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Characterising microplastics in indoor air: Insights from Raman imaging analysis of air filter samples
Cheng Fang1, Olalekan Simon Awoyemi2, Gopalan Saianand1
1Global Centre for Environmental Remediation (GCER), University of Newcastle, Callaghan, NSW 2308, Australia; CRC for Contamination Assessment and Remediation of the Environment (CRC CARE), University of Newcastle, Callaghan, NSW 2308, Australia.
Abstract:
We are directly exposed to microplastic contamination via indoor air that we breathe daily, for which the characterisation of microplastics is still a challenge. Herein, two typical air filter samples were collected, one from an air-conditioner and another from a personal computer, both of which have been working for around half a year to collect and accumulate microplastics in the indoor air, like microplastic banks. After the sample preparation to remove the mineral dusts, Raman imaging was employed to directly and simultaneously identify and visualise microplastics of polyethylene terephthalate (PET) fibres, distinguish them from other fibres such as cellulose and cross-check them with a scanning electron microscope (SEM). To count the microplastics and to avoid the quantification bias, several areas were randomly scanned and imaged to statistically estimate the percentage of microplastic fibres in the analysed samples. The microplastics amount, which has been estimated at 73-88,000 fibers per filter per half a year, varies and depends on the indoor environment so that the air filter can work as a good indicator to monitor the quality of the indoor air from the microplastic perspective. Overall, human are directly exposed to this emerging contamination every day, raising environmental concerns. Raman imaging characterisation and its corresponding statistical information can help pursue further research on microplastics.
Insights
Indoor air filters accumulate significant microplastics, with Raman imaging identifying polyethylene terephthalate (PET) fibers. Air filters can monitor indoor air quality, highlighting daily human exposure to microplastic contamination.
Area of Science:
- Environmental Science
- Analytical Chemistry
- Materials Science
Background:
- Microplastic contamination is a pervasive issue, with indoor air posing a direct exposure route for humans.
- Characterizing microplastics in complex matrices like indoor air filters remains a significant analytical challenge.
- Accumulation of microplastics in household appliances highlights their role as potential microplastic sinks.
Purpose of the Study:
- To develop and apply a method for the direct identification and quantification of microplastics in indoor air filters.
- To assess the potential of air filters as indicators for monitoring indoor microplastic pollution.
- To investigate the types and abundance of microplastics present in indoor environments.
Main Methods:
- Collection and preparation of air filter samples from an air-conditioner and a personal computer.
- Utilisation of Raman imaging for direct, simultaneous identification and visualization of polyethylene terephthalate (PET) fibers.
- Cross-validation with Scanning Electron Microscopy (SEM) and statistical analysis for quantification to avoid bias.
Main Results:
- Polyethylene terephthalate (PET) fibers were successfully identified and visualized using Raman imaging.
- Microplastic quantification revealed an estimated 73-88,000 fibers per filter over a six-month period.
- Microplastic abundance varied depending on the indoor environment, confirming air filters as potential monitoring tools.
Conclusions:
- Raman imaging provides an effective method for characterizing microplastics in air filters.
- Air filters serve as valuable indicators for assessing indoor air quality concerning microplastic contamination.
- Daily human exposure to indoor microplastics necessitates further research and environmental concern.
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