ES&T Online News: E-waste recycling spews dioxins into the air

ES&T Online News: E-waste recycling spews dioxins into the air

When computers, televisions, music systems, and other electronic products reach the ends of their lives, they often end up in China or other developing countries as e-waste. Such waste is a serious environmental threat in these parts of the world because of the poorly regulated conditions under which the waste is dismantled. A new study published in ES&T (DOI 10.1021/es0702925) shows that Guiyu, a major e-waste recycling center in China, has the highest documented levels of atmospheric polychlorodibenzo-p-dioxins (PCDDs) and polychlorodibenzofurans (PCDFs) in the world.

In e-waste recycling centers in China, discarded products are dipped into open pits of acid and heated over grills fueled with coal blocks to extract precious metals, such as gold. These processes often release toxic metals, such as lead, and organic compounds, such as dioxins. The emissions are not regulated, and occupational exposure is high because of the poor working conditions for e-waste recycling laborers.

In March 2007, researchers at Hong Kong Baptist University showed that soil at e-waste recycling sites in China has high levels of dioxins and polybrominated diphenyl ether (PBDE) flame retardants. (Read the paper at ES&T‘s ASAP website.) More recently, another study published in ES&T showed that the workers at these sites have blood levels of the heavy PBDE, BDE–209, 50–200 times higher than those previously reported. Whereas dioxins are potentially carcinogenic for humans, PBDEs affect thyroid metabolism and brain development.

In the current study, Ping’an Peng of the Guangzhou Institute of Geochemistry (China) and his colleagues sampled the air from Guiyu for a week in both the summer and the winter and analyzed the samples for 2,3,7,8-PCDD/Fs. The levels varied between 64.9 and 2765 picogram per cubic meter (pg/m3). The toxic equivalents (TEQ)—a value used to account for the different levels of toxicity of the individual dioxins—was 0.909–48.9 pg TEQ/m3. Given that Guiyu has no municipal or medical solid-waste incinerators, which are known to be major sources of dioxins, the authors attributed the elevated dioxin levels to e-waste recycling.

The team also found that the dioxin concentrations in the air around Guiyu were 12–18 times higher than those in Chendian, a town 9 kilometers (km) from Guiyu, and 37–133 times higher than those in Guangzhou, which is 450 km from the e-waste site. The results suggest that dioxin pollution from e-waste recycling is spreading to nearby areas.

When they calculated the exposure of adults to dioxins through inhalation, the researchers found that it (68.9 and 126 pg TEQ per kilogram per day in the summer and winter, respectively) was a whopping 15–56 times higher than the World Health Organization recommended maximum of 1–4 pg TEQ/kg/day.

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