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1. Introduction

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Lead as a Toxicant and Poison

Lead contamination in fish

2. Review of Literature

3. Aim and Objectives



4. Materials and Methodology

Sample collection and preparation

Preparation of standard lead solutions

UV-Spectroscopy Analysis

Atomic Absorption Spectroscopy

5. Result

6. Discussion

7. Future Perspective

8. Summary

9. References


Figure 5.1. Standard graph for
concentration of lead (ppm) by UV-Vis Spectroscopy

Figure 5.2: Lead concentration in fish
sample by Atomic Absorption Spectroscopy


Table 5.1. Concentration of lead in fish
sample determined by AAS




Lead as a Toxicant and Poison

Lead has long been studied as a toxicant because
of its high potential to cause various detrimental health effects. Chronic lead
toxicity is quite common and can lead to irreversible health afflictions
relating to the renal system, central nervous system, and hepatic system among
others. Lead acts as an enzyme inhibitor by binding to proteins including
enzymes. Organic lead compounds which are highly toxic are taken up easily by
the human body. Chronic lead poisoning can cause anaemia, extreme fatigue, and
when it gets accumulated in high quantities, can cause damage to various organs
of the body.


Lead contamination in fish

While the most studied ways of lead
contamination are via paints, contaminated soil and drinking water, lead in food;
specifically from lean meats and fishes is being increasingly looked into. Toxins
released into water bodies are taken up by fishes via their feed as well as
through their gills. Lead, a common toxicant is mainly found in fish muscles,
gills and the liver. Due to bioaccumulation and biomagnifications, the lead is
not degraded and passes on from the contaminated fish to other animals that
consume it, including humans.



§  In
2005, William G. Brumbaugh and Christopher Schmitt studied and compared the
concentrations of Cadmium, Lead and Zinc in fish from mining influenced waters
of Northeastern Oklahoma. Despite mining having ceased in this region more than
30 years ago, the heavy metal wastes remain widely distributed. Liver, blood
and carcass samples from common carp, bass and catfish were analysed using
Inductively coupled plasma mass spectroscopy (ICP-MS). Common carp was found to
have the highest amount of lead. (Ref.)


§  From
2011-2012, Elin Boalt, et al carried out a study on the presence of lead,
mercury and cadmium in Baltic herring and perch from the Bothnian sea. The
samples tested were dorsal muscle layer, liver and carcass homogenate. Lead was
reported most often in the carcass homogenate and liver. (Ref.)


§  Rohasliney
Hashim et al studied the levels of lead, cadmium and nickel in fish collected
from the Kelatan river in 2014. The dorsal muscle tissue from 13 fish species
was the analyte and the study was carried out using a graphite furnace atomic
absorption spectrometer. Omnivorous fish were found to have high levels of
cadmium and nickel while carnivorous fish had the highest concentration of
lead. The species O. Hassetti and T. Maculates had lead concentrations that
exceeded FAO Malaysian Food Act and WHO guidelines. (Ref.)


§  Shovan
MNH et al, in the June, 2017; conducted a study to determine the levels of
heavy metals in the various organs of 3 commonly consumed fishes in Bangladesh
– Catla, Pangus and Rohita using
Atomic Absorption spectrophotometry. The gill of the Pangus fish was found to
have the highest concentration of lead (~48.3 ppm) that had far exceeded the
limits of WHO. (Ref.)


§  The
concentration of heavy metals in farm sediments, feed and selected heavy metals
in various tissues of farmed Pangasius
hypothalamus in Bangladesh were
studied by Das et al in July, 2017. The concentration of lead, cadmium, nickel
and mercury were below WHO recommended limits but their concentration in the
gills, kidney and liver of the fish were high above the tolerable level and
hence the fish are unfit for human consumption. (Ref.)




To determine the concentration of lead
(Pb) in locally consumed fish species, Lutjanus
gibbus and if they are fit for human consumption.



§  To standardise a spectrophotometric method for the
determination of trace amounts of lead in the homogenized carcass of Lutjanus gibbus

compare UV spectophotometry and Atomic Absorption Spectophotometry as methods for
determining trace amounts of lead in fish.

§  To estimate whether the sample is suitable for food or
feed based on World Health Organization – Maximum Level standard.



Sample collection and Preparation

Lutjanus gibbus was
obtained from a roadside fisherwoman in Anna Nagar West who is frequented by
the residents of the place. The particular species was chosen because it is
among the commonly solf species of edible fish in the market. The fish was kept
in the deep freezer until it was to be used for the experiment. For chemical
analysis, homogenization was done using sodium phosphate buffer and the extract


Preparation of standard Lead Solutions

A 100 mL stock solution of lead was
prepared by dissolving 160 mg of lead acetate in double distilled water. The
solution was standardized with EDTA using methyl blue as indicator to determine
the concentration of lead in it. A series of standard solutions ranging from
25-150 ?g of lead were prepared. 


UV-spectroscopy Analysis

To the standardized lead solutions ranging
in concentration from 25-150 ?g, 1.5 mL of            1.95 X 10 -4 M dithizone
solution was added. This was followed by adding 1 mL of 4 X 10 -3 M
HCl and 4mL of 0.3 M CTAB (Cetyltrimethylammonium
bromide). The mixture was made upto 10mL with double distilled water. The
absorbance was measured at 500nm against a suitable reagent blank. The
absorbance values of standard lead solutions were plotted to produce a
calibration graph. The absorbance value of the sample was also determined by UV


4.4. Atomic Absorption

similarly obtained and treated sample was given for Atomic Absorption
Spectroscopy analysis and results obtained by absorbance at 216.9nm.




Figure 5.1. Standard
graph for concentration of lead (mg/L) (ppm) by UV-Vis Spectroscopy




Table 5.1.
Concentration of lead in fish sample determined by AAS




Sample ( Lutjanus gibbus)

Concentration of lead (ppm)

















Figure 5.2: Lead concentration in fish
sample by Atomic Absorption Spectroscopy





The lead concentration in the sample was
assessed by Atomic Absorption Spectroscopy (AAS). The obtained value of 1.46
ppm is less than the maximum permissible values set by the WHO of 2 ppm. Hence
the fish is suitable for consumption. But, if more fish of the same species is
consumed, there is a risk of the lead concentration crossing the permissible
limit, and thus possibly being harmful to the consumer, also, as lead has the
ability to bioaccumulate and biomagnify, if this fish species were to be consumed
by other predatory fish, it could further increase the lead concentration in
the fishes eventually consumed by humans.

Initial testing was carried out using a
UV/Spectrophotometer at 500nm. But the resultant absorbance was much higher
than the WHO standard limit of 2ppm and did not fall within the calibration
graph obtained.

Youngsters are more vulnerable to the
deleterious effects of trace amounts of lead and can suffer from permanent
adverse health defects, mostly affecting the brain and nervous system
development. Lead can cause long-term health impairment in adults, such as high
risk of blood pressure fluctuations, and damage to kidneys. Exposure of high
levels of lead to pregnant women can cause stillbirth, low baby weight,
premature birth etc.




The concentration of lead in various fish
species could be studied and compiled. This would give an idea as to the
overall lead intake of an average person in the locality who consumes fish from
the same source.



Lead is a common
heavy metal contaminant found in food. As most industries dispose their wastes
into water bodies, lead, a common toxicant becomes widespread in these water
bodies. The fish inhabiting the water body take up the lead via their gills and
through their diet. Due to years of bioaccumulation and magnification, the
concentration of lead increases within the fishes inhabiting the water body. At
high levels, the lead can cause adverse health defects in fish including
mortality. When lead contaminated fish are taken up by humans, the trace lead
amounts can cause a multituve of health problems.

Locally obtained Lutjanus
gibbus was spectrophotometrically analysed for presence and
concentration of lead; both by an UV-Vis Spectrophotometer (Lead-dithizone
system in a HCl medium) and an atomic absorption spectrophotometer.

The obtained
concentration of 1.46ppm while lesser than the WHO maximum limit of 2ppm, still
poses a threat to the health of consumers as lead has the ability to
bioaccumulate and biomagnify.

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