Human health risk assessment based on trace metals

Title: Human health risk assessment based on trace metals in air and dust from e-waste recycling workshops in Hong Kong, China

Authors: Winifred Ka-Yan LAU Peng LIANG Brian Yu-Bon MAN Shan-shanCHUNG*, and Ming-hung WONG,* Department of Biology, Hong Kong Baptist University, Kowloon Tong, Hong Kong

*

– Tel: (852) 34117741; Fax: (852)34117743; email: [email protected]

- Tel: (852) 34117745; Fax: (852)34117743; email: [email protected]

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Abstract Trace metal contamination in e-waste recycling workshops are considered a significant health hazard to workers. The extent of trace metal contamination (Cd, Cr, Cu, Pb, Hg, Zn) was evaluated in suspended air particulates, surface dust and floor dust collected in 4 formal and 1 informal e-waste recycling workshops in Hong Kong. Human health risk assessments were subsequently carried out to evaluate cancer and non-cancer risks as a result of exposure to floor dust through the ingestion, dermal contact and inhalation pathways. It was found that in general, trace metal concentrations were highest in air particulates (Cd 38.6, Cr 593, Cu 142, Pb 824, Ni 485, and Zn 4456 ng/g) and surface dust (Cd 3.65, Cr 51.9, Cu 431, Pb 582, and Ni 93.1 µg/100 cm2) collected from the dismantling area. Concentrations of trace metals in floor dust were found to be more varied between different work areas. In addition, it was found that workers in the desoldering and loading areas were exposed to Pb concentrations in floor dust with calculated blood lead levels of 39.5 µg/dl and 35.8 µg/dl respectively. Risk assessment calculations indicated that workers may be exposed to a cancer risk above the acceptable range in the dismantling and chemical waste areas in formal e-waste recycling workshops. E-waste recycling workers should be informed of the associated risks and should be protected against the hazards of e-waste recycling activities in Hong Kong.

Keywords: Electronic Waste; Trace Metals; Dust; Risk Assessment; Occupational Safety and Health; Hong Kong

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1. Introduction Problems associated with electronic waste (e-waste), one of the fastest growing components of the solid waste stream in the world today, have been extensively studied by the scientific community in the past decade. Part of the problem associated with recycling e-waste lies with the disassembly of different materials, some containing toxic chemicals which may be released into the environment if improperly handled (Tsydenova and Bengtsson, 2011). Currently in Hong Kong, both formal and informal e-waste recycling sectors co-exist. The Hong Kong Government estimated in 2010 that approximately 80 percent of locally generated e-wastes were recycled but the majority were exported overseas by second-hand dealers in the informal sector (Environment Bureau, 2010). There are a few recyclers in Hong Kong’s formal e-waste recycling sector. However, their current capacity is considered insufficient to cater for future needs and their business only focuses on the treatment of computers or off-specification equipments (Environmental Protection Department [EPD], 2011). Thus, to regulate and effectively manage Hong Kong’s e-waste problem the Hong Kong Government intends to set up a formal e-waste treatment facility for local e-waste under a producer responsibility scheme (PRS), prioritizing the local treatment of televisions, washing machines, air-conditioners, refrigerators, and personal computers (TWARC waste) which are thought to comprise 86% of all local e-wastes by weight (Environment Bureau, 2010).

Since information about the current practices of Hong Kong’s e-waste recycling industry is lacking, there is an urgent need to provide information for developing 47

sustainable local e-waste treatment options. In this regard, it is exigent to identify potential risks associated with the local e-waste recycling industry such that adequate safety and protection measures may be put in place to mitigate hazards for the present and in the future. Exposure to chemical risks is one of the most significant human health hazards that have been studied (Deng et al., 2006; Wong et al., 2007; Leung, et al., 2008; Ma et al., 2009). Over 1000 different chemicals can be found in e-waste, some of which are toxic to humans. The e-waste stream is very heterogeneous as there are multitudes of design for each type of electrical and electronic equipment (EEE) available on the market with each comprising several types of materials. The chemical composition of e-waste is also dependent on the brand, type and age of the product discarded. Although it is difficult to generalize the material composition of the e-waste stream, metals are thought to comprise over 60.2% of materials used in EEE and contributes as much as 70% of the trace metals (Hg and Cd) being sent to the landfills in the United States (Widmer, et al., 2005). Printed circuit boards (PCBs) and cathode ray tube (CRT) TVs contain the highest Pb concentrations (Matsuto, et al., 2004). Despite significant recycling, Cu from e-waste on the other hand, is thought to be contributing to the 5000 tonnes of annual global Cu emission into the environment (Gaidajis, et al., 2010).

Chung et al. (2011) estimated that Hong Kong households generate no more than 80,443 tonnes of TWARC wastes each year. Given that the majority of e-wastes are processed through the informal sector (Environment Bureau, 2010) with sporadic locations in the city, trace metals contained in the TWARC wastes can potentially 47

leach out into the environment and be exposed to humans. Bearing in mind that the figure estimated by Chung et al. (2011) only forms a portion of the e-waste in Hong Kong, significantly higher amounts may be stored and processed within the city each year. While the toxicities of e-waste are well recognized, potential risks, safety and health implications of e-waste treatment and handling practices in Hong Kong are not. Deeper understanding into the present handling of different TWARC waste treatment methods can increase the awareness of the public and workers and contribute to establishing a set of guidelines to protect worker safety.

Given limited data availability, the specific objectives of this study are to evaluate the extent of trace metal (namely Cd, Cr, Cd, Pb, Hg, Ni, and Zn) contamination in air particulates and dust in e-waste recycling workshops operating in Hong Kong and to conduct a risk assessment to estimate potential health risks posed to workers.

1.1 Trace metals in e-waste Although e-wastes compose of a large range of materials, the majority of hazardous substances are found in certain components of EEE.

Table 1 provides a summary of

the trace metals commonly found in e-waste components. Out of all e-waste components of concern, CRTs contain the greatest amount of trace metals, with Pb values ranging from 1 – 3 kg (Tsydenova and Bengtsson, 2011). In contrast, PCBs contain about 16% copper, 4% solder and 2% nickel along with other precious metals such as gold and palladium, which account for approximately 90% of the intrinsic 47

value of most scrap boards (Ogilvie, 2004). Regarding toxicities of liquid crystal display (LCD) monitors, the least known aspect is the harmful effects of liquid crystals on human health. There are over 1000 marketed liquid crystals with formulations containing approximately 250 different substances. While liquid crystals are suspected to be hazardous because of the potential toxicity and carcinogenicity of some of the substances concerned, studies on their toxicities are scarce and inconclusive (Loew, 2000;Tsydenova and Bengtsson, 2011). [insert Table 1 here]

1.2 Trace metals in the environment from e-waste related recycling activities Multiple studies have documented environmental and health effects of uncontrolled e-waste recycling processes contaminating environmental media such as soil, air, surface water and sediment in developing countries. For example, in the BAN & SVTC report (Puckett et al., 2002), a single water sample taken in Guiyu from a location adjacent to a PCB processing area revealed that Pb levels exceeded the WHO Drinking Water Guidelines by 190 times while a sediment sample taken near the same location revealed that Pb and Cd levels exceeded USEPA Sediment Screening Benchmarks by almost 775 and 1338 times respectively. Similarly Brigden et al. (2005) found that concentrations of Cu, Pb, Sn, Ni, and Cd in sediments taken from discharge channels of mechanical shredder workshops in Guiyu were between 400 – 600 times higher compared to uncontaminated sediments. In the same study, dust samples collected from the floor of e-waste recycling workshops undergoing

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manual PCB separation and solder recovery in Guiyu, found Pb concentrations (31 300 – 76 000 mg/kg) hundreds of times higher than typical levels in indoor dusts.

In a paper published by Leung et al. (2008) on trace metal concentrations in surface dust from e-waste recycling workshops of Guiyu, Pb levels detected ranged from 22 900 – 206 00 mg/kg which exceeded the Dutch Intervention Values for soil by 43 – 289 times and Cu and Zn were 6 – 188 and 1.4 to 14 times higher than the Dutch Intervention Values respectively. Floor dust samples collected from adjacent roads, a schoolyard, and an outdoor food market showed that public places were also adversely affected. Elevated concentrations of metals were also observed in ambient air in Guiyu. Both TSP and PM2.5 (samples with aerodynamic diameter smaller than 2.5µm) were analysed for Cd, Cr, Cu, Ni, Pb, Zn, Mn and As in Deng et al. (2006). TSP and PM2.5 fractions were most enriched with Cr (1161 and 1152 ng/m3, respectively) Zn (1038 and 924 ng/m3), Pb (444 and 392 ng/m3), Mg (60.6 and 25.42 ng/m3), and Cu (483 and 126 ng/m3). Levels were found to be higher than those observed at other sites in Asian metropolitan cities such as Tokyo, Shanghai and Seoul (Deng et al., 2006). Freshwater ecosystems in Guiyu have also been affected by the intensive e-waste recycling industry. Wong et al. (2007) found higher dissolved metal concentrations in waters of Lianjiang and Nanyang Rivers within Guiyu in comparison to a reservoir outside Guiyu. Lianjiang was enriched with dissolved As, Cr, Li, Mo, Sb and Se, while Nanyang River had elevated levels of dissolved Ag, Be, Cd, Co, Cu, Ni, Pb, and Zn. High levels of metals were attributed to strong acid leaching processes which took place along the river. At another e-waste recycling hub 47

in China, Taizhou, paddy soil, polished rice and relevant hull samples were analysed for As, Ba, Cd, Co, Cr, Cu, Hg, Mn, Ni, and Pb by Fu et al. (2008). Cd, Cu and Hg in soil samples were found to be 1.19, 9.98 and 0.32 µg/g, respectively and have exceeded the maximum allowable concentration for Chinese agricultural soils by 4.0, 2.0 and 1.1 folds (0.30, 50.0, 0.30 µg/g, respectively). The geometric mean of Pb in polished rice reached 0.69 µg/g which was 3.5 folds higher than the 0.20 µg/g safety criterion for milled rice in China, providing evidence that trace metal contamination from uncontrolled e-waste recycling can potentially be extended to affect a much larger population.

1.3 Occupational Exposure Limits Given the high exposures to trace metals discussed in the previous section, acceptable concentration of hazardous substances in the workplace defined by competent authorities is needed. In 2002, the Labour Department of Hong Kong approved a statutory Code of Practice on “Control of Air Impurities (Chemical Substances) in the Workplace” under Section 7A(1) of the Factories and Industrial Undertakings Ordinance which lists occupational exposure limits (OEL) for over 230 substances, including trace metals, commonly found in the workplace environment. OELs were adopted mainly from Threshold Limit Values (TLVs) of the American Conference of Governmental Industrial Hygienists (ACGIH). Although failure to observe the conditions stipulated in the Code of Practice is not an offense but it may serve as a factor in determining whether or not safety and health provisions under the Ordinance has been breached in a criminal court (Tsin, 2006). In addition to ACGIH’s TLVs, 47

other organizations in the United States have recommended OEL to protect worker health and safety. The two that are most often cited with ACGIH’s TLVs are the OSHA permissible exposure limits (PELs) and NIOSH’s Recommended Exposure Limits (RELs). NIOSH’s RELs were developed by NIOSH and OSHA under the Standards Completion Programme while OSHA’s PELs were largely derived from ACGIH’s TLVs. Despite the different sets of standards, OSHA’s PELs are the only enforceable regulatory limits on the amount or concentration of a substance in the air in the United States. ACGIH’s TLVs and NIOSH’s RELs are both recommended guidelines and are left to the discretion of the user. It should be noted that although legally binding, OSHA’s PELs are not updated regularly owing to requirements, such as the standards and limits are required to be technologically and economically feasible, under the Occupational Safety and Health Act. NIOSH’s RELs and ACGIH’s TLVs on the other hand, are updated periodically based on the latest information on health effects of exposure of substances concerned (McCluskey, 2003).

Regarding the surface environment and that of floor dusts, with the exception of USEPA’s regulation for Pb in house dust at 40 µg/ft (431 µg/100 cm2) on floors based on the collection of house dusts using the wipe method (USEPA, 2001), there are currently no international guidelines or standards governing trace metal content in surface or floor dust.

2. Methodology 47

This is the first study that characterises the risk of e-waste recycling on Hong Kong e-waste recyclers and contribute information to ensuring workers’ health and safety for such future facilities. Owing to its ubiquitous nature, dust was selected as the environmental medium to be tested in this study. Elemental compositions and concentrations in dust can reflect the characteristics of both short- and long-term activities in the area (Leung et al., 2008) and hence was considered to be suitable for comparison between different e-waste recycling workshops. Consent was solicited at all five of the major formal e-waste recycling workshops in Hong Kong. Formal e-waste recycling workshops are believed to be the dominant e-waste processors in Hong Kong where in addition to collection and storage, dismantling of e-waste into separate components and further processing such as cable shredding or desoldering are conducted on-site. The work processes observed in the formal recycling workshops have been previously reported in Lau and Chung (in press). Briefly, the major work processes in Hong Kong’s formal e-waste recycling workshop include: cable shredding, chemical waste treatment, desoldering, manual dismantling, on- and off-loading, office activities, repairing and storage. In contrast, very limited information is available on the processes that occur in informal e-waste recycling workshops most of which are believed to act as open storage sites with very limited treatment capabilities, if any. Owing to the sensitivity of the nature of work within informal e-waste recycling workshops, the exact number of informal traders in Hong Kong is not known, making the use of probability sampling methods difficult. District councils, the Heung Yee Kuk, a statutory advisory body representing the 47

interests of establishments in the New Territories, village representatives, and e-waste traders were contacted for introduction to informal e-waste traders. In the end, four formal e-waste recycling workshops and one informal e-waste recycling workshop granted permission to conduct sampling on their premises. The informal e-waste recycling workshop sampled is an open storage site situated in the Northern New Territories with a small semi-covered shelter. It serves as a temporary storage site for transient e-waste going into developing countries. In general, the two major work processes adopted at the informal e-waste recycling workshop were the loading and storage of e-wastes.

Owing to the small sample size of informal e-waste recycling workshops, the data obtained are not likely to be representative of the informal sector. However, they can still serve as a crude comparison to the data obtained from the formal e-waste recycling workshop. Findings obtained from the local formal e-waste recycling workshops sampled on the other hand, were considered to be representative and can reflect the actual situation within such premises so that OSH risks as a result of trace metal exposure in dust posed to workers undergoing similar e-waste recycling activities could be investigated. In addition to floor dust, suspended air particulates, and surface wipes were also collected from specific work processes carried out at the workshops to differentiate the associated trace metal concentrations. For comparison, identical samples were also collected from an empty workshop with no prior e-waste recycling activities.

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2.1 Sample collection and preparation Deposited floor dust samples were collected from the e-waste workshops using a plastic whisk broom and dustpan in a gentle sweeping action to collect the fine particulates. The collected samples were stored in pre-treated paper bags (heated at 50°C overnight to remove volatiles) and placed in sealable polyethylene bags to be taken back to the laboratory. Sample locations consisted of both indoor and outdoor sites, depending on the layout of the workshops, and were in close proximity to work areas. Usually one sampling was not sufficient to collect all the dust required for analyses and re-visits may be necessary. At the laboratory, dusts from each location were homogenized, sieved (10% respectively while floor dusts were digested in triplicates. An average of three replicates of standard reference material (SRM) from the National Institute of Standards and Technology [NIST] (NIST SRM 2584) Trace Elements in Indoor Dust and analytical blanks were included in every batch of microwave acid digest. The SRM for wipe sampling was prepared by unfolding a Ghost Wipe ™ and placing 0.2 g of NIST SRM 2584 onto the centre of the wipe. The wipe was then folded inward and handled in the same way as that for the samples. SRMs were used to calculate the recoveries of all investigated elements which were considered satisfactory and the ranges are presented in Table 2. Owing to insufficient samples, Hg concentrations were not measured in air and wipe samples. [insert Table 2 here]

2.4 Statistical Analyses All statistical analyses were performed with SPSS (version 17, SPSS, Chicago, IL, USA). All data were tested for goodness of fit to a normal distribution with Kolmogorov- Smirnov’s one sample test. Since all of the data were found to deviate from the normal distribution, the data were log-transformed prior to performing the one-way ANOVA test to compare the means of different groups. Spearman’s rank correlation coefficients were subsequently calculated to determine relationships 47

among different metals. The probability value of p1, there may be concern for potential health effects, otherwise, it is assumed to be negligible.

∑

(Equation 6)

In calculating cancer risk, the lifetime average daily dose (LADD) was calculated according to RAGS (Part A) (USEPA, 1989) for cancer risks as a result of ingestion and dermal contact and RAGS (Part F) (USEPA, 2009) for cancer risks as a result of inhalation using Equations 7 and 8 respectively.

Cancer risk = LADD x SF

(Equation 7)

where SF = slope factor Cancer risk = IUR x EC

(Equation 8) 47

where IUR = inhalation unit risk (µg/m3)

Human health risk assessments above could not be conducted for Pb because no consensus could be established in deriving aRfD for Pb. One of the methods to relate Pb concentrations to human health is by estimating blood lead levels (BLL) of workers. The World Health Organisation (WHO) has reported that BLL in the range of 10 – 15 µg/dl can cause adverse health effects while the Centres for Disease Control and Prevention (CDC) has also established a limit of 10 µg/dl as a level of concern for children (WHO, 1995; ASTDR, 2007b). To fill the immediate need for a scientifically sound method to assess adult lead risks, USEPA developed the Adult Lead Model (ALM), a simple representation of lead biokinetics to predict quasi-steady state BLL among women of child bearing age with site exposure to contaminated soil in a non-residential setting. However, the model can also be used as an interim modelling methodology until more sophisticated methodology is available (USEPA, 2003).

The basic form of the Adult Lead Model is given by Equation 9:

PbB

PbB

(Equation 9)

where: PbBcentral

= central estimate of BLL in adults (µg/dl) who are exposed to soil/dust Pb concentration, PbS 47

PbB0

= Typical BLL in adults in (µg/dl) in the absence of exposures to the site being assessed

PbS

= Soil/dust lead concentration (µg/g)

BKSF

= Biokinetic slope factor relating quasi-steady state increase in PbB0 to average daily Pb uptake

IRS

= Intake rate of soil (g/day)

AFS

= Absolute gastrointestinal absorption fraction for ingested lead (unitless)

EFS

= Exposure frequency for contact (days/yr)

AT

= Averaging time (days)

3.Results and Discussion 3.1 Contaminant concentrations in suspended air particulates Trace metal concentrations detected in suspended air particulates are presented in

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Table

Location Office (n=3)

Mean Median Min. Max. Repair Mean (n=5) Median Min. Max. Dismantling Mean (n=7) Median Min. Max. Storage Mean (n=2) Median Min. Max. Cable Shredding Mean (n=1) Median Min. Max. Chemical Waste Mean (n=1) Median Min. Max. Control Mean (n=4) Median Min. Max. OSHA PEL-TWAa NIOSH REL-TWAa HK OELb

3. The informal e-waste recycling workshop did not allow for an air sample

Cd 5.39±2.41ab 4.58 2.31 10.18 3.80±1.42b 3.71 2.35 6.98 38.6±48.3a 9.91 1.59 204 3.72±1.73b 3.79 1.68 5.63 4.58ab 3.57b 4.38±4.23b 4.22 0.04 12.34 5000 n.a. 10 000*

Cr 129±126ab 96.8 2.96 363 279±413ab 41.7 0.93 1450 593±919ab 148 2.5 2714 431±461a 226 157 1116 2.25c 1.37c 15.4±8.34bc 14.5 6.48 26.2 1 000 000 500 000 500 000

Cu 44.6±13.5c 45.4 23.0 63.0 54.0±27.4bc 42.8 26.0 124 142±143b 94.2 23.15 644 50.5±33.0bc 37.2 28.11 99.7 429a 82.6bc 103±54.9bc 114 24.5 163 1 000 000 1 000 000 1 000 000

Pb 115±66.4bc 94.7 10.9 211.4 131±93.8bc 99.4 1.74 296 824±801a 741 67.8 3415 36.0±19.3cd 35.8 15.7 56.9 239ab 289ab 86.8±116d 5.9 0.21 252 50 000 50 000 50 000

Ni 108±97.7b 72 18.8 349.6 220±436ab 77.7 29.8 1950 485±592a 227 46.4 2717 61.4±35.9b 53.1 29.9 109.4 191ab 88.9b 87.4±67.2b 68.4 24.3 218 1 000 000 15 000 1 500 000

to be taken and therefore results presented in this section are those of the formal e-waste recycling workshops only. The workshop in which desoldering processes were conducted also did not allow air samples to be taken in the desoldering area, in addition safety concerns restricted sampling in loading areas therefore, no results could be obtained for desoldering and loading processes. Probably because of the small sample size and the heterogeneity of air particulates in different workshops, the concentrations of investigated metals all follow a non-normal distribution. Hence, in 47

Zn 401±590e 84.1 28.6 1892 458±556de 169 32.9 2130 4456±5207bc 1698 39 18806 38.0±1.15e 37.6 37 39.6 8002a 6872ab 1220±637cd 1151 493 2042 n.a. n.a. n.a.

addition to the mean, the median and range are also reported. In general, air particulates in the dismantling area contained the highest concentrations of Cd (1.59 – 204 ng/m3), Cr (2.5 – 2714 ng/m3), Pb (67.8 – 3415 ng/m3) and Ni (46.4 – 2717 ng/m3) while levels of Cu and Zn were highest in the cable shredding area (429 and 8002 ng/m3 respectively). At all workshops, dismantling was done manually using hand held tools which generate large amounts of dust and may explain why high concentrations of metals were detected in air particulates. Pb and Ni concentrations were also calculated to be significantly different than the control site. In addition, Cu concentrations in the cable shredding area were significantly different than those detected in other areas of the workshop while only Zn concentrations were significantly different from most workshop areas except chemical waste treatment areas. As wires and cables are known to contain large amounts of Cu and Zn, it can be expected that significant portions will be emitted during cable shredding processes.

All standards pertaining to air particulates mentioned in Section 1.3 are based on an 8-h time weighted average (TWA) with exposure on a 40 h/week schedule (OSHA, 2006). They are therefore not directly comparable to the results obtained in this study, where sampling time spanned over 24 h. Instead, they are provided as a reference in

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Table . Since HK’s OEL are identical to that of ACGIH’s TLV, only HK’s OEL are

Location Office (n=3)


Cd 5.39±2.41ab 4.58 2.31 10.18 3.80±1.42b 3.71 2.35 6.98 38.6±48.3a 9.91 1.59 204 3.72±1.73b 3.79 1.68 5.63 4.58ab 3.57b 4.38±4.23b 4.22 0.04 12.34 5000 n.a. 10 000*

Cr 129±126ab 96.8 2.96 363 279±413ab 41.7 0.93 1450 593±919ab 148 2.5 2714 431±461a 226 157 1116 2.25c 1.37c 15.4±8.34bc 14.5 6.48 26.2 1 000 000 500 000 500 000

Cu 44.6±13.5c 45.4 23.0 63.0 54.0±27.4bc 42.8 26.0 124 142±143b 94.2 23.15 644 50.5±33.0bc 37.2 28.11 99.7 429a 82.6bc 103±54.9bc 114 24.5 163 1 000 000 1 000 000 1 000 000

Pb 115±66.4bc 94.7 10.9 211.4 131±93.8bc 99.4 1.74 296 824±801a 741 67.8 3415 36.0±19.3cd 35.8 15.7 56.9 239ab 289ab 86.8±116d 5.9 0.21 252 50 000 50 000 50 000

Ni 108±97.7b 72 18.8 349.6 220±436ab 77.7 29.8 1950 485±592a 227 46.4 2717 61.4±35.9b 53.1 29.9 109.4 191ab 88.9b 87.4±67.2b 68.4 24.3 218 1 000 000 15 000 1 500 000

presented. Results indicated that concentrations of Cd, Cr, Cu, Pb and Ni detected in suspended air particulates collected from all workshops are at a level where occupational exposures resulting in adverse health effects are minimal. With regards to Zn, which concentrations were highest out of all metals tested, no international standards could be identified. However, OSHA recognizes it as an irritant to the eyes, nose, throat, and skin. It can also potentially cause acute lung damage (OSHA, 1993).

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Although the particle size in the present study was different from the study of Deng et al. (2006), it was found that Cd, Pb and Zn concentrations from dismantling areas were 5, 2 and 4 times higher than TSP (particles less than 30 – 60 µm) concentrations in Guiyu. Ni concentrations from the present study all exceeded those measured in Deng et al. (2006) while Cr and Cu concentrations were all below concentrations measured in the same report. In another study done by Kent et al. (2007) on airborne metal exposures in a formal cellular phone recycling plant in the United States, 8-h personal air samples were collected and analyzed for Al, As, Be, Ca, Cd, Cr, Cu, Fe, Pb, Mg, Mn, Ni, Se, Ag, Na, and Zn. With the exception of Cr which results were comparable, those obtained from personal sampling were 1.7 to 1338 folds higher than corresponding concentrations detected in the present study. In their study, Cu from shredding and roasting steps reached 22 000 ng/m3 and 38 000 ng/m3 respectively. Although Kent et al. (2007) did not conduct area samples and the type of waste and treatment capacity will have an effect on concentrations of metals on suspended particulates, the large discrepancies between personal and area sampling advocates the need to conduct personal sampling on local e-waste workers in the future. [insert Table 3 here]

3.2 Surface dust Results from wipe samples are presented in Table . Large variation was seen between samples of the same area reflecting on the heterogeneity of the samples implying that workers conducting the same processes may be exposed to varied levels of surface 47

contaminants, even when their work benches are located in close proximity to each other. Furthermore, no significant differences could be identified for Cd and Cr concentrations between different areas of the workshop. However, Cu and Ni concentrations in the cable shredding area and Pb in the desoldering areas were significantly different than other parts of the workshop. Significant differences between mean surface contaminant concentrations indicate that the activities of individual work processes present a different level of risk relative to other areas.

Further examination of the results found that workers in the dismantling and desoldering areas are exposed to the highest concentrations of Pb. A sample from the dismantling area of one of the workshops measured 8562 µg/100 cm2, being almost 20 times higher than US regulated limit of 431 µg/100 cm2(USEPA, 2001). Moreover, workers involved with cable shredding are exposed to high amounts of Cu on work surfaces, with the mean concentration being approximately 16 times higher than the control. Regarding trace metal concentrations in surface dust between formal and informal e-waste recycling workshops, trace metal concentrations measured in the storage area of the informal e-waste recycling workshop were generally lower than those measured in the formal e-waste recycling workshops. With the exception of Cd, no significant differences in trace metal concentrations were observed between surface dust in the informal e-waste recycling workshop and the control site. This may be because the informal e-waste recycling workshop only stores e-waste on-site with no other handling or treatment processes and that the site is open and subjected

47

to weather influences such as rain and wind which could potentially reduce the amount of dust within the workshop.

No previous study on trace metal analyses in e-waste recycling workshops using wipe sampling was identified in the literature. But in comparison with a study done by McDonald et al. (2010) to quantify Pb and Cd in Canadian homes where the highest median Pb concentration was 5.64 µg/100cm2 and the highest Cd concentration was 0.320 µg/100cm2, results of Pb and Cd in the surface dust collected from formal e-waste recycling workshops in the present study were found to be between 1.3 – 103 and 1.15 – 11.4 times higher respectively. Results suggest that e-waste recycling contributes significant concentrations of trace metals in surface dust exposed to workers. Wipe sampling is regarded as a fast and simple method determining contaminants present in the surface environment. Dermal contact with hazardous non-volatile chemicals which remain on work surfaces for long periods of time could be a significant exposure pathway. Chemicals such as Pb may be absorbed through the skin to cause adverse health effects, such as causing damage to the brain and kidney, without being noticed by the worker (ASTDR, 2007a & 2007b). In addition to skin absorption, exposure to dust on work surfaces may adhere to the skin and enter the body through inadvertent ingestion. Since all samples were taken on surfaces which are regularly used by workers (e.g. desks and work benches), practice of good housekeeping may significantly reduce the exposure and risk posed to the workers. [insert Table 4 here] 47

3.3 Workshop floor dust Similar to results from air and wipe samples, concentrations of metals in floor dust do not follow a normal distribution and their results are presented in Table . Reference was also made to Li et al. (2001) on their study of trace metal concentrations in road side dust collected on roads around urban parks in Hong Kong. It was found that their results for Cd, Cu, Pb, and Zn were comparable to that of the control site in the current study.

As can be expected, dust swept from office areas of the formal e-waste recycling workshops contained the lowest levels of trace metals in general, while results were varied for other work processes. Surprisingly, loading areas where no e-waste recycling activities take place contained the highest mean levels of Hg and Cd where concentrations were respectively nine and two times higher than the second highest concentration measured. In addition, mean Pb concentrations in the loading area did not differ significantly from Pb concentration in the desoldering area where the highest level of Pb (19 172 mg/kg) was detected. The highest mean Cr concentration was detected in the dismantling area (801mg/kg) and was 8 times higher than the dust collected by Brigden et al. (2005) from Chinese and Indian PCB recycling workshops where PCBs were heated over heated metal plates or open flames so that components can be removed manually. Cr concentration in one of the formal e-waste recycling workshops of the present study averaged to be 2909 mg/kg or approximately 29 times the value measured in the Chinese and Indian workshops in Brigden et al. (2005). 47

Further comparisons with the Bridgen et al. (2005) found lower Cu concentrations compared to that of the Guiyu workshops conducting PCB recycling. Results from the present study indicate that workers are exposed to significant concentrations of trace metals in workshop floor dust of formal e-waste recycling workshops in Hong Kong which alarmingly, were comparable to those detected in workshops where uncontrolled heating and burning of PCBs are practised. When comparing the findings obtained from the informal e-waste recycling workshop, Cd and Zn concentrations in the storage areas were found to be comparable to those obtained in PCB recycling workshops in Guiyu. Trace metal concentrations in the loading area were in general, lower than the concentrations obtained in the formal e-waste recycling workshop which again, may be attributed to the fact that the loading area of the informal e-waste recycling workshops are in the open-air and exposed to various weather conditions. [insert Table 5 here]

3.4 Correlations between trace metals in dust Spearman Rank’s correlation coefficient of trace metals in suspended air particulates, surface dust and floor dust collected from local formal e-waste recycling workshops are summarized in Table 6 – Table 8. The majority of metals investigated were found to be significantly positively correlated with each other in all types of samples tested, which suggests a common origin. No significant correlations were seen between Cd and Cr in all of the samples (p>0.05). [insert Tables 6, 7 and 8 here] 47

3.5 Human health risk assessment There are no guidelines or regulations for trace metals in settled dust. Therefore it is necessary to conduct a risk assessment on the measured trace metal concentrations in floor dust to evaluate whether any potential adverse health effects are posed to e-waste recycling workers. As previously mentioned, floor dust provides information on both short- and long-term exposures in contrast to only short-term exposures for surface wipes. Therefore, health risks posed by ingestion, dermal contact and inhalation were calculated for floor dusts only. Owing to the small sample size of informal e-waste recycling workshops, only the results obtained from the formal workshops will be presented.

For non-cancer effect reported in

47

Table , ingestion of dust particles appears to be the major route of exposure to workshop dust followed by dermal contact. HQ (noncancer) due to inhalation of dust particles are 2 – 3 orders of magnitude lower than the other two exposure pathways, and was therefore a less significant exposure route compared to the other routes of exposure. The highest HI was calculated for cable shredding followed by dismantling with the largest contribution from ingestion of Cu. But since all calculated HIs were below 1, results indicated that there are little adverse non-cancer health risks due to workshop dust. Since there is evidence that trace metals could be retained in the body for long periods of time and cause potentially serious non-cancer adverse effects to humans (Järup, 2003), exposure to contaminated dust should be minimized as much as possible. [insert Table 9 here]

Table

shows the calculated per million human cancer risks at 5th, median and 95th

percentiles. The median cancer risks ranged from 9.71 ×10-6 – 116 × 10-6 (i.e. 9.71 to 116 in 1 000 000) for exposures to dust collected from the repair and chemical waste areas respectively. According to the USEPA, a generally acceptable cancer risk ranges from 1× 10-6 to 1× 10-4(USEPA, 2001). While the median risk for exposures to floor dust in the chemical waste area was slightly above 1× 10-4 at 116 in 1 million, the upper boundary of the generally acceptable range is not a discrete line at 1× 10-4, further evaluation is necessary to assess on the site-specific conditions, including any uncertainties about the nature and extent of contamination and associated risks (USEPA, 2001). Similar to non-cancer risks, ingestion and dermal contact of 30

floordust appears to be the most significant exposure pathway in term of cancer risks to workers. It should however be noted that at the 95th percentile, calculated cancer risks in the dismantling and chemical waste treatments area were both above 1× 10-4 (147 and 121 in a million respectively). Cancer risks above the accepted range describe the probability that an exposed individual will develop cancer as a result of that exposure by the age of 70 and further investigations on human health implications are recommended to evaluate on the risk of trace metal exposures to workers in the workshop. [insert Table 10 here]

The limitations of risk assessment calculation presented in the present study include that non-cancer health risks through all of the exposure pathways were believed to be underestimated owing to the scarcity of data. For the ingestion pathway, Pb and Hg were excluded because no oral RfDs were established. In the case of Pb, adverse health effects occurred at blood Pb levels so low as to be essentially without a threshold. Therefore EPA considered it inappropriate to develop an RfD for inorganic Pb (USEPA, 2011). For exposure via dermal contact, again because of limited information, USEPA recommended the use of ingestion RfDs until more appropriate dose-response factors are available for dermal exposures. Uncertainty exists because factors were derived from oral studies and intended for assessing risks from ingestion (USEPA, 2004). Similarly, no reference concentration (RfCi) for inhalation was available for Cu, Pb and Zn and therefore, no calculation of their respective HQs could be conducted. 31

Similar to the non-cancer risk assessment, cancer risks calculated in this study were also believed to be an underestimation of the actual risk. USEPA typically calculates slope factors for potential carcinogens in classes A, B1, and B2 which represents human carcinogen, probable human carcinogen with limited human data and probable human carcinogen with sufficient evidence in animals and inadequate or no evidence in humans respectively (USEPA, 1989). Out of all the metals investigated, Cr(VI) and Ni are classified as class A whereas Cd is a class B1 and Pb is a class B2 carcinogen. However, only the oral slope factor for Cr(VI) is available and therefore, cancer risks for ingestion and dermal contact calculated in the present study was based on the carcinogenicity of Cr(VI). For exposure via the inhalation pathway, IURs were available for Cd, Ni, and Cr(VI).

3.6 Health risk estimation for Pb The most direct assessment on evaluating human health risks as a result of exposure to Pb is to measure BLL in exposed individuals. However, the research team was unable to solicit the consent from sampled workshops to conduct blood tests to measure BLL in workers. An alternative method to assess on the potential Pb risks to e-waste recycling workers as a result of exposure is to use the USEPA’s Adult Lead Model (ALM). The ALM, allows a prediction of BLL in workers based on Pb concentrations from environmental sources using a log-normal distribution based on a GSD.

32

An exposure frequency of 300 days/yr and an averaging time of 365 days as recommended by USEPA (2003) for assessing continuing long term exposures were inputted into the ALM. BLL of workers in the desoldering and loading areas were calculated to be 39.5 µg/dl and 35.8 µg/dl respectively, well above the limit of 10 µg/dl set by the CDC. BLL of workers in the dismantling areas were estimated to be at 10 µg/dl while BLL of workers in the cable shredding area were calculated to be 7.8 µg/dl. Under OSHA’s Lead Standard (29 CFR 1910.1025; OSHA, 2006), BLLs of above 40 µg/dl requires medical intervention. Menke et al. (2006) identified a direct association between BLL and increased mortality. The risk of cardiovascular, myocardial infarction and stroke mortality was evident at BLLs of 2 µg/dl. BLL as low as 5 – 9 µg/dl were associated with increased risk of death from all causes, cardiovascular disease, and cancer in a study conducted by Schober et al. (2006). Given the association of adverse health effects at low BLLs, and its irreversible bioaccumulative effects, it is essential to minimize worker exposure to Pb contaminated sites to reduce occupational exposures.

It should be mentioned that the model is estimated using a linear biokinetic slope factor which is multiplied by the estimated lead uptake. The lead uptake in turn, is based upon the overall rate of daily ingestion and the estimated AFs. Owing to insufficient research on dust specific parameters, default soil parameters were inputted into the model for the calculations. But settled dust may have a lower dry bulk density than surface soil, volumes of settled dust may weigh less than comparable volumes of surface soils such that the rate of intake may be higher than 33

that for soil (USEPA, 2008). Therefore, current calculated BLL for workers may only represent the lower range of exposure.

4. Conclusion Metals comprise a significant portion of the materials used in EEE. Through collection of suspended air particulates, surface dust and settled floor dust, it was found that Hong Kong e-waste recycling workers are exposed to trace metal concentrations which may be detrimental to their health. Although concentrations in suspended air particulates were well below the regulatory standards set by OSHA and the reference standards by NIOSH and Hong Kong Labour Department [HKLD], dismantling and desoldering processes were found to generate high Pb levels surface dust. Trace metal concentrations from floor dust were also found to be comparable to those from Chinese and Indian recycling workshops where crude recycling processes are practiced. Pb concentrations were estimated to result in BLL that require medical intervention. As results were modelled against assumptions using US data, further investigation on potential health effects such as direct measurement of the body loadings of trace metals in workers is highly recommended.

Acknowledgment The authors would like to thank the participating e-waste recycling workshops and Mr. K.K. Ma for his help with the chemical analyses. This research is supported by a grant from the Public Policy Research Grant (HKBU 2001-PPR-5) and the

34

Marginally-Funded Post-Graduate Fund (on Persistent Toxic Substances) from the Research Grants Council of Hong Kong.

References ASTDR. 2007a. Lead CAS#:7439-92-1 Division of Toxicology and Environmental Medicine Public Health Statement. Available at: http://www.atsdr.cdc.gov/ToxProfiles/tp13-c1-b.pdf. Last Accessed 29 Mar, 2011.

ASTDR. 2007b. Lead CAS#7439-92-1 Division of Toxicology and Environmental Medicine ToxFAQs. Available at: http://www.atsdr.cdc.gov/tfacts13.pdf. Last Accessed 29 Mar, 2011.

Brigden, K., Labunska, I., Santillo, D., and Allsopp, M. 2005. Recycling of electronic wastes in China and India: workplace and environmental contamination. Technical Note: 09/2005 (Section 1) Greenpeace Research Laboratories, Department of Biological Sciences, University of Exeter, Exeter EX4 4PS, UK.

Chung, S., Lau, K., and Zhang, C. 2011. Generation of and control measures for, e-waste in Hong Kong. Waste Management 31, 544 – 554. 35

Deng, W.J., Louie, P.K.K., Liu, W.K., Bi, X.H., Fu, J.M., and Wong, M.H. 2006. Atmospheric levels and cytotoxicity of PAHs and heavy metals in TSP and PM2.5 at an electronic waste recycling site in southeast China. Atmospheric Environment 40, 6945 - 6955.

Environment Bureau. 2010. Safe and sustainable: a new producer responsibility scheme for waste electrical and electronic equipment. Consultation Document. Available at: http://www.epd.gov.hk/epd/weee/en/index.html. Last accessed 1 Jun, 2012. EPD, 2011. A New Producer Responsibility Scheme for Waste Electrical and Electronic Equipment. Legislative Council Panel for Environmental Affairs CB(1) 424/11-12(03).

Fu, J., Zhou, Q., Liu, J., Liu, W., Wang, T., Zhang, Q., and Jiang, G. 2008. High levels of heavy metals in rice (Oryza sativa L.) from a typical E-waste recycling area in southeast China and its potential risk to human health. Chemosphere 71, 1269 – 1275.

Gaidajis, G., Angelakoglou, K., and Aktsoglou, D. 2010. E-waste: Environmental Problems and Current Management. Journal of Engineering Science and Technology Review 3 (1), 193 – 199. 36

Järup, L. 2003. Hazards of heavy metal contamination. British Medical Bulletin 68, 167 – 182.

Kent, M.S., Corbett, M.L. and Glavin, M. 2007. Characterization and Analysis of Airborne Metal Exposures among Workers Recycling Cellular Phones. Proceedings of the 2007 IEEE International Symposium on Electronics and the Environment, Orlando,112-116.

Lau, W. & Chung, S., in press. A Preliminary Study on Occupational Safety and Health Risks of E-waste Recycling Workers in Hong Kong. Int. J. Chem. Environ. Eng. Sys. Leung, A.O.W., Duzgoren-Aydin, N.S., Cheung, K.C., and Wong, M.H. 2008. Heavy Metals Concentrations of Surface Dust from e-Waste Recycling and Its Human Health Implications in Southeast China. Environ. Sci. Technol. 42, 2674 – 2680.

Li, X., Poon, C., and Liu, P.S. 2001. Heavy metal contamination of urban soils and street dusts in Hong Kong. Applied Geochemistry 16, 1361 – 1368

Li, J., Duan, H., and Shi, P. 2011. Heavy metal contamination of surface soil in electronic waste dismantling area: site investigation and source-apportionment

37

analysis. Waste Management and Research. Available online 15 Mar. DOI: 10.1177/0734242X10397580.

Loew, S. 2000. Session Pilot Checklists and Explanatory memorandum for evalulation of the Environmental Soundness of an Importing Facility Management of the Waste Stream: Used personal computers. Second OECD Workshop on Environmentally Sound Management of Wastes Destined for Recovery Operations. Vienna, Austria.

Ma, J., Addink, R., Yun, S., Cheng, J., Wang, W., and Kannan, K. 2009. Polybrominated Dibenzo-p-dioxins/ Dibenzofurans and Polybrominated Diphenyl Ethers in Soil, Vegetation, Workshop-Floor Dust, and Electronic Shredder Residue from an Electronic Waste Recycling Facility and in Soils from a Chemical Industrial Complex in Eastern China. Environmental Science & Technology 43, 7350 – 7356.

Matsuto, T., Jung, C.H., Tanaka, N. 2004. Material and heavy metal balance in a recycling facility for home electrical appliances. Waste Management 24, 425 – 436.

Menke, A., Muntner, P., Batuman, V., Silbergeld, E.K, and Guallar, E. 2006. Blood Lead Below 0.48µmol/L (10µg/dL) and Mortality Among US Adults. Circulation 114, 1388 – 1394.

38

McCluskey, G. 2003. Occupational Exposure Limits. In Greenberg, M., Hamilton, R.J., Phillips, S.D., McCluskey, G.J. (eds). Occupational, Industrial, and Environmental Toxicology. 2nd Ed. Mosby, Inc: Philadelphia.

McDonald, L.T., Rasmussen, P.E., Chénier, and Levesque, C. 2010. Wipe Sampling Methodologies to Assess Exposures to Lead and Cadmium in Urban Canadian Homes. Proceedings of the Annual International Conference on Soils, Sediments, Water and Energy 15, Article 6.

McDonald, L.T., Rasmussen, P.E., Chénier, and Levesque, C. 2011. Extending wipe sampling methodologies to elements other than lead. Journal of Environmental Monitoring 13, 377 – 383.

NIOSH. 2003a. Elements by ICP (Aqua Regia Ashing): Method 7301. NIOSH Manual of Analytical Methods (NMAM), 4th ed. 3rdsuppl., U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health. Available from: http://www.cdc.gov/niosh/nmam/new.html.

NIOSH. 2003b. Elements on Wipes: Method 9102. NIOSH Manual of Analytical Methods (NMAM), 4th ed., 3rd suppl., U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, 39

National Institute for Occupational Safety and Health. Available from: http://www.cdc.gov/niosh/nmam/new.html.

Ogilvie, S.M. 2004. WEEE & Hazardous Waste A report produced for DEFRA. Available at: http://www.defra.gov.uk/environment/waste/producer/electrical/documents/weee-haz waste.pdf. Last Accessed 29 Mar, 2011.

OSHA. 1993. Zinc. Available at: http://www.osha.gov/dts/chemicalsampling/data/CH_276790.html. Last accessed 16 Jun., 2011.

OSHA. 2006. Permissible Exposure Limits (PELs). Available at: http://www.osha.gov/SLTC/pel/. Last accessed 16 Jun, 2011.

Puckett, J., Byster, L., Westervelt, S., Gutierrez, R., Davis, S., Hussain, A., and Dutta M. 2002. Exporting Harm The High-Tech Trashing of Asia.

Schober, S.E., Mirel, L.B., Graubard, B.I., Brody, D.J., Flegal, K.M. 2006. Blood Lead Levels and Death from All Causes, Cardiovascular Disease, and Cancer: Results from the NHANES III Mortality Study. Environmental Health Perspectives 114, 1538 – 1541.

40

Tsin, T. 2006. The development and implementation of occupational exposure limits in Hong Kong. Regulatory Toxicology and Pharmacology 46, 114 – 119.

Tsydenova, O. and Bengtsson, M. 2011. Chemical hazards associated with treatment of waste electrical and electronic equipment. Waste Management 31, 45 – 58.

USEPA. 1989. Risk Assessment Guidance for Superfund Volume I Human Health Evaluation Manual (Part A). Office of Emergency and Remedial Response. Washington D.C.

USEPA. 2001. Identifying Lead Hazards in Residential Properties. Prevention, Pesticides and Toxic Substances (7404). EPA747-F-01-002. Washington, D.C.

USEPA. 2003. Recommendations of the Technical Review Workgroup for Lead for an Approach to Assessing Risks Associated with Adult Exposures to Lead in Soil. EPA-540-R-03-001.Available at: http://www.epa.gov/superfund/health/contaminants/lead/products/adultpb.pdf. Last accessed 22 Jun. 2011.

USEPA. 2004. Risk Assessment Guidance for Superfund Volume I: Human Health Evaluation Manual (Part E, Supplemental Guidance for Dermal Risk Assessment) Final. EPA/540/R/99/005. Washington, D.C.

41

USEPA, 2007. Method 7473: Mercury in solids and solutions by thermal decomposition amalgamation, and atomic absorption spectrophotometry. United States Environmental Protection Agency.

UNEP. 2008. About the Convention. Available at: http://chm.pops.int/Convention/tabid/54/language/en-US/Default.aspx. Last Assessed 6 May, 2011.

USEPA. 1989. Risk Assessment Guidance for Superfund Volume I Human Health Evaluation Manual (Part A). Office of Emergency and Remedial Response. Washington D.C.

USEPA. 1997. Exposure Factors Handbook. National Center for Environmental Assessment, Washington, D.C.

USEPA. 2003. Recommendations of the Technical Review Workgroup for Lead for an Approach to Assessing Risks Associated with Adult Exposures to Lead in Soil. EPA-540-R-03-001.Available at: http://www.epa.gov/superfund/health/contaminants/lead/products/adultpb.pdf. Last accessed 22 Jun. 2011.

42

USEPA. 2009. Risk Assessment Guidance for Superfund (RAGS), Volume I: Human Health Evaluation Manual (Part F, Supplemental Guidance for Inhalation Risk Assessment). OSWER 9285.7-82. Office of Superfund Remediation and Technology Innovation. Washington, D.C.

USEPA. 2011. Lead and compounds (inorganic) (CASRN 7439-92-1). Integrated Risk Information System. Available at: http://www.epa.gov/iris/subst/0277.htm. Last accessed 20 Jun, 2011.

Widmer, R., Oswald-Krapf, H., Sinha-Khetriwal, D., Schnellmann, M., and Böni, H. 2005. Global perspectives on e-waste. Environmental Impact Assessment Review 25, 436 – 458.

Wong, C.S.C., Duzgoren-Aydin, N.S., Aydin, A., and Wong, M.H. 2007. Evidence of excessive releases of metals from primitive e-waste processing in Guiyu China. Environmental Pollution 148, 62 – 72.

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Table 1 Overview of trace metals commonly found in e-waste (Source: Ogilvie, 2004, EMPA, 2009, Li et al., 2011, and, Tsydenova and Bengtsson, 2011)

Substance Arsenic

Occurrence in e-waste Light emitting diodes

Barium

CRT (in electron gun getter)

Beryllium

PCB connectors

Cadmium

Rechargeable batteries (Ni-Cd), CRT (in phosphors), contacts and switches on PCBs, stabilizers in PVC (PVC is ubiquitously used as insulation coating on wires and cables), printer inks and toners

Chromium VI

Data tapes, floppy disks, additives in plastic-like pigments

Copper

Wires, PCBs

Lead

Rechargeable batteries (lead acid batteries – most commonly used in portable devices), CRT (in cone glass), solders on PCBs, wiring

Lithium

Rechargeable batteries (commonly used in portable devices)

Mercury

Relays and switches, batteries, gas discharge lamps (widely used in lighting LCD displays), capacitors, light emitting diodes attached to PCBs, thermostat Rechargeable batteries (Ni-Cd and NiMeH), CRT (electron gun), PCBs CRT (in panel), additives in plastics

Nickel Zinc

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Table 2 Recovery ranges for inspected elementsin the different types of environmental mediums sampled from e-waste recycling workshops in Hong Kong

Element

Floor Dust

Air Filters

Surface Wipes

Cd

89 – 124%

91 – 107%

90 – 109%

Cr

93 – 112%

77 – 103%

90 – 98%

Cu

91 – 114%

90 – 98%

103 – 112%

Pb

87 – 101%

86 – 105%

87 – 104%

Hg

89 – 92%

n.a.

n.a.

Ni

86 – 100%

85 – 102%

81 – 107%

Zn

81 – 96%

92 – 111%

n.a.

n.a. – not applicable

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Table 3 Concentration of trace metals in suspended air particulates (ng/m3) measured from formale-waste recycling workshops in Hong Kong. Location Office (n=3)


Cd 5.39±2.41ab 4.58 2.31 10.18 3.80±1.42b 3.71 2.35 6.98 38.6±48.3a 9.91 1.59 204 3.72±1.73b 3.79 1.68 5.63 4.58ab 3.57b 4.38±4.23b 4.22 0.04 12.34 5000 n.a. 10 000*

Cr 129±126ab 96.8 2.96 363 279±413ab 41.7 0.93 1450 593±919ab 148 2.5 2714 431±461a 226 157 1116 2.25c 1.37c 15.4±8.34bc 14.5 6.48 26.2 1 000 000 500 000 500 000

Cu 44.6±13.5c 45.4 23.0 63.0 54.0±27.4bc 42.8 26.0 124 142±143b 94.2 23.15 644 50.5±33.0bc 37.2 28.11 99.7 429a 82.6bc 103±54.9bc 114 24.5 163 1 000 000 1 000 000 1 000 000

46

Pb 115±66.4bc 94.7 10.9 211.4 131±93.8bc 99.4 1.74 296 824±801a 741 67.8 3415 36.0±19.3cd 35.8 15.7 56.9 239ab 289ab 86.8±116d 5.9 0.21 252 50 000 50 000 50 000

Ni 108±97.7b 72 18.8 349.6 220±436ab 77.7 29.8 1950 485±592a 227 46.4 2717 61.4±35.9b 53.1 29.9 109.4 191ab 88.9b 87.4±67.2b 68.4 24.3 218 1 000 000 15 000 1 500 000


a

OSHA, n.d.; b HKLD, 2002; Key: n.a. – none established; * - inhalable dust fraction; Values followed by the same letter (a - e) in the same column are not significantly different at the 0.05 probability level according to Duncan’s Multiple Range Test

47

Table 4 Trace metal concentrations on surface wipes (µg/100 cm2) of formal and informale-waste recycling workshops in Hong Kong. Location Cd Cr Cu Pb Ni Office Mean 0.637±0.491a 12.8±10.1a 14.9±11.8cd 7.35±6.46bc 79.5±127bcd Median 0.74 8.85 9.86 8.47 9.38 (n=14) Min. 0.03 1.00 2.78 0.41 1.8 Max. 1.31 29.3 35.8 21.5 379 Repair Mean 0.548±0.359a 20.6±21.6a 44.9±148cd 40.5±135bc 132±252abc (n=24) Median 0.385 15.0 11.2 10.7 46.3 Min. 0.04 0.60 2.63 1.75 0.76 Max. 1.28 81.3 735 675 1173 Dismantling Mean 3.65±8.04a 51.9±85.1a 431±1136bc 582±1748ab 93.1±124abc (n=26) Median 1.36 22.0 32.8 24.6 13.3 Min. 0.01 0.34 3.53 2.80 4.12 Max. 41.0 334.5 4816 8562 413 Storage Mean 1.46±0.23a 34.9±6.75a 12.2±0.58cd 12.9±4.24b 7.77±1.76cd (n=6) Median 1.46 30.9 12.2 13.0 7.66 Min. 1.24 7.40 11.4 7.88 6.20 Max. 1.68 44.9 12.8 17.9 9.56 Desoldering Mean 0.485±0.09a 13.5±6.36a 97.7±87.9bc 486±418a 20.8±13.3bcd (n=6) Median 0.515 13.1 58.1 268 17.9 Min. 0.35 4.58 22.5 148 7.55 Max. 0.58 22.6 221 1125 41.2 Mean 0.367±0.035a 29.2±14.6a 1350±1726a 51.4±33.5ab 174±78.2a Cable Shredding Median 0.37 34.5 394 33.6 200 (n=3) Min. 0.33 12.7 315 30.4 86.8 Max. 0.40 40.4 3343 90.0 237 Mean 1.89±2.59a 20.6±7.26a 120±47.2b 38.6±25ab 111±52.0ab Chemical Waste Median 0.76 20.5 103 40.7 102 (n=4) Min. 0.29 14.2 87 11.25 58.5 Max. 5.73 27.4 190 61.9 183 Storagei Mean 0.24±0.01a 7.53±0.18a 4.33±0.85d 5.87±0.37bc 4.30±1.04cd (n=2) Median 0.24 7.53 4.33 5.87 4.30 Min 0.23 7.40 3.73 5.60 3.56 Max 0.25 7.65 4.93 6.13 5.03 Control Mean 0.31±2.14b 26.8±34.9a 84.1±147cd 40.7±56.5c 3.68±3.40d (n=12) Median 0.15 2.62 4.77 2.9 2.78 Min.