Global Indoor Dust Microplastics Exposure: Quantification and Risk Assessment

In recent years, significant focus has been given to microplastics in aquatic environments as an emerging contaminant. Conversely, much less attention has been given to its pervasive presence in the atmospheric environment, especially inside homes where people spend approximately 70% of their time. This global MP study measured and assessed their prevalence, source and type in atmospherically deposited dust in homes from 29 countries to evaluate human health exposure and risk. In 2019, 108 indoor dustfall samples were collected over a 1-month period and were analysed for their chemical composition using a Nicolet iN10 FTIR. Residential characteristics of each participants home were collected via a questionnaire. Approximately 99% of settled dust particles were fibres (synthetic, semi-synthetic and natural; the former classed as MP), with the highest proportion being between 200 to 400 m in length. Samples were categorised according to their location based on the following World Bank gross national income (GNI) categories: high income (HI), medium income (MI) and low income (LI) countries. Deposition rate of MP was highest in LI countries (3515±1187) versus MI (1268±373) and HI (1257±492) countries. Vacuum cleaner frequency use across GNI countries was significantly associated to lower MP loading rates. Synthetic fibres were the most prevalent MP, with 39% to 46% across HI and LI countries. Conversely, natural fibres predominated in MI countries. Polyamide and polyethylene terephthalate (polyester) fibres were present in the highest proportion in HI countries (Textiles). Polyurethane fibres were in the highest proportion in LI countries (furniture and flooring). The correlation analysis of deposited dust weight, MP deposition rate, and probable outdoor sources of MP revealed indoor sources of deposited dust and MP. Inhalation and ingestion rates were calculated for age groups, with younger ages determined to have greatest exposure. The weight percent of constituent monomers of found polymers have been assumed equal to deposition rate of polymers for risk assessment. Toddles across all GNI countries are at the highest health risk. Using socio-economic correlations with the data results, we identify the level of the economy as a likely influencing factor on people's health in the context of household dust MP.