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Tree Bark Shows Global Spread of Toxic Chemicals

Tree Bark Shows Global Spread of Toxic Chemicalsi
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March 15, 2013 9:14 PM
The chemicals used to retard fire in consumer products such as furniture and clothing can become toxic pollutants when they wind up in the environment. And they are in the environment - all over the world - in the water, the soil, the plants, and the air. Tracking the spread of these chemicals has been a major challenge, but it just got easier. Erika Celeste reports for VOA on the new technique.

Tree Bark Shows Global Spread of Toxic Chemicals

Erika Celeste
The US Environmental Protection Agency has begun a major new risk assessment of 20 flame-retardant chemicals. These compounds have been widely used for decades in many consumer products, from furniture to sleepwear. But the chemicals are toxic.  And although they are being phased out, they have become a worldwide pollutant and a serious threat to human health.  Measuring their presence in our water, soil, and air has been a major challenge.  But, a new technique promises to make it much easier.

And they are in the environment all over the world; in the water, soil, plants and the air. Tracking the spread of these chemicals has been a major challenge, but it just got easier.

It takes less than 90 seconds for a spark to grow to an inferno. Flame retardants can prevent this.

But Indiana University researcher Amina Salamova points out that when the chemicals evaporate, they become toxic air pollutants.

On the campus of Indiana University, Amina Salamova studies polybrominated diphenyl ethers [PBDEs], and other chemical environmental pollutants. PBDEs are widely used as flame retardants but have been associated with adverse effects on human health.

“They can have an effect on neurological development, on reproductive system, and they can effect your thyroid endocrine system,” said Salamova.

Concerns about those effects have prompted regulatory agencies and some manufacturers to phase out the use of many flame retardant chemicals. But PBDEs can persist for years in the environment, and scientists do not know precisely where or how they spread.

Novel tool

That’s why Salamova and her co-researcher Ronald Hites developed a new technique to measure the presence and concentration of flame retardant chemicals in the air, by sampling the bark of trees.  

“The tree’s ideal because it’s sitting there passively soaking up these compounds out of the atmosphere,” said Hites.

A tree’s bark provides a large surface area that takes in chemicals as both vapor and particles. Also, because a layer of bark remains on the tree for five years or so before being shed, it provides a unique record of the environment over time.

Salamova said the tree-bark approach has many advantages over the current, more complex sampling method, which involves pumping air through expensive equipment, and requires plenty of manpower, and electricity.

“So what I see in future for tree bark is the ability to use this method in developing countries which don’t have a lot of funding for elaborate atmospheric studies. Also we can use this method in remote sites where there is no power,” said Salamova.

Global initiative

With the help of the Global Atmospheric Passive Sampling network, an international monitoring initiative, Salamova and Hites received bark samples from 12 locations around the world, including Norway, the Czech Republic, South Africa, Nepal, Indonesia, the United States and Canada.  

“So this way, you collect about 50 gram of bark, you can collect it from either side of the tree,” said Salamova.

Researchers use a chisel and hammer to tap out a few pieces of bark, wrap them in foil and ship them back to Indiana University for chemical analysis.

Pervasive evidence

Studying those samples in the lab, the researchers found evidence of flame retardants in the atmosphere at all 12 locations. Hites was not surprised to find the highest concentrations at urban sites in Ontario, Canada and around the U.S. Great Lakes.

What was unexpected was the high level of chemicals in some very remote rural regions of Indonesia and Tasmania.

“There’s hardly anybody there. It’s really out of the winds of possible industrial sources. But still these compounds are present there at reasonably high levels, they’re slightly below average, but again measurable levels in the tree bark from Tasmania,” said Hites.

The researchers’ findings, detailed in the journal Environmental Science and Technology, show that these compounds are migrating surprisingly long distances. Salamova says they hope to continue collecting samples to build a global database so scientists and regulatory agencies can understand the pervasiveness of chemical retardants and find ways to remove them from the environment.

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by: Rie K.Maegawa from: Japan
March 31, 2013 1:50 AM
We should rate this experiment highly from the following points. First, this laboratory and field work does not kill any living creatures. Secondly, the samples are really widely collected. As the result, the researchers have found the unexpected high leverl of the chemicals in the very remote rural regions of Indonesia and Tasmania. Building a global database for the data is significant.


by: Chinara from: Azerbaijan
March 19, 2013 8:59 PM
Is it possible to conduct tests on dioxin by this method? As dioxin also is very toxic and persistent pollutant and accumulates in the tissue from all type of environment.


by: cleanair from: Tasmania
March 17, 2013 8:38 AM
Thank you to the researchers who have discovered this process.
I live in Tasmania. There are about half a million people live here.
These results are interesting because our CSIRO tells us we have the cleanest air in the world.

In Response

by: Ian from: USA
March 18, 2013 11:28 AM
You may actually still have the cleanest air in the world.
It is just the whole world's air getting worse


by: Kitagawa Keikoh from: Jiyugaoka, JPN
March 15, 2013 8:00 PM
We are threatening from China's PM2.5 in Japan. They are the worst pollution producer in the world. They don't have enough technology to prevent pollutions and they are wasting energy. That is a new weapon of harasment for neighbor countries.

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