Page - 35 - in Freshwater Microplastics - Emerging Environmental Contaminants?

containingbiocidal additives, plasticisers or flame retardants are likely to bemore environmentally hazardous, as these substances may leach out of the polymer matrix. One effect mechanism is being highlighted as important for both engineered nanomaterials andnano- andmicroplastics, namely, physical interactions between the particle and the organisms [43]. This includes inflammation and interference with theenergybalancecausedbyuptakeofparticles into thegut, thereby limiting food uptake.Different types of engineered nanomaterials, aswell as nanoplastics, have been observed to adhere to the surface ofmicroalgae, potentially causing a physical shadingeffectonacellular level [44].Physical effectsofmicroplasticson marine organisms have been reviewed recently [45], and mechanisms that have been described as potentially relevant include blockage of the digestive system, abrasionof tissues,blockageoffeedingappendagesof invertebrates,embedment in tissues,blockageofenzymeproduction,reducedfeedingstimulus,nutrientdilution, decreased growth rates, lower steroid hormone levels and impaired reproduction. Table 1 presents an overview of effects in response to the physical particle prop- erties that havebeenobserved in different species. The potential of microplastics to cause such physical effects on organisms depends on a number of factors. Particles with a high capacity to accumulate in Table 1 Examples of biological effects observed in aquatic organisms after exposure to engineerednanoparticles or nano- andmicroplastics Engineerednanoparticles Nano- andmicroplastics Molecular/cellular level Oxidative stressa Inhibitionof photosynthesis (shading)b DNAdamage anddifferential gene expressionl Cellular stress response and impaired metabolismm Tissue level Histopathological changesc Transfer into cellsd Tissuedamagen Transfer into tissueso Organ/organismal level Morphologicalmalformatione Decreased swimmingvelocitiesf Increasedmucusproductiong Toxic effects of released ionsh Decreasedgrowth rates andbiomass productioni Moulting inhibitionj Impairedmobilityk Impaired respirationp Impaired feedingq Impaireddevelopment and reproductionr Decreasedgrowthratesandbiomassproductions Behavioural changest Increasedmortalityu aIn algae [46]; bin algae [47]; cin fish [48]; din algae [49]; ein fish embryos [50]; fin crustaceans [51]; gin fish [52]; hin algae [53]; iin algae [7]; jin crustaceans [54]; kin crustaceans [51]; lin echinoderms [55], bivalves [56–58] and fish [59]; min polychaetes [60], echinoderms [55], bivalves [56–58, 61] and fish [62–64]; nin fish [59, 64, 65]; oin crustaceans [66], mussels [67, 68] and fish [69]; pin polychaetes [70], crustaceans [71] and bivalves [72]; qin polychaetes [60, 73], crustaceans [74, 75], bivalves [72, 76, 77] and fish [62]; rin crustaceans [74, 78, 79], echinoderms [80], bivalves [58] andfish [81]; sin crustaceans [75, 79] and bivalves [72]; tin fish [62, 81, 82]; uin crustaceans [75, 83], bivalves [72] andfish [84] AquaticEcotoxicity ofMicroplastics andNanoplastics: LessonsLearned from. . . 35