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Constantly raising microplastic (MP) contamination of water sources poses a direct threat to the gentle balance of the marine environment. This study focuses on a multifactor hazard evaluation of conventional (polyethylene - PE, polypropylene - PP, and polystyrene - PS) and alternative (polyethylene terephthalate with 25 % or 50 % recycled material and polylactic acid) plastics. The risk assessment framework explored included MP abundance, water acidification potential, surface oxidation, fragmentation, and bacterial growth inhibition. Based on MP monitoring campaigns worldwide, we conclude that PE-based plastics are the most abundant MPs in water samples (comprise up to 82 % the MP in those samples). A year-long weathering experiment showed that PS-based and PP-based plastics were oxidized to a higher extent, resulting in the highest water acidification with pH reduction of up to three orders of magnitude. Finally, our laboratory experiments showed that weathered PS was the most fragile plastic during mechanical degradation, while both PP- and PS-based plastic extracts showed a significant growth inhibition toward the marine microorganisms (Bacillus sp. and Pseudoaltermonas sp). Using the examined factors as weighted inputs into our framework, this holistic evaluation of hazards suggest that PP-based plastic products were the most hazardous compared to the other conventional and alternative plastic types.

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Although substantial quantities of toxic wastes are generated from textile industries, the characteristics of textile processing wastes (TPWs) have yet scantily been investigated from ecological and agricultural perspectives. Here, the eco-geological consequences of TPWs are evaluated by considering three types of sludges (i.e., silk fibre sludge (SFS), dye mixed silk processing sludge (DSPS), and cotton processing wastewater sludge (CPWS)). The predominance of certain components between different wastes (e.g., fibrous substances in silk industry wastes (i.e., SFS and DSPS) and amorphous materials in cotton processing wastes (i.e., CPWS)) is accounted for by the use of different raw materials in different industries. According to the FTIR and other characterization analyses, all three types of TPWs were rich in carbonaceous compounds and nutrients (e.g., CNPK) because of their biological origin. Further, high accumulation of toxic metals (e.g., Cd, Cr, Cu, Zn, Pb, and Mn) was apparent with chemical-processing routes. The principal component analysis indicated strong relationships between certain environmental variables (e.g., moisture content and bulk density) and bioavailability of several metals (e.g., Cd, Zn, Cu, and Mn), while C levels in TPWs were tightly associated with Cr levels. According to the Visual MINTEQ model, the dissolution-precipitation dynamics of potentially toxic elements (e.g., Pb, Cr, and Zn) in TPWs are predicted to be controlled by the levels of phosphates/chlorides/sulphates in line with the textile processing steps employed in different factories. The great toxicity potential of CPWS (e.g., relative to SFS and DSPS) is recognized to pose significant metal-induced hazards to ecosystems and human health over time. Among the three TPWs, SFS could be prescribed for agricultural application after proper treatment (e.g., via valorization techniques) with the aid of its benign nature and high nutrient (Total N: 3.83%; available P: 118.6 mg kg-1) value.

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Polymeric polyisocyanate prepolymer substances are reactive intermediates used in the manufacture of various polyurethane products. Knowledge of their occupational and environmental hazard properties is essential for product stewardship and industrial hygiene purposes. This work reports on the systematic design of a program to explore how structural features (i.e., types of polymeric polyol and diisocyanate reactants, functionality) and physical-chemical properties (i.e., octanol-water partition coefficient [log Kow], viscosity, molecular weight) of a group of 10 toluene diisocyanate (TDI)- and methylene diphenyl diisocyanate (MDI)-based monomer-depleted prepolymer substances can be related to their exposure and hazard potentials. The revelation of trends or thresholds in such relationships could form a basis for regulatory screening of existing or new prepolymer substances, while also informing the design of substances having reduced exposure and/or hazard profiles. As a first step, the aquatic exposure and hazard potentials of these 10 substances were investigated. The results of this investigation showed that yields of dissolved reaction products (derived from non-purgeable organic carbon measurements and carbon contents of the parent prepolymers) were inversely correlated with the calculated log Kow of the substances. For prepolymer loading rates of both 100 and 1000 mg/L in water, the average dissolved reaction product yields ranged from ≤1% to 32% and from ≤0.1% to 25%, respectively, over calculated log Kow values ranging from -4.8 to 45. For both loading rates, dissolved reaction products were not quantifiable where the calculated log Kow value was >10. Yet, none of the 10 prepolymers and tested loading rates exhibited acute adverse effects on the aquatic invertebrate, Daphnia magna, in the 48-h acute immobilization test. From a product stewardship perspective, polymeric prepolymers of TDI and MDI within the investigated domain and concentration range are not expected to be hazardous in the aquatic environment.

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Diacetyl (DA) is a highly reactive alpha diketone associated with flavoring-related lung disease. In rodents, acute DA vapor exposure can initiate an airway-centric, inflammatory response. However, this immune response has yet to be fully characterized in the context of flavoring-related lung disease progression. The following studies were designed to characterize the different T cell populations within the lung following repetitive DA vapor exposures. Sprague-Dawley rats were exposed to 200 parts-per-million DA vapor for 5 consecutive days × 6 h/day. Lung tissue and bronchoalveolar lavage fluid (BALF) were analyzed for changes in histology by H&E and Trichrome stain, T cell markers by flow cytometry, total BALF cell counts and differentials, BALF IL17a and total protein immediately, 1 and 2 weeks post-exposure. Lung histology and BALF cell composition demonstrated mixed, granulocytic lung inflammation with bronchial lymphoid aggregates at all time points in DA-exposed lungs compared to air controls. While no significant change was seen in percent lung CD3+, CD4+, or CD8+ T cells, a significant increase in lung CD4+CD25+ T cells developed at 1 week that persisted at 2 weeks post-exposure. Further characterization of this CD4+CD25+ T cell population identified Foxp3+ T cells at 1 week that failed to persist at 2 weeks. Conversely, BALF IL-17a increased significantly at 2 weeks in DA-exposed rats compared to air controls. Lung CD4+CD25+ T cells and BALF IL17a correlated directly with BALF total protein and inversely with rat oxygen saturations. Repetitive DA vapor exposure at occupationally relevant concentrations induced mixed, granulocytic lung inflammation with increased CD4+CD25+ T cells in the rat lung.

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This review aims to elucidate the current knowledge and future research needs regarding the hazard potential of nanocellulose to human health. Growing interest from research and industry alike has led to increasing likelihood of human contact to the material via various exposure routes. Although a number of comprehensive reviews on human health hazards of nanocellulose have been conducted, this paper brings new insights as it systematically analyzes and quantitatively assesses the results of in vivo and in vitro tests in terms of investigated endpoints, tested concentration ranges, physicochemical properties, surface modifications and source of the tested nanocellulose, exposure route, and cell lines used. The quality of the studies is further inspected based on various established criteria. Considering the rapid development of nanocellulose-based products and the novelty of the material, human health studies remain scarce. By assessing those that have been conducted, patterns and gaps were identified that will be helpful to guide future research. The results show that there are still significant uncertainties remaining, particularly regarding in vivo testing, with pulmonary exposure showing some cause for concern. Although a substantial number of in vitro studies have been undertaken, results are often conflicting. The detected effects could not be directly attributed to size of nanoparticles, cell lines, surface modifications or tested concentrations. This may also be linked to the varying quality of the studies. This review ends by identifying key gaps to help pave the way for future research and ensure the safe development and use of nanocellulose.

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Nano-photocatalysts are known for their ability to degrade pollutants or perform water splitting catalyzed by light. Being the key functional ingredients of current and future products, the potential of nano-photocatalysts releasing into the environment and causing unintended harm to living organisms warrants investigation. Risk assessment of these materials serves as an important step to allow safe implementation and to avoid irrational fear. Using TiO2 and g-C3 N4 as representative nano-photocatalysts, this study evaluates their hazard potential in zebrafish. Under simulated solar light, nano-photocatalysts up to 100 mg L-1 show no acute toxicity to zebrafish embryos due to the protection of chorions. The short-lived reactive oxygen species generated by nano-photocatalysts only exert injury to the hatched larvae at and above 50 mg L-1 . The input of solar energy, determined by the depth of water, irradiation time, and light intensity, greatly influences the toxicity outcome. Increasing concentrations of natural organic matters contribute positively to the hazard potential at 0-10 mg L-1 while gradually diminishing the hazardous effect above 10 mg L-1 . This study demonstrates the importance of nano-bio interactions and environmental exposure conditions in determining the safety profile of nano-photocatalysts.

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Natural and human-induced seabed sediment disturbances affect wide areas of the global coastal ocean. These recurrent to chronic disturbances mobilize significant amounts of material, including substances that have the potential to significantly harm the environment once re-released. This very challenging issue is difficult to deal with if sub-surface contaminant concentrations are unknown. Based on the analysis of 11 new, up to 5-m long sediment cores taken offshore in the Gulf of Cadiz, the contamination history (using the trace elements lead and zinc) is well documented over major parts of the gulf. Ore mining and metal processing industries on the southwestern Iberian Peninsula started five thousand years ago and experienced a first peak during the Roman Period, which can be detected over the entire gulf. The Industrial Era added a massive, shelf-wide heavy metal excursion of unprecedented dimension. This metal contamination to the coastal ocean decreased in the 1990s and appears to be today limited to larger areas off the Tinto/Odiel and Guadiana River mouths. The unforeseen, significant finding of this study is that the gulf-wide, peak heavy metal concentration, stemming from the Industrial Era, is widely overlain by a modern sediment veneer just thick enough to cover the contaminant horizon, but thin enough to have this layer within the reach of natural or human-induced sediment mobilization events.

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