UV-C LIGHTS OVERVIEW

What is UV Light?

This type of light is naturally emitted by the sun, but it can also be generated artificially by lamps and light fixtures. Within the spectrum of sunlight, the light with a wavelength of 100 to 400 nanometers (nm) is called ultraviolet light. It can be divided into UV-A (315 to 400 nm), UV-B (280 to 315 nm), and UV-C (200 to 280 nm). Unlike with regular fluorescent light tube products, which allow us to visually confirm light brightness, assessing light intensity on a UV lighting device is more complicated, as UV light is invisible to the naked eye.

For decades, the scientific community has been aware about the disinfection ability of ultraviolet light (UV) wavelengths.

As mentioned above, UV wavelengths can range anywhere from 100 to 400 nm, and comprise distinct spectra. UV-A and UV-B have a spectrum range higher than 300 nm, which fails to inactivate pathogens, rendering them ineffective for disinfection applications. However, UV-C light falls between 200 and 280 nm (peak at 250-275 nm) and bears the ability to kill pathogens. Also known as germicidal light, this UV range includes far-UV-C radiation and UV-C radiation. Far UV-C is currently been tested to guarantee its safety on skin and eyes, and has a range of 207 to 222 nm.

 

How UV-C Works

With the rapid development of UV-C applications for disinfection purposes, there is a growing need to quantify and determine if a UV-C lamp or setup will accomplish the desired results.

Research has shown that DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) absorb ultraviolet radiation most readily at wavelengths between 254 and 275 nm. Since UV-C falls within this range, UV-C technology is capable to penetrate the cell membrane and nucleus of pathogens.

When the DNA and RNA in the cells of a pathogen are exposed to UV-C radiation, a chemical change occurs in the nucleic acids, resulting in a corruption in the genetic code. During this process, called dimerization, UV-C radiation inactivates the pathogen by causing cellular inability to regenerate or replicate, or by causing cell death.

Due to this ability, UV-C light is also known as germicidal UV, and has been proven to successfully neutralize the effect of a variety of pathogens, such as bacterial propagules, spores, viruses, fungi, etc.

Why Choose UV Sanitizer

The Illuminating Engineering Society (IES) has released a new report on Germicidal Ultraviolet (GUV) light and how it could reduce the spread of COVID-19. With the right equipment, germicidal UV can successfully and safely be used to disinfect air in occupied spaces, such as hospital waiting rooms, intensive care units and operating rooms, as well as clinics, offices, manufacturing and transportation facilities, schools, houses, etc.

In unoccupied controlled-access environments, UV-C can be used as a supplemental measure to disinfect room surfaces, greatly reducing the spread of healthcare-associated contamination. Germicidal UV-C is also currently being used for the disinfection of certain types of personal protective equipment (PPE) for limited reuse during the pandemic.

AMTEK helps you to breathe safer in a healthier environment

How UV-C is measured

  • Irradiance

Irradiance is the flux of radiant energy per unit area (normal to the direction of flow of radiant energy through a medium).

It is a way to measure how much [light density of radiation incident on a given surface area] total UV-C energy has irradiated a surface at certain distance. Irradiance is expressed in microwatts per square centimeter per distance (μW•S /cm2 •distance).

This measurement can be used to evaluate both the efficacy and safety of a device.

The relationship between irradiance and source-surface distance can be expressed by the inverse square law in which the peak intensity on a surface decreases exponentially with distance.

The real value would require taking into account the viewing angle, radiation pattern, area of interest on the surface, and other external factors such as potential reflection from the environment.

IRRADIANCE map using 250 Watts UV-C lamp

  • Fluence

Fluence is another way to measure how much total UV-C energy has irradiated a surface during a certain amount of time. It is also sometimes referred to as UV-C dosage or UV-C exposure dosage.

A key component of successful UV-C disinfection is ensuring the pathogen is exposed to the right light fluence (UV-C dosage) so the UV-C radiation can be absorbed through its membrane. In fact, this is the most crucial element in UV-C system design, because fluence is the primary determinant to successful pathogen inactivation. Different pathogens will require different doses of UV-C light to be killed or inactivated.

Fluence is expressed in milijoules per cm2 (mJ/cm2) and is the dosage of UV-C exposure required to neutralize a specific pathogen. Calculated for water, surface, and air disinfection the formula is:

UV-C irradiance (μW/cm2) × exposure time (seconds)

The fluence value can be augmented by

1) Increasing the strength of the UV-C light source wattage generated,

2) Increasing the time/exposure to the UV-C light source or,

3) By decreasing the distance between UV-C light source and the object to be disinfected.

FLUENCE map using 250 Watts UV-C lamp with 10 minutes

  • What Fluence Is Required?

This depends on the following factors:
• Kind of pathogens to be treated
• Level of disinfection / log reduction
• UV wavelength(s) delivered
• Time

The degree of pathogen inactivation by ultraviolet radiation is directly related to the UV-C dose applied. This dose is the product of UV-C irradiance (I, as expressed as energy per unit surface area) and exposure time (T). Therefore: DOSE = I x T.


The UV-C dose required does depend on the task and/or the situation.

  • Log Reduction

It is essential to understand what logarithmic (log) reduction is and why it is important to the process of surface disinfection. Scientists, engineers, and other professionals who are responsible, sometimes even legally, for preventing illness and pathogenic contamination, use log reduction as a measure to evaluate the level of elimination of the microbial bio-burden.

The term log is short for logarithm, a mathematical term for a power to which a number can be raised. For example, using 10 as the given number, a log 2 increase can be shown as 102 or 10 x 10 = 100.

Once the log value is obtained, the reduction of microorganisms is calculated using a logarithmic scale as shown on the graphic below.

 

This table is an example of log reduction values using a starting point of one (1) million bacteria or 1,000,000 CFU’s on a surface (i.e.: under bed rails in a hospital), as outlined below:

NOTE: The UV-C exposure dosage needed for each level of reduction is shown on Appendix A (Tables) along with the published reference in Appendix C (References), where the data came from.

  • Why Log Reduction is important.

    Hospital surfaces can be contaminated with pathogenic organisms, and achieving a reduction of only 6.0 log or below means enough cells of dangerous viruses, bacteria, fungus, or Clostridium difficile (C. diff) spores, can or will be left behind to proliferate and repopulate surfaces within the treated area.

    Literature shows that pathogens can be spread, contaminate patients, and/or grow new bacterial and fungal colonies on new surfaces (Koganti, S. & Donskey, C., 2016).


    The number of pathogen survivors is very important because they can increase their populations exponentially in a very short time. For example, Staphylococcus aureus (S. aureus), under ideal conditions, doubles its colony size in 24-30 minutes (Generation Time, G). This means 1,000 (or 103 or log 3) pathogen individuals would increase to 2,000 after 30 minutes, 60 minutes later they would have increased to 4,000, and after two hours to 16,000 and then to over one million (1,024,000) after 5 hours or more, if the growing environment is optimal.


    Log Reduction Examples for Clostridium Difficile (C. diff) Spores

    A UV-C product was shown by Cadnum & Donskey (2016) to achieve a low reduction of about 3.3 log on an inoculated surface placed at four (4) feet away from the light source and after a 40 min exposure. In this case, only surfaces exposed in a favorable manner were tested on (i.e.: facing light source and 4 ft or less away from it) (Cadnum, J. L., Donskey, C., 2016).

    When calculating a reduction of 3.3 log, if the surface is contaminated with 1,000,000 spores, that means there will be more than 100 C. difficile survivors remaining that can repopulate surfaces and infect people.

    Another UV-C light product was shown by Dr. J. Boyce, MD (2016) to achieve a log reduction range of 2.0 – 4.0 for C. difficile, after a manufacturer recommend a fifteen (15) minute treatment on an inoculated surface at a zero (0) degree angle to the light, and only four (4) feet from the light source (Boyce, J.M., 2016).

    When calculating a log reduction of 2.0 – 4.0, if the surface is contaminated with 1,000,000 spores, that means there will be between about 100 to 10,000 C. difficile survivors remaining.

    Evidently, none of the examples above achieve disinfection, decontamination, or sterilization.

UV-C LAMP TECHOLOGY

Induction Lamp Technology

Advantages of Magnetic Induction Technology

  • Quartz lamp made in Japan
  • Long life lamp > 50,000 hrs.
  • Zero maintenance cost
  • 254 nm perfect spectrum
  • 185 nm to get Ozone output
  • Suitable for large spaces
  • Movable and easy to use device
  • Working temperature from -20˚C to +100˚C
  • Capability of working under water at 50cm. depth

LED Lamp Technology

With the development of better chips and components, UV-C LED technology is in constant progress. Nonetheless, as was the case with LED lighting from a few years back, today UV-A, UV-B, and UV-C LEDs aren’t yet as powerful as linear and induction technology tubes. However, there are many applications in which UV-C LED technology at close range is very reliable. Additionally, UV-C LEDs are able to generate a more precise UV-C spectrum than linear and induction lamps. UV-C LEDs generally work at 260 – 280 nm.

Today, technologically advanced UV-C LED devices such as Hand-Rail disinfection units for electric stairs, counterfeit detection systems, low-power equipment sterilizers, and portable curing and coating methods offer great application possibilities to users. Initially used predominantly in the printing industry, the UV-C LED is today being used in a variety of fields: medical, automotive, security, electronics, and more.

Electrical Stairs Handrail LED UV-C disinfection device

UV-C Light Applications

Water

  • Water plants purification
  • Water wells & water cisterns
  • Households under sink installations
  • Ice making machines
  • Water vending machines
  • Laundry water
  • Schools, restaurants, airports and hotels
  • Aquarium, hatcheries, and nurseries
  • Swimming pools & hot tubs
  • Farms, ranches & trailer parks
  • Boats & recreational vehicles

Food Processing

  • Food processing (processing, warehousing, handling, production dept., salad bars, buffets, bakeries, restaurants), meat, poultry, dairy -agriculture plants
  • Bottling facilities
  • Soft & fruit drinks, and juices
  • Brewery & winery

a

Medical

  • Laboratories, hospitals, and clinics
  • Pharmaceutical production
  • Pathology labs, kidney dialysis
  • Agriculture (animal husbandry)

Industries

  • Cosmetics and electronic production
  • Metal & mechanic plants
  • Biotech industry (research labs, biotech labs, equipment sterilization)
  • Public & private ground [buses, vehicles, trains, sub-ways, trucks] and air [aircraft cabins, airports] transportation disinfection
  • Clean rooms
  • Public toilets
  • Printing
  • Personal UV-C disinfections units
  • HAVC systems (commercial, industrial, healthcare, and residential)
  • Water treatment plants
  • Banks money disinfection
  • Lake & pond reclamation

UV-C Light Features and Benefits

  • Environmentally friendly, no dangerous or toxic chemicals on the air or water
  • Effective Germicidal Wavelength
  • Effective Eradication of Most Spores
  • Covering Large Production Capacity of UV-C
  • UV treatment is highly compatible with other treatment processes
  • Cost effective, low initial capital costs and reduced operating costs
  • Flexible design capabilities for custom lamp system development
  • Equipment with wide Operating Temperature

APPENDIX A: Tables

Table 1. UV Doses for Multiple Log Reductions for Various Spores

Spore Lamp Type UV Dose (Fluence) (mJ/cm2) for a given Log Reduction without photo-reactivation Reference
1 2 3 4 5 6 7
Bacillus subtilis ATCC6633 N/A 36 48.6 61 78 Chang et al. 1985
Bacillus subtilis ATCC6633 LP 24 35 47 79 Mamane-Gravetz and Linden 2004
Bacillus subtilis ATCC6633 LP 22 38 >50 Sommer et al. 1998
Bacillus subtilis ATCC6633 LP 20 39 60 81 Sommer et al. 1999
Bacillus subtilis WN626 LP 0.4 0.9 1.3 2 Marshall et al., 2003

Table 2. UV Doses for Multiple Log Reductions for Various Bacteria

Bacterium Lamp Type UV Dose (Fluence) (mJ/cm2) for a given Log Reduction without photo-reactivation Reference
1 2 3 4 5 6 7
Aeromonas hydrophila ATCC7966 LP 1.1 2.6 3.9 5 6.7 8.6 Wilson et al. 1992
Aeromonas salmonicida LP 1.5 2.7 3.1 5.9 Liltved and Landfald 1996
Campylobacter jejuni ATCC 43429 LP 1.6 3.4 4 4.6 5.9 Wilson et al. 1992
Citrobacter diversus LP 5 7 9 11.5 13 Giese and Darby 2000
Citrobacter freundii LP 5 9 13 Giese and Darby 2000
Escherichia coli ATCC 11229 N/A 2.5 3 3.5 5 10 15 Harris et al. 1987
Escherichia coli ATCC 11229 N/A 3 4.8 6.7 8.4 10.5 Chang et al. 1985
Escherichia coli ATCC 11229 LP <5 5.5 6.5 7.7 10 Zimmer et al. 2002
Escherichia coli ATCC 11229 MP <3 <3 <3 <3 8 Zimmer et al. 2002
Escherichia coli ATCC 11229 LP 7 8 9 11 12 Hoyer 1998
Escherichia coli ATCC 11229 LP 3.5 4.7 5.5 6.5 7.5 9.6 Sommer et al. 2000
Escherichia coli ATCC 11229 LP 6 6.5 7 8 9 10 Sommer et al. 1998
Escherichia coli ATCC 11303 LP 4 6 9 10 13 15 19 Wu et al. 2005
Escherichia coli ATCC 25922 LP 6 6.5 7 8 9 10 Sommer et al. 1998
Escherichia coli C LP 2 3 4 5.6 6.5 8 10.7 Otaki et al. 2003
Escherichia coli O157:H7 LP 1.5 3 4.5 6 Tosa and Hirata 1999
Escherichia coli O157:H7 LP <2 <2 2.5 4 8 17 Yaun et al. 2003
Escherichia coli O157:H7 CCUG 29193 LP 3.5 4.7 5.5 7 Sommer et al. 2000
Escherichia coli O157:H7 CCUG 29197 LP 2.5 3 4.6 5 5.5 Sommer et al. 2000
Escherichia coli O157:H7 CCUG 29199 LP 0.4 0.7 1 1.1 1.3 1.4 Sommer et al. 2000
Escherichia coli O157:H7 ATCC 43894 LP 1.5 2.8 4.1 5.6 6.8 Wilson et al. 1992
Escherichia coli O25:K98:NM LP 5 7.5 9 10 11.5 Sommer et al. 2000
Escherichia coli O26 LP 5.4 8 10.5 12.8 Tosa and Hirata 1999
Escherichia coli O50:H7 LP 2.5 3 3.5 4.5 5 6 Sommer et al. 2000
Escherichia coli O78:H11 LP 4 5 5.5 6 7 Sommer et al. 2000
Escherichia coli K-12 IFO3301 LP&MP 2 4 6 7 8.5 Oguma et al. 2002
Escherichia coli K-12 IFO3301 LP&MP 2.2 4.4 6.7 8.9 11.0 Oguma et al. 2004
Escherichia coli K-12 IFO3301 LP 1.5 2 3.5 4.2 5.5 6.2 Otaki et al. 2003
Escherichia coli Wild type LP 4.4 6.2 7.3 8.1 9.2 Sommer et al. 1998

Table 3. UV Doses for Multiple Log Reductions for Various Protozoa

Protozoan Lamp Type UV Dose (Fluence) (mJ/cm2) for a given Log Reduction without photo-reactivation Reference
1 2 3 4 5 6 7
Cryptosporidium hominis LP & MP 3 5.8 Johnson et al. 2005
Cryptosporidium parvum, oocysts, tissue culture assay N/A 1.3 2.3 3.2 Shin et al. 2000
Cryptosporidium parvum LP & MP 2.4 <5 5.2 9.5 Craik et al. 2001
Cryptosporidium parvum MP <5 <5 <5 ~6 Amoah et al. 2005
Cryptosporidium parvum MP <10 <10 <10 Belosevic et al. 2001
Cryptosporidium parvum LP 1 2 <5 Shin et al. 2001
Cryptosporidium parvum MP 1 2 2.9 4 Bukhari et al. 2004
Cryptosporidium parvum LP <2 <2 <2 <4 <10 Clancy et al. 2004
Cryptosporidium parvum MP <3 <3 3-9 <11 Clancy et al. 2000
Cryptosporidium parvum LP <3 <3 3-6 <16 Clancy et al. 2000
Cryptosporidium parvum LP 0.5 1 1.4 2.2 Morita et al. 2002
Cryptosporidium parvum LP 2 <3 <3 Zimmer et al. 2003
Cryptosporidium parvum MP <1 <1 <1 Zimmer et al. 2003
Encephalitozoon cuniculi, microsporidia LP 4 9 13 Marshall et al. 2003
Encephalitozoon hellem, microsporidia LP 8 12 18 Marshall et al. 2003
Encephalitozoon intestinalis, microsporidia LP & MP <3 3 <6 6 Huffman et al. 2002
Encephalitozoon intestinalis, microsporidia LP 3 5 6 Marshall et al. 2003
Giardia lamblia, gerbil infectivity assay LP <0.5 <0.5 <0.5 <1 Linden et al. 2002b
Giardia lamblia LP <10 ~10 <20 Campbell et al. 2002
Giardia lamblia LP <2 <2 <4 Mofidi et al. 2002
Giardia lamblia,excystation assay N/A > 63 Rice and Hoff 1981
Giardia lamblia, excystation assay N/A 40 180 Karanis et al. 1992
Giardia muris, excystation assay N/A 77 110 Carlson et al. 1985
G. muris, cysts, mouse infectivity assay N/A <2 <6 10 + tailing Craik et al. 2000
Giardia muris MP 1 4.5 28 + tailing Craik et al. 2000
Giardia muris MP <10 <10 <25 ~60 Belosevic et al. 2001
Giardia muris LP <1.9 <1.9 ~2 ~2.3 Hayes et al. 2003
Giardia muris LP <2 <2 <4 Mofidi et al. 2002
G. muris, cysts MP <5 <5 5 Amoah et al. 2005

Table 4. UV Doses for Multiple Log Reductions for Various Viruses

Virus Host Lamp Type UV Dose (Fluence) (mJ/cm2) per Log Reduction Reference
1 2 3 4 5 6
PRD-1 (Phage) S. typhimurium Lt2 N/A 9.9 17.2 23.5 30.1 Meng and Gerba 1996
B40-8 (Phage) B. Fragilis LP 11 17 23 29 35 41 Sommer et al. 2001
B40-8 (Phage) B. fragilis HSP-40 LP 12 18 23 28 Sommer et al 1998
MS2 (Phage) Salmonella typhimurium WG49 N/A 16.3 35 57 83 114 152 Nieuwstad and Havelaar 1994
Virus Host Lamp Type UV Dose (Fluence) (mJ/cm2) per Log Reduction Reference
1 2 3 4 5 6
MS2 DSM 5694 (Phage) E. coli NCIB 9481 N/A 4 16 38 68 110 Wiedenmann et al. 1993
MS2 ATCC 15977-B1 (Phage) E. coli ATCC 15977–B1 LP 15.9 34 52 71 90 109 Wilson et al. 1992
MS2 NCIMB 10108 (Phage) Salmonella typhimurium WG49 N/A 12.1 30.1 Tree et al. 1997
MS2 (Phage) E. coli K-12 Hfr LP 21 36 Sommer et al. 1998
MS2 (Phage) E. coli CR63 N/A 16.9 33.8 Rauth 1965
MS2 (Phage) E. coli 15977 N/A 13.4 28.6 44.8 61.9 80.1 Meng and Gerba 1996
MS2 (Phage) E. coli C3000 N/A 35 Battigelli et al. 1993
MS2 (Phage) E. coli ATCC 15597 N/A 19 40 61 Oppenheimer et al. 1993
MS2 (Phage) E. coli C3000 LP 20 42 69 92 Batch et al. 2004
MS2 (Phage) E. coli ATCC 15597 LP 20 42 70 98 133 Lazarova and Savoye 2004
MS2 (Phage) E. coli ATCC 15977 LP 20 50 85 120 Thurston-Enriquez et al., 2003
MS2 (Phage) E. coli HS(pFamp)R LP 45 75 100 125 155 Thompson et al. 2003
MS2 (Phage) E. coli C3000 LP 20 42 68 90 Linden et al. 2002a
MS2 (Phage) E. coli K-12 LP 18.5 36 55 Sommer et al. 2001
MS2 (Phage) E. coli NCIMB 9481 N/A 14 Tree et al. 2005
PHI X 174 (Phage) E. coli WG5 LP 2.2 5.3 7.3 10.5 Sommer et al. 1998
PHI X 174 (Phage) E. coli C3000 N/A 2.1 4.2 6.4 8.5 10.6 12.7 Battigelli et al. 1993
PHI X 174 (Phage) E. coli ATCC15597 N/A 4 8 12 Oppenheimer et al. 1993
PHI X 174 (Phage) E. coli WG 5 LP 3 5 7.5 10 12.5 15 Sommer et al. 2001
PHI X 174 (Phage) E. coli ATCC 13706 LP 2 3.5 5 7 Giese and Darby 2000
Staphylococcus aureus phage A 994 (Phage) Staphylococcus aureus 994 LP 8 17 25 36 47 Sommer et al. 1989
Calicivirus canine MDCK cell line LP 7 15 22 30 36 Husman et al. 2004
Calicivirus feline CRFK cell line LP 7 16 25 Husman et al. 2004
Calicivirus feline CRFK cell line N/A 4 9 14 Tree et al. 2005
Calicivirus feline CRFK cell line LP 5 15 23 30 39 Thurston-Enriquez et al. 2003
Adenovirus type 2 A549 cell line LP 20 45 80 110 Shin et al. 2005
Adenovirus type 2 Human lung cell line LP 35 55 75 100 Ballester and Malley 2004
Adenovirus type 2 PLC / PRF / 5 cell line LP 40 78 119 160 195 235 Gerba et al. 2002
Adenovirus type 15 A549 cell line (ATCC CCL-185) LP 40 80 122 165 210 Thompson et al. 2003
Adenovirus type 40 PLC / PRF / 5 cell line LP 55 105 155 Thurston-Enriquez et al. 2003
Adenovirus type 40 PLC / PRF / 5 cell line LP 30 ND ND 124 Meng and Gerba 1996
Adenovirus type 41 PLC / PRF / 5 cell line LP 23.6 ND ND 111.8 Meng and Gerba 1996
Poliovirus Type 1 ATCC Mahoney N/A N/A 6 14 23 30 Harris et al. 1987
Poliovirus Type 1 LSc2ab () MA104 cell N/A 5.6 11 16.5 21.5 Chang et al. 1985
Poliovirus Type 1 LSc2ab BGM cell LP 5.7 11 17.6 23.3 32 41 Wilson et al. 1992
Poliovirus 1 BGM cell line N/A 5 11 18 27 Tree et al. 2005
Poliovirus 1 CaCo2 cell-line (ATCC HTB37) LP 7 17 28 37 Thompson et al. 2003
Poliovirus 1 BGM cell line LP 8 15.5 23 31 Gerba et al. 2002
Poliovirus Type Mahoney Monkey kidney cell line Vero LP 3 7 14 40 Sommer et al. 1989
Coxsackievirus B5 Buffalo Green Monkey cell line N/A 6.9 13.7 20.6 Battigelli et al. 1993
Coxsackievirus B3 BGM cell line LP 8 16 24.5 32.5 Gerba et al. 2002
Coxsackievirus B5 BGM cell line LP 9.5 18 27 36 Gerba et al. 2002
Reovirus-3 Mouse L-60 N/A 11.2 22.4 Rauth 1965
Reovirus Type 1 Lang strain N/A N/A 16 36 Harris et al. 1987
Rotavirus SA-11 Monkey kidney cell line MA 104 LP 8 15 27 38 Sommer et al. 1989
Rotavirus SA-11 MA-104 cell line N/A 7.6 15.3 23 Battigelli et al. 1993
Rotavirus SA-11 MA-104 cell line N/A 7.1 14.8 25 Chang et al. 1985
Rotavirus SA-11 MA-104 cell line LP 9.1 19 26 36 48 Wilson et al. 1992
Rotavirus MA104 cells LP 20 80 140 200 Caballero et al. 2004
Hepatitis A HM175 FRhK-4 cell LP 5.1 13.7 22 29.6 Wilson et al. 1992
Hepatitis A HAV/HFS/GBM N/A 5.5 9.8 15 21 Wiedenmann et al. 1993
Hepatitis A HM175 FRhK-4 cell N/A 4.1 8.2 12.3 16.4 Battigelli et al. 1993
Echovirus I BGM cell line LP 8 16.5 25 33 Gerba et al. 2002
Echovirus II BGM cell line LP 7 14 20.5 28 Gerba et al. 2002

APPENDIX B: UV-C Disinfection Background

Below are some key contributions over the years to the study of microorganisms and their response to UV-C light in the form of germicidal lamps.

1845 – It became known that microorganisms respond to light.

1855 – Arloing and Daclaux demonstrated that sunlight killed Bacillus anthracis and Tyrothrix scaber.

1877 – Downes and Blunt reported that bacteria were inactivated by sunlight – the violet blue area of the spectrum being the most effective. Exposing test tubes containing Pasteur’s solution to sunlight prevented the growth of microorganisms inside the tube and, upon increased exposure durations, the test tubes remained bacteria-free for several months.

These early investigations pointed to key factors that influence ultraviolet germicidal irradiation (UVGI):

  • Inactivation of a given quantity of organisms is dependent on the dose of radiation received.
  • Dose is the product of intensity and exposure duration.
  • Inactivation is also dependent on the wavelength of the received radiation.

1889 Widmark confirmed UV-C rays from arc lamps were responsible for microorganism inactivation.

1890 – Koch proved the lethal effect of sunlight on tuberculosis, which was an early indicator of the modern use of UV-C to combat this disease.

1892 – Geisler used a prism and heliostat to show that sunlight and electric arc lamps are lethal to Bacillus Typhosus.

1903 – Niels Ryberg Finsen (1860-1904) was awarded the Nobel Prize for Medicine, after being the first to employ UV-C rays in treating disease. He invented the Finsen curative lamp, which was used successfully through to the 1950s.

1903 – Banard and Morgan determined that a UV-C spectrum within 226-328 nm is biocidal.

1908 – UV-C was used to disinfect the municipal water supply of Marseille, France.

1930s – Westinghouse developed the first commercial UV-C germicidal lamps, which were used primarily in hospitals.

1932 – Ehris and Noethling isolated biocidal spectrum to 253.7 nm.

1933-1935 – William F. Wells showed that organisms in droplet expectoration could be killed in the air with UV-C.

1937-1941 – Wells showed that germicidal UV radiation in the upper section of the room prevented measles from spreading in public schools. However, there have been difficulties in replicating these findings.

Post World War II – UV-C was used for sterilizing air in hospitals, kitchens, meat storage and processing plants, bakeries, breweries, dairies, beverage production, pharmaceutical plants and animal labs; anywhere microbiological contamination was a concern.

1950s – UV-C was incorporated into air handling equipment. It became a major component in the control and eradication of tuberculosis (TB) after Riley proved its effectiveness in 1957.

1960s – Concern about microbes decreased with the introduction and increasing availability of new drugs and sterilizing cleaners.

1970s – The energy crisis during this decade sparked enthusiasm for conservation. To save energy, heating, ventilating, and air-conditioning (HVAC) systems were shut down when not in use. Condensation that had previously been evaporated by the constantly moving air was now collecting on coils and drain pans. As a result, mold and other microorganisms multiplied in this dark, wet environment. When the systems were re-started, microbial contaminants would circulate throughout the building.

1994 – The CDC acknowledged UV-C’s effectiveness for TB control.

1999 – The WHO recommended the use of UVGI for TB control.

2014 – UV-C was used as part of the final cleaning procedure within the Nebraska Biocontainment Unit upon Ebola patient discharge.

2020 – UV-C light was recommended for the disinfection of N95 masks and other PPE during SARS-CoV-2 pandemic.

Recent technological advancements have made it possible for UV-C disinfection technology to be used in an ever-expanding range of applications.

Through strategic partnerships with leading manufacturers, UV-C technology providers are uniquely positioned to present their customers with the best UV-C germicidal products to meet their specific needs.

APPENDIX C: References

Amoah, K., Craik, S., Smith, D. W. & Belosevic, M. (2005). Inactivation of Cryptosporidium oocysts and Giardia cysts by ultraviolet light in the presence of natural particulate matter. Journal of Water Supply, Research and Technology-Aqua, 54 (3): 165–178.

Ballester, N. A. & Malley, J. P. (2004). Sequential disinfection of adenovirus type 2 with UV-chlorine- chloramine. Journal American Water Works Association, 96(10): 97-103.

Batch, L. F., Schulz, C. R. & Linden, K. G. (2004). Evaluating water quality effects on UV disinfection of MS2 coliphage. Journal American Water Works Association, 96(7): 75-87.

Battigelli, D. A., Sobsey, M. D. & Lobe, D. C. (1993). The inactivation of Hepatitis A virus and other model viruses by UV irradiation. Water Science & Technology, 27(3-4): 339-342.

Belosevic, M., Craik, S. A., Stafford, J. L. Neumann, N. E., Kruithof, J. & Smith, D. W. (2001). Studies on the resistance/reaction of Giardia muris cysts and C. parvum oocysts exposed to medium-pressure ultraviolet radiation. FEMS Microbiology Letters, 204(1): 197-204.

Bolton J. R. & Linden, K. G. (2003). Standardization of Methods for Fluence (UV Dose) Determination in Bench-Scale UV Experiments. Journal of Environmental Engineering, 129(3): 209-216.

Boyce, J. M., Farrel, P. A.,Towle, D., Fekieta, R., & Aniskiewicz, M. (2016). Impact of Room Location on UV-C Irradiance and UV-C Dosage and Antimicrobial Effect Delivered by a Mobile UV-C Light Device. Infection Control Hospital Epidemiology, 37(6): 667-72.

Bukhari, Z., Abrams, F. & LeChevallier, M. (2004). Using ultraviolet light for disinfection of finished water. Water Science & Technology, 50(1): 173-178.

Caballero, S., Abad, F. X., Loisy, F., Le Guyader, F. S., Cohen, J., Pintó, R. M. & Bosch, A. (2004). Rotavirus virus-like particles as surrogates in environmental persistence and inactivation studies. Applied and Environmental Microbiology, 70(7): 3904-3909.

Cadnum, J. L., Tomas, M. E., Sankar, T., Jencson, A., Mathew, J. I., Kundrapu, S. & Donskey, C. J. (2016). Effect of Variation in Test methods on Performance of Ultraviolet-C Radiation Room Decontamination. Infection Control Hospital Epidemiology, 37(5): 555-60

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