Absorption of arsenic from soil and water by two chard (Beta vulgaris L.) varieties: A potential risk to human health

A review on arsenic pollution, toxicity, health risks, and management strategies using nanoremediation approaches

OBJECTIVES

Over 50 countries are affected by arsenic contamination. The problem is becoming worse as the number of affected people increases and new sites are reported globally.

CONTENT

Various human activities have increased arsenic pollution, notably in both terrestrial and aquatic environments. Contamination of our water and soil by arsenic poses a threat to our environment and natural resources. Arsenic poisoning harms several physiological systems and may cause cancer and death. Excessive exposure may cause toxic build-up in human and animal tissues. Arsenic-exposed people had different skin lesion shapes and were vulnerable to extra arsenic-induced illness risks. So far, research shows that varying susceptibility plays a role in arsenic-induced diseases. Several studies have revealed that arsenic is a toxin that reduces metabolic activities. Diverse remediation approaches are being developed to control arsenic in surrounding environments.

SUMMARY AND OUTLOOK

A sustainable clean-up technique (nanoremediation) is required to restore natural equilibrium. More research is therefore required to better understand the biogeochemical processes involved in removing arsenic from soils and waters.

Metabolomic profiling reveals key factors and associated pathways regulating the differential behavior of rice (Oryza sativa L.) genotypes exposed to geogenic arsenic

Arsenic (As) toxicity is an escalating problem; however, information about the metabolic events controlling the varied pattern of As accumulation in rice genotypes within their natural environment is still lacking. The present study is thus an advancement in unravelling the response of such rice genotypes. Soil-water-rice samples were analyzed for As accumulation using ICP-MS. Furthermore, we implemented metabolomics through LC-MS/MS and UHPLC to identify metabolic signatures regulating As content by observing the metalloid's composition in rice agrosystem. Results showed that rice genotypes differed significantly in their levels of metabolites, with Mini mansoori and Pioneer having the highest levels. Mini mansoori contained least As which might have been regulated by Ala, Ser, Glu, Phe, Asn, His, Ile, Lys, Gln, Trp, Tyr, chlorogenic, p-coumaric, trans-ferulic, rutin, morin, naringenin, kampferol, and myricetin, while Asp, Arg, Met, syringic, epigalocatechin, and apigenin contributed to the greater As acclimatization ability of Pioneer. Multivariate tools separated the rice genotypes into two major clusters: Pioneer-Mini mansoori and Damini-Sampoorna-Chintu. KEGG identified three major metabolic pathways (aminoacyl-tRNA, phenylpropanoid, and secondary metabolites biosynthesis route) linked with As tolerance and adaptation mechanisms in rice. Overall, these two genotypes symbolize their As hostile and accommodating attitudes probably due to the accumulated metabolites and the physicochemical attributes of the soil-water. Thus, thorough understanding of the metabolic reactions to As may facilitate the emergence of As tolerant/resilient genotypes. This will aid in the selection of molecular markers to cultivate healthier rice genotypes in As-contaminated areas.

The involvement of hydrogen sulphide in melatonin-induced tolerance to arsenic toxicity in pepper (Capsicum annuum L.) plants by regulating sequestration and subcellular distribution of arsenic, and antioxidant defense system

Melatonin (MT) and hydrogen sulphide (H₂S) are recognised as vital biomolecules actively taking part in plant defence systems as free radical scavengers and antioxidants against a myriad of biotic and abiotic stressors. However, it has been yet unknown in plants subjected to arsenic (As) toxicity whether or not H₂S interacts with MT to regulate endogenous antioxidant defence system. Prior to beginning As stress (As-S) treatments, MT (0.10 mM) was applied externally to plants daily for three days. AsS was then started for two weeks with As(V) (0.1 mM as Na₂HAsO₄·7H₂O). The treatment of As reduced plant biomass (24.4%) and chlorophyll a (51.7%), chlorophyll b (25.9%), while it increased subcellular As in roots and leaves, levels of glutathione (GSH), hydrogen peroxide (H₂O₂), malondialdehyde (MDA), methylglyoxal (MG), H₂S and phytochelatins (PCs) in pepper plants. In As-stressed pepper plants, the application of MT increased plant biomass (16.3%), chlorophyll a (52.7%), chlorophyll b (28.2%), antioxidant enzymes' activities, and H₂S accumulation, while it lowered the concentrations of MDA and H₂O₂. In As-treated plants, GSH and phytochelatins (PCs) were increased by MT by regulating As sequestration to make it harmless. The addition of MT increased As accumulation in the vacuoles of roots and caused the soluble fraction of As in vacuoles to become less toxic to vital organelles. MT-induced tolerance to As stress was further enhanced using NaHS, a source of H₂S. Hypotaurine (0.1 mM HT), a H₂S scavenger, was applied to the control and As-stressed plants together with MT and MT + NaHS to determine whether H₂S was implicated in MT-induced increased As-S tolerance. By reducing H₂S generation in pepper plants, HT counteracted the beneficial effects of MT, whereas the addition of NaHS to MT + HT restored the negative effects of HT, proving that H₂S is necessary for the pepper plants As-stress tolerance caused by MT.

Use of compost in the uptake mitigation of arsenic in Beta vulgaris L. var. cicla

BACKGROUND

Arsenic (As) may represent a risk for crop yield quality and human health since it may accumulate in the edible plant organs with the potential of leading to acute or chronic toxic effects in varied segments of the population. Management of soil fertility through compost has proven to be a valuable practice for increasing and maintaining soil organic matter, with nutritional benefits for crops. This work aimed to evaluate Swiss chard yield and the change in the bioavailability, bioaccumulation, and partitioning of As in the response of the use of compost or conventional mineral fertilization in an open-field trial conducted in a volcanic area in central Italy characterized by the natural contamination of As in soil.

RESULTS

Compost treatment led to a short-term increase trend in soil organic carbon, total nitrogen, and available phosphorus in a significant way. In the compost-amended plots, the mitigation of the As uptake was detected in leaves, which are the edible part of Swiss chard. The As bioaccumulation factor in leaves of Swiss chard and the translocation factor for leaves/roots were also decreased using compost.

CONCLUSION

Fertilization by compost can improve soil fertility, sustain Swiss chard production, and mitigate As accumulation in leaves of this crop grown in a naturally As-contaminated soil. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Arsenic contribution of poultry manure towards soils and food plants contamination and associated cancer risk in Khyber Pakhtunkhwa, Pakistan

Exposure to high level of arsenic (As) through the ingestion of contaminated soil, dust and food plants can pose health risk to humans. This study investigates the total arsenic (As), arsenobetaine (AsB), monomethylarsenate (MMA), dimethylarsenate (DMA), arsenite (As³⁺) and arsenate (As⁵⁺) concentrations in poultry feed, manure, agricultural soils and food plants collected from Khyber Pakhtunkhwa Province, Pakistan. The total mean As concentrations in the edible parts of food plants ranged from 0.096 mg kg^-1 to 1.25 mg kg^-1 with percentile (P) values (P25-0.039, P50-0.0765, P75-0.165 1 mg kg^-1 to P25-0.95, P50-1.23, P75-1.6 1 mg kg^-1) and exceeded the food safety limit (0.1 mg kg^-1) of Food & Agriculture Organization (FAO) and World Health Organization (WHO) in all plant species except Pisum sativum (pea) and Mentha arvensis (mint). The risk to human health was assessed through the average daily intake (ADI), hazards quotient (HQ), health risk index (HRI) and lifetime cancer risk (LTCR). The highest average daily intake of As via the ingestion of Malva neglecta (mallow, a leafy plant) was observed for adults and children. The ADI for adults and children (2.36 × 10^-4 mg kg^-1 day^-1 and 6.33 × 10^-4 mg kg^-1 day^-1) was about 13% and 5%, respectively, of the Bench Mark Dose Limit (BMDL_0.5) of 3.00 × 10^-3 mg kg^-1 day^-1 set by WHO. The HRI was 3 times more in the children (2.1) than the adults (0.79), posing non-cancer health risks (health risk index > 1) for children. The LTCR values were slightly higher (1.53 × 10^-4) relative to USEPA and WHO limits (1 × 10^-6 to 1 × 10^-4) for children whereas a minimal cancer risk was observed for adults via consumption of selected food plants. The results showed that poultry manure can contaminate food plants that may lead to cancer and non-cancer risks in agricultural areas, Pakistan. Thus, it is important to minimize As concentration in poultry feed to safeguard human health and environment from adverse effects.

Growth and biosorption of Purple guinea and Ruzi grasses in arsenic contaminated soils

Increasing mining and industrial discharge of untreated wastewater, as well as excessive use of fertilizers for agricultural purposes, and heavy metal contamination in soil have become one of the serious environmental problems worldwide. In the present study, pot experiments were conducted to evaluate the influence of arsenic contamination and other factors on the growth and development of local forage grasses like Purple guinea and Ruzi grasses under controlled conditions. Influence of arsenic concentration, soil properties, and fertilizers on biosorption and withstanding potential of grasses was studied using model soil and real-time arsenic-contaminated mine soil. High arsenic contents in soil significantly affected the growth as well as biomass production of grasses and declined the overall biomass production concerning exposure durations. Purple guinea and Ruzi grasses showed growth tolerance in arsenic-contaminated soils with concentrations of 100 and 150 mg/kg respectively. Grass species, soil compositions, and properties, fertilizers, growth duration, etc. potentially influenced arsenic accumulation in grasses. Both local forage grasses showed <1 bio-accumulation factor (BAF) and bio-concentration factor (BCF) after 45 days that indicates the minimum harvesting time of 45 days, and biosorption rate was found significant to the exposure duration. Maximum translocation factor (TF) values observed in Purple guinea and Ruzi grasses were 0.65 and 0.95, respectively which are < 1, therefore, these local forage grasses could be labeled as arsenic-metallophytes and ability to tolerate high levels of heavy metals without much biosorption. The results confirmed that local forage grasses have much growth tolerance potential against arsenic in real-time mine soil with desired fertilizers and these species could be used for sustainable management of ecological health of the Thung Kum gold mine area in Thailand.

Human risk associated with the ingestion of artichokes grown in soils irrigated with water contaminated by potentially toxic elements, Junin, Peru

The contamination of water, air and soil with potentially toxic elements (PTE) compromises the supply of contaminant free food. Vegetables grown in contaminated soils can absorb and accumulate PTE at concentrations that are toxic to human health. In this context, the human risk associated with the intake of artichokes grown in soils irrigated with PTE contaminated water was assessed. 120 samples of surface soil and artichoke heads were collected and the concentrations of Cu, Fe, Pb, Zn and As were determined. The results showed that the concentrations of Cu, Fe and Zn in soil did not exceed the standards of the Ministry of Environment of Peru, but they did exceed those of Pb (125.45 mg kg^-1) and As (28.70 mg kg^-1). The decreasing order of mean PTE concentration in artichoke heads was Fe > Zn > Cu > Pb > As, exceeding the permissible levels of FAO/WHO CODEX Alimentarius. However, the concentrations of As comply with the maximum limits of inorganic contaminants in vegetables (0.3 mg kg^-1) established in the MERCOSUR regulations. The non-carcinogenic and carcinogenic risk of Pb and As indicated that the ingestion of artichoke heads does not represent a health risk.

Health risks of arsenic buildup in soil and food crops after wastewater irrigation

Despite considerable research of arsenic (As) level in ground/drinking water of Pakistan, scarce data is available regarding irrigation water contamination by As and associated health risks. The municipal wastewater is routinely applied for soil irrigation in peri-urban agriculture of the country. Since the wastewater composition/contamination and its allied consequences greatly vary in different areas, therefore, it is imperative to check the possible health risks in areas where untreated wastewater is being applied for food crop production. This study analyzed potential health hazards of As-buildup in soil and food plants irrigated with municipal wastewater growing under natural conditions. Sixteen wastewater irrigation locations were selected in District Vehari. From these sites, a total of 16 wastewater samples, 108 soil samples and 65 plant samples were collected for As analysis. Total As contents in wastewater (5.3-63.6 μg/L), soil (1.4-19.6 mg/kg) and plants (0-6.5 mg/kg) greatly varied with sampling location, soil depths and plant type. Based on total As contents in edible tissues, risk assessment parameters, especially cancer risk factor, showed possible health risks (> 0.0001) for wheat crops for children while no risks for other food crops. The use of multiple and diversified food crops is recommended in the study area to minimize the possible risk of As exposure and poisoning. The study also anticipates some future viewpoints considering the on-ground situation of wastewater use, possible exposure of metal(loid)s to human and associated health concerns at local and global scale.

Arsenic accumulation in lettuce (Lactuca sativa L.) and broad bean (Vicia faba L.) crops and its potential risk for human consumption

Exposure to arsenic (As) is considered one of the primary health risks humans face worldwide. This study was conducted to determine As absorption by broad beans and lettuce crops grown in soil with As contents and irrigated with water contaminated with this toxic element, in Pastos Chicos, Jujuy (Argentina). Total dry biomass (TDB) and total As were determined in soils, roots, leaves, pods and seeds. These data were used to determine several parameters, such as translocation (TF) and bioconcentration (BCF) factors, target hazard quotient (THQ), and carcinogenic risk (CR). Broad bean plants had the lowest biomass production when exposed to As in irrigation water and soil. Lettuce plants presented TDB reductions of 33.3 and 42.8% when grown in soil polluted with As, and in control soil under irrigation with contaminated water, respectively. The presence of this toxicant in broad bean seeds and lettuce leaves (edible parts) exceeded the limits established by Código Alimentario Argentino, i.e. 0.10 and 0.30 mg/kg, respectively. THQ values for lettuce leaves were higher than 1, the same as those for broad bean seeds when grown in soil with As contents and irrigated with arsenic-contaminated water, thus suggesting that consumers would run significant risks when consuming these vegetables. Furthermore, this type of exposure to As implied a CR that exceeded the acceptable 1 × 10^-4 risk level. Hence, we may conclude that consuming lettuce and broad beans grown at the evaluated site brings about considerable health risks for local residents.