Assessing microplastic characteristics in bottled drinking water and air deposition samples using laser direct infrared imaging

Abstract

There is an urgent need for data on microplastics (MPs) in uptake media relevant to humans. Here we apply Laser Direct Infra-Red (LDIR) spectroscopy for the rapid analysis of MP> 10 µm in clean matrices such as bottled drinking water and (deposited) air samples, using strict QA/QC criteria. Nine water bottles of three different brands were found to contain on average 96 particles/L (range 7–364, median 44 particles/L) with polymer abundances in the order polyethylene terephthalate and/or polyurethane > polyamide > polyvinylchloride. Further, for laboratory and household rooms, MP deposition rates were measured, ranging from 0 to 573 particles m−2 h−1. For household deposition samples, these rates translate to 7 MP (range 0–16) consumed in an average meal. Polyethylene terephthalate and/or polyurethane > polyamide > polypropylene were the most abundant polymers. We find a statistically significant positive relationship between the total surface area of textile per unit of room volume (m2/m3) and the deposition of MP. Power law distributions for particle width, height, area, volume and mass were constructed for both sample types, with slopes ranging from 1.9 to 3.8. LDIR appears to be a relatively fast MP measurement method, with MP recovery during sample preparation as a potential improvement point.