Silver Membrane

Marine biology and Oceanography organizations have long used a variety of filter media to assist with their research. While the ways in which filtration supplies can be used are as diverse as the life forms that live under the waves, here we highlight a couple of these applications that have previously been mentioned in published papers to give you an idea about some ways filters can be purposed in marine research.

In a study on mercury content of the ocean area between Antarctica and Tasmania, researchers from the Ifremer Institute used the 0.2 Micron, 47 mm polycarbonate membrane filters to filter samples of seawater and brine prior to determining their mercury content through atomic fluorescence spectroscopy. The PCTE membranes were used in conjunction with Sartorius filtration devices and a Nalgene vacuum pump to attain filtered water in volumes between 100 and 1000 mL. By applying this filtration setup the researchers were able to find patterns in how mercury travels the ocean.

Another oceanographic use for filtration materials comes from the study of zooplankton that live deep in the Pacific Ocean. 1.2 Micron silver membrane filters were used to pre-filter samples of plankton waste prior to nitrogen content analysis via a high temperature combustion technique.

Also using silver membrane filters (1.2 Micron, 25 mm) was an experiment by the Woods Hole Oceanographic Institution which used them as part of a study to see if the growth of marine phytoplankton in certain areas leads to organic carbon being exported. Here the membranes were used to collect and prepare particles from deep water samples for further analysis.

Remember, these are just a few examples of how filters can be used in the marine sciences. If you’ve been doing your own tests with filter media, let us know in the comments!

In a case of good news/bad news for industrial workers, OSHA (the Occupational Safety and Health Administration) is getting a budget increase for 2012, but the money comes with a delay on a proposal that would further limit workers’ exposure to carcinogenic silica dust.

The backstory: Last February OSHA sent a proposal to the White House Office of Management and Budget that called for a reduction in the silica PEL¹ (Permissible Exposure Limit), which would be the first change to this regulation since the 1960’s². The plan was to get the approval of the OMB and then open up the proposal to public debate after 90 days, but one year later and OSHA is still waiting.

The reason for the snag is most likely because of concerns raised by the industries that would be financially affected by stricter controls. Some opponents of the new OSHA proposal argue that the government needs to do a better job of enforcing the current rules before making any changes to the exposure level. Congress seems to agree with this priority, as the largest line item increase in the new budget is $5 million for additional enforcement OSHA’s sister organization, MSHA (Mine Safety and Health Administration). Representatives for the impacted industries, such as construction and mining, also point out that they subject themselves to voluntary monitoring and medical treatment for certain silica levels and these measures have been effective at eliminating the health risks to workers.

Unfortunately for those who disagree with that assessment, a stricter regulation is unlikely to happen in the immediate future since with the upcoming elections lawmakers aren’t in a hurry to pass a regulation that could paint them as “anti-business.” So at least for now OSHA is going to have to use their bigger budget to make the current regulations work.

For more information on the new OSHA budget we recommend this piece by NPR and this writeup from Patton Boggs LLP.

1)  The PEL for silica is a little tricky to explain – there are several variables and conditions that prevent it from being expressed as a simple number. You can read this blog post from The Safety Director’s Cut for a detailed explanation.

2) While the acceptable levels may change, there aren’t any expected changes to the recommended procedure for evaluating crystalline silica – which involves filtering samples on silver membrane filters and X-Ray Diffraction analysis. You can find the full procedure from the CDC here.

This week the Occupational Safety and Health Administration (OSHA) fined a carbon steel foundry in Wisconsin $95,480 for willfully overexposing their workers to crystalline silica, a known carcinogen. Ironically, this news comes shortly after a group of citizens petitioned the Wisconsin Department of Natural Resources (DNS) to adopt more stringent rules governing emissions of respirable crystalline silica.

Crystalline silica is a particularly dangerous air pollutant because it is a basic component of soil, sand, brick, granite and other common materials. As a byproduct of many everyday industrial processes like mining, construction, and glass manufacturing, it is a ubiquitous presence for some workers. Industrial processes that involve abrasive blasting or the use of sand and quartz are also sources of crystalline silica exposure, which is why many of these workers are concerned over the increasing popularity of fracking in their state. The hydraulic fracturing (AKA “Fracking”) process involves fracturing rock layers with a fluid that includes sand or ceramic material in order to extract the gas underneath. As you can tell from the description, stirring up compressed rock dust and sand particles is a definite health concern, so it’s good to see those at risk aware of it and addressing the matter.

The petitioners are asking the Wisconsin DNS to classify respirable crystalline silica as a hazardous air pollutant under their air toxics rule. Furthermore, the petitioners recommend that the DNS comply with the standard set by the State of California Office of Environmental Health Hazard Assessment which dictates a limit of 3 micrograms per cubic meter and requires consistent monitoring and enforcement.

Determining the concentration of crystalline silica and amorphous silica by the National Institute for Occupational Safety and Health (NIOSH) standards requires capturing particulates from an air sample on a 0.45 micron, 25 mm diameter Silver Membrane Filter and then analyzing the particulate matter for silica using X-Ray diffraction (XRD). See NIOSH methods 7500 and 7501 for the complete procedure.

Read the full petition by Wisconsin citizens here.
Also see this report on silica from the Wisconsin DNS.

Coal miners could be at greater risk to lung ailments caused by air-borne contaminants such as crystalline silica, according to a new NIOSH (National Institute for Occupational Safety and Health) publication. After reviewing information that had been published over the last 15 years the agency determined that miners may face increased exposure to these harmful materials as the more productive seams of coal are mined out, forcing them to dig deeper into thinner mining seams. The result is longer working hours in environments that have denser concentrations of crystalline silica, creating respiratory and pulmonary disease.

NIOSH is responsible for setting guidelines on exposure levels of damaging substances like crystalline silica as well as recommending the sampling procedures for these toxic particles. The NIOSH sample technique for crystalline silica involves redepositing the sample onto a 0.45 micron, 25 mm silver membrane filter for analysis by x-ray diffraction. Testing for air-borne contaminants is one of the most common applications for our silver membranes. NIOSH did not make any changes to the sampling method in their new report. In fact, these new findings strengthen their concerns about the respiratory health effects caused by coal mine dust.

If you fastidiously watch “Through the Wormhole” like I do, chances are you’ll find this application for silver membrane filters fascinating – they’re being used to assist in the collection of antimatter! Now if your main reference for antimatter is a certain Dan Brown novel, you should know that separating and collecting antimatter is a much, much more difficult process than the entertainment industry would have you believe. In fact, “If you take all the antimatter produced in the history of the world and annihilated it all at once, you wouldn't have enough energy to boil a pot of tea,” according to Harvard physicist Gerald Gabrielse. Professor Gabrielse is a leader in antimatter trapping methodology and a co-author of the paper Pumped Helium System for Cooling Positron and Electron Traps to 1.2 K, which details how our filters are used to trap antimatter.

Antimatter is composed of the exact opposite particles (particles of the same mass but opposite electrical charges) as its traditional counterpart. So whereas a hydrogen atom is made of one electron and one proton, an antihydrogen atom (called H-Bar) is comprised of a positron and an antiproton. When antimatter comes into contact with matter, even air, both particles annihilate and release energy in the form of photons (light particles) and/or radiation. Because of the extreme instability of antimatter, one of the major challenges with studying it is gathering enough of the material in a lab. To store any amount of antimatter requires an extremely powerful vacuum to prevent it from coming into any contact with matter. To this end, scientists are experimenting with all manner of “traps” in order to separate and analyze the antimatter.

It is one of these traps that pure silver membranes have found a role in the antimatter collection process. The paper referenced above explains how in order to collect antihydrogen the scientists must cool the trap apparatus to temperatures close to absolute zero. To cool the apparatus to such an extreme degree the scientists here use liquid helium (which is about -269°C), this is also where the silver filters come into play. In order to remove any impurities that could cause clogging in the apparatus, the liquid helium is twice filtered through silver filters, first through a 5 micron filter and then a 3 micron filter before continuing through the pumping system.

A popular misconception about antimatter is that it has potential as an alternative energy source. On his website Professor Gabrielse points out that “No antimatter energy source will ever be possible since it takes much more energy to make antimatter than can ever be recovered from antimatter annihilation…Our motivation for trapping antimatter is to study is basic properties and to compare them with the properties of ordinary hydrogen atoms.” So while this research isn’t going to solve our energy problems, it could help physicists answer some of the biggest mysteries regarding the makeup of the universe.

That last part would sound better coming from Morgan Freeman…

Check out this interesting article from the NIST Tech Beat explaining how nature may be manufacturing silver nanoparticles all by itself. The article also discusses some ideas as to why it is that silver is such a good antibacterial agent.

Read the NIST article here.

A new study by NIOSH found a more effective method for testing occupational exposure to airborne wood dust, which is known to cause cancer. This new practice incorporates silver membrane filters along with a mid-infrared diffuse reflection method for direct on-filter determination of wood dust mass instead of gravimetric analysis and glass fiber filters, creating a more specific test.

To learn more, you can view the article abstract here.

Today the Environmental Protection Agency awarded $32 million to 4 universities around the country to study the health impacts of air pollution. These centers will answering questions like, "does air pollution effect a child's learning ability?" "Are obese people more susceptible to health effects of air pollution?" "How does your commute effect your health?"

We work with a number of environmental labs to provide filtration materials, and one of the most common requests we get from them is for our 0.45 micron, 25mm silver membranes to comply with NIOSH methods for testing airborne contaminants such as silica and bromine.

Here is a breakdown of what the four new centers are focusing on:

• University of Washington - Effects of roadway pollution on on cardiovascular health.
• Michigan State University - The relationships between obesity and air pollution.
• Emory University / Georgia Institute of Technology - Characterize health risks of air pollution mixtures, research how social factors (living location, commute, etc.) impact health.
• Harvard University - Investigate health effects of short-term and long-term exposure to pollutants on specific health functions, including cognitive function, birth weight, and mortality.

See also:
"EPA Awards $32 Million to Understand Health Impacts of Air Pollution"

EPA Clean Air Research Centers Home

We've previously discussed how the combination of silver and carbon nanotubes can be used to create more efficient water purification filters, now you can see a little bit about how this filter is made thanks to Technology Review and Stanford University. You can read more about the process here.