Will an 11W UVC lamp kill bacteria?

Will an 11W UVC lamp kill bacteria?

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If I shone a UVC lamp (11W) on something (say for example a plastic phone case) for an hour, would that kill off a noticeable amount of bacteria? That is, if I were to go over the case with a cotton swab before the hour and swipe the cotton swab over a petri dish with nutrients and if I were to do the same after the hour with a different cotton swab and a different petri dish. Do you think that after a week there would be a noticeable difference in bacterial growth between the dishes? I think it should, since some filters for ponds work the same way, but I'm not sure, since in my case, the light needs to penetrate about 10 inches of air first and the environment isn't as closed off. What are your ideas on this?

Some physical methods of sterilisation are in hospitals

  • Steam autoclaving
  • Dry heat - thermostat
  • White light / UV light sterilization

where continuous UV light has poor penetration. UV radiation heat is absorbed by proteins and nucleic acid. All micro-organisms contain tehm. They inactivate the DNA. There will be electronic and photochemical reactions by

  • photolysis
  • loss of colony-forming ability
  • enzyme inactivation
  • destruction of nucleic acid.

If I shone a UVC lamp (11W) on something (say for example a plastic phone case) for an hour, would that kill off a noticeable amount of bacteria?

Direct answer: Not all bacteria, but some. UV light has poor penetration so it will not expose all bacteria. Most prevalent bacteria there

  • streptococci,
  • staphylococci and
  • some others.

I estimate that the majority of the bacteria will remain because the light cannot reach each corner of the object. In clinics, many hours and high temperatures are used to kill bacteria. UV light is not efficient there. I think the problem is that you cannot reach each corner of the object. The high temperature and disinfectants can then again reach the clinical instruments throughly. Manual work is however still needed.

You can then take examples of bacteria. Search their corresponding temperature ranges. The survival can also be dependent on the nature of the light of the bulb. Each bacteria has an individual structure. We can manipulate the environment to make bacteria more vulnerable to the heating i.e. to change the structure of the bacteria. We can increase the duration of the heat exposure to make kill of the bacteria more effective.

How does mini uv sterilizer can kill bacteria in water?

In this article we will tell you in detail about mini uv sterilizer and the subtleties of their choice.

The sterilizing properties of ultraviolet radiation appeared in 1887. And people started using it in water disinfection processes from the first half of the 20th century. Nowadays, ultraviolet is used to disinfect drinking water, pool water, surfaces, air, etc.

What is a mini uv sterilizer water for?

Generally, bacteria can contaminate any source of water with bacteria. They can enter a well or shallow borehole, such as from a crack in your septic tank or from your neighbor's leaky sinkhole. Microorganisms reproduce very well in surface sources such as rivers, reservoirs, etc.

Most of these organisms are a direct threat to human health. When ingested, they lead to a large number of undesirable consequences. The ultraviolet sterilizer guarantees and effectively disinfects water. Moreover, it makes it suitable for drinking and other household / household purposes.

What is UV and how does it work?

Ultraviolet rays vary in wavelength. Some rays are beneficial for the body they contribute to the production of vitamin D3 in the human body. In mini uv sterilizer, a special lamp placed in a quartz casing emits light with a wavelength of 254 nanometers.

Light interacts with the DNA of microorganisms and destroys its structure. As we know from the school biology course: information about the structure of a cell is encrypted in DNA so that this cell can multiply. Ultraviolet light does not kill bacteria, but deprives them of their ability to multiply and thereby harm the human body.

Mini uv sterilizer t water consists of:

  • Shells (or so-called reaction chamber)
  • Quartz tube placed inside the chamber
  • Most ultraviolet lamp (emitting element)
  • Power supply

Some sterilizers may contain additional auxiliary parts, for example:

  • Intensity sensor to determine the efficiency of the device
  • A relief valve that prevents water heated from the lamp from entering the line
  • Flow sensor, etc.

Water enters the sterilizer chamber through one of its ports. Then the flow of water moves through a quartz tube into which a lamp is inserted. High-performance models of sterilizers can contain from two to several hundred emitters inside one reaction chamber. Moreover, it depends on the required performance, as well as on the source water. At the end of the process, treated water exits through another port of the sterilizer.

Ultraviolet light destroys pathogens of the following diseases:
  • Flu
  • Colibacillus
  • Typhoid and cholera
  • Hepatitis
  • Dysentery
  • Salmonellosis
  • Cysts of Giardia lamblia and Cryptosporidium and others.

The use of ultraviolet radiation in water treatment:

  1. In a water supply system where a carbon, polypropylene or any other cartridge, backfill filter or softener intalls. The filter filling or the surface of the cartridge is a favorable environment for the growth and reproduction of pathogenic microorganisms.
  2. In water supply systems using reverse osmosis installations. Such systems usually involve the use of a storage tank, and there is some possibility of water contamination. In this case, the mini uv sterilizer acts as a safety net.
  3. The water comes from a well or various surface sources.
  4. Aeration comes in the water treatment system. Abundant oxygen saturation of water significantly accelerates the growth of microorganisms.
  5. Hydrogen sulfide or ammonia is present in the feed water.

How to choose a water mini uv sterilizer?

The choice of a particular sterilizer model depends primarily on its performance. This indicator calculates on the basis of the radiation dose that water receives when passing through the sterilizer.

The reference dose is 40 mJ / cm². Leading brands claim the performance of their appliances based on this value. In practice, a dose of 30 mJ / cm² is safe (that is, guaranteed to give a result).

Unfortunately, not all companies consider it necessary to indicate at what radiation dose this or that performance declares.

Most of the Chinese manufacturers claim performance without reference to the dose of radiation, while the leaders in the mini uv sterilizer market claim several performances for the sterilizer. Moreover, it depends on the radiation dose.

For example, in the description of the VIQUA S5Q model, you can see the performance for three doses of radiation. Therefore, when buying a sterilizer, we advise you to first ask: for what dose of radiation is the performance of a particular model determined?

We can measure the performance indicator in m³ / hour. When choosing, be guided by the fact that one crane has a throughput of 300 l / h. That is, if we need a sterilizer for a shower combination (hot / cold water) + a kitchen tap (hot / cold water), a model with a capacity of 1.2 m³ / hour will do.

If the water is under high contamination in the water treatment system, we recommend using a mini uv sterilizer with a capacity margin.

Ultraviolet water mini uv sterilizer

We can use UV sterilizers both as a main cleaner and as an additional one. An ultraviolet sterilizer is a flask with a quartz lamp with sensors inside. The service life of these systems reaches 18 months the device does not require additional equipment and purchase of auxiliary substances.

The system is unpretentious in operation in case of malfunction, it will give a signal let’s note the special advantages of the ultraviolet water sterilizer:

  • High degree of water disinfection
  • Low price of the device
  • Wide range of quartz tube lamps
  • Anti-corrosion coating
  • Safe operation

In our company you can buy an ultraviolet sterilizer of various parameters. For efficiency, we install it immediately before the water supply: this protects against re-contamination of H2O.

The disinfection system neutralizes E. coli, influenza viruses, hepatitis, typhoid and cholera pathogens, salmonella and other pathogens. Ultraviolet water sterilizers are most often used as the final stage of purification.

Is mini uv sterilizer environment friendly?

Mini uv sterilizer gives a very environmentally friendly and effective disinfection method. We use it not only in apartments, but also in hospitals, enterprises, and offices. The favorable price for an ultraviolet sterilizer makes the disinfection system even more in demand.

Water disinfection with ultraviolet devices has some advantages over traditional water disinfection methods:

  • Provides instant destruction of bacteria and viruses by 99.9%.
  • Does not require the use of reagents.
  • There is no need for preparation and storage of chemicals when servicing the unit.
  • Compared to chlorination and ozonation, ultraviolet radiation is the most harmless to consumers and the environment.
  • Operation of the unit does not require additional equipment and the presence of maintenance personnel.
  • In case of lamp damage (failure), the control unit will beep. Therefore, you can always replace a damaged lamp on time.


Since covid 19 is spreading very fast, you need to stay safe from bacteria. For this purpose, it is necessary to buy mini uv sterilizer. Moreover, it is quite affordable but can kill 99% germs.

Germicidal Efficacy and Mammalian Skin Safety of 222-nm UV Light

We have previously shown that 207-nm ultraviolet (UV) light has similar antimicrobial properties as typical germicidal UV light (254 nm), but without inducing mammalian skin damage. The biophysical rationale is based on the limited penetration distance of 207-nm light in biological samples (e.g. stratum corneum) compared with that of 254-nm light. Here we extended our previous studies to 222-nm light and tested the hypothesis that there exists a narrow wavelength window in the far-UVC region, from around 200-222 nm, which is significantly harmful to bacteria, but without damaging cells in tissues. We used a krypton-chlorine (Kr-Cl) excimer lamp that produces 222-nm UV light with a bandpass filter to remove the lower- and higher-wavelength components. Relative to respective controls, we measured: 1. in vitro killing of methicillin-resistant Staphylococcus aureus (MRSA) as a function of UV fluence 2. yields of the main UV-associated premutagenic DNA lesions (cyclobutane pyrimidine dimers and 6-4 photoproducts) in a 3D human skin tissue model in vitro 3. eight cellular and molecular skin damage endpoints in exposed hairless mice in vivo. Comparisons were made with results from a conventional 254-nm UV germicidal lamp used as positive control. We found that 222-nm light kills MRSA efficiently but, unlike conventional germicidal UV lamps (254 nm), it produces almost no premutagenic UV-associated DNA lesions in a 3D human skin model and it is not cytotoxic to exposed mammalian skin. As predicted by biophysical considerations and in agreement with our previous findings, far-UVC light in the range of 200-222 nm kills bacteria efficiently regardless of their drug-resistant proficiency, but without the skin damaging effects associated with conventional germicidal UV exposure.


Nonfiltered and filtered measured emission…

Nonfiltered and filtered measured emission spectra from a Kr-Cl excimer lamp (main peak…

Bacterial cell killing induced by…

Bacterial cell killing induced by 222- and 254-nm UV light. Killing of MRSA…

Premutagenic skin DNA lesion yields…

Premutagenic skin DNA lesion yields induced by 222- and 254-nm UV light. Yields…

Epidermal thickness and keratinocyte proliferation…

Epidermal thickness and keratinocyte proliferation in mouse skin exposed to UVC light. Panel…

UVC-induced premutagenic DNA lesions in…

UVC-induced premutagenic DNA lesions in mouse skin. Panel A: Representative cross-sectional images of…

UVC-induced inflammation in mouse skin.…

UVC-induced inflammation in mouse skin. Density of (panel A) mast cells and (panel…

Tissue differentiation in UVC-exposed mouse…

Tissue differentiation in UVC-exposed mouse skin. Representative cross-sectional images of mouse dorsal epidermis…

Materials and methods

Effects of UVA light on common opportunistic microbes in culture

Bacterial and yeast preparations.

Bacteria and yeast were grown in appropriate liquid culture media and conditions (detailed in S1 Table). Primary cultures were used to inoculate solid microbial agar and isolate single colony forming units (CFU). Liquid cultures were prepared from a single CFU of each microbe to guarantee purity. Cultures were incubated (S1 Table) until they reached the McFarland standard of 0.5 [12] and 1000 μL of the liquid culture was transferred into each of two 1.7 mL micro-centrifuge sterile tubes. A 100 μL aliquot from each tube was serially diluted and plated on solid microbial medium to determine baseline CFU/mL (S1 Table), and UVA light was applied to the remainder.

UVA light against bacteria and yeast.

UVA effects were assessed using both broad band (BB) and narrow band (NB) wavelength spectra. For BB assessments (peak wavelength

345nm), a mercury vapor lamp (Asahi Max 303, Asahi Spectra Co., Tokyo, Japan) was used to transmit light via a borosilicate rod etched with diluted sulfuric acid, sodium bifluoride, barium sulfate and ammonium bifluoride (Armour, NJ). For NB experiments, an array of LEDs (peak wavelength 343±3nm, with full width at half maximum of 5nm) mounted on an aluminum heatsink (Seoul Viosys, Gyeonggi-Do, South Korea) (S1 Fig) was used. Wavelengths were confirmed by spectrometry (Flame UV-VIS, Ocean Optics, FL) and UV meters (SDL470 and UV510 UV, Extech, NH) (S1 Fig).

For the BB-UVA experiments, the sterilized rod was placed through the caps of 1.7mL tubes. An identical unlit rod was placed into control tubes. After incubation, CFU/mL were determined by serial dilutions of aliquots and measured using a Scan 300 Automatic Colony Counter (Interscience, Woburn, MA). This process was repeated at 20 and 40 minutes.

For the NB-UVA experiments, the LED array was placed 1cm from the surface of a culture plated with E. coli GFP, and illuminated (2000 μW/cm 2 at the plate). In separate experiments, we exposed liquid cultures of 10 6 CFU/mL of E. coli and P. aeruginosa to NB-UVA at intensities of 500, 1000, 2000 and 3000 μW/cm 2 for 20 and 40 minutes.

Safety of NB-UVA on human cells

HeLa cells (ATCC® CCL-2™) were added to DMEM cell culture medium (Gibco, Waltham, MA) plus 10% Bovine serum (Omega Scientific, Tarzana, CA) and 1x Antibiotic-Antimycotic (100x, Gibco) in 60x15mm standard tissue culture dishes (Corning, NY) and incubated at 37ºC (5% CO2) for 24 hours to achieve 1,000,000 to 1,800,000 cells per plate. Cells were exposed to NB-UVA (2000 μW/cm 2 ) for 0 (control), 10, or 20min. After 24hr of further incubation at 37°C (5% CO2), cells were removed using 0.05% Trypsin-EDTA (1x) (Gibco), stained with Trypan Blue 0.4% (1:1) (Gibco) to define live/dead cells [13, 14] and quantitated using an automated cell counter (Biorad T20, Hercules, CA). HeLa cells were also exposed to higher NB-UVA at 5000 μW/cm 2 for 20 minutes and quantitated after 24hr of incubation at 37ºC (5% CO2).

Effects of UVA were also tested on human alveolar (ATCC A549) and primary ciliated tracheal epithelial cells (HTEpC, Lot 446Z036.8, Male, age 50, Caucasian) (PromoCell, Heidelberg, Germany). Cells were plated and grown for 48h in DMEM (Alveolar cell) and Airway Growth Medium (HTEpC) (PromoCell) at 37ºC (5% CO2). Subsequently, cells were exposed to UVA (2000 μW/cm 2 ) for 0 (control) or 20 minutes (treated), and cell counts were obtained after 24hr at 37ºC (5% CO2) by automated cell counter (Biorad T20).

Levels of 8-hydroxy-2’-deoxyguanosineis (8-OHdG), a sensitive marker of oxidative DNA damage and oxidative stress [15, 16], were analyzed in the DNA of NB-UVA-treated cells. DNA was extracted using AllPrep DNA/RNA/Protein Mini Kits (Qiagen). 8-OHdG levels were detected using EpiQuik™ 8-OHdG DNA Damage Quantification Direct Kits (Epigentek, Farmingdale, NY). For optimal quantification, the input DNA amount was 300 ng, as the basal 8-OHdG is generally less than 0.01% of total DNA (Epigentek). A standard curve of 8-OHdG ranging from 5 to 200 pg was used to determine the concentration of 8-OHdG in the samples.

Effects of NB-UVA light on human cells transfected with group B coxsackievirus

NB-UVA exposure of HeLa cells transfected with group B coxsackievirus.

HeLa cells were cultured (12 plates, mean 253,000 cells/plate) for 24hr at 37ºC (5% CO2). Recombinant coxsackievirus B (pMKS1) expressing an enhanced green fluorescent protein (EGFP-CVB) was prepared as previously described [17] half were exposed to NB-UVA (2000 μW/cm 2 ) for 20min while the other half were not exposed. HeLa cells were then transfected with NB-UVA-exposed or NB-UVA-unexposed virus (multiplicity of infection (MOI) = 0.1). Coxsackievirus is considered highly lytic [18]. After 6hrs, supernatant was removed, and cells were washed twice with 1x sterile PBS (pH = 7.0). New DMEM media was added and cells were incubated at 37ºC (5% CO2). Dead cells in the supernatant (floating cells) were collected and quantified 24hrs later using an automated cell counter (Biorad T20). Six plates (3 NB-UVA-exposed and 3 unexposed) were assessed for live cells. Of the remaining six plates, the 3 plates transfected with NB-UVA-exposed virus were exposed to an additional 20min of NB-UVA (2000 μW/cm 2 ). After 24hrs at 37ºC (5% CO2), imaging was performed using a BZ-9000 BioRevo (Keyence Corp., Itasca, IL). Dead and live cells were determined by the Trypan Blue 0.4% (1:1)(Gibco) method and counts were obtained using an automated cell counter (Biorad T20).

HeLa cell pre-treatment with NB-UVA and group B coxsackievirus transfection.

HeLa cells were plated and incubated in DMEM for 24 hours at 37ºC (5% CO2). Plates were divided into unexposed controls (n = 3) and HeLa cells exposed to NB-UVA (2000 μW/cm 2 ) for 20min (n = 3). After 24hrs at 37ºC (5% CO2), all plates were transfected with EGFP-CVB (MOI = 0.1). At 24hrs post-transfection, cells were counted using an automated cell counter (Biorad T20).

Pre-treatment of group B coxsackievirus with NB-UVA and HeLa cell transfection.

HeLa cells were cultured for 24hrs at 37ºC (5% CO2) and transfected with EGFP-CVB (MOI = 0.1). Prior to transfection, half of the EGFP-CVB aliquots were exposed to NB-UVA (2000 μW/cm 2 ) and the other half remained unexposed. After 24hrs at 37ºC (5% CO2), imaging was performed and HeLa cell counts were using an automated cell counter (Biorad T20).

Effects of repeated exposure of NB-UVA on HeLa cells already transfected with group B coxsackievirus.

HeLa cells were plated and incubated at 37ºC (5% CO2) and at 24hrs, cells were divided into three groups: Group 1, cells transfected with EGFP-CVB (n = 3, MOI = 0.1), served as positive transfected controls. Group 2, HeLa cells transfected with EGFP-CVB (MOI = 0.1) exposed to NB-UVA (n = 3, 2000 μW/cm 2 for 20 min) and 6hrs later exposed again to NB-UVA (2000 μW/cm 2 ) for 20 minutes followed by 4 additional exposures (two 20-minute exposures on day 2, 8hrs apart, and two 20-minute exposures on day 3, 8hrs apart. Group 3, not transfected with EGFP-CVB but exposed to NB-UVA at the same time-points as Group 2 (n = 3) to assess UVA effects. In all experiments, imaging and cell counts were performed using an automated cell counter (Biorad T20).

NB-UVA exposure on alveolar (A549) cells already transfected with group B coxsackievirus.

Ideal timepoints of cell death from transfection were determined to be 24 hours in preliminary experiments with alveolar cells (results not shown). Alveolar cells were plated, incubated at 37ºC (5% CO2) and counted at 48hrs (n = 9, cell count of 754,000). Cells were then transfected with EGFP-CVB (n = 6, MOI = 0.1), and 24hrs later, plated cells were exposed to NB-UVA (2000 μW/cm 2 ) for 0 (control, n = 3) or 20 minutes (treated, n = 3). Exposure was repeated every 24hrs for three days, with imaging and cell counts performed at 96hrs post-transfection. Three control plates were not transfected and not exposed.

Preparation of coronavirus 229E.

Human coronavirus 229E (CoV-229E) (ATCC VR-740, ATCC) was overlain onto confluent MRC-5 human lung fibroblasts. CoV-229E is considered lytic [19]. Once cells exhibited

50% cytopathic effect, cells were trypsinized and the cell/media suspension was collected. The cell/media mixture underwent one rapid freeze/thaw cycle and was centrifuged at 1000x g for 10min to clarify the media. The virus in the supernatant was used for subsequent experiments. Equal volumes of the supernatant from the same culture containing the virus were used for transfection of primary human cells.

NB-UVA exposure of ciliated tracheal epithelial cells (HTEpC) transfected with CoV-229E.

HTEpC (135,000 cells) were plated into three groups. Group 1 was transfected with CoV-229E (n = 3, 50uL per plate). In group 2, prior to transfection, CoV-229E was exposed to NB-UVA (n = 3, 2000 μW/cm 2 ) for 20min. Group 3 was not exposed to NB-UVA or transfected (n = 3). After transfection, the cells were exposed to NB-UVA (4cm distance with 2000 μW/cm 2 at the plate surface) for 20min daily. Plates were imaged at 16, 36, 72, and 96hrs, cell viability (live/dead) counts were obtained at 72 and 96hrs post-transfection. Trypan Blue 0.4% (1:1) (Gibco) was used to determine live/dead cells and cell counts were obtained using an automated cell counter (Biorad T20, Hercules, CA). Cells were kept at 37ºC (5% CO2).

NB-UVA effects on CoV-229E and mitochondrial antiviral signaling protein (MAVS).

AllPrep DNA/RNA/Protein Mini Kits (Qiagen) were used to extract total protein from UVA-exposed and unexposed tracheal cells transfected with CoV-229E. Proteins were loaded into a Bolt 4–12% Bis-Tris gel (NW04122 Thermo Fisher) and transferred onto a Biotrace NT nitrocellulose membrane (27376–991, VWR). Total proteins were stained with Ponceau S solution (P7170, Sigma-Aldrich). The membrane was blocked in blocking solution (tris-buffered saline containing 3% bovine serum albumin (A7030, Sigma-Aldrich) and 0.1% Tween 20 (P1379, Sigma-Aldrich) (TBS-T) and incubated overnight at 4°C with either rabbit anti-coronavirus spike protein antibody (1:1000 PA5-81777, Thermo Fisher) or mouse anti-MAVS antibody (1:200 SC-166583, Santa Cruz Biotechnology) diluted in blocking solution. After washing in TBS-T, the membrane was then overlain with either horseradish peroxidase (HRP)-conjugated goat anti-rabbit IgG antibody (1:300 95058–734, VWR) or HRP-conjugated goat anti-mouse IgG antibody (1:300 5220–0286, SeraCare), washed in TBS-T, and exposed to enhanced chemiluminescence solution (RPN2235, GE Healthcare). Immunoreactive protein bands were imaged using a ChemiDoc Imaging System (Bio-Rad Laboratories, Hercules, CA).

In vivo effects of UVA

Animal preparation.

In vivo effects of UVA exposure on mammalian internal visceral cells were assessed using wildtype 129S6/SvEv mice (n = 20, female = 10) and BALB/cJ mice (n = 10, female = 5). Animals were anesthetized prior to UVA light treatment in a chamber containing isoflurane anesthetic gas (1–5%) mixed with oxygen, and maintained under sedation using a nose cone anesthesia (1–2% isoflurane) at one breath per second. Euthanasia was performed using C02 inhalation followed by cervical dislocation. All animal research was performed under a protocol approved by the Institutional Animal Care and Use Committee (IACUC) at Cedars-Sinai Medical Center, IACUC007304.

Exposure of colonic mucosa to UVA.

Under anesthesia, the borosilicate rod (OD = 4mm, length = 40mm) was introduced anally to the splenic flexure (S1C Fig). Five BALB/cJ mice underwent colonic BB-UVA exposure (2,000 μW/cm 2 ) for 30min, and 5 mice were treated with an unlit optic rod. In the second experiment, ten 129S6/SvEv mice underwent 20min daily colonic UVA exposure (3,000–3,500 μW/cm 2 ) for 2 two consecutive days, and 10 mice (male = 5) were treated with an unlit rod.

Endoscopic examination before and after UVA light therapy.

While anesthetized, a rigid pediatric cystoscope (Olympus A37027A) was used to assess the intestinal mucosa up to the splenic flexure before and after UVA exposure. All endoscopies were recorded and blindly interpreted by two gastroenterologists (JHP and SYK) with expertise in animal model endoscopies. Endoscopic appearances were analyzed based on perianal examination, transparency of the intestinal wall, mucosal bleeding, and focal lesions.

Tissue analysis.

At day 14, control and treated mice were euthanized, and swiss-roll preparations of the colon were performed as described [20]. The rolled colon was transferred to a tissue-processing/embedding cassette and placed in 10% buffered formalin overnight. Paraffin sections of the colon were cut, stained with hematoxylin and eosin (H&E), and assessed by a blinded pathologist (SS).

Statistical analysis

Descriptive statistics were calculated to describe the bacteria counts and colony sizes and UVA exposure with varying intensities. Each UVA group included 4 measurements and the mean of the measurements at each time point was reported. To assess the effect of UVA light on bacteria, yeast, and virus, the measurements of bacteria and human cells in UVA exposed and control groups were compared with t-test. Bivariate analyses were used to further determine the association between UVA exposure and viral effect on three human cell types. The continuous variables were compared with t-test. The statistical significance was defined as p < 0.05. Analyses were performed using GraphPAD Prism 7 (GraphPad, San Diego, CA).

Answer to Question #11911 Submitted to "Ask the Experts"

The following question was answered by an expert in the appropriate field:

I have seen ultraviolet (UV) lights that kill bacteria in fish tanks. The light does not touch the water but shines down into the tank or sometimes is submerged. I am in ninth grade biology and writing a paper on UV-C light. My question is: If a UV-C light shines down into a container of water from above, could a human safely drink from the container? Or if a waterproof UV-C light is submerged in a water glass, could a human drink from it? Theoretically would there be any danger in either instance?

The short answer to your question is that the water would be safe to drink.

In general, there are many forms of energy, some we can see (visible light), some we cook with (microwaves), some we heat with (infrared), and some we cannot completely see (UV). UV light is further divided into three types, abbreviated UV-A, UV-B, and UV-C.

UV-A and UV-B lights are used mostly for plant grow lights and tanning beds (note that we do not recommend that tanning beds be used by individuals). UV-C light is the most energetic of these forms of UV light and is invisible to humans. The reason you see the bluish glow from these types of bulbs is a function of the manufacturing and physical characteristics of the quartz glass forming the bulb. Under no circumstances should you stare at a UV-C light source for any amount of time.

When UV-C light shines on water or if the bulb is immersed in the water, some of the light penetrates the water and is absorbed by germs, such as bacteria and viruses, in the water. When UV-C light is absorbed by these germs, they are killed, sterilizing the water.

The water itself is not harmed by the UV-C, and the UV-C light does not remain in the water. When you drink the water, there is no UV-C in the water. In fact, some public water suppliers use UV-C light to sterilize their drinking water, and you can also purchase UV-C light systems to sterilize your own home's water or air. There are also small portable UV-C devices used by hikers and backpackers to sterilize their water when hiking. One example is the SteriPEN. These devices work well but be sure to have extra batteries!

In summary, shining a UV-C light source on water, or placing a UV-C bulb in water, does not harm the water so the water is safe to drink.

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UVC, Watts, Microwatts

UVC, Watts, Microwatts, Joules, & Light Penetration

This article/post is intended to give some basic understanding between the relationship of watts, microwatts, joules of UVC energy and how this translates to UV Sterilizer effectiveness.

Please keep in mind that the diagram in this article is based on air penetration, so some extrapolation is necessary for use in water applications (which is the primary intention of this article, although the principles apply to UVC air sterilization devices as well)
UVC Air Sterilization Devices

What is a Watt/Microwatt?

One Joule of energy = 1,000 milliWatt seconds = 1,000,000 microWatt seconds
One joule is the amount of energy required to perform the following actions:

• The work done by a force of one newton traveling through a distance of one meter (a newton is the unit of force equal to the amount of force required to accelerate a mass of one kilogram at a rate of one meter per second per second)
• The work required to move an electric charge of one coulomb* (the amount of electric charge transported by a current of 1 ampere in 1 second) through an electrical potential difference of one volt or one coulomb volt, with the symbol C•V
• The work done to produce power of one watt continuously for one second or one watt second (compare kilowatt hour), with the symbol W•s. Thus a kilowatt hour is 3,600,000 joules or 3.6 megajoules
• The kinetic energy of a 2 kg mass moving at a velocity of 1 m/s. The energy is linear in the mass but quadratic in the velocity, being given by E = ½mv²
we measure UV-C intensity in Micro-Watts that strike one square centimeter of surface area.
Reference: What is a coulomb?

UVC Penetration
A quote from an advanced sterilization article:
UV Sterilization How a UV Sterilizer Works

"The emission or light intensity of a UVC germicidal light bulb is usually expressed in a term called "microwatts per square centimeter" (Mw/cm2). The maximum intensity provided by a single UV-C Bulb is at its surface.
So, if we calculate the surface area of the UVC lamp and only use that area which effectively emits UVC light rays, the effective area of UVC transmission will be established. Basic mathematics will show that the surface area of a cylindrical tube is ‘pie’ D L.

Next extrapolate this effective area of UVC transmission as having a screen with squares 1 centimeter in size. Each of these cm2 areas now, for measurement purposes, emits a UVC lamp intensity measured in microwatts, in other words the term microwatts/cm2. UVC light intensity decreasingly varies as the distance from the UVC light increases.

Put more simply (a non scientific analogy) The amount of wattage will also increase penetration, as a higher watt UV-C bulb will generally have more Mw/cm2."
See this product link for high output Straight Tube UV Bulbs:
Premium HO Straight Tube UV Lamps

"In my own experiments I have used 15 watt and 25 watt UVC bulbs in exactly the same unit (both were 18”), if wattage were only considered there would be a 60% increase in effectiveness, however I only observed a about a 25% increase.
When I used a 30 Watt UVC bulb in a unit with over twice the exposure as the 15 Watt, the kill rate more than doubled. From my experience, if you increase wattage (and Mw/cm2) you need to also increase the volume of water to maximize the higher watt bulb.
Experiments can also be safely conducted with standard household light bulbs to correlate penetration. For this start with a 7 watt clear bulb (such as a Christmas bulb) and place varying thicknesses of paper/ cardboard in front of the bulb and measure when penetration stops. Continue this with higher and higher wattage bulbs."

The Diagram to the left can give a rough comparison of distance as per UVC energy as expressed by MW/cm2 in Air transmission.
The dose applied by an UV-C lamp installation is a function of the lamp output, the intensity factor, and time. As an equation Intensity x Exposure time= microwatt seconds/cm2.

As an example, a 9 watt UVC lamp at one inch from the lamp is found by this formula:
9 x 127 = 1143 mW/cm2.
Since many bacteria such as Vibrio require a UVC exposure of 6500 mW/cm2 or more, this means an exposure time of 5.68 seconds is required to kill this pathogen

Now let me point out that even though I have published this diagram, please use this as a rough guide only, as I have found inaccuracies in it. To be more blunt I have found the distance, wattage, and flow rate to be the MOST IMPORTANT factors in determining exposure/effectiveness. This diagram is STATIC and does NOT take into consideration the dynamics of UVC radiation penetration for which I have yet to find a good formula to demonstrate this (even in University studies).

What is often missing in any equations I have seen is the dynamics of water flow geometry, actual water flow, and wattage. The bottom line is to use this table and others you might find elsewhere with “a grain of salt” noting that these are static and even then are flawed when true output via wattage is taken into consideration.

Further Reading, References, Product Resources:

UV Bulb Replacement Lamps
The very best UV Replacement Lamps/Bulbs at competitive prices!

WEBINAR: Science Behind UVC Sterilizing Lights

Get an in-depth look at how UVC sterilization germicidal lights can be used for disinfection and what that means to you. In this video you will see:

• How UVC lights fight germs including coronavirus
• Effects of UVC light and safety considerations
• Top 6 industries ideal for UVC disinfection deployment
• Independent lab reports on SARIN UVC devices

Dr. Takrima Sadikot, PhD Molecular Biology & Biochemistry Associate Professor Washburn University
Inayat Noormohmad, President/Founder SARIN Energy

Frequently Asked Questions

Please click on any of the questions below for answers to frequently asked questions about UVC sterilization. Of course we also welcome phone calls and e-mails regarding these, and any other questions you may have. Please visit the contact page for individual numbers and addresses of American Ultraviolet associates in your area.

Q: Can I put UVC fixtures in my home?

Yes - ultraviolet fixtures from American Ultraviolet have been safely used in homes, as well as in hospitals, laboratories, clean rooms, doctors&Prime offices, commercial buildings, food processing plants and other commercial and residential environments throughout the world - any place a concern for clean air exists.

Q: Do germicidal lamps kill viruses?

Yes -germicidal UVC lamps kill up to 99.9% of most viruses, airborne bacteria and mold spores.

Q: What is UVGI and how does it work?

Ultraviolet (UV) energy is a portion of the electromagnetic spectrum. The electromagnetic spectrum is the range of all types of known electromagnetic energy (also known as electromagnetic radiation). The term radiation simply means energy that travels and spreads out as it travels. Read Full Answer.

Q: Can Ultraviolet Light Kill Coronavirus (Caution Required)?

Answer provided by By Naomi Millán, Senior editor of Building Operating Management (May 2020). Read Full Answer.

Q: Will germicidal UV take care of mold?

Yes. Germicidal UVC lamps will kill up to 99.9% of mold and help prevent future mold growth.

Q: How often do the lamps need to be replaced?

Germicidal UVC lamps from American Ultraviolet are good for approximately 17,000 hours (two years) of continuous use, with only 20% decrease in output over the two years.

Q: Should UVC lamps be cleaned?

Yes - depending on the surrounding environment, UVC lamps should be checked periodically (approximately every three months), and can be cleaned with a dry cotton cloth or paper towel. Wear rubber gloves and clean with alcohol only. This will also help maximize lamp life.

Q: How much intensity do I need to kill certain organisms?

The exposure of germicidal ultraviolet is the product of time and intensity. High intensities for a short period and low intensities for a long period are fundamentally equal in lethal action on bacteria. The inverse square law applies to germicidal ultraviolet as it does to light: the killing power decreases as the distance from the lamps increases. The average bacterium will be killed in ten seconds at a distance of six inches from the lamp in an American Ultraviolet Germicidal Fixture.

Q: Can germicidal lamps be turned on and off continuously?

There are three common types of germicidal UVC lamps:

Q: How do germicidal lamps kill?

Ultraviolet light in the germicidal wavelength - 185-254 nanometers - renders the organisms sterile. When organisms can no longer reproduce, they die. To learn more please visit the Basics of UVC section within the Overview section.

Q: How hot do the lamps get?

Germicidal UVC lamps do not produce much heat - about the same as fluorescent lamps.

Q: To be effective, how close to the surface do the lamps need to be?

The exposure of germicidal ultraviolet is the product of time and intensity. High intensities for a short period and low intensities for a long period are fundamentally equal in lethal action on bacteria. The inverse square law applies to germicidal ultraviolet as it does to light: the killing power decreases as the distance from the lamps increases. The average bacterium will be killed in ten seconds at a distance of six inches from the lamp in an American Ultraviolet Germicidal Fixture.

Q: Do I need ozone-producing lamps?

Some Germicidal UVC lamps produce ozone. Whether or not you need ozone-producing lamps depends on your particular application. Most of the time you do not need ozone, unless there are shaded areas that the UVC light cannot reach, and the space will not be occupied by people. Ozone can travel in the air to where UVC cannot reach directly, but should not be used in spaces where people will be present, without proper PPE. American Ultraviolet only uses ozone-producing germicidal UVC lamps when specifically required by unique applications, or customer requirements. American Ultraviolet standard UVC lamps do not produce any ozone. Our lamps only emit from 240NM and up.

Q: When do I need to use ozone-producing lamps?

Certain germicidal UVC lamps can generate energy at 185 nanometers, as well as 254nm. The 185nm wavelength produces abundant amounts of ozone in air. Ozone is an extremely active oxidizer and destroys microorganisms on contact. Ozone also acts as a deodorizer. Another advantage is that it can be carried by air into places that UVC radiation cannot reach directly. American Ultraviolet standard UVC lamps do not produce any ozone. Our lamps only emit from 240NM and up.

Q: What damage will the lamps do to me?

Prolonged, direct exposure to UVC light can cause temporary skin redness and eye irritation, but does not cause skin cancer or cataracts. American Ultraviolet systems are designed with safety in mind and, when properly installed by a professional contractor, do not allow exposure to ultraviolet irradiation and allow for safe operation and maintenance. If you are exposed to direct germicidal light, it can burn the top surface of your skin. If your eyes are exposed, it would be similar to a "welder's flash", and your eyes can feel dry or gritty. At no time do germicidal lamps cause any permanent damage.

Q: What effects does UV light have on surrounding materials?

Long-term exposure of germicidal UVC light to plastics will shorten the shelf life of the plastic by approximately 10%. Example: If the plastic would normally last about ten years, and it's exposed to germicidal UVC light the entire time, it would probably need to be replaced in 9 years. Plant life may be damaged by direct, or reflected, germicidal ultraviolet rays. Transient dyes and colors may be faded from prolonged exposure to ultraviolet rays.

Q: Can germicidal UVC penetrate surfaces or substances?

No - germicidal UVC sterilizes only what it comes in contact with. If you have a room sterilizer, such as one of our TB models, and there are light fixtures or fans hanging from the ceiling, the UVC light will stop when it hits these fixtures. This may require additional fixtures placed strategically in the room to ensure complete coverage.

Q: How do you determine the square footage that one germicidal UVC lamp will cover?

This is determined by the wattage of the lamp. Example: A 15-watt lamp will cover approximately 100 square feet a 30-watt lamp will cover approximately 200 square feet.

Q: Do the lamps need a ballast to work?

Yes - a germicidal lamp is one part of a system, and the system cannot be fully defined and optimized unless the lamp and ballast combination is determined. It is the interaction of the lamp and ballast that is the true determinant of system performance.

Q: How are UVC lamps used to disinfect the air?

Germicidal UVC lamps can be used in ceiling fixtures suspended above the people in a room, or within air ducts of re-circulating systems. The first method is called Upper Air Irradiation. The fixtures are shielded on the bottom so that the radiation is directed only up toward the ceiling and out the sides. These upper-air germicidal fixtures are mounted at least 7ft. above the floor so that people will not bump into them or look directly at the lamps.

The second method of air disinfection uses UVC lamps placed inside the ventilation system ducts. If a ceiling is too low for an upper-air irradiation fixture, this type of an in-duct germicidal fixture can be used. Also, because people are not exposed to the UVC radiation, very high levels can be used inside the ducts.

Q: Why doesn't the government, or insurance companies, reimburse for UVC fixtures?

Germicidal lamps were not placed on the Medicare or Medicaid list when the government requested it in the early 60s, because tuberculosis was not a major issue at that time. Because it's not on these lists, the government, and insurance companies, will not reimburse individuals for purchasing a UVC system.

Q: What safety precautions should be taken when using germicidal UVC?

In personal protection applications (the use of lamps for room irradiation in homes, schools, offices, etc.), indirect fixtures such as TB and Corner Mount fixtures are mounted above eye level. Only the upper air is irradiated and persons or animals occupying the area receive no direct exposure. Direct ultraviolet irradiations, such as American Ultraviolet's Utility Fixtures or Deluxe Surface Mounted Fixtures, irradiate the air in the entire room. In such installations, personnel should be protected by wearing either goggles or face shields, such as American Ultraviolet's Ultra-Spec 100 Safety Goggles and Ultra-Shield Face Shields designed for ultraviolet exposure, and by covering as much skin as possible with clothing or sun block.

UV light could reduce hospital-acquired infections

A new study shows that ultraviolet disinfection technology eliminates up to 97.7 percent of pathogens in the operating room. Using this light wavelength might help defeat superbugs.

Could light help lower the risk of dangerous infections in hospitals?

The study, published in theAmerican Journal of Infection Control, examined the effects of a type of ultraviolet (UV) light technology called PurpleSun.

This technology is designed for use in operating rooms, patient rooms, and other healthcare settings.

The study shows that the device can help reduce the risk of infections acquired in the hospital.

These infections cost billions of dollars, and some estimates state that they cause almost100,000 deaths each year in the United States.

In the current study, researchers used over 3,000 microbiological samples from 100 different surgical cases at three hospitals in the New York area.

Researchers then looked at how well the PurpleSun technology worked. They found that it eliminated most pathogens.

PurpleSun is unique, as it has foldable partitions, which means that it can surround equipment on all sides, and its light hits five surface points. It also uses high levels of UV intensity in 90-second intervals for optimum effect.

“[UV] light technology will not replace manual cleaning and disinfection with chemicals, but it has a place in healthcare settings,” says Donna Armellino, lead author of the study and vice president of infection prevention at Northwell Health. She explains:

“ This technology can optimize environmental cleanliness, resulting in decreased pathogens that could potentially cause infection.”

Donna Armellino