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.
On the campus of Indiana University, Amina Salamova studies polybrominated diphenyl ethers and other chemical environmental pollutants. The ethers 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 these ethers can persist for years in the environment, and scientists do not know precisely where or how they spread.
That’s why Ms. 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.
Ms. 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 Ms. Salamova.
With the help of the Global Atmospheric Passive Sampling network, an international monitoring initiative, Ms. 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 grams of bark, you can collect it from either side of the tree,” said Ms. 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.
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. Ms. 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.