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

Staphylococcus arlettae mediated defense mechanisms and metabolite modulation against arsenic stress in Helianthus annuus

Introduction

Arsenate, a metalloid, acting as an analog to phosphate, has a tendency to accumulate more readily in plant species, leading to adverse effects.

Methods

In the current study, sunflower seedlings were exposed to 25, 50 and 100 ppm of the arsenic.

Results

Likewise, a notable reduction (p<0.05) was observed in the relative growth rate (RGR) by 4-folds and net assimilation rate (NAR) by 75% of Helianthus annuus when subjected to arsenic (As) stress. Nevertheless, the presence of Staphylococcus arlettae, a plant growth-promoting rhizobacterium with As tolerance, yielded an escalation in the growth of H. annuus within As-contaminated media. S. arlettae facilitated the conversion of As into a form accessible to plants, thereby, increasing its uptake and subsequent accumulation in plant tissues. S. arlettae encouraged the enzymatic antioxidant systems (Superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX) and catalase (CAT)) and non-enzymatic antioxidants (flavonoids, phenolics, and glutathione) in H. annuus seedlings following substantial As accumulation. The strain also induced the host plant to produce osmolytes like proline and sugars, mitigating water loss and maintaining cellular osmotic balance under As-induced stress. S. arlettae rectified imbalances in lignin content, reduced high malonaldehyde (MDA) levels, and minimized electrolyte leakage, thus counteracting the toxic impacts of the metal.

Conclusion

The strain exhibited the capability to concurrently encourage plant growth and remediate Ascontaminated growth media through 2-folds rate of biotransformation and bio-mobilization.

Interactive impacts of microplastics and arsenic on agricultural soil and plant traits

The ability of microplastics (MPs) to interact with environmental pollutants is currently of great concern due to the increasing use of plastic. Agricultural soils are sinks for multipollutants and the safety of biodegradable MPs in field conditions is questioned. However, still few studies have investigated the interactive effects between MPs and metals on the soil-plant system with agricultural soil and testing crops for human consumption. In this work, we tested the effect on soil and plant parameters of two common MPs, non-degradable plastic low-density polyethylene and biodegradable polymer polylactic acid at two different sizes (<250 μm and 250-300 μm) in association with arsenic (As). Lettuce (Lactuca sativa L.) was used as a model plant in a small-scale experiment lasting 60 days. Microplastics and As explained 12 % and 47 % of total variance, respectively, while their interaction explained 21 %, suggesting a higher toxic impact of As than MPs. Plant growth was promoted by MPs alone, especially when biodegradable MPs were added (+22 %). However, MPs did not affect nutrient concentrations in roots and leaves. The effect of MPs on enzyme activities was variable depending on the time of exposure (with larger effects immediately after exposure), the type and size of the MPs. On the contrary, the co-application of MP and As, although it did not change the amount of bioavailable As in soil in the short and medium term, it resulted in a significant decrease in lettuce biomass (-19 %) and root nutrient concentrations, especially when polylactic acid was applied. Generally, MPs in association with As determined the plant-soil toxicity. This work provides insights into the risk of copollution of MPs and As in agricultural soil and its phytotoxic effect for agricultural crops. However, the mechanisms of the joint effect of MP and As on plant toxicity need further investigation, especially under field conditions and in long-term experiments.

Arsenic uptake and accumulation in bean and lettuce plants at different developmental stages

The pattern of arsenic (As) uptake at different developmental stages in plants and its consequent influence on the growth of plants was investigated in bean and lettuce. Further, the human health risk from the consumption of these As-laced vegetables was determined. The irrigation water was contaminated with As at concentrations of 0.1, 0.25, and 0.5 mg/L. The As concentration in the plant parts (root, stem, leaves, and flower/fruit) was determined in bean at the young, flowering, and fruiting stages and lettuce at the young and mature stages. At the different growth stages, As had an impact on the biomass of bean and lettuce plant parts, but none of the biomass changes were significant (p>0.05). The increase in As concentration of the irrigation water elevated the As concentration of plant parts of both plants at all growth stages, with the exception of the bean fruit. The As concentration in the developmental stages was in the order: lettuce (young>mature) and bean (fruiting>young>flowering). In lettuce, the transfer factor was higher at the young stage (0.09-0.19, in the control and 0.1 mg/L As treatment), while in bean, it was highest at the flowering stage (0.09-0.41, in all treatments). In the edible part, lettuce possessed substantially elevated As concentrations (0.30, 0.61, and 1.21 mg/kg DW) compared to bean (0.008, 0.005, and 0.022 mg/kg DW) at As treatments of 0.1, 0.25, and 0.5 mg/L, respectively, and posed significant health risks at all applied As concentrations.

Toxic Elements in Beans from Zhejiang, Southeast China: Distribution and Probabilistic Health Risk Assessment

This study described the distribution of As, Cd, Cr, Hg, and Pb in 692 bean samples from Zhejiang province, southeast China, and estimated the health risk using Monte Carlo simulation. The average levels of As, Cd, Cr, Hg, and Pb were 0.0349, 0.0379, 0.246, 0.0019, and 0.0246 mg kg-1. Correlation analyses showed very strong positive correlations for Cd-Pb in kidney beans and mung beans, Cd-As in black beans, and Pb-As in red beans. The target hazard quotients (THQs) were adopted for non-carcinogenic risk assessment, and THQs at the 50th percentile were all less than 1, indicating that there are no deleterious effects from rice exposure to these elements. When evaluating THQ for multiple elements, the certainty with a hazard index (HI) greater than 1 for children was 12.64%, for teens 11.54%, and for adults 1.01%. The sensitivity analysis reveals that the concentration of Cd in beans and ED (exposure duration) are the main principal factors that contributed to the total risk. The mean carcinogenic risks for children, teens, and adults were all less than 1 × 10-4, indicating no potential carcinogenic risk. Despite that, the routine monitoring of these elements, especially for Cd should be continued.

The Effect of Functionalized Multiwall Carbon Nanotubes with Fe and Mn Oxides on Lactuca sativa L

The aim of this work was to evaluate the effect of six nanomaterials, namely CNT-COOH, CNT-MnO2, CNT-Fe3O4, CNT-MnO2-Fe3O4, MnO2, and Fe3O4 on lettuceTo determine the impact of nanomaterials on lettuce, the results obtained were compared with those for the control plant, grown in the same conditions of light, temperature, and humidity but without the addition of nanomaterial. The study found that the content of bioactive compounds and the antioxidant capacity varied in the treated plants compared to the control ones, depending on the nanomaterial. The use of CNTs functionalized with metal oxides increases the elemental concentration of lettuce leaves for the majority of the elements. On the contrary, metal oxide nanoparticles and CNT functionalized with carboxyl groups induce a decrease in the concentration of many elements. Soil amending with MnO2 affects the content of more than ten elements in leaves. Simultaneous application of CNT and MnO2 stimulates the elemental translocation of all elements from roots to leaves, but the simultaneous use of CNT and Fe3O4 leads to the most intense translocation compared to the control other than Mo.

Endofungal Rhizobium species enhance arsenic tolerance in colonized host plant under arsenic stress

Arsenic (As) is a toxic metalloid that is present in natural surroundings in many forms with severe consequences to sustainable agriculture and human health. Plant growth-promoting Rhizobia have been found involved in the induction of plant tolerance under various biotic and abiotic stresses. An endofungal Rhizobium species associated with arbuscular mycorrhizal fungi (AMF) Serendipita indica deploy beneficial role in the promotion of plant growth and tolerance against various biotic and abiotic stresses. In the current study, we have determined the role of endofungal Rhizobium species in protection of host plant growth under As stress. We observed that endofungal Rhizobium species strain Si001 tolerate AsV up to 25 mM and its inoculation enhances tomato seed germination and seedling growth. A hyper-colonization of Rhizobium species Si001 in tomato roots was observed under As stress and results in modulation of GSH and proline content with reduced ROS. Rhizobium species Si001 colonization in host plant recovered pigment contents (chlorophyll-a and chlorophyll-b up to 189.5% and 192%, respectively), photosynthesis (157%), and water use efficiency (166%) compared to As-treated plants. Interestingly, bacterial colonization results in 40% increased As accumulation in the root, while a reduction in As translocation from root to shoot up to 89% was observed as compared to As treated plants. In conclusion, endofungal Rhizobium species Si001 association with the host plant may improve plant health and tolerance against As stress with reduced As accumulation in the crop produce.

Additive and Interactive Associations of Environmental and Sociodemographic Factors with the Genotypes of Three Glutathione S-Transferase Genes in Relation to the Blood Arsenic Concentrations of Children in Jamaica

Arsenic (As) is a metalloid that has been classified as a xenobiotic with toxic effects on human beings, especially on children. Since the soil in Jamaica contains As, dietary intake is considered the main source of As exposure in Jamaicans. In addition, glutathione S-transferase (GST) genes, including GSTT1, GSTP1, and GSTM1, play an important role in the metabolism of xenobiotics including As in humans. Using data from 375 typically developing children (2–8 years) in Jamaica, we investigated the environmental and sociodemographic factors, as well as their possible interactions with the children’s genotype for GST genes in relation to having a detectable level of blood As concentration (i.e., >1.3 μg/L). Using multivariable logistic regression, we have identified environmental factors significantly associated with blood As concentrations that include a child’s age, parental education levels, and the consumption of saltwater fish, cabbage, broad beans, and avocado (all p < 0.01). Based on the multivariable analysis including gene x environment interactions, we found that among children with the Ile/Ile genotype for GSTP1 Ile105Val, children who consumed avocado had higher odds of having a detectable blood As concentration compared to children who did not eat avocado.

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.

Heavy metals in soils and edible tissues of Lepidium meyenii (maca) and health risk assessment in areas influenced by mining activity in the Central region of Peru

Heavy metal contamination of soil and agricultural products is an environmental problem, has an adverse effect on the quality of food crops, and is a danger to food security and public health. The concentration of arsenic (As), cadmium (Cd), lead (Pb), iron (Fe) and zinc (Zn) in surface soils and edible hypocotyls tissues of two ecotypes of Lepidium meyenii Walpers (maca) was evaluated in three districts of the Junín province, Peru. In addition, the risk to human health due to exposure to heavy metals from maca consumption was evaluated. Soil samples and maca hypocotyls were collected in areas influenced by mining and metallurgical activity. The mean concentration of Cd (0.32 ± 0.23 mg/kg) and Pb (0.20 ± 0.12 mg/kg) in maca samples exceeded the values established by the Food and Agriculture Organization and the World Health Organization. The bioconcentration factor was less than 1. The estimated daily intake of each metal was below the oral reference dose. The hazard quotient and hazard index were less than 1, it is unlikely to cause non-cancer adverse health outcome. The cancer risk for As and Cd was higher than the tolerable limit (1 × 10-6) in children and adults. In the district of Ondores, the cancer risk for As in children was higher than the acceptable limit (1 × 10-4). Residents of the Ondores district would be more exposed to As and Cd from consumption of maca hypocotyls. It is very important to carry out continuous monitoring of other toxic metals in different ecotypes of maca (red, black, yellow, purple, creamy white, pink) in order to evaluate the variation in the accumulation of heavy metals and the level of toxicity of each metal between ecotypes.