Air pollution exposure is a public health emergency, which attributes globally to an estimated seven million deaths on a yearly basis We are all exposed to air pollutants, varying from ambient air pollution hanging over cities to dust inside the home. It is a mixture of airborne particulate matter and gases that can be subdivided into three categories based on particle diameter. The smallest category called PM₀.₁ is the most abundant. A fraction of the particles included in this category might enter the blood stream spreading to other parts of the body. As air pollutants can enter the body via the lungs and gut, growing evidence links its exposure to gastrointestinal and respiratory impairments and diseases, like asthma, rhinitis, respiratory tract infections, Crohn's disease, ulcerative colitis, and abdominal pain. It has become evident that there exists a crosstalk between the respiratory and gastrointestinal tracts, commonly referred to as the gut-lung axis. Via microbial secretions, metabolites, immune mediators and lipid profiles, these two separate organ systems can influence each other. Well-known immunomodulators and gut health stimulators are probiotics, prebiotics, together called synbiotics. They might combat air pollution-induced systemic inflammation and oxidative stress by optimizing the microbiota composition and microbial metabolites, thereby stimulating anti-inflammatory pathways and strengthening mucosal and epithelial barriers. Although clinical studies investigating the role of probiotics, prebiotics, and synbiotics in an air pollution setting are lacking, these interventions show promising health promoting effects by affecting the gastrointestinal- and respiratory tract. This review summarizes the current data on how air pollution can affect the gut-lung axis and might impact gut and lung health. It will further elaborate on the potential role of probiotics, prebiotics and synbiotics on the gut-lung axis, and gut and lung health.

We examined ingestion and retention rates of microplastics (MPs) by two freshwater (Japanese medaka and zebrafish) and two marine fish species (Indian medaka and clown anemonefish) to determine their color preferences and gastrointestinal-tract retention times. In our ingestion experiments, clown anemonefish ingested the most MP particles, followed by zebrafish, and then Japanese and Indian medaka. Next, we investigated color preferences among five MP colors. Red, yellow, and green MP were ingested at higher rates than gray and blue MPs for all tested fish species. To test whether these differences truly reflect a recognition of and preference for certain colors based on color vision, we investigated the preferences of clown anemonefish for MP colors under light and dark conditions. Under dark conditions, ingestion of MP particles was reduced, and color preferences were not observed. Finally, we assessed gastrointestinal-tract retention times for all four fish species. Some individuals retained MP particles in their gastrointestinal tracts for over 24 h after ingestion. Our results show that fish rely on color vision to recognize and express preferences for certain MP colors. In addition, MP excretion times varied widely among individuals. Our results provide new insights into accidental MP ingestion by fishes.

Large quantities of lead/zinc (Pb/Zn) mine tailings were deposited at tailings impoundments without proper management, which have posed considerable risks to the local ecosystem and residents in mining areas worldwide. Therefore, the geochemical behaviors of potentially toxic elements (PTEs) in tailings were in–depth investigated in this study by a coupled use of batch kinetic tests, statistical analysis and mineralogical characterization. The results indicated that among these studied PTEs, Cd concentration fluctuated within a wide range of 0.83–6.91 mg/kg, and showed the highest spatial heterogeneity. The mean Cd concentrations generally increased with depth. Cd were mainly partitioned in the exchangeable and carbonate fractions. The release potential of PTEs from tailings was ranged as: Cd > Mn > Zn > Pb > As, Cd > Pb > Zn > Mn > As and Cd > Pb > Mn > Zn > As, respectively, under the assumed environmental scenarios, i.e. acid rain, vegetation restoration, human gastrointestinal digestion. The results from mineralogical characterization indicated that quartz, sericite, calcite and pyrite were typical minerals, cumulatively accounting for over 80% of the tailings. Sulfides (arsenopyrite, galena, and sphalerite), carbonates (calcite, dolomite, cerussite and kutnahorite), oxides (limonite) were identified as the most relevant PTEs–bearing phases, which significantly contributed to PTEs release from tailings. A combined result of statistical, geochemical and mineralogical approaches would be provided valuable information for the alteration characteristics and contaminant release of Pb/Zn mine tailings.

The unified bioaccessibility method (UBM) was harnessed to assess in vitro oral bioaccessibility pools of dialkyl phthalate congeners (with methyl, –ethyl, –butylbenzyl, –n-butyl, –2-ethylhexyl, and –n-octyl moieties) and bisphenol A at the 17 μg g⁻¹ level in beach sand contaminated with polyethylene microplastics. A variety of sample preparation approaches prior to the analysis of the UBM gastrointestinal extracts, including traditional methods (protein precipitation, liquid-liquid extraction, and solid-phase extraction) and dispersive liquid-liquid microextraction (DLLME) were comprehensively evaluated for clean-up and analyte enrichment. DLLME was chosen among all tested approaches on account of the high extraction efficiency (73–95%, excluding bis(2-ethylhexyl)phthalate and di-n-octyl phthalate), high sample throughput (∼7 min per set of samples), and environmental friendliness as demonstrated by the analytical eco-scale score of 83, and the green analytical procedure index pictogram with green/yellow labeling. The release of the less hydrophobic plastic-laden compounds (dimethyl phthalate, diethyl phthalate and bisphenol A) from the contaminated sample into the body fluids was significant, with bioaccessibility values ranging from 30 to 70%, and from 43 to 74% in gastric and gastrointestinal fluids, respectively, and with relative standard deviation < 17% in all cases. The majority of the compounds were leached during gastric digestion, likely as the combined action of the low pH and the gastric enzymes. The risk exposure analysis revealed that accumulation/concentration in the body fluids is potentially relevant for dimethyl phthalate, diethyl phthalate and bisphenol A, with relative accumulation ratios ranging from 1.1 ± 0.1 to 2.6 ± 0.4. The average daily intake values for the suite of compounds, corrected with the bioaccessibility fraction, ranged from 60 to 430 ng kg of body weight⁻¹·day⁻¹, in all cases, far below the tolerable daily intakes, thus indicating the lack of children health risk by ingestion of microplastic-laden sand with elevated concentrations of plasticizers.

Dietary exposure to chemicals alters the diversity of microbiome communities and can lead to pathophysiological changes in the gastrointestinal system. The organochlorine pesticide dieldrin is a persistent environmental contaminant that bioaccumulates in fatty tissue of aquatic organisms. The objectives of this study were to determine whether environmentally-relevant doses of dieldrin altered gastrointestinal morphology and the microbiome of zebrafish. Adult zebrafish at ∼4 months of age were fed a measured amount of feed containing either a solvent control or one of two doses of dieldrin (measured at 16, and 163.5 ng/g dry weight) for 4 months. Dieldrin body burden levels in zebrafish after four-month exposure were 0 (control), 11.47 ± 1.13 ng/g (low dose) and 18.32 ± 1.32 ng/g (high dose) wet weight [mean ± std]. Extensive histopathology at the whole organism level revealed that dieldrin exposure did not induce notable tissue pathology, including the gastrointestinal tract. A repeated measure mixed model analysis revealed that, while fish gained weight over time, there were no dieldrin-specific effects on body weight. Fecal content was collected from the gastrointestinal tract of males and 16S rRNA gene sequencing conducted. Dieldrin at a measured feed dose of 16 ng/g reduced the abundance of Firmicutes, a phylum involved in energy resorption. At the level of class, there was a decrease in abundance of Clostridia and Betaproteobacteria, and an increase in Verrucomicrobiae species. We used a computational approach called predicted relative metabolomic turnover (PRMT) to predict how a shift in microbial community composition affects exchange of metabolites. Dieldrin was predicted to affect metabolic turnover of uroporphyrinogen I and coproporphyrinogen I [enzyme]−cysteine, hydrogen selenide, selenite, and methyl-selenic acid in the fish gastrointestinal system. These pathways are related to bacterial heme biosynthesis and selenium metabolism. Our study demonstrates that dietary exposures to dieldrin can alter microbiota composition over 4 months, however the long-term consequences of such impacts are not well understood.

Microplastics receive significant societal and scientific attention due to increasing concerns about their impact on the environment and human health. Marine mammals are considered indicators for marine ecosystem health and many species are of conservation concern due to a multitude of anthropogenic stressors. Marine mammals may be vulnerable to microplastic exposure from the environment, via direct ingestion from sea water, and indirect uptake from their prey. Here we present the first systematic review of literature on microplastics and marine mammals, composing of 30 studies in total. The majority of studies examined the gastrointestinal tracts of beached, bycaught or hunted cetaceans and pinnipeds, and found that microplastics were present in all but one study, and the abundance varied between 0 and 88 particles per animal. Additionally, microplastics in pinniped scats (faeces) were detected in eight out of ten studies, with incidences ranging from 0% of animals to 100%. Our review highlights considerable methodological and reporting deficiencies and differences among papers, making comparisons and extrapolation across studies difficult. We suggest best practices to avoid these issues in future studies. In addition to empirical studies that quantified microplastics in animals and scat, ten studies out of 30 (all focussing on cetaceans) tried to estimate the risk of exposure using two main approaches; i) overlaying microplastic in the environment (water or prey) with cetacean habitat or ii) proposing biological or chemical biomarkers of exposure. We discuss advice and best practices on research into the exposure and impact of microplastics in marine mammals. This work on marine ecosystem health indicator species will provide valuable and comparable information in the future.

Tris (2-ethylhexyl) phosphate (TEHP) is one of the most commonly used organophosphorus flame retardant (OPFR) analogues and is commonly detected in surface water and sediments. Limited information is available about the metabolic pathway or metabolite formation related to TEHP in fish. In this study, rare minnows (Gobiocyprisrarus) were exposed to TEHP in static water for 30 d to investigate the bioaccumulation and metabolite distribution in the fish muscle, liver, kidney, gill, GI-tract, ovary and testis. Based on the estimated kᵤₚ,ₚₐᵣₑₙₜ and kd,ₚₐᵣₑₙₜ values, the bioconcentration factors (BCFₚₐᵣₑₙₜ) of TEHP in fish tissues were calculated in the order of kidney > ovary ≈ liver ≈ testis > gill ≈ GI-tract > muscle; this finding was consistent with the results of our previous study on other alkyl-substituted OPFRs. In addition, this study identified the metabolic profiles of TEHP in the liver. TEHP was oxidatively metabolized by the fish to a dealkylated metabolite (di 2-ethylhexyl phosphate; DEHP) and hydroxylated TEHP (OH-TEHP). OH-TEHP further underwent extensive phase II metabolism to yield glucuronic acid conjugates. DEHP was mainly distributed in rare minnow in the following order: liver > GI-tract > kidney ≫ other tissues. However, the metabolite showed lower accumulation potential in fish tissues than TEHP, with metabolite parent concentration factors (MPCFs) for DEHP of less than 0.1 in all the investigated tissues. The BCFₚₐᵣₑₙₜ values of TEHP in various fish tissues were only 9.0 × 10⁻³-7.2 × 10⁻⁴ times its estimated tissue-water partition coefficient (Kₜᵢₛₛᵤₑ₋wₐₜₑᵣ) values based on tissue lipid, protein and water contents, which indicated the significance of biotransformation in reducing the bioaccumulation potential of TEHP in fish. The toxicokinetic data in the present study help in understanding the tissue-specific bioaccumulation and metabolism pathways of TEHP in fish and highlight the importance of toxicology research on TEHP metabolites in aquatic organisms.

Epidemiological evidence suggests that phthalate plasticizers may act as “obesogens”, which are chemicals that exacerbate obesity. The gastrointestinal (GI) system is the primary exposure route for phthalates, however, the relationship between phthalate-driven perturbations of GI system functions that can influence obesity has yet to be examined. To address this knowledge gap, we exposed Danio rerio (zebrafish) for 60 days to either (1) Control feeding (5 mg/fish/day), (2) Overfeeding (20 mg/fish/day) or (3) Overfeeding with diethyl-hexyl phthalate (DEHP) (20 mg/fish/day with 3 mg/kg DEHP). After 60 days, Overfed and Overfed + DEHP zebrafish had elevated body mass, and hepatosomatic and gonadosomatic indices. RNAseq analysis of the GI revealed enrichment of gene networks related to lipid metabolism in the Overfed + DEHP group. Many of the enriched networks were under transcriptional control of peroxisome proliferator activated receptor alpha (pparα), a known modulator of lipid metabolism, immune function, and GI function. Real-time PCR confirmed that pparα was overexpressed in the Overfed + DEHP zebrafish, further revealing a pathway by which DEHP may influence lipid metabolism via the GI. These data increase our understanding of phthalate-driven effects on GI function and lipid metabolism, identifying gut-specific gene networks that may drive phthalate-exacerbated obesity.

The ingestion of microplastics (plastic particles <5 mm) has been observed in a range of marine organisms, and adverse effects have been reported in several species after high concentration exposure. However, the long-term effects of low-dose ingestion remains unclear. The aim of this study was thus to assess the chronic effects of low concentrations of polystyrene microparticles to the intertidal amphipod Echinogammarus marinus, using food consumption, growth, and moulting as endpoints. Amphipods were fed a gelatinous algal feed spiked with microbeads (8 μm) in concentrations of ∼0.9, 9 and 99 microplastics/g for 35 days. E. marinus was also analysed for retention of microplastics, and egestion rate was calculated in a separate high-dose feeding experiment. No significant effects were found in the food consumption or growth assays. There was no accumulation of microplastics in the gut, with only one microbead recorded internally in three (8%) of the exposed amphipods. The low number is likely linked to gastrointestinal functions, allowing for easy egestion of indigestible items. This assumption was supported by the observation that after high-dose exposure, 60% of E. marinus egested all microbeads within 24 h. This study suggests that ingesting low concentrations of 8 μm microplastics do not impair the feeding or growth of amphipods along the exposure period. We hope that negative results such as these may further assist in assessing the impact posed by microplastics to marine organisms.

Recent studies suggest an association between particulate matter (PM) air pollution and gastrointestinal (GI) disease. In addition to direct deposition, PM can be indirectly deposited in oropharynx via mucociliary clearance and upon swallowing of saliva and mucus. Within the GI tract, PM may alter the GI epithelium and gut microbiome. Our goal was to determine the effect of PM on gut microbiota in a murine model of PM exposure via inhalation. C57BL/6 mice were exposed via inhalation to either concentrated ambient particles or filtered air for 8-h per day, 5-days a week, for a total of 3-weeks. At exposure's end, GI tract tissues and feces were harvested, and gut microbiota was analyzed. Alpha-diversity was modestly altered with increased richness in PM-exposed mice compared to air-exposed mice in some parts of the GI tract. Most importantly, PM-induced alterations in the microbiota were very apparent in beta-diversity comparisons throughout the GI tract and appeared to increase from the proximal to distal parts. Changes in some genera suggest that distinct bacteria may have the capacity to bloom with PM exposure. Exposure to PM alters the microbiota throughout the GI tract which maybe a potential mechanism that explains PM induced inflammation in the GI tract.