Evaluating the health risks of potentially toxic elements through wheat consumption in multi-industrial metropolis of Faisalabad, Pakistan

Comparative efficacy of Parthenium hysterophorus (L.) derived biochar and iron doped zinc oxide nanoparticle on heavy metals (HMs) mobility and its uptake by Triticum aestivum (L.) in chromite mining contaminated soils

In this study we investigated the efficacy of a novel material parthenium weed (Parthenium hysterophorus L.) biochar (PBC), iron doped zinc oxide nanoparticles (nFe-ZnO), and biochar modified with nFe-ZnO (Fe-ZnO@BC) to adsorb heavy metals (HMs) and reduce their uptake by wheat (Triticum aestivum L.) in a highly chromite mining contaminated soil. The co-application of the applied soil conditioners exhibited a positive effect on the immobilization and restricted the HMs uptake below their threshold levels in shoot content of wheat. The maximum adsorption capacity was because of large surface area, cation exchange capacity, surface precipitation, and complexation of the soil conditioners. The scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) showed porous smooth structure of parthenium weed derived biochar that helped in HMs adsorption, increase the efficiency of soil fertilizers and nutrients retention which help in the enhancement soil condition. Under different application rates the highest translocation factor (TFHMs) was obtained at 2 g nFe-ZnO rate followed the descending order: Mn > Cr > Cu > Ni > Pb. The overall TFHMs was found <1.0 indicating that low content of HMs accumulation in roots from soil slight transferred to shoot, thus satisfying the remediation requirements.

Ecological and human health risk assessment of heavy metals based on their source apportionment in cropland soils around an e-waste dismantling site, Southeast China

An accurate understanding of soil heavy metal (HM) pollution characteristics and source apportionment, and a recognition of the major factors influencing ecological and human health risks (HHRs) are essential for soil HM pollution control and remediation. In this study, 212 surface soils (0-20 cm) and 15 profile soils (0-100 cm) were collected from cropland soils around an e-waste dismantling site in Taizhou city, Zhejiang Province, China. Spatial analysis was used to evaluate the pollution characteristics of HMs (Cd, Cu, Pb, Zn, Cr and Ni). Principal component analysis (PCA) and positive matrix factorization (PMF) were also conducted to quantify their source contributions. A modified source-oriented HHR assessment integrated source-oriented ecological risk and source-oriented HHR assessment was developed to describe the major factors that influenced HHR. Results showed that 94.81 %, 88.21 %, 36.79 % and 47.17 % of Cd, Cu, Pb and Zn, respectively, in surface soils exceeded their screening values in the soil environmental quality standard for agricultural soils (GB 15618-2018). Spatial analysis indicated that high values of Cd, Cu, Pb and Zn were distributed near the e-waste dismantling site. The results of PCA and PMF showed that the primary sources of HMs in the study area are e-waste dismantling activities, natural sources and atmospheric deposition, which contribute 27 %, 46 % and 27 % of HM pollutants, respectively. The results of source-oriented ecological risk and HHR assessment indicated that e-waste dismantling activities and natural sources were primary sources for ecological risk and HHR. However, source-oriented HHR assessment may underestimate the contribution of e-waste dismantling activities by ignoring HM pollution levels. The modified source-oriented HHR assessment highlights that e-waste dismantling activities were major factor that affect noncarcinogenic risk. This study could provide important data support for subsequent environmental remediation of soil HM pollution in cropland soils around e-waste dismantling sites.

Co-exposure of potentially toxic elements in wheat grains reveals a probabilistic health risk in Southwestern Guizhou, China

Bijie is located at a typical karst landform of Southwestern Guizhou, which presented high geological background values of potentially toxic elements (PTEs). Recently, whether PTE of wheat in Bijie is harmful to human health has aroused people's concern. To this end, the objectives of this study are to determine the concentrations of PTE [chromium (Cr), nickel (Ni), arsenic (As), lead (Pb), cadmium (Cd), and fluorine (F)] in wheat grains, identify contaminant sources, and evaluate the probabilistic risks to human beings. A total of 149 wheat grain samples collected from Bijie in Guizhou were determined using the inductively coupled plasma mass spectrometer (ICP-MS) and fluoride-ion electrode methods. The mean concentrations of Cr, Ni, As, Cd, Pb, and F were 3.250, 0.684, 0.055, 0.149, 0.039, and 4.539 mg/kg, respectively. All investigated PTEs met the standard limits established by the Food and Agriculture Organization except for Cr. For the source identification, Cr and Pb should be originated from industry activities, while Ni, As, and Cd might come from mixed sources, and F was possibly put down to the high geological background value. The non-carcinogenic and carcinogenic health risks were evaluated by the probabilistic approach (Monte Carlo simulation). The mean hazard quotient (HQ) values in the three populations were lower than the safety limit (1.0) with the exception of As (children: 1.03E+00). However, the mean hazard index (HI) values were all higher than 1.0 and followed the order: children (2.57E+00) > adult females (1.29E+00) > adult males (1.12E+00). In addition, the mean carcinogenic risk (CR) values for Cr, As, Pb, and Cd in three populations were all higher than 1E-06, which cannot be negligible. The mean threshold CR (TCR) values were decreased in the order of children (1.32E-02) > adult females (6.61E-03) > adult males (5.81E-03), respectively, all at unacceptable risk levels. Moreover, sensitivity analysis identified concentration factor (C _W ) as the most crucial parameter that affects human health. These findings highlight that co-exposure of PTE in wheat grains revealed a probabilistic human health risk. Corresponding measures should be undertaken for controlling pollution sources and reducing the risks for the local populace.

Pollution characteristics and human health risk assessments of toxic metals and particle pollutants via soil and air using geoinformation in urbanized city of Pakistan

Toxic metals and particle pollutants in urbanized cities have significantly increased over the past few decades mainly due to rapid urbanization and unplanned infrastructure. This research aimed at estimating the concentration of toxic metals and particle pollutants and the associated risks to public health across different land-use settings including commercial area (CA), urban area (UA), residential area (RA), and industrial area (IA). A total of 47 samples for both soil and air were collected from different land-use settings of Faisalabad city in Pakistan. Mean concentrations of toxic metals such as Mn, Zn, Pb, Ni, Cr, Co, and Cd in all land-use settings were 92.68, 4.06, 1.34, 0.16, 0.07, 0.03, and 0.02 mg kg^-1, respectively. Mean values of PM₁₀, PM_2.5, and Mn in all land-use settings were found 5.14, 1.34, and 1.9 times higher than the World Health Organization (WHO) guidelines. Mn was found as the most hazardous metal in terms of pollution load index (PLI) and contamination factor (CF) in the studied area. Health risk analysis for particle pollutants using air quality index (AQI) and geoinformation was found in the range between good to very critical for all the land-use settings. The hazard quotient (HQ) and hazard index (HI) were higher for children in comparison to adults, suggesting that children may be susceptible to potentially higher health risks. However, the cancer risk (CR) value for Pb ingestion (1.21 × 10^-6) in children was lower than the permissible limit (1 × 10^-4 to 1 × 10^-6). Nonetheless, for Cr inhalation, CR value (1.09 × 10^-8) was close to tolerable limits. Our findings can be of valuable assistance toward advancing our understanding of soil and air pollutions concerning public health in different land-use settings of the urbanized cities of Pakistan.

Heavy Metals and Health Risks Associated with Consumption of Herbal Plants Sold in a Major Urban Market in Southwest, Nigeria

BACKGROUND

Although herbal medicines play an important role as a source of medicine, concerns have been raised about the risks posed by consumption of these plants, especially if consumed above permissible levels.

OBJECTIVES

This study was undertaken to assess the level of exposure, toxicity and health risk associated with the consumption of herbal plants in Ado Ekiti urban market, Nigeria.

METHODS

Ten commonly consumed herbal plants sold in Ado Ekiti urban market were subjected to heavy metal analysis. Health risk assessment was carried out to determine the estimated daily intake (EDI) of heavy metals, health risk index (HRI), target hazard quotient for non-carcinogenic risk and estimation of cancer risk (ECR).

RESULTS

The EDIs for lead (Pb), nickel (Ni), chromium (Cr), copper (Cu) and magnesium (Mn) were above the upper tolerable daily intake reference for all studied plant species in both children and adults, an indication that herbal use poses a short-term to long-term health risk to consumers of these herbal products. The EDI for children was significantly lower compared to that of adults, indicating higher risks for adult consumers of these herbal products. The HRI in children for Pb (Alstonia congensis, Terminalia avicennioides, Aframomum melegueta, Cymbopogon citratus and Napoleona vogelii) were greater than 1; HRI in Cu and Mn also showed an unusually high concentration, an indication that long term exposure to the consumption of these herbal plants poses a serious health risk. The HRI in children and adults follows the order Mn > Cu > Ni > Pb > Cr; cadmium (Cd) was not detected in any of the herbal plants. The ECR for Pb, Ni and Cr present in the herbal plants for children ranged between 10-6 (low) to 10-3 (high), while the ECR for Pb, Ni and Cr for herbal plants for adults ranged between 10-5 (acceptable) to 10-2 (unacceptable). For both children and adults, there is a call for concern due to ECRs above the acceptable range; the consumption of these herbal plants poses a long-term cancer risk.

CONCLUSIONS

In both children and adults, ECRs for some of the herbal plants in the present study above the acceptable range present a risk to human health. The consumption of such herbal plants poses a long-term cancer risk.

COMPETING INTERESTS

The authors declare no competing financial interests.

Bioaccumulation and translocation of trace elements in soil-irrigation water-wheat in arid agricultural areas of Xin Jiang, China

Pollution resulting from toxic trace elements is an increasing concern around the world especially in developing countries such as China. Rapid industrialisation, urbanisation and agricultural development are the dominant sources of anthropogenic contamination contributed to an increased potential toxicity of trace elements in the irrigation water-soil-food chain. Xin Jiang in China is a reserved cultivated land development area that could provide the most extensive strategic support for food production and arable land security in China. Thus, it is crucial to investigate the bioaccumulation and translocation of trace elements in order to assess the ecological and human health risks in the traditional oasis system of the agricultural areas in Bay Cheng County, Xin Jiang. This study analysed the levels of trace elements in different layers of the soil, the irrigation water and the wheat plants, and the relationships among them. The results indicated that cadmium (Cd) and chromium (Cr) were the primary pollutants in soils and wheats respectively, and they fell into the serious pollution category. However, no trace elements over the pollution limits were detected in irrigation water. The maximum values of trace elements appeared in the soil layers at 5-10 cm and 10-15 cm. The pollution levels of trace elements in the soil layers were found at 0-5 cm and 0-20 cm, which were higher than those at 20-80 cm. In wheat, high amounts of absorption for Se, Cr, Zn and Cu, but low for Pb were detected in different parts of a plant. The roots of wheats were more eco-toxic to Cd, Co and Pb than other tissues, indicating that roots were more effective at absorbing Cd, Co and Pb, as these metals are usually toxic in the soil. Se, Cu and Zn showed a higher ability of being transferred from soils to the edible parts of crops. The bio-transfer factors of Zn, Mo, Cu, Mg and Mn were considerably higher than those of other elements. The average cancer risk of As, Cd, Co, Ni and TCR in wheat grains exceeded the safety reference limit (1 × 10^-4). For the exposed population, Cr in wheat was the major contributor to total cancer risk. The average values of HQ of Cr, Mn and As, and total non-cancer risk index exceeded the corresponding effective safe reference doses (HQ > 1).

Assessment of Heavy Metals in Agricultural Land: A Literature Review Based on Bibliometric Analysis

A great amount of negative influence on human existence and environmental protection has been brought on by heavy metal pollution in agriculture soil. Thus, major awareness has been diverted to the evaluation of heavy metals (EHM) in agricultural land, which is used to improve the environment and ensure people’s health. Based on 3759 publications collected from the Web of Science Core CollectionTM (WoS), this paper’s aim is to illustrate a comprehensive bibliometric run-through and visualization of the subject of EHM. Contingent on influential authors, top institutions, keywords are discussed in detail. Afterwards, the ruling publications and focal assemblage of EHM and leading publications are analyzed to discover the main research topics, according to citation analysis and reference co-citation analysis. The main motive of the paper is to assist research workers interested in the area of EHM determine the ongoing potential research opportunities and hotspots.

Descriptive Analysis of Heavy Metals Content of Beef From Eastern Uganda and Their Safety for Public Consumption

In this study, we initiated an effort to generate information about beef safety in Uganda. Our entry point was to assess by atomic absorption spectrophotometry the levels of essential elements copper (Cu), cobalt (Co), iron (Fe) and zinc (Zn), and non-essential elements lead (Pb), chromium (Cr), nickel (Ni), and cadmium (Cd) in 40 beef samples collected from within and around Soroti (Uganda). The information was used to evaluate the safety of consuming such beef against the World Health Organization (WHO) limits. The latter was accomplished by (i) estimating the daily intake (EDI) of each metal in the study area, (ii) modeling the non-cancer health risk using the target hazard quotient (THQ) and (iii) modeling the cancer risk using the incremental lifetime cancer risk (ILCR). The study finds that the mean concentrations (±95% CI) and EDI were in the order of Fe > Zn > Cr > Ni > Pb > Co > Cu > Cd. Cancer risk was found to be due to Ni > Cr > Cd > Pb and significantly higher in children than adults. The latter particularly demonstrates the importance of Ni poisoning in the study area. Overall, while essential elements in our beef samples were below WHO limits (hence no health risks), non-essential elements had high health and cancer risks due to higher levels of Cr and Ni.

Cadmium, chromium, nickel and nitrate accumulation in wheat (Triticum aestivum L.) using wastewater irrigation and health risks assessment

The wastewater utilization for irrigation purposes is common practice in peri-urban areas located in vicinity of developed cities. This water contains elements like chromium (Cr), nickel (Ni), cadmium (Cd) and nitrate (NO₃-N) that poses health risk when exposed to human. In this study effect of wastewater irrigation from Chakara wastewater plant, Faisalabad on growth of wheat and health risks was assessed. Pot experiment was conducted at Institute of Soil and Environmental, University of Agriculture, Faisalabad using different concentration of wastewater as treatment 100% tap water, 25% wastewater + 75% tap water, 50% wastewater + 50% tap water, 75% wastewater + 25% tap water, 100% wastewater. The results indicated that the wastewater irrigation negatively effects the plant growth and physiological parameters. The minimum plant height, grain weight, spike length, osmotic potential and SPAD values were recorded 50.33 cm, 1.47 g plant^-1, 7.00 cm, 423 and 38.91 respectively in 100% wastewater irrigation. The risk quotient (RQ _TEs) for each toxic element and cumulative risk index (RI _TEs) values were calculated. The cadmium risk quotient (Cd _RQ) for adults was on margin and value was >1 for in 75% wastewater + 25% tap water and 100% wastewater irrigation, while the RQ for Ni and Cr was <1. Maximum RI _TEs values calculated in 100% wastewater irrigation 0.424 and 0.294 for children and adults respectively. Hence it was concluded that wastewater irrigation significantly increased the accumulation rate of metals and nitrate in wheat and cause potential health risks for children and adults.

Remediation of organophosphorus pesticide polluted soil using persulfate oxidation activated by microwave

Contaminated sites from pesticide industry have attracted global concern due to the characteristics of organic pollution with high concentrations and complete loss of habitat conditions. Remediation of organophosphorus pesticide polluted soil using microwave-activated persulfate (MW/PS) oxidation was investigated in this study, with parathion as the representative pesticide. Approximately 90 % of parathion was degraded after 90 min of MW/PS oxidation treatment, which was superior to those by single PS or MW treatment. Relatively greater performances for parathion degradation were obtained in a relatively larger PS dosage, higher microwave temperature, and lower organic matter content. Appropriate soil moisture favored parathion degradation in soil. SO₄^-, OH, O₂^-, and ¹O₂ generated in the MW/PS system all contributed to parathion degradation. Multiple spectroscopy analyses indicated that PO and PS bonds in parathion were destroyed after MW/PS oxidation, accompanied by generation of hydroxylated and carbonylated byproducts. The soil safety after parathion degradation was assessed via model prediction. Furthermore, MW/PS oxidation also exhibited great performance for degradation of other organophosphorus pesticides, including ethion, phorate, and terbufos.

Lead, Zinc and Cadmium Accumulation, and Associated Health Risks, in Maize Grown near the Kabwe Mine in Zambia in Response to Organic and Inorganic Soil Amendments

Health risks due to heavy metal (HM) contamination is of global concern. Despite concerns of high levels of HMs in soils near Kabwe mine in Zambia, edible crop production is common, posing potential health risks. This study assessed the potential of chicken manure (CM), triple superphosphate (TSP) and a blended fertilizer (BF; consisting of Nitrogen, Phosphorous and Potassium (NPK) fertilizer and composted chicken manure) to reduce lead (Pb), zinc (Zn) and cadmium (Cd) in soils and their accumulation in maize grown near the Kabwe mine. Maize was grown to maturity and its HM concentrations and associated health risk indices were calculated. All soil amendments decreased bioavailable soil Pb concentrations by 29–36%, but only CM decreased Zn, while the amendments increased or had no effect on Cd concentrations compared to the control. The amendments reduced Pb (>25%) and Zn concentrations (>18%) in the maize stover and grain. However, Cd concentrations in maize grain increased in the BF and TSP treatments. Bioaccumulation factors showed that Cd had the highest mobility from the soil into maize stover and grain, indicating the need for greater attention on Cd in Kabwe despite its apparently lower soil concentration compared to Pb and Zn. The hazard quotients for Pb and Cd were much greater than one, indicating a high risk of possible exposure to toxic levels by people consuming maize grain grown in this area. This study demonstrated the significant potential of manure and phosphate-based amendments to reduce Pb and Zn, and to some extent Cd, uptake in maize grain and consequently reduce associated health risks.

Sources, Enrichment, and Geochemical Fractions of Soil Trace Metals in Ulaanbaatar, Mongolia

Mongolia is a rapidly developing country that has experienced growing industrialization and urbanization in recent decades. This study was conducted to evaluate the enrichment and labile fractions of metals in urban soils of Mongolia and to identify major sources of soil metal pollution. The concentrations and geochemical fractions of Al, Fe, Mn, Cr, Cu, Cd, Co, Zn, V, Mo, As, Sb, and Pb in soils of the city Ulaanbaatar were investigated. The results demonstrate that only Fe, Mn, Co, Mo, and V occur at natural levels with enrichment factors close to unity. The majority of investigated toxic metals, including Cu, Zn, Cr, Sb, As, Cd, and Pb, are serious pollutants in urban soils, with enrichment factors of up to 2.8, 5.1, 2.1, 16, 13, 15, and 11, respectively. Studies of the chemical fractions of metals demonstrate that Zn is mainly found in its labile form and is considered a high risk to humans and biota. Industrial release, household ash, coal combustion, and tire abrasion were identified as key sources of toxic metals entering into the soil of Ulaanbaatar City, which should be controlled effectively to prevent the population as well as pollution distribution over a wider area by long-range atmospheric transport.

Chemical fractionation and bioaccessibility of potentially toxic elements in area of artisanal gold mining in the Amazon

Artisanal mining may have modified the mobility, bioavailability and bioaccessibility of potentially toxic elements (PTEs) in the Serra Pelada gold mine, eastern Amazon, Brazil, which has not yet been studied. The objectives were to perform chemical fractionation of barium (Ba), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn), and to determine the bioaccessibility of these elements in soils and mining wastes collected in agriculture, forest, mining, and urban areas from the influence zone of the Serra Pelada gold mine. Pseudo total concentrations were obtained by acid digestion, chemical fractionation was performed using the Bureau Community of Reference (BCR) sequential extraction, oral bioaccessibility was obtained by the Simple Bioaccessibility Extraction Test (SBET) and lung bioaccessibility was obtained through Gamble's solution. The pseudo total concentrations indicated contamination by Ba, Cu and Ni. The sequential extraction revealed the predominance of all elements in the residual fraction. However, Ba is in high concentrations in the greater mobility forms, ranging from 166.36 to 1379.58 mg kg^-1. Regardless of the area, Cr and Cu are more oral bioaccessible in the intestinal phase, and Zn in the gastric phase. Ba, Cr and Zn are not lung bioaccessible, while Cu, Ni and Pb are bioaccessible via inhalation. The PTEs studied deserve attention not only due to the high pseudo total concentrations found (which indicate potential risk), but also the concentrations in high mobility forms and bioaccessible fractions, especially in the areas of greatest anthropogenic occupation.

Consumption of Raw Herbal Medicines Is Associated with Major Public Health Risks amongst Ugandans

Background

Community consumption of herbal plants in developing countries is a common practice, however, scarcity of information on their physiochemical composition is a major public health concern. In Uganda, Vernonia amygdalina is of interest in rural communities due to its therapeutical action on both bacterial and protozoal parasites, however no studies have been conducted to assess the heavy metal concentrations in traditional plants used in alternative medicine. The aim of the study was to establish concentrations of heavy metals in Vernonia amygdalina, model the estimated daily intake (EDI), and assess both the non-cancer-related health risk using the target hazard quotient (THQ), and the risk related to cancer through the incremental lifetime cancer risk (ILCR) for the Ugandan population.

Methods

Leaves of Vernonia amygdalina were collected from 20 georeferenced villages and processed into powder in the laboratory using standard methods. These were then analyzed in the laboratory using an atomic absorption spectrometer for lead (Pb), chromium (Cr), copper (Cu), zinc (Zn), cobalt (Co), iron (Fe), cadmium (Cd), and nickel (Ni). Concentrations were compared against the World Health Organization (WHO) limits. The EDI, THQ, and ILCR were modelled and significance was measured at 95% confidence.

Results

The study showed that mean ± SEM concentrations of heavy metals were highest in the order of Cr, 121.8 ± 4.291 ppm > Ni, 84.09 ± 2.725 ppm > Zn, 53.87 ± 2.277 ppm > Pb, 40.61 ± 3.891 ppm > Cu, 28.75 ± 2.202 ppm > Fe, 14.15 ± 0.7271 ppm > Co, 7.923 ± 0.7674 ppm > Cd, 0.1163 ± 0.005714 ppm. Concentrations of Pb, Cr, Zn, Co, and Ni were significantly higher than the WHO limits. The EDI was significantly higher in children than in adults, demonstrating an increased risk of toxicity in children. The THQ and ILCR were over 1000 times higher in all Ugandans, demonstrating the undesirable health risks following oral consumption of Vernonia amygdalina due to very high Cr and Ni toxicities, respectively.

Conclusion

Consumption of raw Vernonia amygdalina was associated with a high carcinogenic risk, demonstrating a need to enact policies to promote physiochemical screening of herbal medicines used in developing countries against toxic compounds.

Public health risk of toxic metal(loid) pollution to the population living near an abandoned small-scale polymetallic mine

Small-scale mining activities in many developing countries have caused severe environmental issues to the surrounding areas, which ultimately threatened the health of local populations. Based on detailed characterization of the local drinking water and surface soil, as well as foodstuffs, this study comprehensively assessed the public health risk of toxic metal(loid)s to the population living in three villages surrounding an abandoned small-scale polymetallic mine in southern China. The agricultural soils contained elevated levels of Cu, Zn, As, Cd, and Pb, which originated from the mining district, and as expected, the locally cultivated rice and vegetables were contaminated by As, Cd, and Pb to varying extents. Arsenic occurred in both inorganic and organic forms in the rice and vegetables, with inorganic As (i-As) accounting for 82.2% (45.4-100%) and 94.7% (65.2-100%) of the total As contents in rice and vegetables, respectively. Results of health risk assessment indicate that the residents in the impacted villages had serious non-carcinogenic and carcinogenic risk. Dietary exposure to i-As and Cd through rice and vegetable consumption was the primary cause of non-carcinogenic risk, while i-As intake was the dominant contributor of carcinogenic risk. These findings suggest that significant environmental pollution by toxic metal(loid)s could result from small-scale metal mines, even after being abandoned, and the accumulation of the toxic metal(loid)s in food crops could pose significant health risk to the local residents. Immediate actions should be taken to discourage them from consuming the locally produced food crops, while long-term control measures for containment of toxic metal(loid) pollution are being developed, and high priority should be given to the remediation of Cd and As in the contaminated soils.

Biochar-induced immobilization and transformation of silver-nanoparticles affect growth, intracellular-radicles generation and nutrients assimilation by reducing oxidative stress in maize

Silver nanoparticles (AgNPs) are used in a wide range of consumer products inevitably releases in massive quantities in the natural environment, posing a potential thread to ecosystem-safety and plant health. Here, the impact of AgNPs (100-1000 mg L^-1) without and with biochar (@2 % w/v) amendment on maize plants was assessed in hydroponics exposure medium. AgNPs exposure to plants induced dose-dependent phytotoxicity by suppressing plant growth, disturbing photosynthesis and gas exchange traits and alteration in macro- and micronutrients assimilation. At the same time, AgNPs with addition of biochar alleviated the phyto-toxic effects of AgNPs through approximately 4-8 times reduction in uptake and tissue accumulation of Ag. Moreover, activities of antioxidant enzymes in AgNPs + biochar treated plants indicated the lower oxidative stress. Electron paramagnetic resonance (EPR) spectroscopy confirmed that superoxide (O₂^-) radical was the dominant reactive oxygen species. Fourier-transform infrared spectroscopic (FTIR) and X-ray photoelectron spectroscopic (XPS) results revealed that biochar surface carboxyl and sulfur functional groups were involved in complexation process with NPs, which inhibited the oxidative dissolution and release of Ag⁺ ions besides of biochar space shield effect. Thus, the interaction of biochar with AgNPs immobilizes these NPs and can effectively reduce their bioavailability in the environmental matrix.

Treated wastewater used in fresh produce irrigation in Nsukka, Southeast Nigeria is a reservoir of enterotoxigenic and multidrug-resistant Escherichia coli

Background

Occurrences of pathogens in environmental and irrigation waters, as well as the use of inadequately treated sewage for fresh produce constitute potential public health threats worldwide.

Objective

To investigate the treated wastewater used in fresh produce irrigation in Nsuskka, Southeastern Nigeria, as a reservoir enterotoxigenic and multidrug-resistant Escherichia coli.

Methods

Treated wastewater (from the sewage treatment facility at Nsukka, Southeast Nigeria), soil and irrigated vegetable samples were collected and analyzed using standard procedures. Escherichia coli isolated from the samples were screened for the presence of enterotoxigenic E. coli strain encoding lt gene and profiled for antibiotic resistance using the conventional PCR and standardized agar disk diffusion assays respectively.

Results

Of the total presumptive 103 isolates, PCR detected uidA gene in 87 (84 %), of which 23 (26 %) harboured the lt encoding ETEC gene. Generally, imipenem, cefuroxime and norfloxacin proved to be most effective of all the antibiotics employed. Wastewater isolates were variously susceptible to ciprofloxacin (95 %), norfloxacin (95 %), cefuroxime (93 %), chloramphenicol (93 %), trimethoprim and tetracycline (88 %), soil isolates to streptomycin (75 %) and vegetable isolates to cefuroxime (90 %), norfloxacin (86 %), ciprofloxacin (81 %) and chloramphenicol. Contrariwise, high resistances observed to other antibiotics were in the order; ampicillin (95 %), penicillin (93 %), erythromycin (90 %) and clarithromycin (83 %) among wastewater isolates, ciprofloxacin and norfloxacin (75 %) in soil isolates; penicillin, vancomycin and erythromycin (98 %), rifampicin and clarithromycin (93 %), sulphamethoxazole (83 %), ampicillin (81 %), tetracycline and imipenem (76 %), trimethoprim (72 %) and amoxicillin (71 %) among vegetable isolates, with multidrug resistance patterns ranging from three to seventeen.

Conclusions

Our results reveal the treated wastewater as a reservoir of enterotoxigenic E. coli as well as multidrug resistance that may pose a health hazard for humans and animals when released to the natural environment. Hence, there is need to develop management strategies and ensure compliance in order to prevent water-borne diarrhoea caused by ETEC and reduce the menace of antibiotic resistance in the environment.

Estimating the pollution characteristics and health risks of potentially toxic metal(loid)s in urban-industrial soils in the Indus basin, Pakistan

The Indus Basin Irrigation Network (IBIN) plays a vital role in the agricultural system of Pakistan, irrigating seventeen million hectares of cultivated areas. Rapid urbanization, industrialization, and agricultural activities along the Indus basin have influenced the soil quality and human health; it is, therefore, critical to know its pollution characteristics. Soil samples from Indus basin, i.e., Abbottabad (ABT), Haripur (HRP), Attock (ATC), and Islamabad (ISB) have been analyzed for the total contents of potentially toxic metal(loid)s (PTMs) in the top layer. The topsoil samples from 0 to 10 cm depth have been further investigated using different pollution indices and human health risk assessment models. The contamination degree of soil pollution was highest in ISB (33.75), followed by ABT (25.30) and ATC (23.57). The assessment of the daily intake of PTMs by children and adults through different pathways revealed ingestion as the significant exposure pathway. Cr was found to be the major element posing non-carcinogenic health risks to children at ATC whereas the non-carcinogenic risks posed by all other PTMs were within the safe limit. Furthermore, life-time carcinogenic risks for Ni followed by Cr and Cd were greatly exceeded at all locations and As at ATC and ISB for both age groups, but comparatively children were found to be at a higher risk of carcinogenicity. Hence, efficient remediation strategies are needed to reduce the increasing content and health risks of PTMs in the Indus basin.

Investigating the drinking and surface water quality and associated health risks in a semi-arid multi-industrial metropolis (Faisalabad), Pakistan

Urban areas under the influence of multi-industrial activities with arid and semi-arid environments witness the significant increase in environmental pollution especially in the water sector. The present study evaluated the water quality and associated health risk assessment through heavy metal pollution. Drinking (n = 48) and surface (n = 37) water samples were collected from semi-arid multi-industrial metropolis, Faisalabad, Pakistan. Physio-chemical and biological parameters and different metals (Al, As, Ba, Cd, Cr, Cu, Fe, Pb, Ni and Zn) were investigated using standard procedures and multivariate water quality assessments. Many physio-chemical and biological parameters and metals especially arsenic were exceeding the permissible limit of Punjab environmental quality standards and the World Health Organization. The results from water quality index showed that < 56% samples have poor, < 8% have very poor and < 6% have unsuitable water quality for drinking purposes. Water quality for the Gugera Branch Canal was found suitable with medium sodium (alkalinity) and salinity hazards, while it was found poor with magnesium absorption ratio. Hazard quotient (HQ) values for arsenic were found at the threshold level (HQ > 1) and carcinogenicity was found in case of arsenic and chromium (1 × 10^-4) in adults and children. Semi-arid weather combined with different anthropogenic activities and unusual water features provoked metal contamination. Results of the present study can deliver basic information for effective management of water in the most populous and industrial areas.

Effects of biochar on uptake, acquisition and translocation of silver nanoparticles in rice (Oryza sativa L.) in relation to growth, photosynthetic traits and nutrients displacement

Rapid development in nanotechnology and incorporation of silver nanoparticles (AgNPs) in wide range of consumer products causing the considerable release of these NPs in the environment, leading concerns for ecosystem safety and plant health. In this study, rice (Oryza sativa) was exposed to AgNPs (0, 100, 200, 500 and 1000 mg L^-1) in biochar amended (2 %w/v) and un-amended systems. Exposure of plants to AgNPs alone reduced the root and shoot length, biomass production, chlorophyll contents, photosynthesis related physiological parameters as well as macro-and micronutrients in a dose dependent manner. However, in case of biochar amendment, physiological parameters i.e., net photosynthesis rate, maximum photosynthesis rate, CO₂ assimilation, dark respiration and stomatal conductance reduced only 16, 6, 7, 3 and 8%, respectively under AgNPs exposure at 1000 mg L^-1 dose. Meanwhile, biochar at all exposure level of AgNPs decreased the bioaccumulation of Ag in rice root and shoot tissues, thus alleviated the phyto-toxic effects of NPs on plant growth. Moreover, results showed that biochar reduced the bioavailability of AgNPs by surface complexation, suppressing dissolution and release of toxic Ag⁺ ions in the growth medium. The presence of biochar at least decreased 2-fold tissue contents of Ag even at highest AgNPs (1000 mg L^-1) concentration. These finding suggested that biochar derived from waste biomass resources can be used effectively to prevent the bioaccumulation and subsequent trophic level transfer of emerging Ag nano-pollutant in the environment.

Difference of trace element exposed routes and their health risks between agriculture and pastoral areas in Bay County Xinjiang, China

The concentration level related to toxicities of trace elements in drinking water, rice, wheat flour, and their associated negative impacts on human health have become an emergent issue in China. Because Xinjiang is the largest province in China with the majority of arable pasture land available for cultivation, it is important to analyze the concentrations of trace elements in relation to their toxicities in water, rice, and wheat flour and to investigate the health risk differences between agricultural and pastoral areas in Bay County, Xinjiang. The study results showed that (1) metal concentrations from drinking water, rice, and wheat flour were within the permissible limits; (2) concentration levels of trace elements and their total risk from drinking water and rice were higher in the agricultural areas than those in the pastoral areas, whereas concentration levels of trace elements and their total risk from wheat flour were higher in the pastoral areas than those in the agricultural areas; (3) the concentration level of the trace elements in rice were higher than in the wheat flour, but the risk from the wheat flour was higher than the risk from rice; (4) total non-cancer risk from the flour (HI_f) in both areas exceeded the respective safe reference doses; (5) total cancer risk from the wheat flour, rice, and water exceeded the safety limit (1 × 10^-4); (6) for the exposed population, arsenic was suggested as the most evident pollutant leading to carcinogenic concerns regarding the water, rice, and wheat flour; (7) the risk index from the wheat flour made up the highest percentage both in the total cancer risk and the non-cancer risk, followed by rice and then water; and (8) the human health risk was attributed to influence from the local environment in the agriculture areas, while it was attributed to the external environment in the pastoral areas. Graphical abstract.