Article pubs.acs.org/est
PM10 and PM2.5 and Health Risk Assessment for Heavy Metals in a Typical Factory for Cathode Ray Tube Television Recycling Wenxiong Fang, Yichen Yang, and Zhenming Xu* School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People’s Republic of China ABSTRACT: The representative waste television recycling process was chosen as the object of this study, including manual dismantling and mechanical separation of printed circuit boards (PCBs) and cathode ray tubes (CRTs) in two independent workshops. During these recycling processes, fine particulate matter and heavy metals will be released into the air to impact the environment and the health of the workers. The mass concentrations of PM2.5 (particles below 2.5 μm diameter) in mechanical and dismantling workshops ranged from 252.6 to 290.8 μg/m3 and from 112.7 to 169.4 μg/m3, respectively. The average concentration of PM2.5 around the workshop was 98.5 μg/m3. Meanwhile, the contents of PM10 (particles below 10 μm diameter) were all below the risk threshold, except that (360.4 μg/ m3) monitored in the mechanical workshop. In two workshops, Pb (20.46 and 6.935 mg/g) was the most enriched metal in the PM2.5 samples, while in PM10, the concentration of Cu (27.76 and 31.80 mg/g) was the largest. The concentration of Cd was the least in both PM10 and PM2.5. Health risk assessment showed that the total hazard indexes for non-carcinogenic metal in PM2.5 monitored in mechanical and dismantling workshops and in the southeast of the workshops were 7.61, 3.01, and 1.57, respectively, all above the safety level. Furthermore, Pb (7.28 and 3.01) might possibly have a non-carcinogenic effect on the workers in two workshops, and the sequence of the hazard quotient (HQ) through the three exposure ways was ingestion > dermal contact > inhalation. The lifetime cancer risk of four targeted metals was Cr > Ni > Pb > Cd, which could be proven in all monitoring samples. This study aims to provide a large amount of valid data for the State Environmental Protection Department to develop relevant environmental standards and for companies to improve the waste television recycling system to be more efficiently and environmentally friendly.
1. INTRODUCTION With the development of the electronic industry and information technology, a large amount of waste electric and electronic equipment (WEEE) is worldwide constantly generated, which has become a serious problem for environmental protection and also a risk to human health. It is not only a crisis of quantity1 but also a crisis of toxic parts,2 such as lead, chromium, cadmium, etc. China, as the world’s leading manufacturing country, has become the biggest dumping ground of WEEE.3 According to some other studies,4−6 the number of abandoned television sets was about 56 million sets in 2010, accounting for 81.53% of the electronic waste (ewaste) collected by normal e-waste recycling companies. In addition, because of the lack of advanced recovery technology, serious environmental contaminations have been caused in the process of previous e-waste recovery, such as exposed manual dismantling, open incineration, acid washing, etc.7 On the other hand, valuable materials can be separated from e-waste. For example, precious metals constitute about 30% of the waste printed circuit boards (PCBs) by weight (copper, ∼16%; solder, ∼4%; iron and ferrite, ∼3%; and nickel, ∼2%).8 Therefore, effective technologies should be applied to meet the relevant requirements on comprehensive use of resources, environmental protection, and labor safety. © 2013 American Chemical Society
The recycling of waste televisions, as a main part of WEEE, is becoming an issue of common concern. Presently, the representative television recycling process has been widely used in e-waste recycling factories in China, which includes manual dismantling and mechanical separations of PCBs and cathode ray tubes (CRTs). After efficient disassembling, the power cord, speaker, demagnetized coil, and shell would be separated and recovered as industrial raw materials. PCBs and CRTs could be separated and need special treatment. The crush (pneumatic separation) corona electrostatic separation treatment line is used for recycling valuable components from waste PCBs, and the four-position semi-automatic cutting technology is used for processing of CRT recycling. Various methods were applied to recover metallic lead from the funnel glass, such as the vacuum-aided carbon thermal reduction method9 and the mechanical activation method for extracting lead.10 These physical processes have been proven to be technologically feasible for waste television recycling. However, the negative impacts of the television recycling system are still Received: Revised: Accepted: Published: 12469
June 15, 2013 September 5, 2013 October 1, 2013 October 1, 2013 dx.doi.org/10.1021/es4026613 | Environ. Sci. Technol. 2013, 47, 12469−12476
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Figure 1. Typical waste television recycling workshop and the sampling points.
Figure 2. Typical treatment process for waste television recycling.
not researched clearly. The powder, especially fine particulate matter (PM), will be released into the ambience of each recycling line during these physical processes, which can pass through the alveolus and reach parts of the body by the blood circulatory system, and the quantity of PM2.5 constitutes 96% of all particles deposited in the lung parenchyma.11 Furthermore, heavy metals (Cu, Cr, Cd, Ni, and Pb) with a high concentration will be adhered on the particles, which will cause various health problems to the workers in the workshops and the residents around the factory.12,13 According to previous studies,14,15 the China Environmental Protection Agency (EPA) has listed waste CRT as a kind of hazardous waste for the high-content Pb in the funnel glass (20−30% PbO) and the PCB recycling process will release five metals. In the recent literature, there is no comprehensive research on the waste television recycling process about the contents of PM2.5 and PM10 and health risk assessment for heavy metals. Meanwhile, most researchers focused on the health risk assessment of total suspended particulate (TSP) and PM10 and the lack of systematic studies on heavy metals in PM2.5, which has a greater health risk to workers. Therefore, a series of monitoring data on the representative television recycling process in our study is valuable and significant for the State
Environmental Protection Department to develop relevant environmental standards and for companies to improve the waste television recycling process to be more environmentally friendly. Our major work contents of this study are as follows: (1) to monitor the concentrations of PM10, PM2.5, and heavy metals in and around the two workshops and (2) to estimate the non-carcinogenic effect and lifetime cancer risk of five metals to workers and residents.
2. MATERIALS AND METHODS 2.1. Object of Study. In China, all specialized factories for e-waste recycling need the qualification certificate conferred by the China’s Ministry of Environmental Protection. Their physical process and technology must meet the waste television recycling process requirement in the public announcement of “Waste Electrical and Electronic Products Processing Enterprise Qualification Examination and Licensing Guide”. In our study, the factory is one of the empowerment enterprises and has strong representativeness, which is located in a specific industrial zone in Shanghai, shown as Figure 1. In this factory, the equipment operating time is 8 h per day and the annual work load is 740 000 television sets. The representative television recycling process includes manual dismantling and 12470
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Figure 3. Whole process for waste television recycling.
the mechanical production lines and the manual dismantling lines, respectively, where workers frequently operated the facilities, and the other four points were set in different directions to monitor the impact from the two workshops. Because the bag filter is one of the ways through which fine particles diffused into the air outside, we collected the samples near the vent of the bag filter (not marked in Figure 1) and analyzed the impact by the Gaussian diffusion model. We arranged these sampling points to assess the risk of occupational hygiene from the recycling lines. At each sampling site, we collected three samples and calculated their mean concentrations of PM2.5 and PM10. After the necessary sample pretreatment, all samples were digested according to the United States Environmental Protection Agency (U.S. EPA) method16 and then were detected by the method of inductively coupled plasma−atomic emission spectrometry (ICP−AES, IRIS Advantage 1000, Thermo Electron Corporation, Waltham, MA). For quality control, a blank test was also conducted by the same method. 2.3. Health Risk Assessment of Heavy Metals. Fine particulate matter, especially PM2.5, will cause health risks to workers and residents mainly in three ways: ingestion, inhalation, and dermal contact. This study adopted health risk assessment models from the U.S. EPA to evaluate health risks of heavy metals in the surroundings of the workshops and factory. The average daily dose through ingestion (ADDing), inhalation (ADDinh), and dermal contact (ADDderm) can be calculated as follows:17
mechanical separations of PCBs and CRTs (shown as Figure 2). After efficient disassembling (Figure 3A), the power cord, speaker, demagnetized coil, and shell would be separated from the waste television and recovered as industrial raw materials. PCBs and CRTs could be separated and need special treatment. The technology for PCB recycling consists of four parts (Figure 3B): (1) the multiple scraping parts, including one feed conveyer, one shredder, and two hammer grinders (the shredder is used before hammer grinders to reduce the average size of waste PCBs; after two hammer grinders, the particle size is below 2.5 mm and the size distribution of scraped waste PCBs is continuous), (2) the multiple separators, including two cyclones and one vibrating screen (after the process of cyclone separating, the fine non-metal particles are almost delivered to the cyclone 2 and the crude particles (size of +1.2 mm) and suitable particles (size of +0.6−1.2 mm) are delivered to the vibrating screen; after the vibrating screen, the crude particles are delivered back to the hammer grinder 2 and the suitable particles are fed to the six-roll electrostatic separator), (3) the six-roll corona electrostatic separation (CES) (after six-roll CES, metal and non-metal particles can be recovered), and (4) the dust precipitation part (the bag-type dust collector was used to precipitate the dust from the process of scraping and material delivering). Meanwhile, the treatment for CRT recycling consists of three parts (Figure 3C): (1) removal of the explosion-proof band part, (2) four-position semi-automatic cutting process (the panel and funnel glasses are separated, and the phosphorus and nickel net will be removed), and (3) further treatment for funnel glasses to remove metallic lead (the vacuum-aided carbon thermal reduction method and the mechanical activation method for extracting lead have been used in the lead-removal processes; glass and metal would be recovered during this physical process). 2.2. Sample Collection and Analysis. A middle volume air sampler (flow rate of 0.100 m3/min) was applied to collect PM10 and PM2.5 samples. Four sampling points were set near
ADDing =
C × IngR × EF × ED BW × AT
(1)
ADDinh =
C × InhR × EF × ED BW × AT × PEF
(2)
ADDderm =
C × SA × SL × ABS × EF × ED BW × AT
(3)
where C stands for the concentration of the contaminant in dust (mg/kg). For ingestion, the intake rate (IngR) was 100 12471
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Figure 4. Mean concentrations of PM2.5 and PM10 at different sampling points.
mg/day for adult. For inhalation, InhR was 15.2 m3/day for male. Particle emission factor (PEF) was 1.36 × 109 m3/kg.18 For dermal contact, the exposed skin area (SA) was given as 2253 cm2. The skin adherence factor (SL) equaled 0.2 mg cm−2 day−1, and the dermal absorption factor (ABS) was 0.001.19 The average bodyweight (BW) of Chinese people was 60 kg for adults.20 In this study, exposure frequency (EF) was assumed as 250 days per year and the exposure duration (ED) was assumed as 10 years.21 The average time (AT) was 3650 days. A hazard quotient (HQ) means the non-carcinogenic risks of single contaminant, varying from the hazard index (HI), which represents the total non-carcinogenic risks of different pollutants through the above-mentioned three ways. The formulas for determining the HQ and HI are as follows:17 ADD RfD
(4)
∑ HQ i
(5)
HQ =
HI =
3. RESULTS AND DISCUSSION 3.1. Assessment of PM10 and PM2.5 in the Factory. The mass concentrations of PM10 and PM2.5 were monitored at the nine sampling points from November 2012 to February 2013, shown as Figure 4. For the mechanical workshop, the mean concentrations of PM2.5 and PM10 ranged from 252.6 to 290.8 μg/m3 and from 326.3 to 394.5 μg/m3, respectively, which were much higher than the Air Quality Standard of China (PM2.5 ≤ 75 μg/m3 and PM10 ≤ 250 μg/m3). Meanwhile, they were more than 4 times larger than the concentrations (57.3 and 74.3 μg/m3) in the non-working workshop. For the dismantling workshop, the mean concentration of PM2.5 was 141.1 μg/m3 (above the safety limitation). Oppositely, the PM10 concentrations were all below the risk threshold. They were both also larger than the concentrations in the non-working workshop. It suggested that the content of fine particles diffusing from these physical recycling lines was obvious and the in-depth analysis of health risks on the workers was quite significant. For the air around the workshop, the average concentration of PM2.5 was 98.5 μg/m3, which was higher than that in nonworking workshops (63.4 μg/m3). Meanwhile, there was an obvious concentration difference of PM2.5 in up- and downwind directions (average of 68.8 μg/m3 in upwind and 128.2 μg/m3 in downwind). All of these indicated that the fine particles would diffuse into the ambience from the workshops and may have a health risk on the residents. The concentrations of PM10 around the workshop were all below the Chinese grade III guideline. The ratio of PM2.5 to PM10 mass concentration in this study ranged from 0.66 to 0.80, with an average of 0.76, which means particles below 2.5 μm diameter contributed to 76% of the particles below 10 μm diameter. It indicates that fine particles were dominated by PM2.5 and might pose health risks to the workers. Another way through which the fine particles diffuse into the ambience of the workshop is the bag filter. The bag filters had a good filtering effect on coarse particles, but it was difficult for them to filter the particles below 2.5 μm diameter. This was consistent with the monitoring results that the average concentration of PM2.5 (130.4 μg/m3) exceeded the risk threshold at the bag filter outlet. Therefore, we used the
The hazard index (HI) is the sum of HQ. If HQ < 1, then noncarcinogenic effects are impossible. If the HQ ≥ 1, an adverse health effect might likely appear. If HQ > 10, then a high chronic risk exists.20 Meanwhile, four carcinogens (Cr, Ni, Cd, and Pb) are investigated, of which the unit risks (URs) are defined by the U.S. EPA Integrated Risk Information System (IRIS). According to the previous study,22 the equation for the individual lifetime cancer risk (Ric) is as follows: R ic =
[C × ED × UR] 70 years
(6)
where the exposure duration (ED) is 90 days/year for a 20 year work period, equating 1800 days for a lifetime exposure to contaminants, and C is the contaminant concentration (μg/ m3). Any cancer risk less than 1 × 10−6 is considered negligible by the U.S. EPA. 12472
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Figure 5. Particle diffusion model.
Figure 6. Concentration distribution of PM2.5 at different distances from the bag filter.
impact on the residents caused by PM2.5 from the bag filter was cut down well by means of the particle sedimentation and atmospheric dispersion and the health risk could be considered negligible. 3.2. Distribution Characteristics of Heavy Metals in PM10 and PM2.5. 3.2.1. Heavy Metal Distribution in Two Workshops. The concentrations of Cr, Ni, Cu, Cd, and Pb in floor dust collected in two workshops are presented in Table 1. It demonstrated that toxic metals were released into the air and
Gaussian diffusion model (Figure 5) to analyze the impact of PM2.5 on the residents near the factory in our study. According to the continuous point source Gaussian formula, the ground axis concentration model could be derived as follows: ρ(x , 0, 0, H ) =
⎛ H2 ⎞ Q exp⎜ − 2 ⎟ πu ̅ σyσz ⎝ 2σz ⎠
(7)
where ρ was the concentration of particles at a certain point (μg/m3). In our study, the PM2.5 concentration in the baghouse outlet (Q) was 93.6 μg/s. The average wind speed was u̅ = 4.5 m/s, and the height (H) was about 10 m. The standard deviations (σy and σz) remained to be determined according to Pascual’s P−G graph. This model was used to analyze the concentration distribution of PM2.5 near the ground, and the results were presented in Figure 6. It can be seen that the maximum concentration was 0.027 μg/m3 at the distance of 153 m from the bag filter outlet, which indicated that the
Table 1. Cr, Ni, Cu, Cd, and Pb Concentrations in Floor Dust Collected in Two Workshops
floor dust in the mechanical workshop floor dust in the dismantling workshop 12473
Cr (mg/g)
Ni (mg/g)
Cu (mg/g)
Cd (mg/g)
Pb (mg/g)
0.174
1.225
0.947
0.092
13.88
0.152
0.318
2.16
0.059
17.83
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floor dust in the workshops. In comparison to Cr, Ni, Cu, and Cd, Pb was released into the ambience of the recycling lines more easily. There was an obvious difference with the monitoring results monitored in a PCB recycling workshop,23 because the CRT recycling process had great impacts on the environment in the mechanical workshop. Table 2 shows the average concentrations of heavy metals (Cr, Ni, Cu, Cd, and Pb) and the ratios of metal concentrations
average of 0.033% of the PM10 mass concentration. The largest concentration was found in the Pb content (0.012%), followed by Cr (0.011%), Ni (0.005%), Cu (0.004%), and Cd (0.001%). On the other hand, the northeast had the highest concentration of heavy metal (4.25 mg/g). The northwest was second, with an average heavy metal content of 4.15 mg/g, the southeast followed, with 2.51 mg/g, and the southwest was last, with a mean heavy metal content of 2.09 mg/g. Figure 7b presented the heavy metal distributions in PM2.5. The heavy metal content accounted for 0.063% of the PM2.5 mass concentration, which was about 0.03% more than that in PM10. Again, Pb comprised most of the heavy metal content with 0.033%, followed by Ni (0.014%). Cr and Cu had the similar contents measuring 0.007%, and the content of Cd (0.002%) was the least among the five metals again. The highest mass concentration of heavy metals was yet again found in the northeast (8.59 mg/g), followed by the contents in the northwest (6.16 mg/g). The southeast and southwest had heavy metal concentrations of 5.30 and 5.13 mg/g, respectively. 3.3. Heavy Metal Risk Assessment. 3.3.1. Risk Assessment for Non-carcinogenic Metals in the Workshop. The hazards of heavy metals on human health are well-known. Considering that most concentrations of PM10 were below the risk threshold and the fine particles were mainly dominated by PM2.5, the health risk assessments of targeted metals in PM2.5 were more significant. The model of health risk assessment of the U.S. EPA was applied to evaluate the HIs of Cr, Ni, Cu, Cd, and Pb in PM2.5 samples, and the values of HQs and HIs for each non-carcinogenic metal in the two workshops were shown in Table 3. For ingestion, the HQs of the heavy metals showed a sequential order as Pb > Cr > Cu > Ni > Cd in the mechanical workshop, while in the dismantling workshop, it was Pb > Cr > Cd > Ni > Cu. The total HQ was 7.28, to which Pb made the maximal contribution (91.62%) in the mechanical workshop, while it was 2.81 in the dismantling workshop, to which the contribution of Pb was 80.43%. For inhalation, the HQs (0.00612 in the mechanical workshop and 0.00452 in the dismantling workshop) were both far below the health risk boundaries. For dermal exposure, the contributions of Cr, Cd, and Pb to the total HQ were 31.89, 5.26, and 62.23% in the mechanical workshop and those of Cr, Cd, and Pb were 10.95, 24.17, and 34.12% in the dismantling workshop, with the total HQ being smaller than 1 (safety level). In short, the values of HQs calculated in circumstances of all three different exposure
Table 2. Mass Concentrations of Cr, Ni, Cu, Cd, and Pb in Two Workshops (mg/g) mechanical workshop Cr Ni Cu Cd Pb
manual dismantling workshop
PM10
PM2.5
PM2.5/PM10
PM10
PM2.5
PM2.5/PM10
0.554 0.472 27.76 0.108 12.34
1.202 0.744 3.753 0.033 20.46
2.17 1.58 0.14 0.31 1.66
0.436 0.459 31.80 0.398 2.043
2.875 1.148 1.205 0.094 6.935
2.182 2.499 0.038 0.104 3.394
in PM2.5 to that in PM10 in mechanical and dismantling workshops. For the mechanical workshop, it was obvious that Pb (20.46 mg/g) was the most enriched metal in PM2.5, followed by Cu (3.753 mg/g), while the mean concentration of Cu (27.76 mg/g) was the largest in PM10. The concentration of Cd (0.108 and 0.033 mg/g) was the least among the five metals in both PM2.5 and PM10. According to the proportions of metal concentrations, PM2.5 had a larger adsorption capacity with Pb than the other four heavy metals. On the contrary, Cu was the easiest to adhere on the particles between 2.5 and 10 μm. It indicated that particles with different sizes had different adsorptive capacities with each heavy metal. For the sampling point in the manual dismantling workshop, the same distribution of heavy metals could be observed that the content of Pb (6.934 mg/g) was the largest in PM2.5 and Cu had an obviously larger concentration in PM10. In both workshops, Pb was the main factor affecting the health of the workers, which was consistent with the high concentration in CRT funnel glass.9 Therefore, how to prevent the release of Pb still remains quite a significant research subject, and more efficient and novel methods should be used in the CRT television recycling process. 3.2.2. Heavy Metal Distribution around the Workshop. Figure 7a showed the heavy metal content of PM10. The distribution of selected heavy metals only accumulated for an
Figure 7. Concentrations of five metals in (a) PM10 and (b) PM2.5 monitored in different directions. 12474
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Table 3. HQs and HIs for Each Non-carcinogenic Metal in PM2.5 Monitored in the Two Workshops mechanical workshop element
HQing
Cr Ni Cu Cd Pb total
4.57 4.24 6.63 3.77 6.67 7.28
× × × ×
HQinh −1
10 10−2 10−2 10−2
5.36 4.60 1.19 3.22 7.42 6.12
× × × × × ×
manual dismantling workshop
HQderm −3
10 10−6 10−5 10−6 10−4 10−3
1.03 7.08 1.61 1.70 2.01 3.23
× × × × × ×
HI −1
10 10−4 10−3 10−2 10−1 10−1
5.56 4.31 6.79 5.47 6.88 7.61
× × × ×
HQing −1
10 10−2 10−2 10−2
Table 4. HQs and HIs for Each Non-carcinogenic Metal in PM2.5 Monitored in the Southeast HQing 3.52 4.81 1.48 4.79 9.71 1.43
× × × × ×
HQinh
10−1 10−2 10−2 10−2 10−1
4.12 5.21 1.64 5.36 1.08 4.24
× × × × × ×
HQderm
10−3 10−6 10−6 10−6 10−4 10−3
7.92 × 8.02 × 2.22 × 2.16 × 2.72 × 0.129
10−2 10−4 10−4 10−2 10−2
HI 4.35 4.89 1.50 6.95 9.99 1.57
× × × × ×
× × × ×
10 10−2 10−2 10−1
4.24 7.11 3.82 1.19 6.79 4.52
× × × × × ×
HQderm −3
10 10−6 10−6 10−5 10−4 10−3
8.15 1.09 5.16 4.81 6.79 1.99
× × × × × ×
HI −2
10 10−3 10−4 10−2 10−2 10−1
4.48 6.66 1.53 1.55 2.33 3.01
× × × ×
10−1 10−2 10−2 10−1
Ni > Cu. The total HI was 1.57, indicating that adverse health effects might be possible. 3.3.3. Carcinogenic Metal Risk Assessment. The URs for the two known carcinogens (Cr and Ni) and two probable human carcinogens (Cd and Pb) were defined in a previous study22 and presented in Table 5. According to the mean concentrations of each carcinogenic metal in PM2.5 collected in different sampling points, we could calculate the lifetime cancer risk. From Table 5, it can be seen that the trend was the risks in the mechanical workshop > the risks in the manual dismantling workshop > the risks in the southeast. Any cancer risk less than the threshold value (10−6) is considered negligible by the U.S. EPA. From the results, we could see that the lifetime cancer risk of Cr exceeded the threshold obviously and it may have a cancer risk on the workers and residents. 3.4. Management Strategy. Considering the health risk of fine particles and heavy metals, many suggestions to guarantee the health of workers have been put forward and may be carried out in the future. (1) According to a previous study of the assessment results in a PCB recycling workshop,23 the concentration of PM10 was obviously lower than the monitoring results in the workshop, including PCB and CRT recycling lines in our study. Therefore, we suggest that each recycling line should be set up in a separate workshop to cut down the concentrations of particles and heavy metals. (2) If each physical part of the automatic line (e.g., shredder, grinder, and separator) could be isolated by the acoustic hoods, the diffusion of fine particles into the ambience can be obviously reduced, so that the concentrations of particles can be controlled in a low level. Meanwhile, it is very necessary to enhance the interior air purification by the bag-house. (3) The probe monitoring and automation control technology can be used in the waste television recycling lines. This remote control technology can reduce the exposure time of the workers in the ambience of the automatic line and will cut down the health risk of fine particles. (4) Special and effective masks have the most direct protection on the workers, which can filter the most PM2.5. (5) More advanced filter materials should be applied to the dust-removal equipment to reach a significant filtration efficiency of fine particles (below 2.5 μm diameter). Therefore, the concentrations of PM2.5 in bag-house outlet will be in the safety level.
ways showed the following pattern: ingestion > dermal contact > inhalation. On the other hand, according to Table 3, the HIs of Cr, Ni, Cu, Cd, and Pb were 0.556, 0.043, 0.068, 0.055, and 6.88 in the mechanical workshop and 0.448, 0.0067, 0.015, 0.155, and 2.33 in the dismantling workshop, respectively, which indicated that, in both workshops, only Pb might create non-carcinogenic risks to the workers and residents. The reason might lie in the fact that Pb had a high concentration in the particles and could be released into the air more easily during the television recycling process. Also, it can be seen that the total HI (7.61 and 3.01) of five metals exceeded the safety level. In summary, Pb was the main contaminant among the five heavy metals possibly causing human health risks. 3.3.2. Risk Assessment for Non-carcinogenic Metals in the Southeast. According to the monitoring result that PM2.5 was the major contamination among all particles in the southeast, the health risks of each targeted metal in PM2.5 needs to be further investigated. Table 4 shows the HQs of different
Cr Ni Cu Cd Pb total
3.61 6.55 1.48 1.07 2.26 2.81
HQinh −1
10−1 10−2 10−2 10−2 10−1
exposure ways and the HIs of five metals. For ingestion, the HQ was 1.43 and Pb (contributing 67.9%) had the largest threat. For inhalation, Cr had the highest contribution to HQinh (97.12%) and the total HQ was 4.24 × 10−3. For dermal contact, the trend of HQ was Cr > Pb > Cd > Ni > Cu and the total HQ was 0.129, below the risk limitation. Therefore, the sequence of HQ through the three exposure ways was ingestion > dermal contact > inhalation, in accordance with the trend in the mechanical workshop. For each heavy metal, the HIs were all in the safety range and ranked in the order: Pb > Cr > Cd > Table 5. Lifetime Cancer Risk for Each Carcinogenic Metal mechanical workshop pollutant Cr Ni Cd Pb
UR 0.0018 0.012 0.000012 0.00048
C (μg/m3) 0.408 0.279 0.012 6.64
dismantling workshop C (μg/m3)
Ric 3.45 9.43 1.52 5.61
× × × ×
−4
10 10−6 10−6 10−6
0.161 0.194 0.016 1.175 12475
southeast C (μg/m3)
Ric 1.36 6.56 2.03 9.93
× × × ×
−4
10 10−6 10−6 10−7
0.120 0.109 0.005 0.387
Ric 1.01 3.68 3.34 3.27
× × × ×
10−4 10−6 10−7 10−7
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Environmental Science & Technology
Article
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In summary, the concentrations of PM2.5 (average of 276.8 μg/m3 in the mechanical workshop, 141.1 μg/m3 in the dismantling workshop, and 98.5 μg/m3 around the workshops) collected in all sampling points were much higher than the Air Quality Standard of China. Meanwhile, the contents of PM10 were all below the risk threshold, except that (360.4 μg/m3) monitored in the mechanical workshop. The fine particles would diffuse into the ambience of the workshops through the bag filter and other open ways to impact workers and residents. Therefore, special masks for filtering PM2.5 are needed to reduce oral inhalation of fine particles. For the health risk assessment, Pb was the main targeted metal to cause the noncarcinogenic risks probably. The technologies to remove the lead during the CRT recycling process seems to be more efficient and significant to cut down the non-carcinogenic risks. Meanwhile, Cr had high lifetime cancer risk on workers in all samples; therefore, the methods to cut down the concentration of Cr must be taken seriously in further studies.
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AUTHOR INFORMATION
Corresponding Author
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[email protected]. cn. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (21077071) and the National High Technology Research and Development Program of China (863 program 2012AA063206).
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dx.doi.org/10.1021/es4026613 | Environ. Sci. Technol. 2013, 47, 12469−12476
