How can contamination be prevented during laboratory analysis of atmospheric samples for microplastics?

Abstract

Microplastics (MPs) in the air and indoor environments are of growing concern and have led to increased testing for MPs. This study draws attention to the quality and quantitative measures of MP studies by conducting laboratory experiments (on solutions, filters, and blank samples) that were rarely or were not adopted in the airborne and indoor MP literature. Experiments have been conducted to identify contaminations that may come from experimental procedures while determining MPs in the air samples. MPs in different matrices during experiments were counted and categorized by their shapes. Chemical characterization was performed by Raman Spectroscopy. Results showed that laminar flow is the best option over a fume hood or standard laboratory environment for detecting air MPs to reduce blank levels. Blue-green and Black-Grey were the dominant colors; fiber was the predominant type of MPs seen, and most of them fall under the size range from (1-1000µm) in different indoor environments and blanks. Common MPs seen were PP, PVA, PTFE, PVC, and HDPE. Thermal treatment of fresh unused filters at 450°C for 4h was effective as it reduced the MP count by 50%. Working solutions are mainly contaminated, and their pre-filtration is essential. The average deposition of MPs in blank samples during seven days was around 55 MPs. There is an urgent need for studies on developing quality control and quality assurance of airborne and indoor MPs. Hence, a standard protocol needs to be accepted; by harmonizing procedures, comparable results can be found, uncovering the correct levels of MP contamination, as required for risk assessment.