First detection of μ-plastics in human urines and kidneys using μ-Raman spectroscopy

Microplastics (MPs) are defined as small plastic particles, measuring less than 5mm; it is possible to distinguish between primary MPs, produced as such, and secondary MPs, resulting from the breakdown of larger plastic products, or from the shedding of synthetic fibers, or the release from personal care products, in the form of microbeads. Due to their ubiquitous presence in different environments, such as oceans, freshwater, and even the air we breathe, MPs became one of the environmental issues of highest concern of the XXI century. Due to our constant exposure to the such contaminants, microplastics were already detected in human lung, liver, placenta, blood and breastmilk, thus pointing at an easy absorption and distribution of such particles in human body. However, health risks related to the assumption of MPs by mammals are still not well clarified, but it is commonly believed that, acting as foreign bodies, they could work as triggers for emerging diseases of unknown etiology, whose correlation with environmental exposure cannot be excluded. An epidemic of Chronic Kidney Disease (CKD) of uncertain etiology is emerging worldwide and then, to evaluate a possible involvement of MPs is crucial. To this end, in human urines and kidney the presence of MPs was investigated. We therefore analyzed properly digested urines (health individuals) and kidneys tissues (1-4 g from nephrectomies), looking for polymers or plastics additives, such as pigments. Analyses were performed using microRaman spectroscopy, a technique of election for the detection of microplastics, thanks to its high spatial resolution and sensitivity towards the presence of polymers and pigments. Our study confirmed the presence of plastic fragments (e.g. Figure 1) in both urines and kidneys, but also the presence of commonly employed pigments, such as hematite, laying the basis for further investigations on the mechanisms of excretion of these particles, and on their possible role in promoting kidney damage.