Roadside food-vending shanties using coal cookstoves may be an important source of carbon monoxide (CO) exposure in megacities in India. The shanties are often small, congested and poorly ventilated, and very little is known about the level of human exposure to CO. Here, we assessed the level of exposure to CO in 25 roadside food-vending shanties using coal cookstoves in Kolkata, India. Portable electrochemical CO monitors were used to measure CO concentrations during peak and non-peak customer-periods in closed (blocked from three sides) and semi-closed (blocked from two sides) shanties. Measurements were taken where customers sit indoor about 5–7 ft away from the cookstoves. The shanties' ventilation rates were measured using tracer gas concentration-decay technique. Levels of blood carboxyhaemoglobin (COHb) and exhaled CO were estimated using regression models. The 1-hr time weighted average (TWA) indoor CO exposure levels ranged from 7.8 to 18.1 ppm during peak-periods, and 0.7–3.1 ppm during non-peak-periods. The exposure levels during peak-periods exceeded the USEPA's reference limit of 9 ppm in all cases in the closed shanties, and in 71% of cases in the semi-closed shanties. The ventilation rates ranged from 5.5 to 23.4 and 14.8 to 32.5 cubic feet per minute (cfm) per person for the closed and semi-closed shanties, respectively, indicating poor ventilation in some shanties. There was significant variation (p = 0.01) in the level of indoor CO exposure between peak and non-peak periods, and between shanty types. The estimated levels of blood COHb during peak and non-peak hours were 0.78 ± 0.7% and 0.35 ± 0.07%, respectively, that were within the normal physiological values in non-smokers.

Biological tests with plant seeds have been adopted in many studies to investigate the phytotoxicity of pollutants to facilitate the control of risks and remain to be optimized. In this work, the experiment with a small sample size (Experiment 1) and the experiment with a large one (Experiment 2) were designed to study the effect of tetracycline (TC) on Chinese cabbage (Brassica rapa L.) at seed germination and radicle elongation stages. At the former stage, germination number data were obtained to analyze the germination energy (GE) and to judge the probability of the number of germinated seeds (Pₙ) by the binomial distribution model in Experiment 1. While germination time-to-number data were obtained to analyze the mean time to germination (MGT), the estimate of mean time to germination (EMGT) by survival analysis method, the time to germination for 50% of total seeds (T₅₀) and the germination rate (GR) besides GE in Experiment 2. At the latter stage, the data of radicle length (RL) were obtained in all the experiments and the influence from the former stage on this stage was excluded in Experiment 2 but not in Experiment 1. Results showed that TC had universal adverse effects on the latter stage but not on the former stage in the experiments. Considering the availability of germination data for statistical analysis and the robustness of RL data, the methods adopted in Experiment 2 were more feasible than those in Experiment 1. In addition, Chinese cabbage seeds with medium size have the character of rapid germination compared with the commonly used crop species and can be used to shorten the experimental cycle to study the responses of seeds to pollutants to evaluate the phytotoxicity.We introduced survival analysis method to analyze the germination time-to-number data obtained in seed germination test to evaluate the phytotoxicity of tetracycline.

Severe pollution caused by atmospheric particulate matter (PM) has become a global environmental issue. Samples of atmospheric PM were collected before and during the Chinese Spring Festival in Xiamen, a coastal city in Southeast China, to investigate their chemical characteristics, sources, and formation mechanisms. The results indicated that PM₂.₅ mass concentrations comprised 53.60% and 56.31% of total suspended particulates before and during the Spring Festival, respectively. Due to the halt of factory production and construction and the reduction of vehicle flow during the Spring Festival, the concentrations of organic carbon, elemental carbon and water soluble ions in PM₂.₅ decreased by 78.56%, 84.19% and 27.53%, respectively, compared with those before the Spring Festival. However, the concentrations of K⁺, Mg²⁺, Al, Sr, and Ba increased by 3121.76%, 571.67%, 183.71%, 180.15%, and 137.58%, respectively, resulting from the display of fireworks and firecrackers during the Spring Festival. Analysis of backward air mass trajectory indicated that the concentrations of PM₂.₅ and its components were dominated by local pollution sources before and during the Spring Festival. The relationships between meteorological conditions and pollutant concentrations showed that the secondary organic aerosol was generated from the heterogeneous reaction before the Spring Festival, and the secondary inorganic aerosol was formed by the photochemical reaction during the Spring Festival.

Hematite nanoparticles (NPs) exist naturally and ubiquitously in soil, and they are always associated with soil organic matter by forming organic-inorganic complexes. In this work, hematite NPs coated with peat humic acid (HAₚₑₐₜ) and soil humic acid (HAₛₒᵢₗ) were chosen as sorbents for hydrophobic organic contaminants (HOCs) to simulate the sorption processes in soil. Ionizable pentachlorophenol (PCP) and non-ionizable phenanthrene (PHE) were selected as representative HOCs. Compared with sorption isotherms of uncoated hematite NPs, the coating of HA onto the surface of hematite NPs substantially increased its sorption affinity for PCP and PHE by about 1-2 orders of magnitude, and the increasing degree was positively correlated to the HA content. These phenomena emphasized the dominant role of HA in the sorption process. The reduced polarity and the introduction of functional groups contributed to the enhanced sorption of HOCs on HA-coated hematite NPs. Furthermore, HAₚₑₐₜ-hematite NPs showed higher sorption affinity for both PCP and PHE than HAₛₒᵢₗ-hematite NPs, which was mainly due to the lower polarity and higher hydrophobicity of HAₚₑₐₜ-hematite NPs. The sorption of PCP and PHE on HA-coated hematite NPs was inhibited obviously with increasing pH values and the pH effect on PCP sorption was more significant than that of PHE, due to the deprotonation of functional groups within adsorbed HA, the loose structure of adsorbed HA and the dissociation of PCP. Our findings elucidated the mechanisms involved in HOCs sorption processes by HA-hematite NPs and provided a theoretical basis for environmental remediation with natural NPs (e.g., hematite NPs).

Microplastics (MPs) contamination in water environment has recently been documented as an emerging environmental threat due to their negative impact on the ecosystem. Their sources are many, but all of them are from synthetic materials. The sources of MPs are cosmetics and personal care products, breakdown or abrasion processes of other plastic products, textile and tyre, bitumen and road marking paints. Because of their low density and small particle size, they are easily discharged into the wastewater drainage systems. Therefore, the municipal wastewater treatment plants (WWTPs) are indicated to be the main recipients of MPs before getting discharged into the natural waterbodies. Therefore, understanding the occurrence and fate of MPs in WWTPs are of great importance towards its control. The aim of this article is to provide a comprehensive review to better understand the pathways of MPs before entering the WWTPs, characteristics of MPs in wastewater, and the removal efficiency of MPs of the existing wastewater treatment technologies adopted by the WWTPs. This review also covers the development of potential microplastics treatment technologies investigated to date. Based on the review of existing literature, it is found that the existing WWTPs are inefficient to completely remove the MPs and there is a risk that they may get discharged into the ambient water sources.

Increasing urbanisation is altering the physiology of wild animals and the mechanisms involved are largely unknown. We hypothesised that altering the physiology of urban organisms is due to the effect of extra light at night on the circadian clock by modulating the expression of pineal machinery and clock genes. Two experiments were performed. In Experiment 1, immediately after being procured from their respective sites (urban and rural sites), birds were released individually in LLdᵢₘ light conditions. Circadian rhythm period, activity duration, and total activity count were calculated and did not differ between urban and rural birds. In Experiment 2, birds (from urban and rural habitats) were sampled at six time points at regular 4-h intervals, beginning 1 h after sunrise. We measured daily variations in plasma melatonin levels. We also analysed the expression levels of Aanat, Mel1A and Mel1B as an indicator of melatonin biosynthesis and action machinery. Clock and clock-controlled genes (Bmal1, Clock, Per2, Per3, Cry1 and Npas2) were studied in the hypothalamus, the pineal gland, and retina to investigate the effects of urban habitats on the circadian clock. Our results show that there is a lower expression of Aanat in the pineal gland and relatively low plasma melatonin levels in urban birds. Further, clock genes are also differentially expressed in all three central tissues of urban birds. We propose that alterations in the melatonin biosynthesis machinery and the expression of clock genes could result in miscalculations in the internal timing of the organism, with environmental timings leading to altered physiology in urban wild animals.

Rice grain is known to accumulate methylmercury (MeHg) and has been confirmed to be the major pathway of MeHg exposure to residents in mercury (Hg) mining areas in China. Selenium (Se) supplementation has been proven to be effective in mitigating the toxicity of Hg. To understand how Se supplementation influences soil Hg speciation, a wide range of Se (0–500 mg/kg) was applied to Hg polluted paddy soils in this study, which decreased MeHg concentration in soil from 2.95 ± 0.36 to 0.69 ± 0.16 μg/kg (or 77%). After Se addition, humic acid state Hg (F4) was transformed into strong-complexed state Hg (F5), indicating that Hg bound up to the non-sulfur functional groups of humic acid (non-RSH) was released and reabsorbed by strong binding Se functional group (F5). As a result, inorganic Hg (IHg) was reduced by >48%, 18%, and 80% in root, stem, and grain, respectively, however, the reduction was not apparent in leaf. Substantial reductions were also found for MeHg in grain and root, but not in stem and leaf. Soil is suggested to be the main source of both MeHg and IHg in rice grain. Such a finding may provide an idea for improving Hg-polluted paddies through controlling soil IHg and MeHg. Further research on the molecular structure of the strong-complexed Hg in F5 should be conducted to elucidate the mechanism of Hg-Se antagonism.

Nanoplastics have attracted increasing attention in recent years due to their widespread existence in the environment and the potential adverse effects on living organisms. In this paper, the toxic effects of nanoplastics on organisms were systematically reviewed. The translocation and absorption of nanoplastics, as well as the release of additives and contaminants adsorbed on nanoplastics in the organism body were discussed, and the potential adverse effects of nanoplastics on human health were evaluated. Nanoplastics can be ingested by organisms, be accumulated in their body and be transferred along the food chains. Nanoplastics showed effects on the growth, development and reproduction of organisms, and disturbing the normal metabolism. The toxic effects on living organisms mainly depended on the surface chemical properties and the particle size of nanoplastics. Positively charged nanoplastics showed more significant effects on the normal physiological activity of cells than negatively charged nanoplastics, and smaller particle sized nanoplastics could more easily penetrate the cell membranes, hence, accumulated in tissues and cells. Additionally, the release of additives and contaminants adsorbed on nanoplastics in organism body poses more significant threats to organisms than nanoplastics themselves. However, there are still knowledge gaps in the determination and quantification of nanoplastics, as well as their contaminant release mechanisms, degradation rates and process from large plastics to nanoplastics, and the transportation of nanoplastics along food chains. These challenges would hinder the risk assessment of nanoplastics in the environment. It is necessary to further develop the risk assessment of nanoplastics and deeply investigate its toxicological effects.

The cell-free dithiothreitol (DTT) assay is widely used and the DTT consumption rate is interpreted to assess the oxidative potential (OP). Most researchers use an experimental procedure developed by Cho et al. (2005) while some adopt a procedure by Li et al. (2009). The key difference between the two procedures is the initial DTT concentration, 100 μM used in the former and 20 μM in the latter, raising an unaddressed issue of comparability. We examine in this work this issue using metal-free humic-like substance (HULIS) samples isolated from ambient aerosol and two metals (i.e. copper and manganese). We found that higher initial DTT concentrations led to higher DTT consumption rates for both HULIS and metals. For HULIS, the increase in DTT consumption rate was proportional to the initial DTT concentration (i.e., roughly by 5-fold), allowing correction of the concentration effect and direct comparison of results from the two protocols. However, the proportionality did not hold for the metals or metal-organic mixtures. The increase was much lower than the proportionality of 5 and metal concentration-dependent, specifically, 1.2–1.3 for Cu and from negligible to 2.0 for Mn. For six water extracts of ambient aerosol samples, in which HULIS and metals co-exist, the proportionality ranged from 1.3 to 2.2. This deviation from a linear dependence on initial DTT concentration, plausibly due to metal-DTT binding, impedes assessing and comparing OP of metals and metal-organic mixtures using different implementations of the DTT assay. Considering the different antioxidants concentrations in real human lung fluid, this work raises caution about using the DTT assay to assess metal-containing mixtures, such as ambient aerosol samples.

Polycyclic aromatic hydrocarbons (PAHs) are organic compounds composed of at least two benzene rings. This paper reviews the characteristics, sources and health risk of airborne particulate PAHs in Chinese cities. The airborne particulate PAH concentrations varied from 3.35 to 910 ng m⁻³, with an average of 75.0 ng m⁻³, and the pollution level of PAHs in northern cities was generally higher than that in southern cities. The PAH concentrations in different cities underwent similar seasonal variations, with high concentrations in the winter and relatively low concentrations in the summer. Many factors, such as meteorological conditions and source emissions, influenced the spatiotemporal pattern of PAHs. High temperatures, frequent flow exchanges, abundant rainfall and strong solar radiation reduced the level of particulate PAHs in the atmosphere. The historical changes in the level of airborne particulate PAHs in four cities were analyzed. The PAH concentrations in Beijing and Taiyuan presented a trend of first increasing and then decreasing, while the level of particulate PAHs in Nanjing and Guangzhou had a decreasing tendency from year 2000–2015. The airborne particulate PAHs in cities were derived from several sources, including coal combustion, vehicle emissions, coking industries, biomass burning and petroleum volatilization. The results of a health risk assessment indicated that the incremental lifetime cancer risk (ILCR) for people in the northern cities was higher than that for people in the other regions, especially during the cold season. Moreover, adults were at greater risk than people in other age groups, and the health risk to females was slightly higher than that to males. The potential risk of airborne particulate PAH exposure was relatively high in some cities, and controlling PAH emissions at the source should be required to prevent pollution.