High Levels of PBDEs Found
PBDEs - Fire Retardants in Dust: High Levels of PBDEs Found
In September 2003, EWG reported record levels of PBDE contamination in the bodies of 20 American mothers. Later that month we initiated a dust study to determine the extent of PBDE contamination in the indoor environment. We asked ten women from the breast milk study to collect samples of dust from their homes. These participants were selected to be a representative sample of the original group with respect to geographical location, PBDE body burden, age and occupation. Women who had moved since submitting their breast milk samples were excluded from the follow-up study. No one reported occupational exposure to foam or plastics, except the use of computers in an office setting.
The ten study participants vacuumed their house as they normally would and sent EWG either the dust bag from their vacuum cleaners or, if they owned vacuum cleaners without bags, emptied the cartridge of their machine into a clean zip-lock bag. The women also filled out a questionnaire on the model and make of their vacuums, how many times they had used their machine since last changing the bag or emptying the canister, and the number of rooms in their house with carpet. Samples were sent to a certified laboratory for analysis.
The results were striking. Each of the ten dust samples contained high levels of PBDEs, with concentrations exceeding 3,000 ppb for half of the study homes and averaging 4,629 ppb. Overall, PBDE levels ranged from 614 to 16,366 parts per billion. We chose to treat one participant's sample separately because she had used her vacuum to clean up polyurethane foam residues when she removed carpet padding, two mattress pads, and an uncovered foam cushion from her home. Her sample contained 41,203 ppb of PBDEs — a level twice as high as reported in any previous study.
Overall, the PBDE levels we found in house dust, though very high, are actually in line with what has been reported in other studies. A study of 100 homes in the UK, for example, measured average levels of 10,543 ppb in dust, with a maximum of 20,505 ppb. The only other U.S. study to look at house dust, in Cape Cod, Mass., found an average PBDE concentration of 3,669 ppb and a maximum of 11,426 ppb [46, 47]
There are 209 chemically distinct variations, or congeners, of PBDEs; the commercial compounds sold as Penta, Octa and Deca are mixtures of several different congeners. Though we tested for thirteen different PBDE congeners, just three of these — PBDE-47, -99 and -209 — comprised 90 percent of the makeup by weight of our dust samples. The two major ingredients in Penta, PBDE-47 and -99, each accounted for 24 percent on average. But PBDE-209, the major ingredient in Deca, was the dominant congener found, making up 42 percent of the samples. Levels of Deca averaged 2,394 ppb, ranging from less than 400 ppb to 7,510 ppb.
High levels of PBDE were found in dust from 10 American homes
One factor may partially explain the wide variation we observed in dust concentrations. Both of the two participants with the highest concentrations of Penta in household dust reported atypical uses of polyurethane foam in their homes. One participant had reupholstered her couch cushions several years before the sample was collected; the other had used her vacuum to clean up the following polyurethane foam products: carpet padding from one room, two mattress pads and a uncovered foam cushion.
Evidence of breakdown in homes
Another interesting finding of our study relates to the ratio of the two main PBDE congeners found in the Penta product: While the Penta mixture contains sixty percent PBDE-99 and forty percent PBDE-47, five out of our ten dust samples contained a significantly higher percentage of PBDE-47 -— and one home contained 50 percent more PBDE-47 than expected. In other words, half of the homes tested had an abnormal ratio of these chemicals as compared to the ratio found in the commercial Penta product.
Because PBDE-99 has five bromines while PBDE-47 only has four, our data suggests that PBDEs are breaking down inside study homes. This is of particular concern because PBDE-47 is more bioaccumulative than PBDE-99 or -209. In EWG's breast milk study, for example, we found that women had at least twice as much PBDE-47 as PBDE-99 in their bodies. This finding also underscores the concern for Deca also breaking down in people's homes and the environment. With such high levels of Deca found in house dust, even if the breakdown occurs slowly or to a small degree, Deca could nevertheless be an important source of exposure to the more toxic and bioaccumulative forms of the PBDEs.
The ratio of PBDE-47 to PBDE-99 in dust samples suggest that PBDEs are breaking down into more toxic forms in many homes.
Dust and milk levels not related
Given that EWG analyzed only one dust sample per household taken at a single point in time, it was not surprising that we found no direct relationship between concentrations of PBDEs in a woman's body and in her home. (This was true for each type of PBDE, when analyzed together or alone.) PBDE concentrations in dust did not appear to be affected by the number of electronic appliances or computers, foam furniture, or recent remodeling. Diet, age, occupation and other demographic factors also failed to explain the wide variation in body burdens found by EWG in our 2003 study of PBDEs in women's breast milk.
The sources of PBDE contamination measured in human beings are currently unknown. Animal fats are the major source of PCB and dioxin exposure, and are suspected as an important source of PBDEs as well. However, several factors make it difficult to quantify PBDE exposure. First, PBDE body burdens accumulate after years of exposure. Ideally, exposure assessment would measure concentrations of fire retardants in a woman's diet, and from the air and dust in her recent homes, offices, and vehicles. Also, no study has looked at individuals' rate of uptake, metabolism and excretion of these chemicals, which is likely to play a large role in the highly variable concentrations observed in human beings. Further research will help clarify the role of household dust as direct route of exposure for children and mothers. But our preliminary comparison shows that dust ingestion may be a particularly significant route of exposure for young children.
PBDE levels in house dust vs. breast milk