Environ Sci Pollut Res DOI 10.1007/s11356-014-3562-8
RESEARCH ARTICLE
Bioaccessibility and health risk of heavy metals in ash from the incineration of different e-waste residues Xiao-Qing Tao & Dong-Sheng Shen & Jia-Li Shentu & Yu-Yang Long & Yi-Jian Feng & Chen-Chao Shen
Received: 15 June 2014 / Accepted: 3 September 2014 # Springer-Verlag Berlin Heidelberg 2014
Abstract Ash from incinerated e-waste dismantling residues (EDR) may cause significant health risks to people through ingestion, inhalation, and dermal contact exposure pathways. Ashes of four classified e-waste types generated by an incineration plant in Zhejiang, China were collected. Total contents and the bioaccessibilities of Cd, Cu, Ni, Pb, and Zn in ashes were measured to provide crucial information to evaluate the health risks for incinerator workers and children living in vicinity. Compared to raw e-waste in mixture, ash was metal-enriched by category incinerated. However, the physiologically based extraction test (PBET) indicates the bioaccessibilities of Ni, Pb, and Zn were less than 50 %. Obviously, bioaccessibilities need to be considered in noncancer risk estimate. Total and PBET-extractable contents of metal, except for Pb, were significantly correlated with the pH of the ash. Noncancer risks of ash from different incinerator parts decreased in the order bag filter ash (BFA)>cyclone separator ash (CFA)>bottom ash (BA). The hazard quotient for exposure to ash were decreased as ingestion>dermal contact>inhalation. Pb in ingested ash dominated (>80 %) noncancer risks, and children had high chronic risks from Pb (hazard index >10). Carcinogenic risks from exposure to ash were under the acceptable level (Ni. The largest bioaccessible fractions of Cu (79 %) and Ni (58.1 %) were found in BA, whereas the largest bioaccessible fraction of Zn (55.8 %)
was found in BFA and the largest bioaccessible fractions of Cd (88 %) and Pb (75.1 %) were found in CFA. The bioaccessible fractions of the heavy metals in the BA, CFA, and BFA varied widely among the four tests. Comparing the bioaccessibility (Fig. 2) with the total concentration (Fig. 1) of each metal, Pb had the highest total concentration (30,100 mg.kg−1) but the lowest bioaccessible fraction (28.2 %), and Cd had the lowest total concentration
Environ Sci Pollut Res
Sig.
Cd Cu Zn Ni Pb
CGP =96.9+0.55Ctotal −14pH CIP =142+0.36Ctotal −20.5pH CGP =−212+0.53Ctotal −9.79pH
0.966 0.957 0.986
0.000 0.000 0.000
CIP =−153+0.3Ctotal +11.7pH CGP =416+0.29Ctotal +54.1pH CIP =2790+0.29Ctotal −620pH CGP =−46.4+0.39Ctotal +2.84pH CIP =10.7+0.21Ctotal −1.88pH CGP =8050+0.24Ctotal-709pH CIP =2300+0.063Ctotal −299pH
0.977 0.837 0.710 0.930 0.936 0.614 0.564
0.000 0.004 0.042 0.000 0.000 0.119 0.178
GP and IP were two simulated stages of physiologically based extraction test (PBET) GP gastric phase, IP intestinal phase
50
30
9
Ingestion 20
5.6 4.2 2.8 1.4 0.0
10 0
165 3
110 55
2
Dermal contect 1.8
1
1.2 0.6 0.0
0
300
4
200 3
100 Inhalation 20 15 10 5 0
Total Hazard Quotient
18
Total Hazard Quotient
Hazard Quotient -2
40
27
-3
R
BFA
Total Hazard Quotient (10 )
Regression equations
CFA
36
-5
Element
BA
45
Hazard Quotient (10 )
Table 2 Multiple regression analysis of the PBET-extractable metal concentrations and total metal concentrations in the ash samples and the pH values of the ash samples
2010; Hu et al. 2011; Jin et al. 2013; Lu et al. 2011), in which pH having been found to be the most common and significant factor. The pH values of the ash samples are shown in Table S1. The relationship between the bioaccessible concentration of each metal (in the GP and IP), the total concentration of the metal, and the pH of the ash were examined using multiple regression analysis (Table 2) to determine the effect of the pH on the bioaccessibility of the heavy metals in the EDR ash. The bioaccessibilities of the heavy metals in the ash samples were significantly correlated with the pH of the ash at relatively low total metal concentrations (R>0.710, PBA. The risk posed by Cd in BFA was more than twice the risk posed by Cd in CFA, and the risk posed by Pb in CFA was almost twice the risk posed by Pb in BA. These results indicate that the risks of noncancer toxicity may increase as the ash particle size decreases, which agrees with the results of other studies, in which health risks have been found to increase as the particle size decreases (Jin et al. 2013). The risk of noncancer Pb toxicity from ingesting ash from all four tests contributed 83.4 to 92.7 % of the noncancer toxicity risk posed by all five heavy metals. Cd and Pb in BFA from all four tests and Pb in BA from the first test were found to pose risks of adverse health effects through the dermal contact exposure pathway. The total heavy metal concentrations in ash from all four tests were found to pose the risk of noncancer toxic effects through dermal contact. Compared with the risks associated with exposure through ingestion and dermal contact, inhalation was found to be unlikely to pose risks of adverse health
-5
Risk assessment
effects, the HQs for exposure through inhalation being below 0.005 for the total metal concentrations in the ash samples from all four tests. The HQs for exposure to ash through different exposure pathways for all five heavy metals decreased in the order ingestion>dermal contact>inhalation. Therefore, different exposure pathways presented different levels of risk of noncancer toxicity for each heavy metal. The HI values (Fig. 4) for the exposure of children to heavy metals through the three exposure pathways showed that the ash from all four tests would pose high levels of chronic risk. The highest level of noncancer risk to children (HI=52) was found to be posed by BFA from the fourth test, in which Pb exposure through all three exposure pathways contributed 81.3 % of this HI. The risk posed to children by Pb exposure through the ingestion of ash would, therefore, be of grave concern. However, the alarming HQPb that was found for children in this study was much lower than the HQPb values in an e-waste recycling workshop (HQPb =402) and in a near street of such workshop (HQPb =82.6) to children (Leung et al. 2008). It has been found by a number of surveys that children
Hazard Quotient (10 )
A risk assessment was conducted to determine whether the less bioaccessible heavy metals could pose risks to a population working in and living near an EDR incinerator and to investigate the impact factors and to what degree they influence the values of health risk. That would be described in the next section.
Ash from four types of e-waste incinerated
Fig. 4 Characterization of noncarcinogenic risks (hazard quotient) to workers from heavy metals in the four types of e-waste incinerated ash. BA bottom ash, CFA cyclone separator ash, BFA bag filter ash. 1, 2, 3, and 4 stand for the ash samples from four types of raw e-waste incinerated. Total hazard quotient is the sum of each heavy metal’s hazard quotient. Total=Cu+Zn+Ni+Cd+Pb
Environ Sci Pollut Res
BA
125
CFA
BFA
Childern 100 75
that to children, but the hazard values to workers were lower than those to children. The relatively high risk values for the children might be partly attributed to the higher ash ingestion rate (200 mg day−1) that was used for the children than for the workers to estimate the risks posed, the smaller body sizes of children than of workers, and the lack of protective measures that children would take. It has been suggested that children are the most sensitive to risks from pollutants in ash because of more outdoor-playing time, hand-to-mouth activities (mouthing and chewing), deliberately eating the contaminated food, pica behavior as well as less-developed immune systems and higher rates of pollutant absorption (Moya et al. 2004; Meza-Figueroa et al. 2007; Zheng et al. 2010b; Guney et al. 2010). Children sometimes accompany their parents to the workplace and are often exposed to the contaminated environment without any protective measures, which caused they easily be exposed to ash containing heavy metals (Leung et al. 2008). Ruby et al. (1996) found that using total heavy metal concentrations to assess potential risks from ingestion caused the risks of health effects being overestimated. We compared the HQ for ingestion (calculated from the total metal concentrations) with the HQ′ for ingestion (calculated from the bioaccessible fractions of the metals) and also found that HQ for ingestion almost always overestimated the health risk to people from the ingestion of ash. Figures 3 and 4 show that excluding the bioaccessibility of the metals in the ash would result in the risks of noncancer effects being overestimated by a factor of two and, importantly, changed the trend in the risks BA
CFA
BFA
-8
15 25
12
-8
Carcinogenic Risk (10 )
Hazard Index
50
Total Carcinogenic Risk (10 10 )
living near e-waste sites have elevated concentrations of Cd and Pb in their blood (Chen et al. 2011; Huo et al. 2007; Yang et al. 2012; Zheng et al. 2008). Leung et al. (2008) also found that Cu is a pollutant of major concern in e-waste recycling areas. Therefore, urgent attention is required to prevent the health risks of children from them being exposed to Cd, Cu, and Pb in areas where e-waste involving activities are performed. Health risk of ash from EDR incinerated lower than the dust samples of an e-waste recycling workshop and a near street of such workshop mainly caused by the contents of heavy metal in samples from different objects. Different heavy metals content would lead to different degrees of health risk. The risks posed to the health of the workers (Fig. 4) through every exposure pathway to ash from all four tests were almost 10 times lower than the risks posed to children. Only exposure to Pb through the ingestion pathway posed risks of adverse noncancer effects to workers, and the HQ ranged from 1.13 to 3.10 for the ash samples from the four tests. The trend in the HI values (Fig. 5) for workers for the ash samples from the four tests was consistent with the trend that was found for the children. The highest HI value (4.36) was found for BFA from the fourth test. The contributions of each exposure pathway to workers’ noncancer risk were similar to
0 10
Workers
8 6 4 2 0
1
3 2 Considering BA c
4
1
2 3 Omitting BA c
4
Ash from four types of e-waste incinerated Fig. 5 Characterization of noncarcinogenic risks (hazard index) to children and workers in the four types of e-waste incinerated ash. BA bottom ash, CFA cyclone separator ash, BFA bag filter ash. 1, 2, 3, and 4 stand for the ash samples from four types of raw e-waste material incinerated. BAc is bioaccessibility. Hazard index (HI) is the sum of HQ values from each heavy metal and each exposure pathway. HI=(Cu+Zn+Ni+Cd+Pb)ing + (Cu+Zn+Ni+Cd+Pb)inh +(Cu+Zn+Ni+Cd+Pb)der, in which ing is the ingestion, inh is the inhalation, and der is the dermal contact exposure pathway in this study
9 Children
6 3 0 15 12 9
Workers
6 3 0
1
2
3 Cd
4
1
2
3 Ni
4
1
2 3 Total
4
Ash from four types of e-waste incinerated Fig. 6 Characterization of carcinogenic risks to children and workers from heavy metals in the four types of e-waste incinerated ash. BA bottom ash, CFA cyclone separator ash, BFA bag filter ash. 1, 2, 3, and 4 stand for the ash samples from four types of raw e-waste incinerated tests. Only Cd and Ni have cancer risk by inhalation exposed pathway. Total carcinogenic risk is the sum of each heavy metal’s carcinogenic risk. Total=Cd+Ni
Environ Sci Pollut Res
(BA and CFA in Fig. 5). In the same way, if the risk of potential adverse health effects were calculated using total heavy metal concentrations, HQCu for CFA from the third test would pose chronic risk of noncancer effects in children. These might have a considerable impact on management or remediation decisions. The USEPA has found that cancer risks lower than 10−6 are acceptable. Only the cancer risks from exposure to Cd and Ni through the inhalation of ash were assessed in this study (Fig. 6). The cancer risk from different ash samples ranged from 2.92×10−8 to 1.31×10−7 for children and from 3.72× 10−8 to 1.67×10−7 for workers, so exposure to ash from the incineration of EDR was found to pose no cancer risk. The cancer risk and HI (noncancer risk) results showed that workers were more likely to suffer from cancer risks and children were more likely to suffer from noncancer risks. The models that were used in this risk assessment were useful for identifying risks to human health through three exposure pathways to heavy metals in ash from the incineration of four different types of EDR. The noncancer risks and the cancer risks posed by the bottom and fly ash from the different tests (i.e., from the incineration of different types of EDR) varied widely. There are several possible reasons for this variability: the type of EDR being incinerated and the pretreatment method used, the physical and chemical properties of the produced ash, different susceptible populations being exposed, parental involvement in dealing with EDR ash, the effects the daily activities and some special behavior habits of children have on, the different exposure pathways, the difference of parameters for calculating the health risk, and the differences in the heavy metal concentrations in the ash caused by its heterogeneous nature. Given the number and magnitudes of the uncertainties in the exposure factors and toxicity estimates, and the absence of site-specific factors, this study should be considered as preliminary and further research should be undertaken before decisive measures are taken to tackle health risks from ash emitted by EDR incinerators.
Conclusions We found that heavy metals were strongly enriched in ash produced by EDR incinerated in each test, and the metal concentrations in all of the ash samples decreased in the order Pb>Zn>Cu>Ni>Cd. A large proportion of each heavy metal in the ash samples was not bioaccessible, the residual ratio being higher than 50 % for Ni, Pb, and Zn. The bioaccessibility of the heavy metals could be roughly predicted from the properties of the ash when the total metal concentrations were relatively low. Ignoring the bioaccessibility of the heavy metals would lead to the health risks being overestimated. The heavy metals, especially Cd, Cu, and Pb, in the ash produced in all four tests were found to pose risks of noncancer effects,
particularly to children, through three exposure pathways (ingestion, inhalation, and dermal contact). The Pb in ingested ash was found to be the main contributor (>80 %) to noncancer health risks. Many factors would affect the values of health risk posed by exposure to ash, thus further research should be undertaken before any decisive measures are taken to decrease the risks from exposure to ash produced in EDR incinerators.
References Bakoglu M, Karademir A, Ayberk S (2004) An evaluation of the occupational health risks to workers in a hazardous waste incinerator. J Occup Health 46:156–164 Chang CY, Wang CF, Mui DT, Cheng MT, Chiang HL (2009) Characteristics of elements in waste ashes from a solid waste incinerator in Taiwan. J Hazard Mater 165:766–773 Chen A, Dietrich KN, Huo X, Ho SM (2011) Developmental neurotoxicants in E-waste: an emerging health concern. Environ Health Persp 119:431–438 Chou JD, Wey MY, Liang HH, Chang SH (2009) Biotoxicity evaluation of fly ash and bottom ash from different municipal solid waste incinerators. J Hazard Mater 168:197–202 Feng YJ, Yang YQ, Zhang C, Song EX, Shen DS, Long YY (2013) Characterization of residues from dismantled imported wastes. Waste Manag 33:1073–1078 Ferreira-Baptista L, De Miguel E (2005) Geochemistry and risk assessment of street dust in Luanda, Angola: a tropical urban environment. Atmos Environ 39:4501–4512 Forteza R, Far M, Segui C, Cerdá V (2004) Characterization of bottom ash in municipal solid waste incinerators for its use in road base. Waste Manag 24:899–909 Gidarakos E, Petrantonaki M, Anastasiadou K, Schramm KW (2009) Characterization and hazard evaluation of bottom ash produced from incinerated hospital waste. J Hazard Mater 172:935–942 Gilbert RO (1987) Statistical methods for environmental pollution monitoring. Van Nostrand Reinhold, New York, pp 177–185 Guney M, Zagury GJ, Dogan N, Onay TT (2010) Exposure assessment and risk characterization from trace elements following soil ingestion by children exposed to playgrounds, parks and picnic areas. J Hazard Mater 182:656–664 Hu X, Zhang Y, Luo J, Wang T, Lian H, Ding Z (2011) Bioaccessibility and health risk of arsenic, mercury and other metals in urban street dusts from a mega-city, Nanjing, China. Environ Pollut 159:1215– 1221 Huo X, Peng L, Xu X, Zheng L, Qiu B, Qi Z, Zhang B, Han D, Piao Z (2007) Elevated blood lead levels of children in Guiyu, an electronic waste recycling town in China. Environ Health Persp 115:1113– 1117 Jin Y, Yuan C, Jiang W, Qi L (2013) Evaluation of bioaccessible arsenic in fly ash by an in vitro method and influence of particle-size fraction on arsenic distribution. J Mater Cycles Waste 15:516–521 Kong SF, Lu B, Bai ZP, Zhao XY, Chen L, Han B, Li ZY, Ji YQ, Xu YH, Liu Y, Jiang H (2011) Potential threat of heavy metals in resuspended dusts on building surfaces in oilfield city. Atmos Environ 45:4192–4204 Leung AO, Duzgoren-Aydin NS, Cheung KC, Wong MH (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
Environ Sci Pollut Res Long YY, Feng YJ, Cai SS, Ding WX, Shen DS (2013) Flow analysis of heavy metals in a pilot-scale incinerator for residues from waste electrical and electronic equipment dismantling. J Hazard Mater 261:427–434 Lu Y, Yin W, Huang L, Zhang G, Zhao Y (2011) Assessment of bioaccessibility and exposure risk of arsenic and lead in urban soils of Guangzhou City, China. Environ Geochem Health 33:93–102 Mench M, Vangronsveld J, Beckx C, Ruttens A (2006) Progress in assisted natural remediation of an arsenic contaminated agricultural soil. Environ Pollut 144:51–61 Meza-Figueroa D, De la O-Villanueva M, De la Parra ML (2007) Heavy metal distribution in dust from elementary schools in Hermosillo, Sonora, México. Atmos Environ 41:276–288 Moya J, Bearer CF, Etzel RA (2004) Children’s behavior and physiology and how it affects exposure to environmental contaminants. Pediatrics 113:996–1006 Ni HG, Zeng EY (2009) Law enforcement and global collaboration are the keys to containing E-waste tsunami in China. Environ Sci Technol 43:3991–3994 Poggio L, Vrscaj B, Schulin R, Hepperle W, Marsan FA (2009) Metals pollution and human bioaccessibility of topsoils in Grugliasco (Italy). Environ Pollut 157:680–689 Puckett J, Byster L, Westervelt S, Gutierrez R, Davis S, Hussain A, Dutta M (2002) Exporting harm: the high-tech trashing of Asia. Basel Action Network, Silicon Valley Toxics Coalition. Available at http:// ban.org/E-waste/technotrashfinalcomp.pdf. Accessed 24 Sept 2010. Ruby MV, Lowney YW (2012) Selective soil particle adherence to hands: implications for understanding oral exposure to soil contaminants. Environ Sci Technol 46:12759–12771 Ruby MV, Davis A, Link TE, Schoof R, Chaney RL, Freeman GB, Bergstrom P (1993) Development of an in vitro screening test to evaluate the in vivo bioaccessibility of ingested mine-waste lead. Environ Sci Technol 27:2870–2877 Ruby MV, Davis A, Schoof R, Eberle S, Sellstone CM (1996) Estimation of lead and arsenic bioavailability using a physiologically based extraction test. Environ Sci Technol 30:422–430 Ruby MV, Schoof R, Brattin W, Goldade M, Mosby DE, Castee L, Berti M, Carpenter M, Edwards D, Cragin D, Chappell W (1999) Advances in evaluating the oral bioavailability of inorganics in soil for use in human health risk assessment. Environ Sci Technol 33:3697–3705 Shen CF, Huang SB, Wang ZJ, Qiao M, Tang XJ, Yu CN, Shi DZ, Zhu YF, Shi JY, Chen XC, Setty K, Chen YX (2008) Identification of Ah receptor agonists in soil of E-waste recycling sites from Taizhou area in China. Environ Sci Technol 42:49–55 Shi H, Kan L (2009) Leaching behavior of heavy metals from municipal solid wastes incineration (MSWI) fly ash used in concrete. J Hazard Mater 164:750–754
Sushil S, Batra V (2006) Analysis of fly ash heavy metal content and disposal in three thermal power plants in India. Fuel 85:2676– 2679 Turner A, IP KH (2007) Bioaccessibility of metals in dust from the indoor environment: application of a physiologically based extraction test. Environ Sci Technol 41:7851–7856 USEPA (1989) Human Health Evaluation Manual. EPA/540/1-89/002. Risk Assessment Guidance for Superfund, vol. I. Office of Soild Waste and Emergency Response USEPA (1996) Soil Screening Guidance: Technical Background Document. EPA/540/R-95/128. Office of Solid Waste and Emergency Response USEPA (2001) Risk Assessment Guidance for Superfund: Volume III— Part A, Process for Conducting Probabilistic Risk Assessment. US Environmental Protection Agency, Washington, DC. EPA 540-R02-002 USEPA (2011b) Exposure Factors Handbook; EPA/600/R-090/052F; U.S. Environmental Protection Agency, Office of Research and Development, National Center for Environmental Assessment: Washington, DC USEPA (2011a) Risk Assessment Guidance for Superfund. In: Part A: Human Health Evaluation Manual; Part E, Supplemental Guidance for Dermal Risk Assessment; Part F, Supplemental Guidance for Inhalation Risk Assessment, vol. I USEPA (2012) Mid-Atlantic Risk Assessment Regional Screening Ta ble . ht tp: //ww w. epa.g ov /reg 3h w m d / r i sk / h um a n / r b concentration\_\_table/index.htm. Accessed May 2014 Yang H, Huo X, Yekeen TA, Zheng Q, Zheng M, Xu X (2012) Effects of lead and cadmium exposure from electronic waste on child physical growth. Environ Sci Pollut Res Int 20:4441–4447 Yao J, Li WB, Kong QN, Wu YY, He R, Shen DS (2010) Content, mobility and transfer behavior of heavy metals in MSWI bottom ash in Zhejiang province, China. Fuel 89:616–622 Zemba SG, Green LC, Crouch EA, Lester RR (1996) Quantitative risk assessment of stack emissions from municipal waste combustors. J Hazard Mater 47:229–275 Zheng L, Wu K, Li Y, Qi Z, Han D, Zhang B, Gu C, Chen G, Liu J, Chen S, Xu X, Huo X (2008) Blood lead and cadmium levels and relevant factors among children from an e-waste recycling town in China. Environ Res 108:15–20 Zheng N, Liu JS, Wang QC, Liang ZZ (2010a) Heavy metals exposure of children from stairway and sidewalk dust in the smelting district, northeast of China. Atmos Environ 44:3239–3245 Zheng N, Liu J, Wang Q, Liang Z (2010b) Health risk assessment of heavy metal exposure to street dust in the zinc smelting district, Northeast of China. Sci Total Environ 408:726– 733
RESEARCH ARTICLE
Bioaccessibility and health risk of heavy metals in ash from the incineration of different e-waste residues Xiao-Qing Tao & Dong-Sheng Shen & Jia-Li Shentu & Yu-Yang Long & Yi-Jian Feng & Chen-Chao Shen
Received: 15 June 2014 / Accepted: 3 September 2014 # Springer-Verlag Berlin Heidelberg 2014
Abstract Ash from incinerated e-waste dismantling residues (EDR) may cause significant health risks to people through ingestion, inhalation, and dermal contact exposure pathways. Ashes of four classified e-waste types generated by an incineration plant in Zhejiang, China were collected. Total contents and the bioaccessibilities of Cd, Cu, Ni, Pb, and Zn in ashes were measured to provide crucial information to evaluate the health risks for incinerator workers and children living in vicinity. Compared to raw e-waste in mixture, ash was metal-enriched by category incinerated. However, the physiologically based extraction test (PBET) indicates the bioaccessibilities of Ni, Pb, and Zn were less than 50 %. Obviously, bioaccessibilities need to be considered in noncancer risk estimate. Total and PBET-extractable contents of metal, except for Pb, were significantly correlated with the pH of the ash. Noncancer risks of ash from different incinerator parts decreased in the order bag filter ash (BFA)>cyclone separator ash (CFA)>bottom ash (BA). The hazard quotient for exposure to ash were decreased as ingestion>dermal contact>inhalation. Pb in ingested ash dominated (>80 %) noncancer risks, and children had high chronic risks from Pb (hazard index >10). Carcinogenic risks from exposure to ash were under the acceptable level (Ni. The largest bioaccessible fractions of Cu (79 %) and Ni (58.1 %) were found in BA, whereas the largest bioaccessible fraction of Zn (55.8 %)
was found in BFA and the largest bioaccessible fractions of Cd (88 %) and Pb (75.1 %) were found in CFA. The bioaccessible fractions of the heavy metals in the BA, CFA, and BFA varied widely among the four tests. Comparing the bioaccessibility (Fig. 2) with the total concentration (Fig. 1) of each metal, Pb had the highest total concentration (30,100 mg.kg−1) but the lowest bioaccessible fraction (28.2 %), and Cd had the lowest total concentration
Environ Sci Pollut Res
Sig.
Cd Cu Zn Ni Pb
CGP =96.9+0.55Ctotal −14pH CIP =142+0.36Ctotal −20.5pH CGP =−212+0.53Ctotal −9.79pH
0.966 0.957 0.986
0.000 0.000 0.000
CIP =−153+0.3Ctotal +11.7pH CGP =416+0.29Ctotal +54.1pH CIP =2790+0.29Ctotal −620pH CGP =−46.4+0.39Ctotal +2.84pH CIP =10.7+0.21Ctotal −1.88pH CGP =8050+0.24Ctotal-709pH CIP =2300+0.063Ctotal −299pH
0.977 0.837 0.710 0.930 0.936 0.614 0.564
0.000 0.004 0.042 0.000 0.000 0.119 0.178
GP and IP were two simulated stages of physiologically based extraction test (PBET) GP gastric phase, IP intestinal phase
50
30
9
Ingestion 20
5.6 4.2 2.8 1.4 0.0
10 0
165 3
110 55
2
Dermal contect 1.8
1
1.2 0.6 0.0
0
300
4
200 3
100 Inhalation 20 15 10 5 0
Total Hazard Quotient
18
Total Hazard Quotient
Hazard Quotient -2
40
27
-3
R
BFA
Total Hazard Quotient (10 )
Regression equations
CFA
36
-5
Element
BA
45
Hazard Quotient (10 )
Table 2 Multiple regression analysis of the PBET-extractable metal concentrations and total metal concentrations in the ash samples and the pH values of the ash samples
2010; Hu et al. 2011; Jin et al. 2013; Lu et al. 2011), in which pH having been found to be the most common and significant factor. The pH values of the ash samples are shown in Table S1. The relationship between the bioaccessible concentration of each metal (in the GP and IP), the total concentration of the metal, and the pH of the ash were examined using multiple regression analysis (Table 2) to determine the effect of the pH on the bioaccessibility of the heavy metals in the EDR ash. The bioaccessibilities of the heavy metals in the ash samples were significantly correlated with the pH of the ash at relatively low total metal concentrations (R>0.710, PBA. The risk posed by Cd in BFA was more than twice the risk posed by Cd in CFA, and the risk posed by Pb in CFA was almost twice the risk posed by Pb in BA. These results indicate that the risks of noncancer toxicity may increase as the ash particle size decreases, which agrees with the results of other studies, in which health risks have been found to increase as the particle size decreases (Jin et al. 2013). The risk of noncancer Pb toxicity from ingesting ash from all four tests contributed 83.4 to 92.7 % of the noncancer toxicity risk posed by all five heavy metals. Cd and Pb in BFA from all four tests and Pb in BA from the first test were found to pose risks of adverse health effects through the dermal contact exposure pathway. The total heavy metal concentrations in ash from all four tests were found to pose the risk of noncancer toxic effects through dermal contact. Compared with the risks associated with exposure through ingestion and dermal contact, inhalation was found to be unlikely to pose risks of adverse health
-5
Risk assessment
effects, the HQs for exposure through inhalation being below 0.005 for the total metal concentrations in the ash samples from all four tests. The HQs for exposure to ash through different exposure pathways for all five heavy metals decreased in the order ingestion>dermal contact>inhalation. Therefore, different exposure pathways presented different levels of risk of noncancer toxicity for each heavy metal. The HI values (Fig. 4) for the exposure of children to heavy metals through the three exposure pathways showed that the ash from all four tests would pose high levels of chronic risk. The highest level of noncancer risk to children (HI=52) was found to be posed by BFA from the fourth test, in which Pb exposure through all three exposure pathways contributed 81.3 % of this HI. The risk posed to children by Pb exposure through the ingestion of ash would, therefore, be of grave concern. However, the alarming HQPb that was found for children in this study was much lower than the HQPb values in an e-waste recycling workshop (HQPb =402) and in a near street of such workshop (HQPb =82.6) to children (Leung et al. 2008). It has been found by a number of surveys that children
Hazard Quotient (10 )
A risk assessment was conducted to determine whether the less bioaccessible heavy metals could pose risks to a population working in and living near an EDR incinerator and to investigate the impact factors and to what degree they influence the values of health risk. That would be described in the next section.
Ash from four types of e-waste incinerated
Fig. 4 Characterization of noncarcinogenic risks (hazard quotient) to workers from heavy metals in the four types of e-waste incinerated ash. BA bottom ash, CFA cyclone separator ash, BFA bag filter ash. 1, 2, 3, and 4 stand for the ash samples from four types of raw e-waste incinerated. Total hazard quotient is the sum of each heavy metal’s hazard quotient. Total=Cu+Zn+Ni+Cd+Pb
Environ Sci Pollut Res
BA
125
CFA
BFA
Childern 100 75
that to children, but the hazard values to workers were lower than those to children. The relatively high risk values for the children might be partly attributed to the higher ash ingestion rate (200 mg day−1) that was used for the children than for the workers to estimate the risks posed, the smaller body sizes of children than of workers, and the lack of protective measures that children would take. It has been suggested that children are the most sensitive to risks from pollutants in ash because of more outdoor-playing time, hand-to-mouth activities (mouthing and chewing), deliberately eating the contaminated food, pica behavior as well as less-developed immune systems and higher rates of pollutant absorption (Moya et al. 2004; Meza-Figueroa et al. 2007; Zheng et al. 2010b; Guney et al. 2010). Children sometimes accompany their parents to the workplace and are often exposed to the contaminated environment without any protective measures, which caused they easily be exposed to ash containing heavy metals (Leung et al. 2008). Ruby et al. (1996) found that using total heavy metal concentrations to assess potential risks from ingestion caused the risks of health effects being overestimated. We compared the HQ for ingestion (calculated from the total metal concentrations) with the HQ′ for ingestion (calculated from the bioaccessible fractions of the metals) and also found that HQ for ingestion almost always overestimated the health risk to people from the ingestion of ash. Figures 3 and 4 show that excluding the bioaccessibility of the metals in the ash would result in the risks of noncancer effects being overestimated by a factor of two and, importantly, changed the trend in the risks BA
CFA
BFA
-8
15 25
12
-8
Carcinogenic Risk (10 )
Hazard Index
50
Total Carcinogenic Risk (10 10 )
living near e-waste sites have elevated concentrations of Cd and Pb in their blood (Chen et al. 2011; Huo et al. 2007; Yang et al. 2012; Zheng et al. 2008). Leung et al. (2008) also found that Cu is a pollutant of major concern in e-waste recycling areas. Therefore, urgent attention is required to prevent the health risks of children from them being exposed to Cd, Cu, and Pb in areas where e-waste involving activities are performed. Health risk of ash from EDR incinerated lower than the dust samples of an e-waste recycling workshop and a near street of such workshop mainly caused by the contents of heavy metal in samples from different objects. Different heavy metals content would lead to different degrees of health risk. The risks posed to the health of the workers (Fig. 4) through every exposure pathway to ash from all four tests were almost 10 times lower than the risks posed to children. Only exposure to Pb through the ingestion pathway posed risks of adverse noncancer effects to workers, and the HQ ranged from 1.13 to 3.10 for the ash samples from the four tests. The trend in the HI values (Fig. 5) for workers for the ash samples from the four tests was consistent with the trend that was found for the children. The highest HI value (4.36) was found for BFA from the fourth test. The contributions of each exposure pathway to workers’ noncancer risk were similar to
0 10
Workers
8 6 4 2 0
1
3 2 Considering BA c
4
1
2 3 Omitting BA c
4
Ash from four types of e-waste incinerated Fig. 5 Characterization of noncarcinogenic risks (hazard index) to children and workers in the four types of e-waste incinerated ash. BA bottom ash, CFA cyclone separator ash, BFA bag filter ash. 1, 2, 3, and 4 stand for the ash samples from four types of raw e-waste material incinerated. BAc is bioaccessibility. Hazard index (HI) is the sum of HQ values from each heavy metal and each exposure pathway. HI=(Cu+Zn+Ni+Cd+Pb)ing + (Cu+Zn+Ni+Cd+Pb)inh +(Cu+Zn+Ni+Cd+Pb)der, in which ing is the ingestion, inh is the inhalation, and der is the dermal contact exposure pathway in this study
9 Children
6 3 0 15 12 9
Workers
6 3 0
1
2
3 Cd
4
1
2
3 Ni
4
1
2 3 Total
4
Ash from four types of e-waste incinerated Fig. 6 Characterization of carcinogenic risks to children and workers from heavy metals in the four types of e-waste incinerated ash. BA bottom ash, CFA cyclone separator ash, BFA bag filter ash. 1, 2, 3, and 4 stand for the ash samples from four types of raw e-waste incinerated tests. Only Cd and Ni have cancer risk by inhalation exposed pathway. Total carcinogenic risk is the sum of each heavy metal’s carcinogenic risk. Total=Cd+Ni
Environ Sci Pollut Res
(BA and CFA in Fig. 5). In the same way, if the risk of potential adverse health effects were calculated using total heavy metal concentrations, HQCu for CFA from the third test would pose chronic risk of noncancer effects in children. These might have a considerable impact on management or remediation decisions. The USEPA has found that cancer risks lower than 10−6 are acceptable. Only the cancer risks from exposure to Cd and Ni through the inhalation of ash were assessed in this study (Fig. 6). The cancer risk from different ash samples ranged from 2.92×10−8 to 1.31×10−7 for children and from 3.72× 10−8 to 1.67×10−7 for workers, so exposure to ash from the incineration of EDR was found to pose no cancer risk. The cancer risk and HI (noncancer risk) results showed that workers were more likely to suffer from cancer risks and children were more likely to suffer from noncancer risks. The models that were used in this risk assessment were useful for identifying risks to human health through three exposure pathways to heavy metals in ash from the incineration of four different types of EDR. The noncancer risks and the cancer risks posed by the bottom and fly ash from the different tests (i.e., from the incineration of different types of EDR) varied widely. There are several possible reasons for this variability: the type of EDR being incinerated and the pretreatment method used, the physical and chemical properties of the produced ash, different susceptible populations being exposed, parental involvement in dealing with EDR ash, the effects the daily activities and some special behavior habits of children have on, the different exposure pathways, the difference of parameters for calculating the health risk, and the differences in the heavy metal concentrations in the ash caused by its heterogeneous nature. Given the number and magnitudes of the uncertainties in the exposure factors and toxicity estimates, and the absence of site-specific factors, this study should be considered as preliminary and further research should be undertaken before decisive measures are taken to tackle health risks from ash emitted by EDR incinerators.
Conclusions We found that heavy metals were strongly enriched in ash produced by EDR incinerated in each test, and the metal concentrations in all of the ash samples decreased in the order Pb>Zn>Cu>Ni>Cd. A large proportion of each heavy metal in the ash samples was not bioaccessible, the residual ratio being higher than 50 % for Ni, Pb, and Zn. The bioaccessibility of the heavy metals could be roughly predicted from the properties of the ash when the total metal concentrations were relatively low. Ignoring the bioaccessibility of the heavy metals would lead to the health risks being overestimated. The heavy metals, especially Cd, Cu, and Pb, in the ash produced in all four tests were found to pose risks of noncancer effects,
particularly to children, through three exposure pathways (ingestion, inhalation, and dermal contact). The Pb in ingested ash was found to be the main contributor (>80 %) to noncancer health risks. Many factors would affect the values of health risk posed by exposure to ash, thus further research should be undertaken before any decisive measures are taken to decrease the risks from exposure to ash produced in EDR incinerators.
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