Flame Retardants and Biosolids -- Redux
I remember when Robert Hale published his first big article about flame retardants in biosolids (article #3 in the library). I was at a meeting and heard his presentation. He talked all about how flame retardants in biosolids would be the end of us all. I was sitting next to Nick Basta (Ohio State) for the talk. Nick picked up on the fact that the concentration of the flame retardants in biosolids (reported at 1- 2 ppm in article #1) was significantly lower than the concentrations in the seat cushions that we were sitting on during the talk (100 000 ppm). He complemented Dr. Hale on his talk and commented that, with the hazards of these compounds, was it even safe to sit down? Prompted by a new article by Dr. Hale, this month’s library focuses on flame retardants or PBDEs in biosolids and in the environment. These compounds, used to prevent and slow fires in a wide range of consumer goods including electronics and clothing, have been ubiquitous in the environment for decades. PBDE is short for polybrominated diphenyl ethers. That translates into ether groups with two phenyls attached that have any number of bromines attached to them. There are a wide number of formulations of these compounds, based on how many bromines are attached. Like another organic that showed up in biosolids (dioxins) the different formulations have different properties including availability and degradation rate. Also like dioxins, these compounds tend to be long lived in soils and to bind tightly to soil organic matter. Finally like many broadly used chemicals, PBDEs show up in biosolids but also show up in a wide range of environmental samples. So let’s go through the articles. The third article, which in a way should be the first, is the first Hale paper on this topic. He has effectively become the ‘go to guy’ on this. This paper reported on concentrations of PBDEs in biosolids from samples collected across the US as well as from fish collected from Virginia. The authors note that the higher concentrations in US media in comparison to European samples is related to the much higher use of these compounds in the US in comparison to Europe. They note that these compounds are found in air samples as well. THERE IS NO DIRECT LINK HERE BETWEEN THE PBDEs IN THE FISH AND IN THE BIOSOLIDS. OK- so they are in biosolids. What happens following land application? Here we can look at the 2nd article. Here authors look at concentration in soils and biosolids amended soils following a single or multiple biosolids applications. Reported units are ug kg or ppb. The authors note that biosolids applications increase soil PBDE and that these compounds persist over time. What is important to note with this paper is the presence of these compounds in the control samples and the high error values. A previous paper out of the Chicago biosolids group (May 10) also noted persistence of PBDEs in soils with minimal movement out of surface soils and presence of these compounds in control soils. Next question is whether the presence in biosolids is a concern. Here we can look at the first paper in the library, a new publication by Hale who has teamed up with Hundal (prior speaker at Biofest) to look at presence, persistence and plant uptake of these compounds. This paper gives an excellent view of national trends in PBDE use, noting that if it is used, it ends up in the biosolids (and household dust for that matter). The authors also found no plant uptake into the multiple parts of the corn plants tested. The article includes a review of studies where plant uptake was observed for plants grown in soils contaminated by PBDE via recycling of electronic wastes. Yes, electronic waste recycling is a significant source of PBDEs in the environment. No uptake from biosolids amended soils was attributed to the ability of the biosolids to tightly bind these compounds. The 4th article in the library looks at another pathway; uptake by worms from biosolids amended soils. Here one interesting thing to note is the high PBDE concentrations in one of the biosolids. There was a textile plant in that town and, back in the day, PBDEs were added to textiles used to make kid’s PJs. The authors detect uptake into worms, in both the control and the biosolids amended soils. Uptake appears to be proportional to soil concentration without a significant concentration factor. The final article is about PBDE concentrations in air and soil samples collected along an urban rural transect in England. I included this article because it is important to realize that these compounds are in the biosolids because they are in everything else. There are multiple references out there for PBDE concentrations in a wide range of environmental samples, from human breast milk to any number of wild animals. Figure 3 in this article shows concentrations in soils in picograms per gram or parts per trillion. In the center of the city, soil concentrations were about 0.1 ppm. I am pretty sure that this is not a function of urban biosolids use, rather just an indication of how these compounds are everywhere.