Postgraduate Seminar, Friday 14th May, 2021

By Emily Karanja, MSc Candidate

Assessment of the Impact of Plastic Pollution on the Levels of Bisphenol A and Di-Butyl Phthalates in Water, Soil, Sediment and Weeds along the Kenyan Coastal Beaches.



Plastic materials have received global attention due to worldwide plastic pollution in marine and freshwater environment, and associated hazardous substances released from plastic wastes into water resources, air and soil. Bisphenol A (BPA) and phthalates are some of the toxic compounds from plastics and are associated with endocrine-disruption in human and wildlife. Phthalates function mainly as plasticizers giving flexibility to polymers with high molecular weights, while bisphenol A is part of the key chemical component in the production of epoxy resins, polycarbonate plastics as well as brominated flame retardants (BFRs). The objective of this study was to determine the impact of plastic pollution on the levels of Bisphenol A and Di-butyl phthalates along the coastal beaches of Mombasa, Kilifi, Malindi and Sabaki estuary. Water, weed, soil and sediment were sampled quarterly for chemical analysis between the months of October 2019 and January 2020. Extraction, clean-up and analysis of BPA and DBP was done at the Pesticide Analytical Laboratory at the University of Nairobi using Agilent 6890 coupled to 5973 Mass selective Detector. Levels of BPA were detected in different ranges with few sites recording below detection limit (BDL). Weed samples recorded the highest values during the wet season in Mombasa with a value of 11.66±0.94 ng/g followed by Pirates at 5.91±0.92 ng/g residue levels. During the dry season, Mombasa recorded the highest level of BPA in water samples with 0.429±0.01ng/g and 2.737±0.97 ng/g during the wet season followed by Pirate with 2.238±0.01 ng/g. During the dry season, soil samples recorded the highest concentration of BPA in Sabaki River, Malindi, Mombasa and pirate with 3.24±1.05 ng/g, 2.867±0.62 ng/g, 2.707±2.45 ng/g and 1.338±1.04ng/g respectively. Soil samples during the wet season recorded BPA levels BDL in most sites including pirate. The wet season recorded higher reading in sediment samples than in dry season, where Malindi had the highest of all with 3.765±1.17 ng/g followed by Sabaki Ocean with 3.532±0.42 ng/g. Mombasa and kilifi beaches recorded the highest BPA levels during the dry season of 1.357±0.41 ng/g and 1.294±0.12 ng/g respectively.  Di-butyl phthalate was only detected in Mombasa and Pirates Beaches with soil at higher level of 39.75±0.91 ng/g followed by Mombasa 18.53±0.29 ng/g. Pirate beach had higher readings of DBP in soil samples than in Mombasa and the same applied to sediment, weed and water samples. The rest recorded BDL levels of DBP in all the other samples except soil sample during the dry season while these two sites recorded some amount of DBP during the wet season. Except for pirates and Mombasa, the rest of the sites recorded BDL levels of DBP in water sample during the wet season with 1.291±0.13 ng/g and 0.786±0.22 ng/g respectively.  During the wet season, Pirate recorded the highest level of DBP in weed samples with 1.491±0.25 ng/g, followed by Mombasa with 0.533±0.39 ng/g, and the rest of the sites recording BDL. All the other sites recorded BDL residue levels in dry season. The rest of the sites recorded BDL levels of DBP in the sediment samples analysed during the wet season except for Pirate and Mombasa which recorded 3.040±1.38 ng/g and 2.181±0.49 ng/g, while in dry season the DBP recorded BDL levels in all sites. Except for Pirate and Mombasa, the rest of the sites recorded BDL levels of DBP in the soil samples analysed in both seasons .During the wet season the highest concentration was from pirate soil, followed by Mombasa with 7.556±0.63ng/g and 4.252±0.89ng/g respectively. BPA with high detection frequency of 87.75% than DBP at 17.86% may be due to different sources of these two analytes in the sampling sites. The differences was due to differences in the sampling location and season, environmental factors and physical chemical properties of the contaminant. Therefore awareness creation to educate industries and the public should be done regularly to prioritize sound environmental management of plastics disposal. The information obtained from this study provides baseline data on the levels of Bisphenol A and Di-butyl phthalates in marine environments in Kenya.