Combined Effects Of Heavy Metals Research Articles

Experimental study of toxic effects of cadmium against background of physical exercise

Introduction. Nowadays, working conditions in industry are often associated with chemical exposure along with manual labour. Given the evidence of the combined effect of heavy metals and muscular work, an increase in cadmium toxicity can be expected. However, an experimental study and actual assessment of exposure to both factors are necessary to avoid underestimation or overestimation of real risks. The purpose of our study was to establish health effects of subchronic cadmium toxicity against background of physical exercise. Materials and methods. In a subchronic animal experiment, four groups of outbred male rats, 14 animals each, were exposed to cadmium chloride at a single dose of 0.77 mg/kg body weight, forced physical exercise (treadmill running), both factors combined, or acted as a control group. Hematological, biochemical, and morphometric indices in rodents were assessed at the end of the experiment. The statistical significance of differences between the groups was established using Student’s t-test (p<0.05). For mathematical modelling, we used the Response Surface Methodology (RSM) with the construction of Loewe isoboles. Results. We observed significant unfavorauble shifts in 27.5% of the assessed morphometric, hematological, biochemical, cytological, and histomorphometric indices in rats following the exposure to cadmium only and in combination with exercise. The mathematical analysis based on the response surface modelling showed the typology of the combined impact of chemical and physical factors to vary depending on the specific effect by which it is assessed, as well as on the dose and level of effect. Limitations. Laboratory animals of only one biological species and sex were used for the experiment, exposed to a single concentration of cadmium and physical exercise of only one intensity level. Conclusion. The principles of health effects of cadmium and physical stress as risk factors of the workplace environment specified in the in vivo experiment may serve as a basis for scientific justification of risk assessment criteria to avoid under- or overestimation of real risks in the occupational setting.

Heavy metals and nutrients mediate the distribution of soil microbial community in a typical contaminated farmland of South China

The effects of heavy metals on soil microbial communities have been extensively investigated, whereas the combined effects of heavy metals and nutrients on soil microbial communities and their interactions are rarely understood. In this study, we investigated the distribution patterns of heavy metals, nutrients and microbial communities in a typical contaminated farmland and explored their interaction mechanisms. The results showed that Cd and Pb were the main pollutants in this area, which mainly came from the smelter. Canonical correspondence analysis and variance decomposition analysis showed that the heavy metals played a more important role in restraining the microbial community structure of soils than other soil properties. Soil Cd, Pb, pH and available K content were the most important environmental factors affecting the microbial community structures in soil. Major Cd tolerant bacteria and fungi were detected including Actinobacteriota, Gemmatimonadota, Entorrhizomycota and Mortierellomycota. The analyses of molecular ecological networks showed that there were 84.1 % of negative correlations among microorganisms. Cd could regulate the abundance of key nodes in Cd-tolerant network modules, and these key nodes could improve the adaptability of the whole module to heavy metals through competition with other microorganisms. This study provides insights into the ecological effects of heavy metals and nutrients on soil microbial communities and will help to develop the bio-remediation technologies for contaminated soils.

Cytotoxicity and Antioxidant Defences in Euplotes aediculatus Exposed to Single and Binary Mixtures of Heavy Metals and Nanoparticles

The aim of this study was to analyse the cytotoxicity of heavy metals (HMs) and nanoparticles (NPs) on populations of the ciliated protist Euplotes aediculatus. We used ecotoxicological tests, antioxidant assays, and the MixTOX tool in Microsoft® Excel to evaluate the toxic effect of HMs and NPs in single and binary mixtures on E. aediculatus and to detect the type of interaction between them. Based on our results, the order of toxicity was Cu > Cd >> Zn (1 h and 24 h) for HMs and ZnO > CuO >> TiO2 >> SiO2 (1 h) and CuO > ZnO >> TiO2 >> SiO2 (24 h) for NPs. The interaction between metals in binary mixtures was predominantly synergistic at low doses and antagonistic at high doses. The type of interaction depende on the metals present and their respective concentrations. Furthermore, both HMs and NPs were shown to trigger effective antioxidant responses in E. aediculatus. Our research highlights the importance of considering the combined effects of HMs and NP exposure and their potency in risk assessment.

Threshold and combined effects of heavy metals on the risk of phenotypic age acceleration among U.S. adults.

Accumulation of heavy metals in the body has been shown to affect the phenotypic age (PhenoAge). However, the combined and threshold effects of blood heavy metals on the risk of PhenoAge acceleration (PhenoAgeAccel) are not well understood. A cross-sectional study was conducted using blood heavy metal data (N = 7763, age ≥18 years) from the 2015-2018 National Health and Nutrition Examination Survey. PhenoAgeAccel was calculated from actual age and nine biomarkers. Multiple regression equations were used to describe the relationship between heavy metals and PhenoAgeAccel. Least Absolute Shrinkage and Selection Operator (LASSO) regression modeling was used to explore the relationship between the combined effects of heavy metals and PhenoAgeAccel. Threshold effect and multiple regression analyses were performed to explore the linear and nonlinear relationships between heavy metals and PhenoAgeAccel. Threshold effect analysis showed that blood mercury (Hg) concentration was linearly associated with PhenoAgeAccel. In contrast, lead (Pb), cadmium (Cd), manganese (Mn), and combined exposure were nonlinearly associated with PhenoAgeAccel. In addition, the combination of Pb, Cd, Hg, and Mn significantly affected PhenoAgeAccel. The risk of PhenoAgeAccel was increased by 207% (P < 0.0001). Meanwhile, a threshold relationship was found between blood Pb, Cd, Mn, and the occurrence of PhenoAgeAccel. Overall, our results indicate that combined exposure to heavy metals may increase the risk of PhenoAgeAccel. This study underscores the need to reduce heavy metal pollution in the environment and provides a reference threshold for future studies.

Exploring the combined effect of heavy metals on accumulation efficiency of Salix alba raised on lead and cadmium contaminated soils

The present study illustrated that Salix alba can accumulate high level of Pb and Cd in different plant parts, with maximum accumulation in roots followed by stem and leaves in the order Cd > Pb > Cd + Pb. The phytoremediation evaluation factors such as bioconcentration factor (BCF) and translocation factor (TF) was higher for Cd over Pb in all plant parts, further the BCF for both Pb and Cd was maximum in root (BCF > 1) followed by stem and leaves. Higher accumulation of Cd over the Pb was observed inside the plant tissues due to Cd mimics with other elements and gets transported through respective transporters. The combined treatment of Pb and Cd affected the bioaccumulation at every treatment level suggesting the negative effect among both elements. Higher survival rate (>85%) was recorded up to 200mgPb/kg and 15mgCd/kg, while further increase in metal concentration reduced the plant efficiency to remediate contaminated soils, hence results in declined survival rate. The FTIR analysis revealed that Pb and Cd accumulation in plants induced changes in carboxy, amino, hydroxyl and phosphate groups that ultimately caused alteration in physiological and biochemical processes of plant and thus provided an insight to the interaction, binding and accumulation of heavy metals.

Cytotoxic effects of heavy metals on functional attributes of boar sperm: an in vitro study

Objective: Reproductive toxicology is a field that deals with the effects of heavy metals on various aspects of reproduction, including sperm count, motility, viability, spermatogenesis, follicular atresia, hormonal imbalance, and oocyte maturation, among others. The present study was carried out to examine the effects of heavy metals, viz., arsenic (As), lead (Pb), and fluoride (F), on boar sperm quality parameters in vitro.Materials and Methods: Forty (40) ejaculates from six (6) boars, averaging eight ejaculates per boar, were collected with the gloved hand technique using a dummy sow. Six (6) different concentrations were selected for the in vitro study: 5, 10, 25, 50, 100, and 200 µM for As and Pb, and 5, 10, 25, 50, 100, and 200 mM for F. The ejaculates were co-incubated with heavy metals at these different concentrations and assessed after different incubation periods (0, 0.5, and 1 h) for sperm functional attributes, viz., sperm progressive motility, viability and membrane integrity, and sperm mitochondrial membrane potential (MMP). The combined effects of heavy metals on sperm functional attributes were also evaluated at different doses (5, 10, 25, 50, 100, and 200 μM/μM for As–Pb; 5, 10, 25, 50, 100, and 200 μM/mM for As–F; and 5, 10, 25, 50, 100, and 200 μM/mM for Pb–F).Results: The present study revealed a highly significant (p &amp;lt;0.001) decrease in sperm progressive motility, viable sperm, membrane integrity, and sperm MMP in samples treated with heavy metals under different incubation periods; furthermore, the longer the incubation time, the greater the toxicity. There was also a significant (p &amp;lt;0.05) decrease in sperm motility, membrane integrity, and MMP in the samples treated with combined heavy metals (As–Pb, As–F, and Pb–F), as compared to the control, after different incubation periods. A significant (p &amp;lt;0.05) reduction in sperm quality attributes was recorded even at the lowest concentrations in the case of heavy metal combinations.Conclusion: It can be concluded that As, Pb, and F are toxic to boar spermatozoa in vitro, causing reductions in sperm functional attributes in a dose- and time-dependent manner.

Health risk assessment of arsenic, lead and cadmium from milk consumption in Punjab, India.

Milk is an integral part of the human diet and its contamination with heavy metals may alter the health of its consumers. The study was conducted to assess the health risk associated with the heavy metals in milk samples collected from urban and rural households of Ludhiana and Bathinda districts of Punjab, India. One hundred and fifty milk samples were analyzed for heavy metals i.e. arsenic, cadmium, lead and mercury using Inductively Coupled Plasma Mass Spectrometry ICP-MS. The health risks, such as non-carcinogenic and carcinogenic risks from heavy metals in milk samples, were calculated for selected males and females of adults, children and elderly subjects. The results indicated that the arsenic, cadmium and lead content in milk samples were within permissible limit whereas mercury was not detected in any sample. The mean values showed that the selected urban and rural population of both districts was safe from non-carcinogenic risk associated with heavy metal content of milk. However, urban (50% males and 86% females) and rural (25% males) children of Bathinda district were at risk of cancer from arsenic and cadmium present in milk samples, respectively. It was also observed that the selected population of both districts were safe from carcinogenic risk due to the combined effects of heavy metals. It was concluded that even with a small amount of heavy metal in milk samples, the rural adults, rural male children and urban female children of Bathinda district had carcinogenic risk due to milk consumption. Hence, regular monitoring and testing of milk samples must be done as a public health measure to prevent heavy metal contamination in milk to safeguard the health of consumers.

Plant–Microbe Interactions under the Action of Heavy Metals and under the Conditions of Flooding

Heavy metals and flooding are among the primary environmental factors affecting plants and microorganisms. This review separately considers the impact of heavy metal contamination of soils on microorganisms and plants, on plant and microbial biodiversity, and on plant–microorganism interactions. The use of beneficial microorganisms is considered one of the most promising methods of increasing stress tolerance since plant-associated microbes reduce metal accumulation, so the review focuses on plant–microorganism interactions and their practical application in phytoremediation. The impact of flooding as an adverse environmental factor is outlined. It has been shown that plants and bacteria under flooding conditions primarily suffer from a lack of oxygen and activation of anaerobic microflora. The combined effects of heavy metals and flooding on microorganisms and plants are also discussed. In conclusion, we summarize the combined effects of heavy metals and flooding on microorganisms and plants.

The combined effect of heavy metals and polycyclic aromatic hydrocarbons on arthritis, especially osteoarthritis, in the U.S. adult population

The evaluation of heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) impact on arthritis is usually limited to the analysis of the arthritis subtype (rheumatoid arthritis, RA), whereas studies on osteoarthritis (OA) are relatively sparse. Furthermore, the combined effect of HMs and PAHs co-exposure on arthritis also has rarely been analyzed. Herein, we aimed to comprehensively estimate the association between HMs and PAHs (three blood HMs and six urinary PAHs metabolites) co-exposure and arthritis. Using data from the National Health and Nutrition Examination Survey (NHANES), 2003–2016, we included 9735 adults, of whom 2464 had total arthritis, 1371 had OA, and 468 had RA. The logistic regression model was conducted to estimate the single effect of HMs and PAHs on arthritis. Moreover, weighted quantile sum (WQS) regression, quantile-based g computation (qgcomp), and Bayesian kernel machine regression (BKMR) were separately performed to assess the combined effect of HMs and PAHs co-exposure on arthritis. In the single-exposure analyses, cadmium (Cd) and lead (Pb) statistically grew the risk of total arthritis, OA, and RA. Among PAHs, 1-hydroxynaphthalene (1-NAP) and 3-hydroxyfluorene (3-FLU) showed a positive association with total arthritis, OA, and RA. Meanwhile, 2-NAP also was significantly associated with total arthritis. 2-NAP, 2-FLU, and 1-hydroxyphenanthrene (1-PHE) also were significantly associated with RA. Furthermore, the three complementary models consistently demonstrated that co-exposure to high levels of HMs and PAHs was positively associated with total arthritis, OA, and RA risk. The above associations were more obvious in young and medium-aged people. Interestingly, BKMR analyses indicated that 1-NAP might interact with Cd and 3-FLU in total arthritis, while Pb might interact with Cd in OA. Therefore, this study provided novel evidence that co-exposure to HMs and PAHs positively correlated with arthritis, especially OA, and these results were worthy of further prospective studies.

Heavy Metals Exacerbate the Effect of Temperature on the Growth of Chlorella sp.: Implications on Algal Blooms and Management

With the accelerated urbanization and rapid development of the industrial and agricultural sectors, concern about the pollution of water environments is becoming more widespread. Algal blooms of varying sizes are becoming increasingly frequent in lakes and reservoirs; temperatures, nutrients, heavy metals, and dissolved oxygen are the factors that influence algal bloom occurrence. However, knowledge of the combined effect of heavy metals and temperature on algal growth remains limited. Thus, this study investigated how specific concentrations of heavy metals affect algal growth at different temperatures; to this end, two heavy metals were used (0.01 mg/L Pb2+ and 0.05 mg/L Cr6+) at three incubation temperatures (15, 25, and 30 °C) with the alga Chlorella sp. A higher incubation temperature contributed to a rise in soluble proteins, which promoted algal growth. The density of algal cells increased with temperature, and catalase (CAT) decreased with increasing temperature. Chlorella sp. growth and catalase activity were optimal at 30 °C (algal cell density: 1.46 × 107 cell/L; CAT activity: 29.98 gprot/L). Pb2+ and Cr6+ significantly promoted Chlorella sp. growth during incubation at 25 and 30 °C, respectively. At specific temperatures, 0.01 mg/L Pb2+ and 0.05 mg/L Cr6+ promoted the production of soluble proteins and, hence, the growth of Chlorella sp. The results provide a useful background for the mitigation and prevention of algal blooms.

Combined Phenanthrene and Copper Pollution Imposed a Selective Pressure on the Rice Root-Associated Microbiome.

Combined organic and inorganic pollutants can greatly impact crops and microbes, but the interaction between coexisted pollutants and their effects on root-associated microbes under flooding conditions remains poorly understood. In this study, greenhouse experiments were conducted to investigate the individual and combined effects of phenanthrene (PHE) and copper (Cu) on rice uptake and root-associated microbial coping strategies. The results showed that more than 90% of phenanthrene was degraded, while the existence of Cu significantly reduced the dissipation of PHE in the rhizosphere, and the coexistence of phenanthrene and copper promoted their respective accumulation in plant roots. Copper played a dominant role in the interaction between these two chemicals. Microbes that can tolerate heavy metals and degrade PAHs, e.g., Herbaspirillum, Sphingobacteriales, and Saccharimonadales, were enriched in the contaminated soils. Additionally, microbes associated with redox processes reacted differently under polluted treatments. Fe reducers increased in Cu-treated soils, while sulfate reducers and methanogens were considerably inhibited under polluted treatments. In total, our results uncover the combined effect of heavy metals and polycyclic aromatic hydrocarbons on the assemblage of root-associated microbial communities in anaerobic environments and provide useful information for the selection of effective root-associated microbiomes to improve the resistance of common crops in contaminated sites.

Toxicological effects of different ionic liquids on growth, photosynthetic pigments, oxidative stress, and ultrastructure of Nostoc punctiforme and the combined toxicity with heavy metals

Ionic liquids (ILs1) are used widely because of their excellent properties. However, their ecotoxicity for environment has aroused great concern. Here we studied, the toxicity of three ILs with different numbers of methyl substituents and anions as well as the combined effect of heavy metals to edible algae Nostoc punctiforme. The results show that fresh weight and chlorophyll content decreased, indicating that the growth and photosynthesis were adversely affected. Polysaccharides and soluble protein contents decreased, resulting in a reduced nutritional value of Nostoc punctiforme. ILs can produce many reactive oxygen species (ROS), which lead to increased the malondialdehyde (MDA) content. In order to remove excessive ROS, antioxidant enzymes activity is increased, but decreases under high IL concentration, because the structure and function of the enzymes became damaged. ILs cause stress to algae, as the cell ultrastructure is indicating by increased amounts of starch and osmiophilic globules. The combined action of heavy metals with ILs decreases the antioxidant enzymes activity and chlorophyll content, and increases the MDA content. The results show that the order of toxicity is [C8MIM]Cl >[C8MIM]Br> [C8DMIM]Br. The combination of heavy metals and ILs cause an increase of the toxicity to Nostoc punctiforme.

THE INFLUENCE OF HEAVY METALS ON THE BIOLOGICAL ACTIVITY OF RETISOLS

Environmental problems have not lost their relevance for the Non-Chernozem zone of Russia, the southern part of which belong to the Ryazan region, where in a number of areas there is a critical situation of cultural landscapes contamination of with heavy metals. The aim of the research was to assess the influence of multi-level heavy metal contamination of Retisols for the parameters of its phytotoxicity and the activity of soil enzymes. In the model experiment on Retisols, it was shown that the complex effect of heavy metals that are priority for the Ryazan region such as copper, zinc, lead, cadmium, at doses of 1.5 and 3.5 UEC (approximate permissible concentration) reduces the activity of soil enzymes and has a toxic effect on the cereal-legume mixture. In the variant of the experiment with heavy metal content of 0.5 UEC in the soil, the studied elements, mainly zinc and copper, act as chemical meliorants for Retisols depleted with trace elements. The combined effect of heavy metals (Cu, Zn, Pb, Cd) in doses of 1.5 and 4.5 UEC is phytotoxic what negatively affects the biometric indicators of the cereal-bean mixture, and also leads to accumulation in the biomass in quantities exceeding the permissible standards.

Combined effects of heavy metals and parasite infections on the haematological and biochemical profiles of wild rats from Awotan Municipal Dumpsite in Ibadan City

The combined effects of heavy metals and parasitic infections on wild rats from Awotan municipal dumpsite in Ibadan city southwest Nigeria were determined. A total of thirty rats were captured from the dumpsite and five rats from a control site using live traps. Rats were identified, weighed and body length measured to determine body condition index. Blood samples were collected from the rats using the cardiac puncture method. Rats were euthanized and dissected to extract various organs (kidney, liver and intestine). Intestinal helminths were extracted, identified and preserved. Blood parasites were identified using Giemsa staining technique of thick and thin films while intestinal helminths recovered were preserved and identified to species level. Organs, intestinal helminths and blood samples were digested and concentrated for heavy metals (Fe, Cu, Cr, Cd, and Pb) using Atomic Absorption Spectrophotometry (AAS). Cortisol level was determined using ELISA technique. All statistical significance was at probability value p &lt; 0.05. Three species of rats were captured, Rattus rattus, Rattus novergicus and Cricetomys gambianus. The mean ± sd of the body condition index of the rats from dumpsite and control groups were 1.82±0.17 and 1.59± 0.38 respectively. There were significant differences in the mean values of eosinophils, platelets and white blood cell counts of rats from the two study sites. Overall parasite prevalence in dumpsite and control were 76.6% and 20% respectively. The overall prevalence of parasite species from dumpsite was in the order Hymenolepis diminuta (26.6%) &gt;Monoliformis monoliformis (20%) &gt;Plasmodium spp (20%) &gt;Trypanosoma spp (10%). The mean concentration (mg/kg) of heavy metals in kidney, liver, intestine and blood of wild rats from both dumpsite and control decreased in the order Fe&gt; Cr&gt; Cu&gt; Cd&gt; Pb. Cortisol level was higher in infected rats from dumpsite (351±58.83ng/ml) than in uninfected rats from dumpsite (237.22± 44.46ng/ml), indicating exposure to immune stressors. A higher prevalence of parasitic infection, heavy metal pollution and the elevated cortisol concentrations in infected rats showed that the animals’ health and well-being are compromised.

Antibiotic resistance in heavy metal resistant non-lactose fermenting Enterobacteriaceae colonies cultured from textile industry effluents

Many of the aquatic pathogenic microflora belong to the non-lactose fermenting (NLF) Enterobacteriaceae and emergence as well as the spread of antibiotic resistance in them is now a serious threat to public health worldwide. Growth of textile industries has heavily flourished acting as hub for the ready-made garments factories in Bangladesh. Textile industry effluents may contain heavy metals and it is not clear whether their disposal is strictly monitored or not and their impact on the aquatic microflora have not been properly investigated and monitored. To assess the impact of heavy metals on the emergence and spread of antibiotic resistance in NLF Enterobacteriaceae, samples were collected from four different locations of drains running down effluents from five (n=5) different textile industries located in Savar, Dhaka, Bangladesh. Total bacterial counts (TBCs), minimal inhibitory concentrations (MICs) of heavy metals, antibiotic susceptibility, binary exposure and plasmid profile experiments were performed. TBCs from day 1 to day 5 revealed that most colony forming units (CFUs) uncountable at 10-6 dilution could be counted at 10-10 dilution. A total of 100 NLF bacterial isolates were categorized as type-1 and type-2 using 4 differential media. The MICs of 100% isolates in both type-1 and type-2 for nickel (Ni), lead (Pb) and chromium (Cr) were 0.6 mM, 0.6 mM and 1.0 mM, respectively. In case of type-1, most (38%) showed resistance to azithromycin (AZM) and least (2%) to cefotaxime (CTX). In case of type-2, most (48%) showed resistance to AZM and least (8%) to CTX. Binary exposure experiments revealed the combined effect of heavy metals and antibiotics. Where in most cases, zone of inhibition increased or remained unchanged. In few cases, zone of inhibition decreased. This finding indicated that the heavy metals typically exert negative or no effects on antibiotic resistance in the isolates tested. Plasmid profiling of the type-1 and type-2 NLF isolates resistant to both the antibiotics and heavy metals revealed that one of the five type-1 isolates contained very large plasmid (14 Kb) and four of the eight type-2 isolates contained 13 Kb plasmids and two contained 12 Kb plasmids. These findings indicated that these isolates possibly possess the ability to sequester metals before being discharged into the soil and/or water environment. Keywords: Antibiotics, effluents, heavy metals, minimum inhibitory concentration (MIC), resistance.

English

It is crucial to monitor the microbial ambience in heavy metal enriched industrial effluents that generally discharge into the environment. Therefore, the present study aimed to understand the load of heavy metals in multidrug-resistant lactose fermenting microorganisms isolating from textile industry effluents. Samples were collected from five different textile industrial canals. In most of the cases, the colony forming units (CFUs) per plate were uncountable at 10-6 dilution but countable at 10-10 dilution. A total of 100 lactose fermenting (LF) isolates were selected using 4 differential media and tested for the determination of minimum inhibitory concentrations (MICs) of heavy metals and antibiotic susceptibility. For nickel (Ni), the MIC was 0.3 mM for almost 98% isolates. The MIC was 0.5 mM for chromium (Cr) in almost 99% isolates. For lead (Pb), 100% isolates had a MIC of 0.4 mM. The most prevalent (36%) resistance pattern was found for sulfamethoxazole-trimethoprim (SXT) and only 10% isolates showed resistance to cefotaxime (CTX). The combined effect of heavy metals and antibiotics revealed that in most cases, the antibiotic zone of inhibition was increased. Plasmid profiling showed that among 14 selective isolates, high sized (21kb) plasmid was found in 6 isolates. &nbsp; Key words: Antibiotics, effluents, heavy metals, minimum inhibitory concentration (MIC), antimicrobial resistance.

Independent and combined associations of urinary heavy metals exposure and serum sex hormones among adults in NHANES 2013–2016

Accumulating evidences indicated that heavy metals may disrupt human sex hormones. However, the combined effects of heavy metals on sex hormones remain to be clarified. To explore the independent and combined associations between heavy metal exposure and serum sex hormones among adults, data of 2728 adults from the National Health and Nutrition Examination Survey (NHANES) was applied. We examined independent and combined associations of fourteen urinary heavy metals and three serum sex steroid hormones (total testosterone (TT), estradiol (E2) and sex hormone-binding globulin (SHBG)). Multivariate linear regression was used to evaluate the independent associations between metal exposure and sex hormone alterations. Principle component analysis -weighted quantile sum regression (PCA-WQSR) model was performed to estimate the combined associations in our individuals. In the co-exposure model, we determined that weighted quantile sum (WQS) index of industrial pollutants was negatively associated with E2 in females (WQS Percent change8-metal = -20.6%; 95% CI: -30.1%, -9.96%), while in males WQS index of water pollutants was negatively related to SHBG (WQS Percent change8-metal = -5.35%; 95% CI: -9.88%, -0.598%). Cadmium (Cd), tin (Sn) and lead (Pb) were the dominating metals of female E2-negative association while Ba was the leading contributor related to male SHBG reduction, which was consistent with the results of multivariate linear regression. Additionally, in postmenopausal women, the associations of E2 decrease with heavy metal co-exposure remained significant while Cd and monomethylarsonic acid (MMA) were identified as hazardous metals in the mixture. We concluded that the exposure to heavy metals was associated with human sex hormone alterations in independent or combined manners. Considering the design of NHANES study, further studies from other national-representative surveys are necessary.

Combined effects of heavy metals (Cd, As, and Pb): Comparative study using conceptual models and the antioxidant responses in the brackish water flea

The combined effect of toxic inducers has emerged as a challenging topic, particularly due to their inconsistent impacts on the environment. Using toxic unit (TU) based on LC50 value, we investigated the 48 h acute toxicities of the following combinations: Cd + As, Cd + Pb, As + Pb, and Cd + As + Pb, and binary and ternary combined effects were interpreted using concentration addition (CA) and independent action (IA) model. The molecular effects of these combinations were further examined on the basis of gene expression (four GST and two SOD isoforms) and antioxidant enzymes activity (SOD and GST). The CA-predicted LC50 was similar to the observed results, indicating that the CA model is more applicable for evaluating the combined effects of the metal mixtures. Synergistic effects (ΣTULC50 < 0.8) were observed for the mixtures As + Pb and Cd + Pb, while additive effects (0.8 < ΣTULC50 < 1.2) were observed for the mixtures Cd + As + Pb and Cd + As. No antagonistic effects were observed in this study. Molecular biomarkers for oxidative stress caused by metals, as well as traditional endpoints such as lethality, have shown a clear response in assessing the toxicity of binary and ternary mixtures. This study opens up a new avenue for the use of biomarkers to assess the combined effects of metals in aquatic environments.

Toxicological effects of microplastics and heavy metals on the Daphnia magna

Microplastics (MPs) are gradually spreading around the world and becoming a ubiquitous environmental contamination in aquatic environments. Due to its unique physicochemical properties, MPs are considered to be strong adsorbents for environmental pollutants and may affect their fate and toxicity in the environment. In this study, the adsorption behaviors of four typical heavy metal ions (Pb2+, Cu2+, Cd2+, and Ni2+) on two sizes of polystyrene MPs (10 μm and 50 μm) were investigated based on batch experiments, and the combined effects of heavy metals and MPs were assessed using Daphnia magna as model. The results showed that smaller MPs (SMPs) exhibited higher adsorption capacities for metal ions (0.261–0.579 mg/g) than that of the larger MPs (LMPs) (0.243–0.525 mg/g), and the affinity sequence of heavy metals on MPs is Pb2+ > Cu2+ > Cd2+ > Ni2+. There are better admirable agreements for pseudo-second-order model and Langmuir model to fit the adsorption kinetics and adsorption isotherms, respectively. Additionally, the combined toxicity of MPs and heavy metals was negatively correlated with the adsorption capacity between them. The combined effects of mixtures toward D. magna changed from antagonism to additive effect with increasing MPs concentrations, and SMPs exhibited higher toxicological risk than LMPs. Our findings compared the accumulative effects of various heavy metals on MPs and can contribute to understanding the combined effects of plastics and heavy metals on biota.

Single and combined effect of divalent copper and oxytetracycline on the performance, microbial community and enzymatic activity of sequencing batch reactors

Abstract Divalent copper (Cu 2 + ) and oxytetracycline (OTC) are often encountered in industrial wastewater and municipal wastewater, whereas no systematic report has been found in evaluating the impacts of combined Cu 2 + and OTC on the performance of bioreactor treatment wastewater. In the present study, the performance, nitrogen removal rate, microbial community and enzymatic activity of sequencing batch reactors (SBRs) were compared under the single and combined 20 mg/L Cu 2 + and 5 mg/L OTC. Compared with the absence of Cu 2 + and OTC, the COD and NH 4 + -N removal efficiencies at 5 mg/L OTC was virtually unchanged during the whole operation process, whereas the presence of single Cu 2 + and combined Cu 2 + and OTC inhibited the COD and NH 4 + -N removal. The combined Cu 2 + and OTC had more inhibitory effects on the oxygen uptake rate, nitrification rate and denitrification rate of activated sludge than the single Cu 2 + or OTC. The activities of dehydrogenase, ammonia monooxygenase, nitrite oxidoreductase, nitrite reductase and nitrate reductase were inhibited more by the combined Cu 2 + and OTC than the single Cu 2 + or OTC. The microbial reactive oxygen species production and lactate dehydrogenase release under the combined Cu 2 + and OTC were more than those under the single Cu 2 + or OTC under the same operational time. The microbial richness and diversity of SBRs displayed some obvious differences under the single and combined Cu 2 + and OTC. These findings will be helpful to better understand the combined effects of heavy metals and antibiotics on biological wastewater treatment systems.