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A New Tool to Design Safer Products

Saturday, December 8th, 2012

   New publication:  A New System to Assess New Chemicals for Endocrine Disruption

    A groundbreaking new paper outlines a safety testing system that helps chemists design inherently safer chemicals and processes.       Resulting from a cross-disciplinary collaboration among scientists, the innovative “TiPED” testing system (Tiered Protocol for Endocrine  Disruption) provides information for making chemicals and consumer products safer. TiPED can be applied at different phases of the chemical design process, and can steer companies away from inadvertently creating harmful products, and thus avoid adding another BPA or DDT to commerce.

    The study, “Designing Endocrine Disruption Out of the Next Generation of Chemicals,” is online in the Royal Society of Chemistry journal Green Chemistry.

    The 23 authors are biologists, green chemists and others from North America and Europe who say that recent product recalls and bans reveal that neither product manufacturers nor the government have adequate tools for dealing with endocrine disrupting chemicals (EDCs).  EDCs are chemicals commonly used in consumer products that can mimic hormones and lead to a host of modern day health epidemics including cancers, learning disabilities and immune system disorders. The authors conclude that as our understanding of the threat to human health grows, the need for an effective testing strategy for endocrine disrupting chemicals becomes imperative.

Historically, chemists have aimed to make products that are effective and economical. Considering toxicity when designing new chemicals has not been their responsibility. This collaboration between fields expands the scope of both biologists and chemists to lead to a way to design safer chemicals.

Scientific understanding of endocrine disruption has developed rapidly over the past 2 decades, providing detailed, mechanistic insights into the inherent hazards of chemicals.  TiPED uses these insights to guide chemical design toward safer materials.  And as consumers are increasingly concerned about endocrine disruption (eg BPA, flame retardants) they are demanding products that do not contain EDCs, creating a market opportunity for companies that can take advantage of the new science.

There is a companion website to the paper, www.TiPEDinfo.com. One can access the paper there and learn more about the TiPED system.

 

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New Tools to Design Safer Chemicals

Thursday, December 6th, 2012

PRESS RELEASE: “A New tool to design safer products”

New publication:  A New System to Assess New Chemicals for Endocrine Disruption

A groundbreaking new paper outlines a safety testing system that helps chemists design inherently safer chemicals and processes. Resulting from a cross-disciplinary collaboration among scientists, the innovative “TiPED” testing system (Tiered Protocol for Endocrine Disruption) provides information for making chemicals and consumer products safer. TiPED can be applied at different phases of the chemical design process, and can steer companies away from inadvertently creating harmful products, and thus avoid adding another BPA or DDT to commerce.

The study, “Designing Endocrine Disruption Out of the Next Generation of Chemicals,” is online in the Royal Society of Chemistry journal Green Chemistry.

The 23 authors are biologists, green chemists and others from North America and Europe who say that recent product recalls and bans reveal that neither product manufacturers nor the government have adequate tools for dealing with endocrine disrupting chemicals (EDCs).  EDCs are chemicals commonly used in consumer products that can mimic hormones and lead to a host of modern day health epidemics including cancers, learning disabilities and immune system disorders. The authors conclude that as our understanding of the threat to human health grows, the need for an effective testing strategy for endocrine disrupting chemicals becomes imperative.

Historically, chemists have aimed to make products that are effective and economical. Considering toxicity when designing new chemicals has not been their responsibility. This collaboration between fields expands the scope of both biologists and chemists to lead to a way to design safer chemicals.

Scientific understanding of endocrine disruption has developed rapidly over the past 2 decades, providing detailed, mechanistic insights into the inherent hazards of chemicals.  TiPED uses these insights to guide chemical design toward safer materials.  And as consumers are increasingly concerned about endocrine disruption (eg BPA, flame retardants) they are demanding products that do not contain EDCs, creating a market opportunity for companies that can take advantage of the new science.

There is a companion website to the paper, www.TiPEDinfo.com. One can access the paper there and learn more about the TiPED system.

 

 

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Designing the next generation of sustainable chemicals.

Friday, November 2nd, 2012

Environmental Factor, November 2012 see original article here.

By Thaddeus Schug

Tom Zoeller, Ph.D., Jerry Heindel, Ph.D., and Wim Thielemans, Ph.D.  Heindel, center, goes to work creating a toxic pumpkin, while Tom Zoeller, Ph.D., left, and Wim Thielemans, Ph.D., take part in the fun. (Photo courtesy of Pete Myers)

Scientists committed to developing green solutions for replacing problem chemicals in the marketplace gathered Oct. 15-17 for a meeting on “Building the Path Forward for the Next Generation of Sustainable Chemicals,” held at the Rockefeller Brothers Fund Pocantico Center in Tarrytown, N.Y.

The meeting, sponsored by the non-government organizations Advancing Green Chemistry  and Environmental Health Sciences,  brought together a mixture of chemists, toxicologists, and biologists. Representatives from NIEHS and NTP included Division of Extramural Research and Training program administrators Jerry Heindel, Ph.D., and Thaddeus Schug, Ph.D.; Kristina Thayer, Ph.D., director of the newly named NTP Office of Health Assessment and Translation; and NTP Biomolecular Screening Branch Chief Ray Tice, Ph.D.

Designing safer chemicals

There are more than 83,000 chemicals in commerce today, many of which pose potential toxic hazards to human health and the environment. The challenge facing chemists designing replacement materials involves figuring out what kind of testing will need to be done to determine if the new chemical is safer than current ones to human health and the environment. One area of growing concern is how to ensure that the next generation of chemicals does not have the potential to act as endocrine disrupting compounds.

The meeting at Pocantico aimed to build upon a new set of testing tools — the Tiered Protocol for Endocrine Disruptors (TiPED) — developed by the group over the past two years. The protocol, which will be published online Dec. 6 in the Royal Society of Chemistry journal Green Chemistry,  is not regulatory, but rather a tool to guide chemists as they develop a new chemical, to give them confidence as to whether the substance is or is not likely to be an endocrine disruptor.

The TiPED protocol offers a five-tiered approach, starting with what should be the fastest and cheapest assays, and working through increasingly specialized tests. The initial two phases rely on predictive computer modeling and high-throughput screening, to quickly weed out problem chemicals. These tests are followed by more specific in vitro cell-based screening assays with a goal of refining, reducing, and replacing animal testing as much as possible. The last two tiers are whole animal assays, to be used for looking for integrated endpoints and less understood systemic responses.

“The idea is that if chemists hit a positive early on, they would either go back to the drawing board or, if that positive was in a specific area, such as an estrogen receptor in a high throughput assay, they would follow that up with more comprehensive assays,” said Heindel. “A hit anywhere along the tiered system means chemists need to pull back, reanalyze, or throw the chemical out.”

The project emphasizes fundamental changes in the way that scientists design new chemicals, and in the process of bringing them into the marketplace. Chemists generally have little training in toxicology, so this plan offers guidelines they can follow early on in the product development process.

Moving forward with the plan

Following a team-building exercise on the evening of Oct. 15, involving pumpkins and toxicological design criteria, the first full day of the meeting was divided into discussion sessions aimed toward refining the specific testing strategies within each phase of the screening model. A good deal of time was dedicated to establishing criteria needed to assess the quality of assays within each tier of the protocol.

The meeting wrapped up with a discussion on strategies to conduct test runs of the protocol, using test chemicals synthesized by John Warner, Ph.D., president and founder of the Warner Babcock Institute for Green Chemistry.

(Thaddeus Schug, Ph.D., is a health scientist in the NIEHS Division of Extramural Research and Training and a regular contributor to the Environmental Factor.)

Disclaimer: This report was written by members of the NIEHS staff based on materials prepared for this meeting and the discussions that took place there. It reflects the views of the authors and not necessarily those of the Rockefeller Brothers Fund, its trustees, or its staff.

 

Coach Barn of the Pocantico Center, which is also known as the John D. Rockefeller Estate  The meeting was held on the ground floor of the Coach Barn of the Pocantico Center, which is also known as the John D. Rockefeller Estate. Take a video tour.  (Photo courtesy of Ray Tice)
Ray Tice, Ph.D., and Kristina Thayer, Ph.D.  Tice, left, and Thayer take part in a discussion of the endocrine disruptor screening protocol. (Photo courtesy of Pete Myers)
Tiered Protocol for Endocrine Disruptors (TiPED) working group  The TiPED working group enjoyed the fall weather and the beautiful scenery at the Pocantico Center in Tarrytown, N.Y. (Photo courtesy of Ray Tice)

 

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Teaching Green Chemistry and Toxicology.

Thursday, October 11th, 2012

Teaching Green

Original published in Chemical and Engineering News, October 1, 2012

The Green Chemistry Commitment’s learning objectives are designed to ensure that chemistry majors have proficiency in essential green chemistry competencies.

A group of educators in the U.S. has grown impatient with the slow headway in integrating the concepts of green chemistry and toxicology into the undergraduate chemistry curriculum. They are ready to ask academic institutions for pledges to accelerate that progress through an initiative called the Green Chemistry Commitment.

Colleges and universities that sign the commitment agree to develop goals for implementing a core set of learning objectives, says Amy S. Cannon, executive director of the nonprofit organization Beyond Benign, in Wilmington, Mass., which is leading the initiative. The objectives outline the basics of green chemistry and toxicology that students should take with them to the workplace after they graduate, Cannon says.

At the top of the list of objectives is that students should have a working knowledge of the 12 Principles of Green Chemistry. These principles, developed 15 years ago, serve as a conceptual framework to guide the design, manufacture, use, and recycling or disposal of chemical products in an economically, environmentally, and socially responsible way. Additional learning objectives include having an understanding of the molecular mechanisms of how chemicals affect human health and the environment and being prepared to communicate the benefits of green chemistry to society.

“The principles of green chemistry direct chemists toward safer, less toxic, and renewable chemistry and materials,” Cannon says. “But to advance green chemistry, a significant change must occur in how we are training the current and next generation of scientists. The Green Chemistry Commitment is an effort to unite the chemistry education community around common learning objectives that have traditionally been absent from our training as chemists.”

Many institutions have already committed significant time and financial resources to introduce green chemistry concepts into lecture courses, substitute green chemistry laboratory exercises in place of traditional labs, and use green chemistry as a research framework, Cannon says. However, a widespread, systematic approach to green chemistry education doesn’t yet exist, she notes.

For example, the American Chemical Society’s guidelines for bachelor’s degree programs provide broadly defined requirements for approved departments and graduates receiving certified degrees (C&EN, Sept. 24, page 39). Green chemistry is currently listed as a potential cross-disciplinary track that could be taught as part of the overall requirements.

Green chemistry advocates argue that green chemistry should be integrated into the foundation course work on analytical, biological, inorganic, organic, and physical chemistry, Cannon says. However, the ACS guidelines are not designed to specify the content of these courses. “Rather than waiting for a mandate to teach green chemistry principles and toxicology concepts, which might be a long time in coming, we thought we should create a mechanism for the chemistry community to commit to changing the curriculum now,” she says.

The Green Chemistry Commitment is designed to be flexible so that each institution can adopt the objectives according to its resources and capabilities, Cannon explains. For example, some departments might focus on integrating green chemistry into core lecture and lab courses, whereas others might develop separate green chemistry or toxicology courses.

Each institution’s progress in meeting the objectives will be charted in an annual report that provides an opportunity to update goals to help drive continual improvement. The reports will be evaluated by the initiative’s advisory board made up of established members of the green chemistry community, and the results will be shared with other institutions.

One university that hopes to sign on to the commitment is the University of California, Berkeley. The university is a relative newcomer to green chemistry, notes John Arnold, director of the Berkeley Center for Green Chemistry and an adviser to the Green Chemistry Commitment. UC Berkeley made its first foray into green chemistry four years ago when graduate students asked for permission to start a green chemistry and sustainable design seminar, Arnold says. The university has been rapidly expanding its efforts from there.

UC Berkeley’s green chemistry program has two focal points, he explains. At the graduate level, the department offers the seminar course and a lecture course in green chemistry. Arnold says the goal is to help the next generation of leaders in chemistry begin their careers able to include green chemistry in the courses they teach and in their research.

“At the undergraduate level, we want to weave green chemistry into the fabric of what we teach, so that undergraduate students can take these concepts with them as they go into the world as doctors, lawyers, engineers, politicians, and businesspeople,” Arnold says. To help meet that goal, UC Berkeley developed new lab experiments for its general chemistry course for nonchemistry majors, which is taken by more than 2,000 students per year—about half of all freshmen.

The Green Chemistry Commitment:

◾ Theory: Have a working knowledge of the 12 Principles of Green Chemistry.

◾ Toxicology: Have an understanding of the principles of toxicology, the molecular mechanisms of how chemicals affect human health and the environment, and how to access the resources to identify and assess molecular hazards.

◾ Laboratory skills: Possess the ability to recognize, assess, and design greener alternative chemical products and processes.

◾ Application: Be prepared to serve society in their professional capacities as scientists through the articulation, evaluation, and employment of methods and chemicals that are benign for human health and the environment.

Read the remainder of the original article HERE.

Chemical & Engineering News
ISSN 0009-2347
Copyright © 2012 American Chemical Society

 

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Building Links Between Green Chemists and Business in Education.

Wednesday, September 19th, 2012

On September 7 and 8, 2012, McGill University (Montréal, Canada) hosted a unique workshop designed to foster green innovation in the next generation. Ten MBA students from the Desautels Faculty of Management and ten PhD candidates from the departments of chemistry and civil engineering were gathered to reflect on this concept. Two guests speakers gave lectures putting green chemistry in the context of industry.

The first one, by Phil Dell’Orco, head of sustainability at GlaxoSmithKline (GSK), addressed the question of fostering and coordinating green chemistry in a large pharmaceutical company. Lynn Leger from Green Center Canada presented how her organization is constantly touring universities (in Canada and outside)

 

PHOTO: Phil Dell’Oroco, Process Engineering at GlaxoSmithKline. By Owen Egan for the McGill Reporter

to find scientific innovations and bring them to the market. She elaborated on  some of the challenges associated with the transition from research to the market. We also had a few smaller classes to introduce the concepts of green chemistry, such as the green principles and metrics, and what it takes to be successful in innovation, as well as green drivers of innovation.

Students were then divided into mixed groups (composed of both business and chemistry and engineering students) and had to work together on building a case study. They were given an innovation, coming straight from Green Centre Canada – an antibacterial compound mimicking garlic active ingredient. Students had to find a market, build a financial case and work some of the chemistry associated.

They came out of it with amazing presentations on their ideas and demonstrated outstanding ability to interact with people from a different  discipline. They all pointed out how much they appreciated being exposed to a difference academic culture and recognized the importance of building bonds across disciplines to bridge the gap towards greener innovations.

This workshop was made possible through funding from the CREATE program of  NSERC, a Canadian federal funding agency, and the Marcel Desautels Institute for Integrated Management. Steve Maguire (from the School of Management) and I created an organized the whole two-day event. And we’re very excited about it. We’ll definitely do it again next year.

Read about the workshop in the McGill Reporter.

By Audrey Moores, Ph.D.
Assistant Professor
Department of Chemistry
McGill University

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“Don’t put that junk on your junk”

Wednesday, July 18th, 2012


I recently said this to my favorite cyclist when discussing that he may not want to apply chamois cream containing parabens (the junk) to his junk. Male cyclists are repeatedly applying (maybe daily, for 5-7 hours at a time) these paraben containing creams to their reproductive parts. Research is showing that maybe they should reconsider.

 

You may see parabens listed as “methylparaben” “propylparaben” or “butylparaben” Etc.  Don’t let that fool you; these compounds are all structurally and functionally similar compounds, each just has an additional carbon group – the methyl, propyl, or butyl.

 

Parabens’ alias is alkyl hydroxy benzoate, not as easily recognizable, but still present on food and cosmetic labels. You can find these parabens in hair products, skin care products, or even your salad dressing! For male cyclists, they are in most creams that are applied to the groin area to alleviate chafing against the saddle of the bike.

 

Studies have shown that parabens can mimic the female sex hormone estrogen (Gomez et al 2005) and in turn can act as endocrine disruptors, inhibiting “testosterone (T)-induced transcriptional activity” (Chen et al 2007). Also, “exposure of post-weaning mammals to butyl paraben adversely affects the secretion of testosterone and the function of the male reproductive system.” Similar effects can be seen with propyl paraben (Oishi 2002).

 

What are other potential effects of this chemical on males? Recent research has shown parabens in association with  breast cancer, though causality has not yet been established (Khanna et al 2012).  This may seem irrelevant for men unless one considers the fact that breast cancer among men is actually on the rise.

 

Additionally, these chemicals may reduce male fertility. Butylparaben was shown in the lab to have an adverse effect on the male mouse reproductive system in that it damaged the late steps of spermatogenesis in the testis (Oishi 2002). Similar effects can be seen for other forms of parabens. They are also suspected of affecting the mitochondria in rat testes, reducing virility (Tavares et al 2008).

 

Male cyclists might want to look for anti-chafe chamois creams that do not contain parabens, such as creams containing lanolin, the oil in sheep’s wool. You can even make lanolin cream in your own home, following this recipe (but make sure the lanolin you use is high quality and pesticide free).

 

Alternatively, one can pay closer attention to the label on chamois cream to ensure that it does not contain parabens.

 

If you are a cyclist, know a cyclist, or love a cyclist, please share this with them.

 

By: Mana Sassanpour

 

Sources:

1. Antiandrogenic properties of parabens and other phenolic containing small molecules in personal care products. J. Chen, K.C. Ahn, N.A. Gee, S.J. Gee, B.D. Hammock, B.L. Lasley. Toxicology and Applied Pharmacology. Volume 221, Issue 3, 278–284, 2007.

 

2. Effects of propyl paraben on the male reproductive system. S. Oishi. Food and Chemical Toxicology. Volume 40, Issue 12, 1807 – 1815, 2002.

 

3. Estrogenic activity of cosmetic components in reporter cell lines: parabens, UV screens, and musks. E. Gomez, A. Pillon, H. Fenet, D. Rosain, M. J. Duchesne, J. C. Nicolas, P. Balaguer, C. Casellas. 
Journal of Toxicology and Environmental Health, Part A 
Vol. 68, Iss. 4, 2005.

 

4. Male breast carcinoma: increased awareness needed. J. White, O. Kearins, D. Dodwell, K. Horgan, A.M. Hanby, V. Speirs. Breast Cancer Research. Volume 13, Issue 5, 219, 2011.

 

5. Organ toxicity and mechanisms: effects of butyl paraben on the male reproductive system in mice. S. Oishi. Archives of Toxicology. Volume 76, Number 7, 423-429, 2002.

 

6. Parabens enable suspension growth of MCF-10A immortalized, non-transformed human breast epithelial cells. S Khanna and P.D. Darbre. Journal of Applied Toxicology. doi: 10.1002/jat.2753, 2012.

 

7. Parabens in male infertility—Is there a mitochondrial connection? R.S. Tavares, F.C. Martins, P.J. Oliveira, J. Ramalho-Santosa, F.P. Peixoto. Reproductive Toxicology. Volume 27, Issue 1, 1-7, 2009.

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Silver speeds chemical reactions with oxygen.

Monday, July 16th, 2012

Huang, Z,  X Gu, Q Cao, P Hu, J Hao, J Li and X Tang. 2012. Catalytically active single-atom sites fabricated from silver particles. Angewandte Chemie http://dx.doi.org/10.1002/anie.201109065.

Synopsis by Marty Mulvihill

In a new study, researchers report using silver in a safer, cheaper, cleaner method to run chemical reactions – specifically the widely-used and universally-important oxidation reactions. The new system works at low temperatures and is 10 times more efficient than previous attempts.

In the quest to save money and prevent waste when making chemicals for industrial and consumer applications, laboratory chemists are looking to a new generation of catalysts to speed up reactions with less mess. Catalysts are added to chemical reactions to help efficiently transform raw materials into products.

In a recent advance, researchers report how silver – placed in a specific pattern on a stable molecular nanostructure – can act as a catalyst and promote reactions at low temperatures using safe and abundant materials like oxygen in the reaction.

The new system is 10 times more efficient than previous attempts. It not only conserves resources, but it will help researchers better understand how to use oxygen in industrial applications.

The silver-based catalyst converts oxygen from the air into a chemically reactive form that allows common industrial chemicals to be made more efficiently. The products of these reactions are the starting materials for a majority of chemical products.

Unlike previous catalysts that promote chemical reactions with oxygen, this silver-based model performs very well at low temperatures. Temperature is a key consideration. Lower temperatures reduce the amount of energy and potentially the cost of running these important reactions.

The new catalyst created by researchers in China represents a 10-fold improvement over previous methods for making these chemical products.

Catalysts increase the speed of chemical reactions. Yet they are not affected in the process. This allows catalysts to be reused and has helped expand their use in a wide range of manufacturing applications.

In addition to working at low temperatures, the catalyst uses oxygen as the only additional reactant. Traditionally oxidation reactions have used harsh chemicals and generated large quantities of hazardous waste. In this reaction the oxygen is incorporated into the product without producing any additional waste.

The results will help chemists understand how to better activate oxygen. Oxygen is often slow to react with other molecules because the molecule is very stable. It is usually found as two atoms paired together, hence its chemical nickname O2. These pairs must be broken apart before the individual oxygen atoms can react with other chemicals.

The new catalyst breaks the oxygen atoms apart. It uses individual silver atoms located near a surface that does not have oxygen as part of its molecular structure.

Using advanced chemical analysis tools, the scientists precisely characterized and explained the reactivity of the silver atoms that are attached to the surface of manganese oxide particle support. They verified the structure of their active catalyst with advanced microscopy and X-ray scattering techniques.

The catalyst is only in the development stages. Before it is ready for use in the chemical industry, chemists will need to show that it can perform oxidation reactions cheaply on a wide range of organic molecules. Read more science at Environmental Health News.

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Bacteria detox process gives insight for safer chemicals.

Thursday, June 28th, 2012

Teufel, R, T Friedrich and G Fuchs. 2012. An oxygenase that forms and deoxygenates toxic epoxide. Nature http://dx.doi.org/10.1038/nature10862.

Synopsis by Jean-Philip Lumb
New insight on the way bacteria break down toxic chemicals could improve cleanup of contaminated sites and offer a molecular blueprint for chemicals that easily dismantle after use.

Chemists may now understand why some bacteria can break apart toxic substances without poisoning themselves. The answer centers on the surprising dual function of an enzyme that transforms harmful molecules into benign ones.

For the first time, German researchers have elucidated the precise actions of the enzyme nicknamed PaaABCE. It is known as a key player in the bacteria’s ability to dismantle and change molecules in a number of cell circumstances. The authors report their results in the journal Nature.

PaaABCE, they found, is unique because it has two distinct functions. On the one hand, it can insert oxygen into a toxic substance, setting it up for degradation. On the other hand, it can remove that same oxygen. The authors speculate that this dual function allows the bacteria to keep toxic materials in the cell at low levels, thus protecting the organism from harm during the detoxification process.

The report is significant because it increases understanding of the molecular mechanisms that bacteria use to detoxify their cell environments. The new insight could provide chemists with important instructions that would tell them how to dismantle old chemical pollutants and assemble new commercially viable ones that would possess decreased lifetimes in the environment.

Chemists produce molecules that serve important roles in countless commercial products. Coloring agents, plasticizers, odorants and preservatives are examples.

But what happens to these compounds once they are finished performing their intended function?

Many are released into the environment and linger there. A potential risk is that these molecules will accumulate in fatty tissues and pass up the food chain. This outcome is particularly troublesome given the lack of required biological testing before a new chemical is introduced into a commercial product.

Even though chemical breakdown in the environment is as equally important as synthesis, it can be far more challenging. Most industrial chemicals are designed to be stable to avoid premature degradation. This same stability causes problems when molecules are released into the environment after their intended commercial life.

A potential solution is to design chemicals that common bacteria in the soil or water can readily break down into innocuous substances. In this fashion, chemicals could perform their purpose in a product, but would then rapidly degrade when released into the environment, ensuring the integrity of natural systems.

In order for chemists to be able to design chemicals with these properties, the precise mechanisms that bacteria use, and also the nature of the intermediates that are involved in the breakdown pathways, need to be well understood.

This study takes an important step in that direction. By successfully reconstituting the biochemical machinery that is required for specific bacteria (Pseudomonas sp.) to break down the chemical phenyl acetic acid, the researchers clarified the role of an essential enzyme that performs an unprecedented chemical reaction in the biochemical pathway.

In the key step of the process, the enzyme PaaABCE adds an oxygen atom in a chemical reaction known as an epoxidation. The product of this reaction is reactive, and is immediately transformed into innocuous byproducts by a series of other enzymes.

At this point, the authors know all of the atoms that comprise PaaABCE, but not their arrangement in space. Therefore, the next step will be to figure out its structure. Knowing its chemical structure will allow chemists to design new synthetic catalysts to remediate soil or purify water. Read more science at Environmental Health News.

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Silver from nanoparticles found in plants and animals.

Friday, June 15th, 2012

Synopsis by Marty Mulvihill and Wendy Hessler

2012-0613mesocosm
Benjamin Espinasse, CEINT, Duke University
Mesocosms provided outdoor labs to study silver nanoparticles.

The silver from tiny particles used to kill microbes in clothing and other consumer goods may wind up in plants, insects and fish, according to new research. The study is the first to track how silver nanoparticles react, change and move through ecosystems, and it adds to a growing number of studies that raise concerns about their widespread use as anti-microbial agents. Researchers have not yet studied their potential effect on plants and animals.

 

Context

Manufacturers are putting silver nanoparticles into a growing list of consumer products despite the fact that little is known about their health or environmental impacts. The Project on Emerging Nanotechnologies estimates that as of 2010, more than 300 products use sliver nanoparticles as an antimicrobial agent. These items include clothing, food storage containers, pharmaceuticals, cosmetics, electronics and optical devices.Silver nanoparticles are very small chunks of silver metal made up of thousands of silver atoms. They are so small that 400 million would fit in the period at the end of this sentence. A chemical coat is often added to prevent clumping and protect their silver core.The element silver discourages the growth of bacteria and other pathogens. The U.S. Environmental Protection Agency regulates silver and some related compounds as pesticides. The agency supports health and safety testing of the highly used silver nanoparticles but does not regulate their specific use.Like most nanoparticles, silver varieties have benefits and risks. Their unique size gives them properties different from both large pieces of silver and individual silver ions. As antibacterial agents, the silver nanoparticles are far more effective, cheaper and use less silver than many alternatives.Silver’s ability to kill bacteria has raised concerns that the nanomaterials may affect beneficial bacteria and the plants and animals essential to a healthy ecosystem. While it is not considered toxic to people, invertebrates and fish are far more sensitive to silver.Cell studies suggest silver affects nerve cells, while silver nanoparticles have been shown to interfere with human sperm development. It is known that fish are vulnerable to even low doses of silver, andstudies indicate that silver nanoparticles can cause malformations and death in embryos exposed to the materials (Bar-Ilan et al. 2009). Exposure to silver also affects reproduction in clams (Brown et al. 2003).Silver nanoparticles are released from products during normal use and washing. They enter the environment through wastewater, as water treatment facilities do not always remove them completely (Keagi et al. 2011).Researchers are rushing to understand what happens to nanoparticles after they are released. Initial studies suggest they can clump together to make larger particles, dissolve to release silver ions and react with oxygen and sulfur to form new types of particles.

 

 

What did they do?

Silver nanoparticles were sprayed onto soil and water in simulated terrestrial and wetland habitats to determine how the particles might change chemically, move through the ecosystems and interact with plants and animals after they get into the environment.The researchers built the habitats (called mesocosms) in open boxes and left them outside in Duke Forest – a Duke University research area in North Carolina – for 18 months. They added wetland plants typical to the southern United States. Mosquitofish and insects were accidentally introduced with the plants and soils. Other wild insects colonized the ecosystems. Many of the species completed their life cycles during the project.They regularly sampled the soil, water and fish to follow how the silver moved through the constructed environment. At the end, silver levels were analyzed in the soil, water, plants and animals – the fish, fish embryos and insects. They also measured distinct silver compounds to determine how the silver ions reacted with oxygen, sulfur and chlorine in the soils and water.Silver levels measured in the dosed plots were compared to the levels measured in the control plots where silver nanoparticles had not been applied.

 

 

What did they find?

Researchers found silver accumulated in both the terrestrial plants (up to 3 percent of the total added) and the aquatic animals.Plants growing in soil that had been dosed with nanoparticles had up to 18 parts per million silver while lower silver levels – ranging from 1 – 7 parts per million – were measured in the plants growing near the water that was dosed with the silver nanoparticles. In all cases, silver was measured in plants that started growing 6 months or more after the application of silver nanoparticles, indicating that the plants could absorb the silver from the soil.They also measured levels of silver in the fish and insects, which included mosquitofish, dragonfly larvae and midges. The mosquitofish had 20 – 30 times higher silver levels than fish in the control plots.More troubling were the high levels (10 – 20 times higher than control) of silver that passed from female mosquitofish to their developing embryos. However, the majority of the silver – about 70 percent of the total put into the systems – was recovered from the soils and the wetland sediments. In addition, for silver nanoparticles applied to the terrestrial environment, erosion and runoff carried some of the metal from the soils into the water where it mostly settled in the sediments.The silver nanoparticles reacted and changed after they were released, but differed between the terrestrial and water habitats. By the end of the study only 18 percent of the silver that was added to the water remained in the original form. The majority – 55 percent – had reacted with sulfur to form silver sulfide, while about 27 percent bound to the organic matter in the bottom sediment.Particles applied to the terrestrial environment were slightly less reactive. Forty-seven percent remained in the original form, while 52 percent reacted to form silver sulfide. These reactions happened more slowly than predicted by laboratory experiments, showing that lab studies do not always accurately predict what happens in the environment.

 

What does it mean?

In terrestrial soil and water, silver nanoparticles can chemically change and contaminate plants and animals with silver. Any health effects from exposures to the metal in this way are not known.The outdoor study from North Carolina is one of the first long term ones to examine how silver nanoparticles change in the environment, specifically in soils, sediments and water. It is also a first step to clarifying where the silver nanoparticles move to after they enter the environment. One surprise was that they tend to settle in the soil and in the sediments underwater.The researchers demonstrated that under realistic conditions the majority of the silver nanoparticles reacted with sulfur and oxygen, changing their structure and function. These newly created silver compounds can be more stable and less toxic than the silver nanoparticles.Over time, though, they may build up in the environment, providing relatively large quantities of silver that can be incorporated into plants and animals. These long-term reservoirs of silver in soils and sediments may lead to increased exposures. For example, silver was found in plants that started growing six months after the nanoparticles were applied.Once changed, the newly formed silver compounds migrated through the soil and water. Runoff and erosion also moved the metal compounds and the nanoparticles. Eventually, the silver was taken up by the plants, insects and fish living in the mock ecosystems.Silver also passed from the mother fish to her embryos. The transfer of contaminants from one generation to the next exposes the embryos early in development and can have long-term effects on health, reproduction and populations (Wu et al. 2010).The effects on plants and other animals in this study are still unknown. Previous research indicates silver can harm fish, clams and other aquatic species.A next step may be to determine if these exposures have any health effects on the species studied. Scientists will also need to determine the levels of silver nanoparticles released into the environment from consumer products. Initial results from a study done on socks containing silver nanoparticles show more than 50 percent of the silver escapes during the first few washings (Geranio et al. 2009). It will also be important to identify the levels of silver nanoparticles that remain intact after release and to understand plant and animal exposures.As more data become available, it may be important to evaluate which products will benefit most from having the silver nanoparticles and which ones may not be worth the risk they may pose to health and environment.(Audrey Bone, Doctoral Student, Duke University, Integrated Toxicology and Environmental Health Program contributed to this synopsis.)

 

Read more science at Environmental Heath News.

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Making Safer Products: A Chemical Design Protocol for Chemists

Wednesday, June 13th, 2012

AGC session at Green Chemistry & Engineering Conference 2012 

Tuesday, June 19, 3:20 -  5:20 / McKinley Room

 

Using Scientific Findings From the Environmental Health Sciences to Avoid Endocrine Disruption in the Chemical Design Process

Pete Myers, Environmental Health Sciences

Karen Peabody O’Brien, Advancing Green Chemistry

A central goal of green chemistry is to avoid hazard in the design of new chemicals. This objective is best achieved when information about a chemical’s potential hazardous effects is obtained as early in the design process as feasible. Endocrine disruption is a hazard that to date has been inadequately addressed by both industrial and regulatory science. To aid green chemists in avoiding this hazard, we propose an endocrine disruption testing protocol for use by green chemists in the design of new materials.

Endocrine Disrupting Chemicals – Principles of Endocrinology for Chemical Design and Public Health Protection.

R. Thomas Zoeller, Department of Biology, University of Massachusetts, Amherst

Epidemiological and experimental studies continue to show adverse effects of endocrine disrupting chemicals (EDCs) from exposure levels far below what risk assessments indicate are safe. Because EDCs interfere with hormone action, it is essential to design experiments and interpret their results in terms of the very large literature that informs us about the role of endocrine systems in health and disease. Principles of endocrinology important to this field include hormone-receptor interactions, the spatial and temporal characteristics of hormone action in relation to development and adult health, and the regulatory circuits that control delivery of hormones to the proper targets at the proper time. These principles should inform basic research and regulatory science as well as to guide chemists in the design of safe chemical products.

The Relationships Between Exposures to Endocrine Disrupting Chemicals and Adverse Human Health Effects.

Laura N. Vandenberg,

 Department of Biology and the Center for Regenerative and Developmental Biology, Tufts University

A growing number of studies overwhelmingly suggest that environmentally relevant doses of EDCs influence human health and disease. Hundreds of human and animal studies challenge traditional concepts in toxicology, in particular the dogma that “the dose makes the poison”, because EDCs can have effects at low doses that are not predicted by effects at higher doses.  Additionally, a large body of evidence indicates that hormones and EDCs produce non-monotonic dose responses (NMDRs), defined as non-linear relationships between dose and effect where the slope of the curve changes sign within the range of doses examined. These data indicate that the effects of low doses cannot be predicted by high dose studies. Thus, fundamental changes in how chemicals are tested are needed to protect human health.

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