Tag Archives: green design

Shorter fibers: key to safer carbon nanotubes?

Synopsis by Marty Mulvihill Feb 05, 2013

Ali-Boucetta, H, A Nunes, R Sainz, MA Herrero, B Tian, M Prato, A Bianco and K Kostarelos, 2013. Asbestos-like pathogenicity of long carbon nanotubes alleviated by chemical functionalization, Angewandte Chemie International Edition http://dx.doi.org/10.1002/anie.201207664.

A shorter carbon nanotube may be a safer one, according to a group of European researchers who varied the materials’ structural fibers and tested their health effects in mice.

Carbon nanotubes are one of the most common and exciting examples of nanotechnology with potential uses in electronics and medicine, but they are made of fibers that resemble asbestos. The modified nanotubes with shorter fibers were less irritating to the mouse lung and showed no signs of cancer when compared to traditional carbon nanotubes.

This work demonstrates the importance of researchers from different disciplines teaming up to solve problems. When applied to green chemistry, toxicologists and chemists working together can create safer materials to help avoid unintended health and environmental consequences of new chemicals.

Many scientists predict that carbon nanotubes will have many useful applications. The nanomaterials could boost performance of our electronic devices, deliver drugs directly to cells and even enable more affordable space travel through lighter materials.

At the same time, other scientists and health experts worry that carbon nanotubes could create health problems in people. In particular, the fibrous structure of these tubes closely resembles the potent carcinogen asbestos. In fact, lab and animal studies have shown that carbon nanotubes do irritate lung tissue in the same way and lead to lung cancer in exposed animals.

Asbestos has been used in building materials, auto parts and coatings as an insulator and fire retardant. Asbestos fibers are released when products containing asbestos age or are disturbed in remodeling or replacement. When breathed in, the fibers can irritate lung tissue, causing cancer and other lung disease.

Now, a group of scientists report that they can make carbon nanotubes – picture sheets of carbon rolled into a cylinder – that are much safer and have fewer asbestos-like health effects.

By chemically modifying the surface of the very small carbon nanotubes, the researchers created fibers that are 10 times shorter than typical nanotube fibers. They tested these new materials head-to-head in mice with both untreated nanotubes and asbestos fibers.

They found that the chemical treatment produces fibers that caused much less irritation in the mouse lungs and did not show signs of cancer development during the seven days after injecting the nanotubes into the lungs.

More work and further testing are needed to understand the long-term impact of the modified nanotubes, including more details about biological interactions with the new nanomaterials.

 

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The above work by Environmental Health News is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.
Based on a work at www.environmentalhealthnews.org.

New Tools to Design Safer Chemicals

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.

 

 

Silver speeds chemical reactions with oxygen.

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.

Bacteria detox process gives insight for safer chemicals.

Teufel, R, T Friedrich and G Fuchs. 2012. An oxygenase that forms and deoxygenates toxic epoxideNature 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.

green bubbles beakers

Making Safer Products: A Chemical Design Protocol for Chemists

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.

Pie Chart

Analysis of Green Chemistry publications over the past four years.

This figure is taken from Green chemistry: state of the art through an analysis of the literature by V. Dichiarante, D. Ravelli and A. Albini. Green Chemistry Letter and Reviews Vol. 3, No. 2, June 2010, 105-113.

 

As the label indicates, the pie chart shows a distribution of green chemistry topics as analyzed by articles produced in the year 2008. The majority of the pie chart (about 50%) is attributed to catalysis – or starting a reaction, under more favorable conditions that require less resources, whether those resources are heat, energy, reagents etc. Specifically, metal catalysts were the most cited catalysts used in many different reactions, specifically in those involving enzymes. Acids are also seen in this category, and according to the article, are used mainly in condensation reactions. The next largest section of the pie (about 40%) is attributed to media, or where/in what the reaction takes place. Many reactions require some liquid for a reaction to take place. Many of these liquids, especially in organic chemistry, are volatile or toxic compounds. As a result, most of the research done with green chemistry and the media of reactions use either no solvent, which allows for most reduction of waste. Water has also gained a prominent role in green chemistry literature as it is our universal solvent and usually can be recycled in a reaction. Ionic liquids are the third major media hit; they are liquids that have charged compounds in the solution to help guide a reaction. Ionic liquids are usually not volatile and are stored more easily compared to their organic counterparts. Finally, the last 10% of the pie chart goes to ‘new methods,’ or novel ways to do old reactions. Using microwaves to start and maintain a reaction is the most prominent method, followed by some research advances in photochemistry and ultrasounds, using light or sound respectively in reactions.

Ford Looks to Dandelions for Natural Rubber

By Jonathan Bardelline
Published in GreenBiz.com May 11, 2011

Ford Looks to Dandelions for Natural Rubber
DEARBORN, MI — Ford continues to diversify its research into plant-based materials by turning a common weed into a replacement for synthetic rubber.

The company has already introduced soy foam and wheat straw components into its vehicles. Now, it’s looking to produce cup holders, floor mats and other parts with the help of dandelions.

Through work with Ohio State University, Ford will make and test car components created with rubber derived from the Russian dandelion, Taraxacum kok-saghyz. OSU’s Ohio Agricultural Research and Development Center is growing the dandelion, which produces a milky-white substance from its roots that can be turned into rubber.

Debbie Milewski, technical leader of Ford’s plastics research group, said the dandelion rubber will be used in parts that are part-plastic, part-rubber. That includes materials all over the interiors of cars like plastic trim as well as exterior parts like bumper covers. Some of those components have rubber content up to 40-50 percent.

Before dandelion-based cup holders find their way into cars, Ford will test how the rubber performs with different plastics to make sure it meets durability requirements.

“We’re going to look at a wide range of plastics and then we’ll narrow the scope from there,” Milewski said. The timeframe for getting the new rubber into vehicles depends on what issues crop up during testing. Soy foam, which is now in seats for every vehicle sold in North America, took six years of development, while the wheat straw bins went from concept to implementation in 18 months.

The dandelion-based rubber has the potential to find its way into any part that currently includes rubber, and Milewski said Ford might even try making parts completely from the natural rubber. The change would not only shift Ford away from petroleum-based synthetic rubber, but also use a plant source that can grow easily in the United States.

OSU’s research on making rubber from the Russian dandelion was a continuation of work done by a Russian university, Milewski said. Ford got involved after a local Ford car dealer near OSU, who knew about the company’s other bio-materials work, heard about the project and wrote to Executive Chairman Bill Ford about it, she said.

As part of Ford’s overall plan to make vehicles lighter and explore alternative materials, the company has also created fabrics out of recycled plastic bottles and engine cylinder head covers from recycled carpet.

Dandelions at OSU – Courtesy Ford

Chemists, biologists collaborate to design endocrine disrupter screening tool.

01-Apr-2011

As part of an unprecedented collaboration in the US between environmental health scientists and synthetic chemists, a working meeting was held last week as part of an ongoing project to create a design protocol to screen new materials for endocrine disrupting activity. Hosted by the non-profit organisations, Advancing Green Chemistry and Environmental Health Sciences, the meeting brought together about two dozen leading researchers in fields that include molecular biology, endocrinology, genetics, and green chemistry to create a screening tool to be used as new chemicals are being synthesized with the goal of detecting potential biological activity before a new compound goes into commercial production.

While endocrine disruption has been recognised as a health hazard for more than two decades, no screening tool comparable to the one this group of scientists is developing currently exists. To be effective at detecting endocrine disrupting activity, an assay would have to take into account potential low dose and non-linear effects of chemicals and the many possible interactions such chemicals can have with genetic receptors. The goal of the project is to produce a suite of peer-reviewed assays for synthetic chemists, the great majority of whom are not trained in biology, endocrinology or toxicology. The protocol is being designed for use in both commercial and academic laboratories.

“In the US, there has been a 15-plus year effort underway at the EPA (Environmental Protection Agency), which has still not come out with a comprehensive testing protocol for endocrine disruption,” said Karen Peabody O’Brien, executive director of Advancing Green Chemistry. “Rather than wait for regulation of what is already in use, this group is putting together a design tool for chemists who are trying to create the next generation of safer materials or ‘greener’ chemicals. We are not trying to regulate industry but give chemists the means to find out well in advance whether they are making something that, to the best of our knowledge, is not biologically active,” explained Dr O’Brien.

She stressed that this is the first toxicological screening tool to be developed by such a cross-disciplinary team of scientists and that the intent is to provide chemists with a way to establish confidence that new materials – particularly alternatives to existing problematic chemicals – are safe.

Article underestimates challenges of marrying chemical design and toxicology.

Posted by Audrey Moores at Mar 31, 2011 06:00 AM | Permalink

An article entitled “Better by Design“ and published in Science News on March 26th describes the recent progress made by chemists towards the design of safer chemicals. The article features a computer-based study by a group of Yale chemists who demonstrated that toxicity of a molecule is strongly correlated with a small number of chemical and physical properties. This research study suggests that we soon will be able to quickly assess the potential toxic risk associated with a molecule – all from its chemical formula. The hope is to build a predictive tool to design inherently safer chemicals from the moment chemists first start to think about them.

The Science News article does a good job of describing the importance of designing chemicals for everyday use that will not present environmental health problems. It also explains in an approachable fashion, some of the ways molecules can interfere with the body. However, two important aspects of the challenge chemical design represents for chemists may be lost.

First, understanding the potency of a molecule at the design level is achievable, as some of the works highlighted in the article suggest. However it is still difficult and not yet entirely possible for all molecules, especially brand new ones. The chemistry community still regards it as an immense challenge to design molecules possessing biological activity – for drug discovery for instance. It is equally complex to predict a desired absence of biological potency. It goes far beyond simply looking at a molecule’s drawing. It requires specialized computer software and databases, as well as lab and animal tests.

Why? Because a compound may be harmful for many combined reasons. The article accurately lists some of them. A compound may interact with the body, for instance, through binding with a specific protein. When it does so, it may trigger undesired body responses, such as an earlier puberty in the case of BPA. This interaction is like a key-lock interaction, where the global shape of the key and the position of each indentation count. So that when chemists design a new molecule for making a plastic wrap, for instance, they should verify that it is not also a key that unlocks an unwanted protein reaction. This task is gigantic, despite what the article suggests. Only a computer program could achieve it reliably.

Second, chemists have by training a limited knowledge of molecular toxicity. There is a tendency for scientists to specialize, and chemists have followed that path. For example, biology is hardly taught in any chemistry curriculum – which mainly concentrates on chemical reactions with a target product in mind. Students are not taught where starting materials are coming from and where molecules go after use. A true paradigm shift is needed to ensure the next generation of chemists can embrace the complexity of the problem of molecule design. The article completely skipped this issue.

In general, the article would be more powerful, and maybe more approachable, if it had provided a vision of how in the future chemists could use tools to design molecules. When chemists first think about a molecule and draw its structure they could consult the program to get an estimation of how potent it can be. With this information, chemists could refrain from even making a molecule that could prove harmful in the long run.

While the article covers an important development in chemistry, it would be better if the reporter had put this work into perspective. Using computers to predict biological activity is a good step, but is just one of many methods developed.

BPA: What’s the alternative?

Posted by Evan Beach at Nov 12, 2010 03:30 PM | Permalink

Science News and other outlets reporting on BPA-free receipts identify for the first time a substitute chemical being used by one of the largest manufacturers of thermal paper. It has been referred to incorrectly in blogs as “bisphenol sulfonate” or “diphenyl sulfone,” but it is actually a chemical known as bisphenol S (Update, 11/15/10: 4,4′-sulfonylbisphenol). As the name indicates, it is structurally very similar to bisphenol A (BPA). And although it has not been studied as much as BPA, preliminary studies show that it shares hormone-mimicking properties as well.

In 2005, a group of Japanese scientists compared BPA and 19 other related compounds for their ability to mimic the female hormone estrogen. They tested the effects on human cells and found that bisphenol S was slightly less potent than BPA, but not by much: bisphenol S was active at 1.1 micromolar concentration, BPA at 0.63 micromolar. One micromolar is roughly equivalent to a packet of sugar in 3,000 gallons of water.

Other researchers have found that bisphenol S is much less biodegradable than BPA. In their study of eight bisphenol compounds, bisphenol S was the most persistent.

While much more is known about the effects of BPA – particularly at ultra-low doses – the existing data on bisphenol S suggests the substitution should be made with caution. Hormone-mimicking behavior and environmental persistence are intrinsic hazards that should be avoided. As the Science News story mentions, an assessment by the U.S. Environmental Protection Agency’s Design for the Environment program may shine more light on the matter.