The occurrence of organochlorine pesticides (OCPs) used decades ago for vector control in urban areas is still reported as a threat to human health. Pyrethroids emerged as a replacement for OCPs in sanitary campaigns and are currently the main insecticides used for vector control worldwide, with prominent use as agricultural and household insecticides, for veterinary and gardening purposes, and as wood preservative. This study aimed to assess the occurrence, seasonal variation, and potential sources of pyrethroids in ambient air of two urban regions of Southeastern Brazil, along with the potential health risks to local populations via inhalation exposure. Pyrethroids were sampled by polyurethane foam passive air samplers and their concentrations were determined by gas chromatography coupled with electron capture negative ionization mass spectrometry (GC/ECNI-MS). Atmospheric pyrethroid concentrations (hereinafter reported in pg m⁻³) were considerably higher than those reported by previous studies worldwide. Cypermethrin (median: 2446; range: 461–15 125) and permethrin (655; 19–10 328) accounted for 95% of the total measured pyrethroids in ambient air. The remaining fraction comprised smaller amounts of bifenthrin (46; <limit of detection (LOD)–5171), deltamethrin (58; <LOD–564), phenothrin (7; <LOD–22) and fenvalerate (0.3; <LOD–3). Bifenthrin, deltamethrin and permethrin were linked to local sources, while cypermethrin, fenvalerate and phenothrin had more prominent regional contributions. In broad terms, most pyrethroids showed no clear seasonal trend. The concentrations and hazard quotients (HQs) showed the following order of occurrence and magnitude: urban > urban-industrial > background areas. HQs increased with decreasing age group, but deterministic and probabilistic estimates did not identify direct health risks for any group. Nevertheless, since only inhalation exposure was considered in this work, other pathways should be investigated to provide a more comprehensive risk assessment of the human exposure to pyrethroids.

PM₂.₅ and PM₁₀ fugitive dust samples from multiple sources (construction, demolition, industrial, agricultural fields, and bare ground) were collected in triplicate for each size bin, from 18 distinct locations in and around Bhopal, central India. The dust samples were dried, sieved, and re-suspended in a chamber fitted with a suitable sampling system, to collect PM₂.₅ and PM₁₀ samples onto Teflon and Quartz filters. The filters were subjected to gravimetric and chemical analyses. Trace elements, water-soluble ions, and thermal-optical carbon fractions were quantified using a variety of analyses. These species were then used to develop PM₁₀ and PM₂.₅ chemical source profiles of the fugitive dust sources. As expected, crustal species were abundant in all source categories. For industrial dust, Fe contribution to mass in both size fractions was about 11.4% and above the upper continental crustal abundance. Further, the source profiles generated for each source were different from their counterparts in the US EPA SPECIATE database and profiles reported in literature. Thus, it will be useful to utilize profiles generated in this study to enhance receptor model performance for the study region. However, collinearity analysis of the profiles revealed that PM₁₀ agricultural and bare ground dust; and PM₂.₅ construction and demolition dust profile pairs may not be separated by receptor models. Finally, a human health risk assessment revealed that construction and industrial dust may pose significant risk to the population. The Incremental Lifetime Cancer Risk (ILCR) metric revealed that adults (2 × 10⁻⁵) and children (1 × 10⁻⁵) were susceptible to cancer risk from exposure to metals in PM₂.₅ fugitive dust. Further, children were more vulnerable than adults. This finding merits further investigation of oxidation state and solubility/bioavailability of Cr and Ni in fugitive dusts.

Sludge and biosolids from wastewater treatment plants (WWTPs), identified as important pathways through which microplastics (MPs) can enter the wider environment, contain high organic content, which can obstruct MP quantification/identification. Time- and cost-effective removal of organics is a significant barrier to MP analysis. This study aims to alleviate these obstacles using a widely available store-bought septic tank cleaner, comprised of enzymes and bacteria. The cleaner was added to sludge samples, obtained from a local WWTP. Digestion was tested across a range of cleaner concentrations and heat treatments, and compared to a control digestion without cleaner. Organic content of samples digested with cleaner was reduced by 93%, representing a 22% greater reduction compared to control samples. Virgin plastic pellets, of a variety of polymers, were subjected to the digestion process and underwent no physical or chemical changes, demonstrating this method does not degrade MPs. As all enzymes were added in a single step, the time required for enzymatic digestion using the cleaner was only two days. Compared to existing methods, which take up to several weeks, this novel enzymatic digestion method offers a viable means of extracting MPs from organic materials without either the long processing times required of chemical (solely Fenton's) methods or high cost of laboratory grade enzyme approaches.

Large-scale ecotoxicological studies have technical and ethical limitations, both related to the need to expose large numbers of individuals to potentially harmful compounds. The computational modeling is a complementary useful and predictive tool that overcomes these limitations. Considering the increasing interest in the effects of pesticides on behavioral traits, the aim of this study was to evaluate the effects of chlorpyrifos (CPF) on intra- and inter-specific interactions of anuran tadpoles, complementing traditional ecotoxicological tools with a theoretical analysis verified by computational simulations. Experiments were developed under two consecutive phases: a first phase of exposure (treated and control group), and a second phase of interactions. The second phase consisted of evaluating the effects of CPF on intra- and inter-specific interactions of exposed C. ornata (Co) tadpoles acting as predators and unexposed Rhinella fernandezae (Rf) tadpoles acting as prey (Experiment I), under different predator-prey proportions (0/10 = 0Co–10Rf, 2/8, 4/6, 6/4, 8/2, 10/0). Also, intraspecific interactions of three Co tadpoles under different conditions of exposure were evaluated (Experiment II: 3 exposed Co, 2 exposed Co/1 non-exposed, 1 exposed Co/2 non-exposed). During the exposure phase, chlorpyrifos induced significant mortality from 48 h (48 h: p < 0.05, 72 h–96 h: p < 0.001), irregular swimming, tail flexure, and the presence of subcutaneous air. Also, it induced effects on the sounds emitted after 96 h of exposure, registering a smaller number of pulses and higher dominant frequencies, and altered intra- and inter-specific interactions. During the interaction phase, the larvae continued to show sound effects, however, the antipredator mechanism continued to be operating and efficient. Finally, it was possible to model the behavior of the larvae under the effects of chlorpyrifos. We conclude that experimental data and computational modeling matched. Therefore, computational simulation is a valuable ecotoxicological tool that provides new information and allows prediction of natural processes.

This study explored biochar (BC) amendment effects on microcystin-LR (MCLR) concentration-dependent sorption and sequential desorption (SDE) by diverse soils to assess MCLR-trapping by BC-amended soils. Soil properties varied with rising BC dose and aging time. As aging proceeded, BC-amended soils shared a generally similar ‘firstly increase and then decrease’ trend of MCLR sorption and ‘firstly decrease and then increase’ trend of desorption at most cases. It appeared that MCLR sorption by BC-amended soils was most positively correlated with mesoporosity and surface basic functionality. BC-amendment increased MCLR-trapping for most soils, especially 4% BC at 3 month-aging maximized trapping ratio of GZ, SY and SX to 86.59%–95.43%, 80.01%–87.20% and 78.73%–90.85%, respectively, at 50–500 μg/L MCLR by largely increasing sorption and decreasing desorption. BC-amendment best matched GZ soil because MCLR-trapping of BC-amended GZ exceeded other amended soils at the same BC dose and aging time, but failed to obviously increase MCLR-trapping of HS soil at most cases, except only case with 2% BC at 3 month-aging. Site energy distribution verified that maximally enhanced MCLR-trapping of most soils was due to greatly enhanced sorption affinity during sorption and 1st desorption cycle, making closer MCLR-binding that more resistant to desorption. Contrarily, BC-amendment did not enhance sorption affinity of HS along sorption-SDE to compromise MCLR-trapping increase at most cases. This study validated 3 months as suitable BC-aging time to maximize MCLR-trapping in diverse soils, and elucidated influencing factors and mechanisms from view of site energy distribution, which shed novel insights on MCLR sorption-desorption by BC-amended soils, and guided to optimize BC-amendment strategy for efficient MCLR-immobilization and eco-risk elimination in diverse soils.

Polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) emission is one of main concerns for the secondary pollution of municipal solid waste incinerators (MSWI). For timely response to emission, 1,2,4-trichlorobenzene (1,2,4-TrClBz) as dioxin indicator can be monitored via online measurement techniques. In this study, multi-walled carbon nanotubes (MWCNTs) were investigated for their suitability as a 1,2,4-TrClBz sorbent for MSWI stack gas analysis. The tests include, batch adsorption, continuous adsorption-desorption of 1,2,4-TrClBz via thermal desorption coupled with gas chromatography (TD-GC-ECD), temperature and concentration stability of MWCNTs, and adsorption performance of the system. Thermogravimetric/derivative thermogravimetric (TGA/DTG) analysis reveals that MWCNTs has higher capacity in terms of weight loss (14.34%) to adsorb 1,2,4-TrClBz compared to Tenax TA (9.46%) and also shows fast desorption of adsorbate at temperature of 87 °C compared to Tenax TA (130 °C). Interestingly, carbon nanotubes and Tenax TA gave almost similar adsorption-desorption response, and from TD-GC-ECD analysis it was found that with increasing mass flow of 1,2,4-TrClBz (7.42 × 10⁻⁶ - 44.52 × 10⁻⁶ mg ml⁻¹) through sorbent traps, average peak areas increased from 2.86 ± 0.02 to 13.54 ± 0.26 for MWCNTs and 2.89 ± 0.02 to 13.38 ± 0.12 for Tenax TA, respectively. The stability of MWCNTs for temperature was 400 °C and for concentration of 1,2,4-TrClBz was 50 ppbv. However, regeneration of sorbent at 100 ppbv (1,2,4-TrClBz) was not possible. TD-GC-ECD system showed high adsorption performance with 3.86% and 3.59% relative standard deviation at 250 °C and 300 °C, respectively. Further Fourier Transform Infrared Spectroscopy (FTIR) analysis confirmed that adsorbate can be fully desorbed at 300 °C.

The sorption behavior of phthalate additives in plastic and microplastic litter is an important process controlling the exposure, net health risk and ecotoxicity of these co-occurring pollutants. Plastic crystallinity and particle morphology are hypothesized to be important variables for microplastics sorption behavior, but to date there have been few direct studies to explicitly test for the influence of these parameters. To address this, in this study we explored the sorption of dibutyl phthalate (DBP) as a probe molecule to diverse polyethylene microplastics including irregularly-shaped pure polyethylene microplastics (IPPM), black plastic film microplastics (BPFM), white plastic film microplastics (WPFM), and commercial microspheres (CM), which had crystallinities ranging from 17 to 99%. Sorption kinetics for all materials could be well represented with both a pseudo-first-order (R² = 0.87–0.93) and pseudo-second-order model (R² = 0.87–0.93). Further, sorption was highly linear in the concentration range of 0.5–10 mg L⁻¹, with no greater performance from a linear sorption model (R² = 0.96–0.99) than the non-linear Freundlich or Temkin sorption models. The partition coefficient (Kd) of DBP sorption onto IPPM, BPFM, WPFM and CMs were 1974.55 L kg⁻¹, 1483.85 L kg⁻¹, 1477.45 L kg⁻¹ and 509.37 L kg⁻¹, respectively, showing a significant decrease with increasing crystallinity (r² = 0.98). The particle size of microplastics (27–1000 μm) is, however, an indecisive factor affecting their sorption behavior for DBP in this study. This study provides new insight that crystallinity plays a governing role on the sorption of phthalate from microplastic. This should be considered in future exposure studies and assessments of phthalates from plastics and microplastics.

Low-cost air quality sensors can help increase spatial and temporal resolution of air pollution exposure measurements. These sensors, however, most often produce data of lower accuracy than higher-end instruments. In this study, we investigated linear and random forest models to correct PM₂.₅ measurements from the Denver Department of Public Health and Environment (DDPHE)’s network of low-cost sensors against measurements from co-located U.S. Environmental Protection Agency Federal Equivalence Method (FEM) monitors. Our training set included data from five DDPHE sensors from August 2018 through May 2019. Our testing set included data from two newly deployed DDPHE sensors from September 2019 through mid-December 2019. In addition to PM₂.₅, temperature, and relative humidity from the low-cost sensors, we explored using additional temporal and spatial variables to capture unexplained variability in sensor measurements. We evaluated results using spatial and temporal cross-validation techniques. For the long-term dataset, a random forest model with all time-varying covariates and length of arterial roads within 500 m was the most accurate (testing RMSE = 2.9 μg/m³ and R² = 0.75; leave-one-location-out (LOLO)-validation metrics on the training set: RMSE = 2.2 μg/m³ and R² = 0.93). For on-the-fly correction, we found that a multiple linear regression model using the past eight weeks of low-cost sensor PM₂.₅, temperature, and humidity data plus a near-highway indicator predicted each new week of data best (testing RMSE = 3.1 μg/m³ and R² = 0.78; LOLO-validation metrics on the training set: RMSE = 2.3 μg/m³ and R² = 0.90). The statistical methods detailed here will be used to correct low-cost sensor measurements to better understand PM₂.₅ pollution within the city of Denver. This work can also guide similar implementations in other municipalities by highlighting the improved accuracy from inclusion of variables other than temperature and relative humidity to improve accuracy of low-cost sensor PM₂.₅ data.

The recent emergence of plasmid-borne mobilized colistin resistance (mcr) genes largely challenges the clinical use of colistin. Monitoring the distribution of mcr genes in environment is important for aiding to develop effective control measures. In this study, we aimed to evaluate the occurrence of a recent reported mcr variant, mcr-10, in hospital sewage water. mcr-10 was identified in three Enterobacter roggenkampii strains with high-level colistin resistance (MIC ≥ 16 mg/L). The three strains were assigned to different sequence types suggesting a sporadic dissemination of mcr-10 in the sewage water. Pairwise comparisons of the predicted protein structures of ten mcr homologues revealed that MCR-10 shares a higher similarity with MCR-3, MCR-4, MCR-7, and MCR-9. Overexpression in Escherichia coli Top10 showed that the activity of mcr-10 against colistin is lower than that of mcr-9. mcr-10 expression can be specifically induced by colistin, and it was co-upregulated with phoPQ to mediate the high-level colistin resistance. The mcr-10 gene was detected on self-transmissible plasmids in two isolates and on the chromosome in the other one. Blasting in Genbank suggested that the two mcr-10-bearing plasmids (pECL981-1 and pECL983-1) were novel plasmids, and replicon typing showed that they belong to IncFIB-FII and IncFIB, respectively. Plasmid-curing assay evidence that pECL981-1 was lack of fitness cost for the host. Three novel types of the genetic context were found for the mcr-10 gene in the three isolates. The structure xerC-mcr10 was dominant in mcr-10-positive genomes (39/42) retrieved in Genbank, suggesting that xerC might be involved in the mobilization of mcr-10. To our knowledge, this is the first report of mcr-10-producing E. roggenkampii detected in hospital sewage water. Our study highlights that continuous monitoring of mcr genes in hospital sewage water is imperative for understanding and tackling the dissemination.

Chlorine-based compounds are typical persistent organic pollutants (POPs) that are widely generated in industrial production. This paper reports an effective and rapid pulsed laser irradiation technique for the dechlorination of hexachlorobenzene (HCB), a model pollutant, without additional catalysts or supports. The effects of the laser parameters, including the laser wavelength and power, on the dechlorination efficiency, were also investigated. The optimized results showed that a lower laser wavelength of 266 nm with 10 mJ/pulse power exhibited the highest dechlorination efficiency with 95% within 15 min. In addition, the laser beam effect was examined by designing the direct-pulsed laser single and multipath irradiation system. The results showed that improving the laser beam profile resulted in more than 95% dechlorination efficiency within 5 min. Thus, the dechlorination reaction proceeded much faster as the surface area that the laser beam came in contact with increased due to the multipath system than the single pathway. Gas chromatography identified benzene as the final product of HCB with pentachlorobenzene (PCB), tetrachlorobenzene (TeCB), trichlorobenzene (TCB), dichlorobenzene (DCB), and chlorobenzene (CB) as intermediate products. The mechanism of HCB dechlorination was explained by a comparison of theoretical calculations with the experimental results. The present study reports an advanced technique for the complete dechlorination of chlorobenzenes, which holds great application potential in environmental remediation.