You are on page 1of 9

Journal of Himalayan Earth Sciences Volume 49, No. 1, 2016 pp.

68-76

Arsenic exposure assessment from ground water sources in Peshawar Basin of
Khyber Pakhtunkhwa, Pakistan
Seema Anjum Khattak1*, David Polya2, Liaqat Ali1 and M. Tahir Shah1
1National Centre of Excellence in Geology, University of Peshawar
2School of Earth Atmospheric and Environmental Sciences, The University of Manchester, UK.

*Corresponding author E-mail: seemakhattak2003@yahoo.com

Abstract

Arsenic contaminated groundwater in some south Asian countries like Bangladesh and West Bengal
India is one of the largest environmental health hazards in the world. PCRWR with the help of UNICEF has
carried out a nationwide survey for drinking water arsenic contamination in different parts of Pakistan which
also included limited number of samples from Mardan, Peshawar and Mingora in KPK province. In order to
know the existence of arsenic contamination in ground water of the Peshawar basin, about 30 drinking
exposure (human hair and nails samples from different parts of the Peshawar basin have been collected.
Drinking/cooking water, raw rice, hair and nails samples were analyzed for total arsenic by ICP-MS. Chronic
Daily Intake (CDI mg/Kg Body weight) was calculated for arsenic risk assessment of all the volunteers who
participated in this study. All drinking/cooking water samples were found below the 10 µg/L arsenic
concentration which is the WHO provisional guideline values. The results were also confirmed by the
biomarkers of arsenic exposure from the study population.

1. Introduction 2007; 2009; Nickson, 2005).

Ground water arsenic hazard is world wide The maximum reported level of arsenic in
recognized problem which is reported in various ground water from Kalalanwala, Punjab province is
parts of the world (Nickson, 1998; Polya, 2008; about 1900 µg/L (Farooqi et al., 2007a) and 906
2010; Rahman, 1996; Rahman, 2009; Sengupta, µg/L in Muzaffar Ghar district (Nickson et al.,
2003; Smedley, 2002). 2005). On the other hand up to 352 µg/L of
inorganic arsenic in ground water (n=240) has been
Different environmental exposures, for reported recently in Sind province (Baig et al.,
example drinking, cooking with arsenic 2010) with a maximum of 250 µg/L from southern
contaminated water or eating arsenic contaminated parts of Sind (Arain et al., 2007, 2009).
food for example rice and other rice products and
also the cooking methods of food are mainly According to a survey of PCRWR (2002-2008)
responsible for arsenic contamination (Carbonell et the major identified problems of drinking water are
al., 2009; Chakraborti et al., 2009a). due to arsenic, fluoride, nitrates and bacterial
contamination which needs to be addressed
The health hazards (both carcinogenic and immediately (Farooqi et al., 2003, 2007b, 2009;
noncarcinogenic) associated with chronic intake of PCRWR, 2008a).
arsenic due to drinking arsenic contaminated water
have been investigated and well known (Nickson, In order to have an idea about the ground water
1998; Acharyya, 1999; Ahsan, 2009; Argos, 2010; arsenic situation in KPK province, five districts
Shrestha, 2003; Smith, 2009; 1998). Because of its were selected and random sampling strategy was
bioaccumulative nature and persistency in human applied in this study.
(Huang, 2009; Hughes, 2006) USEPA declared
inorganic arsenic as carcinogenic in nature. 2. Peshawar basin

Ground water arsenic problem is newly The Peshawar basin is an intra-mountain basin
identified in Pakistan as a result of a national level (>5500 km2) situated at the southern margin of the
survey program. At some places in Punjab and Sind Himalayas and northwest of the Indus plain
provinces it is well above the maximum permissible between the longitude 71° 15' and 72° 45' E and
limit of WHO (10µg/L) (Ahmad, 2004; PCRWR, latitude 33° 45' and 34° 30' N in the North West
2003a, 2004; Arain, 2007; 2009; Farooqi, 2003; Frontier Province (NWFP) (currently known as
68

which drains almost the whole basin and enters the Peshawar floodplain and Peshawar lacustrine plain near Warsak and falls in the Indus River near sediments. the Swat fluvial micaceous sand. On the basis of perennial Nala that contribute to the Peshawar basin varying lithologies. Irrigation department operated eastern side where it is open for discharge of water. Fig. Charsadda and Swabi) and the drainage system (After Tahirkheli & Burbank. The 1994). Mardan. about 190 tub wells within Peshawar basin. 69 .KPK) of Pakistan. It is bounded by the mountain Both surface water and ground water irrigation ranges of Khyber in the west and northwest. drilled and operated by Public Health Engineering Department (PHED) whereas in rural areas there are The Peshawar basin is fairly flat with average also domestic wells in most of the houses (WAPDA elevation of 300 m above mean sea level. the Bara river and the Kalpani Nala. Attock is practiced in Peshawar basin. The Kabul River is the main river basin are classified as Peshawar piedmont. drainage system and ultimately discharge into the covered soils and hosting aquifers of the Peshawar Kabul river. 1985). Nowshera. 2001). Map of Peshawar Basin (including Peshawar. Besides deposits while quaternary flanglomerates are lying these rivers there are several perennial and non- along the margins of the basin. 1. There are four main rivers draining the central part of the basin is generally covered with Peshawar basin that is the Kabul River. soils and aquifers respectively. irrigate the basin and join the Indus at eastern exit Domestic water supply is served by the 609 wells (Fig. These The west east flowing river Kabul and its tributaries tube wells are used for irrigation purposes. Jehangira. the quaternary sediments. gravels and lacustrine River.1) (Tariq. A number of dug Cherat in the south and Swat in the north and wells are used for irrigation in Mardan and northeast while the Indus River borders its south Charsadda areas.

Precautions were made before taking the samples by allowing the water to run through the 5.5 Williamson Research Centre of the School of Earth MΩ deionized water before being dried at 60 °C. The wash solution was discarded was performed on ICP MS and ICP AES in the and the nails were rinsed at least 3 times with 18. Hair samples were washed with 25 ml acetone (analytical grade from Fisher brand).2. patterns.650. and information on potential exposure sources. rain fall ranges from 340 mm to 630 mm. which asked for demographic. Questionnaire survey temperature of 40-48 °C. such as keratosis and melanosis. ground water used for drinking as well as cooking purpose were collected along with hair and nail 5.1. The wash solution the evaluation of different subgroups of population was discarded and the process was repeated two subjected to arsenic exposure for the risk more times with water and then finally with acetone.5MΩ deionized water collected. UK. smoking patterns and about their present health status and any health problem especially skin 4.3. NCEG. 1999). The samples were collected and analyzed by using standard methods Visible dirt was removed from the nail samples of analyses accompanied by strict quality control using a nylon wire brush and deionized water. Charsadda and Swabi) of Peshawar basin areas The climate of the area ranges from semiarid including urban as well as rural residents (Fig. Climatic condition five districts (Peshawar. diet approximately 1200 mm in Mardan and Nowshera.1%/annum (Population Census. Atmospheric and Environmental Sciences. The years). sample without increasing the cost and arsenic probability. 2). Washing and cleaning procedure samples from volunteers. excluding bottled water). Each participant was interviewed to complete The mean annual potential evaporation is a questionnaire. subtropical continental lowland type in the western These samples were taken from both males and parts to sub humid to subtropical continental females including different age groups (12-75 lowland type in the eastern parts of the basin. assessment process have been applied as it has less After the last wash step. Samples of to avoid any contamination. the hair samples were subjectivity and more representativeness of the allowed to dry overnight at room temperature. sonicated for The water. designated drinking water source. January is the coldest month with an average daily temperature of -2° C. kilometer. Stratified random sampling method for and sonicated for 10 minutes . The Peshawar district has a population of 5. 1994).4. The hottest months are June and July with an average daily 5. University of Manchester. Methodology pipes for a maximum time of 5 minutes in order to purge the source.3. Some physical parameters were 1% Triton-X100 solution was used and sonicated measured in the field while the chemical analysis for 20 minutes. hair and nail samples were 10 minutes and 25 ml of 18. Sampling and field survey filled to the top. Sample collection 1. tube well (or other per sq. Samples (n= 30) were collected from 70 . Mardan. Nowshera. Then measures. water consumption (WAPDA . such 1100 mm in Charsadda and 1500 mm in Peshawar as source of drinking water. The water samples All the procedures of the study were ethically were transported to the geochemistry laboratory of approved by the Ethics Committee of NCEG.941 with a growth rate of 4. stored in the dark at 4 degree °C and later University of Peshawar prior to the commencement transported on to the SEAES University of of the study. Population of the field Area problems. An informed consent based questionnaire Human hair and nails samples were also survey was performed along with the sample collected from the volunteers along with their collection in the field and a GPS was used for consent and stored properly in zip lock plastic bags recording the exact sample location. Manchester. A labelled clean plastic bottle was 5. The selected districts Drinking water samples (unfiltered) were are the highly populated areas of KPK with the collected in acid-washed 500-mL polyethylene population density ranges from 500-1000 persons bottles from the kitchen tap. Replicates samples were also collected. and the lid replaced.

Quality control measures Water samples were analyzed for total Standards reference material (SRM). Concentrations were determined using a 5 point An in house Turbo Pascal program. ICP-MS is useful for those samples DBSCORR program was used for the having very low arsenic as its detection limit for correction of raw instrumental arsenic analysis 71 . Field areas and sample location map for Peshawar Basin KPK. concentration (Gill. Fig. element analysis capability in a single run.. In Sensor) were used to measure the in situ pH. used for the drift correction of the raw instrumental data obtained from the ICP-MS. 60 seconds per samples and multi Water Test Meter.01ng/ml. SRM NIST1640 for drinking and cooking Operating conditions for the instrument were water. All the run in order to check the preparative steps samples were run in duplicate and the standards applied during sample preparation. was used during analysis. 5. 1997). Pakistan. 5. it has temperature and electrical conductivity of the the ability to measure a large range of drinking water samples in field. calibration curve. It is also preferred for its rapid Calibrated portable probes (Hanna analysis i. were run after every set of 10 samples. Whatman Conductivity m. (2005). 2.7.6.e. Field analysis most of the elements is typically below 0. External standards Arsenic was detected at m/z = 75 with mass and reagent blanks (acid blanks and Milli Q interference from 40Ar35Cl+ corrected through water blanks) were analyzed after every ten monitoring of m/z = 77 and 82 using TJA samples analyzed and duplicate samples were Solutions' Plasma Lab software. addition to its high sensitivity detection. arsenic by ICP-MS (Plasma Quad II (Fissions).5. and human hair CRM NCS DC 73347 the same as described by Gault et al. Chemical analysis 5.

parts of Peshawar basin i. There is a normal according to the International Water variation in the pH and EC. peak areas for (Table 2). 2002b). 0.8. Previously Management Institute. All the physical parameters . Possible reason for the low 6.1-8 µg/L with a mean value of 0. presentation.and were corrected for blanks. conductivity etc. Table 2.ICP-MS analysis. Peshawar. 2002a). temperature.e. 2007) also reported the alkaline Table 1. The pH availability of favorable environment for the range is 7. Charsadda. Results for physical parameters for ground water used for drinking/cooking in KPK. Data analysis and data presentation agreement with the already reported values of PCRWR. viz. Results of arsenic exposure for the volunteers of Peshawar basin. drift and nature of ground water. (Shahida.1 with mean (7) and median (7) release of arsenic is comparatively less. Mardan and Swabi is in 5. Nowshera. were Public Health and Engineering Department analyzed on the spot at sources of (PHED) tube wells which are very deep and the drinking/cooking water (Table 1). The majority of the samples are collected from pH. 72 . The in the test samples suggest a slightly alkaline average depth of a bore hole in Pakistan is 115 ft nature of water sources. analytical sensitivity using a least square fitting of a linear calibration of replicate analysis of The arsenic concentration ranged from five calibration standards (Polya. such as. Mardan and Mingora and is also less applied for the data analysis and data than the WHO (10 µg/L) recommended presentation.7) in this study For IC. This result for arsenic concentration individual arsenic species.9 µg/L and an average value 1. KPK. 2006-2008 for other KPK areas. SPSS. were integrated by in the drinking and cooking water of different using TRPEAK software (Polya. Microsoft Excel 2003.56 µg/L (SD=1. Different statistical techniques were Peshawar.6 to 9. Results and discussions concentration of arsenic can be the depth and geology of water source (wells and bore holes). guideline value for arsenic concentration for 2007 and Arc GIS9 were used for data drinking water.

Y.. USEPA (1989) one hit model was 12(2). Risk assessment WEDC International Conference. are also much lower than that of arsenic exposed populations in different parts of the The contents of arsenic in hair (mean world which further confirms our results.A.. 2007).. Shah. A.A. 2004. K. information. M. S. The biomarkers of arsenic exposure like biomarkers of arsenic exposure in this area. Kazi.19 mg/Kg) are very References much less than the values obtained for the exposed population in West Bengal India by Acharyya. K. The results show that the ICP MS analysis for the drinking ground water collected Arsenic in scalp hair.. I. K.. Aslam. the value of arsenic to arsenic contamination (Slotnick and Nriagu. 105-107. Baig. 2007.06 µg/Kg. 463-467. H. G.. sediment.. cadmium and lead (CDI µg/kg/body wt. J. Tahir. finger and toenails from the major districts of Peshawar basin were is being considered useful biomarkers for within the permissible limits for arsenic below measurement of chronic arsenic exposure. and Journal of Pakistan Medical body mass index (BMI. 47(1). J. 2005).. Laos. Afridi.. Nature. A... Arain. Q. Sindh. 29(5). Determination of The overall results were within the arsenic levels in lake water.. Kalown. M. Swabi. concentration in human hair and nail samples 2006. Slotnick et al. Pakistan: Estimation of daily actually beneficial for the residents of dietary intake. H. Khuhawar.. Munshi. Vientiane... T. collected by the use of questionnaire survey as it gives the exact picture of the absorbed dose in 8. hair and nail analysis for absorbed dose Previously PCRWR (2003-2004) also reported of arsenic is now considered as very important no anomalous values for arsenic from Peshawar tool for identifying at risk groups. Khairpur Districts. calculated for him/her. Ahmad. Arsenic an Emerging Issue: Experiences from Pakistan. Biomarkers and Mardan which is in accordance with our exposure data are more superior to the one results.. 59. interviewed in the national language. 2005. which is Sindh.. used to estimate excess life time cancer risk due Arain. This is the first study using human Arain.12 mg/Kg) and both hand and toe nails (mean value of (0.) for each individual was levels in hair and toenail samples in calculated on the basis of this provided pakistan. 30th 7.. Conclusion the biological system from all sources of exposure (Karagas et al. Rashid. kg/m2) was also Association... 2009. Jamali. Due the WHO (10 µg/L) recommended guideline to the binding of arsenic to keratin of hair and value for arsenic concentration in drinking nails they give an idea about long term exposure water. Nowshera Charsadda and Toxicology. Food and Chemical Peshawar. 1999. Zehra. Majidano. Chronic Arsenic poisoning.A. 2004. Jamali.G. value of (0. M. A. 401. Rahman. 71-86. A Preliminary Study on the Arsenic Contamination of The calculated mean values for chronic Underground Water of Matiari and daily intake from drinking water (0. Anwar. R.. T. G. T. is far less than the same values calculated Journal of the Chemical Society of for arsenic exposed area of West Bengal and Pakistan. 545-545. 73 . 242-248. Pakistan. Combodia (Gault. BW). M. Ahsan. T. Mardan. 2008 ... 2001a). S. Urdu. M. M.. N. S. 2004 and by Gault et al 2006 in Ganges delta. principal user of each water source was 2009. maximum contamination level values for and foodstuff from selected area of arsenic contents of drinking water. Polya. Samanta... A. urine. B. Banglesh (Boyce. Sarfraz. 2010. Chronic daily intake Anwar. M. Arsenic poisoning in the Samantha et al. A. Jalbani. to arsenic intake from ground water and rice. Kazi. During the field survey at least one Ahsan. Rahman. Baig. M. 1996. 2008..B. 2009). Environmental sciences. In addition. Arsenic. 2004.

Environmental arsenic via the drinking water and Pollution. M. R. T. G. Skin contaminated groundwater in the 74 .A. B. In Gill. M..J. Assessment... M. Presence of arsenic in Sampson. Shah. M...Q. D.. Toxicology.. 168-176. Distribution of highly arsenic and Baig.. T.. D. R. Araujo. Carbonell. A. Jamali. Beck. S. Jalbani. 1985. The Molecular Nutrition & Food Research. 41(4). India. R.K. agricultural products from Arsenic in hair and nails of individuals arsenic-endemic areas and strategies to exposed to arsenic-rich groundwaters in reduce arsenic intake in rural villages. 539-552. Speciation and evaluation of controlling role of anthropogenic Arsenic in surface water and pollutants in the natural hydrological groundwater samples: a multivariate cycle. J. of rice plants upon exposure to single Environmental Science & Technology and combined contamination by 43(9). 73(5). H. F. M. The Chatterjee. Environmetal Safety. G. R. Ecologica Sinica. Arsenic Burden from Cooked Geochemistry.. Firdous. Y.. A. northern Pakistan. R....K.Q. M. Signes-Pastor. Farooqi. A. Chakraborti... 2009. West Peshawar Basin. M. Afridi. 2009. from east Punjab. 2008.. L.. Pakistan and possible Respiratory effects in people exposed to contaminant sources. near Lahore. 29(6). Ecotoxicology and 213.. M.. J. Pakistan. Environment. Masuda.. case study. Hu. cadmium and lead..A. H. Charnock. H. Pakistan. C. M. 3349-3355. Spencer.Lloyds. Wogelius.. Boyce..A. P. H. N. D. H. Samreth.. Gill. Y. 14(6). Archives of concentrations of inorganic arsenic: Environental Contamination and Use of a margin of exposure approach. D. Human and Ecological Risk Gault.. N. 914-923. 855-863.... 53(5). A.K. Karagas. 2007a.. tobacco smoking in southern part of Farooqi. Gault. F. A.. M. 1997.. Fluoride in highly contaminated Soils Probabilistic analysis of human health causing groundwater contamination in risks associated with background Punjab. N.. N. Geochimica et 114(11). Islam. 56(4). Barrachina.. 693-706. R. Stukel. Sarfaraz. M..A. Rowland. A. T.. Charnock. 2003. Pakistan..A. Greenberg. C. 839-849. S. Mineralogical Magazine. Heavy metal Affected and Nonaffected Areas and accumulation in iron plaque and growth Kolkata City in West-Bengal. Masuda. Polya. S. J.B.. A. D.. Kusakabe. Haider. 145(3).J. J. & Firdous. 1159 -1201. Boothman. B. A90-A90.. N. A. 2006. Kandal province. Polya.. D. A. S. Firdous.E.... Science of The Total Environment. J. copper. Lahore and Kasur districts. Chowdhury. Khandro.. 2008. Rice in the Populations of Arsenic Huang. Kazi. Masuda. Jalbani.S.G. 531-541. Naseem. 2001a. S.234. 67(18). Y. Tosteson. 320-326. Burio. 407(21).A. Toxic fluoride and arsenic S. (Eds. A. Modern Analytical S. 2007b..A.W. Science of The Total Naseem. 2009.. Cambodia.. Ghosh. 393(1). Siddiqui. Vong. magnetostratigraphy fission-track Microcosm depth profiles of arsenic dating and stratigraphic evolution of the release in a shallow aquifer.. A.). A.A.R..D. A. A. Biomarkers of exposure: a poisoning in ground water of case study with inorganic arsenic. N.. B. M. and the 2010. B. Farooqi. N. Nayak. Tahirkheli. E. 1790-1796. 5524-5530. Bengal.. Pakistan. Geochemical Journal. Morris. Acta Farooqi. 2005... I.. Weiss. S. H.... Lewis. Bulletin. D. A. Gomez-Morilla. 2009. Burbank. Shah. Addison.. Environmental Health Perspectives.. Punjab. Sax. P. Vazquez. Sengupta.. Leng... Sources of Arsenic and Cohen. M. 2009...I.. F. fluoride contaminated groundwater Arian. H. Fluoride and arsenic Hughes.. G... Afridi. Electron beam methods. Liu. Cosmochimica Acta. Geological Society of America 69(5). Kalalanwala area. M.. L. J.. Mondal... Das. Masuda... Eldan.R. 96. Maity.

Applied Geochemistry. D. S. Science and Technology. U. 1996. B. Pakistan Council of Research in Water A. arsenic contamination. M. Arsenic and Resources (PCRWR).. DBSCORR version 8.... Unpublished Turbo Pascal Programme. the Ganga-Padma-Meghna- India: A probabilistic risk assessment. Polya. Ph. U. Kundu. S. R. Samanta. India. 23(11). 2003. D... P. Dahal. M. S.. Shrestha. Mukherjee. P. R. routes in three contrasting areas of West A. Nadia district. B. Journal of Environmental Science and Unpublished Turbo Pascal Programme.Maharjan. Resources (PCRWR). Nickson. A. A.. Ahamed. 285- 55-68.. Archives of 2998. Naidu. K. Cancer Risk in Relation to Toenail Department of Earth Sciences (now Arsenic Concentrations in a US SEAES). of Science & Technology. 2987. Health. D. M.. University of Manchester.. 1. Brahmaputra plain of India and Applied Geochemistry. Conference on Arsenic in the 338-338.. drinking water quality report. D. 2968-2976. South-East Asia: With Emphasis on Shahida. Pakistan Council of Research in Water Chakraborti.. of Pakistan.. 58(11). 20(1). Pakitstan.. R. Government of Environment... Muzaffargarh District.... D...A.. and cooking of rice as arsenic exposure P. G. West Bengal.. 2007. Arsenic poisoning of In: Proceedings of the International Bangladesh groundwater. Pakistan Council of Research in Water Rahman. Sengupta. N. Banerjee. Ganguli. Bengal. contamination for water supply in Arsenic and other drinking water rapidly growing megacities of Asia: quality issues.. 75 . M. 2003. and mitigation program in Nepal. Upadhyay. Centre of Excellence in Geology. 31. Monitoring Of Surface Cambodia and Vietnam. Biswas. N.. Arsenic 2009. A. S. D. Roy. Nature..M.. Mondal. J. O. Applied Water Ground Water Air And Soil In Geochemistry. 2005.. Bangladesh.. T. Polya. Rahman. Pakistan D. M. K. Saha. S. B. Q. Dimension. PCRWR.. D. T... Pradhan. UK. 2008. N. Population-based Case-Control Study. Ministry of Bengal. K. D.. K.. Environmental Health. 2003a. K. R. 34(7-8). 2004. and skin- Contamination in groundwater of scales of arsenic victims in West central Sindh. A. Nickson. C. Rice is a major Quamruzzaman.. Asia–Pacific region. Mukherjee.. Maskey. Shrestha. 2008. B. 326(1-3). Chatterjee. 2004. Das. Water Pakistan. Sharma. TRPEAK version 10. Bhattacharya. 33-47. Dutta. 185-200. A. Bhattacharya. Environmental B. 701- Polya. Banerjee.. American Journal of Epidemiology Polya. its health impact 477.. D. Science of The Total Science & Technology.. K. 153(6). R.. Hossain. Pakistan.. 395. Ministry of region. Arsenic contamination in contamination in ground water of groundwater in the Southeast Asia southern Punjab. Tuladhar. 2010. Peshawar Basin Against Time The 3rd Polya. Government of and Health. PCRWR.. Chowdhury. Case of Karachi. Pakistan. 463. G. T. nails. 2008. Roychowdhury. N.. Pati.. M. R. 38(1)... Lowry.. University of Peshawar. R. 23(11).. thesis. M. 1998. 2002b. M.A. Ministry Nayak. India. National M. exposure route for arsenic in Chakdaha Groundwater arsenic contamination in block. 292. Arsenic other elements in hair.. Khadka. McArthur.. Rahman. M.. 559-565. D. Comparison of drinking water. Groundwater as source of Kyaw-Myint. M... 2002a. Groundwater Geochemistry and Health. Mondal. C.. Lodh.D.. Resources (PCRWR). Arsenic in Groundwaters of 702. 32(6). A. R. 9-21. Government Chakraborti. B. Shrestha. Giri. raw rice Shrestha. Environmental Geochemistry Science & Technology. R.

R. A.gov. 125.. L. C. Province. WAPDA. thesis. M. Essex. 517-568.. H. Slotnick. Y. 1994. Environmental Health. Tariq. A.D. A. J. Meliker.J. intake from drinking water and foods. A Directorate.. N. Nriagu. 19(4)...A. 17.. D. behaviour and institute of Applied Geosciences. 2006. J.. water of the North West Frontier 139. Ph. 76 .. 147(7).Wesley Longman Limited. 2009. England. Journal of Exposure Science & Environmental Epidemiology.F..Slotnick.. G.hec. S. Netherlands. 2002. Nriagu... Toenails surface water and soil in Peshawar as a biomarker of inorganic arsenic basin. American Journal of Epidemiology. National Centre of Excellence in J o u r n a l o f To x i c o l o g y a n d Geology. R.P. thesis.. Hydro geology Smedley. Biggs. P. 102(1). 1998.. M. Smith. Pakistan.. 215-234.O. M. 2001. Increased lung cancer risks are similar whether arsenic is ingested or inhaled. Environmental geochemistry of Ghosh. the distribution of arsenic in natural waters. Ph.D. Goycolea. Applied Geochemistry. M. Validity of http://eprints. Pakistan and TNO-DGV review of the source. G. 148-158. 70(2). Marked Increase in Bladder and Lung Cancer Mortality in a Region of Northern Chile Due to Arsenic in Drinking Water. 343-348. Ercumen. University of Peshawar.. Haque. Steinmaus. J. AvRuskin.J.pk/7065/1/3016 human nails as a biomarker of arsenic H. Hydrogeology and ground Environmental Research. 660- 669. Pakistan.O. 2007.. M.W. D. L.htm and selenium exposure: A review. H. Yuan. Kinniburgh... Smith.