ABSTRACT
Genotoxicity of freshwater fish in Anambra River was
studied by micronucleus (MN) assay, and the resultant micronucleus indices were
used as biomarkers to estimate and predict pollution profile and possible
danger of feeding on the aquatic species. The micronucleus profiles of the fish
were measured from gill and kidney erythrocytes using microscopic technique.
Season, breed, and location effects on micronucleus indices, together with
their interactions, and the correlation between the pollutants in fish, water
ecosystem, and the micronucleus profiles were also studied. Two major seasons
(Rainy and Dry) and preponderant fish breeds in the river [Synodontis
clarias -Linnaeus, 1758 and Tilapia nilotica -Linnaeus, 1757]
were studied at five distinct locations that displayed differential
environmental stresses. The study revealed that the micronucleus index of fish
is an excellent biomarker for measuring the level of pollution in a freshwater
habitat. This is more evident with regard to zinc and copper. Season, breed and
location affect micronucleus profile adversely and strong correlations exist
between zinc and copper in water and fish and micronuclei profiles. Disease
outbreak among rural dwellers depending on the water for domestic and other
uses is imminent and they lack knowledge on its health implication.
Furthermore, the study maintained that the micronucleus in fish could be
measured with higher efficiency from the gill than the kidney erythrocytes and Synodontis
clarias is more vulnerable to genetic damage due to high zinc and
copper pollutants than Tilapia nilotica. Consequently, the study
recommends environmental sensitization of the resident population and regular
monitoring (micronucleus tests) of edible aquatic life such as Synodontis
clarias (catfish) in order to eliminate the danger of people feeding
on toxic metals, some of which are carcinogenic.
CHAPTER ONE
INTRODUCTION
1.1 Background
Many toxic and potentially toxic chemical substances, some
of which are of natural origin and others due to human activities are available
in the fresh water ecosystem daily. It is difficult to practise even elementary
hygiene without sufficient quantities of water free of these contaminants
(UNFPA, 2001). As such, it is necessary to protect the water sources themselves
from faecal, agricultural, and industrial contaminations (pollutants). In
developing countries, 90 to 95 percent of all sewage and 70 percent of all
industrial wastes are dumped untreated into surface water (UNFPA, 2001). Due to
the increasing environmental exposure to these agents, the need for monitoring
terrestrial and aquatic ecosystems, especially in regions compromised by
chemical pollution is paramount (Mitchelmore and Chipman, 1998; Avishai,
Rabinwitz, Moiseeva and Rinkevch, 2002; Silva, Heuser and Andrade, 2003;
Matsumoto, Janaina, Mario, Maria, 2005).
Genotoxic pollution of aquatic ecosystem describes the
introduction of contaminants with mutagenic, tertogenic and/or carcinogenic
potentials into its principal media and genome of the resident organisms (Badr
and El-Dib, 1978; Environ Health Perspect, 1996; Fagr, El Shehawi and Seehy,
2008). Genotoxicity is a deleterious action, which affects a cell’s genetic
material affecting its integrity (Environ Health Perspect, 1996; WHO, 1997).
Several genotoxic substances are known to be mutagenic and carcinogenic,
specifically those capable of causing genetic mutation and of contributing to
the development of human tumors or cancers (Black, Birge, Westerman and
Francis, 1983; Hose, Hannah, Puffer and Landolt, 1984; Hose, 1985; Baumann and
Mac, 1988; Shugart, 1988; Hayashi,
Ueda, Uyeno, Wada, Kinae,
Saotome, Tanaka, Takai, Sasaki, Asano, Sofuni and Ojima, 1998; Fagr et al.,
2008). These include certain chemical compounds like heavy metals (Pruski and
Dixon, 2002; Lee and Steinert, 2003; Matsumoto, 2003; Matsumoto et al.,
2005; Igwilo, Afonne, Maduabuchi and Orisakwe, 2006) and polycyclic aromatic
hydrocarbons (PAHs) (Santodonato, Howard and Basu, 1981; IARC, 1983; Black et
al., 1983; Germain, Perron and Van Coillie, 1993). These genotoxicants have
been reported to cause mutations because they form strong covalent bonds with
deoxyribonucleic acid (DNA), resulting in the formation of DNA adducts
preventing accurate replication (Varanasi, Stein and Nishimoto, 1989; Hartwell,
Hood, Goldberg, Reynolds, Silver and Veres, 2000; Luch, 2005). Genotoxins
affecting germ cells (sperm and egg cells) can pass genetic changes down to
descendants (Hartwell et al., 2000) and have been implicated to be
against sustainable development principles by WHO (1997; 2002) portraying them
as significant factors in congenital anomalies, which account for 589,000
deaths annually.
Biomarkers are biological responses to environmental
chemicals at the individual level or below demonstrating departure from normal
status (NAS/NRC, 1989; Walker, Hopkin, Sibly and Peakall, 2003). Biomarker
responses may be at the molecular, cellular or ‘whole organism’ level. An
important thing to emphasize about biomarkers is that they represent
measurements of effects (Biomarkers of effect), which can be related to the
presence of particular levels of environmental chemical (Biomarkers of
exposure); they provide a means of interpreting environmental levels of
pollutants in biological terms. It is an indicator of an inherent or acquired
limitation of an organism's ability to respond to the challenge of exposure to
a specific xenobiotic substance (Biomarkers of susceptibility). It can be an
intrinsic characteristic or pre-existing diseases or activities that may result
in an increase in absorbed dose required for biological effectiveness, or a
target tissue response (NAS/NRC, 1989). Fish are excellent subjects for the study of the
mutagenic and carcinogenic potential of contaminants present in water. This is
so because they can metabolize, concentrate, and store waterborne pollutants
(Park, Lee and Etoh, 1993; Ali and El-Shehawi, 2007). Since fish often respond
to toxicants in a similar way to higher vertebrates with fast responses on low
concentrations of direct acting toxicants (Poele and Strik, 1975; Koeman, Poel
and Sloof, 1977; Poele, 1977; Sloof, 1977; Badr and El-Dib, 1978), they can be
used to screen for chemicals that are potentially teratogenic and carcinogenic
in humans. The main application for model systems using fish is to determine
the distribution and effects of chemical contaminants in the aquatic
environment (Al-Sabti and Metcalfe, 1995).
Micronucleus (MN) assay is an ideal monitoring system that
uses aquatic organisms to assess the genotoxicity of water in the field and in
the laboratory. Research reports maintained that it can be applicable to
freshwater and marine fishes and that gill cells are more sensitive than the
hematopoietic cells to micronucleus inducing agents (Hayashi et al.,
1998). Micronuclei are cytoplasmic chromatin-containing bodies formed when
acentric chromosome fragments or chromosomes lag during anaphase and fail to
become incorporated into daughter cell nuclei during cell division (Palhares
and Grisolia, 2002; Fagr et al., 2008). This genetic damage arises as
results of chromosome or spindle abnormalities leading to micronucleus
formation. Recent research reports maintained that micronucleus formation in
freshwater and marine fish is a function of water pollution caused primarily by
heavy metals and polycyclic aromatic hydrocarbons. According to Hartwell et
al. (2000) and Fagr et al. (2008), the incidence of micronuclei in
fish and other aquatic lives serve as an index of these types of damage and
counting of micronuclei is much faster and less technically demanding than
scoring of chromosomal aberrations. The micronucleus assay has been widely used
to screen for chemicals that cause these types of damage (Kligerman, 1982; De
flora, Vigario, D’
Agostini, Camoirano,
Bagnasco, Bennecelli, Melodia and Arillo, 1993; De flora, Vigario, D’ Agostini,
Camoirano, Bagnasco, Bennecelli, Melodia and Arillo, 1993; Campana, Panzeri,
Moreno and Dulout, 1999; Palhares and Grisolia, 2002).
Ability of the water body to support aquatic life as well
as its suitability for other uses depends on many factors among which are trace
element concentrations. Some metals such as manganese, zinc, copper, nickel,
when present in trace concentrations are important for the physiological
functions of living tissue and regulation of many biochemical processes
(Rainbow and White, 1989; Sanders, 1997). Generally, trace amount of metals are
always present in freshwaters from the weathering of rocks and soils. In
addition, industrial wastewater discharges and mining are other sources of
metals in freshwaters. Through precipitation and atmospheric deposition,
significant amounts also enter the hydrological circle through surface waters
(Merian 1991; Robinson, 1996).
Some metals when available in natural waters at higher
concentration in sewage, industrial effluent or from mining and refining
operations can have severe toxicological effects on aquatic environment and
humans (Merian, 1991; DWAF, 1996). In addition, heavy metal becomes toxic when
a level is exceeded; it then damages the life function of an organism
(Albergoni and Piccinni, 1983).
Various physical parameters such as temperature, pH, water
hardness, salinity, and organic matter can influence the toxicity of metals in
solution (Bryan, 1976; Dojlildo and Best, 1993; DWAF, 1996). Also, the lack of
natural elimination process for metals aggravates the situation (Emoyan et
al., 2006). As a result, metals shift from one compartment within the
aquatic environment to another including the biota often with detrimental
effects, through sufficient bioaccumulation. Food chain transfer also increases toxicological risk
in humans (Rainbow, 1985; Mason, 1991). Bioconcentration or bioaccumulation of
heavy metals over time in aquatic ecosystems has been reported by Koli, Canty,
Felix, Reed and Whitmore (1978); Alabaster and Lloyd (1980); Spear (1981);
Friberg, Elinder, Kjellstroem and Nordberg (1986); Fischer (1987); Clark
(1992); and Kiffney and Clement (1993) in developed countries such as U.S.A, UK
and Canada while Oyewo (1998); Otitoloju (2001); Groundwork (2002); Don-Pedro,
Oyewo and Otitoloju (2004) and Aderinola, Clarke, Olarinmoye (2009) reported
similar trend in Nigeria for various Lagos Lagoon epipelagic and benthic
organisms and Obodo (2004) and Agboazu, Ekweozor and Opuene (2007) in fish (Synodontis
membranaceus and Tilapia zili; and Synodontis clarias)
from Anambra River and Taylor Creek, respectively. The distribution of
heavy metals (Ni, Cd, Pb and Cu) in bank sediment and surface water column of
Anambra River, Otuocha axis, has been investigated by Igwilo et al.
(2006) in a single sampling period. According to Mason (1991), heavy metal
pollution is one of the five major types of toxic pollutants commonly present
in surface and ground waters. The environmental pollutants tend to accumulate
in organisms and become persistent because of their chemical stability or poor
biodegradability and that they are readily soluble and therefore
environmentally mobile, forming one of the major contributors to the pollution
of natural aquatic ecosystems (Purves, 1985; Sanders, 1997).
Polycyclic aromatic hydrocarbons (PAHs) are one of the
most widespread organic pollutants (BBC News, 2001). As a pollutant, they are
of concern because some compounds have been identified as carcinogenic,
mutagenic and teratogenic (Larsson, 1983; IARC, 1983; Black et al.,
1983; Germain et al., 1993). Though they occur naturally through
such events as forest fires (NRCC, 1983), human activities can
exacerbate their spread and are considered the major source of release of PAHs
to the environment (Neff, 1979; NRCC, 1983). These
activities include accidental oil spills, municipal and industrial effluents
discharge, and disposal of wastes containing PAHs (Jackson, Patterson, Graham,
Bahr, Bélanger, Lockwood, and Priddle, 1985). These organic pollutants can accumulate
in freshwater organism. Bioconcentration factors (BCF) have been reported in
some organisms (Lu, Metcalfe, Plummer and Mandel, 1977; Casserly, Davis, Downs,
and Guthrie, 1983; Mailhot, 1987) and effects detected using limited number of
biomarkers (Shugart, 1988; Hose, 1985). Physical factors such as temperature,
pH, dissolved oxygen, and hardness have also been documented to enhance the
toxicity of PAHs in freshwater organisms (Finger, Little, Henry, Fairchild and
Boyle, 1985; Black et al., 1983; Trucco, Englehardt and Tracey, 1983;
Call, Brooke, Harting, Poirier and MacCauley, 1986; Oris, Tilghman and Tylka,
1990). Organic pollutants considered here are examples of xenobiotics (foreign
compounds). They play no part in the normal biochemistry of living organisms.
However, apart from the adverse biodiversity effects
imposed by the aquatic chemicals, changes are much more important from a human
perspective, where human demands are placed on the aquatic system. Potable
water in residential user communities around Anambra River is essential for
human survival. Freshwater supply for human consumption should not only be safe
but also wholesome (Kapoor, 2001), free from harmful chemical substances,
pleasant in appearance, odour, taste and usable for drinking purposes (Kapoor,
2001). Pathetically, in rural communities, potable water is collected from
unprotected streams and rivers that are distant and prone to various material
loadings that affect its quality, biota, and health of the dependent population.
In view of the growing scarcity of water resources and its recently
acknowledged non-renewability, it is becoming important to plan its
sustainability, safeguard and improve human conditions and enhance development.
Currently, the situation is perhaps far-fetched as the ignorant pollution and consumptions of freshwater
resources are almost becoming acceptable trends, which potentially predispose
human population to possible disease outbreak and ecological damage.
1.2 Statement of the Problem
Rivers are highly prone to material loadings that can
result in pollution. According to Odo (2004), Anambra River is a shallow and
fragile ecosystem that has suffered drastic changes in the past years from
pollution of its waters. The River has secchi disc ranging from 25cm to 85cm
(Odo, 2004). Its setting in a tropical humid environment with potential
hydrological instability makes the river very vulnerable to degradation. It
receives mean annual rainfall of 150cm-200cm (Awachie and Hare, 1977; Ilozumba,
1989). This together with point source pollution from industries and
surrounding urban areas and non-point sources from agricultural lands has
brought serious environmental concerns of genotoxic pollution and the
sustainability of this resource.
There is a strong evidence of the serious reduction in
local biodiversity of the river as a result of pollution. Ndakide (1988) and
Odo et al. (2009) maintained that very low number of fish species
recorded at Nsugbe, Otuocha and Ogurugu stations of the river has been as a
result of synergistic effects from the various industries and growing
population impact. These effects arise as a result of discharge of municipal
wastes/sewage and individual pollutants (Odo, Didigwu and Eyo, 2009). Toxic
effect of detergents, petroleum products, and household factories had been
documented (Omoregie, 1995). Both the numbers and distribution of large mammals
in the river have been greatly reduced due to increased human influence such as
hunting and burning (Ndakide, 1988). The present fauna in the river is
dominated by weed associated meso-predators (Welcome, 1979).
The water quality of the
rivers discharging into Anambra River is the main determining factor of the
water quality status of the River. For example, Oyi River discharging in
Anambra River is the main collecting medium of municipal sewage, industrial
effluents and human domesticates for more than seventeen years now.
Reconnaisance tour to various regions surrounding the
river revealed crop agricultural and fishery production within the zone
including the floodplains. About 15 percent of all irrigated cropland suffers
from waterlogging and possibly, salinization due to drainage problems, thereby
resulting in reduced crop yields. Soil fertility improvement is mostly based on
application of inorganic fertilizer, especially during the dry season while
natural spontaneous flooding takes care of crop yield during the rainy season
along the floodplains, an earlier observation also documented by Anyanwu
(2006). According to the author, the river is gradually becoming eutrophic. Use
of agrochemicals was also evident. Despite the campaign against the use of
lethal chemicals in fishing, strong empirical evidence abounds that fishermen
use poisonous chemicals especially gamalin-20 in fishing. Because of early
decaying potentials of such treated fish, they are often smoke-dried
immediately after harvesting beside the river and at their organized camps. The
inefficient use of fertilizers and pesticides is also a major cause of
pollution of both surface and ground waters (FAO, 2002). Indiscriminate dumping
of wastes, industrial, domestic and marketing activities are common practices
at the river. Two major markets (Otuocha and Otu Nsugbe) are located on the
bank of the river.
The residents around the river complained of their source
of drinking water being polluted through effluent discharge and other
activities, fish diversity declining with resultant adverse effects on the
bio-economic values of the area such as occupations of the fishermen and local
food menu. Consequently, the thrilling part was that they excluded their agricultural, marketing, and
domestic activities as agents adversely influencing the river. However, the
truth remains that the inhabitants are outrightly ignorant of long time health
implications that could arise from the consumption of water and aquatic edibles
of the river. The residents erroneously quoted and believed that anything in
water does not kill, a primitive juggernaut maintained by them throughout the
eco-survey. In addition, aquaculture, which is the major source of animal
protein for the rural dwellers and beyond is not safe. For sustainability,
there is need to itemize the chemical pollutants of this river; the toxicity of
the aquatic life; the possibility of disease outbreak among the users and
possible precautionary measures. Such study can easily be carried out using
fish micronucleus biomarkers.
Ozouf-Costaz et al. (1990) reported that the
Karyotype and chromatin materials of Clarias gariepinus (Burchell, 1822)
are very stable. They observed no detectable Karyotypic differences among the
species derived from three different geographical areas. Similarly,
karyological and chromosomal analysis of the same species by Okonkwo and
Obiakor (2009) confirmed uniformity in Karyotypic polymorphism. However, they
reported chromosomal aberrations among the resident Clarias gariepinus
of the Anambra River sourced from different locations. These observations
implied that chemical pollutants of genotoxic potentials have been introduced
into the physiological functions of these native species (Okonkwo and Obiakor,
2009). Hence, this work was designed to identify these pollutants, which have
genotoxic potentials.
At
the end of the study, answers would have been provided for the following
questions:
1.
What are the preponderant
pollutants in Anambra River and aquatic lives?
2.
What is the effect of seasonal
changes and location on the availability and magnitude of the pollutants in the
river?
3.
Among Tilapia nilotica
(Linnaeus, 1757) and Synodontis clarias (Linnaeus, 1758), which breed is
more vulnerable or susceptible to chromosomal damage due to pollutants?
4.
What is the relationship between
the micronucleus profile in the fish and water and the pollutants detected in
them?
5.
What is the differential
genotoxicity with its attendant mortality response of the prominent heavy
metals in the river, acting singly and jointly against some test animals?
6.
What is the indication that the
level of pollution of the river can lead to disease outbreak among the user
population?
7.
What is the extent of knowledge
about the health implication of using the river among the residents?
8.
What are the possible remedies and
recommendations for the management of the river?
1.4 Research
Aim and Objectives
The
aim of the study is to evaluate the genotoxic pollution of the Anambra River,
Anambra State of Nigeria using micronucleus assay in fish genome.
The
specific objectives are:
1.
To determine the heavy metal and
polycyclic aromatic hydrocarbon (PAH) contents of the river and two fish
species (tilapia and catfish) using atomic absorption spectrophotometer and gas
chromatography.
3.
To test the breed effect of these
chemical pollutants.
4.
To establish the relationship
between the micronuclei indices of the fish and heavy metals and PAHs detected
in them and water.
5.
To investigate the differential
genotoxicity/mortality of heavy metals found to be most prominent in the
Anambra River, acting singly and jointly against the test animals based on
ratios of individual 96hLC50 values.
6.
To investigate the indication that
the level of pollution of the Anambra River can lead to disease outbreak among
the user population.
7.
To investigate the level of
awareness among the user population about the health implication of using the
river.
8.
To recommend measures for the
management of this resources of multiple uses.
1.5 Research
Hypothesis
The
work tested the following research hypotheses;
Hypothesis
1
HO
– There is no significant indication that the level of pollution of the Anambra
River can lead to disease outbreak among the user population.
Hypothesis
2
HO
– The level of knowledge/ awareness among the population about the health
implication of using the Anambra River is high and effective.
The aquatic environment makes up the major part of our
environment and resources. Therefore, its safety is directly related to the
safety of our health and food security. The most compelling reason for using
biomarkers in environmental risk assessment is that they can give information
on the effects of pollutants. Thus, the use of biomarkers in biomonitoring is
complementary to the more usual monitoring involving the determination or
prediction of residue level. Biomarkers and bioindicators using fish
micronucleus assay in eco-genotoxicology offers several types of unique
information not available from other methods. These include:
-
early warning on environmental
damage;
-
the integrated effect of a variety
of environmental stresses on the health of an organism and the population,
community, and ecosystem;
-
relationships between the
individual responses of exposed organisms to pollution and the effects at the
population level;
-
early warning of potential harm to
human health based on the responses of wildlife to population; and
-
the effectiveness of remediation
efforts in decontaminating waterways (Villela, De Oliveira, Da Silva and
Henriques, 2006).
Why use biomarkers in hazard assessment? One important
reason lies in the limitations of classic hazard assessment. The basic approach
of classic hazard assessment is to measure the amount of the chemical present
and then relate that, via animal experimental data, to the adverse effects
caused by this amount of chemical. The limitation of this approach is that only
for a very few compounds has it been possible to define the levels of a
chemical that are critical to an organism (Walker et al., 2003). Under
real life situations, a wide variety of organisms is exposed to complex and
changing levels of mixtures of pollutants. Biological and chemical monitoring systems should be
complementary to each other. It is important to know both what is there and
what it does.
The first question that biomarkers can be used to answer
is ‘are environmental pollutants present at a sufficiently high concentration
to cause an effect? If the answer is positive, further investigation to assess
the nature and degree of damage and the casual agent or agents is justified. If
negative, it means that additional resources do not have to be invested (i.e.
it is an early warning system). The role of biomarkers in environmental
assessment is envisaged as determining whether or not, in a specific
environment, organisms are physiologically normal. A suite of tests can be
carried out to see whether the individual is healthy. It is necessary to select
both the tests and the species to be tested. It is important to see that the
main trophic levels are covered and not to rely completely on organisms at the
top of the food chain. In the selection of tests, the specificity of the test
to pollutants and the degree to which the change can be related to harm need to
be considered. The use of biomarkers to measure responses to the chemical in
individual organisms can provide a casual link between exposure to a chemical
and a change at the population level (e.g. population decline, decline in
reproductive success or increased mortality rate) as would be explained in this
research with vulnerability effects to other organisms (e.g. resident human
population).
An exciting feature of eco-genotoxicology is that it
represents a ‘molecule to ecosystem’ approach, which relates to the
‘genes-to-physiologies’ approach originally identified by Clarke (1975) and
extensively developed in North America in the 1980s (see for example Feder,
Bennett, Burggren, and Huey, 1987). Freshwater pollution due to heavy metals
poses serious problem because of its high toxicity and of the bioaccumulation
ability of these agents. Priority organic pollutants (POP) like polycyclic
aromatic hydrocarbons (PAHs) have not
received considerable attention in environmental management thereby undermining
their lethal and sub-lethal effects. These pollutants have been reported to be
eco-toxic in developed countries (Germain et al., 1993). However, little
or no information exists in Nigerian Rivers, particularly Anambra River.
Studies of this type would invariably establish the heavy metal status and PAHs
concentrations within the river and call for proactive measures in control.
Genotoxic evaluation of the Anambra River is a key
mechanism for translating the principle of sustainable development into action.
Genotoxic pollutants have been associated with gene mutation (mutagenic) and
proliferation of tissue (carcinogenic potential). These chemicals are capable
of transforming the future generations if unchecked since it can affect the genetic
materials of the future population. According to Okpokwasili (2009), though
fish are dying first due environmental pollution, next is human.
1.7 Significance
of Study
The
research would be of immense benefit to the following categories;
Medical Practitioners and Epidemiologists: Due to the increasing environmental exposure to many toxic and potentially toxic chemical substances, the study will provide essential tools to clinical personnel on particular outbreak of congenital anomalies and diseases.
Medical Practitioners and Epidemiologists: Due to the increasing environmental exposure to many toxic and potentially toxic chemical substances, the study will provide essential tools to clinical personnel on particular outbreak of congenital anomalies and diseases.
Resident Population: The
indigenes around the area will be sensitized by this work on their
various inactions and negative influences on the river and ultimately be
educated on the permanency of the health effects of these activities.
Socio-economy: Aquaculture will
be maintained and sustained –following the recommended management
approaches in this work. The fish species, which form the major food in the
diet of the resident population and beyond would be made safe and
support the burgeoning population indefinitely.
Government: The quality state
of the major river of the state will be portrayed to the government, for
stricter regulations and monitoring of the state freshwater systems for the
protection of aquatic life and forestall water quality decay.
Environmental Managers: The
bio-techniques employed in this work will form major eco-tools for
eco-managers in monitoring and predicting impacts of aquatic pollution and at
the population level.
The work will provide a baseline data for the assessment
of the status of priority organic pollutants (POP); determination of management
mechanisms and ultimately, of regulatory measures of freshwater resource of
Anambra River aimed at the protection of its habitat and astronomical improvement
of fishery resources of the river.
The methodology applied for this research would serve as a
fundamental procedural step in evaluation of the genotoxic potentials of other
aquatic bodies.
1.8 Scope of Study
This study was designed to evaluate the genotoxic
pollution status of the Anambra River. The two preponderant fish species were
examined for micronuclei profiles. The values obtained served as indices of
chemical pollution of the river and contamination of the aquatic life. The water
and fish samples were also analyzed for metal ions and polycyclic aromatic
hydrocarbons (PAHs) contents known to be genotoxic by atomic absorption
spectrophotometer and gas chromatographic (GC) technique. The physico-chemical characteristics were
measured to determine the factors that enhance the environmental mobility and
bioavailability of these pollutants.
The work spanned between rainy and dry seasons to
determine the effect of seasonal changes on the above parameters. Also, the
breed and location effects were evaluated to measure the susceptibility
difference between the preponderant fish species and the locations with
significant degree of the chemical pollution impacts. It was limited to the
stretch of Anambra River excluding its tributaries. Differential
genotoxicity/mortality of two heavy metals found to be most prominent in the
Anambra River, acting singly and jointly against the test animals based on
ratios of individual 96hLC50 values were also evaluated. Public survey was
embarked upon to ascertain the level of awareness on health implication and
susceptibility/ indication that the level of pollution could lead to disease
outbreak among the resident population operating at, and using the ecologically
stressed river.
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