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Magnetic Nanosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
Microbeads are uniformly sized particles, typically 0.5–500 μm in diameter. Bio-reactive molecules can be adsorbed or coupled to their surface, and used to separate biological materials such as cells, proteins, or nucleic acids. Baselt et al. (1998) conducted a proof-of-concept biosensor experiment, showing the worth of using GMR sensors with magnetic microbeads in a Bead ARray Counter (BARC). An array of 80 μm × 5 μm GMR sensor elements was fabricated from sandwich GMR material. Each sensor was coated with different biological molecules that bound to different materials to be assayed. The magnetic microbeads were also coated with the materials to be analyzed. The microbeads in suspension were allowed to settle onto the GMR sensor array where specific beads will bond to specific sensors only if the materials are designed to attract each other. Non-binding beads were removed by a small magnetic field. The beads were then magnetized at 200 Hz by an AC electromagnet. The 1-μm microbeads were made up of nm-sized iron oxide particles, which had little or no magnetization in the absence of an applied field. A lock-in amplifier extracted the signal at twice the exciting frequency from a Wheatstone bridge constructed of two GMR sensor elements, one of which was used as a reference, and two normal resistors. High-pass filters were used to eliminate offset and the necessity of balancing the two GMR sensor elements. With this detection system, the presence of as few as one microbead was detectable.
Waste Generation and Management
Published in Barry L. Johnson, Maureen Y. Lichtveld, Environmental Policy and Public Health, 2017
Barry L. Johnson, Maureen Y. Lichtveld
Microbeads are a special form of plastic waste that is a hazard to the health of ecosystems. These are tiny bits of plastic used as ingredients in exfoliating body washes and facial scrubs. Since their introduction in 1972, they have made their way into more than 100 personal care products. Microbeads are used in soaps because exfoliating products need small, hard particles to rub debris from the skin [89]. Microbeads range in diameter from 5 μm to 1 mm. They are made from synthetic polymers including polyethylene, polylactic acid, polypropylenepolystyrene, or polyethylene terephthalate. One group of researchers calculated that 8 trillion microbeads per day are emitted into aquatic habitats in the U.S. Further, the investigators estimate that the 8 trillion beads that make it into aquatic habitats are only 1% of the total release, which would amount to 800 trillion microbeads ending up in the sludgy runoff from sewage plants [90]. A study by Japanese investigators found the concentration of microplastics, defined as plastic particles up to 5 mm in diameter, is higher in sediment than in sea water, raising concerns that it could affect organisms living in and on the bottom of the ocean. The study examined samples of sediment collected from the sea floor and elsewhere in area that included Tokyo, Southeast Asia, and Africa [91]. As will be described in the next section, microbeads present a serious threat to the health of ecosystems.
Sources and demand for water
Published in Amithirigala Widhanelage Jayawardena, Fluid Mechanics, Hydraulics, Hydrology and Water Resources for Civil Engineers, 2021
Amithirigala Widhanelage Jayawardena
According to FAO’s AQUASTAT, around 3,928 km³ of water per year is withdrawn worldwide, of which 44% (1,716 km³ per year) is consumed and 56% (2,212 km³ per year) is released as wastewater. The wastewater includes agricultural drainage and municipal wastewater. Water reuse is done in many rivers around the world where wastes and wastewater are discharged into waterways at several upstream locations. In developed countries, the discharge of waste and wastewater is only after they have been treated to levels acceptable for release into rivers where water is tapped at downstream locations. In some developing countries where treatment facilities for waste and wastewater are unavailable or unaffordable, the raw waste and wastewater are discharged into watercourses at different upstream locations. In such cases, the downstream water is contaminated by bacteria, nitrates, phosphates and solvents, resulting in negative health and environmental consequences. Untreated wastewater in 2015 ranged from 30% in high income countries to a 92% in low income countries. The target in 2030 is to reduce these to 15% and 46%, respectively (WWDR, 2017). Of particular concern is the presence of microbeads in the waste water. They are found in certain consumer products, such as facial cleansers and toothpaste. After use, these spherical particles made of polyethylene or polypropylene end up in wastewater. Once microbeads enter the wastewater system, few wastewater treatment facilities are able to remove them from the water streams. Risks to aquatic life and public health are not yet well understood, but the particles themselves may contain toxins or attract other toxins in the water. The good news is that in recent years (2016–2018) governments of the US, Canada and UK have banned the use of microbeads in cosmetics and personal care products.
Plastic microbeads: small yet mighty concerning
Published in International Journal of Environmental Health Research, 2021
Shaima S. Miraj, Naima Parveen, Haya S. Zedan
There is a growing public support for banning micro beads and has prompted action from many multinational companies, policy makers, governing, and non-governing bodies. For instance, LOreal, Colgate, Procter & Gamble, Unilever, Target Corporation, Johnson & Johnson, The Body Shop have pledged to discontinue using microbeads in their personal care products and more than 70 NGOs from different countries are working on to have advocated legal action to ban microbeads from personal care products. In 2012, an international campaign ‘Beat the Microbeads’ has been launched by the Plastic Soup Foundation and the North Sea Foundation against microplastic ingredients used in personal care products. Several US states including Illinois, New Jersey, Maine, Maryland and Colorado and the province of Ontario in Canada have banned microbeads (Rochman et al. 2015). Numerous extant queries regarding the fate, persistence and hazards of microbeads can still be addressed via more common investigations of micro plastic debris. Microplastics of the same size and shape as microbeads are constant, impractical to eradicate, and have negative effects on aquatic organisms. According to Guerranti et al. (2019), the chances of risk from microbead pollution are more, and the solution to this dilemma is simple. Banning micro beads from products that enter wastewater will eventually protect water quality, wildlife, and resources used by people. Microplastics containing products are not only banned in some countries but a general ban is necessary (Guerranti et al. 2019).
The occurrence and degradation of aquatic plastic litter based on polymer physicochemical properties: A review
Published in Critical Reviews in Environmental Science and Technology, 2018
Tom Bond, Veronica Ferrandiz-Mas, Mónica Felipe-Sotelo, Erik van Sebille
Much of plastic litter is comprised of microplastics, typically defined as particles <5 mm in diameter (GESAMP, 2016). Plastics designed to be this size are referred to as primary microplastics, whereas secondary microplastics result from the fragmentation of larger pieces of plastic. Primary microplastics include microbeads used in cosmetic and cleaning products. The US has pledged to phase out use of microbeads in cosmetics and personal care products by 2019 (ChemistryWorld, 2016), while the UK government has announced plans to ban microbeads by the end of 2017 (BBC, 2016).