Health risk assessment of heavy metal exposure through vegetable consumption around a phosphorus chemical plant in the Kaiyang karst area, southwestern China

Heavy metal contamination of vegetables in China: status, causes, and impacts

Exposure to heavy metals from vegetable consumption poses a serious health risk to the Chinese population. The lack of knowledge on the overall status of vegetable contamination at the national level hinders the development of national regulations on preventing heavy metal exposure. To address this issue, the study presents an overview of heavy metal contamination in vegetables across China based on 96 peer-reviewed studies published over the past 20 years. The average concentrations of As, Cd, Cr, Cu, Mn, Ni, Pb, and Zn in the edible parts of vegetables are 3.7 ± 12.9, 1.6 ± 4.0, 4.3 ± 10.3, 18.6 ± 27.6, 164 ± 281, 4.5 ± 5.5, 7.7 ± 23.7, and 105 ± 283 mg kg-1 (dry weight), respectively. The associated daily exposures are 0.1-5.7, 0.1-1.7, 0.6-4.2, 4.1-20.5, 26-107, 0.7-3.0, 0.4-16.0, and 13-93 μg kg-1 d-1, respectively. General linear models explained 80%, 44%, 83%, 79%, 64%, 81%, 65%, and 55% of the total variance in As, Cd, Cr, Cu, Mn, Ni, Pb, and Zn concentrations in vegetables, respectively, based on vegetable type and selected geological, meteorological, economic, and environmental factors. Agroforestry is the main source of heavy metal contamination, accounting for 3%-30% of the total variance in heavy metal concentrations in vegetables. Mining, smelting, refining, metalworking, and electrical equipment manufacturing are important source of As, Cr, Cu, Mn, Ni, and Pb, accounting for 7%-17% of the total variance.

Heavy Metals Accumulation in Vegetables and Its Consequences on Human Health in the Areas Influenced by Industrial Activities

The degradation of the environment due to numerous industrial practices has emerged as a major issue globally, particularly in a country like Bangladesh. The present study dispenses information about heavy metal (Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb) contamination in some frequently consumed vegetables, namely, ash pumpkin, potato, bitter gourd, buffalo spinach, snake gourd, and pointed gourd grown in an industrially prone location and their repercussion on consumers' health. Proton-induced X-ray emission (PIXE) technique was used as the major analytical tool to detect heavy metal concentrations. Mean concentration and the range of Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb in vegetables were detected (4.81 ± 2.79, 2.43-10.94), (497.57 ± 258.08, 181.24-886.67), (644.49 ± 298.40, 179.56-998.78), (38.88 ± 14.31, 18.88-60.12), (58.11 ± 12.58, 42.55-84.79), (137.24 ± 48.37, 71.99-208.98), (123.31 ± 63.62, 49.97-256.09), (8.09 ± 2.69, 4.29-14.94), and (4.16 ± 2.95, 1.22-9.98) mg/kg (dry weight basis), respectively. An extreme level of heavy metal contamination in vegetable samples was notified regarding the estimated metal pollution index (MPI) and Nemerow pollution index (P) value, which underpinned the health risk values. The estimated hazard index (HI) value stipulated high risk in all varieties of vegetables regardless of age group and cadmium (Cd) was found as the major contributor. Concerning the carcinogenic risk index (CR) for single elements, the value of Co, Ni, and Cr was approximated far above the USEPA threshold risk limit (CR>1E-04). Moreover, total carcinogenic risk (TCR) for all varieties of vegetables exceeded the safety threshold value for both the age group and children, in particular, were found most vulnerable. The outshot of the present study divulged associated health risks for the population group by the heavy metals via dietary intake of vegetables.

Multicontamination Toxicity Evaluation in the Model Plant Lactuca sativa L

Many contaminated soils contain several toxic elements (TEs) in elevated contents, and plant-TE interactions can differ from single TE contamination. Therefore, this study investigated the impact of combined contamination (As, Cd, Pb, Zn) on the physiological and metabolic processes of lettuce. After 45 days of exposure, TE excess in soil resulted in the inhibition of root and leaf biomass by 40 and 48%, respectively. Oxidative stress by TE accumulation was indicated by markers-malondialdehyde and 5-methylcytosine-and visible symptoms of toxicity (leaf chlorosis, root browning) and morpho-anatomical changes, which were related to the change in water regime (water potential decrease). An analysis of free amino acids (AAs) indicated that TEs disturbed N and C metabolism, especially in leaves, increasing the total content of free AAs and their families. Stress-induced senescence by TEs suggested changes in gas exchange parameters (increase in transpiration rate, stomatal conductance, and intercellular CO2 concentration), photosynthetic pigments (decrease in chlorophylls and carotenoids), a decrease in water use efficiency, and the maximum quantum yield of photosystem II. These results confirmed that the toxicity of combined contamination significantly affected the processes of lettuce by damaging the antioxidant system and expressing higher leaf sensitivity to TE multicontamination.

Ecological assessment of stream water polluted by phosphorus chemical plant: Physiological, biochemical, and molecular effects on zebrafish (Danio rerio) embryos

The rapid development of the phosphorus chemical industry has caused serious pollution problems in the regional eco-environment. However, understanding of their ecotoxic effects remains limited. This study aimed to investigate the developmental toxicity of a stream polluted by a phosphorus chemical plant (PCP) on zebrafish embryos. For this, zebrafish embryos were exposed to stream water (0, 25, 50, and 100% v/v) for 96 h, and developmental toxicity, oxidative stress, apoptosis, and DNA damage were assessed. Stream water-treated embryos exhibited decreased hatching rates, heart rates, and body lengths, as well as increased mortality and malformation rates. The general morphology score system indicated that the swim bladder and pigmentation were the main abnormal morphological endpoints. Stream water promoted antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POD), and glutathione peroxidase (GPx)), lipid peroxidation, and DNA damage. It also triggered apoptosis in the embryos' heads, hearts, and spines by activating apoptotic enzymes (Caspase-3 and Caspase-9). Additionally, stream water influenced growth, oxidative stress, and apoptosis-related 19 gene expression. Notably, tyr, sod (Mn), and caspase9 were the most sensitive indicators of growth, oxidative stress, and apoptosis, respectively. The current trial concluded that PCP-polluted stream water exhibited significant developmental toxicity to zebrafish embryos, which was regulated by the oxidative stress-mediated activation of endogenous apoptotic signaling pathways.

Heavy metal contamination in duck eggs from a mercury mining area, southwestern China

Objective

Mercury (Hg) contamination in the environment around mercury mines is often accompanied by heavy metal contamination.

Methods

Here, we determined concentrations of chromium (Cr), zinc (Zn), strontium (Sr), barium (Ba), and lead (Pb) in duck eggs from a Hg mining area in Southwest China to assess the contamination and health risk.

Results

Duck eggs obtained from the mining area exhibit higher concentrations of Cr, Zn, Sr, Ba, and Pb compared to those from the background area, with egg yolks containing higher metal levels than egg whites. Specifically, the mean Cr, Zn, Sr, Ba, and Pb concentrations of duck eggs from the Hg mining area are 0.38, 63.06, 4.86, 10.08, and 0.05 μg/g, respectively, while those from the background area are only 0.21, 24.65, 1.43, 1.05, and 0.01 μg/g. Based on the single-factor contamination index and health risk assessment, heavy metal contamination in duck eggs poses an ecological risk and health risk.

Conclusion

This study provides important insight into heavy metal contamination in duck eggs from Hg mining areas.

Contamination Status and Ecological Security Thresholds of Fluoride in Farmland around a Phosphorus Chemical Plant in a Karst Area of Southwestern China

The phosphorus chemical plant (PCP) production process leads to the substantial discharge of fluoride into the surrounding environment. However, there is limited research data regarding the pollution levels and ecological safety thresholds of farmland fluoride around PCPs in karst areas. This study evaluates the local contamination status and health risks by determining the fluoride content in farmland and vegetables in vicinity of a PCP in a karst area of Southwestern China. Farmland ecological security threshold was derived based on the species sensitivity distribution (SSD) model. Results showed that the fluoride contents in the soil ranged from 529.36 to 1496.02 mg kg^-1, with the median value of 823.93 mg kg^-1, which was higher than the national background value in China (478 mg kg^-1) by 172.37%. Fluoride contents in vegetables ranged from 0.01 to 25.21 mg kg^-1, with the median value of 1.29 mg kg^-1, which was higher than the limits of contaminants in food (1 mg kg^-1) by 129.00%, and 53.85% of vegetable samples were contaminated. Leafy vegetables showed a higher tendency of fluoride enrichment compared to non-leafy vegetables. Despite there being no significant health risk to the residents via the intake of vegetables overall, there may be potential health risks from the intake of sweet potato leaves. Based on the SSD model, the ecological safety thresholds of fluoride in local farmland was classified into the suitable for planting category (≤174.13 mg kg^-1), safe plant utilization category (174.13-4005.42 mg kg^-1), and strict control of planting category (≥4005.42 mg kg^-1). These findings will provide valuable insights to facilitate the safe cultivation of local agricultural products and optimize the utilization of soil resources.

Health Risk and Quality Assessment of Vegetables Cultivated on Soils from a Heavily Polluted Old Mining Area

Three garden vegetables-radish, carrot and lettuce-were cultivated in a pot experiment using two soils from the Příbram area polluted mainly by cadmium (Cd), zinc (Zn), lead (Pb) and chromium (Cr). The soils of the Příbram district, Czech Republic, are heavily polluted as a result of the atmospheric deposition of toxic elements originating from historic lead-silver mining and smelting activities. The results showed that lettuce absorbed the highest amounts of toxic elements (Cd 28 and 30, Cr 12 and 13, Zn 92 and 205 mg·kg^-1 DW), except Pb, which was higher in radish (30 and 49 mg·kg^-1 DW). Changes in macronutrient contents in edible parts were not found, except for sulfur. A higher total free amino acids (fAAs) accumulation was shown in all vegetables in more contaminated soil, with the highest fAA content being in radish. A group of essential fAAs reached 7-24% of total fAAs in vegetables. The risk to human health was characterized using the target hazard quotient and total hazard index (HI). The cumulative effect of the consumption of vegetables with HI > 1 showed possible non-carcinogenic health effects for lettuce and carrot. HI decreased in the order Cd > Pb > Cr > Zn. The carcinogenic risk of toxic elements decreased in the order Cd > Cr > Pb (0.00054, 0.00026, 0.00003). These values showed a carcinogenic risk from the consumption of lettuce and carrot and confirmed that the adult population of the studied area is at high risk if lettuce and carrot cultivated in this area are consumed daily.