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General interest items edited by Janice Flahiff

Long-lasting chemicals flooding wastewater treatment plants threaten the environment and human health

Long-lasting chemicals flooding wastewater treatment plants threaten the environment and human health

Rolf Halden is a researcher at the Biodesign Institute at Arizona State University.

 

From a December 21, 2010 Eureka news release

Every hour, an enormous quantity and variety of manmade chemicals, having reached the end of their useful lifespan, flood into wastewater treatment plants. These large-scale processing facilities, however, are designed only to remove nutrients, turbidity and oxygen-depleting human waste, and not the multitude of chemicals put to residential, institutional, commercial and industrial use. So what happens to these chemicals, some of which may be toxic to humans and the environment? Do they get destroyed during wastewater treatment or do they wind up in the environment with unknown consequences?

New research by Rolf Halden and colleagues at the Biodesign Institute at Arizona State University seeks to address such questions. The group’s results, reported recently in the Journal of Environmental Monitoring,*** suggest that a number of high production volume (HPV) chemicals—that is, those used in the U.S. at rates exceeding 1 million pounds per year, are likely to become sequestered in post-treatment sludge and from there, enter the environment when these so-called biosolids are deposited on land.

As Halden notes, over 4000 chemicals in common usage in the U.S. qualify as HPV chemicals, the vast majority of which have never been evaluated in terms of exotoxicity (their potential to adversely affect ecosystems), or for the risks they may pose to humans. “With each of these compounds, we are engaged in an experiment conducted on a nationwide scale,” says Halden; “Odds are, some of these chemicals will turn out to be bad players and will pose problems for ecosystems, public health or both.”

Unfortunately, it is neither technically nor economically feasible to perform the kind of detailed analyses necessary to declare this vast swirl of chemicals safe for humans or environmentally benign following wastewater treatment. Instead, Halden’s efforts are aimed at narrowing the field of potentially troublesome chemicals, by defining traits likely to cause some chemicals to persist in the environment. To do this, the group applied a new empirical model for estimating the fraction of mass loading of chemicals in raw sewage expected to endure in digested sludge.

Chemicals which become sequestered in digested sewage sludge are a potential cause for concern in part because the treated sludge is often subsequently applied to land, including land designated for agricultural use. Halden’s group screened some 207 HPV chemicals, using a model that predicted that two thirds of these compounds are likely to accumulate in digested sludge to greater than fifty percent of their initial mass loading in raw sewage. Eleven of these chemicals were flagged as compounds of special concern and deemed potential hazards to human and environmental health.

Three principal criteria dictated the selection of these problem chemicals: (a) their propensity to accumulate and persist in sludge in large amounts (b) structural characteristics suggestive of environmental persistence on land following biosolids recycling, and (c) unfavorable ecotoxicity threshold values, whether these have been experimentally determined or were forecasted with computer models.

As Halden explains, certain classes of chemicals possess physical characteristics that make them likelier to resist breakdown during wastewater treatment. Of particular concern are hydrophobic organic chemicals. As their name implies, such chemicals are ‘afraid’ of water and preferentially attach themselves to particulate matter, thereby becoming part of the primary and secondary sludge. This characteristic trait limits the availability of hydrophobic chemicals to aerobic and anaerobic microorganisms during sewage treatment and sludge digestion.

Rather than being broken down, such chemicals can become enriched in municipal biosolids by several orders of magnitude. Through this process, substances in heavy usage, like HPV chemicals, can accumulate as pollutants in municipal sludge to parts per million (ppm) concentrations. “It’s like vacuum cleaning your home,” says Halden. “When the carpet is clean, the vacuum bag holds a concentrated burden of dirt. By anology, the generation of biosolids enriched in non-biodegradable pollutants are the price you pay when purifying domestic sewage for water reuse.”

In order to better gauge which chemicals may go on to present human health and environmental risks following sequestration in sludge, the group conducted a computer or in silico analysis. The method provides a streamlined and economically attractive means of isolating those chemicals deserving more in-depth field analysis. The group applied a new empirical model able to predict the fraction of total mass of a hydrophobic chemical likely to persist in biosolids after wastewater treatment.

Another advantage of the new model, applied by Halden and Assistant Professor Randhir Deo from the University of Guam, is simplicity. The model only requires two input values in order to estimate a chemical’s environmental persistence. The chemicals to be screened were taken from the High Production Volume Information System database maintained by the EPA to monitor the environmental fate of chemicals produced in amounts exceeding 1 million pounds per year.

The empirical model was developed and tweaked to produce the best agreement between the mathematical framework based on a given chemical’s physical properties and actual measurements derived from large sewage treatment plants. The physical characteristic found to play the largest role in a chemical’s persistence in sludge was its sorption potential—the tendency of molecules of the chemical to adhere to the surface of other molecules. In the case of the HPV chemicals under consideration, high sorption values among hydrophobic chemicals caused them to stick to other particles and be sequestered from the degradative processes used to treat wastewater.

The bulk of the chemicals included in the HPV study were used for industrial purposes and included antidegradants, antioxidants, metal chelators, intermediates, by-products, catalysts, flame retardants, phenylating agents, plasticizers, heat storage and transfer agents, lubricants, solvents, anticorrosive agents, and others. The study also identified five mass-produced chemicals used as flavors and fragrances that were predicted to persist in sludge in fifty percent or greater amounts of their initial mass loading in raw sewage.

Once chemicals likely to persist in sludge were identified, estimates of their toxicity were examined. Those with high persistence levels and high environmental toxicity made the enemies list of chemicals posing the greatest potential hazard. Prominent among the toxic chemicals were the so-called organohalogen compounds, seven of which were found to accumulate in substantial quantity in treated sludge and displayed half-lives in soil estimated to range from 120 to 360 days.

Perhaps of greatest concern are halogenated chemicals known as organobromines—popular ingredients in a range of flame retardant products, which have subsequently been identified in bird tissues, in egg pools of herring gulls, and in dust samples. Halden insists that better monitoring of just such chemicals is essential for understanding their trajectory and mitigating risks to human health and the environment.

“Our work is directed at identifying problematic compounds before they cause harm to the environment and people. Environmental chemists often can foretell adverse outcomes. What’s lacking are regulations to translate that knowledge into pollution prevention,” says Halden. “Cleaning up after the fact, is costly and hard to do.”

Some related informational links

  • Environmental Health and Toxicology (specialized information services from the US National Institutes of Health and US National Library of Medicine)
    • HazMap -an occupational toxicology database designed to link jobs to hazardous job tasks which are linked to occupational diseases and their symptoms. It is a relational database of chemicals, jobs and diseases.
    • ToxNet – Databases on toxicology, hazardous chemicals, environmental health, and toxic releases
    • Household Products Databases – This database links over 8,000 consumer brands to health effects from Material Safety Data Sheets (MSDS) provided by the manufacturers and allows scientists and consumers to research products based on chemical ingredients
    • and many more databases..
  • Toxicology Web links from NIH & NLM (extensive list of govt, non-govt, and international Web sites)
  • Toxicology Resources especially for the public (from NIH and NLM), including ToxTown and ToxMap

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January 3, 2011 Posted by | Biomedical Research Resources, Consumer Health, Consumer Safety, Educational Resources (High School/Early College(, Finding Aids/Directories, Librarian Resources, Medical and Health Research News, Professional Health Care Resources, Public Health | , , , | Leave a comment

Psychologists find skill in recognizing faces peaks after age 30

Psychologists find skill in recognizing faces peaks after age 30
Finding rebuts pervasive belief that all mental faculties top out in early adulthood

From the December 23, 2010 Eureka news alert

CAMBRIDGE, Mass., Dec. 21, 2010 — Scientists have made the surprising discovery that our ability to recognize and remember faces peaks at age 30 to 34, about a decade later than most of our other mental abilities.

Researchers Laura T. Germine and Ken Nakayama of Harvard University and Bradley Duchaine of Dartmouth College will present their work in a forthcoming issue of the journal Cognition.***

While prior evidence had suggested that face recognition might be slow to mature, Germine says few scientists had suspected that it might continue building for so many years into adulthood. She says the late-blooming nature of face recognition may simply be a case of practice making perfect.

“We all look at faces, and practice face-watching, all the time,” says Germine, a Ph.D. student in psychology at Harvard. “It may be that the parts of the brain we use to recognize faces require this extended period of tuning in early adulthood to help us learn and remember a wide variety of different faces.”

Germine, Duchaine, and Nakayama used the web-based Cambridge Face Memory Test — available at http://www.testmybrain.org — to test recognition of computer-generated faces among some 44,000 volunteers ages 10 to 70. They found that skill at other mental tasks, such as remembering names, maxes out at age 23 to 24, consistent with previous research.

But on a face-recognition task, skill rose sharply from age 10 to 20, then continued increasing more slowly throughout the 20s, reaching a peak of 83 percent correct responses in the cohort ages 30 to 34.

A follow-up experiment involving computer-generated children’s faces found a similar result, with the best face recognition seen among individuals in their early 30s. After this, skill in recognizing faces declined slowly, with the ability of 65-year-olds roughly matching that of 16-year-olds.

“Research on cognition has tended to focus on development, to age 20, and aging, after age 55,” Germine says. “Our work shows that the 35 years in between, previously thought to be fairly static, may in fact be more dynamic than many scientists had expected.”

 

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January 3, 2011 Posted by | Medical and Health Research News | , , , | Leave a comment

Texas A&M research shows bacteria provide example of one of nature’s first immune systems

From the December 23, 2010 Eureka news release

COLLEGE STATION, Texas, Dec. 23, 2010—Studying how bacteria incorporate foreign DNA from invading viruses into their own regulatory processes, Thomas Wood, professor in the Artie McFerrin Department of Chemical Engineering at Texas A&M University, is uncovering the secrets of one of nature’s most primitive immune systems.

His findings, which appear in “Nature Communications,” a multidisciplinary publication dedicated to research in all areas of the biological, physical and chemical sciences, shed light on how bacteria have throughout the course of millions of years developed resistance to antibiotics by co-opting the DNA of their natural enemies—viruses.

The battle between bacteria and bacteria-eating viruses, Wood explains, has been going on for millions of years, with viruses attempting to replicate themselves by – in one approach – invading bacteria cells and integrating themselves into the chromosomes of the bacteria. When this happens a bacterium makes a copy of its chromosome, which includes the virus particle. The virus then can choose at a later time to replicate itself, killing the bacterium—similar to a ticking time bomb, Wood says.

However, things can go radically wrong for the virus because of random but abundant mutations that occur within the chromosome of the bacterium. Having already integrated itself into the bacterium’s chromosome, the virus is subject to mutation as well, and some of these mutations, Wood explains, render the virus unable to replicate and kill the bacterium.

With this new diverse blend of genetic material, Wood says, a bacterium not only overcomes the virus’ lethal intentions but also flourishes at a greater rate than similar bacteria that have not incorporated viral DNA.

“Over millions of years, this virus becomes a normal part of the bacterium,” Wood says. “It brings in new tricks, new genes, new proteins, new enzymes, new things that it can do. The bacterium learns how to do things from this.

“What we have found is that with this new viral DNA that has been trapped over millions of years in the chromosome, the cell has created a new immune system,” Wood notes. “It has developed new proteins that have enabled it to resists antibiotics and other harmful things that attempt to oxidize cells, such as hydrogen peroxide. These cells that have the new viral set of tricks don’t die or don’t die as rapidly.”

Understanding the significance of viral DNA to bacteria required Wood’s research team to delete all of the viral DNA on the chromosome of a bacterium, in this case bacteria from a strain of E. coli. Wood’s team, led by postdoctoral researcher Xiaoxue Wang, used what in a sense could be described as “enzymatic scissors” to “cut out” the nine viral patches, which amounted to precisely removing 166,000 nucleotides. Once the viral patches were successfully removed, the team examined how the bacterium cell changed. What they found was a dramatically increased sensitivity to antibiotics by the bacterium.

While Wood studied this effect in E. coli bacteria, he says similar processes have taken place on a massive, widespread scale, noting that viral DNA can be found in nearly all bacteria, with some strains possessing as much as 20 percent viral DNA within their chromosome.

“To put this into perspective, for some bacteria, one-fifth of their chromosome came from their enemy, and until our study, people had largely neglected to study that 20 percent of the chromosome,” Wood says. “This viral DNA had been believed to be silent and unimportant, not having much impact on the cell.

“Our study is the first to show that we need to look at all bacteria and look at their old viral particles to see how they are affecting the bacteria’s current ability to withstand things like antibiotics. If we can figure out how the cells are more resistant to antibiotics because of this additional DNA, we can perhaps make new, effective antibiotics.”

 

January 3, 2011 Posted by | Medical and Health Research News | , , , , , , | Leave a comment

January is National Radon Action Month

radiation warning sign

From the MedlinePlus Radon page

You can’t see radon. And you can’t smell it or taste it. But it may be a problem in your home. Radon comes from the natural breakdown of uranium in soil, rock and water. Radon is the second leading cause of lung cancer in the United States.

There are low levels of radon outdoors. Indoors, there can be high levels. Radon can enter homes and buildings through cracks in floors, walls or foundations. Radon can also be in your water, especially well water. Testing is the only way to know if your home has elevated radon levels. It is inexpensive and easy. You can buy a test kit at most hardware stores or hire someone to do a test. Radon reduction systems can bring the amount of radon down to a safe level. The cost depends on the size and design of your home.

 

Visit the the MedlinePlus topic page on radon to learn more. You will find links to information with overviews, prevention/screening tips, and directories on how to contact experts.
The primary NIH organization for research on Radon is the National Institute of Environmental Health Sciences

Medline Plus also has these related Web pages

 

Also, check out the Environmental Protection Agency website to learn about the national effort to take action against radon.


January 3, 2011 Posted by | Consumer Health | | Leave a comment

   

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