Tag Archives: aerosols

Canadian research into nanomaterial workplace exposure in the air and on surfaces

An August 30, 2018 news item on Nanowerk announces the report,

The monitoring of air contamination by engineered nanomaterials (ENM) is a complex process with many uncertainties and limitations owing to the presence of particles of nanometric size that are not ENMs, the lack of validated instruments for breathing zone measurements and the many indicators to be considered.

In addition, some organizations, France’s Institut national de recherche et de sécurité (INRS) and Québec’s Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST) among them, stress the need to also sample surfaces for ENM deposits.

In other words, to get a better picture of the risks of worker exposure, we need to fine-tune the existing methods of sampling and characterizing ENMs and develop new one. Accordingly, the main goal of this project was to develop innovative methodological approaches for detailed qualitative as well as quantitative characterization of workplace exposure to ENMs.

A PDF of the 88-page report is available in English or in French.

An August 30, 2018 (?) abstract of the IRSST report titled An Assessment of Methods of Sampling and Characterizing Engineered Nanomaterials in the Air and on Surfaces in the Workplace (2nd edition) by Maximilien Debia, Gilles L’Espérance, Cyril Catto, Philippe Plamondon, André Dufresne, Claude Ostiguy, which originated the news item, outlines what you can expect from the report,

This research project has two complementary parts: a laboratory investigation and a fieldwork component. The laboratory investigation involved generating titanium dioxide (TiO2) nanoparticles under controlled laboratory conditions and studying different sampling and analysis devices. The fieldwork comprised a series of nine interventions adapted to different workplaces and designed to test a variety of sampling devices and analytical procedures and to measure ENM exposure levels among Québec workers.

The methods for characterizing aerosols and surface deposits that were investigated include: i) measurement by direct-reading instruments (DRI), such as condensation particle counters (CPC), optical particle counters (OPC), laser photometers, aerodynamic diameter spectrometers and electric mobility spectrometer; ii) transmission electron microscopy (TEM) or scanning transmission electron microscopy (STEM) with a variety of sampling devices, including the Mini Particle Sampler® (MPS); iii) measurement of elemental carbon (EC); iv) inductively coupled plasma mass spectrometry (ICP-MS) and (v) Raman spectroscopy.

The workplace investigations covered a variety of industries (e.g., electronics, manufacturing, printing, construction, energy, research and development) and included producers as well as users or integrators of ENMs. In the workplaces investigated, we found nanometals or metal oxides (TiO2, SiO2, zinc oxides, lithium iron phosphate, titanate, copper oxides), nanoclays, nanocellulose and carbonaceous materials, including carbon nanofibers (CNF) and carbon nanotubes (CNT)—single-walled (SWCNT) as well as multiwalled (MWCNT).

The project helped to advance our knowledge of workplace assessments of ENMs by documenting specific tasks and industrial processes (e.g., printing and varnishing) as well as certain as yet little investigated ENMs (nanocellulose, for example).

Based on our investigations, we propose a strategy for more accurate assessment of ENM exposure using methods that require a minimum of preanalytical handling. The recommended strategy is a systematic two-step assessment of workplaces that produce and use ENMs. The first step involves testing with different DRIs (such as a CPC and a laser photometer) as well as sample collection and subsequent microscopic analysis (MPS + TEM/STEM) to clearly identify the work tasks that generate ENMs. The second step, once work exposure is confirmed, is specific quantification of the ENMs detected. The following findings are particularly helpful for detailed characterization of ENM exposure:

  1. The first conclusive tests of a technique using ICP-MS to quantify the metal oxide content of samples collected in the workplace
  2. The possibility of combining different sampling methods recommended by the National Institute for Occupational Safety and Health (NIOSH) to measure elemental carbon as an indicator of NTC/NFC, as well as demonstration of the limitation of this method stemming from observed interference with the black carbon particles required to synthesis carbon materials (for example, Raman spectroscopy showed that less than 6% of the particles deposited on the electron microscopy grid at one site were SWCNTs)
  3. The clear advantages of using an MPS (instead of the standard 37-mm cassettes used as sampling media for electron microscopy), which allows quantification of materials
  4. The major impact of sampling time: a long sampling time overloads electron microscopy grids and can lead to overestimation of average particle agglomerate size and underestimation of particle concentrations
  5. The feasibility and utility of surface sampling, either with sampling pumps or passively by diffusion onto the electron microscopy grids, to assess ENM dispersion in the workplace

These original findings suggest promising avenues for assessing ENM exposure, while also showing their limitations. Improvements to our sampling and analysis methods give us a better understanding of ENM exposure and help in adapting and implementing control measures that can minimize occupational exposure.

You can download the full report in either or both English and French from the ‘Nanomaterials – A Guide to Good Practices Facilitating Risk Management in the Workplace, 2nd Edition‘ webpage.

Study nanomaterial toxicity without testing animals

The process of moving on from testing on animals is laborious as new techniques are pioneered and, perhaps more arduously, people’s opinions and habits are changed. The People for the Ethical Treatment of Animals (PETA) organization focusing the research end of things has announced a means of predicting carbon nanotube toxicity in lungs according to an April 25, 2016 news item on Nanowerk (Note: A link has been removed),

A workshop organized last year [2015] by the PETA International Science Consortium Ltd has resulted in an article published today in the journal Particle and Fibre Toxicology (“Aerosol generation and characterization of multi-walled carbon nanotubes [MWCNTs] exposed to cells cultured at the air-liquid interface”). It describes aerosol generation and exposure tools that can be used to predict toxicity in human lungs following inhalation of nanomaterials.

An April 25, 2016 PETA press release on EurekAlert, which originated the news item, explains further without much more detail,

Nanomaterials are increasingly being used in consumer products such as paints, construction materials, and food packaging, making human exposure to these materials more likely. One of the common ways humans may be exposed to these substances is by inhalation, therefore, regulatory agencies often require the toxicity of these materials on the lungs to be tested. These tests usually involve confining rats to small tubes the size of their bodies and forcing them to breathe potentially toxic substances before they are killed. However, time, cost, scientific and ethical issues have led scientists to develop methods that do not use animals. The tools described in the new article are used to deposit nanomaterials (or other inhalable substances) onto human lung cells grown in a petri dish.

Co-authors of the Particle and Fibre Toxicology article are scientists from the PETA Science Consortium , The Dow Chemical Company, Baylor University, and the U.S. NTP Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM).

“Promoting non-animal methods to assess nanotoxicity has been a focus of the PETA International Science Consortium”, said Dr. Monita Sharma, co-author of the publication and Nanotechnology Specialist at the Consortium, “we organized an international workshop last year on inhalation testing of nanomaterials and this review describes some of the tools that can be used to provide a better understanding of what happens in humans after inhaling these substances.” During the workshop, experts provided recommendations on the design of an in vitro test to assess the toxicity of nanomaterials (especially multi-walled carbon nanotubes) in the lung, including cell types, endpoints, exposure systems, and dosimetry considerations. Additional publications summarizing the outcomes of the workshop are forthcoming.

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

Aerosol generation and characterization of multi-walled carbon nanotubes exposed to cells cultured at the air-liquid interface by William W. Polk, Monita Sharma, Christie M. Sayes, Jon A. Hotchkiss, and Amy J. Clippinger. Particle and Fibre Toxicology201613:20 DOI: 10.1186/s12989-016-0131-y Published: 23 April 2016

This is an open access paper.

Outer space telescopes made of micro- and nanoparticles (smart dust)

Scientists at Rochester Institute of Technology (RIT is located in New York state) are working on a project that would see ‘smart dust’ used as a telescope in outer space. From a Dec. 1, 2014 news item on phys.org,

Telescope lenses someday might come in aerosol cans. Scientists at Rochester Institute of Technology and the NASA [ National Aeronautics and Space Administration] Jet Propulsion Laboratory are exploring a new type of space telescope with an aperture made of swarms of particles released from a canister and controlled by a laser.

These floating lenses would be larger, cheaper and lighter than apertures on conventional space-based imaging systems like NASA’s Hubble and James Webb space telescopes, said Grover Swartzlander, associate professor at RIT’s Chester F. Carlson Center for Imaging Science and Fellow of the Optical Society of America. Swartzlander is a co-investigator on the Jet Propulsion team led by Marco Quadrelli.

A Dec. 1, 2014 RIT news release by Susan Gawlowicz, which originated the news item, describes the NASA project and provides more details about the technology,

NASA’s Innovative Advanced Concepts Program is funding the second phase of the “orbiting rainbows” project that attempts to combine space optics and “smart dust,” or autonomous robotic system technology. The smart dust is made of a photo-polymer, or a light-sensitive plastic, covered with a metallic coating.

“Our motivation is to make a very large aperture telescope in space and that’s typically very expensive and difficult to do,” Swartzlander said. “You don’t have to have one continuous mass telescope in order to do astronomy—it can be distributed over a wide distance. Our proposed concept could be a very cheap, easy way to achieve large coverage, something you couldn’t do with the James Webb-type of approach.”

An adaptive optical imaging sensor comprised of tiny floating mirrors could support large-scale NASA missions and lead to new technology in astrophysical imaging and remote sensing.

Swarms of smart dust forming single or multiple lenses could grow to reach tens of meters to thousands of kilometers in diameter. According to Swartzlander, the unprecedented resolution and detail might be great enough to spot clouds on exoplanets, or planets beyond our solar system.

“This is really next generation,” Swartzlander said. “It’s 20, 30 years out. We’re at the very first step.”

Previous scientists have envisioned orbiting apertures but not the control mechanism. This new concept relies upon Swartzlander’s expertise in the use of light, or photons, to manipulate micro- or nano-particles like smart dust. He developed and patented the techniques known as “optical lift,” in which light from a laser produces radiation pressure that controls the position and orientation of small objects.

In this application, radiation pressure positions the smart dust in a coherent pattern oriented toward an astronomical object. The reflective particles form a lens and channel light to a sensor, or a large array of detectors, on a satellite. Controlling the smart dust to reflect enough light to the sensor to make it work will be a technological hurdle, Swartzlander said.

Two RIT graduate students on Swartzlander’s team are working on different aspects of the project. Alexandra Artusio-Glimpse, a doctoral student in imaging science, is designing experiments in low-gravity environments to explore techniques for controlling swarms of particle and to determine the merits of using a single or multiple beams of light.

Swartzlander expects the telescope will produce speckled and grainy images. Xiaopeng Peng, a doctoral student in imaging science, is developing software algorithms for extracting information from the blurred image the sensor captures. The laser that will shape the smart dust into a lens also will measure the optical distortion caused by the imaging system. Peng will use this information to develop advanced image processing techniques to reverse the distortion and recover detailed images.

“Our goal at this point is to marry advanced computational photography with radiation-pressure control techniques to achieve a rough image,” Swartzlander said. “Then we can establish a roadmap for improving both the algorithms and the control system to achieve ‘out of this world’ images.”

You can find out more about NASA’s Orbiting Rainbows project here.

I just mentioned rainbows and optics with regard to Robert Grosseteste, a 13th century cleric who ‘unwove’ rainbows, in a Dec. 1, 2014 posting (scroll down about 60% of the way).

Nanozen: protecting us from nanoparticles (maybe)

Friday, Oct. 24, 2014 the Vancouver Sun (Canada) featured a local nanotechnology company, Nanozen in an article by ‘digital life’ writer, Gillian Shaw. Unfortunately, the article is misleading. Before noting the issues, it should be said that most reporters don’t have much time to prepare stories and are often asked to write on topics that are new or relatively unknown to them. It is a stressful position to be in especially when one is reliant on the interviewee’s expertise and agenda. As for the interviewee, sometimes scientists get excited and enthused and don’t speak with their usual caution.

The article starts off in an unexceptionable manner,

Vancouver startup Nanozen is a creating real-time, wearable particle sensor for use in mines, mills and other industrial locations where dust and other particles can lead to dangerous explosions and debilitating respiratory diseases.

The company founder and, presumably, lead researcher Winnie Chu is described as a former professor of environmental health at the University of British Columbia who has devoted herself to developing a new means of monitoring particles, in particular nanoparticles. Chu is quoted as saying this,

“The current technology is not sufficient to protect workers or the community when concentrations exceed the acceptable level,” she said.

It seems ominous and is made more so with this,

Chu said more than 90 per cent of the firefighters who responded to the 9/11 disaster developed lung disease, having walked into a site full of small and very damaging particles in the air.

“Those nanoparticles go deep into your lungs and cause inflammation and other problems,” Chu said.

It seems odd to mention this particular disaster. The lung issues for the firefighters, first responders and people living close to the site of World Trade Centers collapse are due to a complex mix of materials in the air. Most of the research I can find focuses on micrsoscale particles such as the work from the University of California at Davis’s Delta Group (Detection and Evaluation of the Long-Range Transport of Aerosols). From the Group’s World Trade Center webpage,

The fuming World Trade Center debris pile was a chemical factory that exhaled pollutants in particularly dangerous forms that could penetrate deep into the lungs of workers at Ground Zero, says a new study by UC Davis air-quality experts.

You can find the group’s presentation (-Presentation download (WTC aersols ACS 2003.ppt; 7,500kb)) to an American Chemical Society meeting in 2003 along more details such as this on their webpage,

The conditions would have been “brutal” for people working at Ground Zero without respirators and slightly less so for those working or living in immediately adjacent buildings, said the study’s lead author, Thomas Cahill, a UC Davis professor emeritus of physics and atmospheric science and research professor in engineering.

“Now that we have a model of how the debris pile worked, it gives us a much better idea of what the people working on and near the pile were actually breathing,” Cahill said. “Our first report was based on particles that we collected one mile away. This report gives a reasonable estimate of what type of pollutants were actually present at Ground Zero.

“The debris pile acted like a chemical factory. It cooked together the components of the buildings and their contents, including enormous numbers of computers, and gave off gases of toxic metals, acids and organics for at least six weeks.”

The materials found by this group were not at the nanoscale. In fact, the focus was then and subsequently on materials such as glass shards, asbestos, and metallic aerosols at the microscale, all of which can cause well documented health problems. No doubt effective monitoring would have been helpful It seems the critical issue in the early stages of the disaster was access to a respirator. Also, effective monitoring at later stages which did not seem to have happened would have been a good idea.

A 2004 (?) New York Magazine article by Jennifer Senior titled ‘Fallout‘ had this to say about the air content,

Here, today, is what we know about the dust and air at ground zero: It contained glass shards, pulverized concrete, and many carcinogens, including hundreds of thousands of pounds of asbestos, tens of thousands of pounds of lead, mercury, cadmium, dioxins, PCBs, and polycyclic aromatic hydrocarbons, or PAHs. It also contained benzene. According to a study done by the U.S. Geological Survey, the dust was so caustic in places that its pH exceeded that of ammonia. Thomas Cahill, a scientist who analyzed the plumes from a rooftop one mile away, says that the levels of acids, insoluble particles, high-temperature organic materials, and metals were in most cases higher in very fine particles (which can slip deep into the lungs) than anyplace ever recorded on earth, including the oil fires of Kuwait.

The article describes at some length the problems for first responders and for those who later moved back into their homes nearby the disaster site under the impression the air was clean.

Getting back to the nanoscale, there were carbon nanotubes (CNTs) present as this 2009 research paper, Case Report: Lung Disease in World Trade Center Responders Exposed to Dust and Smoke: Carbon Nanotubes Found in the Lungs of World Trade Center Patients and Dust Samples, noted in relation to a sample of seven patients,

It may well be the most frequent injury pattern in exposed patients with severe respiratory impairment. b) Interstitial disease was present in four cases (Patients A, B, C, and E), characterized by a generally bronchiolocentric pattern of interstitial inflammation and fibrosis of variable severity. The lungs of these patients contained large amounts of silicates, and three of them showed nanotubes.

CNT of commercial origin, common now, would not have been present in substantial numbers in the WTC complex before the disaster in 2001. However, the high temperatures generated during the WTC disaster as a result of the combustion of fuel in the presence of carbon and metals would have been sufficient to locally generate large numbers of CNT. This scenario could have caused the generation of CNT that we have noted in the dust samples and in the lung biopsy specimens.

Given that CNTs are more common now, it would suggest that a monitor for nanoscale materials such as Chu’s proposed equipment could be an excellent idea. Unfortunately, it’s not clear what Chu is trying to achieve as she appears to make a blunder in the article,

Chu said environmental agencies require testing to distinguish between particles equal to or less than 10 microns and smaller particles 2.5 microns or less.

“When we inhale we inhale both size particles but they go into different parts of the lung,” said Chu, who said research shows the smaller the particle the higher the toxicity. [emphasis mine] The monitor she has developed can detect particles as small as one micron and even less.

The word ‘nanoparticle’ is often used generically to include, CNTs, quantum dots, silver nanoparticles, etc. as Chu seems to be doing throughout the article. The only nanomaterial/nanoparticle that researchers agree unequivocally cause lung problems are long carbon nanotubes which resemble asbestos fibres. This is precisely the opposite of Chu’s statement.

For validation, you can conduct your own search or you can check Swiss toxicologist Harald Krug’s (mentioned in my Nanosafety research: a quality control issue posting of Oct. 30, 2014) statement that most health and safety research of nanomaterials and the resultant conclusions are problematic. But he too is unequivocal with regard long carbon nanotubes (from Krug’s study, Nanosafety Research—Are We on the Right Track?).

Comparison of instillation and inhalation experiments: instillation studies have to be carried out with relatively high local doses and, thus, more often meet overload conditions than inhalation studies. Transient inflammatory effects have been observed frequently in both types of lung exposure, irrespective of the type of ENMs used for the experiment. This finding suggests an unspecific particle effect; moreover, the biological response seems to be comparable to a scenario involving exposure to fine dust. Prominent exceptions are long and rigid carbon nanotube (CNT) bundles, which induce a severe tissue reaction (chronic inflammation) that may ultimately result in tumor formation. Overall, the evaluated studies showed no indication of a “nanospecific” effect in the lung. [from the Summary section; 2nd bulleted point]

You can find the Nanozen website here but there doesn’t appear to be any information on the site yet. These search terms ‘about’, ‘team’, ‘technology’, and ‘product’ yielded no results on website as of Oct. 30, 2014 at 1000 hours PDT.

Germany, aerosols, and engineered nanomaterials

A strategy paper for occupational health and safety as it regards the use of nanoscale aerosols in Germany has been issued jointly by six organizations according to the Oct. 11, 2011 news item on Nanowerk.  I have clipped their logos and names from the strategy paper as I have difficulty identifying these organizations from abbreviations that are German language-based,

The working group summarized their findings (from the strategy paper:  Tiered Approach to an Exposure Measurement and Assessment of Nanoscale Aerosols Released from Engineered Nanomaterials in Workplace Operations)

The main findings of the working group can be summarized as follows :

• Safe work places where ENMs are produced or processed can be achieved, using existing technology, and which conforms with best industrial hygiene practices. Existing substance-specific, binding, health based OELs must be complied with and are not subject of or overridden by the current approach.

• Exposure measurement of nanoscale aerosols released from ENMs in the work-place is possible and exposure assessment methodologies exist. However, methodologies are not yet standardized and more difficult to apply as in routine operations, e.g. gravimetric dust measurements according to DIN EN 481.

• Equipment required for measurement of exposure to nanoscale aerosols released from ENMs is sophisticated and the results produced, e.g., total particle number concentration, have no direct correlation to the chemical identity. Calibration of equipment is still a challenge and validation using round robin testing, which is typically correlated with SMPS results, is difficult as no commonly accepted reference method is available.

• At the moment, for a practitioner, a tiered approach to exposure assessment appears to be the most appropriate strategy. This approach is split into 3 tiers. In the first step (Tier 1) information is gathered according to established industrial hygiene practices. In the next tier (Tier 2) a basic exposure assessment using a limited set of easy-to-use equipment is conducted, where as in the highest tier 6 (Tier 3) the latest state-of-theart measurement technology is employed to assess the potential for workplace exposure to nanoscale aerosols released from ENMs if required.

• Existing legally binding OELs, e.g. synthetic amorphous silica [TRGS 900: EC No. 231-545-4], carbon black [ACGIH], etc., have to be complied with. Where no such substance-specific, binding, health-based OEL values for ENMs exist, the tiered approach is using 3 criteria for the assessment of the data:

1) Interference value exceeded for nanoscale aerosols released from ENMs.

2) Significant increase over aerosol background level in the workplace air.

3) Chemical identity of the nano-objects and their nanoscale aggregates and agglomerates detected in the aerosol.

• The application of the decision logic leads in total to 7 different cases (Case A – G), which may guide the risk management decisions of the practitioner.

• This step-by-step approach may need to be revisited as soon as new scientific findings are available (especially on binding, health-based occupational exposure limit values). The presented exposure assessment strategy of nanoscale aerosols released from ENMs in the workplace may serve as a starting point for further standardization. (p. 3 PDF, p. 6 print version)