhD students or other
researchers working in the field, which is well within
the normal activities of several philanthropic or gov- ernmental organizations.
There may also be relatively expensive products in the
filtration and ventilation space, where costs could be
reduced, particularly by increasing the energy efficien- cy associated with HVAC systems. Expanding the use
of energy recovery ventilators (ERVS), which allow
exhausted cooling or heating energy to be recovered,
should reduce the cost of climate control.
Research
There are opportunities to conduct both life sciences
and social research to address the bottlenecks men-
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tioned earlier.
Far-UVC safety testing: Far-UVC is a potentially
transformative intervention, and studies to develop a
safety record sufficient for wide use in humans should
be a high priority. Studies have already been successful- ly conducted on realistic 3D skin models, with intense
monitoring for damage, and some longer-term studies
on mice made deliberately susceptible to tumors. Inter- ventions of a similar risk have been proposed based on
the evidence of models. In-human longer-term studies
could be feasible on a dedicated population (possibly
an office block), with monitoring for early signs of
damage, combined with an early efficacy study.
Valid efficacy models: Creating a way to experimen- tally test the efficacy of various IAQ interventions will
be a necessary component of engendering and opti- mizing implementation over the long-term. One model
for doing so is the idea described above of randomiz- ing experimental pilots in early adopters.
CNE studies: Another approach is to utilize con- trolled natural exposure (CNE) studies, which are a
version of human challenge studies where uninfected
“recipient” volunteers are exposed to infected “donor”
volunteers. Despite their ability to provide some of the
highest-quality, cleanest quantitative data of aerosols,
transmission routes, and interventions, they are uncom- mon, with only two large-scale studies in the last two
decades - one in 2010, finishing with an attack rate too
low to be of use and one additional study planned over
the next five years.
We think that exploration of CNE studies stands to be
a valuable research contribution requiring a high level
of cooperation between fields. That said, these studies
are still in their infancy; using them to experimentally
test intervention efficacy may require significant invest- ment on the order of tens of millions of dollars.
Implementation research: There are fundable oppor- tunities around improving the implementation of IAQ
interventions such as the development of guidelines
for setting up IAQ systems to optimize performance
and address safety concerns. Another set of projects
could be centered around developing industry stan- dards for testing products and reporting output values
(e.g. Watts) for fixtures.
Public advocacy-related research: There are a range
of research projects that could inform public advoca- cy around indoor air quality as a visible, salient cause.
This includes public attitudes surveys around indoor air
quality as a cause and support for specific technologies
like GUV; early surveys already show broad support
for GUV. There could also be research around ways to
best educate the public and policymakers about indoor
air quality issues, and message-testing to encourage
adoption of indoor air quality measures.
Coordination
To provide a rough estimate of the impact of a wide- spread air quality campaign in the US on endemic dis- ease burden, we made some basic assumptions about
the timeline and possible impact of a campaign, and
compared the result against a counterfactual baseline.
You can see our calculation here and input new as- sumptions to see how they affect a campaign’s impact.
This calculation demonstrates that there is a strong
benefit from widespread indoor air quality improve- ments on endemic respiratory disease burden, even
before accounting for catastrophic pandemics. This
benefit should make indoor air quality improvements
more politically viable.
Many indoor air quality projects could build on each
other and create momentum for further efforts, and
a dedicated funding pathway could coordinate several
complementary projects. For example, a useful long- term path might start by funding a set of scientific
studies. As research produces further data on inter- ventions and optimal programs, funding could be used
for dedicated advocacy and deployment in partnership
with early organizational adopters. This implementa- tion would in turn lead to iterative research and wider
deployment.
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Projects in these areas could absorb significant
amounts of funding along a wide range. For example:
• $25,000 could fund the development of a detailed
infection model.
• $20M could fund a single dedicated clinical project
(e.g. something like EMIT-2).
• $200M could fund a program consisting of several
complementary projects (e.g. far-UVC light safety
studies, real-world efficacy studies for IAQ interven- tions, advocacy for improved pandemic prepared- ness standards, etc.).
Possibilities for immediate action • Early adopters will be an important part of any push
for improvements in indoor air quality, and organi- zations could begin to install upper-room GUV light
and low-wave light immediately. Philanthropists or
government bodies can be helpful here by providing
partial or full funding to corporate partners who
might not undertake this effort alone. Early adop- tion would allow efficacy data to be collected for
different offices, providing real-world data to incor- porate into detailed models.
• Far-UVC light still needs extensive safety testing. We
are aware of collaborators who are interested in de- signing and running a safety test in the near future.
• Far-UVC light still needs to be assessed for use in
close-range transmission mitigation.
• More detailed models are needed to form the basis
for improved standards; we know of at least one
researcher, Jacob Bueno de Mesquita of Lawrence
Berkeley National Laboratory, who is in the process
of developing such a model and is seeking funding
to invest more time in it. A funder could provide
funding to complete his model for about $25,000.34
• More investment is needed in solid-state far-UVC
technology, including in fundamental research of
the type normally done through academic institu- tions. There are companies working on improving
far-UVC technology, but funders could add to this
effort by supporting academic research in the area.
As a basic heuristic, a PhD student costs roughly
34 We were recently informed that Prof. Ernest P. Blatchley III of Purdue University is working on something similar, although we have
not spoken with him.
$70,000 per year, and an applied research project in
this field might take about two years to demonstrate
promise and another two to come to fruition. An ex- ample philanthropic program to support fundamen- tal research in this area might therefore support five
students for two years each, and then choose two
out of those five to support for another two years,
for a total cost under $1 million. Alternatively, a
philanthropic funder might make an investment in a
tech startup, prioritizing impact over returns (unlike
typical private investors).
Risk Factors
There are a few reasons ways IAQ interventions could
fail or even be harmful:
• IAQ interventions fail to substantially reduce global
catastrophic biorisk due to incomplete coverage, e.g.,
some studies of GUV in schools find no effect on
measles incidence because students end up catching
measles in transit to school.
• It may turn out that for catastrophic pandemic-class
pathogens, IAQ interventions are not as effective
as planned because reducing pathogen levels in the
air might not substantially reduce transmission and
infection rates, e.g., it could be the case that it is easy
to be infected by very low doses.
• It is unlikely, given the dose-infection patterns of
known pathogens, that reducing pathogens doses
would be totally ineffective. Although trans- mission sites can shift without reducing overall
transmission, reducing the speed of transmission
can still buy valuable time for countermeasures to
be enacted.
• IAQ interventions could reduce population immu- nity due to a lack of ordinary virus exposure such
that the transmissibility of biothreats is not much
reduced. It might even be the case that ordinary
airborne pathogens, like the common cold, become
more destructive to those who contract them.
• Typically, this concern does not arise when dis- cussing other pathogen routes. Environmental
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pathogen reduction has historically been enor- mously beneficial for humanity, as demonstrated
by the vast life quality and longevity increases
coming from the reduction in waterborne patho- gens.
• Far-UVC light might result in long-term safety
issues, such as effects on the skin microbiome, that
are difficult to resolve in safety studies.
• If there are long-term health issues, it may still be
the case that the expected value of mass deploy- ment of this system reduces global catastrophic
biological risk to the degree that it’s still better to
have it than not.
• However, health issues (even if they are relatively
minor) introduce legal liabilities for organizations
producing, selling, and employing this technology
and may result in consumer and public sentiment
being hostile to this technology and any associat- ed organizations.
• GUV could produce harmful pollutants through
interaction with particles and gasses in the air, which
negatively impact respiratory health.
• These pollutants could be addressed by filtration,
but filtration would have to be used comprehen- sively in order to completely counteract the effect,
which would correspondingly raise the price of
UV light installation.
• It is likely that it would still be net beneficial to
install far-UVC lights in high-risk places; detailed
cost-benefit analyses are needed for various envi- ronments.
• There could be some form of risk compensation,
where people overestimate the benefit of this tech- nology and after adopting it, become less inclined to
use other biorisk-reducing measures (e.g. PPE, social
distancing).
• Encouraging the adoption of filtration and up- per-room UV now may make it more difficult to get
far-UVC light installed in public indoor spaces later
because of an infrastructure “lock-in” effect, where
an incumbent technology prevents the take-up of
potentially superior alternatives.
• Regulation on dosage for far-UVC light could be set
at levels that are too low for reducing the chance of
existential biorisk (e.g. reducing transmissibility of a
measles-equivalent agent).
• There could be a negative shift in public perception
of IAQ interventions unrelated to actual health
issues, which prevents mass deployment (similar to
anti-vaccine sentiment).
• The FDA could classify specific IAQ interventions
as medical devices, subjecting them to constraining
regulations and making widespread deployment
more difficult.
• Doing a poor job with the rollout of IAQ interven- tions or attempts at altering standards and regula- tions might “poison the well” for better attempts
later, e.g. due to a very small number of high-profile
failures.
• Adversaries could start incorporating IAQ interven- tions into their plans for developing and deploying
pandemic-class agents.
• This is probably minimally relevant as GUV de- nies adversaries several attack vectors, making the
chance of a successful attack less likely.
• It is probably difficult to develop agents that can
withstand high enough levels of UVC light, but if
placement is partial then adversaries may be able
to exploit gaps. Multi-wavelength systems would
be even more difficult to work around.
• UV light degrades plastics over time and plastic is
ubiquitous in our daily environments.
• Boeing found no mechanical degradation in
plastics from simulating an airplane interior
disinfection process using far-UVC (although the
exposure time was significantly lower than would
occur if far-UVC were broadly implemented for
reduction in disease transmission).
• Different plastics are affected to different degrees
and strengthening/protective additives can avert
the degradation, so much of the issue could be
avoided through careful materials choice.
• Generally, the rate of degradation may overall be
negligible compared with the standard lifetime of
consumer products.
Many of these risk factors can be mitigated by the
activities recommended in this report (e.g., developing