Atmospheric microplastics and the human lungs

Microplastics (MPs) are an emerging environmental contaminant (EEC), that have recently been isolated from samples collected from the atmosphere, and are considered ubiquitous on Earth. There is a lack of knowledge regarding the properties of atmospheric MPs (AMPs), in terms of location, concentrations, plastic types, sizes and shapes. There is also limited understanding of the potential for these MPs to be inhaled, and the consequences of such exposure. Standardised approaches throughout the AMP field are called for, because incomparable datasets and varying microplastic (MP) definitions are slowing down the progression of research. It is now necessary to thoroughly investigate AMPs, and gain knowledge of the location and MP types relevant to human exposure, as well as assessing MP inhalation as an exposure route for humans. This information can direct future investigations into the potential hazards associated with AMP inhalation.This thesis presents 3 publications, within this publication style thesis; investigating indoor AMPs, outdoor AMPs and a final investigation into the presence of MPs within human lung tissue samples, acquired from living patients.First, passive sampling of 20 households over a 6-month discontinuous duration, reported an average concentration of 1414 MP m− 2 day− 1 ± 1022 (mean ± SD). This high abundance of MPs within household environments supports the importance of indoor MP sampling locations. Fibrous and fragmented Polyethylene terephthalate (PET), Polypropylene (PP) and Nylon were also stated as relevant to human exposure, at head height.Secondly, passive sampling within a busy outdoor urban roadside location reported concentrations of MPs; 3055 ± 5072 MP m−2 day−1 (mean ± SD, 1164 median), over a yearlong investigation. Specific outdoor areas of high human activity were suggested to rival that of indoor concentrations. An additional snap-shot 2-week investigation, passively sampling 5 different areas of varying human activity, was also conducted. Roadside, commercial and industrial locations were reported with high concentration rates and relevance to human exposure. An abundance of film and fragmented particles, of Polyethylene (PE), Nylon and Resin composition, suggested these properties to be most relevant to human health studies.Finally, digested human lung tissue analysis provided evidence to support the human inhalation of MPs. 39 MPs were identified within 13 lung tissue samples, acquired from 11 living human patients. PP was reported within samples, after strict limit of detection and limit of quantification (LOD LOQ) adjustments were applied. PP, PET and Resin synthetic plastic types, and fibre and fragment shape categories were identified and suggested to be of relevance to human inhalation. The size of most MPs identified within lung tissue samples were larger than that thought possible to inhale, whilst some were smaller and traditionally more inhalable.These publications bridge environmental MP research and human MP health studies, providing much needed knowledge regarding the concentration and types of AMPs that humans are most likely exposed to on a daily basis, as well as supporting the potential for exposure to AMPs via inhalation. Uniquely, at the forefront of all publications, was the aim to provide novel, high quality methodologies, combatting methodological restrictions, and focusing considerably on improving the quality of research concerning AMPs and human exposure, with great emphasis on quality control. These chapters, alongside other AMP research, can form the foundations for future research improvements, leading to eventual standardised operating procedures (SOPs), policy formation, and to achieve guided, accurate and environmentally relevant MP exposure investigations.