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Recycling and disposal of electronic waste: Health hazards and environmental impacts
Responsible organisation
2011 (English)Report (Other academic)
Abstract [en]

E-waste is a generic term comprising all electrical and electronic equipment (EEE) that have been disposed of by their original users, and includes everything from large household appliances, such as refrigerators, microwave ovens, television sets, and computers, to hand-held digital apparatuses, cell phones and toys. E-waste is today the fastest growing sector of the municipal solid waste stream and currently comprises more than 5% of its total flow, which is equivalent to 20-50 million tones a year worldwide. These enormous quantities in combination with the fact that e-waste contains a wide range of hazardous compounds have turned e-waste into a global environmental issue. When the e-waste is taken care of, either in general waste processes or in recycling processes, these hazardous compounds may be released and thereby become a threat to humans and the environment. In addition, in some processes used, new hazardous compounds, such as dioxins, may be formed as the original e-waste components are degraded. Consequently, to avoid serious impacts on human health and the environment it is crucial to ensure that e-waste is properly taken care of, all the way from collection and handling through recycling and disposal. However, e-waste also contains several valuable components, such as precious metals and various plastics that may be profitable to extract during the end-of-life treatment processes. This adds an economical incentive to process e-waste adequately. The best option, both from an environmental and a recovery efficiency point of view, is unquestionably to recycle the e-waste in modern recycling facilities using state-of–the–art technologies with efficient emission control systems. However, due to insufficient legislation and recycling collection systems in many countries, this option is seldom practiced, when seen on a global scale. Instead a large part of the e-waste generated in the world is sent, mostly illegally, to developing countries such as, China, India, Nigeria and Ghana, where the ewaste is disassembled by poor people using rudimentary methods, in the hunt for valuable materials. Another large fraction of the e-waste generated in the world is treated as general municipal solid waste, and is thus incinerated in waste incineration facilities or just put on landfills. Only a minor fraction (around 10%) is treated in recycling facilities adapted for its purpose. Even if all end-of-life treatment processes creates emissions of hazardous compounds, that may have negative impacts on human health and the environment, some processes are worse than others. This report summarizes and compares the hazards and risks that may arise in different processes. The compounds of concern are several and include organic as well as inorganic compounds. The organic compounds include various brominated flame retardants, brominated and chlorinated dioxins (PCDD/Fs and PBDD/Fs), brominated and chlorinated benzenes and phenols, polychlorinated biphenyls (PCBs) and naphthalenes (PCNs), polycyclic aromatic hydrocarbons (PAHs), nonylphenol, organophosphorus flame retardants, phthalate esters and freons. The inorganic compounds include antimony, arsenic, asbestos, barium, beryllium, cadmium, chromium, copper, lead, mercury, nickel, selenium, tin, yttrium, and zinc. Some are of concern because they are very toxic and other mainly because they are very abundant in e-waste. There are also some more discrete chemicals present in ewaste that may be of concern. These are liquid crystals from liquid crystal displays (LCDs), toner dust from toner cartridges and nanonparticles from various products. The components and materials that are of most concern are: printed circuit boards (PC-boards), batteries, cathode ray tubes (CRTs), LCDs, plastics, PCB-containing capacitors, equipment containing freons, toner cartridges and various mercury containing components. Most risks arise during the uncontrolled e-waste recycling activities that occur in developing countries, and are results of the rudimentary methods used. These include manual disassembly and sorting; heating and acid leaching of printed circuit boards (PC-boards); shredding, melting and extrusion of plastics; open burning of plastic coated wires and other components; and sweeping and collection of toners from toner cartridges. These activities are mostly carried out directly on the ground in open air or in poorly ventilated workshops, and involve minimal emission control systems and personal protection for the workers. Humans and the environment in the areas where this is carried out may therefore be highly exposed to the emissions generated. The recycling workers and the local residents are particularly exposed via dust generated during dismantling and shredding processes, and fumes and smoke generated during acid digestion processes and various high temperature processes, such as open burnings and heating, melting, and extrusion processes. The environment is mainly contaminated from the open burning processes and through leakage from dumped residues of various recycling activities, e.g. stripped cathode ray tubes (CRTs) and PC-boards, spent acids from the digestion processes and residual ashes. The compounds of most concern during these activities vary depending on the material being recycled and the methods used. However, on the whole, lead seems to be particularly problematic among the metals, and dioxins (chlorinated and brominated) and polybrominated diphenyl ethers (PBDEs) among the organic compounds. These compounds are all very toxic and may potentially be emitted in large amounts during rudimentary e-waste recycling activities. Lead and PBDEs because they both are highly abundant in e-waste, and dioxins because the formation conditions many times are ideal in the processes used. As a consequence, extremely high levels (in some cases the highest ever measured) of these compounds have been measured in environmental as well as human samples collected in areas where uncontrolled e-waste recycling is taking place. These have also been connected to various negative health effects observed among the people in these areas. Regarding the dioxins, it seems like the brominated and the mixed brominated/chlorinated congeners contribute to the total dioxin-like toxicity to at least the same extent as the purely chlorinated congeners, which is important to remember as most monitoring campaigns only include analyses of chlorinated dioxins. Furthermore, there are convincing evidences that the emissions from the uncontrolled e-waste recycling industry are contributing significantly to the regional as well as the global pollution for some compounds. Risks also arise when e-waste is treated as general municipal solid waste. During incineration, a wide variety of hazardous compounds may be emitted to the atmosphere via the smoke and exhaust gases, both in gaseous form and bound to particles. The compounds emitted may be those that were present in the original waste, but probably more important are those compounds that may be formed during the incineration processes, e.g. PCDD/Fs and PBDD/Fs. This is because the e-waste, being a complex fuel, may function as precursors for many different compounds in thermal processes. In fact, the conditions for dioxin formation are many times ideal when e-waste is incinerated, which is partly due to the presence of PVC-plastics and BFRs as dioxin precursors and partly due to the presence of copper and antimony as very potent catalysts in the transformation reactions. In modern incineration facilities the emission of these and other compounds may be minimized by process optimization and flue gas treatment systems. However, during open burning of e-waste, as occurs in many developing countries, the emissions may be substantial. Besides dioxins, a number of other pollutants are emitted in large quantities, e.g. PAHs, various chlorinated and brominated compounds and several metals, including lead, copper, antimony, zinc, tin, arsenic, nickel, chromium, cadmium, barium and beryllium. In addition to the atmospheric emissions, hazardous compounds may leak from the residual ashes to the ground and to aquifers in the surroundings. However, this has so far been scarcely investigated. During landfilling, hazardous compounds may leak to the surrounding environments, including nearby surface water and groundwater reservoirs, and also evaporate to the atmosphere. Leakage may occur for most compounds in the waste due to the long time spans involved, but of particular concern are the leakage of lead and various other metals, as well as PBDEs and phthalate plasticizers. Evaporation mainly occurs for volatile compounds, of which mercury and its methylated derivatives are of most concern. The extent of leakage and evaporation from a landfill depends on the properties of the contaminants in question, but also on the design of the landfill (i.e. if it is open or sealed), the properties of the material being stored (e.g. type of waste, if it has been pre-treated in some way etc.), and on various environmental factors (such as the ambient temperature and pH and humic content in the infiltrating water). Recycling under controlled conditions that are carried out in facilities adapted for its purpose is much better from a risk perspective point of view, both for the recycling workers, the local residents, and for the environment. However, risks may occur during these activities as well. For the workers, the largest risk is to be exposed to dust during dismantling, shredding and separation of the e-waste as well  as during the subsequent pyrometallurgical processes. In addition, workers may be exposed to volatile compounds, such as mercury, that may be accidentally released during breakage of components in which these compounds are encapsulated. For the environment and the general population, the largest risks arises during the pyrometallurgical processes and during other high temperature processes, such as those used during plastic recycling and incineration of residual waste (justified in the recycling industry as energy recovery). During these, substantial amounts of PCDD/Fs and PBDD/Fs as well as other chlorinated and brominated compounds may be emitted, and in case of the pyrometallurgical processes, a wide range of metals (similar to the once emitted from uncontrolled processes) may also be emitted. Even if these emissions should be possible to minimize by using optimized processes together with modern dust containment and flue gas treatment systems, existing emission data indicate that this is not always satisfactorily done. Significant levels of several compounds have thus been found in and around some of these facilities.  From this, it can be concluded that there is no completely safe end-of-life process available to deal with the e-waste of today. Controlled recycling is much better than uncontrolled recycling, incineration or landfilling, but hazards and risks will occur in all cases. This is simply a consequence of the multitude of hazardous compounds that are present in e-waste. To reduce the risks further, cleaner products containing less hazardous compounds have to be produced. Furthermore, to solve the e-waste problem in a wider perspective, the quantities of e-waste generated have to be reduced. Besides by decreasing the consumption, products with greater life-spans that are safer and easier to repair, upgrade and recycle have to be developed. The ultimate goal must be to ensure that the quantities of e-waste generated are minimized, and that the e-waste which does arise is recycled and disposed of in the best achievable manner to minimize impacts on human health and the environment.

Place, publisher, year, edition, pages
Stockholm: Naturvårdsverket, 2011. , p. 135
Series
Rapport / Naturvårdsverket, ISSN 0282-7298 ; 6417
National Category
Environmental Sciences
Identifiers
URN: urn:nbn:se:naturvardsverket:diva-9382ISBN: 978-91-620-6417-4 (print)OAI: oai:DiVA.org:naturvardsverket-9382DiVA, id: diva2:1616514
Available from: 2021-12-03 Created: 2021-12-03 Last updated: 2021-12-03Bibliographically approved

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