Occurrence, human exposure, and risk of microplastics in indoor environments

Ageel, Hassan ORCID: 0009-0004-3136-8390 (2025). Occurrence, human exposure, and risk of microplastics in indoor environments. University of Birmingham. Ph.D.

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Abstract

Microplastics (MPs), tiny plastic particles less than 5 mm in size, have become a significant environmental concern due to their widespread presence and potential health impacts, especially in indoor sites. This thesis investigates MPs occurrence, concentrations, and characteristics (i.e., size, shape, and polymer type) in indoor air (airborne and atmospheric deposition) and settled indoor dust in Birmingham, UK. The measured MPs concentrations are then used to estimate exposure of UK adults and toddlers to MPs via inhalation and inadvertent dust ingestion in UK homes and workplaces for the first time. Moreover, potential seasonal variation in indoor MPs concentration and estimated daily intakes were studied for the first time, over a 12-month monitoring period in 5 indoor microenvironments. In this thesis, analytical protocols have been developed and quality assured to minimize contamination during sampling/clean-up stages and accurately determine MPs in indoor air and dust samples. A digital fluorescence microscope has been applied to determine the size, shape, and count of MPs particles as physical properties. Additionally, Fourier-Transform Infrared Spectroscopy (μ-FTIR) was applied to identify the polymer types as chemical properties. The analyses revealed the presence of fibers, fragments, and foams of varying sizes. Polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polypropylene (PP) were identified as the most prevalent polymer types in the studied samples. Particles in the size range (10 – 50 μm) were the most abundant in airborne MPs, while larger MPs (50 – 100 μm) were more frequently detected in atmospheric deposition and settled indoor dust samples.
The study of MPs in UK indoor air and inhalation exposure via active and passive air sampling from 30 homes and 30 workplaces is the first and most comprehensive study in this scope. 120 samples were investigated, and the mean concentrations of MPs in UK homes were significantly higher (P<0.05) than those in workplaces for both active and passive air samples. Airborne MPs concentrations were observed in homes (15.6 ± 5.4 MPs/m3) compared to workplaces (13.1 ± 6.5 MPs/m3). For atmospheric deposition samples, the average MPs concentrations were 3735 ± 1343 MP/m2/day in homes and 3177 ± 1860 MP/m2/day in workplaces. Similarly, higher concentrations of MPs were measured in settled indoor dust from homes (155 ± 222 MPs/mg), compared to workplaces (125 ± 209 MPs/mg) sampled in the present study. This was mainly attributed to carpeting, where all the sampled homes were carpeted, while 13 of the studied workplaces were uncarpeted.
The seasonal variation study revealed statistically significant differences (P < 0.05) in mean concentrations of MPs in indoor air and settled dust among the studied seasons for the first time. All sampling locations experienced the highest concentrations of MPs during the summer months, while significantly lower levels were observed in autumn and spring, which was reflected in significantly different estimated daily intakes of MPs in different seasons. This is of particular importance to exposure and risk assessment studies because it raises concern over the representativity and comparability of existing human exposure data from different studies based on single “spot” samples collected from various indoor microenvironments in different seasons.
Overall, Estimated daily intakes of UK toddlers to MPs were substantially higher than those for adults via both inhalation and inadvertent dust ingestion in all seasons and using different exposure scenarios. The is of concern due to toddlers’ incompletely developed immune and nervous systems. Therefore, more effort and prompt actions are required to reduce MPs levels in UK indoor microenvironment to protect our population, particularly vulnerable groups like toddlers, from potential risks associated with exposure to MPs indoors.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):