E-waste chemicals change workers DNA

May 31, 2008

Wen, S, F-X Yang, Y Gong, X-L Zhang, Y Hui, J-G Li, A-L Lui, Y-N Wu, W-Q Lu and Y Xu. 2008. Elevated levels of urinary 8-hydroxy-2’-deoxyguanosine in male electrical and electronic dismantling workers exposed to high concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans, polybrominated diphenyl ethers, and polychlorinated biphenyls. Environmental Science and Technology 42:4202-7.

Chinese factory workers who dismantle computers and other electronic equipment waste (E-waste) are chronically exposed to high levels of dangerous chemicals that damage their DNA and are known to cause a variety of health ills. This study highlights the high exposures and health hazards associated with handling E-waste under less controlled conditions. Workers had more damaged DNA than non-factory workers, 5-times more altered DNA after work than before and higher levels of some chemicals than reported in U.S. workers. Dust samples from the factories contained orders of magnitude higher levels of chemicals than have been reported in other worldwide studies. Many adverse health effects have been linked to the pollutants and this type of DNA damage can lead to cancer and premature aging.


More than 50 million metric tons of E-waste (old and outdated electronics, such as computers, cell phones and fax machines) is produced worldwide each year. Experts speculate this number will rapidly increase well into the future.

Currently the vast majority of this waste is sent to developing countries, such as SE China. There, workers manually dismantle the equipment to reclaim the copper and other prized materials found in the products. Much of the E-waste is crudely processed, often by open burning, which releases a range of highly toxic contaminants (e.g. dioxins, insulators (PCBs), fire retardants (BDEs), heavy metals) into the environment.

The so-called persistent organic pollutants, or POPs, make up a large part of the chemical residue from E-waste recycling. The long-lasting substances accumulate in fat and are known to contaminate air, soils, sediments, animals and people. They can cause a range of health problems, including cancers, immune system problems and reproductive dysfunctions.

DNA damage is one common effect when POPs interact with cells. The mingling produces oxygen radicals, which are free roaming oxygen atoms. The rogue oxygens can change the cell’s DNA structure and alter its function in ways that can lead to disease and premature aging.

Many recent studies report that the soil, plants and animals (including rice, fish and other food sources) near E-waste processing sites in China are highly polluted with hazardous chemicals released during the dismantling and burning activities. Not surprisingly, dust samples from the factories themselves contain high levels of dangerous chemicals, including POPs and heavy metals (). Even though the workers, who handle the waste and breath the dust and smoke, bear the brunt of the exposures, little is known about the health hazards they face during a typical day.

Researchers collected and analyzed hair and urine samples from workers and indoor dust samples for organic pollutants at two electronics dismantling factories in East China during July 2006. The 64 male workers who participated in the study were between 18 and 60 years old and had been working at the factory for a minimum of one-year.

Researchers collected hair samples from workers before they started their shift. Hair can reflect exposure to pollutants because, as it grows, it incorporates contaminants circulating in the body. Hair samples were washed to remove surface (dust).

DNA damage from chemical exposure was determined by comparing levels of a chemical marker found in urine samples taken from each participant before and after work on the same day. The marker, 8-hydroxy-2’-deoxyguanosine (8OH-dG), is used to estimate oxidative DNA damage and cancer risk.

Indoor dust was sampled at three factories that had been in use for between 6 and 8 years.

Hair, urine and dust samples were analyzed for total dioxins (polychlorinated dibenzo-p-dioxins and dibenzofurans, PCDD/Fs), flame retardants (polybrominated diphenyl ethers, PBDEs) and PCBs (polychlorinated biphenyls). The researchers examined specific chemical patterns as a way to identify the main source of each of the accumulated chemicals.

Almost every targeted type of PCDD/Fs, BDEs and PCBs the researchers looked for were found in all but a few hair samples analyzed. In all, only three PCBs were absent from some of the hair samples.

Chemicals levels in the dust samples were orders of magnitude higher than those reported in other published studies. For example, PCDD/Fs levels were more than 500 times higher than those found in house dust from Japan and 5-10 times higher than dust collected from other electrical plants. Total PCB levels were nearly 1,000 times greater than those reported from the US. Similarly, BDE levels were 2 times higher than the highest indoor dust samples collected in the US.

The workers' hair was contaminated with the highest published concentrations of PCDD/Fs, BDEs and PCBs. Only a handful of published studies report amounts of these compounds in hair so there is little existing data to compare the current results with. However, PCDD/Fs were between 20 to 40 times higher than other Chinese and Japanese workers. PCB levels were nearly 100 times greater when compared with some Chinese and Belgium studies. Potentially this may mean that the workers have high body burden levels of these chemicals, although blood or tissue samples were not analyzed.

The dioxins, flame retardants and PCBs measured in hair and dust came mainly from the open and uncontrolled burning of the e-waste. The major flame retardant found, BDE-209, known as deca, is also the most widely used in electronic products. Interestingly, the range of PCB types identified in the people and the dust reflects their heavy historical use in transformer capacitors and in the area's past as the place where the capacitors were dismantled.

Measured levels of the oxidized DNA biomarker in the workers' pre-shift urine were higher than those in the general Chinese population. However, a huge increase in this DNA damage marker was seen in post-shift workers. Levels were nearly 5 times higher after work than before work. These sharp increases indicate that workers' cells experienced oxidative stress during the work shift. Other E-waste pollutants, such as heavy metals, may also play a role, but this study did not identify which contaminants were responsible . The high levels of DNA damage reported are much higher when compared to workers with other occupational exposures and close to the elevated concentrations that are typical in some cancer patients.

What does it mean?

This is one of the first studies to report the very high exposures to dangerous chemicals and health hazards in Chinese workers who handle E-waste under less controlled work situations that are typical in countries that dismantle most of the world's old electronics. Workers had some of the highest levels and widest range of chemicals ever found.

The results suggest burning the e-waste is a dangerous practice. Burning releases many of the toxic chemicals into the environment where it settles in dust, is breathed by people and contaminates food sources and wildlife.

Indoor dust from these E-waste dismantling factories contains extremely high levels of toxic chemicals - orders of magnitude higher that levels found in other studies of indoor dust. Potentially, as the authors suggest, this dust should be considered a hazardous waste and should be disposed of appropriately.

Chemically-laden dust can be inhaled or eaten (via hand-mouth contact) by people. Indeed, the elevated levels of these chemicals in the hair samples of these workers suggests that this is the case and reducing exposure of these workers to these toxic by-products should be a priority for worker safety.

The cellular DNA damage, caused by the constant exposure to the waste, may increase the risk of cancer and lead to serious health problems for the workers exposed to these heavily toxic pollutants. The highly elevated levels of the DNA damage biomarker seen in workers after their work shifts demonstrates that the E-waste causes oxidative stress and resultant DNA damage. The DNA biomarker levels are nearly as high as those seen in cancer patients. There is a high potential cancer risk originating from the E-waste sites.

E-waste and its disposal are major world problems. Contaminants from the materials are getting into workers and affecting their cell processes. More stringent worker protection and controlled burning facilities are probably necessary to keep these toxic chemicals out of the environment and people.


Chatterjee, R. E-waste recycling spews dioxins into the air. Environmental Science and Technology, July 11, 2007.

Harder, B. Toxic "E-waste" gets cached in poor nations, report says. National Geographic News, November 8, 2005.

Johnson, J. 2008. A tsunami of electronic waste. Chemical and Engineering News 86:32-33.

Leung, AO, NS Duzgoren-Aydin, KC Cheung and WH Wong. 2008. Heavy metals concentrations of surface dust from e-waste recycling and its human health implications in southeast China. Environmental Science and Technology. 42:2674-80.

Wray, R. Breeding toxins from dead PCs. The London Guardian, May 6, 2008.

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