Quantification and characterization of microplastics in coastal environments: Insights from laser direct infrared imaging.

The study identified and quantified nine plastic polymers frequently detected in the environment by collecting sediment and seawater samples from coastal areas in Auckland, New Zealand. Polymer types, size distributions, and number of microplastics (MPs) were analyzed using a laser direct infrared (LDIR) imaging technique. Compared to conventional spectroscopic or microscopic methods, LDIR enabled capturing and quantifying MPs in much lower size ranges (20-5000 µm). The results demonstrated the widespread occurrence of MPs in the Auckland coastal environment, with polyethylene terephthalate (PET) being the most frequently detected plastic polymer. MP contamination levels ranged from 13 to 83 particles per liter of coastal water and from 1200 to 3400 particles/kg of dry sand in beach sediments. Six additional locations were investigated to assess the contribution of MPs from stormwater drains to the coastal environment. The total count of identified MPs extracted from sediments near stormwater drains reached a maximum of 18,000 particles/kg of dry sand, representing an order of magnitude increase compared to MP levels found in beach sediments at the same location. In contrast to the prevalence of PET and polyamide observed in beach sediments and coastal waters, polyurethane and polyethylene emerged as the predominant plastic polymers in the vicinity of stormwater drain sediments, implying that the variation could potentially stem from distinct sources of plastics. This significant disparity in quality and quantity underscored the potential link between urban runoff and MP pollution in marine ecosystems. A sample preparation method using 100 g sediment samples was developed and used to assess and compare MPs detection in sediment samples. The commonly used 5 g sample method showed higher extraction efficiency and better detection of the most abundant MPs, but the new 100 g method enabled the detection of previously missed, less abundant plastics.

Quantifying environmental emissions of microplastics from urban rivers in Melbourne, Australia.

This study aims to understand the amount and type of microplastics flowing into Port Phillip Bay from urban rivers around Melbourne. Water samples were collected from the Patterson, Werribee, Maribyrnong, and Yarra Rivers, which contribute 97 % to the total flow into Port Phillip Bay. On average, the rivers contained a mean of 9 ± 15 microplastics/L and ranged from 4 ± 3 microplastics/L (Patterson) to 22 ± 11 microplastics/L (Werribee). Of the eight polymers investigated, polyamide and polypropylene were the most frequently detected polymers. Using the mean concentration of each river, the flow of microplastics into Port Philip Bay was estimated to be 7.5 × 106 microplastics per day and 3.7 × 1010 microplastics per year. To fully understand the fate and transport of microplastics into Port Phillip Bay, this study would be the foundation for a more in-depth investigation. Here, further samples will be collected at more points along the river and at the midpoint of each season.

Assessing exposure of the Australian population to microplastics through bottled water consumption.

The presence of microplastics in the environment is substantially documented; however, the pathways of dietary exposure to microplastics are not yet well understood. This is the first study to document the presence of microplastics in bottled water sold in Australia from commercial outlets. In total, 16 brands of bottled water (Australian Sourced: n = 11, Imported: n = 5) sold in the two largest supermarkets in Australia were analysed in triplicate (n = 48) for the presence of polyethylene, PE; polystyrene, PS; polypropylene, PP; polyvinyl chloride, PVC; polyethylene terephthalate, PET; polycarbonate, PC; polymethylmethacrylate, PMMA; and polyamide, PA. Microplastics were detected in 94% (n = 15) of the samples, with PP (n = 14, 88%), PET (n = 10, 63%), PA (n = 7, 44%), and PE (n = 6, 38%) the most frequently detected. On average, a litre of bottled water contained 13 ± 19 (St Dev) microplastics, ranging from 0 to 80 microplastics/L. The average size of the microplastics identified in this study was 77 ± 22 µm. It was found that bottled water sourced and packaged overseas contained four times as many microplastics compared to bottled water sourced in Australia. It was estimated that in 2017, 28.3% of the Australian population consumed on average 30.8 L of bottled water; therefore, using the result from this study it is estimated that Australians are exposed to 400 microplastics annually through the consumption of bottled water. To understand the total amount of microplastics that Australians could be exposed to through dietary routes, further work is required to observe the presence of microplastics in other beverages and food.

Microplastic contamination of an unconfined groundwater aquifer in Victoria, Australia.

This is the first study to show microplastics contamination in an alluvial sedimentary aquifer that has been capped from the atmosphere. Microplastics are often reported in biotic and abiotic environments, but little is known about their occurrence in groundwater systems. In this study, eight of the most commonly found microplastics in the environment (polyethylene, PE; polystyrene, PS; polypropylene, PP; polyvinyl chloride, PVC; polyethylene terephthalate, PET; polycarbonate, PC; polymethylmethacrylate, PMMA; and polyamide, PA) were analysed in triplicate groundwater samples (n = 21) from five sampling sites across seven capped groundwater monitoring bores from Bacchus Marsh (Victoria, Australia) using Agilent's novel Laser Direct Infra-Red (LDIR) imaging system. Microplastics were detected in all samples, with PE, PP, PS and PVC detected in all seven bores. The average size of the microplastics identified was 89 ± 55 µm (St.Dev.), ranging from 18 to 491 µm. The average number of microplastics detected across all sites was 38 ± 8 microplastics/L, ranging from 16 to 97 particles/L. PE and PVC in total contributed to 59% of the total sum of microplastics detected. PE was consistently detected in all seven bores (average: 11 particles/L), while PVC was more pronounced in a bore adjacent to a meat processor (52 particles/L) compared to that of its overall average of 12 particles/L. A statistically significant positive correlation was observed between PVC and PS (R = 0.934, p ≤0.001). As this study collected samples from capped groundwater bores, the most probable avenue for microplastics was permeation through soil. Therefore, to further understand the fate and transport of microplastics within a groundwater system, it is necessary to analyse a greater range of groundwater bores not only from Australia but throughout the world.

Current practices underestimate environmental exposures to methamphetamine: inhalation exposures are important.

Current practice for determining the exposure to methamphetamine in contaminated homes relies on the analysis of surface wipe sample to address direct contact exposures. The movement of methamphetamine into the air phase, and the potential for inhalation exposures to occur within residential homes contaminated from former clandestine manufacture or smoking of methamphetamine has been generally poorly characterised and understood. All available risk-based guidelines for determining safe levels of methamphetamine in residential properties do not include any consideration of the inhalation pathway as an exposure route. This study showed that methamphetamine can readily move from contaminated materials in a home into the air phase. This movement of methamphetamine into the air phase provides both an exposure pathway and a mechanism for the transfer of methamphetamine throughout a property. The inhalation exposure pathway has the potential to result in significant intake of methamphetamine, adding to dermal absorption and ingestion exposure routes. Guidelines that are established for the assessment of methamphetamine contaminated properties that ignore inhalation exposures can significantly underestimate exposure and result in guidelines that are not adequately protective of health. This study also demonstrates that sampling methamphetamine in air can be undertaken using commercially available sorption tubes and analytical methods.

Assessing urinary levoglucosan and methoxyphenols as biomarkers for use in woodsmoke exposure studies.

A major contributor to particle concentrations in urban airsheds is domestic woodsmoke and smoke arising from wildfires or management burns. Particle concentrations in urban airsheds have been associated with a wide range of health effects. There has been little research into the contribution of biomass burning to studies of human health due to the complexity of attributing effects in the presence of multiple sources of pollutants and the variability in the nature and conditions of biomass burning. A significant advance is the use of biomarkers of exposure; methoxyphenol and levoglucosan; specific compounds produced following the combustion of lignins and detected in urine. Levoglucosan has not previously been assessed for its usefulness as a marker of human exposure. We report for the first time levoglucosan concentrations in urine. Twelve participants were recruited and asked to provide spot urine samples pre- and post-exposure to a fire training exercise. Both levoglucosan and methoxyphenol were detected in the urine of participants. There was no significant increase in these compounds post-exposure to smoke arising from the fire training. Further work is required to assess this biomarker for human exposure studies and in particular the role of diet and previous exposure.