Tag Archives: cadmium

‘Hunting’ pharmaceuticals and removing them from water

Pharmaceuticals are not the first pollutants people think of when discussing water pollution but, for those who don’t know, it’s a big issue and scientists at the University of Surrey (UK) have developed a technology they believe will help to relieve the contamination. From an April 10, 2017 University of Surrey press release (also on EurekAlert),

The research involves the detection and removal of pharmaceuticals in or from water, as contamination from pharmaceuticals can enter the aquatic environment as a result of their use for the treatment of humans and animals. This contamination can be excreted unchanged, as metabolites, as unused discharge or by drug manufacturers.

The research has found that a new type of ‘supermolecule’, calix[4], actively seeks certain pharmaceuticals and removes them from water.

Contamination of water is a serious concern for environmental scientists around the world, as substances include hormones from the contraceptive pill, and pesticides and herbicides from allotments. Contamination can also include toxic metals such as mercury, arsenic, or cadmium, which was previously used in paint, or substances that endanger vital species such as bees.

Professor Danil de Namor, University of Surrey Emeritus Professor and leader of the research, said: “Preliminary extraction data are encouraging as far as the use of this receptor for the selective removal of these drugs from water and the possibility of constructing a calix[4]-based sensing devices.

“From here, we can design receptors so that they can bind selectively with pollutants in the water so the pollutants can be effectively removed. This research will allow us to know exactly what is in the water, and from here it will be tested in industrial water supplies, so there will be cleaner water for everyone.

“The research also creates the possibility of using these materials for on-site monitoring of water, without having to transport samples to the laboratory.”

Dr Brendan Howlin, University of Surrey co-investigator, said: “This study allows us to visualise the specific receptor-drug interactions leading to the selective behaviour of the receptor. As well as the health benefits of this research, molecular simulation is a powerful technique that is applicable to a wide range of materials.

“We were very proud that the work was carried out with PhD students and a final year project student, and research activities are already taking place with the Department of Chemical and Processing Engineering (CPI) and the Advanced Technology Institute (ATI).

“We are also very pleased to see that as soon as the paper was published online by the European Journal of Pharmaceutical Sciences, we received invitations to give keynote lectures at two international conferences on pharmaceuticals in Europe later this year.”

That last paragraph is intriguing and it marks the first time I’ve seen that claim in a press release announcing the publication of a piece of research.

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

A calix[4]arene derivative and its selective interaction with drugs (clofibric acid, diclofenac and aspirin) by Angela F Danil de Namor, Maan Al Nuaim, Jose A Villanueva Salas, Sophie Bryant, Brendan Howlin. European Journal of Pharmaceutical Sciences Volume 100, 30 March 2017, Pages 1–8 https://doi.org/10.1016/j.ejps.2016.12.027

This paper is behind a paywall.

Quantum dots, televisions, and a counter-intuitive approach to environmental issues

There’s a very interesting Jan. 8, 2015 essay by Dr. Andrew Maynard, being hosted on Nanowerk, about the effects that quantum dot televisions could have on the environment (Note: A link has been removed),

Earlier this week, The Conversation reported that, “The future is bright, the future is … quantum dot televisions”. And judging by the buzz coming from this week’s annual Consumer Electronics Show (CES) that’s right – the technology is providing manufacturers with a cheap and efficient way of producing the next generation of brilliant, high-definition TV screens.

But the quantum dots in these displays also use materials and technologies – including engineered nanoparticles and the heavy metal cadmium – that have been a magnet for health and environmental concerns. Will the dazzling pictures this technology allow blind us to new health and environmental challenges, or do their benefits outweigh the potential risks?

If I understand things rightly, cadmium is toxic at both the macroscale and the nanoscale and Andrew goes on to describe quantum dots (cadmium at the nanoscale) and the problem they could present in his Jan. 7, 2015 essay on The Conversation,also hosted by Nanowerk, (Note: Link have been removed),

Quantum dots are a product of the emerging field of nanotechnology. They are made of nanometer-sized particles of a semiconducting material – often cadmium selenide. About 2,000 to 20,000 times smaller than the width of a single human hair, they’re designed to absorb light of one color and emit it as another color – to fluoresce. This property makes them particularly well-suited for use in products like tablets and TVs that need bright, white, uniform backlights.

… What is unique about quantum dots is that the color of the emitted light can be modified by simply changing the size of the quantum dot particles. And because this color-shifting is a physical phenomenon, quantum dots far outperform their chemical counterparts in brightness, color and durability.

Unfortunately, the heavy metal cadmium used in the production of many quantum dots is a health and environmental hazard.

On top of this, the potential health and environmental impacts of engineered nanoparticles like quantum dots have been raising concerns with toxicologists and regulators for over a decade now. Research has shown that the size, shape and surface properties of some particles influence the harm they are capable of causing in humans and the environment; smaller particles are often more toxic than their larger counterparts. That said, this is an area where scientific understanding is still developing.

Together, these factors would suggest caution is warranted in adopting quantum dot technologies. Yet taken in isolation they are misleading.

The essay describes the risk factors for various sectors (Note: A link has been removed),

The quantum dots currently being used in TVs are firmly embedded in the screens – usually enclosed behind multiple layers of glass and plastic. As a result, the chances of users being exposed to them during normal operation are pretty much nil.

The situation is potentially different during manufacturing, when there is a chance that someone could be inadvertently exposed to these nanoscopic particles. Scenarios like this have led to agencies like the US National Institute for Occupational Safety and Health taking a close look at safety when working with nanoparticles. While the potential risks are not negligible, good working practices are effective at reducing or eliminating potentially harmful exposures.

End-of-life disposal raises additional concerns. While the nanoparticles are likely to remain firmly embedded within a trashed TV’s screen, the toxic materials they contain, including cadmium, could well be released into the environment. Cadmium is certainly a health and environmental issue with poorly regulated e-waste disposal and recycling. However, when appropriate procedures are used, exposures should be negligible.

It seems quantum dot televisions impose a smaller burden than their cousins on the environment,

Although it seems counter-intuitive, analysis by the company that was made available to the EPA [US Environmental Protection Agency] showed QD Vision’s products lead to a net decrease in environmental cadmium releases compared to conventional TVs. Cadmium is one of the pollutants emitted from coal-fired electrical power plants. Because TVs using the company’s quantum dots use substantially less power than their non-quantum counterparts, the combined cadmium in QD Vision TVs and the power plant emissions associated with their use is actually lower than that associated with conventional flat screen TVs. In other words, using cadmium in quantum dots for production of more energy-efficient displays can actually results in a net reduction in cadmium emissions.

Not the conclusion one might have drawn at the outset, eh? You can read the essay in its entirety on either Nanowerk (Jan. 8, 2015 essay) or The Conversation (Jan. 7, 2015 essay). (Same essay just different publication dates.) Andrew has also posted his essay on the University of Michigan Risk Science Center website, Are quantum dot TVs – and their toxic ingredients – actually better for the environment? Note: Andrew Maynard is the center’s director.

Test your tuna for mercury and other heavy metals with nano-velcro

Scientists Francesco Stellacci at the École Polytechnique Fédérale de Lausanne (EPFL) and Bartosz Grzybowski at Northwestern University have devised an easy and economical way to test for mercury and other heavy metals in fish. From the Sept. 9, 2012 news release on EurekAlert,

Mercury, when dumped in lakes and rivers, accumulates in fish, and often ends up on our plates. A Swiss-American team of researchers led by Francesco Stellacci at the Ecole Polytechnique Fédérale de Lausanne (EPFL) and Bartosz Grzybowski at Northwestern University has devised a simple, inexpensive system based on nanoparticles, a kind of nano-velcro, to detect and trap this toxic pollutant as well as others. The particles are covered with tiny hairs that can grab onto toxic heavy metals such as mercury and cadmium. This technology makes it possible to easily and inexpensively test for these substances in water and, more importantly, in the fish that we eat. Their new method can measure methyl mercury, the most common form of mercury pollution, at unprecedentedly small attomolar concentrations.

Here’s a description of how the technique works, from the Sept. 12, 2012 news release on the EPFL website,

The technology developed by the Swiss-American team is simple to use. A strip of glass covered with a film of “hairy”nanoparticles is dipped into the water. When an ion – a positively charged particle, such as a methyl mercury or cadmium ion – gets in between two hairs, the hairs close up, trapping the pollutant.

A voltage-measuring device reveals the result; the more ions there are trapped in the nano-velcro, the more electricity it will conduct. So to calculate the number of trapped particles, all one needs to do is measure the voltage across the nanostructure.

By varying the length of the nano-hairs, the scientists can target a particular kind of pollutant. “The procedure is empirical,” explains Stellacci. Methyl mercury, fortunately, has properties that make it extremely easy to trap without accidentally trapping other substances at the same time; thus the results are very reliable.

The interesting aspect of this approach is that the ‘reading’ glass strip could costs less than 10 dollars, while the measurement device will cost only a few hundreds of dollars. The analysis can be done in the field, so the results are immediately available. “With a conventional method, you have to send samples to the laboratory, and the analysis equipment costs several million dollars,” notes Stellacci.

They have tested the system in the field,

The researchers tested the system in Lake Michigan, near Chicago. Despite the high level of industry in the region, mercury levels were extremely low. “The goal was to compare our measurements to FDA [US Food and Drug Administration] measurements done using conventional methods,” explains Stellacci. “Our results fell within an acceptable range.”

A mosquito fish from the Everglades in Florida was also tested. This species is not very high on the food chain and thus does not accumulate high levels of mercury in its tissues. “We measured tissue that had been dissolved in acid. The goal was to see if we could detect even minuscule quantities.” says Bartosz Grzybowski, Burgess Professor of Chemistry and Director of Non-Equilibrium Energy Research Center at Northwestern University. The United States Geological Survey reported near-identical results after analyzing the same sample.

“I think it is quite incredible,” Grzybowski adds, “how the complex principles of quantum tunneling underlying our device translate into such an accurate and practically useful device. It is also notable that our system – through some relatively simple chemical modifications – can be readily adapted to detect other toxic species” Researchers have already demonstrated the detection of cadmium with a very high femtomolar sensitivity.

“With this technology, it will be possible to conduct tests on a much larger scale in the field, or even in fish before they are put on the market,” says lead author Eun Seon Cho. This is a necessary public health measure, given the toxic nature of methyl mercury and the extremely complex manner in which it spreads in the environment and accumulates in living tissues.

Northwestern University provided an illustration of the nano-velcro trapping an ion of heavy metal,

Nano-velcro (Courtesy Northwestern University & EPFL; downloaded from http://actu.epfl.ch/news/nano-velcro-clasps-heavy-metal-molecules-in-its-gr/)