An investigation into the stability and degradation of plastics in aquatic environments using a large-scale field-deployment study.

The fragmentation of plastic debris is a key pathway to the formation of microplastic pollution. These disintegration processes depend on the materials' physical and chemical characteristics, but insight into these interrelationships is still limited, especially under natural conditions. Five plastics of known polymer/additive compositions and processing histories were deployed in aquatic environments and recovered after six and twelve months. The polymer types used were linear low density polyethylene (LLDPE), oxo-degradable LLDPE (oxoLLDPE), poly(ethylene terephthalate) (PET), polyamide-6 (PA6), and poly(lactic acid) (PLA). Four geographically distinct locations across Aotearoa/New Zealand were chosen: three marine sites and a wastewater treatment plant (WWTP). Accelerated UV-weathering under controlled laboratory conditions was also carried out to evaluate artificial ageing as a model for plastic degradation in the natural environment. The samples' physical characteristics and surface microstructures were studied for each deployment location and exposure time. The strongest effects were found for oxoLLDPE upon artificial ageing, with increased crystallinity, intense surface cracking, and substantial deterioration of its mechanical properties. However, no changes to the same extent were found after recovery of the deployed material. In the deployment environments, the chemical nature of the plastics was the most relevant factor determining their behaviours. Few significant differences between the four aquatic locations were identified, except for PA6, where indications for biological surface degradation were found only in seawater, not the WWTP. In some cases, artificial ageing reasonably mimicked the changes which some plastic properties underwent in aquatic environments, but generally, it was no reliable model for natural degradation processes. The findings from this study have implications for the understanding of the initial phases of plastic degradation in aquatic environments, eventually leading to microplastics formation. They can also guide the interpretation of accelerated laboratory ageing for the fate of aquatic plastic pollution, and for the testing of aged plastic samples.

Leaching and transformation of chemical additives from weathered plastic deployed in the marine environment.

Plastic pollution causes detrimental environmental impacts, which are increasingly attributed to chemical additives. However, the behaviour of plastic additives in the marine environment is poorly understood. We used a marine deployment experiment to examine the impact of weathering on the extractables profile, analysed by liquid chromatography-mass spectrometry, of four plastics at two locations over nine months in Aotearoa/New Zealand. The concentration of additives in polyethylene and oxo-degradable polyethylene were strongly influenced by artificial weathering, with deployment location and time less influential. By comparison, polyamide 6 and polyethylene terephthalate were comparatively inert with minimal change in response to artificial weathering or deployment time. Non-target analysis revealed extensive differentiation between non-aged and aged polyethylene after deployment, concordant with the targeted analysis. These observations highlight the need to consider the impact of leaching and weathering on plastic composition when quantifying the potential impact and risk of plastic pollution within receiving environments.

Impact of accelerated weathering on the leaching kinetics of stabiliser additives from microplastics.

The release of additives from microplastics is known to harm organisms. In the environment, microplastics are exposed to weathering processes which are suspected to influence additive leaching kinetics, the extent and mechanism of which remain poorly understood. We examined the impact of weathering on stabiliser additive leaching kinetics using environmentally relevant accelerated weathering and leaching procedures. Nine binary polymer-additive formulations were specifically prepared, weathered, analysed, and evaluated for their leaching characteristics. Cumulative additive release (Ce) varied widely between formulations, ranging from 0.009 to 1162 µg/g. Values of Ce generally increased by polymer type in the order polyethylene terephthalate < polyamide 6 < polyethylene. The change in leaching kinetics after accelerated weathering was incongruous across the nine formulations, with a significant change in Ce only observed for three out of nine formulations. Physicochemical characterisation of the microplastics demonstrated that additive blooming was the primary mechanism influencing the leaching response to weathering. These findings highlight the dependency of additive fate on the polymer type, additive chemistry, and the extent of weathering exposure. This has significant implications for risk assessment and mitigation, where the general assumption that polymer weathering increases additive leaching may be too simplistic.

Solving a microplastic dilemma? Evaluating additive release with a dynamic leaching method for microplastic assessment (DyLeMMA).

Microplastics and plastic additives are contaminants of emerging environmental concern. Static leaching methods are commonly applied to assess the rate and extent of additive release from microplastics. However, this approach may not be representative of environmental conditions where near infinite dilution or percolation commonly occur. We evaluated three different approaches for assessing additive leaching under environmentally relevant sink conditions, culminating in the refinement and validation of DyLeMMA (Dynamic Leaching Method for Microplastic Assessment). Analysis was performed using a high-resolution liquid chromatography-mass spectrometry method enabling targeted quantification of additives and screening for non-intentionally added substances. Using four different plastics, sink conditions were maintained over the duration of the test, thereby avoiding solubility limited release and ensuring environmental relevance. Background contamination from ubiquitous additive chemicals was minimised, thereby providing good sensitivity and specificity. Resulting data, in the form of additive release curves, should prove suitable for fitting to release models and derivation of parameters describing additive leaching from microplastics.Key attributes of DyLeMMA:•Environmentally relevant dynamic leaching method for microplastics, demonstrated to maintain sink conditions over the test duration,•Simple, fast, and cost-effective approach without complication of using a solid phase sink,•Provide data suitable for understanding microplastic leaching kinetics and mechanisms.

Leaching and extraction of additives from plastic pollution to inform environmental risk: A multidisciplinary review of analytical approaches.

Plastic pollution is prevalent worldwide and has been highlighted as an issue of global concern due to its harmful impacts on wildlife. The extent and mechanism by which plastic pollution effects organisms is poorly understood, especially for microplastics. One proposed mechanism by which plastics may exert a harmful effect is through the leaching of additives. To determine the risk to wildlife, the chemical identity and exposure to additives must be established. However, there are few reports with disparate experimental approaches. In contrast, a breadth of knowledge on additive release from plastics is held within the food, pharmaceutical and medical, construction, and waste management industries. This includes standardised methods to perform migration, extraction, and leaching studies. This review provides an overview of the approaches and methods used to characterise additives and their leaching behaviour from plastic pollution. The limitations of these methods are highlighted and compared with industry standardised approaches. Furthermore, an overview of the analytical strategies for the identification and quantification of additives is presented. This work provides a basis for refining current leaching approaches and analytical methods with a view towards understanding the risk of plastic pollution.

Synthesis of graft copolymers of chitosan-poly(caprolactone) by lipase catalysed reactive extrusion.

Chitin is an abundant natural polymer and its deacetylated derivative chitosan has been a focus for the development of biobased, biocompatible and antimicrobial materials. In this work, a green and scalable route to grafting polycaprolactone (PCL) to chitosan using an enzyme catalysed reactive extrusion process is described. FTIR, 1H and 13C NMR spectroscopy and HSQC analysis confirm grafting of PCL to chitosan and show differences in the grafting pattern obtained using two commercially produced lipase enzymes from Candida antarctica (CALB® and NovoCor®). The thermostable NovoCor enzyme gave a much higher grafting yield (96.3%) than the less thermostable CALB enzyme (5.90%). In the esterification reaction, CALB preferentially catalyses reaction on primary OH groups at the C-6 position of chitosan, whereas NovoCor catalyses on the secondary OH groups of chitosan at the C-3 position. This is related to the differences in the selectivity of the two lipase enzymes. The control synthesized without enzyme did not show any grafting reaction. The degree of crystallinity and thermal stability of the lipase catalysed copolymer was reduced compared to unmodified chitosan. Moreover, the PCL grafted chitosan produced by a solvent free reactive extrusion route retained antimicrobial property against E.coli. Such grafted co-polymers may have applications in the controlled release coatings and tissue culture surfaces.

Green route to modification of wood waste, cellulose and hemicellulose using reactive extrusion.

A large volume of wood waste is produced in timber processing industry which traditionally used in low value applications. Here, value addition to the wood waste (Sander dust) and cellulose, hemicellulose isolated thereof by functionalisation using cyclic anhydrides in a solvent-free and green reactive extrusion process is reported. The effect of extrusion temperature, catalyst and different weight ratios of Sander dust (SD):succinic anhydride (SA) on the esterification reaction is evaluated. The esterified products were characterised by the acid value, degree of substitution (DS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), solid state (13)C NMR and thermo-gravimetric analysis (TGA). Under optimum extrusion conditions, mixed esters are formed, with highest acid value obtained for succinylation of cellulose (0.122 g/g at DS of 0.350) which is two times higher compared to succinylated SD (0.059 g/g at a weight gain of 0.452) and hemicellulose (0.043 g/g at DS of 0.290). The reactivity trend for individual anhydride was: (1) SA-Cellulose>SD>hemicellulose; (2) maleic anhydride (MA)-SD>hemicellulose>cellulose and (3) dodecenyl succinic anhydride (DDSA)-SD ≈ cellulose ≫ hemicellulose. The pendant free carboxyl groups generated through functionalisation of wood waste, cellulose and hemicellulose without the presence of polymeric carriers will allow more tailored or targeted modification of wood-plastic composites.

The effectiveness and adverse events of morphine versus fentanyl on a physician-staffed helicopter.

BACKGROUND: Morphine and fentanyl are both frequently used in prehospital trauma patients, but due to limited formulary size, we sought to study whether both drugs should be included. OBJECTIVES: The purpose of this study was to evaluate the effectiveness and safety of fentanyl as compared to morphine for patients requiring analgesic medications for a traumatic injury during transport via a physician-staffed air medical service. METHODS: Trauma patients were grouped by even and odd days (even - morphine 4 mg, odd - fentanyl 50 µg). Patients were excluded based on age (< 18 or > 64 years), hypotension, inability to communicate a pain score (intubated), or known allergy to the study drugs. During the flight, medical crew assessed numeric pain score, vital signs, and incidence of pruritis or nausea. RESULTS: There were 103 patients enrolled in the morphine arm and 97 patients in the fentanyl arm. The mean pain score at the beginning of enrollment was 8.0 ± 2.0 in the morphine arm and 8.0 ± 1.8 in the fentanyl arm. The mean final pain score was 5.8 ± 2.7 in the morphine arm and 5.5 ± 2.4 in the fentanyl arm (n.s. by either t-test or non-parametric testing). There was no significant difference in analgesia between fentanyl and morphine. There were no significant differences in the incidence of pruritis or vomiting between the two groups. Average transport time was 37 ± 8 min in the morphine group, and 43 ± 11 min in the fentanyl group. Average number of morphine doses was 3 ± 1.2. For fentanyl, average number of doses was 3 ± 1.3. CONCLUSION: In our study, there was not a significant difference in analgesic effectiveness between morphine and fentanyl. There was no significant difference in the incidence of adverse effects between the two drugs. Our study suggests that either drug can be used safely with equivalent effectiveness.

'Making a difference': A new care paradigm for pregnant and parenting Aboriginal people.

OBJECTIVE: To describe community-based stakeholders' views of how safe and responsive care "makes a difference" to health and well-being for pregnant and parenting Aboriginal people. Community-based stakeholders included community members, providers of health and social care, and health care and community leaders. METHODS: A postcolonial standpoint, participatory research principles and a case-study design were used to investigate two Aboriginal organizations' experiences improving care for pregnant and parenting Aboriginal people. Data were collected through researcher field notes, exploratory interviews and small group discussions with purposively selected community-based leaders, members and providers. Data were analyzed using an interpretive descriptive method. RESULTS: Community participants' views of "making a difference" emphasized: recognizing relevant outcomes of care; acknowledging progress over time; and using a strengths-based approach in which providers appreciate individuals' efforts and the challenges of their contextual circumstances. DISCUSSION: "Making a difference" to pregnant and parenting Aboriginal people would facilitate Aboriginal peoples' efforts to tackle the deeply embedded socio-historical determinants of well-being and capacity, and thus shift priorities for care upstream to focus on such determinants. Such a paradigm for care would integrate multiple perspectives on desirable outcomes within local frameworks based on values and priorities of Aboriginal parents, while also incorporating the benefits and wisdom of existing yet further downstream approaches to care. CONCLUSION: Design and evaluation of care based on community values and priorities and using a strengths-based approach can improve early access to and relevance of care during pregnancy and parenting for Aboriginal people.