1Department of Fisheries Resources and Management, College of Fisheries, India
2ICAR-Central Marine Fisheries Research Institute, India
3Department of Medicine and Surgery, Afe Babalola University, Nigeria
Submission: September 11, 2020; Published: October 16, 2020
*Corresponding author: Mridula Rajesh, Department of Fisheries Resources and Management, College of Fisheries, Mangaluru - 575 002, Karnataka, India
How to cite this article: Sanjay K, Mridula R, Rajesh K, Suyani N, Ahamed R A, et al. Impact of Microplastics on Aquatic Organisms and Human Health: A Review. Int J Environ Sci Nat Res. 2020; 26(2): 556184. DOI: 10.19080/IJESNR.2020.26.556184
Since the development of commercially viable plastic in the 1950s, plastics have become an increasingly important packaging option worldwide. Unfortunately, these materials are increasingly under environmental scrutiny. Larger plastic debris slowly degrades into small fragments with various sizes ranging from meter to micrometer due to changing environmental conditions. Microplastics are a complex class of heavily modified, synthetic organic particulates, which contaminate a wide range of environments. They are a cause for concern because their size range mimics the prey size ingested by the aquatic organisms and these ingested microplastics can be potentially transferred to the higher predators. Recent studies have confirmed the ingestion of microplastics in commercially important fishes, which is ultimately consumed by humans. Thus, massive efforts are required to investigate the distribution and abundance of microplastics in the ocean, and in considering strategies to reduce the problem. Research is urgently needed, especially regarding the potential exposure and associated human health risk to micro and nano-sized plastics.
Keywords: Aquatic organisms; Contamination; Human health; Microplastics; Plastics
Plastics are synthetic organic polymers derived from the polymerization of monomers extracted from petroleum and other products. They are lightweight, inexpensive, and durable materials, which can easily be sculptured into a variety of products that retrieve use in an extensive application. Plastics have attained a crucial status in modern life and are now ubiquitous . The squeezing of plastics was bound in 1839 with the discovery of
vulcanized rubber and polystyrene. In Belgium, the first truly synthetic polymer, Bakelite, was produced in 1907. Extensive production of plastics began in 1940s and ever since it continued to expand. After 1950s, production of plastics has increased exponentially from 1.7 million tons to 360 million tons in 2018  and it is the fastest growing urban waste accounting 60-80% of marine debris .
Plastics have been found virtually in all environments ranging from the arctic to deserts to household dust. They are mainly introduced into the environment through ineffective waste manage
ment practices. It can be dispersed in the environment through atmospheric transport (wind) as well as through hydraulic systems (water flow). They can be carried into streams, rivers, wetlands and oceans (aquatic ecosystems) by wind as well as flowing water such as rain, snow melt that makes its way to streams, or via municipal or industrial water discharges (sewer water). Plastic
pollution on land is concentrated in landfills, urban spaces and
different agricultural lands that uses bio solids from municipal
wastewater treatment plants. Majority of plastic polymers that
find way to the environment are subjected to deterioration that is
caused by various factors, including thermal oxidation, photo-oxidative
degradation, hydrolysis and biodegradation (Table 1) .
However, the habitual plastics found in the marine environments
do not biodegrade and primarily breakdown through photo-oxidative
Plastic compounds take up years to degrade into smaller fragments.
Larger plastic debris slowly degrades into small fragments
with various sizes ranging from meter to micrometer due to
changing environmental conditions. This fragmented plastic with
size smaller than 5 mm are termed as microplastics. According
to GESAMP , microplastics (MPs) have been defined as small
pieces of plastic less than five millimeters in size with no lower
limit established. They are highly persistent in the aquatic ecosystem.
These are not easily seen by the naked eye but are found
in many areas, including lakes, rivers, oceans, sea ice, remote islands,
Antarctic’s, sediments and soil, as well as in the digestive
systems, respiratory structures, and tissues of wildlife, including
birds, mammals, reptiles, fish and shellfish .
Categories of plastic debris
Plastic debris can be expound and narrated in a variety of
ways by shape, size, color, polymer type, origin (e.g. from the land,
fishing-related or sewage-related debris) and original usage (e.g.
packaging, rope). Based on origin, they are also categorized into
primary and secondary microplastics depending on whether the
particles were originally manufactured to be that size (primary)
or whether they have resulted from the breakdown of macroplastics
Four categories of plastics given by Barnes et al.  are as follows:
a) Macroplastics are large (>20mm) plastic debris such as
b) Mesoplastics are large plastic particles such as virgin
resin pellets and are usually defined as 5-20mm in range.
c) Microplastics are small plastic fragments typically less
than 5mm that are derived from the breakdown of macroplastics.
d) Nanoplastics are small microplastic particles ranging in
size from 0.2-2mm.
The term mega-debris (>100mm) is also used and can be applied
to large debris items such as derelict fishing nets.
Types of marine debris
Marine debris is any manmade material including litter and
fishing gear or rope that once lost or thrown into the marine environment.
The most common materials that make up marine
debris are plastics, glass, paper, metal, cloth, Styrofoam, rubber,
wood, derelict fishing gear and abandoned and derelict vessels.
High quantities of marine debris may be found on the shoreline
close to urban areas because of high anthropogenic discards.
United Nations of Environment Programme (UNEP) has included
plastic (moulded, soft, foam, nets, ropes, buoys, monofilament
line), fisheries related equipment, cigarette butts or lighters, metals
(drink cans, bottle caps, pull tabs), glass (buoys, light globes,
fluorescent globes, bottles), processed timber (including particle
board), paper rubber and cloth in the list of marine debris.
The highest percentage of item of marine debris consists of
cap, spoon, small sachets, syringe, paste tube, straw, pen assorted,
plastic bits, bead, hair clips and the plastic and nylon ropes
followed by thermocol and sponge . The United Nations Joint
Group of Experts on the Scientific Aspects of Marine Pollution
(GESAMP) estimated that land-based sources are responsible for
up to 80% of marine debris. Key components of land-based sources
include litter, trash and debris from construction, ports and
marinas, commercial and industrial facilities, and trash blown out
of garbage containers, trucks, and landfills. Ocean-based sources,
such as, overboard discharges from ships and discarded fishing
gear, account for the other 20% .
Microplastics (MPs) have been defined as small fragments
of plastic less than five millimeters in size with no lower extent
entrenched . The MPs present in the marine environment result
from the fragmentation of larger plastic debris or may be introduced
into the water and sediments already as micro- or nano-
sized particles. Examples of microplastics are preproduction
pellets and components of diverse products, such as fragments
of fishing gear, packages and drink bottles, synthetic textiles, car
tyres, paints, cosmetics and personal care products (e.g. facial
cleaners, bath gels, toothpaste), and electronic equipment among
others [5,10,11]. Consequently, microplastics encompass a very
heterogeneous assemblage of particles that vary in size, shape,
and chemical composition, among other properties [12,13]. Microplastics
have been found worldwide, are highly persistent in
the environment, and are therefore, accumulating in different marine
ecosystems at increasing rates. MPs fragments are in a broad
range of shapes and sizes:
a) Fragment - hard, jagged particle.
b) Fiber or line - thin or fibrous, straight plastic.
c) Pellet - hard, rounded, or spherical particle.
d) Film - thin plane of flimsy plastic.
e) Foam - lightweight, sponge-like plastic.
Differences in size and shape can affect the way particles
move through the environment and may modify their potential
for toxicity . Ocean gyres, estuaries, and other coastal areas of
heavily anthropogenic impacted regions are the ecosystems most
polluted with MPs .
Effects of microplastics on aquatic animals including
There are numerous ways through which MPs and associated
contaminants get incorporated into the aquatic biota. This
includes filter feeding, suspension feeding, inhalation at air-water
surface and consumption of prey exposed to MPs or through
direct ingestion. Ingestion is believed to be a main MPs exposure
route for several marine species. Ingestion of small plastic particles
has been reported in more than six hundred and ninety
marine species belonging to different trophic levels . Aquatic
animals including plankton passively ingest MPs due to their inability
to differentiate MPs and food. The minute size, buoyancy
and attractive color of MPs particles make them ideal candidates
as food for fish.
In fish, after ingestion, the MPs may translocate across the
gastrointestinal tract and gills and enter the circulatory system.
The translocation may happen either through Tran’s cellular
uptake or by par cellular diffusion . Through the blood, MPs
reach different organs and muscles. Filter feeders filter larger volumes
of water for food and in the process end up retaining MPs in
their body. The chemical constituents (monomers and additives)
of MPs contain endocrine disruptors which lead to change in fish
behavior, gastrointestinal irritation, disruption of lipid metabolism,
change in micro biome and can cause reproductive problems.
However, presence of MPs in the aquatic environment and
fish gut is an emerging concern that has been reported in different
fishes from different locations of the world (Table 2).
Impact of plastic on marine environment
Plastic pollution is one of the most widespread problems affecting
the marine environment. It also threatens ocean health,
food safety and quality, human health, coastal tourism, and contributes
to climate change. Here are some of the major impacts of
plastic pollution on the marine environment and associated flora
Plastic debris is harmful to marine life including to protected
species of birds, sharks, turtles, and marine mammals. Marine debris
may cause injury or death through drowning, injury through
entanglement and internal injuries, or starvation following ingestion.
a) Ghost fishing: Over 250 species of marine animals are
impacted by entanglement such as turtles; penguins; albatrosses,
petrels and shearwaters; shorebirds, gulls and auks; coastal
birds other than seabirds; baleen whales, toothed whales and
dolphins; earless or true seals, sea lions and fur seals; manatees
and dugong; sea otters; fish and crustaceans. One of the greatest
threats of entanglement to marine life and seabirds is derelict
fishing gear, including monofilament line; trawl nets, and gill nets.
Lost and free-floating fishing gear can continue to ghost fish for
months and even years, ensnaring a wide range of species, particularly
in areas adjacent to fishing grounds, along current convergence
zones, and along shorelines where debris is deposited by
currents and waves. Seabirds, turtles, whales, dolphins, dugongs,
fish, crabs, crocodiles and numerous other species are killed and
maimed through entanglement .
Once an animal is entangled, it may drown, and its ability to
catch food or avoid predators is impaired, or incurs wounds from
abrasive or cutting action of attached debris. Lost or abandoned
fishing nets pose a particular great risk. These ‘‘ghost nets’’ continue
to catch animals even if they sink or are lost on the seabed.
Whales are also caught in their mouths or wrapped around their
heads and tails. Debris entanglement can also have damaging effects
on marine habitats such as coral reefs and sea grass resulting
in the destruction from contact with derelict fishing gear.
b) Ingestion: Many animals, such as sea turtles, seabirds,
and marine mammals have been known to ingest marine debris.
The debris item may be mistaken for food and ingested as natural
food or may have been ingested accidentally along with other
food. Ingestion of marine debris may lead to reduction in the absorption
of nutrients in the gut, reducing the amount of space for
food in the gizzard and stomach, loss of nutrition, internal injury,
intestinal blockage, starvation, and even death. Ingestion of MPs
by marine organisms in the pelagic zone and sedimentary habitats
has increased at concentrations of 150-2400 particles per m3.
Due to small size and free-floating behavior of MPs in the water
column makes it similar to plankton, which enable their consumption
by aquatic biota at different trophic levels, thereby affecting
the species at the organism-level and modify the population structure.
The benthos is likely to be a sink for high density of MPs.
Benthic suspension- and deposit- feeders are therefore likely to
ingest sinking and sedimentary MPs.
c) Invasions of Alien species: Marine litter can serve as
a means of transport for many species, with the potential risk
to facilitate transport of exotic and invasive species altering the
equilibrium in some areas such the open ocean or sandy seabed’s.
They would be first colonized by microorganisms and then, by
macro biota, like mollusks, crustaceans, fishes, cnidaria and echinoderms.
In case the debris floats, the organisms can be transported
to other regions.
Marine litter cause serious economic losses to various sectors
and authorities. Among the most seriously affected are coastal
communities (increased expenditures for beach cleaning, public
health and waste disposal), tourism (loss of income, bad publicity),
shipping (costs associated with fouled propellers, damaged
engines, litter removal and waste management in harbors), fishing
(reduced and lost catch, damaged nets and other fishing gear,
fouled propellers, contamination), fish farming and coastal aquaculture
(reduced seafood consumption).
Impacts on climate change
Oceans, which provide the largest natural carbon sink for
greenhouse gases, plastic leaves a deadly legacy. It directly chokes
and smothers a host of marine animals and habitats and can take
hundreds of years to break down. Plastics, which is a petroleum
product, contributes to the global warming. Sunlight and heat
cause the plastic to release powerful greenhouse gases, leading to
an alarming feedback loop. As our climate changes, the planet gets
hotter, the plastic breaks down into more methane and ethylene,
increasing the rate of climate change, and so continuing the cycle.
Effects of microplastics on human health
Human health risks are mainly attributed to the chemical additives
on plastics and sorbed toxic compounds present on microplastics.
Monomers of certain plastic polymers such as ethylene
and ethylene terephthalate are not recognized as significant human
health threat but styrene exhibits estrogen like activity 
and vinyl chloride is a genetoxic and mutagenic agent . Chemical
additives added to plastics viz., phthalates, bisphenol-A, nonylphenols
and flame retardants act as endocrine disruptors .
Toxic chemicals sorbed to microplastics and harmful pathogens
attached to the microplastics have the potential to negatively affects
When marine organisms ingest plastic debris, these contaminants
enter their digestive systems, and overtime accumulate in
the food web. The transfer of contaminants between marine species
and humans through consumption of seafood has been identified
as a health hazard. The pathway for ingestion of microplastics
present in the marine aquatic environment by humans is depicted
in Figure 1, which is a modification of Rao .
Plan of action to mitigate microplastics in the aquatic
a) The release of plastics to the aquatic environment needs
to be drastically reduced. There is an urgent need to prohibit the
use of microbeads in cosmetics towards reducing microplastics
b) Wastewater and drinking water treatments are highly
efficient in getting rid of more than 90% of microplastics. Hence,
wastewater treatment plants should be upgraded, and better
waste management practices should be involved by creating recycling
infrastructure so that the plastics could be eliminated from
the water before they are released into the aquatic environment.
c) Many interventions can be done by individuals to reduce
microplastics entry in to the aquatic system. Perhaps the most important
step lies in changing the way we think and behave. Hence,
the product innovation for biodegradable alternatives to plastic
polymers has to be strengthened and encouraged with the use
of natural alternatives to additives used in plastic manufacture,
edible cutlery, paper straws, biodegradable food wrappings, and
edible food coatings.
d) Upgradation of washing machine, which is the main reason
for transfer of microplastic fibre particles from clothes, can
prevent microplastic fibre particle from entering sewer.
e) Enhance public education through nationwide campaigns
such as ‘Beat Plastic Pollution’ campaign of the United Nations
and ‘Green Good Deed’ of Ministry of Environment, Forests
and Climate Change, Government of India and campaigns to emphasize
refuse, reuse and recycle plastics.
The defilement of oceans by microplastics is of great concern
due to its ecological as well as health impacts. They may compromise
food security, food safety, and consequently human health.
They have now taken place in all the corners of the world and in
all the environments ranging from the arctic to deserts to household
dust. As plastics takes more than 300 years to disintegrate in
to micro and nano-plastics indicating the impact of plastic pollution
on aquatic animal health and human health for years to come.
The occurrence of microplastics in fish species used for human
consumption is a global problem and we are vulnerable to microplastic
exposure through the consumption of seafood and other
human food items, as well as through other routes such as air. The
impact of microplastic contamination of aquatic life on human
health is currently unknown and is a potential area of research.
Thus, there is a need of immediate priority and strong action plan
to mitigate the microplastics pollution in the aquatic environment.
Proper solid waste management programs and reduction
in the use of plastics are required. Moreover, there is a need for
coastal clean-up program and facilities to deposit non-degradable
litter in public places.
GESAMP (2016) Sources, fate and effects of microplastics in the marine environment: part two of a global assessment.In: Kershaw PJ, Rochman CM (Eds.),IMO/FAO/UNESCOIOC/UNIDO/WMO/IAEA/UN/UNEP/UNDP Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection. Reports and Studies GESAMP, 93, p.220.