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.
Are Dryer Sheets and Liquid Softeners Safe for the Environment? https://t.co/NTK3QGK1RG @CleanAirMoms @ewg @goodhealth— EcoWatch (@EcoWatch)1519666753.0
Reposted with permission from our media associate The Conversation.
By Michael Svoboda, Ph.D.
Despite a journey to this moment even more treacherous than expected, Americans now have a fresh opportunity to act, decisively, on climate change.
The authors of the many new books released in just the past few months (or scheduled to be published soon) seem to have anticipated this pivotal moment.
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EcoWatch Daily Newsletter
By Katy Neusteter
The Biden-Harris transition team identified COVID-19, economic recovery, racial equity and climate change as its top priorities. Rivers are the through-line linking all of them. The fact is, healthy rivers can no longer be separated into the "nice-to-have" column of environmental progress. Rivers and streams provide more than 60 percent of our drinking water — and a clear path toward public health, a strong economy, a more just society and greater resilience to the impacts of the climate crisis.
Public Health<img lazy-loadable="true" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTUyNDY3MC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY2MDkxMTkwNn0.pyP14Bg1WvcUvF_xUGgYVu8PS7Lu49Huzc3PXGvATi4/img.jpg?width=980" id="8e577" class="rm-shortcode" data-rm-shortcode-id="1efb3445f5c445e47d5937a72343c012" data-rm-shortcode-name="rebelmouse-image" data-width="3000" data-height="2302" />
Wild and Scenic Merced River, California. Bob Wick / BLM<p>Let's begin with COVID-19. More than <a href="https://www.nytimes.com/interactive/2020/us/coronavirus-us-cases.html?name=styln-coronavirus&region=TOP_BANNER&block=storyline_menu_recirc&action=click&pgtype=LegacyCollection&impression_id=2f508610-2a87-11eb-8622-4f6c038cbd1d&variant=1_Show" target="_blank">16 million Americans</a> have contracted the coronavirus and, tragically,<a href="https://www.nytimes.com/interactive/2020/us/coronavirus-us-cases.html?name=styln-coronavirus&region=TOP_BANNER&block=storyline_menu_recirc&action=click&pgtype=LegacyCollection&impression_id=2f508610-2a87-11eb-8622-4f6c038cbd1d&variant=1_Show" target="_blank"> more than</a> <a href="https://www.nytimes.com/interactive/2020/us/coronavirus-us-cases.html?name=styln-coronavirus&region=TOP_BANNER&block=storyline_menu_recirc&action=click&pgtype=LegacyCollection&impression_id=2f508610-2a87-11eb-8622-4f6c038cbd1d&variant=1_Show" target="_blank">300,000 have died</a> due to the pandemic. While health officials encourage hand-washing to contain the pandemic, at least <a href="https://closethewatergap.org/" target="_blank">2 million Americans</a> are currently living without running water, indoor plumbing or wastewater treatment. Meanwhile, <a href="https://www.theguardian.com/us-news/2020/jun/23/millions-of-americans-cant-afford-water-bills-rise" target="_blank">aging water infrastructure is growing increasingly costly for utilities to maintain</a>. That cost is passed along to consumers. The upshot? <a href="https://research.msu.edu/affordable-water-in-us-reaching-a-crisis/" target="_blank">More than 13 million</a> U.S. households regularly face unaffordable water bills — and, thus, the threat of water shutoffs. Without basic access to clean water, families and entire communities are at a higher risk of <a href="https://www.americanprogress.org/issues/green/news/2020/08/05/488705/bridging-water-access-gap-covid-19-relief/" target="_blank">contracting</a> and spreading COVID-19.</p><p>We have a moral duty to ensure that everyone has access to clean water to help prevent the spread of the coronavirus. Last spring, <a href="https://nymag.com/intelligencer/2020/03/coronavirus-stimulus-bill-explained-bailouts-unemployment-benefits.html" target="_blank">Congress appropriated more than $4 trillion</a> to jumpstart the economy and bring millions of unemployed Americans back to work. Additional federal assistance — desperately needed — will present a historic opportunity to improve our crumbling infrastructure, which has been <a href="https://www.theguardian.com/us-news/2020/jun/23/millions-of-americans-cant-afford-water-bills-rise" target="_blank" rel="noopener noreferrer">grossly underfunded for decades</a>.</p><p>A report by my organization, American Rivers, suggests that <a href="https://s3.amazonaws.com/american-rivers-website/wp-content/uploads/2020/07/09223525/ECONOMIC-ENGINES-Report-2020.pdf" target="_blank" rel="noopener noreferrer">Congress must invest at least $50 billion</a> "to address the urgent water infrastructure needs associated with COVID-19," including the rising cost of water. This initial boost would allow for the replacement and maintenance of sewers, stormwater infrastructure and water supply facilities.</p>
Economic Recovery<p>Investing in water infrastructure and healthy rivers also creates jobs. Consider, for example, that <a href="https://tinyurl.com/y9p6sgnk" target="_blank">every $1 million spent on water infrastructure in the United States generates more than 15 jobs</a> throughout the economy, according to a report by the Value of Water Campaign. Similarly, <a href="https://tinyurl.com/yyvd2ksp" target="_blank">every "$1 million invested in forest and watershed restoration contracting will generate between 15.7 and 23.8 jobs,</a> depending on the work type," states a working paper released by the Ecosystem Workforce Program, University of Oregon. Healthy rivers also spur tourism and recreation, which many communities rely on for their livelihoods. According to the findings by the Outdoor Industry Association, which have been shared in our report, "Americans participating in watersports and fishing spend over <a href="https://s3.amazonaws.com/american-rivers-website/wp-content/uploads/2020/06/30222425/Exec-summary-ECONOMIC-ENGINES-Report-June-30-2020.pdf" target="_blank">$174 billion</a> on gear and trip related expenses. And, the outdoor watersports and fishing economy supports over <a href="https://s3.amazonaws.com/american-rivers-website/wp-content/uploads/2020/06/30222425/Exec-summary-ECONOMIC-ENGINES-Report-June-30-2020.pdf" target="_blank">1.5 million jobs nationwide</a>."</p><p>After the 2008 financial crisis, Congress invested in infrastructure to put Americans back to work. The American Recovery and Reinvestment Act <a href="https://thehill.com/blogs/congress-blog/economy-a-budget/25941-clean-water-green-infrastructure-get-major-boost" target="_blank">of 2009 (ARRA) allocated $6 billion</a> for clean water and drinking water infrastructure to decrease unemployment and boost the economy. More specifically, <a href="https://www.conservationnw.org/news-updates/us-reps-push-for-millions-of-restoration-and-resilience-jobs/" target="_blank" rel="noopener noreferrer">an analysis of ARRA</a> "showed conservation investments generated 15 to 33 jobs per million dollars," and more than doubled the rate of return, according to a letter written in May 2020 by 79 members of Congress, seeking greater funding for restoration and resilience jobs.</p><p>Today, when considering how to create work for the <a href="https://www.bls.gov/news.release/pdf/empsit.pdf" target="_blank" rel="noopener noreferrer">10.7 million</a> people who are currently unemployed, Congress should review previous stimulus investments and build on their successes by embracing major investments in water infrastructure and watershed restoration.</p>
Racial Justice<p>American Rivers also recommends that Congress dedicate <a href="https://s3.amazonaws.com/american-rivers-website/wp-content/uploads/2020/07/09223525/ECONOMIC-ENGINES-Report-2020.pdf" target="_blank" rel="noopener noreferrer">$500 billion for rivers and clean water over the next 10 years</a> — not just for the benefit of our environment and economy, but also to begin to address the United States' history of deeply entrenched racial injustice.</p><p>The <a href="https://www.epa.gov/npdes/sanitary-sewer-overflows-ssos" target="_blank" rel="noopener noreferrer">23,000-75,000 sewer overflows</a> that occur each year release up to <a href="https://www.americanrivers.org/2020/05/fighting-for-rivers-means-fighting-for-justice/#:~:text=There%20are%20also%2023%2C000%20to%2075%2C000%20sanitary%20sewer,to%20do%20with%20the%20mission%20of%20American%20Rivers." target="_blank" rel="noopener noreferrer">10 billion gallons of toxic sewage</a> <em>every day</em> into rivers and streams. This disproportionately impacts communities of color, because, for generations, Black, Indigenous, Latinx and other people of color have been <a href="https://www.scientificamerican.com/article/flooding-disproportionately-harms-black-neighborhoods/" target="_blank" rel="noopener noreferrer">relegated</a> to live in flood-prone areas and in neighborhoods that have been intentionally burdened with a lack of development that degrades people's health and quality of life. In some communities of color, incessant flooding due to stormwater surges or <a href="https://www.ajc.com/opinion/opinion-partnering-to-better-manage-our-water/7WQ6SEAQP5E4LGQCEYY5DO334Y/" target="_blank" rel="noopener noreferrer">combined sewer overflows</a> has gone unmitigated for decades.</p><p>We have historically treated people as separate from rivers and water. We can't do that anymore. Every voice — particularly those of people most directly impacted — must have a loudspeaker and be included in decision-making at the highest levels.</p><p>Accordingly, the new administration must diligently invest in projects at the community level that will improve lives in our country's most marginalized communities. We also must go further to ensure that local leaders have a seat at the decision-making table. To this end, the Biden-Harris administration should restore <a href="https://www.epa.gov/cwa-401#:~:text=Section%20401%20Certification%20The%20Clean%20Water%20Act%20%28CWA%29,the%20United%20States.%20Learn%20more%20about%20401%20certification." target="_blank">Section 401 of the Clean Water Act</a>, which was undermined by the <a href="https://earthjustice.org/news/press/2020/tribes-and-environmental-groups-sue-trump-administration-to-preserve-clean-water-protections#:~:text=Under%20Section%20401%20of%20the%20Clean%20Water%20Act%2C,seeks%20to%20undermine%20that%20authority%20in%20several%20ways%3A" target="_blank">Trump administration's 2020 regulatory changes</a>. This provision gives states and tribes the authority to decide whether major development projects, such as hydropower and oil and gas projects, move forward.</p>
Climate Resilience<p>Of course, the menacing shadow looming over it all? Climate change. <a href="https://media.ifrc.org/ifrc/wp-content/uploads/2020/11/IFRC_wdr2020/IFRC_WDR_ExecutiveSummary_EN_Web.pdf" target="_blank">More than 100 climate-related catastrophes</a> have pummeled the Earth since the pandemic was declared last spring, including the blitzkrieg of megafires, superstorms and heat waves witnessed during the summer of 2020, directly impacting the lives of more than <a href="https://media.ifrc.org/ifrc/wp-content/uploads/2020/11/IFRC_wdr2020/IFRC_WDR_ExecutiveSummary_EN_Web.pdf" target="_blank">50 million people globally</a>.</p><p>Water and climate scientist Brad Udall often says, "<a href="https://www.youtube.com/watch?v=xQhpj5G0dME" target="_blank">Climate change is water change</a>." In other words, the most obvious and dire impacts of climate change are evidenced in profound changes to our rivers and water resources. You've likely seen it where you live: Floods are more damaging and frequent. Droughts are deeper and longer. Uncertainty is destabilizing industry and lives.</p><p>By galvanizing action for healthy rivers and managing our water resources more effectively, we can insure future generations against the consequences of climate change. First, we must safeguard rivers that are still healthy and free-flowing. Second, we must protect land and property against the ravages of flooding. And finally, we must promote policies and practical solutions that take the science of climate disruption into account when planning for increased flooding, water shortage and habitat disruption.</p><p>Imagine all that rivers do for us. Most of our towns and cities have a river running through them or flowing nearby. Rivers provide clean drinking water, irrigate crops that provide our food, power our homes and businesses, provide wildlife habitat, and are the lifeblood of the places where we enjoy and explore nature, and where we play and nourish our spirits. Healthy watersheds help <a href="https://news.un.org/en/story/2020/03/1059952" target="_blank" rel="noopener noreferrer">mitigate</a> climate change, absorbing and reducing the amount of carbon in the atmosphere. Healthy rivers and floodplains help communities adapt and build resilience in the face of climate change by improving flood protection and providing water supply and quality benefits. Rivers are the cornerstones of healthy, strong communities.</p><p>The more than <a href="https://archive.epa.gov/water/archive/web/html/index-17.html" target="_blank" rel="noopener noreferrer">3 million miles</a> of rivers and streams running across our country are a source of great strength and opportunity. When we invest in healthy rivers and clean water, we can improve our lives. When we invest in rivers, we create jobs and strengthen our economy. When we invest in rivers, we invest in our shared future.</p>
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