In recent years, there have been significant advances made in the science and regulation of PCB’s, the environmental toxins that Rachel Carson made public in her book “Silent Spring.” Less is known of PBDE’s, a structurally similar and increasingly pervasive chemical used in flame retardants. Host Steve Curwood talks with two San Francisco Bay researchers who have found elevated levels of PBDE’s in mothers’ breast milk and fatty tissue.
CURWOOD: Ever since the landmark book “Silent Spring” by Rachel Carson, PCB's and dioxins have taken center stage in the debate over environmental toxins. There is less awareness of a similar class of chemicals called PBDEs, increasingly used to make flame retardants. Researchers recently found elevated levels of PBDE in mother's breast milk and fatty tissue in the San Francisco Bay area. To talk about the findings and possible health effects of PBDE, I am joined by lead author Myrto Petreas, environmental biochemist with California's Department of Toxic Substances Control. Also joining me is Tom McDonald, toxicologist for the California Environmental Protection Agency. Dr. Petreas, let's start with you. What exactly are PBDEs and where are they found?
PETREAS: PBDEs are flame retardants. There are three major industrial formulations of PBDEs and they're called the penta, the octa, and the deca. The penta is used in foam, used in furnishings, car seats. Very often the deca are used mostly with rigid plastics, like the computer monitor, the TV, other devices like that, so that it may prevent any flames or fires.
CURWOOD: Now you studied three groups of women in the San Francisco Bay area. Tell me about these three groups, and why did you choose to study these particular women?
PETREAS: The study you're referring to is combining data from three separate epidemiological studies that are still going on. We analyzed the tissues from these women’s blood or adipose – or fatty – tissue, for a number of chemicals, like the pesticides, PCBs, and PBDEs. And we found very high levels of PBDEs in two of the groups. And the most interesting thing was that the levels we found in these two groups were the highest we had ever seen, at least ten times higher than what was reported from Europe or Japan.
The other interesting thing is that we didn't find anything of these PBDEs in the third group of women. This was archived blood from the '60s, and we couldn't see the PBDEs. So what we could see in the '90s we could not see in the '60s.
In fact, what generated the interest in PBDEs was a few years back in Sweden, results from archived human milk from the '70s all the way to the '90s showed an exponential increase, so PBDEs were rising. And in the same sample of Swedish milk, all the other pesticides and dioxins and PCBs were dropping.
Now I should mention that the levels that generated all this interest in Sweden was less than ten times lower than what we are seeing here in California in the '90s.
CURWOOD: Tom McDonald, what do these PBDE levels suggest in terms of possible health effects, do you think?
MCDONALD: There's three primary concerns that we have with respect to health effects, and those include neuro-developmental changes, meaning learning and memory deficits in children, also thyroid hormone disruption, as well as possibly cancer. The concern basically comes from animal studies. We have, for example, three independent laboratories now, one in Sweden, one in Italy, and one here in the United States, that have all shown that either in rats and mice when you give PBDEs to them, either in utero or early after birth, you get permanent changes in behavior and learning and memory. And these are very similar to what we see with the PCBs, which is also a very similar chemical in both structure and activity.
CURWOOD: What do we know about how these chemicals might have gotten into human fat tissue and blood?
PETREAS: PBDEs are what we call persistent bioaccumulative chemicals. They get released into the environment, and because they are persistent, they don't break down. They get into the food web. So most of our exposure comes through the diet. Once they're in the body, because they don't metabolize so easily, they stay a long time and they store in the fatty tissues.
Now, the interesting thing about PBDEs is that, in addition to the diet, we think that we may be exposed to them through either inhalation or ingestion of dust. PBDEs have been measured in offices and homes and we think they may be coming from the use of consumer products, particularly foam, which may be friable, coming out through the fabric, maybe, of a sofa. And then we get exposed to them as well.
CURWOOD: What regulations exist for this type of flame retardant?
PETREAS: There are no regulations in the United States. Recently the European Union banned the use of penta and octa. The deca is still under investigation, waiting for a risk assessment to be completed.
CURWOOD: Now what are the advantages to using this class of chemicals as flame retardants?
MCDONALD: Indeed, it's very important that we do have products that don't burn quickly. California is one state that has very stringent fire safety flame retardancy standards, and I think a lot of the consumer products that are produced in the U.S. are made so that they meet California standards. For example, the PBDEs are added to plastics and foam, sometimes as much as 10 percent of the weight of the material. And when a plastic or a foam starts to burn, the PBDE actually quenches the fire and slows the burning and saves lives.
CURWOOD: How much does the U.S. consume of this stuff?
MCDONALD: Well, current estimates range on the order of somewhere about 75 million pounds per year, so this is quite a high-use chemical. These are such ubiquitous contaminants that I think we're all exposed to low levels of these.
CURWOOD: Tom McDonald is a toxicologist with the California Environmental Protection Agency. Myrto Petreas is an environmental biochemist with California's Department of Toxic Substances Control. Thank you both for speaking with me today.
PETREAS: Thank you.
MCDONALD: It was a pleasure.
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