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Silver Nanoparticles in Clothing Wash Out, May Be Toxic
By Sukalyan Sengupta and Tabish Nawaz
Humans have known since ancient times that silver kills or stops the growth of many microorganisms. Hippocrates, the father of medicine, is said to have used silver preparations for treating ulcers and healing wounds. Until the introduction of antibiotics in the 1940s, colloidal silver (tiny particles suspended in a liquid) was a mainstay for treating burns, infected wounds and ulcers. Silver is still used today in wound dressings, in creams and as a coating on medical devices.
Since the 1990s, manufacturers have added silver nanoparticles to numerous consumer products to enhance their antibacterial and anti-odor properties. Examples include clothes, towels, undergarments, socks, toothpaste and soft toys. Nanoparticles are ultra-small particles, ranging from 1 to 100 nanometers in diameter—too small to see even with a microscope. According to a widely cited database, about one-fourth of nanomaterial-based consumer products currently marketed in the U.S. contain nanosilver.
Korean toothpaste containing nanosilver Alex Parlini, Project on Emerging Nanotechnologies, CC BY-ND
Multiple studies have reported that nanosilver leaches out of textiles when they are laundered. Research also reveals that nanosilver may be toxic to humans and aquatic and marine organisms. Although it is widely used, little is understood about its fate or long-term toxic effects in the environment.
We are developing ways to convert this potential ecological crisis into an opportunity by recovering pure silver nanoparticles, which have many industrial applications, from laundry wastewater. In a recently published study, we describe a technique for silver recovery and discuss the key technical challenges. Our approach tackles this problem at the source—in this case, individual washing machines. We believe that this strategy has great promise for getting newly identified contaminants out of wastewater.
A Textile Silver Lode
Use of nanosilver in consumer products has steadily risen in the past decade. The market share of silver-based textiles rose from 9 percent in 2004 to 25 percent in 2011.
Several investigators have measured the silver content of textiles and found values ranging from 0.009 to 21,600 milligrams of silver per kilogram of textile. Studies show that the amount of silver leached in the wash solution depends on many factors, including interactions between detergent and other chemicals and how silver is attached to the textiles.
In humans, exposure to silver can harm liver cells, skin and lungs. Prolonged exposure or exposure to a large dose can cause a condition called argyria, in which the victim's skin turns permanently bluish-gray.
Toxic effects of silver nanoparticles on zebra fish embryos Asharani et al., 2008., CC BY
Once silver goes down the drain and ends up at wastewater treatment plants, it can potentially harm bacterial treatment processes, making them less efficient, and foul treatment equipment. More than 90 percent of silver nanoparticles released in wastewater end up in nutrient-rich biosolids left over at the end of sewage treatment, which often are used on land as agricultural fertilizers.
This poses multiple risks. If plants take up silver from soil, they could concentrate it and introduce it into the food chain. It also can leach into groundwater or wash into rivers via rainstorms or erosion.
Treating Laundry Water at the Source
Our research shows that the most efficient way to remove silver from wastewater is by treating it in the washing machine. At this point silver concentrations are relatively high, and silver is initially released from treated clothing in a chemical form that is feasible to recover.
Once laundry washwater is piped to wastewater treatment plants and mixed with sewage and water from other sources, silver concentrations decrease significantly and can be converted into different chemical forms.
Deer Island Wastewater Treatment Plant, Boston, Massachusetts Doc Searls, CC BY
A bit of chemistry is helpful here. Our recovery method employs a widely used chemistry process called ion exchange. Ions are atoms or molecules that have an electrical charge. In ion exchange, a solid and a liquid are brought together and exchange ions with each other.
For example, household soaps do not lather well in "hard" water, which contains high levels of ions such as magnesium and calcium. Many home water filters use ion exchange to "soften" the water, replacing those materials with other ions that do not affect its properties in the same way.
For this process to work, the ions that switch places must both be either positively or negatively charged. Nanosilver is initially released from textiles as silver ion, which is a cation—an ion with a positive charge (hence the plus sign in its chemical symbol, Ag+).
Even at the source, removing silver from washwater is challenging. Silver concentrations in the wash solution are relatively low compared to other cations, such as calcium, that could interfere with the removal process. Detergent chemistry complicates the picture further because some detergent components can potentially interact with silver.
To recover silver without picking up other chemicals, the recovery process must use materials that have a chemical affinity for silver. In a previous study, we described a potential solution: Using ion-exchange materials embedded with sulfur-based chemicals, which bind preferentially with silver.
In our new study, we passed washwater through an ion-exchange resin column and analyzed how each major detergent ingredient interacted with silver in the water and affected the resin's ability to remove silver from the water. By manipulating process conditions such as pH, temperature and concentration of nonsilver cations, we were able to identify conditions that maximized silver recovery.
Schematic of the silver recovery process using ion-exchange resinTabish Nawaz
We found that pH and the levels of calcium ions (Ca2+) were critical factors. Higher levels of hydrogen or calcium ions bind up detergent ingredients and prevent them from interacting with silver ions, so the ion-exchange resin can remove the silver from the solution. We also found that some detergent ingredients—particularly bleaching and water-softening agents—made the ion-exchange resin work less efficiently. Depending on these conditions, we recovered between 20 percent and 99 percent of the silver in the washwater.
Our findings can spur research into alternative detergent formulations that improve silver recovery. They also show that ion-exchange technology can recover trace silver from washwater that contains high levels of detergent.
The Future of Wastewater Treatment
Today wastewater is collected from multiple sources, such as homes and businesses, and piped over long distances to centralized wastewater treatment plants. But increasing evidence shows that these facilities are ill-equipped to keep newly identified contaminants out of the environment, since they use one common treatment scheme for many different waste streams.
We believe the future is in decentralized systems that can treat different types of wastewater with specific technologies designed specifically for the materials they contain. If wastewater from laundromats contains different contaminants than wastewater from restaurants, why treat them the same way?
Our approach is both more efficient and a more effective way to address new environmental problems—potentially through a step as simple as installing a specialized water treatment cartridge in your washing machine.
Reposted with permission from our media associate The Conversation.
EcoWatch Daily Newsletter
By Tom Duszynski
The coronavirus is certainly scary, but despite the constant reporting on total cases and a climbing death toll, the reality is that the vast majority of people who come down with COVID-19 survive it. Just as the number of cases grows, so does another number: those who have recovered.
In mid-March, the number of patients in the U.S. who had officially recovered from the virus was close to zero. That number is now in the tens of thousands and is climbing every day. But recovering from COVID-19 is more complicated than simply feeling better. Recovery involves biology, epidemiology and a little bit of bureaucracy too.
How does your body fight off COVID-19?<p>Once a person is exposed the coronavirus, the body starts producing <a href="https://www.mblintl.com/products/what-are-antibodies-mbli/" target="_blank">proteins called antibodies to fight the infection</a>. As these <a href="https://www.statnews.com/2020/03/27/serological-tests-reveal-immune-coronavirus/" target="_blank">antibodies start to successfully contain the virus</a> and keep it from replicating in the body, symptoms usually begin to lessen and you start to feel better. Eventually, if all goes well, your immune system will completely destroy all of the virus in your system. A person who was infected with and survived a virus with no long-term health effects or disabilities has "recovered."</p><p>On average, a person who is infected with SARS-CoV-2 will feel ill for about seven days from the onset of symptoms. Even after symptoms disappear, there still may be small amounts of the virus in a patient's system, and they should stay <a href="https://www.cdc.gov/coronavirus/2019-ncov/if-you-are-sick/steps-when-sick.html" target="_blank">isolated for an additional three days</a> to ensure they have truly <a href="https://health.usnews.com/conditions/articles/coronavirus-recovery-what-to-know" target="_blank">recovered and are no longer infectious</a>.</p>
What about immunity?<p>In general, once you have recovered from a viral infection, your body will keep cells called lymphocytes in your system. These cells "remember" viruses they've previously seen and can react quickly to fight them off again. If you are exposed to a virus you have already had, your antibodies will likely stop the virus before it starts causing symptoms. <a href="https://dx.doi.org/10.5114%2Fceji.2018.77390" target="_blank">You become immune</a>. This is the <a href="https://www.ncbi.nlm.nih.gov/books/NBK27158/" target="_blank">principle behind many vaccines</a>.</p><p>Unfortunately, immunity isn't perfect. For many viruses, like mumps, immunity can wane over time, leaving you <a href="https://www.sciencedaily.com/releases/2016/04/160421145747.htm" target="_blank">susceptible to the virus in the future</a>. This is why you need to get revaccinated – those "booster shots" – occasionally: to prompt your immune system to make more antibodies and memory cells.</p><p>Since this coronavirus is so new, scientists still don't know whether people who recover from COVID-19 are <a href="https://www.cdc.gov/coronavirus/2019-ncov/hcp/faq.html" target="_blank">immune to future infections of the virus</a>. Doctors are finding antibodies in ill and recovered patients, and <a href="https://www.cdc.gov/coronavirus/2019-ncov/hcp/clinical-guidance-management-patients.html" target="_blank">that indicates the development of immunity</a>. But the question remains how long that immunity will last. Other coronaviruses like <a href="https://doi.org/10.1002/jmv.25685" target="_blank">SARS and MERS produce an immune response</a> that will protect a person at least for a short time. I would suspect the same is true of SARS-CoV-2, but the research simply hasn't been done yet to say so definitively.</p>
Why have so few people officially recovered in the US?<p>This is a dangerous virus, so the Centers for Disease Control and Prevention is being extremely careful when deciding what it means to recover from COVID-19. Both medical and testing criteria must be met before a person is <a href="https://www.cdc.gov/coronavirus/2019-ncov/hcp/disposition-in-home-patients.html" target="_blank">officially declared recovered</a>.</p><p>Medically, a person must be fever-free without fever-reducing medications for three consecutive days. They must show an improvement in their other symptoms, including reduced coughing and shortness of breath. And it must be at least seven full days <a href="https://health.usnews.com/conditions/articles/coronavirus-recovery-what-to-know" target="_blank">since the symptoms began</a>.</p><p>In addition to those requirements, the CDC guidelines say that a person must test negative for the coronavirus twice, with the <a href="https://www.cdc.gov/coronavirus/2019-ncov/if-you-are-sick/care-for-someone.html" target="_blank">tests taken at least 24 hours apart</a>.</p><p>Only then, if both the symptom and testing conditions are met, is a person officially considered recovered by the CDC.</p><p>This second testing requirement is likely why there were so few official recovered cases in the U.S. until late March. Initially, there was a <a href="https://www.nytimes.com/2020/03/18/health/coronavirus-test-shortages-face-masks-swabs.html" target="_blank">massive shortage of testing in the U.S.</a> So while many people were certainly recovering over the last few weeks, this could not be officially confirmed. As the country enters the height of the pandemic in the coming weeks, focus is still on <a href="https://www.cdc.gov/coronavirus/2019-nCoV/hcp/clinical-criteria.html" target="_blank">testing those who are infected</a>, not those who have likely recovered.</p><p>Many more people are being tested now that states and private companies have begun <a href="https://www.cdc.gov/coronavirus/2019-ncov/cases-updates/testing-in-us.html" target="_blank">producing and distributing tests</a>. As <a href="https://www.dispatch.com/news/20200406/coronavirus-in-ohio-from-its-rocky-start-testing-for-covid-19-slowly-ramping-up" target="_blank">the number of available tests increases</a> and the pandemic eventually slows in the country, more testing will be available for those who have appeared to recover. As people who have already recovered are tested, the appearance of any new infections will help researchers learn <a href="https://www.statnews.com/2020/03/24/we-need-smart-coronavirus-testing-not-just-more-testing/" target="_blank">how long immunity can be expected to last</a>.</p>
Once a person has recovered, what can they do?<p>Knowing whether or not people are immune to COVID-19 after they recover is going to determine what individuals, communities and society at large can do going forward. If scientists can show that recovered patients are immune to the coronavirus, then a person who has recovered could in theory <a href="https://www.vox.com/2020/3/30/21186822/immunity-to-covid-19-test-coronavirus-rt-pcr-antibody" target="_blank">help support the health care system</a> by caring for those who are infected.</p><p>Once communities pass the peak of the epidemic, the number of new infections will decline, while the number of <a href="https://www.newsweek.com/china-says-passed-peak-coronavirus-epidemic-covid-19-1491863" target="_blank">recovered people will increase</a>. As these trends continue, the risk of transmission will fall. Once the risk of transmission has fallen enough, community-level isolation and social distancing orders will begin to relax and businesses will start to reopen. Based on what other countries have gone through, it will be <a href="https://www.nature.com/articles/d41586-020-00154-w" target="_blank">months until the risk of transmission is low</a> in the U.S.</p><p>But before any of this can happen, the U.S. and the world need to make it through the peak of this pandemic. Social distancing works to slow the spread of infectious diseases and <a href="https://www.cdc.gov/coronavirus/2019-ncov/need-extra-precautions/what-you-can-do.html" target="_blank">is working for COVID-19</a>. Many people will <a href="https://www.yalemedicine.org/stories/2019-novel-coronavirus/" target="_blank">need medical help to recover</a>, and social distancing will slow this virus down and give people the best chance to do so.</p>
By Elizabeth Claire Alberts
The future for the world's oceans often looks grim. Fisheries are set to collapse by 2048, according to one study, and 8 million tons of plastic pollute the ocean every year, causing considerable damage to delicate marine ecosystems. Yet a new study in Nature offers an alternative, and more optimistic view on the ocean's future: it asserts that the entire marine environment could be substantially rebuilt by 2050, if humanity is able to step up to the challenge.
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Across the country, the novel coronavirus is severely affecting black people at much higher rates than whites, according to data released by several states, as The New York Times reported.
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By Zulfikar Abbany
Bread has been a source of basic nutrition for centuries, the holy trinity being wheat, maize and rice. It has also been the reason for a lot of innovation in science and technology, from millstones to microbiological investigations into a family of single-cell fungi called Saccharomyces.
Chemical leavening<p>If you like a little heft in your loaf, you will need a leavening agent.</p><p>For those short on time, you can use baking soda. That's a chemical compound of sodium bicarbonate mixed with potassium bitartrate, or cream of tartar.</p><p>Soda breads have their traditions in parts of eastern and central Europe, and in Ireland and Scotland, with Melrose loaves and "farls."</p><p>They can taste a bit bland, though, and are often considered only as an emergency solution on Sundays. No disrespect intended: They taste just fine fresh from the oven.</p><p>Whether it's chemical or more "natural," leavening relies largely on the production of carbon dioxide.</p><p>When you mix an acid, such as vinegar, buttermilk, yogurt or apple cider, with an alkaline compound like baking soda, you get CO2. That CO2 creates bubbles, which in turn capture steam in the oven and allow a bread to rise.</p><p><span></span>But it's better with yeast. Tastes better, too. It just takes more time. </p>
What is yeast?<p>There are yeasts all around us — on grains, in the air, in biofuels. It even lives inside us, but that's not always a good thing.</p><p><a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1090575/pdf/1471-2334-5-22.pdf" target="_blank">Candida yeast</a> can cause infections of the skin, feet, mouth, penis or vagina if it builds up too much in the body.</p><p>One of the most common yeasts, however, is <em>Saccharomyces cerevisiae</em>. That's <a href="https://www.dw.com/en/an-early-beer-archaeologists-tap-ground-at-worlds-oldest-brewery/a-45480731" target="_blank">"brewer's"</a> or "baker's" yeast.</p><p>You can get fresh baker's yeast, often in 42-gram (1.48-ounce) cubes, or as dried yeast (quick action or active, which requires rehydration) in a sachet of 7 grams.</p><p>There's little difference: One is compressed and the other is dehydrated and granulated. But they do the same thing, essentially. </p><p>Some commercial yeast producers add molasses and other nutrients. But natural yeast has plenty of useful nutrients in it anyway, including B group vitamins, so who knows whether it's good or necessary to add them. </p>
How does yeast work?<p>When you mix flour, yeast and water, you set off a veritable chain reaction. Enzymes in the wheat convert starch into sugar. And the yeast creates enzymes of its own to convert those sugars into a form it can absorb.</p><p>The yeast "feeds" on the sugars to create carbon dioxide and alcohol. The yeast burps and farts, releasing gases into the mix, and that creates bubbles to trap CO2. </p><p>It's a vital fermentation process that breaks down the gluten in the flour and helps make your bread more digestible.</p><p>The yeast cells split and reproduce, generating lactic and carbonic acid, raising the temperature and ultimately adding flavor to the mix.</p><p>The longer you leave the yeast to do its thing, the better for your bread. Time is more important than the amount of yeast. </p><p>In fact, that's an enduring question — how much yeast? I'll use 20 grams fresh yeast for 500 grams of flour. Others say that's enough yeast for 1 kilo. If you are converting a dry-yeast recipe to fresh yeast, some bakers advise tripling the weight. So, if a sachet of dried yeast is 7 grams, your fresh yeast is 21 grams.</p><p><span></span>But that also depends on the flours you are using, temperatures in the bowl and the room, and a host of other things. You'll just have to experiment and see. No number of books (and I've read a stack on bread) will help as much as trial and error.</p>
Wild yeast: Sourdough<p>So, good bread needs time. If you have a lot of time, why not move it up a notch and grow wild yeast — a sourdough starter — in your own home?</p><p>A sourdough starter is not to be mistaken (as it often is) for the leaven, or "mother," "sponge," or <em>levain</em>. That's more a second stage, a descendant of the starter. You take a scoop from your starter and add it to another flour and water mixture when you prepare the dough for a new loaf. </p><p>The sourdough process utilizes yeasts naturally present in flour and … yet more time. A longer fermentation process allows a richer lactic acid bacteria <em>lactobacilli</em> or LAB to evolve, and that can be healthy for your gut microbiome.</p><p>It's simple enough to start a sourdough starter. All you need is flour, warm water and time.</p><p>Some suggest equal measures of whole-grain flour and water at 28 degrees Celsius (82 degrees Fahrenheit), some say room temperature — just don't let the water exceed 40 C or the yeasts will die. Some suggest two parts flour to three parts water. But it's up to you whether you want a drier or wetter starter. You will know only through experimentation. </p><p>Some say you should filter tap water to remove chemicals like fluoride and avoid using water that's boiled and then cooled. Others say that really doesn't matter.</p><p>The main thing is, keep it clean and give it time. Days, weeks, months and years.</p>
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