1.1.
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.

 

1.2.
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.

 

2.
REVIEW OF LITERATURE

§  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.)

 

 

3.
AIM AND OBJECTIVES

3.1.
Aim

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

 

3.2.
Objectives

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

§ 
To
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.

 

4.
MATERIALS AND METHODS

4.1.
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
filtered.

 

4.2.
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. 

 

4.3.
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 spectroscopy.

 

4.4. Atomic Absorption
Spectroscopy

A
similarly obtained and treated sample was given for Atomic Absorption
Spectroscopy analysis and results obtained by absorbance at 216.9nm.DISCUSSION: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.  7.
FUTURE PERSPECTIVEThe 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. 8.
SUMMARYLocally 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.