20 July 2005: Dusting keeps flame-retardants at bay
If you want to prevent flame-retardant chemicals accumulating in your body, reach for a feather duster, say researchers in Canada.
Fire-retardant polybromo diphenyl ether (PBDE) levels measured in humans and the environment have been steadily rising since the 1970s. But, though these compounds are found in goods such as electronics and furniture, it was not clear till now how they get into the human body.
Miriam Diamond and colleagues at the University of Toronto have found that the main exposure route is via household dust, followed by eating animal and dairy products. Diamond's team used computer modelling and measured concentrations to estimate the emissions and fate of PBDEs in the Toronto area. The potential exposure routes included food, soil, dust, and inhalation of air both indoors and outdoors.
'We used estimates of how much of each type of food a "typical" Canadian eats, how much air we breathe, etc,' Diamond told Chemistry World. 'Together with measured PBDE concentrations in each - food, in air, dust, and so on - we calculated how much PBDE we expect to be exposed to.'
The toxic effects of PBDEs in humans are not known. Animal studies on rats and mice have shown an effect on the thyroid that delays puberty, and effects on brain development leading to impaired reflexes, memory and learning that worsen with age.
Toddlers often have high body burdens of PBDEs, possibly because they put dusty objects from the floor into their mouths. Breastfeeding infants have the highest levels, with PBDEs detected in breast milk. 'Their occurrence in breast milk with concentrations increasing over time in North America is the major impetus for us doing the exposure assessment,' said Diamond. 'We hypothesise that women with very high PBDE concentrations in breast milk may be super-exposed; it seems likely that if one reduces one's exposure, then presumably the breast milk concentrations will fall.' Levels of PBDE in humans are reportedly much higher in North America than in Europe.
An earlier study on Swedish electronics factory workers, who are regularly exposed to PBDEs, found that levels in their blood decreased when they took holidays, lending weight to the theory that PBDEs may not be persistent in the body.
The penta- and octa-bromodiphenyl ethers are banned in the EU, which is currently considering a voluntary phase-out of a third type, deca-bromodiphenyl ether. Diamond says that the EU should revisit this, since the deca-bromodiphenyl ether degrades into the penta- and octa- versions of the molecule.
Diamond's advice to consumers is to eliminate dust, especially if you have toddlers - by minimizing carpeting, for example. 'Don't intentionally introduce potentially large sources of PBDEs to your home when you have toddlers, such as a new mattress or foam furniture. Ensure good ventilation, especially in rooms where you have potential sources of PBDEs, such as televisions, computers, and foam furniture.' And don't forget your feather duster.
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