Microplastics pollution - a qualitative material flow analysis

Abstract

The quantity of plastic released into the environment has grown considerably in the past decades. Small plastic fragments, found in cosmetics or resulted from friction and abrasion may percolate through the sludge of wastewater treatment plants and subsequently enter the hydrosphere. While the effects of plastic pollution on animals are becoming more evident, it is uncertain if the human health is affected by this phenomenon. In order to apply a precautionary approach, it is necessary to limit the quantity of such pollutants. It is therefore of utmost importance to identify the main direct and indirect sources. Also, a quantification would also be beneficial in order to classify these pollutants. The literature confirms that microplastics may reside in the environment for very long periods of time. Using the STAN2 software, this study designed a Material Flow Analysis that illustrates the main pathways of microplastics. Thus, from source to sink, they can enter the biofuel plants and later enter the pedosphere if the digestate or the sewage sludge is used as fertilizer. The lighter particles may become airborne or can be washed by water overflow. Lastly, most of the microplastics are discharged into the hydrosphere. Even the most performant wastewater treatment plants are unable to capture all the microplastics. In regions where no water treatment is in place, these particles can directly enter the oceans. They can be accidentally ingested by biota. Significant quantities of microplastics were also found in food sources. Using data from international statistics, this thesis quantified the potential amount of microplastics ingested by a human during one year. More than 5800 microplastics may be ingested by one individual from beer, honey, sea salt and seafood only. Around 99% of this amount is excreted. In conclusion, humans may actively contribute not only to an increase in the amount of microplastics, but they also contribute to a recirculation of the particles found in food.