Discovery and analysis of microplastics in human bone marrow
September 15, 2024 | ScienceDirect
Abstract
The health implications of human exposure to microplastics (MPs) have raised significant concerns. While evidence indicates MPs can accumulate in closed human organs like the heart, placenta, and blood, there is no available data on MP exposure specifically within the human bone marrow. To fill the research gap, this study detected the concentration of microplastics (MPs) in bone marrow samples by pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) and assessed the size range and morphological characteristics of MPs by Laser Direct Infrared Spectroscopy (LD-IR) and scanning electron microscopy (SEM). Our study shows that MPs were present in all 16 bone marrow samples, with an average concentration of 51.29 µg/g ranging from 15.37 µg/g to 92.05 µg/g. Five polymer types-polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC), polyadiohexylenediamine 66 (PA66), and polypropylene (PP), were identified. PE was the most frequent polymer detected in the bone marrow, with an average concentration of 30.02 µg/g ranging from 14.77 µg/g to 52.57 µg/g, with a detection rate of 93.75 %. PS had the highest detection rate at 100 % of bone marrow samples, while PVC and PA66 were found in 75 % of samples each. LD-IR analysis revealed the identification of 25 polymer types, with an average abundance of 19.72 particles/g. Of these, 89.82 % of the MPs were smaller than 100 µm. In summary, this study has, for the first time, demonstrated the presence of MPs are deeply embedded within human bone marrow, providing a basis for future investigations into their potential toxicological effects and underlying mechanisms affecting the hematopoietic system.
Introduction
The world is facing a critical environmental challenge due to plastic pollution, with 6 billion tons of microplastics (MPs) currently present. In 2019, 353 million tons of plastic waste were generated, which is anticipated to exceed 1 billion tons by 2060 [1], [2]. Waste plastics in the environment could decompose down into small particles [3]. In 2004, Thompson introduced the concept of MPs, which are plastic fragments and particles less than 5 millimeters in diameter [4]. Besides, microbeads, intentionally added into personal care products, are also important source of MPs. MPs can enter the human body through ingestion, inhalation, and skin contact [5], [6], raising significant concerns about their potential health risks.
Recent evidence indicates that MPs are present not only in human tissues that are directly contacting with the external environment, such as the lungs [7], sputum [8], alveolar lavage fluid [9], and faeces [10], [11], but also in completely enclosed human organs, such as the heart [12], placenta [13], and testis and semen [14]. Increasing evidence shows that MPs impact human health. MPs in human blood may accumulate in tissues and cause systemic body exposure [15]. Carotid artery plaque MPs have been linked to higher risks of myocardial infarction, stroke, or death [16], and faecal MPs are correlated with inflammatory bowel disease status [11]. Exposure to MPs may also affect probiotic taxa in preschool-aged children, disrupting gut microbiota [17]. Human exposure and toxicological hazard data are the prerequisite and data basis for the human health risk assessment [18]. Thus, there is an urgent need for more accurate assessments of MPs exposure and its potential health impacts.
Situated in the medullary cavity of long bones and all cancellous bone, bone marrow represents 3.5–5.9 % of adult body weight. As the largest haematopoietic organ, it is pivotal for hematopoiesis and immune defense [19], [20]. The bone marrow has a large blood sinus forming a network of capillaries, with the large space of endothelial cells in the blood sinuses facilitates the exchange between the bone marrow and blood [21]. The blood sinuses also promote the exchange of various harmful environmental substances in the bone marrow and peripheral region. Haematopoietic function disorders caused by environmental chemicals are the key factors in the occurrence of blood diseases [22]. The toxic effects of MPs on mouse bone marrow haematopoietic function have been demonstrated [23]. Exposure to 0.1 mg and 0.5 mg of 5 µm polystyrene (PS)MPs inhibit colony-forming unit growth and affect gene expression in mouse bone marrow cells [24]. These MPs can also induce haematopoietic injury by disrupting the gut microbiota homeostasis, metabolism, and inflammation[23], [24]. Our earlier study found that PSMPs inhibited the proliferation and differentiation of human CD34 + haematopoietic stem/progenitor cells and disturbed metabolic activity, particularly targeting the citrate cycle [25]. However, previous studies have lacked effective population exposure data to support the selection of exposure doses, highlights the need for research into human exposure levels.
Pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) is an emerging thermal analysis technique that reliable qualified and quantified data for MPs risk assessment of human health [15], [26]. Laser direct infrared spectroscopy (LD-IR) has been widely used to characterize of MPs, including their type, size, and morphology [12]. This study utilized Py-GC/MS, LD-IR, and scanning electron microscopy (SEM) to analyze and identify the accumulation of MPs in the bone marrow. The results provide crucial data for evaluating the risks of MPs on human haematopoietic injury, and support further studies with larger sample sizes and more detailed designs to explore the health implications of MPs in human bone marrow.
