This document discusses assessing heavy metal concentrations in fish tissues from fish cultured with adulterated feeds contaminated with heavy metals. The study aims to determine bioaccumulation and distribution of toxic heavy metals in commercial fish tissues and assess potential health risks from consuming contaminated fish. Fish will be exposed to feeds containing varying concentrations of heavy metals and their tissues will be analyzed for heavy metal content using atomic absorption spectrophotometry. Risks to human health from ingesting contaminated fish will be estimated. The findings could show whether fish cultured with heavy metal contaminated feeds are safe for human consumption.

1. BACKGROUND
Fisheries sector plays an important role in the economy and livelihood of
Bangladesh in terms of nutrition, employment and export earnings.
During 1992-2017, fish production has increased by more than three folds from
1.2 million mt to 4.10 million mt.
 As a consequence, Bangladesh attained 4th position in the globe in freshwater
aquaculture production.
The present per capita annual fish consumption in Bangladesh stands at about 14
kg/year against a recommended minimum requirement of 18 kg/year; hence there
is still need to improve fish consumption in the country.
 Fish remains by far the most important and frequently consumed animal source
food in Bangladesh, but studies on fish consumption show very substantial
variation depending on location, income and season.

2. BACKGROUND
Growth of aquaculture has been supported by development of input businesses and
suppliers, in particular those related to production of seed and feed.
‘Raw’ unformulated feeds are widely used in homestead and commercial carp
aquaculture.
 The use of commercially manufactured pelleted feeds predominates in entrepreneurial
fish culture.
Forty major feed mills produced 0.67 million tonnes of formulated feeds, worth around
$220 million in 2010.
 Whilst feed supply has grown rapidly in recent years, quality remains a major concern.
High heavy metals like lead (Pb) and cromium (Cr) contents in adulterated commercial
feeds are already reported in some countries including Bangladesh.
 More attention should be given to the monitoring of toxic heavy metals in feed due to
inherent bioaccumulation and biomagnifications potentials and their long term persistence
in environmental compartments.

3. BACKGROUND
After introduction into the environment from a plurality of anthropogenic sources,
heavy metals may accumulate in aquatic life, enter the food chain and cause serious
harm to human health where contamination and exposure are significant.
Fish assimilate metals by ingestion of particulate material suspended in water,
ingestion of food, ion-exchange across lipophilic membranes (e.g., the gills), and
adsorption on tissue and membrane surfaces.
Levels of toxic heavy metals in aquatic biota are of particular interest because of the
potential risk to humans who consume them.
 The accumulation of heavy metals in the tissues can result in chronic illness and cause
potential damage to the population.
The aim of this study is to assess heavy metal concentrations in different tissues of
fishes cultured with adulterated feeds contaminated with heavy metals and quantify
health risk consequences from exposure through consumption of contaminated fish.

4. OBJECTIVE
(i) To determine the bioaccumulation and distribution of toxic heavy
metals in commercial fishes cultured with adulterated feeds
contaminated with heavy metals.
(ii)To assess the food safety and potential health risk for consumption of
heavy metals contaminated fishes.

5. METHODOLOGY
• Rearing of Experimental Fish with heavy metal exposures: To study the chronic
toxicity of heavy metals by detecting changes at the developmental, physiological,
biochemical or molecular levels, each of the 4 fishes will be released randomly in 30 L
glass aquarium and fed with feeds containing heavy metals. Oral exposure will be done
by adding heavy metals in feed. Feeds containing different concentrations of heavy
metals (i.e. 0 ppm or control, 25 ppm, 50 ppm, 100 ppm, 150 ppm, and 200 ppm,) will
be made by impregnating feeds with heavy metal solutions. Mortality, feeding
behavior, growth reduction, deformities and histopathological changes will be assessed
after rearing the fishes with heavy metals treated feed for upto 60 days.
• Sample collection: Fish samples will be collected from oral exposures of different
doses of heavy metals and will be kept frozen in the freezer pending heavy metals
analysis in the laboratory.

6. METHODOLOGY
• Sample preparation for heavy metal analysis: Heavy metal contents in different portion of fish will be
determined using Atomic Absorption Spectrophotometer following standard procedures.
• Human health risk assessment (Estimated daily intake and target hazard quotient)
• Estimated daily intake of heavy metals via ingestion route (fish) will be calculated using Eq. (1). The target
hazard quotient (THQ) was finally calculated using Eq. (2).
𝐸𝐷𝐼 =
𝐶 𝑋 𝐼𝑅 𝑋 𝐸𝐹 𝑋 𝐸𝐷
𝐵𝑊 𝑋 𝐴𝑇
………….…..(1) 𝑇𝐻𝑄 =
𝐸𝐷𝐼
𝑅𝑓𝐷
………………………..(2)
• Where C is the concentration of the metals in the sample (mg/kg), IR is the ingestion rate (kg/day), EF is
exposure frequency (365 days/year). ED is the exposure duration in years; RfD is the reference dose
(mg/kg/day). BW is the average adult body weight (kg), AT is the averaging time.
• Statistical analysis: Descriptive statistics, determination of one-way analysis of variance (ANOVA) and
post hoc tests will be conducted using Microsoft Excel 2010 and IBM SPSS Statistics 20.v

7. CONCLUSION
The fishes cultured with adulterated feeds contaminated with
toxic heavy metals are quite unsafe for human consumption if
the levels of heavy metals exceed the standard and acceptable
level. We will detect the distribution and bioaccumulation of
heavy metals in some fish species after heavy metals exposures
from adulterated feeds.