Effects of secondary microplastic on the respiratory system of BALB/c mice

Microplastics (MP) are ubiquitous in the environment, even being found in human organs such as the lungs and brain. In the environment, plastics are exposed to continuous processes which affect their structural integrity and result in their fragmentation. These secondary particles, while they may lose the compounds added during their production, can adsorb and absorb other compounds during the time they are exposed to the environment. We hypothesize that strutural and composition of the polymer may alter the toxicity of the MP. In this study, we evaluated the effects of naturally degraded polypropylene (PPs), PP primary (PPp) and the synergistic effect of PP with diesel exhaust particles (DEP) on the male mice lung function. BALB/c mice, 8 per group, received daily for 28 days 10 µL of saline solution containing 300 µg of PPs or PPp or 30 µg of DEP, or DEP and PPs or DEP and PPp. On the 29th day under anesthesia, the animals were anesthetized and tracheostomized for monitoring of lung function. The Kruskal-Wallis test followed by the Bonferoni test were used to test differences between groups. An increase (p>0.05) in the resistance and elastance response of the distal airways was observed in mice exposed to PPS (6.1+-0.82; 31.08+-4.82), DEP (6.64+-1.77; 34.28+-10.26), PPS+DEP (8.99+-5.66; 42.97+- 24.5) and PPp+DEP (6.42+-0.67; 36.06+-3.93), when compared to the control (6+-0.68; 30.32+-4.7). The results demonstrate that exposure of animals to PPs and DEP as well as the synergistic effect of PP and DEP caused a response associated with the distal regions of the mice's lungs, suggesting increase in the inflammatory process in this tissue, with the possible presence of edema.