Ecotoxicological Determination of Microplastic Toxicity on Algae Chlorella sp.: Response Surface Modeling Approach

An extensive use of plastic material, which is a characteristic of modern society, is increasing the amount of plastic waste in the environment. Accordingly, plastic pollution has become a global environmental problem. The problem is particularly related to microsized and nanosized plastic particles which have become environmental contaminants of emerging concern. This research was focused on ecotoxicological aspects of 5 the most common plastic substances: polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), and polyethylene terephthalate (PET); all substances were in form of microplastics. The used test organism was freshwater microalgae Chlorella sp. and inhibition of the algal growth after 3-day exposure was measured. The experimental domain included microplastics in range 10–1000 mg/L and sizes 100–700 µm. Response surface modeling was applied in order to analyze the influence of these two parameters and statistical analysis of the obtained models was performed. The significance level was 95%. The obtained inhibitions were relatively low (< 6.79%) but Chlorella sp. showed sensitivity to changes in both tested parameters. A general behavior that included inhibition increase with higher concentration values and lower particle sizes was observed. The exception was PP where only the concentration proved to be significant parameter; the influence of the particle size remained insignificant for the selected experimental domain. Hormesis appears likely in PE and PP cases at particle sizes and concentrations that are below the experimental domain. Determined adverse influence of the applied plastics followed the order: PVC > PET > PS > PE > PP.