28/07/2007
Three recent studies published in Environmental Science and Technology show that the methods of recycling waste electrical and electronic equipment currently used at some Chinese sites generate high levels of pollution. Little information is available on the impact on the health of workers and the local population.

Particularly high levels of dioxins and furans have been measured in the atmosphere around Guiyu, South-East Asia, a major Chinese centre for E-waste recycling. Human exposure to some of these substances can lead to cancers of the skin and to reproductive disorders. "Every day, a vast quantity of E-waste - such as computers, printers, mobile phones and televisions - is processed in Guiyu", said Xinhui Bi, co-author of one of the studies. The products, which workers handle with bare hands, are submerged in open tanks containing acid and heated using blocks of coal to extract the precious metals they contain.

Atmospheric concentrations of polychlorinated dibenzodioxins and polychlorinated dibenzofurans ranging (PCDD/F) from 64.9 to 2,365 picograms per cubic metre (pg/m3), and very high levels of polybrominated dibenzodioxins and polybrominated dibenzofurans were measured in Guiyu in a study carried out by Guangzhou Institute of Geochemistry. As there are no incinerators - the usual generators of dioxins - in this town, the authors attribute the high levels of these substances to E-waste recycling. The end result is that air dioxin concentrations in Guiyu are 12 to 18 times higher than those measured in Chendian, just 9 kilometres away. The authors also claim that the levels of PCDD/F inhaled by the inhabitants of Guiyu clearly exceed the tolerable limits for ingestion defined by the World Health Organisation (WHO). "The significance of the paper is to provide us with the first estimate of what [levels] to expect," said Oladele Ogunseitan, Professor of Social Ecology at the University of California Irvine, who added: "As a next step, what needs to be done is as an epidemiological study looking for actual symptoms, but I imagine that this is not a trivial thing to do".

A joint Chinese-American study has analysed the residues produced by the combustion of plastic components and cables. In Guiyu, concentrations of polybrominated diphenyl ethers (PBDE), flame retarders used in the manufacture of cases for electronic appliances, were found to be very high (33,000 to 97,000 nanograms per gram), as were PCDD/F levels in combustion residues and in acid leaching soils (12,500 to 89,800 pg/g).

PBDE concentrations in blood samples taken from workers on recycling sites in Guiyu have also been measured as part of a joint Chinese-British study. Researchers found that blood concentrations of deca-bromodiphenyl ether (BDE-209) were 50 to 200 times higher than those of previously studied populations exposed to these substances at work. PBDEs are not classified as carcinogenic for human beings, but it has been shown that they affect thyroid metabolism and brain development in rats.

Source: HSE daily