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May 12, 2004

PBDEs - Fire Retardants in Dust: Dust and Indoor Pollution

Some researchers refer to house dust as an "indoor-pollution archive" or a "long-term accumulative sample" of contaminants, because contaminants accumulate in house dust over time. [48, 49, 50] Ordinary house dust is a complex mixture of pet dander, fungal spores, particulates from indoor aerosols, soil tracked in by foot traffic, VOCs and traces of metals. [51] House dust is not as exposed to moisture and sunlight which typically facilitate the breakdown of chemicals in the environment. Therefore many contaminants degrade more slowly in dust, or not at all. [52] For example, although the toxic pesticide DDT was banned in the 1970s, it was found in detectable levels in 65 percent of samples collected in Massachusetts homes and 70 percent of German homes. [47, 53]

Numerous studies have now found that the indoor environment contains higher levels of toxic fire retardants than are found outside. [54, 55] PBDEs mix with house dust as foam furniture degrades or electronic products emit chemicals through off-gassing. The high concentrations we found suggest that degrading consumer products, not emissions from industrial facilities, are the likely source of fire retardants measured in people, fish and wildlife in far-flung regions of the world.

PBDEs in dust: High levels found in homes and offices worldwide

  Study Location(s) Number of samples Total PBDEs (ppb) Deca
 Average Range Average Range
house dust United Kingdom 10 pooled samples of 10 houses each 10,543 4,254 - 20,505 9,820 3,800 - 19,900
EWG study 10 houses 4,629 614 - 16,366 (41,203) 2,394 < 400 - 7,510
Cape Cod 5 houses 3,699 1,412 - 11,426 1,232 916 - 1,472
Germany 25 houses 1,807 145 - 27,008 1,394 137 - 19,100
Norway, Finland 2 houses 267 129 - 405 180 100 - 260
office dust Netherlands, Finland, Sweden, Italy, Denmark 7 Parliament buildings 2,371 437 - 7,100 2,129 330 - 6,900
Netherlands 3 internet providers 405 311 - 546 360 260 - 490

Sources: [46, 47, 107, 108]

We also found PBDE elevated concentrations relative to other contaminants in house dust. In a recent study, researchers tested dust from 120 homes in Cape Cod, Mass., for 63 common chemicals. The average PBDE levels in EWG's dust samples were higher than most pesticides, PCBs, parabens and polyaromatic hydrocarbons found in Cape Cod. [47] More than 80 percent of the contaminants found in the Cape Cod study were found in lower mean concentrations than any of the three major PBDE congeners in EWG's dust samples.

Scientists now recognize that indoor environmental contamination poses a substantial health risk to the population. Pollution levels indoors, where Americans spend 90 percent of their time, are much higher than outdoors. [56] Efforts to examine and reduce indoor pollution have focused on a handful of agents — secondhand smoke, radon, lead paint, pesticides, formaldehyde and other volatile organic compounds (VOCs). But very little is known about the risks associated with exposure to toxic chemicals in house dust. [56]


Lead was the first environmental contaminant for which dust was found to be an important pathway for exposure. Today, many epidemiological studies have shown strong relationships between the concentration of lead in house dust and the blood of those in the home, and have confirmed that lead-contaminated house dust is a major source of lead exposure in children. [57, 58, 59]

Exposure to contaminated dust is particularly of concern for children. Not only do children spend a lot of time on floors and carpets where dust accumulates, they frequently put their hands and other objects in their mouths, increasing the ingestion of dust and the contaminants in it. [50] Children also inhale more than adults relative to body weight, and typically have more skin surface area exposed, which is important since some contaminants can be absorbed directly through the skin. [60] Overall, infants and toddlers ingest about twice as much dust as adults per day. [61] The EPA recommends that scientists estimate 100 mg dust ingestion per day for children ages 1 to 4, and 400 mg for highly exposed children. [62] Some children who compulsively eat dirt (a phenomenon known as pica behavior) may ingest ten or more times this amount. [61]

EWG's calculations show that dust is likely to be a more important PBDE exposure route for children than food. Six studies have estimated PBDE exposure in a daily adult diet for European and Canadians, reporting concentrations ranging from 13 to 213 ng/day. [55, 63, 64, 65, 66, 67] Figures for the US diet are believed to be within a similar range. [68] By comparison, when EWG calculated children's daily PBDE ingestion via dust (using median and high-end concentrations measured in our study and EPA's estimates for childhood dust ingestion), our mid-range estimate was 327 ng/day; our high-end estimate was twenty times this amount. [62] And children ingest a much smaller quantity of food than adults, this comparison is actually an overestimate of children's PBDE exposure from food.

Dust is a more significant source of
PBDE exposure for children than food

graph showing consumption of PBDE in food and in dust

Sources: [55,62,63,64,65,66,67]

In addition to being more exposed to indoor environmental contaminants via dust, children are often more susceptible to the effects of the contaminants themselves. In children, toxins have more opportunity to cause lasting damage because even small perturbations in hormone levels at the wrong time can disrupt normal brain and organ development. Age-related differences in human metabolism can also make infants and children more sensitive to chemical exposures than adults. For example, a comparison of the half-lives (a measure of how fast a chemical leaves the body) of 45 different pharmaceuticals in young children and adults found that on average it takes newborn babies 3 to 9 times longer to eliminate half of the administered dose. [69]

House dust is a reservoir for many environmental toxins: Selected results of 3 major studies

Chemical Name House dust concentration
(ppb or ng/g)
Common Uses Number and Location of Homes Sampled Source
Median Max
TBBPA, tetrabromobisphenol A ND 340 Fire Retardants 110 homes in
the UK
HBCD, hexabromocyclododecane 3,200 6,900
Tris breakdown product, 2,3-dibromo-1-propanol ND 42,800 88 homes in
Cape Cod
bisphenol A 0.8 18 Plastics additive 118 homes in Cape Cod [47]
dibutyltin 519 1,300 119 homes in the UK [46]
dioctyltin 63 545
monobutyltin 1350 2,800
monooctyltin 349 1,300
tributyltin 50 759
benzyl butyl phthalate 45.4 1,310 PVC plastic, personal care product additive 119 homes in Cape Cod [47]
bis(2-ethylhexyl) adipate 6.0 391
bis(2-ethylhexyl) phthalate 340 7,700
diethyl phthalate 5.0 111
di-N-butyl phthalate 20.1 352
bendiocarb 0.4 318 Pesticide 362 homes,
nine states
carbaryl 0.4 1,160
chlorpyrifos 0.6 324
diedrin 0.3 139
DDT 0.3 10 119 homes in Cape Cod [47]
methoxychlor 0.2 13
pentachlorophenol 0.8 8
piperonyl butoxide 0.4 624
trans-permethrin 0.4 98
methyl paraben 1.0 8 Preservative: food, cosmetics 118 homes in Cape Cod [47]
4-nonylphenol 2.6 9 Industrial detergent, personal care products 118 homes in Cape Cod [47]
nonylphenol diethoxylate 5.3 49
nonylphenol monoethoxylate 3.4 16