Distribution of nitrate in the water resources of Pakistan

Water quality monitoring activities have recognized the nitrate contamination in the drinking water sources as one of the major quality issue of Pakistan. Adopting a  uniform sampling design, 747 samples were collected from a wide range of irrigated or non-irrigated regions having distribution of samples in sixteen cities as Lahore (79), Kasur (46), Faisalabad (30), Khushab (50), Chakwal (51), Mianwali (30), Jhelum (53), Bahawalpur (60), Karachi (60), Mirpur Khas (55), Peshawar (38),  Risalpur (35), Quetta (81), Ziarat (21), Loralai (21), Mastung (37). The results   showed that 19% of the total samples have nitrate concentration beyond the  permissible safe limit of 10 mg/L falling in the concentration  range of 11-160 mg/L  of nitrate. The highest percentage contamination (23%) is found in water samples collected from both the Balochistan and Punjab provinces. Comparatively higher  nitrate levels of <70 % in the groundwater sources like hand pumps and wells  support the possibilities of increased contamination in the areas cultivated using heavy doses of fertilizers. Findings of the study provide support for further  epidemiological investigations and potential strategy for mitigating the issue in theaffected regions.Key words: Nitrate-N, groundwater contamination, hand pumps,   methemoglobinemia, Pollution, nutrients, fertilizer, agriculture

Improved Integrated Risk Assessment of Geogenic Arsenic: Exposure and Attributable Health Risks

The linkage between arsenic contaminated water and increased cancer risk is well recognized. The potential health risk posed by separate inorganic and organic arsenic species through combined exposure to arsenic contaminated water and staple foods is not well understood though. Therefore, this research aims to improve arsenic risk assessment by investigating the primary exposure sources, pathways, metabolism and response indicators in an integrated manner. The population based water and food consumption pattern characterised by this research was used to validate the cancer risk modelling which demonstrated that using water or food intake values from the developed world may not represent cancer risks to the specific population in question. Integrating this characterisation with arsenic species provided several key insights. Arsenate was identified as the main species in the ground water aquifers of five villages whilst the predominance of arsenite and its co-existence with arsenate in one village indicated variations in aquifer redox conditions. Wheat cultivated with arsenic-rich irrigation water proved to be an alternate exposure pathway of inorganic arsenic. The species specific probabilistic cancer and non-cancer risks were found to be higher for arsenite followed by arsenate, whilst no risk was found for dimethylarsinic acid of dietary origin. The comparative impact of various reference doses on chronic health risk substantiated that children are at higher vulnerability, whilst using population based exposure characteristics of this study population and relative risk estimates from southwest Taiwan, showed females to be at higher risk of life time bladder and lung cancer due to inorganic arsenic. No risk was associated with low doses of arsenic. Total ingested arsenic from water or food under the effect of certain potential modifiers was a significant predictor of arsenic species in human biomarkers and proved toenail to be a comparatively effective biomarker. At low arsenic levels in water, food associated total arsenic was a better predictor of urinary metabolites. The total arsenic intake from water and urinary metabolites under the effect of labour jobs strongly predicted the increased risk of arsenical skin lesions. Probabilistic risk modelling indicated that persons with skin lesions were at higher risk of transformation of skin lesions into skin cancer, also evidenced with their lower methylation capability. Overall, this thesis provides evidence that species based risk assessment requires a greater understanding of exposure matrix, toxicological thresholds and metabolic reactions from ingestion to potential endpoints. This study has provided a baseline of inorganic arsenic for risk management to set public health water supply goals and to minimize the daily consumption of cooked rice for compliance with the safe arsenic limit. The findings are suitable to support future regulatory processes for species based arsenic limits in water together with staple foods

Association between inefficient arsenic methylation capacity and demographic characteristics on the risk of skin lesions. Toxicology and Applied Pharmacology.

This study was conducted in rural Pakistan to assess the dose-response relationship between skin lesions and arsenic exposure and their variation by demographic characteristics. The study included 398 participants (66 participants with skin lesions and 332 without) residing in six previously unstudied villages exposed to ground water arsenic in the range of 10 µg L-1 with a daily arsenic intake of 0.78±2.01 mg day-1 from household ground water sources for an exposure duration of 10-20 years. The participants with skin lesions compared to those without skin lesions showed higher levels of urinary iAs (133.40 ± 242.48 vs. 44.24 ± 86.48 μg g-1 Cr), MMA (106.38 ± 135.04 vs. 35.43 ± 39.97 μg g-1 Cr), MMA% (15.26 ± 6.31 vs.12.11 ± 4.68) and lower levels of DMA% (66.99 ± 13.59 vs. 73.39 ± 10.44) and secondary methylation index (SMI) (0.81 ± 0.11 vs. 0.86 ± 0.07). Study participants carrying a lower methylation capacity characterized by higher MMA% (OR 5.06, 95% CI: 2.09-12.27), lower DMA% (OR 0.64, 95% CI: 0.33-1.26), primary methylation index (PMI) (OR 0.56, 95% CI: 0.28-1.12) and SMI (OR 0.43, 95% CI: 0.21-0.88) had a significantly higher risk of skin lesions compared to their corresponding references after adjusting for occupation categories. The findings confirmed that inefficient arsenic methylation capacity was significantly associated with increased skin lesion risks and the effect might be modified by labour intensive occupations

Refinement of arsenic attributable health risks in rural Pakistan using population specific dietary intake values

Background: Previous risk assessment studies have often utilised generic consumption or intake values when evaluating ingestion exposure pathways. If these values do not accurately reflect the country or scenario in question, the resulting risk assessment will not provide a meaningful representation of cancer risks in that particular country/scenario. Objectives: This study sought to determine water and food intake parameters for one region in South Asia, rural Pakistan, and assess the role population specific intake parameters play in cancer risk assessment. Methods: A questionnaire was developed to collect data on sociodemographic features and 24-hour water and food consumption patterns from a rural community. The impact of dietary differences on cancer susceptibility linked to arsenic exposure was evaluated by calculating cancer risks using the data collected in the current study against standard water and food intake levels for the USA, Europe and Asia. A probabilistic cancer risk was performed for each set of intake values of this study. Results: Average daily total water intake based on drinking direct plain water and indirect water from food and beverages was found to be 3.5 L day-1 (95% CI: 3.38, 3.57) exceeding the US Environmental Protection Agency’s default (2.5 L day-1) and World Health Organization’s recommended intake value (2 L day-1). Average daily rice intake (469 g day-1) was found to be lower than in India and Bangladesh whereas wheat intake (402 g day−1) was higher than intake reported for USA, Europe and Asian sub-regions. Consequently, arsenic-associated cumulative cancer risks determined for daily water intake was found to be 17 in children of 3-6 years (95% CI: 0.0014, 0.0017), 14 in children of age 6-16 years (95% CI: 0.001, 0.0011) and 6 in adults of 16-67 years (95% CI: 0.0006, 0.0006) in a population size of 10000. This is higher than the risks estimated using the US Environmental Protection Agency and World Health Organization’s default recommended water intake levels. Rice intake data showed early life cumulative cancer risks of 15 in 10000 for children of 3-6 years (95% CI: 0.0012, 0.0015), 14 in children of 6-16 years (95% CI: 0.0011, 0.0014) and later life risk of 8 in adults (95% CI: 0.0008, 0.0008) in a population of 10000. This is lower than cancer risks in countries with higher rice intake and elevated arsenic levels (Bangladesh and India). Cumulative cancer risk from arsenic exposure showed the relative risk contribution from total water to be51%, from rice to be44% and wheat intake 5%. Conclusions: The study demonstrates the need to use population specific dietary information for risk assessment and risk management studies. Probabilistic risk assessment concluded the importance of dietary intake in estimating cancer risk, along with arsenic concentrations in water or food and age of exposed rural population

Human Health Risk Assessment For Arsenic: A Critical Review

Millions of people are exposed to arsenic resulting in a range of health implications.This paper provides an up-to-date review of the different sources of arsenic (water, soil and food), indicators of human exposure (biomarker assessment of hair, nail, urine and blood), epidemiological and toxicological studies on carcinogenic and non-carcinogenic health outcomes, and risk assessment approaches. The review demonstrates a need for more work evaluating the risks of different arsenic species such as; arsenate, arsenite monomethylarsonic acid, monomethylarsonous acid, dimethylarsinic acid and dimethylarsinous acid as well as a need to better integrate the different exposure sources in risk assessments

The impacts of water pricing and non-pricing policies on sustainable water resources management: a case of Changa Pani water supply scheme in Pakistan

The impacts of water pricing and non-pricing policies on sustainable water resources management: a case of Changa Pani water supply scheme in Pakista

Integrated adsorption-photodegradation of organic pollutants by combined photoactive carbon xerogel/titania adsorbent

Recent studies on the removal of pollutants via adsorption include the use of carbon-based adsorbents, due to their high porosity and large surface area; however, such materials lack photoactive properties. This study evaluates the synergistic effect of integrated mesoporous carbon xerogel (derived from resorcinol formaldehyde) and titanium dioxide (TiO2) for combined adsorption and photodegradation application. The complex formed between carbon xerogel and TiO2 phase was investigated through FTIR, proving the presence of a Ti-O-C chemical linkage. The physicochemical properties of the synthesised adsorbent-photocatalyst were probed using FESEM, BET analysis and UV-Vis analysis. The kinetics, equilibrium adsorption, effect of pH, and effect of adsorbent dosage were investigated. The expansion of the absorbance range to the visible range was verified and the corresponding band gap evaluated. These properties enabled visible light response when the system was exposed to visible light post-adsorption. Hence, an assistive adsorption-photodegradation phenomenon were successfully executed. The adsorption performance exhibited 85% dye degradation and improved to 99% following photodegradation. Further experiments showed the reduction of microorganisms under visible light, where no microbial colonies were observed after treatment, indicating the potential application of these composite materials

Super-Sensitive LC-MS Analyses of Exposure Biomarkers for Multiple Mycotoxins in a Rural Pakistan Population

High levels of mycotoxin contamination have been reported in various food commodities in Pakistan, however, there has been no exposure assessment study using multiple mycotoxins’ biomarkers. This study aimed to simultaneously assess the exposure to the five major mycotoxins: aflatoxin B1 (AFB1), deoxynivalenol (DON), fumonisin B1 (FB1), ochratoxin A (OTA) and zearalenone (ZEN) in a Pakistani population using an integrated approach of human biomonitoring. Human urine samples (n = 292) were analyzed by a super-sensitive liquid-chromatography tandem mass spectrometry (LC-MS/MS) method. Rice and wheat were also collected and analyzed for mycotoxins by the LC-MS/MS method. Food consumption data were collected using a 24 h recall method. A high prevalence of urinary AFM1 (66%, mean ± SD 20.8 ± 41.3 pg/mL) and OTA (99%, 134.7 ± 312.0 pg/mL) were found, whilst urinary DON, FB1 and ZEN levels were low. The probable daily intake (PDI) derived from the urinary biomarkers revealed that 89% of the participants had exposure to OTA exceeding the established tolerable daily intake (TDI = 17 ng/kg bw/day). The average PDI of AFB1 for the studied population was 43 ng/kg bw/day, with rice as the main source of AFB1 exposure. In summary, exposure to AFB1 and OTA are of health concern and require further management

Estimating the health burden of aflatoxin attributable stunting among children in low income countries of Africa

Abstract Numerous population-based studies have documented high prevalence of aflatoxin associated childhood stunting in low income countries. We provide an estimate of the disease burden of aflatoxin related stunting using data from the four African countries. For this empirical analysis, we obtained blood aflatoxin albumin adduct biomarker based exposure data as measured using ELISA technique and anthropometric measurement data from surveys done over a 12-year period from 2001 to 2012 in four low income countries in Africa. We used these data to calculate population attributable risk (PAR), life time disease burden for children under five by comparing two groups of stunted children using both prevalence and incidence-based approaches. We combined prevalence estimates with a disability weight, measuring childhood stunting and co-occurrence of stunting-underweight to produce years lived with disability. Using a previously reported mortality, years of life lost were estimated. We used probabilistic analysis to model these associations to estimate the disability-adjusted life-years (DALYs), and compared these with those given by the Institute for Health Metrics and Evaluation’s Global Burden of Disease (GBD) 2016 study. The PAR increased from 3 to 36% for aflatoxin-related stunting and 14–50% for co-occurrence of stunting and underweight. Using prevalence-based approach, children with aflatoxin related stunting resulted in 48,965.20 (95% uncertainty interval (UI): 45,868.75–52,207.53) DALYs per 100,000 individuals. Children with co-occurrence of stunting and underweight due to exposure to aflatoxin resulted in 40,703.41 (95% UI: 38,041.57–43,517.89) DALYs per 100,000 individuals. Uncertainty analysis revealed that reducing aflatoxin exposure in high exposure areas upto non-detectable levels could save the stunting DALYs up to 50%. The burden of childhood all causes stunting is greater in countries with higher aflatoxin exposure such as Benin. In high exposure areas, these results might help guide research protocols and prioritisation efforts and focus aflatoxin exposure reduction. HEFCE Global Challenge Research Fund Aflatoxin project

Hybrid Beads of Zero Valent Iron Oxide Nanoparticles and Chitosan for Removal of Arsenic in Contaminated Water

Water contaminated with highly hazardous metals including arsenic (As) is one of the major challenges faced by mankind in the present day. To address this pressing issue, hybrid beads were synthesized with various concentrations of zero valent iron oxide nanoparticles, i.e., 20% (FeCh-20), 40% (FeCh-40) and 60% (FeCh-60) impregnated into a polymer of chitosan. These hybrid beads were employed as an adsorbent under the optimized conditions of pH and time to facilitate the efficient removal of hazardous arsenic by adsorption cum reduction processes. X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer- Emmett-Teller BET, a porosity test and wettability analysis were performed to characterize these hybrid beads. The porosity and contact angle of the prepared hybrid beads decreased with an increase in nanoparticle concentration. The effects of various adsorption factors such as adsorbent composition, contact period, pH value and the initial adsorbate concentration were also evaluated to study the performance of these beads for arsenic treatment in contaminated water. FeCh-20, FeCh-40 and FeCh-60 have demonstrated 63%, 81% and 70% removal of arsenic at optimized conditions of pH 7.4 in 10 h, respectively. Higher adsorption of arsenic by FeCh-40 is attributed to its optimal porosity, hydrophilicity and the presence of appropriate nanoparticle contents. The Langmuir adsorption kinetics described the pseudo second order. Thus, the novel beads of FeCh-40 developed in this work are a potent candidate for the treatment of polluted water contaminated with highly toxic arsenic metals.Applied Science, Faculty ofNon UBCEngineering, School of (Okanagan)ReviewedFacultyResearche