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Chapter 14
Environmental Impact of Polyurethane Chemistry
Charles Oluwaseun Adetunji,*,1Olugbemi T.Olaniyan,2Osikemekha Anthony Anani,3
Abel Inobeme,4and John Tsado Mathew5
1Applied Microbiology, Biotechnology and Nanotechnology Laboratory,
Department of Microbiology, Edo University, Iyamho, PMB 04, Auchi,
Edo State 312101, Nigeria
2Laboratory for Reproductive Biology and Developmental Programming,
Department of Physiology, Edo University, Iyamho, PMB 04, Auchi,
Edo State 312101, Nigeria
3Laboratory of Ecotoxicology and Forensic Biology, Department of Biological Science,
Faculty of Science, Edo University, Iyamho, PMB 04, Auchi, Edo State 312101, Nigeria
4Department of Chemistry, Edo University, Iyamho, PMB 04, Auchi,
Edo State 312101, Nigeria
5Department of Chemistry, Ibrahim Badamasi Babangida University, Lapai,
Niger State 911101, Nigeria
*Email:adetunji.charles@edouniversity.edu.ng
Polyurethanes (PUs)are frequently produced from the chemical reaction of polyol
and isocyanate molecules in the presence of light and enzymes.Polyols and
isocyanates sourced from PU contain a lot of properties that make them essential
for both domestic and industrial uses.It has been established that polymers of
PU are chemically sluggish and might contain hazardous materials like phosphate,
glycols,and amines,which might be dangerous to the respiratory tract,skin
systems,and the environment.is chapter reviews the environmental
applications of PUs in diverse elds.Highlights of the environmental impact of
PUs on aquatic life,soil health,plants,and humans,along with the general
chemistry, are discussed.
Introduction
Polyurethanes (PUs)are polymers made of organic units joined by carbamate compounds.
Most PUs are known for their thermoseing and thermoplastic properties and are traditionally
formed by reacting tri-or diisocyanate with a polyol.PUs are classied as copolymers because they
contain two monomers:polyols and isocyanates.Polyols and isocyanates can be used to produce
hoses,condoms,electronic materials,the underlay of carpets,articial bers,sealants,adhesive,
skateboards,elevators,shopping carts,escalators,and roller coasters (1,2). e monomers consist
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of chains of chemicals like 1,1-dichloro-1-uoroethane,1,1,3,3-pentauoropropane,methylene
diphenyl diisocyanate,toluene diisocyanate,toluene,and diisocyanates,which are known to have
negative environmental and human health eects because they are sourced from phosgene (3,4).
It has been established that polymers of PU are chemically sluggish and might contain hazardous
materials like phosphate,glycols,and amines,which might be dangerous to the respiratory tract
and skin systems (5–8). For the past few years,there has been growing concern regarding the
epidemiological,clinical,industrial hygiene,and animal data and the role of PUs in disease
conditions (9).
In 2016,PU production was estimated to be over 18 million tons globally on an annual basis
and was forecasted to surpass 26 million tons in 5 years (2021) (10,11). Rapra (12,13)recounted
that the universal market sales of PU products such as foams were worth over $100 billion in 2015,
with an expected utilization in terms of product consumption aaining 25.3 million tons in the same
year.Normally,PUs are produced from the chemical reaction of polyol and isocyanate molecules
in the presence of light and enzymes (14,15)and contain more than two groups —R′−[OH]n≥2
and R−[N=C=O]n≥2—correspondingly (16).e properties of elasticity,soness,toughness,and
rigidity exhibited by PUs chiey rely on the categories of isocyanates and polyols from which they
form (17,18).
is chapter reviews the environmental application of PU in diverse elds.Highlights of the
impact of PU exposure on humans and their health implications are further elucidated,together with
the chemistry.e environmental impact of PU on aquatic,soil health,and plants is analyzed.e
modes of action of the PU using a typical example of xenobiotics are discussed.e benecial role of
PUs as a coating and adhesive agent and several future recommendations are highlighted.
Chemistry of PU
PUs are one of the important classes of thermoset and thermoplastic polymers formed using
polycondensation reactions between diverse chain extenders isocyanates and polyols,resulting in an
extensive variety of polymers with several diverse properties and applications.Most of these thermal,
chemical,and mechanical properties may be achieved through the reaction among hydroxyl groups
and polyisocyanates,producing urethane groups,along with ramications that may be aained by
adding previously manufactured urethane groups.e hydroxyl compound with its functionality as
well as the isocyanate may be improved to form cross-linked or branched polymers.Some structural
changes may also be made by varying the nature of the synthetic routes,monomers,and industrial
development.In these cases,the chain exibility and the cross-linking properties of PUs along with
intermolecular forces can be diverse, extensive, and autonomous (19).
Several varieties of isocyanates could be applied in PU synthesis.Generally,aromatic
diisocyanates can react more easily than aliphatic ones;as a result,aliphatic diisocyanates are useful
in precise reactions to direct distinct properties in the nished item.From these,it should be noted
that some of this adaptability is very relevant,particularly in the area of analytical chemistry.e
elimination of chemical constituents through an aqueous medium is a signicant issue from an
environmental and an industrial point of view.e adsorption method has achieved prominence
in the management of euents and waters,particularly when the adsorbent employed shows small
charges and does not need any management before being applied.In this situation,PU foams can
be treated with suitable adsorbents for the maintenance of chemical constituents,based on their
cheapness,and can also be applied without any earlier usage.PU foams present robust chemical
properties,are highly energy ecient,have thermal resistance,are biodegradable,and are easily
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found in the market.Current scientic interests are advancing the study of syntheses comprising
an inert polymer and a conductive polymer matrix.Possible applications of such syntheses are
electrooptical and electrochromic devices,actuators,and sensors,among others.Although PUs have
several merits as elastomers and conductive polymers,those using conjugated chains are usually
categorized as brile,rigid,and dicult to process,which has led to many aempts to overcome
some incompatibilities.When dealing with conducting polymers,the major objective is the
formulation of polymeric constituents employing good mechanical properties and the processability
associated with electrochromism or high conductivity.PU syntheses have been extensively applied
in electroanalysis because they have several advantages when compared to metallic probes (19).
Mass spectrometry and its hyphenated methods have been applied to characterize PU synthetic
polymers and their separate so and hard sections.PU usually consists of hard parts that include
toluene diisocyanate and methylene biphenyl diisocyanate and so parts such as polyether and
polyester polyols.However,some studies using mass spectrometry methods have revealed
exceptional features related to the structural integrity and the makeup of complex PU precursors and
PU materials. A list of typical PU materials is shown in Figure 1.
Figure 1.Typical examples of PU material.
e catalytic technique was also used in the production of polyhydroxyurethanes,which gave
remarkable yield through the additional polymerization pathway (20). e study revealed that the
perhydroxylated dodecaborate cluster [B12(OH)12]2−can perform as an inorganic polyol,formed
from a molecular cross-linker in the production of PU-based materials.e study also demonstrated
how the characteristic robustness of the boron collection used can eciently improve the thermal
steadiness of the manufactured PU constituents integrating [B12(OH)12]2−building blocks when
compared to equivalent polymers made from carbon-built polyols.In the end,this method makes
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available a possible direction for adjusting the physical as well as chemical properties of so
constituents by the integration of polyhedral boron-rich clusters into the polymer network (21).
PU urea is a non-isocyanate substitute for the traditional ones,which are produced through
aminolysis and transurethanization of cyclic carbonates,usually accomplished in bulk as well as in
solvents.For numerous reasons,such as properties,environmental impact,and scalability,there is
increasing interest in an advanced non-isocyanate PU urea that is based on water (21).e chemistry
of PUs gives rise to dierent compounds that are regularly jointly mentioned as reaction polymers.
Some of these compounds are unsaturated polyesters,epoxies,or phenolics.PUs are frequently
synthesized through the reaction of a polyol and an isocyanate molecule in the presence of ultraviolet
light or catalyst activation.ese polyol and isocyanate molecules could certainly comprise two or
more hydroxyl groups (RO–[OH]n≥2)or isocyanate clusters (R–[N=C=O]n≥2)respectively.e
displayed characteristics of the PUs generally depend on the kinds of isocyanates and polyols from
which they were prepared.However,because of the cross-linking,the PUs oen have an unlimited
molecular mass through a 3D system composition (15).
Polyols utilized for PU synthesis frequently comprise two or more –OH groups.Diverse
categories of polyols are accessible and can be formulated in laboratories through several means.For
instance,polyether polyols are acquired using ethylene oxide and the copolymerization of propylene
oxide employing a compatible polyol originator,although polyester polyols are produced in a related
mode in the same paern by which polymers based on polyester are made.One kind of polyether
polyol,poly(tetramethylene ether)glycol,is formulated through the polymerization of
tetrahydrofuran for extremely eective elastomeric uses (18).
e impacts of certain catalysts on the properties and structures of PU prepolymers and systems
are examined to regulate the composition and association for a specic usage.is study revealed the
requirements of the catalytic process for the production of PU,equally at the cross-linking stages and
the prepolymer,and highlights the catalyst reliance of both stages.On the other hand,when llers
likethose utilized in industrial large-scalePUpreparationsarepresent,tensiletestsdemonstratedthat
the mechanical properties are aected and can be tailored through the selection of the catalyst.e
catalytic process for the production of PU is shown in Figure 2.
Figure 2.Catalytic process for the production of PU.
Chemistry of PU Foam
Aastha (22)established that PUs belong to the family of thermoseing polymers,which when
heated do not melt.At the same time,certain thermoplastic PUs are also obtainable.e monomer
of urethane is the key characteristic of this polymer.e reactions of PU formation are exothermic
reactions (involving the evolution of heat), where condensation reactions take place between an
alcohol that has not less than two reactive –OHs(hydroxyl)radicals per molecule (triols,diols,
polyols)andanisocyanate,which has at least one reactive –NCO(isocyanate)groupin the respective
molecule (diisocyanates and polyisocyanates).
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Polyols are utilized to make polyisocyanurate and PU foams.e production of renewable
polyols utilized for polyisocyanurate and PU foams shows a large accessibility of compound
chemicals from biomass.ese have been categorized according to their chemical composition.e
equivalent chemical paths have been linked,employing the properties of the nal PU-based foams.
Relationships were outlined among the source of the polyol and the morphologies,properties,and
chemical modications of the equivalent foams.Modern improvements in non-isocyanate PU foams
have been similarly considered (23).
e chemistry of the reactions that take place among the ancillary and polyisocyanate raw
materialstoproducePUswasascertained.Applications of urethanes can be found in four major elds
of activity:rigid foams,exible foams,rubbers,and surface coatings.Other work shows that the
industrial growth of urethane polymers,mainly the rigid and exible foams,has been determined by
the application of engineering skills in creating acceptable machinery as much as improvements in
the chemistry involved (24).
Chemistry of PU Coatings
e chemistry of the –N=C=O(isocyanate)group oers the essential foundation of the
chemistry of PU coatings.Its high chemical reactivity,together with its capability to respond to
employing dierent chemical associates,creates the isocyanate set mainly suitable for the coatings
market.e isocyanate group could respond through any compound that possesses reactive
hydrogen,such as an alcohol,water,or an amine.Golling et al. (25)reviews isocyanate chemistry as
well as future improvements in isocyanate chemistry for PU adhesives and coatings.For more than
60 years,this area of chemistry was driven by several innovations that helped increase coating uses
with a view to the needs of customers,strengthening the characteristics of this exceptional material.
Solvent borne PU have found relevance in dierent areas and have become a point of reference for
high-performance coating schemes.e qualities that make these schemes so impressive are the
fast treatment under baking or ambient conditions,mirror-like nishes and high gloss,exibility or
hardness as desired, solvent and chemical resistance, and outstanding weathering resistance.
de Haro et al. (26)stated that PU coatings that have high lignin content were characterized
and developed in their ndings.e materials used were based on a 1,4-bis(4-isocyanate-2-
methoxyphenyl)butane (α,ω-diisocyanate monomer)achieved from lignin-derived vanillic acid,
along with the additional reaction of cross-linking employing three diverse,nonchemically improved
practical lignins acquired from diverse crushing processes (kra,soda,and mild acetone organosolv).
When they determined the optimal lignin mass ratio for both kinds of lignin,an in-depth
classication of the acquired PU coatings emphasized their eective cross-linking,high biomass
content,hydrophobic character,improved thermal stability,tunable mechanical response,and
ecient adhesion results on dierent types of substrates.Many of these properties were found to be
highly related to the physicochemical structures of the main lignins utilized,such as glass-transition
temperature,molecular weight,−OH content,and the distribution of phenylpropane subunits,thus
suggesting the prospect of foreseeably tailoring the features of such biobased PU coatings through
lignin assortment.e study establishes the lignin response obtained from biobased diisocyanate
with diverse technical lignins that are not chemically modied,which epitomizes a motivating route
for the manufacture of thermoseing PU coatings using a great biomass concentration.
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Environmental Impact of PUs
PUs are a group of polymers that are synthetic in nature and are known to be unique and
highly versatile.is class of polymer is readily produced and processed on a broad scale using
dierent methods (27).PUs are a fundamental component of materials used in the present era and
are widely applicable in various human endeavors.eir uses cut across dierent areas,including
coatings for furniture,materials used in construction,ame retardants,synthetic skins,and other
elastomeric components.ey are very relevant in other areas such as the medical elds,where they
are employed in tissue engineering as scaolds,adhesives for so tissues,devices for the eective
delivery of drugs into biological systems, pericardial patches, and synthetic coverings of skin (15).
Environmental Impact of PUs on Aquatic Environments
Rutkowska et al. (28)did an investigation in which the degradability of PUs in seawater that
contained sodium azide was estimated.e polymer materials were subjected to incubation for 12
months.Variations in the properties of the PUs—such as tensile strength,weight,and structural
morphology—were then examined.It was observed that the extent of degradation of the PU samples
in the seawater depended on the extent of cross-linking in the polymer.
PU-based materials are found in dierent forms.For example,the foams are found in shoes and
other materials used in packaging as a cushion and in boxes commonly used for shipping.In building
construction,a spray foam made of PU is used as an insulating material.Most of the chemicals
present in these products used daily by humans have toxic components.e composition of spray
PU,for example,includes a mixture of Side A and Side B chemicals (29).Most of the chemicals
present are harmful to organisms in the environment.e cocktail of chemicals is capable of harming
aquatic organisms when it comes in contact with water.e chemicals are usually trapped in the
solid foam once it has solidied,and they remain very toxic.Also,most of the shavings that are
released from the foams,as well as the dust particles,discharge excess chemicals directly into the
environment,which also has a harmful eect.Eventually,the chemicals get into the waterways
and most other aquatic environments and have bioaccumulative tendencies in the bodies of aquatic
organisms (30).
Side A Chemicals
e groups of compounds that make up the components commonly described as Side A
chemicals include various classes of isocyanates,such as diisocyanates of methylene diphenyl groups.
is group of toxic compounds is capable of irritating skin,causing respiratory problems,triggering
serious asthma,and destroying the mucus linings of various respiratory surfaces.Some of these
compounds are carcinogenic in nature (29).
Side B Chemicals
e major components of the second class of chemicals used include ame retardants,polyols,
and amine-based catalysts.Most of the compounds have a serious eect on the environment.When
washed into water bodies,they have the potential to aect aquatic organisms.Some of the
compounds of the amine are associated with blurred vision.ey are also capable of causing serious
burns to the mouth if accidentally ingested.Also employed as catalysts are the polyols,which are
employed to speed up the process of foam solidication.ey are also capable of building up in the
brain, liver, and other sensitive organs of organisms (29).
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Bioaccumulation of Flame Retardants
Bioaccumulation of Side B components such as ame retardants has been reported in some
studies.ey are capable of building up in the bodies of animals when they get into the waterways.
e chemical constituents of the ame retardant responsible for this toxicity include tris(1-chloro-
2-propyl)phosphate and hexabromocyclododecane.Because of the solubility of some of these
chemicals in fats,they build up in fay tissue and the liver of aquatic organisms and are eventually
eaten by humans.e presence of hexabromocyclododecane has been reported in Norwegian cod
and is found mostly accumulated in the liver.Other toxic chemicals have also been reported in blue
mussels (29).
e ame retardants present also decrease reproductive health as well as the survival of various
aquatic organisms.ey aect aquatic plants,such as algae,and organisms like worms and daphnids.
e hormonal balances in sh are altered by the presence of this toxic chemical.Studies have also
documented the alteration of the enzymes in the liver of salmon.ese chemicals can survive in
the air for months and in the soil for several days.In the aquatic environment,the chemicals have
been reported to have a half-life longer than 182 days,pointing to their deleterious eect on the
environment (30).
Environmental Impact of PUs on Soil Environment and Soil Health
One of the major issues of concern is the environmental contamination by various pollutants
released from various production processes and materials.e production of PUs is a concern
because of some of the toxic substances that are associated with it.ese materials are capable
of aecting the environment,including soil and aquatic bodies (31). PUs are cheaper for some
processes,but they are documented to have deleterious impacts on the environment,including soil
quality and properties.However,new regulations have been put in place at the international level to
ensure the use of PUs as a relatively safer option (32).
e major components of PU production are methylene diphenyl diisocyanate and toluene
diisocyanate.Because of their impact on soil and other environments,strict regulations govern their
production in some countries.PUs also have a positive usage and impact on soil quality.In sandy
soil,a primary challenge known in their usage is their low strength in terms of shear and cohesion
when used in engineering.Dierent approaches have been considered in resolving this,and most
lack environmental perspective and impact.Studies have reported the use of PU and a combination
of natural ber to achieve the desired quality of the soil and a unique ecofriendliness (33).PU is
employed in the reinforcement of sandy soil.e introduction of PU and ber materials brings about
a signicant improvement in the ductility of sandy soil for wider engineering applicability (34).
e mechanical behavior of soil is also improved through the inclusion of PU in the soil matrix.
e improvement in the mechanical quality of soil has been reported (35). PU-based bers are
widely applied in various geotechnical processes because they can be employed conveniently for
many purposes.When they are introduced into the soil,they have the potential to enhance the
strength isotropy and reduce the presence of planes of weakness that could be formed in parallel
to the reinforcement.However,some environmental implications and challenges arise from the use
of PU in this aspect of enhancing the mechanical properties of soil.is is due to the pollution
associated with microplastics.is tends to be more pronounced when eective measures are not put
in place as a control mechanism in minimizing environmental contamination (33).
e use of soil for construction is aected by the poor engineering and physical properties of
the soil.Various techniques and processes have been put in place to improve the properties of weak
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soils to reduce the potential damages.e use of PUs in this regard to improve soil quality cannot
be overemphasized (36).Eective soil stabilization to improve soil properties is readily achieved
through the use of PUs.e compression index of soil is reduced through this process while
increasing the performance strength (37).
ree major kinds of PU were synthesized to improve the resistance of soil to erosion using
a mixture of polypropylene glycol,toluene diisocyanate,and polyethylene glycol.Findings from a
study showed an enhanced resistance of soil to erosion that was due to the addition of PU (30). e
transport of PU sealants in the soil is due to the interaction between moisture and the isocyanate
groups (38). In one study (31),foam from liquid PU was added in dierent amounts by soil mass
and index,and an assessment of engineering parameters was done.e desire was to nd out the best
amount of PU to add for the most ecient stabilization.It was reported that the mechanical property
of the soil was signicantly improved with the addition of foam made of liquid PU.Various useful soil
mechanical parameters were found to be enhanced by the introduction of PU into the soil.
Degradation of PUs in Soil
Some polymeric materials are not readily degraded and are xenobiotic in nature,hence the quest
to assess the degree of biodegradability of polymers in order to understand their impact on the
environment.Strategies have also been put in place to minimize the impact of PU on soil and other
components of the environment (39). ere is a growing trend to develop new materials that can be
easily degraded,producing substances that are environmentally friendly.Considering the concern
for the impact of PUs on the environment,there has been shi in emphasis to the assessment of
its degradation through the action of microorganisms.Several factors that aect the ease and rate of
degradation of PUs have also been assessed (27).
e degradation of PUs in soil can occur in the natural environment through the combined
action of various environmental factors,by the combined eort of microorganisms,microorganisms,
and enzymes.e rate of decomposition is aected by various physical and chemical parameters.
In most studies,the degradation of PU is considered under natural weather conditions.Studies
have reported three major types of degradation of PUs:enzymatic degradation (polyurethanase),
degradation by fungi,and degradation by bacteria.It has been reported that PUs are very susceptible
to aack by fungi.Dierent groups of fungi are known to be associated with the biodegradation
of PUs.In some reported studies,Cladosporium spp.Curvularia senegalensis (and Curvularia spp.),
Aureobasidium spp., and Fusarium spp.were obtained in soil and were capable of degrading PUs.
ey were also observed to produce enzymes such as PU that could bring about the process of
degradation.
e presence of variety in the population of microorganisms usually implies that the possibility
for removal of waste exists at a polluted area,and the process of PU degradation could be aected by
the absence of induction of the metabolism routes that are responsible for the process of degradation.
is forms the basis of biostimulation,during which the introduction of exogenous materials could
enhance the breakdown of the PU waste.Cosgrove et al. (40)carried out a study to assess the
use of bioaugmentation and biostimulation for the removal of PU waste from soil.e process of
degradation was determined aer biostimulation of microcosms of the soil using a dispersion agent
of PU (impranil)and bioaugmentation using PU-degrading fungi.Enumeration of the communities
of fungi and the colonizing of buried PUs were done through the use of gel electrophoresis.It was
reported that there was an increase in the degradation of the PU waste through the addition of
yeast when compared to a lower degradation that was observed in the control soil sample where
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yeast was absent.e population of the local PU-degrading fungi was increased by bioaugmentation,
which also contributed to the increase in degradation.e study reveals that bioaugmentation and
biostimulation are useful in removing PU contaminants from the soil (40).
e high resistance of PUs to decomposition has been documented,and this has been aributed
to their high resilience.ey can,however,be broken down into smaller compounds under suitable
environmental conditions.e cross-linking in the polymer can be broken down by the activities
of various micro-and macroorganisms,including fungi and bacteria.Under aerobic conditions,PU
undergoes decomposition that results in the production of water and carbon (IV)oxide,as well as
some other trace compounds from the microorganism activities (32). Aerobic decomposition also
plays a unique role in the breakdown of PU in the soil environment.is process occurs in the
presence of oxygen.When conditions are favorable,the PUs are capable of degrading into smaller
compounds.It is worth noting that cast PUs do not degrade into smaller compounds in the same
way that thermoplastics do.During the breakdown of the cross-linking present in the thermoset
PUs,there is a release of molecules,individually such that the impact on the environment would be
minimized.is,therefore,implies that most producers of this polymer in a commercial state usually
consider this during the course of production (32).
Beneath landlls containing PUs,it has been reported that there are species of fungi that have
the potential to induce the degradation of PUs under aerobic and anaerobic environments.e
degradation of materials containing PUs in the vicinity of museums has also been reported.Among
the dierent classes of these polymeric compounds,the polyester-based ones tend to break down
more readily by the action of fungi (41).Findings from the study reveal that polymeric materials that
are based on polyester PU tend to resist degradation by microorganisms,as well as some chemical
aacks.Such materials,however,readily hydrolyze through chemical action under high temperature
and pH as well as other extreme conditions in the environment.e resistance of some polyester PUs
to microbial degradation could result in the signicant accumulation of some aromatic amines.
Mathur and Prasad (42)isolated fungi from soil samples and assessed that they are eective in
degrading PU.e fungi’s ability to make use of PU as their only carbon source was checked by
shaking the culture for 30 days.e researchers identied the presence of an extracellular enzyme
that was responsible for the process of degradation,known as an esterase.e biodegradation of PU
is vital for both producers and consumers and the environment at large.is concept is also very
useful in bioremediation processes for the removal of PU from the environment (26).
Khan (39)isolated a fungus,Aspergillus tubingensis,capable of inducing the degradation of PU.
e potential of the fungus in degrading the PU was also assessed using three dierent approaches
using 2%glucose.e studies revealed a signicant degradation of the polymer by the fungus and
reported the potential of A.tubingensis to minimize environmental waste that is due to PU
compounds.
Environmental Application of PUs in Diverse Fields
Krasowska et al. (43)revealed that many factors inuence the biodegradation of polymers,
particularly PUs in the environment,based on poly(ethylene–butyleneadipate), poly(ε-
caprolactone), and poly(ester–urethane), in an investigation using seawater to monitor
physicochemical parameters such as pH,the activity of dehydrogenases,temperature,salt,moisture
content,and oxygen content.e authors revealed that PUs in the environment can be degraded
depending on physiochemical properties like tensile strength,weight,morphology,and crystallinity
and on environmental conditions through enzymatic hydrolysis of ester bonds vulnerable to fungal
degradation.
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Naldzhiev et al. (44)carried out an assessment of PU in terms of indoor environmental impact
and its degradation to various compounds like isocyanate,ame retardant,byproducts,polyol,
catalyst amines,and blowing agents known to have detrimental eects on human health.e authors
systematically analyzed the public and environmental impacts of the toxic agents that are due to
increased emission in high quantities from various household materials,and then they outlined the
negative consequences for ventilation or air quality in the environment.Further investigation was
suggested by the authors to check on whether a single compound or combined compounds of this
PU were responsible for the possible negative health impact.Studies have revealed that PU is utilized
for dierent household equipment, installations, insulation, and gadgets.
Pavani and Raja (45)revealed that there has been a massive increase in the establishment of
plastic industries in some major cities across the globe due to their ease,convenience,and cheapness.
Studies have revealed that much of this plastic is nonbiodegradable,thus contributing to a negative
impact on the environment through pollution,endocrine disruption,cancer,and congenital
anomalies and developmental defects.Disposal of these plastic materials in bodies of water has been
demonstrated to pose a serious threat and jeopardize the survival of many aquatic animal species
through such anthropogenic activities.e authors suggested ways to mitigate these issues,such as
public awareness,alternative means of disposal,and the establishment of plastic recycling facilities.
e sensitive marine ecosystem is altered by entanglement with plastic debris,causing starvation
or malnutrition,injuries,infections,reproductive failure,and death among aquatic animals,aquatic
vegetation, sea turtles, and nesting birds.
Adane and Muleta (46)revealed that in Ethiopia,serious environmental and health challenges
are caused by plastic waste pollution,so the authors investigated the use of plastic bags and their
environmental impacts in Jimma City in Ethiopia.In their ndings,they revealed that a large
population utilizes plastic bags more frequently than any other plastic products,resulting in open
dumping in surrounding areas and causing blockage of sewage lines,animal death,human health
issues,and deterioration of natural habitat.ey also showed that the trend in the utilization of
plastic bags is increasing despite the awareness concerning the danger and adverse eects on the
environment.It was suggested that more legislative or policy action against the use of plastic products
will be needed to end the production and distribution of plastic bags by retailers.Boadi and Kuitunen
(47)showed that in regions aected by plastic waste,many of the respondents support the banning
of production,distribution,and utilization of this plastic product and inclusion of all relevant
stakeholders in the campaign against the use of plastic products to curb the challenges of plastic bag
waste.
Porwal (48)revealed that paints and furniture vanish contain PU compounds and byproducts
known to cause seriously detrimental eects on the environment,agricultural productivity (due to
salinization from irrigation water), and human health.Nkwachukwu et al. (49)revealed that many
environmental and health concerns have been generated by the increased growth of plastic industries
as a result of poor management practice.Pollutants such as PUs or polyolen are released from
the burning of plastic materials,seling on land and water bodies and thus accumulating in the
ecosystem,with the resultant eects of cancer,congenital anomalies,reproductive failure,subtle
neurobehavioral eects,and immune diseases.Yang et al. (50)revealed that the application of PU
foam materials has increased signicantly in the past few years,so disposal remains a serious concern.
e authors suggested that recycling seems to be the most desirable response.Nagy and Kuti (51)
suggested that recycling,environmentally friendly solutions,and improved waste handling are
recommended responses in adopting an environment-and health safety–conscious aitude in the
21st century.
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Howard (52)briey highlighted that the nondegradability of plastic-like PUs is a major concern,
so recycling of plastic waste seems to be the best option in curbing the detrimental eects of PU
polymer.e increased pollution caused by these compounds is a result of the vast applications
in medical,automotive,and industrial activities.PU polymer is a result of condensation of
polyisocyanates or polyalcohols,which determines the enzyme-degrading systems by hydrolysis of
ester bonds via esterase enzymes of microbial origin.Guolo et al. (53)revealed that by the year
2030,the European target is to achieve a sustainable environment essential to building a global
economy devoid of pollutants.PUs utilized in thermoset polymeric insulation products,transport,
and installation would need to be recycled at the end of their life span.
Pikoń and Czop (54)revealed that more aention has been given to developing biodegradable
packagingmaterialsfromrenewablenaturalresourcesbecauseoftheirreducedlevelofenvironmental
impact.e authors showed that biodegradable plastic is beginning to replace traditional petroleum-
based plastics, which are known to pose serious environmental and health issues.
Hahladakis et al. (55)suggested that the multipurpose,inexpensive nature of plastic has hugely
increased the level of its utilization across the globe due to plastic material demand.us,the
increased production of plastic materials will result in increased plastic waste creation,which if
not eectively managed will result in detrimental health and environmental issues.Reddy et al.
(56)demonstrated that plastics are capable of releasing chemicals and various additives into the
soil,water,and atmosphere,thereby altering the ecosystem and resulting in global warming.e
authors revealed that,to date,there are no data or gures to show the appropriate amount of plastic
contamination or microplastic debris in aquatic habitats.
Environmental Impact of PUs on Human Beings and eir Health
Rustagi et al. (57)revealed that,due to the rise in plastic industrial growth,many concerns
have been raised regarding the detrimental impact of plastic waste on the environment and human
health.Many adverse eects have been aributed to the exposure to chemicals and additives like
PUs released from plastics into the water,food,and products consumed by humans.Some of the
eects of plastic consumption include birth defects,cancers,impaired immunity,developmental and
reproductive eects, and endocrine disruption.
Zoeller et al.(58)revealed that knowledge concerning plastic chemicals like PU and bisphenol A
that are endocrine disruptors has increased tremendously.More information about their detrimental
health impacts is beginning to emerge.Studies have revealed that these chemicals are at high levels
in the environment from industrial leaching into the soil,water,and air,and they are subsequently
taken up by plants,microorganisms,animals,and then humans through consumption of these
contaminated plants and animals.Such chemicals nd their way into tissue,causing endocrine-
linked pediatric disorders,reproductive dysfunction,cancer,neurobehavioral disorders,and
cardiometabolic impairment.
Alabi et al. (59)revealed that from 1950 to 2018,approximately 6.3 billion tons of plastic were
generated globally.An increase in the human population has also placed a huge demand on plastic
usage,resulting in a large amount of waste production,with accompanying health and environmental
issues.e authors noted that plastics are utilized in the production of many food packaging
containers,medical devices,and other household devices.ese plastics are constantly being
released into the ocean,resulting in the leaching of several toxic chemical components into water and
seafood.e authors further highlighted the fact that microplastic ingestion and bioaccumulation
by freshwater and marine organisms account for a wide range of health risks through exposure of
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humans to PUs.Consumption by animals and plants already exposed to the high content of PU
and microplastic additives will result in detrimental eects in humans,such as obesity,endometrial
hyperplasia,cancers,alteration in thyroid hormone axis gene expression,recurrent miscarriages,and
sterility.
Onwughara et al.(60)revealed that humans are exposed to PU and other toxic plastic chemicals
through the environment and food like dairy and meat products,with dierent pathophysiological
manifestations.Apart from the direct health implications,plastic debris and bags can also block
sewage or drainage channels,thereby creating stagnant water and providing appropriate breeding
sites for mosquitoes and other parasitic vectors with the potential to cause encephalitis,dengue
fever,or malaria.Barnes et al. (61)focused on the detrimental eects of plastic and microplastic
toxic chemicals in environmental and human exposure.e authors highlighted dierent health
risks that may emanate from exposure to these chemicals,such as irritation in the eye,breathing
diculties,vision failure,respiratory problems,cancers,liver dysfunction,skin diseases,headache,
lung problems,dizziness,reproductive dysfunctions,birth defects,cardiovascular disorders,
genotoxicity,and gastrointestinal damage.Proshad et al. (62)noted that PU is found in the plastics
utilized in the production of water boles,kitchen utensils,drink containers,food packages,and
cosmetics.is PU gets into some of the food and drink products and is consumed by humans,with
the resultant adverse eects on health and the environment.e authors revealed that PU and other
chemicals found in plastics can cause major health risks and environmental pollution such as birth
defects,cancer,genetic changes,ulcers,chronic bronchitis,skin diseases,vision failure,deafness,
indigestion,and liver dysfunction.ey showed that many of these chemicals in plastics used in
packaging and insulation for food and drinks are harmful to human health and very unsafe because
long-term exposure can cause hematological, neurotoxic, cytogenetic, and carcinogenic eects.
Wagner and Oehlmann (63)revealed that the health risks and environmental pollution that
may emanate from plastic usage could simply stem from chemical additives and monomeric building
blocks such as bisphenol A and PU.ese compounds are utilized for food packaging like baby
boles,food cans,and beverage containers,thereby leaching polymer compounds into the food
products from the inner lining especially under increased temperatures.e authors revealed that
these chemicals interfere with several hormonal systems to wreak serious havoc in humans,like
ovarian chromosomal damage,rapid onset of puberty,decreased sperm production,rapid changes in
theimmune system,breastcancer,pain,prostatecancer,metabolicdisorders,recurrentmiscarriages,
cardiovascular disorder,type 2 diabetes,endometrial hyperplasia,respiratory diseases,polycystic
ovarian syndrome,nervous system disorders,and obesity.Rudel et al. (64)revealed that
governments—particularly Bangladesh—who have witnessed plastic pollution over the years have
put in place rules and regulations to control the production and distribution of plastic across the
areas.A ban was instituted on plastic bags by the Bangladesh Ministry of Environment and Forest,
mobile courts,and the Ministry of Health to stop environmental pollution by plastic waste.Meeker
et al. (65)demonstrated that plastic toxicity is a global problem for the environment and for human
health due to chemicals such as PU and other additives used in the production.
Environmental Impact of PUs on Crops
Hahladakis et al. (55)revealed that increased plastic production has majorly impacted the
agricultural sector negatively through the release of toxic chemicals,such as PU and additives used
in plastics production,into the sea,ocean,and lands.e authors carefully highlighted some of the
waste management and pollution challenges concerning agricultural activity resulting from serious
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contamination of soil,water,air,and food.Exposure to PU in agriculture occurs via food packaging
processes, soil pollution moving into plants and crops, and animal feeds in contaminated foods.
Chen et al.(66)reported that the world’s population by the year 2050 will signicantly increase
to about 9 billion,so adequate preparation must be made to supply food and water to the ever-
increasing population.Despite the global projection for increased food production by the year 2030,
the quality and quantity of food products are currently being threatened by environmental
contamination from plastic pollution.It is generally known that the quality and nutritional status
of crops and food production greatly depend on soil physiology and physiochemical conditions to
provide the necessary ecosystem support for agricultural practices.e authors revealed that soil
pollution reduces food production and security through a reduction in yield,quality,and nutritional
contents.Generally,contamination can occur at any point in the food chain,like translocation
of pollutants through shoots,tubers,and fruits and then to humans through consumption of
contaminated agricultural food products.
Goesfeld et al. (67)revealed that crop production is generally aected directly or indirectly
through contamination from plastic waste and euents in the land,soil,and groundwater.Many of
the agricultural inputs from pesticides,fertilizers,and antibiotics are coated with plastics and may
be a source of great danger to agricultural lands and subsequently reduced crop production.e
authors showed that modern agricultural practices increase soil pollution due to increased usage of
chemical or synthetic fertilizers or pesticides,causing soil degradation,reduced crop productivity,
and environmental changes as a result of PU contamination from plastic waste.e authors
demonstratedthatthroughmicrobialactivityinbiodegradationof plastic waste,soil acidication may
increase through the release of chemicals like PU and other pollutants into the soil,thus reducing the
nutritional strength of plants, crop quality, and yield as a result of poor soil integrity.
Sarkar et al. (68)revealed that dierent natural and synthetic plastic polymers are utilized as
plastic mulch,resulting in environmental and human health risk concerns due to disposal and
degradation challenges.e authors revealed that in the agricultural sector,the utilization of plastic
mulch has increased signicantly because of its low cost and its ability to prevent pests and maintain
microclimate properties and conditions.is nondegradable plastic leaches into the soil to cause
serious damage to crops and groundwater,thereby reducing agricultural productivity.Apart from
plastic mulch,synthetic fertilizers are also being produced with plastic coatings using synthetic
polymers like PU and polystyrene,with tendencies to contaminate the soil and inltrate agricultural
produce.
Guart et al. (69)revealed how plastic additives and constituents migrate into the soil or food by
utilizing various kinds of migration tests.In their report,a toxicological evaluation was done to assess
the level of risk that consumers of this product are exposed to.e authors revealed that many of the
constituents of the plastic are known to cause metabolic and endocrine-disrupting properties with
other pathophysiological conditions in humans.e authors stressed that soil pollution as a result
of plastic contamination is on the increase globally,and many target organisms and ecosystems are
facing threats.Food insecurity as a result of soil pollution and reduced crop yield and productivity is
a major problem globally.Plastics contaminate aquatic and soil systems,thus posing a huge threat to
the terrestrial ecosystems that feed on both the aquatic animals and the contaminated plants,thereby
resulting in mutagenicity or cancer formation.
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Conclusion
is chapter has provided detailed information on the environmental application of PU in
diverse elds such as aquatic life,soil health,plants,and humans.Detailed information was
highlighted on the general chemistry of various PUs produced from chemical reactions of polyols and
isocyanate molecules to produce articial bers,sealants,adhesive,skateboards,elevators,shopping
carts,escalators,and roller coasters.e monomers of PUs were revealed to possess chains of
chemicals known to have negative environmental and health impacts due to the presence of
phosgene.us,the ndings from this study have established that polymers of PU might contain
hazardous materials such as phosphate,glycols,and amines that might be dangerous to the
respiratory tract, skin systems, and the environment.
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