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Type of ultraviolet light most effective at killing coronavirus is also the safest to use around people

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Type of ultraviolet light most effective at killing coronavirus is also the safest to use around people

Scientists have long known that ultraviolet light can kill pathogens on surfaces and in air and waterUV robots are used to disinfect empty hospital rooms, buses and trains; UV bulbs in HVAC systems eliminate pathogens in building air; and UV lamps kill bugs in drinking water.

Perhaps you have seen UV wands, UV LEDs and UV air purifiers advertised as silver bullets to protect against the coronavirus. While decades of research have looked at the ability of UV light to kill many pathogens, there are no set standards for UV disinfection products with regard to the coronavirus. These products may work to kill SARS-CoV-2, the virus that causes COVID-19, but they also may not.

I am an environmental engineer and expert in UV disinfection. In May 2021, my colleagues and I set out to accurately test various UV systems and see which was the most effective at killing off – or inactivating – SARS-CoV-2.

David Herring, NASA via WikimediaCommons

When UV light enters a cell, it breaks the bonds that hold DNA or RNA together.

How does UV light kill a virus?

Light is categorized by wavelength – the distance between peaks of a wave of light – and is measured in nanometers. UV wavelengths range from 100 to 400 nanometers – shorter in wavelength than the violet hues in visible light – and are invisible to the human eye. As wavelength shortens, photons of light contain higher amounts of energy.

Different wavelengths of UV light work better than others for inactivating viruses, and this depends on how well the wavelengths are absorbed by the virus’s DNA or RNA. When UV light gets absorbed, the photons of light transfer their energy to and damage the chemical bonds of the genetic material. The virus is then unable to replicate or cause an infection. Researchers have also shown the proteins that viruses use to attach to a host cell and initiate infection – like the spike proteins on a coronavirus – are also vulnerable to UV light.

The dose of light matters too. Light can vary in intensity – bright light is more intense, and there is more energy in it than in dim light. Being exposed to a bright light for a short time can produce the same UV dose as being exposed to a dim light for a longer period. You need to know the right dose that can kill coronavirus particles at each UV wavelength.

A sunburned man sits on a beach

Ian Hooton, Science Photo Library via Getty Images

Sunburns are caused by UV light damaging skin cells.

Making ultraviolet lights safe for people

Traditional UV systems use wavelengths at or around 254 nanometers. At these wavelengths the light is dangerous to human skin and eyes, even at low doses. Sunlight includes UV light near these wavelengths; anyone who has ever gotten a bad sunburn knows just how dangerous UV light can be.

However, recent research has shown that at certain UV wavelengths – specifically below 230 nanometers – the high-energy photons are absorbed by the top layers of dead skin cells and don’t penetrate into the active skin layers where damage can occur. Similarly, the tear layer around eyes also blocks out these germicidal UV rays.

This means that at wavelengths of UV light below 230 nanometers, people can move around more freely while the air around them is being disinfected in real time.

UV lamp test diagram

Karl Linden, CC BY-ND

Researchers used this setup to test multiple different UV lights at various doses to see what it took to kill SARS-CoV-2.

Testing different wavelengths

My colleagues and I tested five commonly used UV wavelengths to see which work best to inactivate SARS-CoV-2. Specifically, we tested how large a dose is needed to kill 90% to 99.9% of the viral particles present.

We ran these tests in a biosafety level three facility at the University of Arizona that is built to handle lethal pathogens. There we tested numerous lights across the UV spectrum, including UV LEDs that emit light at 270 and 282 nanometers, traditional UV tube lamps at 254 nanometers and a newer technology called an excited dimer, or excimer, UV source at 222 nanometers.

To test each device we spiked a sample of water with millions of SARS-CoV-2 viruses and coated a petri dish with a thin layer of this mixture. We then shined UV light on the petri dish until we achieved a specific dose. Finally we examined the viral particles to see if they could still infect human cells in culture. If the viruses could infect the cells, the dose was not high enough. If the viruses did not cause an infection, the UV source at that dose had successfully killed the pathogen. We carefully repeated this process for a range of UV doses using the five different UV devices.

While all of the wavelengths we tested can inactivate SARS-CoV-2 at very low doses, the ones that required the lowest dose were the systems that emit UV light at a wavelength of 222 nanometers. In our experiment, it took a dose of less than 2 millijoules of energy per square centimeter to kill 99.9% of viral particles. This translates to needing about 20 seconds to disinfect a space receiving a low intensity of short wavelength UV light, similar to that used in our test.

These 222-nanometer systems are almost twice as effective as conventional UV tube lamps, which are often used in ultraviolet disinfecting systems. But importantly, the winning lamp also happens to be the safest for humans, too. At the same UV light intensity it takes to kill 99.9% of SARS-CoV-2 in 20 seconds, a person could be safely exposed to 222-nanometer light for up to one hour and 20 minutes.

What this means is that widely available types of UV lamp lights can be used to safely knock down levels of the coronavirus with people present.

Better use of existing tech

Many places or organizations – ranging from the U.S. Air Force to the Space Needle in Seattle to Boeing – are already using or investigating ways to use UV light in the 222 nanometer range to protect public health.

I believe that our findings are important because they quantify the exact doses needed to achieve various levels of SARS-CoV-2 control, whether that be killing 90% or 99.9% of viral particles.

Imagine coffee shops, grocery stores, school classrooms, restaurants and concert venues now made safe by this technology. And this is not a solution for just SARS-CoV-2. These technologies could help protect human health in public spaces in future times of crisis, but also during times of relative normalcy, by reducing exposure to everyday viral and bacterial threats.


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Patriots-Bills inactives: Kyle Dugger out, all 8 questionable Pats active in Buffalo

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Patriots-Bills inactives: Kyle Dugger out, all 8 questionable Pats active in Buffalo

ORCHARD PARK, N.Y. — Questionable? Ha.

For the third straight week, every Patriot listed as questionable on the team’s injury report is active. Starting right tackle Trent Brown and defensive tackle Christian Barmore were among the eight supposed question marks, but both will play in windy Buffalo. Backup quarterback Jarrett Stidham, cornerback Shaun Wade and linebacker Jahlani Tavai are the Pats’ most notable inactives.

The Patriots also activated linebacker Jamie Collins off injured reserve and elevated defensive lineman Daniel Ekulale and safety Sean Davis from the practice squad.  They are without starting safety Kyle Dugger, who remains on COVID-19 reserve.

For the Bills, run-stuffing defensive tackle Star Lotulelei is active after returning from injured reserve. Wide receivers WR Marquez Stevenson and Isaiah McKenzie are both out.

Both teams’ complete inactive lists are below.

PATRIOTS

QB Jarrett Stidham

LB Ronnie Perkins

TE Devin Asiasi

OL Yasir Durant

BILLS

WR Marquez Stevenson

WR Isaiah McKenzie

FB Reggie Gilliam

OL Jamil Douglas

DT Vernon Butler

DE Efe Obada

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Parents, teachers push for prompt transition to elected Boston school committee

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Parents, teachers push for prompt transition to elected Boston school committee

Boston Public School parents, teachers and graduates called on city councilors to shift the mayor-appointed school committee to an elected body in a public hearing Monday, demanding follow-through on the resounding 79% memorandum voters passed on the identical ballot question in November’s election.

“With this appointed school system, I feel that my voice goes unheard,” said BPS parent Suleika Soto, summarizing what many petitioners highlighted: a lack of both accountability and communication from the current structure of the committee.

“We, the students, families, and educators are not the constituents of the Boston School Committee,” said BPS teacher Neema Avashia. “We find ourselves begging to be heard.”

The Boston School Committee is responsible for managing Boston Pubic Schools’ annual operating budget, hiring and overseeing the superintendent, and regulating policies and practices within city schools. Members of the 13-person council had been elected by city residents from 1982 until 1989, when voters decided to transition the council to a mayor-appointed body.

Question 3 on November’s ballot to restore the group back to an elected body got overwhelming support from voters, with more than 99,000 votes cast in favor of the change.

“What we have to do now is listen to what people have said and how loud they’ve said it,” said John Nucci, who served four years as the president of the Boston School Committee during its most recent era as an elected body.

The City Council provided an early draft of what the transition back to an elected body could look like. The first step, in January 2022, would maintain eight appointed members and add one member elected through the BPS student population. By January 2024, the body would become a hybrid mix of seven appointed members, one student-elected member and three at-large elected members. Finally, by 2026, the entire 13-person committee would consist of elected members.

But the question of how those members are elected is one of many details councilors will try to hammer out through future hearings and meetings. One topic of debate is whether the majority of committee members should represent specific districts, or act as at-large officials, representing the city as a whole.

Newly elected city councilor and former BPS teacher Erin Murphy suggested at least nine of the members should represent specific districts, fearing “many voices would be left out” if they don’t have specific representation.

Pam Kocher, president of the Boston Municipal Research Bureau — a neutral party on the issue — cautioned that an elected governing body is not a guarantee for a representative body.

“Elections can reward the loudest voices and those with the most resources,” she said.

Councilors assured attendees this meeting will be the first of several on the issue before action.

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Maguire: Stand up for Boston students – be a substitute teacher

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Maguire: Stand up for Boston students – be a substitute teacher

I invite you to join me — if only for a day — in the best job a person could have: teaching. This year we are back to in-person learning, a goal for which the teachers have long strived. However, many teachers with underlying health concerns took leaves of absence. Some teachers in their 60s took early retirement. And the rest of us often have to take time off to either care for our own children and/or to quarantine due to close contact situations.

This year the Boston Public Schools is in great need for both short- and long-term substitute teachers. The need for substitute teachers in some schools is desperate as they need coverage for one in five classrooms.

Therefore I ask my fellow Bostonians to substitute for at least one day in our schools. Applicants can choose what days they work, where they work, what grades or subjects they would cover. Such selectability allows applicants to tailor their work with their personal responsibilities. Let me assure you, whatever time you have available, the BPS will have a spot for you.

Our traditional substitute pool is retired teachers. This year that pool has all but dried up. Concerns over COVID keep many of our retirees at home. Those who are still subbing are not enough to fill all of our vacancies. So who can help us now? I believe we have untapped resources in our local universities and in the Boston business community.

When the pandemic burst upon the scene in 2020, many medical and nursing students were fast-tracked into full-time positions to meet the sudden and enormous need for more doctors and nurses. I am asking the local schools of education to do the same right now to help us fill our vacancies. The colleges have eager aspiring teachers. Putting the two together is a classic win-win.

I am also calling upon the Boston business community. Over the years, many businesses have used their corporate retreat time for community building. They come into our school for a day of service. Such days traditionally entailed painting classrooms or helping to plant a garden. This year, why not come into the classrooms and share your knowledge with our students?

Accountants could come into a math class and tell the students how what they are learning now could lead to good jobs later. Graphic designers could tell students how art and computer science classes blend into an exciting career. Students love hearing from adults in their community. Such contact makes their learning tangible instead of theoretical.

You could talk about how you got to your current career — was it what you always wanted to do or did you take many roads on your journey? If you have seventh or eighth graders, share your hobbies, your travels, your culture — this age craves exposure to the world around them. If you are in an elementary school you can read your favorite book, talk about your favorite games as child, bring your best Dad jokes — these kids just want to feel like you like them.

If you are worried about what substitute teaching would be like and would you be good at it, let me assure you that all you need is an open mind and a kind heart. When you enter the school building, you will be given a substitute folder. In it will be all the materials you will need for the day: seating charts, class lists, assignments and directions.

My own career began as a substitute teacher. I wasn’t quite Glenn Holland in “Mr. Holland’s Opus,” but I was a young man who thought substitute teaching would be a good way to earn some money while I studied for law school. And like Mr. Holland, I fell in love with a job I never knew I wanted. Twenty-eight years later, I can tell you that I love the job more now than on day one. I invite you to experience this joy for yourself.

Substitute teaching in Boston is not volunteering, you will get paid. If you work one day at a time, the pay is $170 per diem. If you work in the same class for a longer period of time, greater than 25 school days, the pay increases to $330 a day.

So go to bostonpublicschools.org/jobs and help our schools, ours students and our teachers. We need you now more than ever.


Michael J. Maguire teaches Latin at Boston Latin Academy and serves on the Executive Board of the Boston Teachers Union.

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