Tag Archives: NIOSH

Lung injury, carbon nanotubes, and aluminum oxide

It’s pretty much undisputed that long, multi-walled carbon nanotubes (MWCNTs) are likely to present a serious health hazard given their resemblance to asbestos fibres. It’s a matter of some concern that has resulted in a US National Institute of Occupational Safety and Health (NIOSH) recommendation for workplace exposure to all carbon nanotubes that is stringent. (My April 26, 2013 posting features the recommendation.)

Some recent research from North Carolina State University (NCSU) suggests that there may be a way to make long, multi-walled carbon nanotubes safer. From an Oct. 3, 2014 news item on Nanowerk,

A new study from North Carolina State University and the National Institute of Environmental Health Sciences (NIEHS) finds that coating multiwalled carbon nanotubes (CNTs) with aluminum oxide reduces the risk of lung scarring, or pulmonary fibrosis, in mice.

“This could be an important finding in the larger field of work that aims to predict and prevent future diseases associated with engineered nanomaterials,” says James Bonner, a professor of environmental and molecular toxicology at NC State …

An Oct. 3, 2014 NCSU news release, which originated the news item, describes the research in a little more detail,

Multiwalled CNTs have a wide array of applications, ranging from sporting goods to electronic devices. And while these materials have not been associated with adverse health effects in humans, research has found that multi-walled CNTs can cause pulmonary fibrosis and lung inflammation in animal models.

“Because multiwalled CNTs are increasingly used in a wide variety of products, it seems likely that humans will be exposed to them at some point,” Bonner says. “That means it’s important for us to understand these materials and the potential risk they pose to human health. The more we know, the better we’ll be able to engineer safer materials.”

For this study, the researchers used atomic layer deposition to coat multiwalled CNTs with a thin film of aluminum oxide and exposed mice to a single dose of the CNTs, via inhalation.

The researchers found that CNTs coated with aluminum oxide were significantly less likely to cause pulmonary fibrosis in mice. However, the coating of aluminum oxide did not prevent lung inflammation.

“The aluminum oxide coating doesn’t eliminate health risks related to multi-walled CNTs,” Bonner says, “but it does lower them.”

Here’s a link to and a citation for the paper,

Atomic Layer Deposition Coating of Carbon Nanotubes with Aluminum Oxide Alters Pro-Fibrogenic Cytokine Expression by Human Mononuclear Phagocytes In Vitro and Reduces Lung Fibrosis in Mice In Vivo by Alexia J. Taylor, Christina D. McClure, Kelly A. Shipkowski, Elizabeth A. Thompson, Salik Hussain, Stavros Garantziotis, Gregory N. Parsons, and James C. Bonner. Published: September 12, 2014 DOI: 10.1371/journal.pone.0106870

This is an open access article.

The researchers offered this conclusion (part of the paper’s abstract),

These findings indicate that ALD [atomic layer deposition] thin film coating of MWCNTs with Al2O3 reduces fibrosis in mice and that in vitro phagocyte expression of IL-6, TNF-α, and OPN, but not IL-1β, predict MWCNT-induced fibrosis in the lungs of mice in vivo.

However, what I found most striking was this from the paper’s Discussion (section),

While the Al2O3 coating on MWCNTs appears to be the major factor that alters cytokine production in THP-1 and PBMCs in vitro, nanotube length is still likely an important determinant of the inflammatory and fibroproliferative effects of MWCNTs in the lung in vivo. In general, long asbestos fibers or rigid MWCNTs (i.e., >20 µm) remain in the lung and are much more persistent than shorter fibers or nanotubes [20]. Therefore, the nanotube fragments resulting from breakage of A-MWCNTs coated with 50 or 100 ALD cycles of Al2O3 would likely be cleared from the lungs more rapidly than uncoated long MWCNTs or those coated with only 10 ALD cycles of Al2O3. We observed that the fracturing of A-MWCNTs occurred only after sonication prior to administration to cells in vitro or mice in vivo. However, unsonicated A-MWCNTs could be more likely to fracture over time in tissues as compared to U-MWCNTs [uncoated]. We did not address the issue of A-MWCNT clearance before or after fracturing in the present study, but future work should focus the relative clearance rates from the lungs of mice exposed to A-MWCNTs in comparison to U-MWCNTs. Another potentially important consideration is whether or not ALD coating with Al2O3 alters the formation of a protein corona around MWCNTs. It is possible that differences in cytokine levels in the supernatants from cells treated with U- or A-MWCNTs could be due to differences in protein corona formation around functionalized MWCNTs that could modify the adsorptive capacity of the nanomaterial. Characterization of the protein corona and the adsorptive capacity for cytokines after ALD modification of MWCNTs should be another important focus for future work. [emphases mine]

In other words, researchers think coating long, MWCNTs with a certain type of aluminum might be safer due to its effect on various proteins and because coated MWCNTs are likely to fracture into smaller pieces and we know that short MWCNTs don’t seem to present a problem when inhaled.

Of course, there’s the research from Duke University (my Oct. 3, 2014 post) which suggests CNTs could present a different set of problems over time as they accumulate in the environment.

US National Insitute for Occupational Health and Safety issues report on strategies for handling nanomaterials

A Dec. 19, 2013 news item on Nanowerk announces the release of a recent publication about the safe handling of nanomaterials from the US National Institute of Occupational Health and Safety (NIOSH), Note: A link has been removed,

Occupational health risks associated with manufacturing and using nanomaterials are not yet clearly understood. However, initial toxicological data indicate that there is reason for caution. NIOSH is committed to promoting the responsible development and advancement of nanotechnology through its research and communication efforts to protect workers. NIOSH has taken a leading role in conducting research and making recommendations for nanotechnology safety in work settings. See the nanotechnology topic page for a list of documents and resources.

Recently, NIOSH has released a document titled, Current Strategies for Engineering Controls in Nanomaterial Production and Downstream Handling Processes, which provides information on how to control exposures for many of the most common processes seen in facilities that use or produce nanomaterials or nano-enabled products.

A Nov.8, 2013 NIOSH news release provides some additional insight into NIOSH’s strategy,,

Engineering controls are favored over administrative controls and personal protective equipment for lowering worker exposures, because they are designed to remove the hazard at the source, before it comes into contact with the worker. However, evidence showing the effectiveness of controls during the manufacture and downstream use of engineered nanomaterials in specific applications has been scarce.

The NIOSH recommendations fill a gap for science-based guidance that employers and workers can apply now, as research continues for better understanding of nanomaterial characteristics, and ways in which workers may be exposed, that may pose the risk of adverse health effects.

The consumer products market currently has more than 1,000 nanomaterial-containing products including makeup, sunscreen, food storage products, appliances, clothing, electronics, computers, sporting goods, and coatings. As more nanomaterials are introduced into the workplace and nano-enabled products enter the market, it is essential that producers and users of engineered nanomaterials ensure a safe and healthy work environment, the new document states.

Processes discussed in the document and for which controls are recommended and described include reactor operations and cleanout processes, small-scale weighing and handling of nanopowders, intermediate and finishing processes, and maintenance tasks. The document also includes recommendations for evaluating the performance of control technologies and control systems.

There’s a Dec. 9, 2013 NIOSH blog posting written by Jennifer L. Topmiller and Kevin H. Dunn which provides more detail about workers’ exposure to nanomaterials,,

Engineered nanomaterials are materials that are intentionally produced and have at least one primary dimension less than 100 nanometers (nm). Nanomaterials have properties different from those of larger particles of the same material, making them unique and desirable for specific product applications.  The consumer products market currently has more than 1,000 nanomaterial-containing products including makeup, sunscreen, food storage products, appliances, clothing, electronics, computers, sporting goods, and coatings [WWICS 2011].

It is difficult to estimate how many workers are involved in this field. By one estimate, there are 400,000 workers worldwide in the field of nanotechnology, with an estimated 150,000 of those in the United States [Roco et al. 2010]. The National Science Foundation has estimated that approximately 6 million workers will be employed in nanotechnology industries worldwide by 2020.

Occupational health risks associated with manufacturing and using nanomaterials are not yet clearly understood.  However, initial toxicological data indicate that there is reason for caution. NIOSH is committed to promoting the responsible development and advancement of nanotechnology through its research and communication efforts to protect workers. NIOSH has taken a leading role in conducting research and making recommendations for nanotechnology safety in work settings. …

The greatest exposures to raw nanomaterials are likely to occur in the workplace during production, handling, secondary processing, and packaging. In a review of exposure assessments conducted at nanotechnology plants and laboratories, Dr. Derk Brouwer determined that activities which resulted in exposures included harvesting (e.g., scraping materials out of reactors), bagging, packaging, and reactor cleaning [Brouwer 2010]. Downstream activities that may release nanomaterials include bag dumping, manual transfer between processes, mixing or compounding, powder sifting, and machining of parts that contain nanomaterials.  Similar to controlling hazards in traditional macro-scale manufacturing, engineering controls are recommended to reduce exposures to nanomaterials.

… Because little has been published on exposure controls in the production and use of nanomaterials, this document focuses on applications that have relevance to the field of nanotechnology and on engineering control technologies currently used, and known to be effective, in other industries.

Assessing how well the exposure control works is also essential for verifying that the exposure goals of the facility have been successfully met. This document covers a range of control evaluation tools including airflow visualization and measurement and containment test methods, such as tracer gas testing. Additional methods, such as video exposure monitoring, also provide information on critical task-based exposures and helps identify high-exposure activities and help provide the basis for interventions.

intriguingly, there’s also a plea for partnership at the end of this Dec. 9, 2013 NIOSH posting,

Producers and users of engineered nanomaterials are invited and encouraged to partner with NIOSH. Companies that have installed exposure controls, such as local exhaust ventilation, or are interested in assessing and reducing worker exposures can work with NIOSH engineers to develop and evaluate exposure mitigation options. Partnering with NIOSH not only benefits your company by providing an assessment of process emissions and recommending effective exposure control approaches  but also expands the knowledge base that benefits the industry as a whole.  Please feel free to contact us through the comment section below or by sending an e-mail to [email protected].  Thank for your interest in protecting workers!

You can find the NIOSH report, Current Strategies for Engineering Controls in Nanomaterial Production and Downstream Handling Processes here.

Shining a light on the women scientists at the US National Institute of Occupational Health and Safety (NIOSH)

A few days ago while researching another NIOSH (US National Institute of Occupational Health and Safety) story to be published later today, I stumbled across this Nov. 12, 2013 US National Institute of Occupational Health Safety (NIOSH) news release about their women and science video series,

The National Institute for Occupational Safety and Health (NIOSH) announces the availability of a new series of videos highlighting the stories of NIOSH women scientists. These “Women in Science” videos place the spotlight on the talented and diverse women researchers at NIOSH who provide encouragement for future occupational safety and health professionals, both men and women.

The development of world-class talent in science, technology, engineering, and mathematics (STEM) is critical to America’s global leadership. Scientists and policy makers see a particular need to engage young women in STEM careers, to address the fact that disproportionately fewer women than men currently work in STEM fields. These video spotlights touch upon the value placed by NIOSH on nurturing the rising generation of women scientists, and encouraging a new generation of scientific talent.

“At NIOSH, the mission of world-class research for preventing work-related injuries, illnesses, and deaths engages talented women, such as those highlighted in this series,” said NIOSH Director John Howard, M.D. “We hope the stories of these women will serve to encourage aspiring young scientists in their search for a field with which to serve.”

The “Women in Science” videos feature seven NIOSH scientists who share their personal journeys into various fields, describing interests while acknowledging duties, challenges, and balancing family life. The scientists include two epidemiologists, a U.S. Public Health Service officer and medical epidemiologist, a health communication specialist, a medical officer, a research civil and environmental health engineer, and a research psychologist. Between them are stories describing their career paths, the importance of research in protecting the American workforce, and advice for aspiring young scientists. Viewers will hear how a love of mystery books as a child led to a career as a “disease detective,” how adventures abroad were the driving force to a fulfilling career, how an experience with a severe head trauma patient guided the switch from neurosurgery to occupational medicine, and how research projects can involve breaking things and redesigning them to make them better.

A Nov. 13, 2013 posting by Alyssa Llamas (a Health Communication Specialist in the NIOSH Communication & Research Translation Office) on the NIOSH Science Blog gives the reasons for this video series (as for the fun facts included there, they weren’t quite as much fun as I hoped),

“When I grow up, I want to be an industrial hygienist.” Hearing a ten-year-old girl say those words would probably warrant a double take. While there might be some little girls out there dreaming about one day conducting research and working in a laboratory, studies suggest that more often, it’s a ten-year-old boy who will have the dream and will realize it when he grows up. The reality is that a disproportionately smaller number of women than men follow careers in science, technology, engineering, and math (STEM). Scientific organizations agree that a better balance is needed. Perhaps, when asked what they want to be when they grow up, more girls will one day enthusiastically say, “epidemiologist, health communication specialist, medical officer, engineer, psychologist!”

In order to remain competitive and innovative in science and technology, we must close the gender gap and harness the full potential of the female STEM workforce in the United States. …

You can find the videos on this NIOSH page titled, Science Speaks: A Focus on NIOSH Women in Science.

Gloves, Québec’s (Canada) Institut de recherche Robert-Sauvé en santé et en sécurité du travail, and a workplace nanotoxicity methodology report

A new report on a workplace health and safety issue in regard to nanoparticles (Development of a Method of Measuring Nanoparticle Penetration through Protective Glove Materials under Conditions Simulating Workplace Use)  was released in June 2013 by Québec’s Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST). Little research has been done on exposure through skin (cutaneous exposure), most research has focused on exposure by inhalation according to the report (en français version here),

In the workplace, the main pathway to NP exposure is inhalation (Ostiguy et al., 2008a). Exposure by the cutaneous route has not been studied much, partly because of the widely held belief that skin offers an impermeable barrier to NPs (Truchon et al., 2008). Yet a growing number of studies have pointed to the possible percutaneous absorption of NPs, such as in the case of skin damaged by abrasion (Zhang et al., 2008), repeated flexion (Rouse et al., 2007) or even through intact skin (Ryman-Rasmussen et al., 2006). Pores, hair follicles and sweat glands may also play a role in facilitating absorption of NPs through the skin (Hervé-Bazin, 2007). The nanoparticles are then carried throughout the body by the lymphatic circulatory system (Papp et al., 2008). Induced direct toxic effects have also been reported for epidermal keratinocyte cells exposed to carbon nanotubes and other types of NPs (Shvedova, 2003). [p. 17 PDF version; p. 1 print version; Note: See report bibliography for citations]

The researchers examined gloves made of four different types of material: nitrile, latex, neoprene, and butyl rubber under a number of different conditions. One type of nanoparticle was used for the study, titanium dioxide in powder and liquid forms. The report summary provides a bit more detail about the decision to develop a methodology and the testing methods,

With the exponential growth in industrial applications of nanotechnologies and the increased risk of occupational exposure to nanomaterials, the precautionary principle has been recommended. To apply this principle, and even though personal protective equipment against nanoparticles must be considered only as a last resort in the risk control strategy, this equipment must be available. To respond to the current lack of tools and knowledge in this area, a method was developed for measuring the penetration of nanoparticles through protective glove materials under conditions simulating workplace use.

This method consists of an experimental device for exposing glove samples to nanoparticles in powder form or in colloidal solution, while at the same time subjecting them to static or dynamic mechanical stresses and conditions simulating the microclimate in the gloves. This device is connected to a data control and acquisition system. To complete the method, a sampling protocol was developed and a series of nanoparticle detection techniques was selected.

Preliminary tests were performed using this method to measure the resistance of four models of protective gloves of different thicknesses made of nitrile, latex, neoprene and butyl to the passage of commercial TiO2 nanoparticles in powder form or colloidal solution. The results seem to indicate possible penetration of the nanoparticles in some types of gloves, particularly when subjected to repeated mechanical deformation and when the nanoparticles are in the form of colloidal solutions. Additional work is necessary to confirm these results, and consideration should be given to the selection of the configurations and values of the parameters that best simulate the different possible workplace situations. Nevertheless, a recommendation can already be issued regarding the need for regular replacement of gloves that have been worn, particularly with the thinnest gloves and when there has been exposure to nanoparticles in colloidal solution.

For interested parties, here’s a citation for and a link to the report (PDF),

Development of a Method of Measuring Nanoparticle Penetration through Protective Glove Materials under Conditions Simulating Workplace Use by Dolez, Patricia; Vinches, Ludwig; Perron, Gérald; Vu-Khanh, Toan; Plamondon, Philippe; L’Espérance, Gilles; Wilkinson, Kevin; Cloutier, Yves; Dion, Chantal; Truchon, Ginette
Studies and Research Projects / Report  R-785, Montréal, IRSST, 2013, 124 pages.

I last wrote about gloves and toxicity in a June 11, 2013 posting about gloves with sensors (they turned blue when exposed to toxic levels of chemicals). It would be interesting if they could find a way to create gloves with sensors that warn you when you are reaching dangerous levels of exposure through your gloves. Of course, first they’d have to determine what constitute a dangerous level of exposure. The US National Institute of Occupational Health and Safety (NIOSH) recently released its recommendations for exposure to carbon nanofibers and carbon nanotubes (my April 26, 2013 posting). In layperson’s terms, the recommended exposure is close to zero exposure. Presumably, the decision was based on the principle of being ‘safe rather than sorry’.

One final comment about exposure to engineered nanoparticles through skin, to date there has been no proof that there has been any significant exposure via skin. In fact, the first significant breach of the skin barrier was achieved for medical research, Chad Mirkin and his team at Northwestern University trumpeted their research breakthrough (pun intended) last year, from my July 4, 2012 posting,

Researchers at Northwestern University (Illinois, US) have found a way to deliver gene regulation technology using skin moisturizers. From the July 3, 2012 news item on Science Blog,

A team led by a physician-scientist and a chemist — from the fields of dermatology and nanotechnology — is the first to demonstrate the use of commercial moisturizers to deliver gene regulation technology that has great potential for life-saving therapies for skin cancers.

The topical delivery of gene regulation technology to cells deep in the skin is extremely difficult because of the formidable defenses skin provides for the body. The Northwestern approach takes advantage of drugs consisting of novel spherical arrangements of nucleic acids. These structures, each about 1,000 times smaller than the diameter of a human hair, have the unique ability to recruit and bind to natural proteins that allow them to traverse the skin and enter cells.

This goes a long way to explaining why primary occupational health and safety research has focused on exposure via inhalation rather than skin.  That said, I think ensuring safety means minimizing exposure by all routes until more is known about the hazards.

No more carbon nanotubes from Bayer MaterialScience

A May 8, 2013 news item on Nanowerk proclaims,

Bayer MaterialScience intends to focus its development activities more intently on topics that are closely linked to its core business. For that reason the company will bring its work on carbon nanotubes (CNTs) to a close. Precisely how the research results and know-how for the production and application CNT will be used further will be determined shortly.

Researchers from Bayer MaterialScience had collaborated with external partners in recent years to resolve complex issues related to the safe production of specific carbon nanotubes. [emphasis mine] Methods for scaling up the production processes were developed, as were new generations of catalysts and new types of products.

The timing for this announcement from Bayer MateriaScience is interesting given that the US National Institute of Occupational Health and Safety (NIOSH) just announced some stringent recommendations (almost zero) for occupational exposure to carbon nanofibers and carbon nanotubes (my Apr. 28, 2013 posting).

The May 8, 2013 Bayer MaterialScience news release, which originated the news item, provides more detail about the business decision,

Much of the knowledge gleaned over recent years was made available to other companies and research institutions within the Innovation Alliance Carbon Nanotubes (Inno.CNT), which counts Bayer MaterialScience among its roughly 90 members.

“We remain convinced that carbon nanotubes have huge potential,” says Patrick Thomas, Chief Executive Officer of Bayer MaterialScience. It has been found, however, that the potential areas of application that once seemed promising from a technical standpoint are currently either very fragmented or have few overlaps with the company’s core products and their application spectrum.

“For Bayer MaterialScience, groundbreaking applications for the mass market relating to our own portfolio and therefore comprehensive commercialization are not likely in the foreseeable future,” says Thomas. Nonetheless, this know-how provides an important basis for a possible later use of CNT, for example in the optimization of lithium ion batteries, Thomas says. “We are currently in contact with potential interested parties regarding the specific application of the know-how generated,” Thomas adds.

The conclusion of the nano projects has no impact on the headcount. All 30 people employed in this sector will be transferred to other suitable positions within the Group.

I”m glad to hear no one will lose their job.

Finally, I recall reading somewhere that there was a glut of carbon nanotube production and taking that with the recent NIOSH recommendation and Bayer’s claim of poor prospects for commercialization, it seems like one of those decisions that made itself.

ETA May 20, 2013: Dexter Johnson provides some insight into carbon nanotube production and the glut in his May 18, 2013 posting on Nanoclast (on the IEEE [Institute of Electrical and Electronics Engineers] website),

This [Bayer MaterialScience decision] is no surprise since there was a huge glut of product resulting in industry utilization rates that must have been in the single digits. This oversupplied market was the result of a MWNT [multi-walled nanotube] capacity arms race that started in the mid-2000s.

I recommend reading the rest of the posting where Dexter goes on to describe how pricing dropped precipitously from 2006 to 2009  and the resultant efforts to develop markets for the product.

US National Institute of Occupational Health and Safety sets recommendations for workplace exposure to carbon nanofibers/nanotubes

Earlier this week, the US National Institute of Occupational Health and Safety (NIOSH) set recommendations for workplace exposure to carbon nanotubes and carbon nanofibers. According to the Apr. 24, 2013 media advisory from the US Centers for Disease Control and Prevention (NIOSH’s parent agency), the recommendations have been issued in the new Current Intelligence Bulletin (CIB) no. 65. From CIB No. 65,

NIOSH is the leading federal agency conducting research and providing guidance on the occupational safety and health implications and applications of nanotechnology. As nanotechnology continues to expand into every industrial sector, workers will be at an increased risk of exposure to new nanomaterials. Today, nanomaterials are found in hundreds of products, ranging from cosmetics, to clothing, to industrial and biomedical applications. These nanoscale-based products are typically called “first generation” products of nanotechnology. Many of these nanoscale-based products are composed of engineered nanoparticles, such as metal oxides, nanotubes, nanowires, quantum dots, and carbon fullerenes (buckyballs), among others. Early scientific studies have indicated that some of these nanoscale particles may pose a greater health risk than the larger bulk form of these materials.

Results from recent animal studies indicate that carbon nanotubes (CNT) and carbon nanofibers (CNF) may pose a respiratory hazard. CNTs and CNFs are tiny, cylindrical, large aspect ratio, manufactured forms of carbon. There is no single type of carbon nanotube or nanofiber; one type can differ from another in shape, size, chemical composition (from residual metal catalysts or functionalization of the CNT and CNF) and other physical and chemical characteristics. Such variations in composition and size have added to the complexity of understanding their hazard potential. Occupational exposure to CNTs and CNFs can occur not only in the process of manufacturing them, but also at the point of incorporating these materials into other products and applications. A number of research studies with rodents have shown adverse lung effects at relatively low-mass doses of CNT and CNF, including pulmonary inflammation and rapidly developing, persistent fibrosis. Although it is not known whether similar adverse health effects occur in humans after exposure to CNT and CNF, the results from animal research studies indicate the need to minimize worker exposure.

This NIOSH CIB, (1) reviews the animal and other toxicological data relevant to assessing the potential non-malignant adverse respiratory effects of CNT and CNF, (2) provides a quantitative risk assessment based on animal dose-response data, (3) proposes a recommended exposure limit (REL) of 1 μg/m3 elemental carbon as a respirable mass 8-hour time-weighted average (TWA) concentration, [emphasis mine] and (4) describes strategies for controlling workplace exposures and implementing a medical surveillance program. The NIOSH REL is expected to reduce the risk for pulmonary inflammation and fibrosis. However, because of some residual risk at the REL and uncertainty concerning chronic health effects, including whether some types of CNTs may be carcinogenic, continued efforts should be made to reduce exposures as much as possible.

The recommended exposure, for those of us who can’t read the technical notation, translates to one microgram per cubic meter per eight-hour workday.  In other words, almost zero. Note that this is a recommendation and not a regulation. H/T Apr. 26, 2013 article by Elizabeth Wiese for USA Today

My Mar. 12, 2013 posting highlights some of the NIOSH research which preceded this recommendation.

The long, the short, the straight, and the curved of them: all about carbon nanotubes

I implied a question in my Mar. 12, 2013 post about the recent announcement from the US National Institute of Occupational Health and Safety (NIOSH) concerning a carbon nanotube toxicity study. I indicated some curiosity about the length of the multi-walled carbon nanotubes studied in this latest research. Coincidentally, Dr. Andrew Maynard (Executive Director of the University of Michigan Risk Science Center answered this implied question in his Mar. 14, 2013 posting about the study (on Andrew’s 2020 Science blog),

The carbon nanotubes in this study were inhaled multi-walled carbon nanotubes with a predominantly long, straight fiber-like morphology.  Mice were exposed at a level of 5 mg/m3 for 5 hours per day, over a 15 day period.

It’s well worth reading Andrew’s posting for the context he provides about the research and for links to further information.

For anyone who wants the short story, multi-walled carbon nanotubes (predominantly the long, straight fibre-type were used in the study) when combined with a known cancer-initiating chemical are more toxic than plain carbon nanotubes. The study has yet to be published but the results were discussed at the Society of Toxicity’s 2013 annual meeting.

Happily, he also provides this charming video (part of his Risk Bites video series) describing carbon nanotubes and their ‘infinite’ variety,

Thank you Andrew for clearing up some of my longstanding questions about carbon nanotubes.

Happy weekend to all!

Multi-walled carbon nanotubes, cancer, and the US National Institute of Occupational Health and Safety’s (NIOSH) latest findings

A Mar. 11, 2013 news item on Nanowerk reveals some of the latest research performed by US National Institute of Occupational Health Safety (NIOSH) researchers into the question of whether or not multi-walled carbon nanotubes (MWCNT) cause cancer,

Earlier today, at the annual meeting of the Society of Toxicology, NIOSH researchers reported preliminary findings from a new laboratory study in which mice were exposed by inhalation to multi-walled carbon nanotubes (MWCNT). The study was designed to investigate whether these tiny particles have potential to initiate or promote cancer. By “initiate,” we mean the ability of a substance to cause mutations in DNA that can lead to tumors. By “promote,” we mean the ability of a substance to cause cells that have already sustained such DNA mutations to then become tumors.

It is very important to have new data that describe the potential health hazards that these materials might represent, so that protective measures can be developed to ensure the safe advancement of nanotechnology in the many industries where it is being applied.

The Mar. 11, 2013 posting (which originated the news item) by Vincent Castranova, PhD; Charles L Geraci, PhD; Paul Schulte, PhD  on the NIOSH blog provides details about the experimental protocols and the outcome of the experiments,

In the NIOSH study, a group of laboratory mice were injected with a chemical that is a known cancer initiator, methylcholanthrene.  Another group of mice were injected with a saline solution as a control group.  The mice then were exposed by inhalation either to air or to a concentration of MWCNT.   These protocols enabled the researchers to investigate whether MWNCT alone would initiate cancer in mice, or whether MWCNT would promote cancer where the initiator, methylcholanthrene, had already been applied.

Mice receiving both the initiator chemical plus exposure to MWCNT were significantly more likely to develop tumors (90% incidence) and have more tumors (an average of 3.3 tumors/mouse lung) than mice receiving the initiator chemical alone (50% of mice developing tumors with an average of 1.4 tumors/lung).  Additionally, mice exposed to MWCNT and to MWCNT plus the initiator chemical had larger tumors than the respective control groups.  The number of tumors per animal exposed to MWCNT alone was not significantly elevated compared with the number per animal in the controls.  These results indicate that MWCNT can increase the risk of cancer in mice exposed to a known carcinogen.  The study does not suggest that MWCNTs alone cause cancer in mice.

That last sentence is quite important because (from the NIOSH blog post),

Several earlier studies in the scientific literature indicated that MWCNT could have the potential to initiate or promote cancer. The new NIOSH study is the first to show that MWCNT is a cancer promoter in a laboratory experiment, and reports the growth of lung tumors in laboratory mice following inhalation exposure to MWCNT rather than injection, instillation, or aspiration.  Inhalation exposure most closely resembles the exposure route of greatest concern in the workplace. In the study, laboratory mice were exposed to one type of MWCNT through inhalation at a concentration of 5 milligrams per cubic meter of air for five hours per day for a period of 15 days.

Risk of occupational cancer depends on the potency of a given substance to cause or promote cancer and the concentration and duration of worker exposure to that substance.  This research is an important step in our understanding of the hazard associated with MWCNT, but before we can determine whether MWCNT pose an occupational cancer risk, we need more information about actual exposure levels and the types and nature of MWCNT being used in the workplace, and how that compares to the material  used in this study.

This study is part of a larger program designed to establish safety practices with regard to handling nanomaterials/nanoparticles (from the NIOSH blog post),

These laboratory studies are part of a strategic program of NIOSH research to better understand the occupational health and safety implications of nanoparticle exposure, and to make authoritative science-based recommendations for controlling exposures so that the technology is developed responsibly as the research advances, and the societal benefits of nanotechnology can be realized.  NIOSH has worked closely with diverse public and private sector partners over the past decade to incorporate occupational health and safety into practical strategies for safe development of this revolutionary technology. More information is available on the NIOSH nanotechnology topic page.

There is no mention in the blog post as to whether the MWCNTs in this latest work were long or short or a mixture of both. Unfortunately, the study has not yet been published in a journal, so it’s not yet available for reading purposes. I did mention carbon nanotubes and toxicity in a Jan. 16, 2013 posting about a recent study,

Researchers at the University College of London (UCL), France’s Centre national de la recherche scientifique (CNRS), and Italy’s University of Trieste have determined that carbon nanotube toxicity issues can be addressed be reducing their length and treating them chemically.

While I find this latest work from NIOSH interesting, it’s hard for me to understand why there’s no mention of length. Unless, the NIOSH work is focused on what happens when MWCNTs are inhaled along with known cancer initiators and they believe that length is not a factor.

ETA Mar. 15, 2013: I did find get some information about the length (long carbon nanotubes for the most part) as per this Mar. 14, 2013 posting or you can find the update in my Mar. 15, 2013 posting here.

‘Safe’ nano, a report covering US National Institute of Occupational Health and Safety activities from 2004 to 2011

The Nov. 9, 2012 news item on Nanowerk lists the report title as “Filling the Knowledge Gaps for Safe Nanotechnology in the Workplace“,

In 2007 and 2009, NIOSH [US National Institute of Occupational Safety and Health] published progress reports detailing the accomplishments of the NTRC [Nanotechnology Research Center], including the results of ongoing laboratory and field research and the publication of technical and other guidance documents on the safe handling of engineered nanomaterials (see Progress Toward Safe Nanotechnology in the Workplace, www.cdc.gov/niosh/topics/nanotech/pubs.html).

This 2012 update presents the program accomplishments of the NTRC from its inception in 2004 through 2011. It includes an analysis of the progress made toward accomplishing the goals and objectives of the NIOSH Strategic Plan for Nanotechnology Research and toward addressing the goals and research needs identified in the U.S. National Nanotechnology Initiative (NNI) Environmental, Health, and Safety (EHS) research strategy.

The report  is approximately 400 pp. most of which are devoted to descriptions of various projects, both completed and currently underway. The actual report comes in at roughly 65 pp.  I find the cover art to be particularly interesting given my interest in data visualization,

“Filling the Knowledge Gaps for Safe Nanotechnology in the Workplace” cover: A graphical representation of the reach of a highly cited NIOSH journal article specific to nanomaterials. The scatter plot illustrates the initial publication (red dot) surrounded by the number of times it was directly cited in other papers (primary citations are yellow dots) and then the number of times the primary citation papers were cited by other papers (secondary citations are white dots). This diagram was developed using Cytoscape, an open source platform for complex network analysis and visualization.

For those who don’t fancy reading the report, here’s a list of the accomplishments from the report’s Executive Summary (p. 8-9 PDF version),

Summary of NTRC Program Outputs and Impacts

Among the many program outputs and impacts, the NTRC researchers:

■ Developed some of the earliest guidance on the design and conduct of nano­toxicology studies.

■ Identified pulmonary and cardiovascular hazards of some types of carbon nano­tubes in animals.

■ Determined that the dispersion of ultrafine carbon black nanoparticles in the lungs of rats following intratracheal instillation results in an inflammatory response that is greater than agglomerated ultrafine carbon black.

■ Determined that ultrafine TiO2 or carbon black is more inflammogenic than fine TiO2 or carbon black on a mass-dose basis.

■ Developed a system to generate nanoparticle aerosols for inhalation toxico­logic studies.

■ Conducted over 40 field assessments in nanomaterial manufacturer and user facilities.

■ Produced more than 400 peer-reviewed scientific publications, resulting in over 5,000 primary and 82,000 secondary citations.

■ Provided over 650 invited presentations.

■ Published a framework for conducting workplace emission testing.

■ Developed innovative sampling methods for engineered nanomaterials.

■ Contributed to the development of a bio-mathematical model in rats to describe clearance, retention, and translocation of inhaled nanoparticles throughout the body.

■ Developed recommended exposure limits (RELs) for TiO2 and carbon nano­tubes (CNTs) and carbon nanofibers (CNFs).

■ Developed interim guidance for medical screening and hazard surveillance.

■ Identified what research will be needed to ensure the health of workers han­dling nanomaterials.

■ Established formal partnerships and collaborations with private, governmen­tal and academic centers in the U.S. and globally.

■ Co-chaired the NNI Nanotechnology Environmental and Health Implications (NEHI) Working Group and contributed significantly to the development of the 2011 NEHI environmental health and safety (EHS) strategy.

■ Chaired the Organization for Economic Cooperation and Development (OECD) Working Party on Manufactured Nanomaterials Steering Group 8 on exposure measurement and exposure mitigation for manufactured nanomaterials.

■ Provided widely used guidance on responsible development of nanotechnology.

■ Helped to establish the U.S. and international position that a precautionary approach to controlling exposures to engineered nanoparticles is warranted.

■ Have shown how responsible nanotechnology development and worker safety and health can be achieved.