Seite - 106 - in Freshwater Microplastics - Emerging Environmental Contaminants?

Despite the lack of scientific confirmation of MPs in Africa’s freshwaters, it wouldbeunfair to say that there is a lackof recognitionof theplastic issue.On the contrary, therehasbeenagreat deal of researchconductedon thepresenceofMPs within themarine and estuarine environment (described in the following section), and also, there has beenmuch progressmade on reducing and banning the use of plasticbags insomecountries.Thisprogresshasnotbeenmadesolely toreducethe plasticwaste but also on the groundsof environmental andpublic health. Improp- erly discarded plastic bags have been shown to block gutters and drains which create stormwater problems and collect water which provides a breeding ground formosquitos that spreadmalaria, and theuseof bags as toilets hasbeen linked to thespreadofdisease[26,27].ThegovernmentofSouthAfrica introducedlevieson theuseofplasticbags in2003 [28], in2005Rwanda imposedabanon theuseand importationofplasticbagsof<100microns thick,andTanzaniasimilarly imposed abanbasedonthickness in2006[27].Suchmeasuresmaynotalwaysbesuccessful as inSouthAfrica levieswere not predicted to reduce the plastic bag litter stream [28].Subsequently theactions taken,whilepositive,mayhavelittle impact in terms of thepotential forMPpollution inAfrican freshwaters.However, the scale of the problemfirst needs to be assessed, and in this regard, studies conducted inmarine and estuarinewatersmay show theway forward. 2 PresenceofMPs inAfricanMarineandEstuarine Environments In comparison to the rest ofAfrica, significantknowledgehasbeengatheredabout the presence, sources, and fate of plastics andMPs in the coastal regions around SouthAfrica and their biota. The earliest documented reports of plastics are from themid- to late1980swithRyan [29]having sampled the sea surfacewater off the southwesternCapeprovince between1977 and1978with a total of 1,224neuston trawls that foundameanplasticdensityof3,640particleskm 2withthemajorityof the particles in theMP range.Commonly found typeswere fragments, fibers, and foamed plastic particles with polyethylene being a predominant polymer [29]. A follow-up study [30] conducted at 50 South African beaches in 1984 and 1989 foundasignificant increase in themeanMPdensity from491m 1 in1984to678m 1 5 years later. Analysis of the distribution ofMPs found that inshore currents rather than local sourceswere responsible for thevariation in abundancesbetween beaches.Conversely, in thecaseofmacroplastics, itwas the local sources that had the greater influence.More recent research conducted byNel and Froneman [31] reached the same conclusion regarding the primary influence on the distribution of MPs in both sediment and water. Across 21 sampling locations along SouthAfrica’s southeastern coastline, comprising both bay and open coast areas, with both sediment and water samples analyzed for MP abundance, the authors 106 F.R.Khanet al.