Dr. Gideon Idowu
Microplastics and plastic-derived chemical contaminants in Africa: Implication on human health and the loss of aquatic biodiversity
Plastic pollution is one of the most fundamental environmental challenges currently confronting Africa. Because of their wide varieties, flexibilities and a very large number of applications, plastics constitute the bulk of solid wastes reaching the natural environment. The unique durability which makes them attractive for the many applications, also causes them to persist in the environment. They only degrade over a long period of time and become tiny plastic particles regarded as ‘microplastics’.
Microplastics are ingested by both bottom-dwelling and pelagic organisms in water, and result in blockage of digestive tracts, starvation, internal and external lacerations, as well as the loss of organ and body weight. Microplastics ingestion also causes reduced reproduction, oxidative damage, biotransformation of enzymes, and accumulation of toxic contaminants from surrounding water.
Microplastics ingestion is not limited to large water organisms like fish, seabirds, and reptiles. Small invertebrate species such as arthropods, shrimps, molluscs and zooplanktons have also been affected. Microplastics ingested by aquatic organisms have higher toxicological risks, through bioaccumulation and biomagnification across trophic levels.
Furthermore, plastic polymers do not come into the environment alone. Numerous other chemical substances are incorporated into them as additives - to serve as plasticizers, colorants, fillers, antioxidants and light stabilizers. These substances leach into the environment during degradation of plastic materials. Of special environmental concern are those additives that have endocrine-disrupting effects on species in the environment. These include phthalates, bisphenols, alkylphenols, and polybrominated diphenyl ethers (PBDEs).
Endocrine-disrupting chemicals (EDCs) interfere with normal hormonal functions in species and cause effects such as feminization of male organisms, ultimately resulting in reduced species population due to impaired reproduction capabilities. Like animals in the wild, humans exposed to EDCs may suffer hormonal imbalances and consequent reproductive impairments, DNA damage and cancers. Human exposure comes mainly through recreational use of surface waters (e.g. for swimming) and through drinking of water from rivers and streams, a practice that is still rampant in most rural Africa.
The overall environmental effect of plastic pollution is a progressive decrease in population of species, an inevitable loss of aquatic biodiversity, and an increased burden of diseases in Africa.
While governments across the continent have signed agreements to eradicate plastic pollution, there is yet no commensurate action plan to this intent, due to a lack of compelling scientific evidence to inform needed policy changes.
This JWO-funded Africa-wide project is bridging data gap on microplastics and EDCs pollution, and providing evidence of their effects on species, the loss of aquatic biodiversity, as well as the human health exposure risks.