Characteristics Of Indoor Airborne Microplastics Pollution In Poly (Ethylene:Propylene:Diene) Rubber Industry And Human Exposure Risk Assessment

Background As an emerging pollutant,microplastics(MPs)are pervasive in the environment and the plastics themselves are potentially toxic,the problem of MPs pollution has garnered widespread attention from people from all walks of life.However,there are still knowledge gaps in the study of airborne MPs pollution characteristics and exposure risks in indoor places,and research on airborne MPs in occupational places is still very limited,especially in the rubber industry.In order to provide a scientific reference for indoor airborne MPs pollution and occupational exposure risk in this industry,this study is based on the following:(1)investigating the abundance,size,shape,and polymer composition of indoor air MPs in different occupational sites in the EPDM rubber industry;(2)analyzing the relationship between air MPs and production processes;and(3)estimating the amount of trans-air exposure to MPs for different occupational personnel.Methods An auto parts company in Wuhu,where synthetic rubber is used as the raw material,was chosen as the study location.A total of 27 air MPs samples were taken using intelligent medium-flow TSP samplers in three workshops(a refining workshop,an extrusion workshop,and a post-processing workshop),as well as one administrative office,where various production activities were conducted in accordance with"GBZ/T159-2017 Specifications of air sampling for hazardous substances monitoring in the workplace".Following a series of pre-treatments,including ablation,the physical properties of MPs were evaluated using Nile red staining and fluorescence microscopy images,and the determination of the chemical makeup of MPs was carried out using micro-Fourier transform infrared spectrometry.The respiratory parameters were referred to the“Chinese Handbook of Population Exposure Parameters”to estimate the exposure to air MPs through the respiratory route for different occupational groups in this industry based on the formulas currently in use for the exposure to airborne MPs.Results(1)We detected MPs in indoor air samples from three rubber industry production workshops and one administrative office.Air MPs at all indoor sites exhibited a predominant small size(<100μm)and fragmentation pattern.The post-processing workshop among the production workshops had the highest abundance of MPs in indoor air(559±184 n/m~3).MPs were more prevalent in the workplaces where production activities took place,such as the refining workshop,extrusion workshop,and post-processing workshop,than in the office(360±61 n/m~3).(2)In terms of polymer types,a total of 40 types of MPs were found in the air of indoor places in this study.There were 28 different types of MPs found in the indoor air of the extrusion workshop with complex production processes.The types of MPs were related to the production processes,such as the highest proportion of injection materials ABS in the post-processing workshop,a higher proportion of EPDM rubber in the extrusion workshop than in other workplaces,indoor air MPs in the refining workshop where AHCR is used as adhesives is dominant,and administrative office air MPs are found in addition to packaging materials PS and synthetic fiber RY and raw material components related to the process,such as EPDM.(3)Based on the formula for inhalation of airborne MPs,the population in this study at high risk of exposure to airborne MPs in indoor were males aged 18～44,with average daily exposures ranging from 2,215 to3,429 MPs/day.Office workers were thought to breathe in between 456,786 and575,675 MPs annually via the respiratory route,whereas manufacturing floor workers were thought to be exposed to between 566,364 and 1,069,702 MPs annually via the respiratory route.Conclusions The abundance of indoor air MPs at occupational sites in the rubber industry in this study was higher than at other indoor sites in similar studies,and production activities in this industry may generate high concentrations of microplastics released into the air.The abundance and sources of air MPs in different indoor places are mainly related to production activities and raw materials,and the risk of air MPs exposure is higher for occupational workers in production workshops than for administrative office staff.The results of these studies provide useful references and important support for the monitoring and mitigation of air MPs pollution in occupational sites in the EPDM rubber industry.