Article pubs.acs.org/est
Risks in the Physical Recovery System of Waste Refrigerator Cabinets and the Controlling Measure Jujun Ruan,†,‡ Mianqiang Xue,† and Zhenming Xu*,† †
School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People’s Republic of China ‡ School of Environmental Science and Engineering, Yangzhou University, 196 West Huayang Road, Yangzhou, Jiangsu 225000, People’s Republic of China S Supporting Information *
ABSTRACT: Environmental information in physical recovery system of waste refrigerator cabinets was provided in this paper. The system included closed shearing, activated carbon adsorption (ACA), air current separation, magnetic separation, and eddy current separation. Exposures of CFC-11, heavy metals, and noise emitted from the system were assessed. Abundant CFC-11 (>510 mg/m3) was detected in crusher cavity. However, due to the employment of ACA, little CFC11 ( 10, it suggested high chronic risk.26 The hazard index (HI) was the sum of HQ. 2.3. Noise Monitoring. An integrating sound level meter (AWA 5610B) and an octave filter (AWA 5722) was employed to monitor noise levels of the physical recovery system in its running state. Monitoring positions were located near crusher, MS, ECS, ACS, and ACA devices as well as at the boundary of the workshop (presented in Figure 1). The sound level meter and octave filter were placed 1.2 m above the ground and 1 m away from the machines. Three values of noise level were recorded in different positions.
Where Ms is the weight of the filter paper after sampling (mg), M is the weight of the filter paper before sampling (mg), V is the volume of gas flow (m3). Three samples of TSP and PM10 were collected respectively. Sample of ground dust was collected from the ground of workshop by a small broom. 2.2.2. Concentrations Analysis of Heavy Metals. The samples (TSP and PM10 together with filters, ground dust: 0.50 g respectively) were soaked by HNO3 (5 mL, 69%), HCl (15 mL, 36%), and H2O2 (2 mL, 30%) for 12 h. Then the mixtures were heated progressively to 190 °C to near 6 mL. After it was cooled, the solution was filtered into 100 mL volumetric flasks. Finally, concentrations of heavy metals were detected by the method of inductively coupled plasma mass spectrometry (ICPMS, Nexion 300, PerkinElmer).24 Meanwhile, a blank test was conducted with the same method. 2.2.3. Health Risk Assessment of Heavy Metals Exposed in Air. For evaluating the risk of heavy metal exposed in the air of the workshop, risk assessment models from EPA (US) were employed.25 Worker exposes to dust through three pathways: ingestion, inhalation, and dermal contact. The average daily dose contacted through ingestion (ADDing) and inhalation (ADDinh) are expressed as26 ADDing =
ADD RfD
3. RESULTS AND DISCUSSION 3.1. Assessment of CFC-11 Exposure. Monitoring results of CFC-11 concentrations emitted from the physical recovery system were presented in Figure 2. High concentration (>510 mg/m3) of CFC-11 was detected in the crusher cavity. It meant that abundant CFC-11 was stored in waste refrigerator cabinet. Environmental destroy induced by CFC-11 might be brought
C ing × IngR × ED BW × AT
(2)
C inh × InhR × ED BW × AT
(3)
Average daily dose absorbed through skin (ADDderml) is computed by ADDdermal =
Cdermal × SA × SL × ABS × ED BW × AT
(4)
Cing is the concentration of the pollutant absorbed by inhalation and Cdermal is the concentration of the pollutant absorbed through skin. Cing and Cdermal are expressed as C ing = Cdermal = C m(TSP) × C(TSP)
(5)
m
Where C (TSP) is the metal concentration in the TSP sample, C(TSP) is the concentrations of TSP. Cinh is expressed as C inh = C m(PM10) × C(PM10)
(6)
Cm(PM10)
Where is the metal concentration in the PM10 sample, C(PM10) is the concentrations of PM10. For ingestion, the intake rate (IngR) of dust is 100 mg/day for adult. For inhalation, the intake rate (InhR) for male is15.2 m3/day. For dermal contact, the exposed skin area, SA = 1150 cm2; the skin adherence factor, SL = 0.2 mg/cm2day; the dermal absorption factor, ABS = 0.001.27 The average body weight (BW) of Chinese people is 60 kg for adults.28 The exposure duration (ED) is the length of time that contaminant contact lasted and it was calculated by working days (250 days per year) timed the service life (10 years) of the recovery line. The average time (AT) is 3650 days. A hazard quotient (HQ) for health risk was calculated to make
Figure 2. Monitoring results of CFC-11 concentrations emitted from the physical recovery system. 13388
dx.doi.org/10.1021/es303388z | Environ. Sci. Technol. 2012, 46, 13386−13392
Environmental Science & Technology
5.60 × 10 8.08 × 10−3 1.20 × 10 5.25 × 10−4 4.02 × 10 3.52 × 10−3 4.00 × 10 3.50 × 10−3 6.72 × 10 4.24 × 10−6 3.00 × 10 1.35 × 10−4 2.92 × 10 2.21 × 10−3 Cu Pb
HQing RfDderm
7.30 × 10 6.31 × 10−1
7.50 × 10 3.84 × 10−2
HI HQderm
−3
HQinh 13389
−2
−2
Copper had the highest concentrations both in TSP and PM10 samples. Tin had the lowest concentrations. Tin is often considered as harmfulless to human or environment, but copper and lead are toxic materials. Copper and lead can bring heavy destroy to human liver, gallbladder, and brain cell. Exposure risks of copper and lead in TSP and PM10 samples were assessed by the model of health risk assessment of EPA (U.S.). The assessment results were given in Table 2. Hazard quotients of copper and lead dosed by ingestion, inhalation, and dermal absorption were (0.073, 0.0075, and 0.00056) and (0.631, 0.0384, and 0.00808). All the values were smaller than 1 (safety level) and the value of hazard index (0.00811) and (0.678) was also smaller than 1. It showed the concentrations of copper and lead in airborne particulate of workshop were safe for workers. Assessment results indicated exposures of heavy metals in the physical recovery process of waste refrigerator cabinet were safe to human and environment. It was an exemplification of proving physical technology could bring little risk of heavy metal exposure in the recovery process of e-waste. Additionally, pollutants in PM2.5 (particulate matter smaller than 2.5 μm) can bring heavy harm to human health. However, heavy metals exposed in PM2.5 were not investigated in this paper. The reasons were (1) PM2.5 was mainly contributed by coal-fired power generation, traffic emission, and other residuals of burning.30 The particle size created by mechanical crushing had not reached the small degree of PM2.5. (2) PM2.5 was a new air quality index in China. The whole assessment system of PM2.5 had not been mature. Yet, assessment of pollutants in
−2
0
RfD inh
PM10
0.59
−2
TSP
1.3
RfD ing
PM10
3.17
−6
TSP
2.1
ADDderm
PM10
4.91
−4
TSP
ADDinh
monitoring position inside the workshop
−3
Sn (μg/m3)
ADDing
Pb (μg/m3)
elements
Table 2. Average Daily Doses (mg kg−1 day−1) and Hazard Quotients of Copper and Lead Exposed in Air for Worker
Table 1. Average Concentrations of Cu, Pb, Sn in TSP, PM10, and Ground Dust Samples Cu (μg/m3)
−4
out if this ozone depleting substance leaked out. In order to protect ozonosphere, ozone depleting substances had been prohibited to use in human production (especially in refrigerator manufacture) in almost every country. However, the monitoring result suggested that protecting ozonosphere not only depended on prohibiting ozone-depleting substances in new production but also needed to regard the fraction in old production. For collecting the CFC-11 presented in waste refrigerator cabinet, the crusher was designed to enclosed type. Meanwhile, ACA device, which connected to crusher by closed piper, pumped CFC-11 gas into activated carbon fiber. CFC-11 gas was condensed and adsorbed in activate carbon fiber. The monitoring results of CFC-11 concentrations (
