Polychlorinated biphenyl (PCBs) in rice grains and straw; risk surveillance, congener specific analysis, distribution and source apportionment from selected districts of Punjab Province, Pakistan

Science of the Total Environment 543 (2016) 620–627

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Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv

Polychlorinated biphenyl (PCBs) in rice grains and straw; risk surveillance, congener specific analysis, distribution and source apportionment from selected districts of Punjab Province, Pakistan Mehvish Mumtaz a, Andleeb Mehmood b, Abdul Qadir a, Adeel Mahmood c,f,⁎, Riffat Naseem Malik d, Arshed Makhdoom Sabir e, Jun Li f, Gan Zhang f a

College of Earth and Environmental Science, University of the Punjab, Lahore, Pakistan Department of Chemistry, Mirpur University of Science and Technology (MUST), Mirpur, AJ&K, Pakistan c Department of Biosciences, COMSATS Institute of Information Technology, Islamabad PO: 45550, Pakistan d Environment Biology and Ecotoxicology Laboratory, Department of Environmental Sciences, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad 45320, Pakistan e Rice Research Institute Kala Shah Kaku, 17 Km G.T. Road, Lahore, Pakistan f State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China b

H I G H L I G H T S

G R A P H I C A L

A B S T R A C T

• PCBs levels fall within the permissible limits of tolerable daily intake. • Hazard ratio suggested no considerable carcinogenic risk to humans. • Urban fraction was found dominant in spatial distribution.

a r t i c l e

i n f o

Article history: Received 7 July 2015 Received in revised form 22 September 2015 Accepted 26 October 2015 Available online xxxx Editor: Adrian Covaci Keywords: PCBs Rice

⁎ Corresponding author. E-mail address: [email protected] (A. Mahmood).

http://dx.doi.org/10.1016/j.scitotenv.2015.10.126 0048-9697/© 2015 Elsevier B.V. All rights reserved.

a b s t r a c t The current study presents health risk surveillance by investigating the levels of polychlorinated biphenyls (PCBs) in rice (Oryza sativa L.) grains and rice straw. Samples were collected from four districts (Okara, Sahiwal, Lahore and Sheikhpura) of Punjab Province, Pakistan for congener specific analysis of PCBs, and to observe the spatial distribution pattern and point sources. Level of Σ30 PCB (ng g−1) in rice grains and rice straw ranged from 4.31 to 29.68 and 6.11–25.35, respectively. Tetra-CBs were found predominant in rice straw (49%) and grains (38%) over other PCB homologs. No significant variation (P N 0.005) was observed for most of the screened PCBs congeners except, PCB-66, -77, -60, -101, -74, -138, -153 and -105 in rice grains and PCB-66 in rice straw. Reported toxicity equivalency (TEQ) values for dioxin like PCBs in rice grains were found lower than the previously published reports from Asian countries, however higher TEQ values are reported for rice straw in this

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TEQs Human health risks Pakistan

study. Health was found at risk of cancer among one in million by consumption of the study area food stuffs, though no considerable carcinogenic risks to human health was found. © 2015 Elsevier B.V. All rights reserved.

1. Introduction

pioneer study deals with the congener specific analysis, spatial distribution pattern of PCBs and probable hazardous impact on humans and animals through consumption of exposed dietary items (rice grains and straws, respectively) from Punjab Province, Pakistan.

About 209 congeners of polychlorinated biphenyls (PCBs) were synthesized commercially and 130 congeners have been identified in different commercial products. Their structure consists of two benzene rings linked with each other while hydrogen atoms are replaced with chlorine atoms. Approximately 1.2 million metric tons of PCBs were synthesized during 1929–1977 (WHO, 1993), they also produced by combustion of chlorine and carbon containing compounds (Ahmed, 2003). Leakage of transformer oil during repairing, transportation and auctions of old transformers to industries at low cost are the reasons of PCB contamination in surrounding environment (Eqani et al., 2013; Mahmood et al., 2014d). In 1970s, due to the toxicity of persistent organic pollutants (POPs), PCBs were banned in developed countries, however in past about 2 million tons of PCBs mixture had been transported and accumulated in environment (Roszko et al., 2014). PCBs have detrimental effects on humans (Safe, 1994; Longnecker et al., 1997; Damstra, 2002; Storelli, 2008) such as reproductive abnormalities (Yen et al., 1989; Chen et al., 2015), endocrinal disruption (Colborn et al., 1993; Brouwer et al., 1999) neurological effects (Tilson and Kodavanti, 1997), cancer (Tsongas et al., 2000; Kumar et al., 2014) depressive responsiveness, intelligence quotient (IQ) level decreased and impairment of vision (Bell, 2014; Kodavanti, 2014). PCBs exposed children exhibit neurophysiological effects (Schantz et al., 2003) and stunted growth (Jacobson et al., 1990). A number of studies conducted on animals (Cheng et al., 2009), elaborated that wild life is also not safe from toxicological effects of PCBs, posing behavioral and functional abnormalities (Kodavanti, 2014). Due to toxicological properties and uncertain ecological behavior, POPs became a global concern. Many agreements (trans-boundary movement of hazardous pollutants to overcome air pollution 1998, Stockholm convention 2001) were signed to overcome this issue (Elabbas et al., 2013). Pakistan has signed many multilateral environmental agreements (MEAs) including Stockholm convention on POPs but still PCBs are being reported from the environment of Pakistan (Eqani et al., 2013; Mahmood et al., 2014a, 2014b, 2014c, 2014d). Although, PCB levels in environment have been decreasing slowly, and it has been estimated that during 2005 the emission of PCB was about 10% of those released in 1970s (Mahmood et al., 2014d). Plants uptake PCBs from soil through roots and transfer to foliar parts and grains (Zhao et al., 2006). Rice being the staple food fulfill about 60% of the world's food requirements while rice straws are consumed by animals as fodder particularly in winter season (Drake et al., 2002; Mahato and Harrison, 2005; Nguyen et al., 2008; Hou et al., 2013). Literature revealed that across the glob, a number of reports have been published to present the levels of PCBs in rice. Poland (Roszko et al., 2014; Witczak and Abdel-Gawad, 2012; Witczak and Abdel-Gawad, 2012), Germany (Petzold et al., 1999), Netherlands (Baars et al., 2004), Japan (Tsutsumi et al., 2001; Mato et al., 2007), China (Zhao et al., 2009; Xing et al., 2010; Song et al., 2011), Italy (Fattore et al., 2008), South Korea (Son et al., 2012) and Spain (Marin et al., 2011) have contributed literature on this issue. Very few reports are available on levels of PCBs in rice straw (Chu et al., 1999; Fan et al., 2009; Tato et al., 2011). Published reports on PCBs levels from the environment (soil, air, water, sediments) of Pakistan are increasing day by day (Tariq et al., 2004; Ahmad et al., 2008; Khan et al., 2010; Syed and Malik, 2011; Eqani et al., 2012; Syed et al., 2013a; Syed et al., 2013b; Alamdar et al., 2014; Syed et al., 2014; Mahmood et al., 2014a, 2014b; Mumtaz et al., 2015) however, only one report reflects the PCBs level in food chain commodities (Mahmood et al., 2014d), while not even a single report available for the residual levels of PCBs in rice straw. The

2. Materials and methods 2.1. Sampling Four sampling districts named Okara, Sahiwal, Sheikhpura and Lahore were selected from Punjab Province, Pakistan (Fig. 1). Rice straw and rice grains samples were collected from twenty sampling sites (five sites from each district) according to stratified random sampling from minimum 15 km distance between two sampling sites. Whole rice plant was collected during harvesting season (October–November 2013). Kernel and stem were separated and placed in separate labeled bags. Samples were transported to Environmental Toxicology Laboratory, College of Earth and Environmental Sciences, University of the Punjab, Pakistan in ice box and placed at −20 °C in freezer until further analysis (Sojinu et al., 2012; Mahmood et al., 2014d). 2.2. Extraction and cleanup Rice grain (n = 20) and rice straw (n = 20) samples were grinded into powdered form and 10 g sample was extracted in dichloromethane (DCM) through Soxhlet apparatus for more than 24 h (Barriada-Pereira et al., 2003; Ahmad et al., 2008). Extracts were evaporated via rotary evaporator and solvent phase was changed from DCM to n-hexane. Alumina/silica columns were used for clean-up of extracts and resulting extract was concentrated up to 0.2 ml under gentle high purified nitrogen stream (Mahmood et al., 2014a). PCB-54 was added as internal standard before injecting the samples on GC-MS. 2.3. Chromatographic analysis Chromatographic analysis was performed by GC–ECNI-MS (gas chromatography electron capture negative ion mass spectrometry), Agilent 7890. Selected ion monitoring (SIM) mood was used for analysis of PCBs congeners (PCB-8, PCB-37, PCB-44, PCB-49, PCB-52, PCB-60, PCB-66, PCB-70, PCB-74, PCB-77, PCB-82, PCB-87, PCB-99, PCB-101, PCB-105, PCB-114, PCB-118, PCB-126, PCB-128, PCB-138, PCB-153, PCB-156, PCB-166, PCB-170, PCB-179, PCB-180, PCB-183, PCB-187, PCB-189, PCB-198). Throughout analysis injector port temperature was maintained 250 °C. Following scheme was followed during analysis; temperature was 150 °C for first 3 min and 4 °C/min to 290 °C. For 10 min isothermal process was kept. The source temperature of MSD (mass spectrometer detector) and quadruple temperature was 230 °C and 150 °C respectively (Mahmood et al., 2014a). 2.4. Quality control and quality assurance (QA/QC) Quality control procedure was strictly followed for the all samples to ensure the quality of results. Calibration standards were used daily for instruments calibration. All the chemicals used during the experimentation were of analytical grade and purchased from Merck (Germany). Standards for BDE and DP were purchased from Dr. Ehrenstorpher GmbH, Germany. Field, procedural and solvent blanks were analyzed by the similar methodology, adopted for original samples. Glassware was double washed with distilled water and backed at 450 °C for more than 6 h. Agilent MSD Productivity Chemstation software was

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Fig. 1. Study area map showing locations of sampling sites.

used for data processing and acquirement. Average surrogate recoveries in all samples for TCmX (tetrachlorometaxylene) ranged between 53 and 71% and average recovery for PCB-209 was ranged between 76 and 82%.

2.5.2. HR and carcinogenic effects For HR following formula was used (Dougherty et al., 2000)

HR ¼

EDI CBC

2.5. Human health risk assessment Risk to human health was calculated by following United State Environmental Protection Agency (USEPA) guidelines. For the evaluation of non-carcinogenic effects, estimated daily intake (EDI) was calculated via consumption of rice grains and compared with tolerable daily intake (TDI). On the other hand, Hazard ratio (HR) was calculated to highlight carcinogenic effects.

where CBC = cancer benchmark concentration and calculated as follows:

CBC ¼

ðRL  OSFÞ  BW CR

2.5.1. EDI and non-carcinogenic risk Following formula was used to calculate EDI

where, RL = risk level (10−6), OSF = oral slope factor, BW = average body weight (60 kg), and CR = consumption rate calculated during survey (120 g day−1).

EDI ¼ CR  Concentration of PCBs congeners=BW

2.6. Statistical analysis

where BW is body weight and consumption rate i.e. CR (calculated during sampling and survey).

One way ANOVA along with descriptive statistics were determined by using SPSS (version 21). Sampling locations and spatial distribution patterns of PCBs in the study area were presented by using Arc GIS (version 9.3).

M. Mumtaz et al. / Science of the Total Environment 543 (2016) 620–627 Table 1 Comparison among the current reported PCBs levels with the previously reported data (ng g−1). Matrices

Rice grains

Rice straw

a

623

3. Results and discussion 3.1. Level and PCBs congeners profile

Locations

ΣPCBs

Status with respect to current reporta

References

Current study Pakistan

10.39 1.122

Lower

Italy Netherlands Germany Sweden Japan China Yinking Beijing Pingqiao Luqiao Current study China Australia Italy Northern areas Italy Southern areas Plain area

0.0213 0.025 0.03 0.005–0.011 0.0039 0.01

Lower Lower Lower Lower Lower Lower

Mahmood et al. (2014a, 2014b, 2014c, 2014d) Fattore et al. (2008) Baars et al. (2004) Petzold et al. (1999) Lind et al. (2002) Mato et al. (2007) Nakata et al. (2002)

2.34 522.67 15,682.39 11.56

Lower Higher Higher

Chu et al. (1999) Zhao et al. (2007) Zhao et al. (2007)

129.28 2320 40.18

Higher Higher Higher

Chu et al. (1999) Fan et al. (2009) Tato et al. (2011)

35.03

Higher

Tato et al. (2011)

28.32

Higher

Tato et al. (2011)

Higher or lower than current report.

3.1.1. Rice straw Basic descriptive statistical values for investigated congeners of PCBs are presented in SI Table 1. Mean concentration (ng g−1) of PCBs was found 11.52 ± 5.46 and ranged from 6.11 to 25.35. Maximum contribution to ΣPCBs was made by PCB-70 (2.34 ng g−1) followed by PCB-88 (1.15 ng g−1), PCB-44 (1.04 ng g−1), PCB-99 (0.77 ng g−1) and PCB87 (0.75 ng g−1) while PCB-189 (0.03 ng g−1) contributed least concentration. Scarcity of published data exists for PCBs in rice straw exist. Published literature from China revealed mean concentration 129.28 ng g−1 of PCBs in leaves/straw which was higher than the current reported results (Chu et al., 1999). Results of the present reports were found lower than previously published data from variety of fodder samples collected from northern, southern and main part of Italy (40.18 ng g−1, 28.32 ng g−1, 35.03 ng g−1, respectively) while higher than Australia (2.32–287.60 ng kg−1) (Fan et al., 2009; Tato et al., 2011). Detailed comparison of the current results with available previously published data is presented in Table 1. To the best of our knowledge this is the pioneer study from Pakistan presenting the PCBs congeners profile and levels in rice straw. 3.1.2. Rice grains Average level (ng g−1) of PCBs in rice grain was reported 10.39 ± 5.88 which ranged between 4.31 and 29.68. Detailed levels and descriptive statistical values for each investigated congeners are presented in SI Table 1. Among congeners, PCB-70 (3.36 ng g−1) contributed maximum concentration followed by PCB-88 (0.93 ng g−1), PCB-99 (0.70 ng g−1),

Fig. 2. Study area map showing spatial distribution patterns of PCBs homologs in rice straw samples.

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PCB-87 and PCB-198 (0.73 ng g−1) while PCB-156 (0.04 ng g−1) contributed the least concentrations. Levels of PCBs in the current study were higher than previously published reports on rice grains from Netherlands (mean: 0.025 ng g− 1) (Baars et al., 2004), Sweden (0.005–0.011 ng g− 1) (Lind et al., 2002), Italy (0.0213 ng g−1) (Fattore et al., 2008), Germany (0.03 ng g−1) (Petzold et al., 1999), China (2.34 ng g− 1) (Chu et al., 1999) and Pakistan (mean: 1.12 ng g−1) (Mahmood et al., 2014d). The present results were found lower than previously published data from Pingqiao, China (mean: 522.67 ng g− 1) and Luqiao, China (15,682.39 ng g−1) (Zhao et al., 2007). Detailed comparison of the current results with available previously published data is presented in Table 1. 3.2. PCB homologs pattern Among PCBs homologs tetra-CBs were found predominant in rice straw (49%) and grains (38%). Decreasing trend for percentage contribution of PCBs homologs in rice straw and rice grains was as follows: tetra-CBs N penta-CBs N di-CBs N dioxin-likeCBs N hexa-CBs N triCBs N hepta-CBs and tetra-CBs N penta-CBs N dioxin-like-CBs N diCBs N hexa-CBs N hepta-CBs N tri-CBs. It is important to note that dioxin-like-CBs were ranked third and contributed about 10% of the total PCBs. Various factors like deposition, volatilization, degradation and uptake of congeners from soil by plants may influence the homologs pattern. Distribution of PCBs congeners may also affect the homologs distribution pattern (Li et al., 2008). Results of the present study were in accordance with the previously reported study from Pakistan which exhibited that tetra-CBs were highest contributor to the food chain supplements (Mahmood et al., 2014d). In European food samples mean concentration of non-dioxin like PCBs in cereals was 0.023 ng g−1

which is lower than the presenting concentration in this study (4.02 ng g−1) (Fattore et al., 2008). Visual expression of percentage contribution of each investigated PCBs homologs in rice straw and rice grains is explained in SI Figs. 1 & 2, respectively. 3.3. Potential source and spatial distribution patterns Results of one way ANOVA suggested the non-significant variation (P N 0.005) for most of PCBs in rice grains among sampling districts (Okara, Sahiwal, Lahore and Sheikhpura) and sampling sites within each district. However some congeners i.e. PCB-60, -66, -74, -77, -101, -105, -138, and -153 for rice grain reflected significant variation (P b 0.005). In case of rice straw non-significant variation (P N 0.005) was observed except PCB-66 which exhibited significant results (P b 0.005). Spatial distribution pattern of PCBs homologs from each sampling site of the study area is presented in Figs. 2 & 3, respectively. Visual expression of spatial distribution pattern (Figs. 2 & 3) revealed that district Lahore bear higher PCBs pollution load compared with the other districts. Rice straw and grain samples from Lahore contributed about 33%, 32%, respectively to the total detected PCBs. This is perhaps due to the dense population, urbanization, industrialization and mobilization. When we considered the pollution load from each site of the study area then trend (rice straw) appeared as: Haveli Lakha (Okara) N Yousafwala (Sahiwal) N Wagha border (Lahore) N Sheikhupura (Manawala), while trend for rice grain decreased as: Okara cantt (Okara) N Sahiwal N University of the Punjab (Lahore) N Kala Shah Kako (Sheikhpura). Study campaign was launched in urban and industrial areas of Punjab Province (Bozlaker et al., 2008; Syed et al., 2013a, 2013b). Water bodies of the study area were receives huge efflux of industrial

Fig. 3. Study area map showing spatial distribution patterns of PCBs homologs in rice grain samples.

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Table 2 Comparison of EDI of the current study with previously reported data. PCBs

EDI (ng kg−1 BW

Chinaa (μg kg−1 BW

day−1)

day−1)

Chinab (ng kg−1 BW day−1)

Chinacd (pg kg−1 BW

Pakistan (pg kg−1 BW

South Koreae (ng kg−1 BW

Japan (Tokyo)f (g kg−1 BW

day−1)

day−1)

day−1)

day−1) Year

Di-CBs Tri-CBs Tetra-CBs Penta-CBs Hexa-CBs Hepta-CBs Dioxin like-CBs ΣPCBs

1.87 0.45 9.37 3.81 1.42 0.6 8.04 20.78

Luqiao Pingqiao Control site

Disassembly site

Yuhang

– – – – – – 24.0 5.7

439.5 NA – – – – – 8599.9

– – – – – – 0.06 –

– – – – – – – 0.6

33.8 238.9 – – – – – 2564.8

2001 2002 2003 – – – – – – – 2825

– – – – – – 0.007 3.008

– – – – – – – 310

– – – – – – – 301

– – – – – – 298

On average BW is 60 kg. CR of rice consumption in Pakistan was 120 g−1 person−1 day−1. a Zhao et al. (2007). b Zhao et al. (2009). c Song et al. (2011). d Mahmood et al. (2014d). e Son et al. (2012). f Sasamoto et al. (2006).

wastewater and being used for irrigation purposes that can be responsible for increased levels of contaminants. Our results supported previously published reports from France and China by exhibiting higher pollution load from urban and industrial locations (Motelay-Massei et al., 2004; Ren and Li, 2007). Soil to plants uptake along with the foliar deposition can leads to the increased levels of PCBs in rice crops (Iwata and Gunther, 1976; Chu et al., 1999). 3.4. Toxicity equivalency (TEQ) fluxes Toxicity equivalency factor (TEF) values were used to calculate TEQ values for rice straw and grains (Van den Berg et al., 1998; Van den Berg et al., 2006). TEQ values were calculated for non-ortho (PCB-77, -126) and mono ortho (PCB-189, -156, -118, -114, -105) PCBs congeners. Concentration (ng g−1) for dioxin like PCBs in rice grains ranged from 0.20 to 13.9 with mean value of 4.02 while for rice straw ranged from 0.01 to 6.16 with mean concentration of 1.04 (SI Tables 2 & 3). Scarcity of data exists on TEQ values for rice grains, only few reports were published from other countries for cereals crops and exhibited quiet lower values (Roszko and Szymczyk, 2010; Witczak and Abdel-Gawad, 2012; Roszko et al., 2014). Previously published report from Zhejiang, China, South Korea and Valencia (Spain) reported 0.016, 0.0002 and 0.01 pg g−1, respectively, TEQ value for rice grains, which is lower than the estimated TEQ values of the current study (Song et al., 2011; Son et al., 2012). Reported TEQ value from Pakistan reflected higher values as compared to the value reported in the current study (Mahmood et al., 2014d). When we look at rice straw, previously published data from Japan reported 0.29 pg TEQ g−1 (0.00029 ng TEQ g−1) which is higher than the present study (Uegaki et al., 2006). MAFF (Ministry of Agriculture Forestry and Fisheries) of Japan reported TEQ value (0.24 pg TEQ g−1) for different plants used as fodder that is higher than calculated TEQ in the present study (MAFF, 2003).

previously reported study from Pakistan and China (Mahmood et al., 2014d; Song et al., 2011). Results of the present study and comparison with previously published EDI values are presented in Table 2. ADI for PCBs in rice grains are missing however for other dietary items tolerance level for PCBs ranged from 0.2 to 3 μg g−1 (200 ng g− 1) (U.S. FAO/WHO). Results of the present study were in accordance with tolerable intake levels of PCBs reflected that humans had no noncarcinogenic risk by investigated items in the study area. According to world health organization, tolerable daily intake (TDI) for dioxin like PCBs (Table 3) ranged from 1 to 4 pg TEQ kg− 1 BW day− 1 (World Health Organization (WHO), 2000). Reported results of the present study were in limit of TDI and considered safe for humans consumption. Carcinogenic effects via consumption of rice contaminated with PCBs were based on cancer bench mark concentration (CBC) which is defined as the concentration to which humans are exposed and risk of cancer among 1 in million. From CBC, hazard ratio was estimated that suppose, HR N 1 reflects carcinogenic effects in humans (Dougherty et al., 2000). HR calculated for 50th and 95th percentile of reported PCBs and non- and mono-ortho PCBs is presented in Table 4. For non& mono-ortho PCBs these ratios were quiet lower and represented that humans are safe by consumption of non- and mono-ortho PCBs via rice. Hazard ratio for rice exceeded permissible limits while lower than the previously published report on cereals from Pakistan (PCBs = 0.02 pg g− 1; non- and mono-ortho PCBs = 0.006 pg g− 1) (Mahmood et al., 2014d). Previously published reports from Asia (Hogarh et al., 2012) and Pakistan revealed higher levels of POPs in air of Pakistan (Syed et al., 2013a; Mahmood et al., 2014d) which may contribute to rice grains by atmospheric and foliar deposition (Chu et al.,

Table 3 EDI for dioxin like PCBs (ng TEQ kg−1 BW day−1). Dioxin like PCBs

3.5. Health risk assessment for carcinogenic and non-carcinogenic effects Risk level via consumption of contaminated rice was calculated by comparing with average body weight (Binelli and Provini, 2004). Noncarcinogenic effects to human health were determined by comparing acceptable daily intake (ADI) with estimated daily intake (EDI) (Dougherty et al., 2000; Wang et al., 2011). EDI calculated for the present study was found lower than study reported from China (Zhao et al., 2007; Zhao et al., 2009), Japan (Sasamoto et al., 2006) but higher from

TEQ (ng TEQ g−1)

EDI (ng TEQ kg−1 BW

Standard valuea

day−1) PCB-77 PCB-105 PCB-114 PCB-118 PCB-126 PCB-156 PCB-189 a

0.00 0.01 0.03 0.01 7.50 0.02 0.01

0.00 0.02 0.06 0.02 15.0 0.04 0.02

World Health Organization (WHO) (2000).

1–4 pg TEQ kg−1 BW day−1

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Table 4 Hazard ratio for carcinogenic effects.

ΣPCBs ΣNon- and mono-ortho PCBs

CBC (ng/kg/day)

HR 50th

HR 95th

10 7.5

1.69 0.09

3.954 0.208

Bold values showing carcinogenic effects.

1999). Concentrations of OCPs, PCBs, PCNs and other contaminants are rising in the environment of Pakistan day by day (Syed et al., 2013a; Mahmood et al., 2014a; Mahmood et al., 2014b; Mahmood et al., 2014c; Mahmood et al., 2014d). 4. Conclusion In the current study congener levels, spatial distribution pattern and source apportionment along with the risk surveillance of PCBs to living organisms were determined from four districts of Punjab, Pakistan. Health risks reflected no considerable carcinogenic risk to human health via consumption of PCBs contaminated rice. Results of the present study declared that tetra-CBs contribution was higher in rice straw and rice grains compared with the other CBs. Higher levels of PCBs was observed from Lahore district and considerable levels were detected from the sampling locations near urban and industrial areas. Estimated dietary intake for the present study was in the range of permissible limits; however hazard ratio showed a minor risk to health of living organism, consuming the food stuff of the study area. Appendix A. Supplementary data Supplementary data to this article can be found online at http://dx. doi.org/10.1016/j.scitotenv.2015.10.126. References Ahmad, S., Zia-ul-haq, M., Imran, M., Iqbal, S., Iqbal, J., Ahmed, M., 2008. Determination of residual content of pesticides in rice (Oryza sativa L.) crop from different regions of Pakistan. Pak. J. Bot. 40 (3), 1253–1257. Ahmed, F.E., 2003. Analysis of polychlorinated biphenyls in food products. TrAC Trends Anal. Chem. 22, 170–185. Alamdar, A., Syed, J.H., Malik, R.N., Katsoyiannis, A., Liu, J., Li, J., et al., 2014. Organochlorine pesticides in surface soils from obsolete pesticide dumping ground in Hyderabad City, Pakistan: contamination levels and their potential for air–soil exchange. Sci. Total Environ. 470–471, 733–741. Baars, A.J., Bakker, M.I., Baumann, R.A., Boon, P.E., Freijer, J.I., Hoogenboom, L.A.P., et al., 2004. Dioxins, dioxin-like PCBs and non-dioxin-like PCBs in foodstuffs: occurrence and dietary intake in The Netherlands. Toxicol. Lett. 151, 51–61. Barriada-Pereira, M., Concha-Graña, E., González-Castro, M.J., Muniategui-Lorenzo, S., López-Mahía, P., Prada-Rodríguez, D., et al., 2003. Microwave-assisted extraction versus Soxhlet extraction in the analysis of 21 organochlorine pesticides in plants. J. Chromatogr. A 1008, 115–122. Bell, M.R., 2014. Endocrine-disrupting actions of PCBs on brain development and social and reproductive behaviors. Curr. Opin. Pharmacol. 19, 134–144. Binelli, A., Provini, A., 2004. Risk for human health of some POPs due to fish from Lake Iseo. Ecotoxicol. Environ. Saf. 58, 139–145. Bozlaker, A., Odabasi, M., Muezzinoglu, A., 2008. Dry deposition and soil–air gas exchange of polychlorinated biphenyls (PCBs) in an industrial area. Environ. Pollut. 156, 784–793. Brouwer, A., Longnecker, M.P., Birnbaum, L.S., Cogliano, J., Kostyniak, P., Moore, J., et al., 1999. Characterization of potential endocrine-related health effects at low-dose levels of exposure to PCBs. Environ. Health Perspect. 107, 639–649. Chen, X., J-s, C., Zhang, L., J-g, L., Yao, L., Self, S.G., et al., 2015. Levels of PCDDs, PCDFs and dl-PCBs in the blood of childbearing-aged women living in the vicinity of a chemical plant in Tianjin: a primary study. Chemosphere 118, 1–4. Cheng, J., Yang, Y., Ma, J., Wang, W., Liu, X., Sakamoto, M., et al., 2009. Assessing noxious effects of dietary exposure to methylmercury, PCBs and Se coexisting in environmentally contaminated rice in male mice. Environ. Int. 35, 619–625. Chu, S., Cai, M., Xu, X., 1999. Soil–plant transfer of polychlorinated biphenyls in paddy fields. Sci. Total Environ. 234, 119–126. Colborn, T., vom Saal, F.S., Soto, A.M., 1993. Developmental effects of endocrine-disrupting chemicals in wildlife and humans. Environ. Health Perspect. 101, 378–384. Damstra, T., 2002. Potential effects of certain persistent organic pollutants and endocrine disrupting chemicals on the health of children. J. Toxicol. Clin. Toxicol. 40, 457–465.

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