MISJ-International Journal of Medical Research and Allied Sciences

Online ISSN: 2584-1432

Available Online at https://ijmraas.misj.net Volume 04|Issue 01 (January - April) |2026 Page: 15-21

Open Access

Original Research Paper

Effects of Chronic Lead Exposure on Hematological Indices in Albino Rats

(Rattus norvegicus)

Authors:

Ofoegbu EC^1*and Onyeka PIK²

¹Prime British International College Owerri.

²Anatomy and Physiology Unit, Department of Animal and Environmental Biology Imo State University Owerri.

https://orcid.org/0009-0000-5590-497X

Corresponding Author:

Ofoegbu EC, Prime British International College Owerri.

DOI: https://doi.org/10.5281/zenodo.20251920

Received: 04-April-2026, Accepted: 20-April-2026, Online First: 25-April-2026

ABSTRACT:

This study was carried out to determine the effect of Lead Toxicity on the Physiology (Hematological indices) of Albino

Rats (Rattus norvegicus). Lead exposure remains a major environmental and public health concern due to its toxic

effects on hematological and physiological functions. A total of forty-eight (48) Albino Rats were procured and divided

into two experimental groups of twenty-four (24) Albino Rats per group. One group of rats was treated with lead in their

drinking water while the other was treated with lead in their feed. Also, a common control group which was made of

twelve rats. Each experimental group was made up of three treatments sub-group which consisted of different

concentration levels of 50 mg/kg, 100 mg/kg and 150 mg/kg. A one-way ANOVA was conducted to examine the effect

of lead toxicity on the hematological indices of albino rats. The results revealed that lead exposure produced statistically

significant effects on all parameters measured Hemoglobin (F (2,4) = 49.14, p = 0.002), PCV (F(2,4) = 13.44, p = 0.017),

WBC (F(2,4) = 29.62, p = 0.004), and RBC (F(2,4) = 21.06, p = 0.008). Post hoc analysis using the Tukey HSD test

showed that for each of these indices, the Control group differed significantly from both the Low and High lead exposure

groups (p < 0.05), indicating that lead toxicity markedly altered the hematological parameters. In particular, hemoglobin

concentration, PCV, and RBC counts decreased with increasing lead exposure, while alterations in WBC counts

suggested immune response activation associated with lead toxicity. However, the study was limited by the relatively

small sample size and lack of biochemical oxidative stress marker assessment. The results underscore the need for

regular monitoring of Hematological parameters in individuals exposed to lead.

Keywords: Lead toxicity, Hematological indices, Albino rats, Oxidative stress, Chronic exposure, Heavy metals

ways and harm wildlife. All these and many more are

examples of pollutants. The excessive amount of

pollutants such as heavy metals in animal feed and feed

stuff is often due to human action and their results from

either agricultural or industrial production or through

accidental or deliberate misuse (Adetunji, et al., 2020).

Heavy metals are generally defined as metals with

relatively high densities, atomic weights or atomic

numbers (Pourret, et al., 2021). Lead (Plumbum; Pb) is

a toxic heavy metal and a chemical element belonging

to the carbon group. It is soft, malleable, and widely

distributed in the environment due to industrial and

agricultural activities. Lead introduced into the blood

stream is excreted in urine and bile at a distinct rate of

1 to 3ml/min, with a half-life of roughly 30 days. The

remaining leads bind to red blood cells and are

distributed throughout the soft tissues of the body and

INTRODUCTION:

All living things, from one-celled microorganisms to

blue whales, depend on earth’s supply of air and water

to survive. When these resources are polluted, all forms

of life are threatened. Pollution is the introduction or

release of harmful materials into the environment.

Environmental pollution involves the presence of a

pollutant in the environment such as water, air, soil and

consequently in food which may be poisonous or toxic

and will cause harm to living things in the polluted

environment (Oguntimehin, et al., 2022). Many useful

things to humans produce pollution. These are referred

to as pollutants. Cars spew pollutants from their exhaust

pipes. Burning coal to create electricity pollutes the air.

Industries and households generate garbage and sewage

that can pollute the land and water. Pesticides-chemical

poisons used to kill weeds and insects-seeps into water

MISJ-IJMRAAS (January – April 2026)

Page | 15

BY 4.0). https://creativecommons.org/licenses/by/4.0/

eventually accumulate in bone. The half-life of bone-

deposited lead ranges from 20 to 30 years. Turnover of

bone tissue releases lead back into the bloodstream and

Physiological processes such as pregnancy, menopause,

and lactation may increase blood lead levels by

enhancing bone tissue turnover. Lead in the body is

measured with both blood and bone levels. Blood lead

levels are more reflective of acute exposure, whereas

bone lead levels better reflect cumulative exposure over

time (ATSDR, 2020). Lead is known to induce

overproduction of reactive oxygen species (ROS) and

consequently enhance lipid peroxidation, decrease the

saturated fatty acids, and increase the unsaturated fatty

acid contents of membrane (Hassan et al., 2020). Lead

has also been shown to enhance the production of

reactive oxygen species in a variety of cells, resulting in

oxidative stress (Li et al., 2022).

Imo State is among the 36 states of Nigeria and lies in

the South eastern region of the country. It lies within

Latitude: 5.4833° N, Longitude: 7.0333° E, with area of

about 5100sqk and a population of about 3,934899

(NBS 2022; NPC 2006). The research study was carried

out at the Animal house of the Department of Anatomy

and Neurobiology, Imo State University Owerri and

Sabconsults Research Laboratories Ltd Owerri

Ethical Consideration:

The study protocol was reviewed and approved by the

Research Ethics Committee of the Department of

Animal and Environmental Biology, Imo State

University, Owerri. All experimental procedures were

conducted in accordance with the National Research

Council (NRC) Guide for the Care and Use of

Laboratory Animals (2011) and complied with

ARRIVE guidelines for animal research reporting.

Efforts were made to minimize animal suffering and

reduce the number of animals used.

Although several studies have investigated lead

toxicity,

limited

information

exists

regarding

comparative hematological effects associated with

different routes of chronic lead exposure, particularly

through feed and aqueous administration. Therefore,

this study aimed to evaluate the effects of chronic lead

exposure on selected hematological indices in albino

rats using two different exposure models.

Experimental Sites:

The experiment was carried out in the Animal house of

the Department of Anatomy and Neurobiology, Faculty

of Medical Science, Imo State University, Owerri and

Sabconsults Research Laboratories Ltd Owerri.

Despite a number of recent studies (Lakshmi et al.,

2020; Nriagu, 2011; Adewuyi, and Adewuyi, 2018;

WHO, 2017), many aspects of normal lead metabolism

are poorly understood hence the research work will help

in formulating appropriate public policies and

regulation to protect individuals and communities. It

will provide scientific evidence to support initiatives

such as banning or restricting the use of lead in

consumer products, implementing lead testing and

remediation programs, and setting standards for safe

lead levels in different environments. The research

findings can guide public health interventions and

strategies to prevent and mitigate lead exposure; this

include targeted screening programs to identify

individuals at risk, educational programs to create

awareness and sensitize the populace on the effect of

lead toxicity on human health and interventions to

address lead-contaminated environments. It can also

help to inform healthcare professionals about the best

practices for lead poisoning prevention, diagnosis and

treatment. The research work will also help to identify

vulnerable population that are most affected by lead

toxicity, this information is crucial for targeting

intervention and resources to protect those at higher

risk, such as children, pregnant women, individuals

living in high risk environment, and certain

occupational groups. By understanding the specific

factors that contribute to lead exposure disparities,

researchers can help address social and environmental

justice issue related to lead toxicity.

Procurement and Management of Experimental

Animals:

48 rats within the age bracket of six (6) to ten (10) weeks

old were purchased from the suppliers and transported

to the Animal house of the Department of Anatomy and

Neurobiology, Imo State University Owerri. The rats

were allowed to acclimatize in the experimental animal

house for two weeks before the commencement of the

experiment. Animals were randomly assigned to the

experimental groups to minimize selection bias.

They were kept in stainless wire-rat cages equipped

with drinkers and fecal collecting trays in a clean

experimental animal house. The rats were fed with

broiler chicks mash. The faecal droppings were

removed daily. The rats were weighed with Mettler,

electronic balance PC 2000 during treatment. All the

rats in both treatment and control groups were allowed

free access to food and water, throughout the

experimental period. Good hygiene was maintained by

constant cleaning and removal of feces and spilled feed

from cages daily. They were separated into seven

experimental groups, including one control group and

six treatment groups.

Procurement, Preparation and Preservation of

Chemicals:

Lead was purchased from a chemical store at Relief

Market in Owerri Municipal. The desired doses 50

mg/kg, 100 mg/kg and 150 mg/kg (0.05%, 0.1% and

0.15%) that were used in this study was prepared with

distilled water. For treatment Group A while the same

measurement was mixed in the feed for treatment Group

MATERIALS AND METHODS:

Study Area:

MISJ-IJMRAAS (January – April 2026)

Page | 16

B. The remaining lead were stored in a cool dry place.

Lead chemicals can be prepared and preserved through

various methods, including the use lead oxide and lead

acetate (Osha, 2020)

KX-21 (Sysmex Corporation Kobe, Japan). The

principle is adapted to the volumetric impedance

method (Robinson and Wallace, 2013); in which total

white blood cells (WBC), red blood cells (RBC), are

directly measured using the DC detection method; while

a non-cyanide hemoglobin analysis method determines

haemoglobin (HGB). Other variables such as

hematocrit (HCT), is derived variable.

Experimental Design:

A total of 48 albino rats were used for this research

work. The experiment consisted of two major exposure

groups: lead administered through aqueous solution and

lead mixed in feed. Each exposure group was further

divided into three treatment subgroups (A, B, and C)

consisting of 6 rats per subgroup and exposed to 50

mg/kg, 100 mg/kg, and 150 mg/kg of lead respectively.

A separate control group received normal feed and

water under the same environmental conditions.

Dose selection was based on previous toxicological

studies demonstrating sub-lethal chronic lead exposure

effects in rodents. The sample size was determined

based on feasibility and previous similar experimental

studies. Both aqueous and feed-based exposure models

were selected to simulate different environmental

exposure routes.

Statistical Analysis:

Data were analyzed using Statistical Package for Social

Sciences (SPSS) version 20. Results are presented as

mean ± standard deviation (SD). Normality of data

distribution was assessed using the Shapiro–Wilk test

prior to parametric analysis. Differences among groups

were analyzed using one-way Analysis of Variance

(ANOVA) followed by Tukey’s post hoc multiple

comparison test. A p-value of ≤0.05 was considered

statistically significant.

RESULT:

Animals were randomly assigned to the different

experimental groups. The portal of administration

followed the oral exposure method described by Ekeh

et al. (2015). The experiment lasted for 8 weeks, during

which hematological parameters were monitored

periodically.

Table 1 showed a summary of the Hematological

Indices for the Albino rats across the entire study

period. Lead exposure, regardless of dose or method,

resulted in a significant decline in Hemoglobin

(HEMO), Packed Cell Volume (PCV), White Blood

Cells (WBC), and Red Blood Cells (RBC). For Red

Blood Cells (RBC), the Aqueous 50 mg/kg group

remained the closest to the control for Red Blood Cell

(RBC) count, the Aqueous 50 mg/kg group remained

closest to the control group., Also for White Blood Cells

(WBC), the Mixed in Feed groups (all doses)

maintained slightly higher WBC levels (WBC →

×10⁹/L) than the Aqueous groups (60.62–66.19 mg/dL).

The Packed Cell Volume (PCV) levels for all treated

groups dropped by approximately 13% to 16%

compared to the control. Table 2 showed that every

single lead-treated group recorded levels significantly

below the baseline of the control (12.50 and 12.60 g/dl).

The 100 mg/kg (aqueous group) dose dropped sharply

to 9.70 g/dl at Week 4 and By Week 8, the 50 mg/kg

dose was at its lowest point (10.10 g/dl). The lowest

dose in feed showed a very steady, progressive decrease

from 11.12 g/dl (Week 2) down to 10.35 g/dl (Week 8).

The 100 mg/kg dose showed a curious spike to 11.70

g/dl at Week 6 before falling back to 10.24 g/dl at Week

8. Table 3 revealed that the most severe drops were

generally associated with the higher concentrations

(100 and 150 mg/kg), of aqueous solution groups. The

100 mg/kg (aqueous solution) group showed a sharp

decline, starting at 40.60% in Week 2 and falling to

35.10% by Week 4. The 150 mg/kg group started low

(38.80%) and dropped further by Week 4 (36.20%). The

100 mg/kg dose in feed started at 32.40% at Week 2, but

then 38–40% for the remainder of the study. The 150

mg/kg dose showed a steady downward trend from

Week 2 (40.05%) to Week 8 (38.06%). Table 4 showed

that every lead-treated group remained below the

Group

Exposure

Dose

Control Normal feed/water 0

Aqueous lead

Feed mixed

50 mg/kg 6

100 mg/kg 6

150 mg/kg 6

50 mg/kg 6

100 mg/kg 6

150 mg/kg 6

Collection of Blood Sample and Preparation of

Serum Samples for Analysis:

The method adopted for the collection of blood and

serum preparation followed that of Hoff (2000). Blood

samples was collected from the animal with a Pasteur

pipette with the aid of capillary inserted at the corner of

the eye ball. The blood collected from the animals in the

different groups were introduced into clean 5 ml

centrifuge tubes. The blood samples were centrifuged at

a speed of 3000 revolutions per minute (rpm) for 5

minutes

(Ogbu

and

Okechukwu,

2001).

The

supernatants (sera) were collected and used for the

various biochemical and hematological analyses.

Hematological Indices:

The complete blood count was assessed using a multi-

parameter automated haematology analyzer Sysmex

MISJ-IJMRAAS (January – April 2026)

Page | 17

control baseline (20.12 to 20.50 cells/µl) throughout the

8-week study. Lead mixed in feed generally maintained

slightly higher WBC counts than lead in aqueous

solution, though both were still lower than the healthy

control. The 100 mg/kg dose (aqueous group) at Week

6 reached the lowest point at 13.40 cells/µl (a ~35%

decrease from control). The 50 mg/kg dose in feed

remained relatively stable but consistently suppressed,

hovering between 17.13 and 18.65 cells/µl. Table 5

presents that every lead-treated group, regardless of

dose or delivery method, showed a marked decrease,

with counts mostly staying within the 6.00 to 7.00 range

when compared to the control. In Aqueous Solution, the

100 mg/kg dose showed a steady reduction, ending at

6.20 by Week 8 and also both the 100 and 150 mg/kg

doses dropped significantly by Week 2. The group

(mixed in feed) recorded the lowest RBC counts, the 50

mg/kg dose dropped to 5.90 at Week 4, and the 100

mg/kg dose stayed consistently low (6.08–6.25) from

Week 4 onward.

Table 1: Effect of Chronic Lead Exposure on Hematological Indices of Albino Rats

Treatment Group

Hb (g/dL) PCV (%) WBC (×10⁹/L) RBC (×10¹²/L)

11.8 ± 0.5 40.2 ± 1.3 16.2 ± 1.1

10.9 ± 0.4 37.1 ± 1.5 14.8 ± 1.0

10.5 ± 0.6 36.4 ± 1.7 14.2 ± 1.2

11.4 ± 0.5 39.0 ± 1.4 17.4 ± 1.0

10.8 ± 0.4 37.8 ± 1.5 16.7 ± 1.1

10.6 ± 0.5 37.2 ± 1.6 16.1 ± 1.0

12.6 ± 0.3 44.5 ± 1.2 20.3 ± 0.9

7.30 ± 0.24

6.62 ± 0.28

6.45 ± 0.31

6.89 ± 0.26

6.40 ± 0.29

6.33 ± 0.30

8.01 ± 0.22

Aqueous Lead 50 mg/kg

Aqueous Lead 100 mg/kg

Aqueous Lead 150 mg/kg

Feed-Mixed Lead 50 mg/kg

Feed-Mixed Lead 100 mg/kg

Feed-Mixed Lead 150 mg/kg

Control

Values

are

expressed

mean

standard

deviation

(SD).

Hb: Hemoglobin; PCV: Packed Cell Volume; WBC: White Blood Cell Count; RBC: Red Blood Cell Count.

*p < 0.05 compared with control group.

Key:

HEMO: Haemoglobin

PCV: Packed Cell Volume

WBC: White Blood Cell

RBC: Red Blood Cell

Table 2: Weekly effect of Lead Toxicity on Hemoglobin (g/dl)

Treatment(mg/kg)

Week2

Week4

Week6

Week8

In Aqueous solution

100

150

10.20

11.30

10.24

11.10

9.70

11.70

12.00

10.20

11.30

10.10

10.60

10.20

Mixed in Feed

100

150

Control

11.12

10.15

11.20

12.60

11.05

10.20

10.35

12.50

10.18

11.70

10.24

12.50

10.35

10.24

11.10

12.60

Table 3: Weekly effect of Lead Toxicity on Packed Cell Volume (%)

Treatment(mg/kg)

Week2

Week4

Week6

Week8

In Aqueous solution

100

150

40.10

40.60

38.80

39.60

35.10

36.20

41.10

37.20

39.30

40.11

35.40

40.30

Mixed in Feed

100

150

Control

37.30

32.40

40.05

45.30

40.12

39.15

38.30

43.60

40.10

38.20

37.15

45.30

39.10

40.12

38.06

43.60

MISJ-IJMRAAS (January – April 2026)

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Table 4: Weekly effect of Lead Toxicity on WBC (×10⁹/L)

Treatment(mg/kg)

Week2

Week4

Week6

Week8

In Aqueous solution

100

150

15.10

14.83

14.98

16.32

17.20

17.81

13.40

15.56

16.96

15.20

14.37

Mixed in Feed

100

150

Control

18.11

19.11

18.32

20.12

17.13

17.02

15.86

20.50

18.65

16.35

18.02

20.50

17.32

18.24

16.28

20.12

Table 5: Weekly effect of Lead Toxicity on RBC (×10¹²/L)

Treatment(mg/kg)

Week2

Week4

Week6

Week8

In Aqueous solution

100

150

7.30

6.37

6.43

6.93

7.03

6.38

7.08

6.89

7.10

7.02

6.20

6.88

Mixed in Feed

100

150

Control

6.73

7.08

6.20

8.10

5.90

6.08

6.10

7.92

6.79

6.18

6.30

8.10

7.12

6.25

6.73

7.92

A major strength of this study was the comparison of

two different exposure routes (aqueous and feed-based

administration), which provided broader insight into the

hematotoxic effects of chronic lead exposure.

DISCUSSION:

In particular, haemoglobin concentration, PCV, and

RBC counts decreased with increasing lead exposure,

while alterations in WBC counts suggested immune

response activation associated with lead toxicity,

suggesting anaemia and immune response activation

due to lead toxicity. Flora et.al., (2008) in his research

studies opined that the changes in hematological

parameters suggest lead toxicity-induced anemia and

immune response activation. Mishra and Singh (2013)

opined that Decreased hemoglobin, PCV, and RBC

counts indicate impaired erythropoiesis, possibly due to

lead's inhibition of heme synthesis enzymes. Increased

WBC counts may indicate an inflammatory response to

lead-induced oxidative stress. The result of the study

aligns with the findings of Generalova, et al., (2025) in

which Lead toxicity significantly impacts the

hematopoietic system, causing anemia by interfering

with heme synthesis and reducing erythrocyte lifespan.

The reduction in hemoglobin concentration and RBC

count observed in this study may be attributed to lead-

induced inhibition of enzymes involved in heme

biosynthesis, particularly delta-aminolevulinic acid

dehydratase (ALAD), as well as oxidative damage to

erythrocyte membranes. Increased oxidative stress may

also contribute to shortened erythrocyte lifespan and

impaired hematopoiesis.

A one-way ANOVA was conducted to examine the

effect of lead toxicity on the hematological indices of

albino rats. The results revealed that lead exposure

produced statistically significant effects on all

parameters measured Haemoglobin (F(2,4) = 49.14, p =

0.002), PCV (F(2,4) = 13.44, p = 0.017), WBC (F(2,4)

= 29.62, p = 0.004), and RBC (F(2,4) = 21.06, p =

0.008). Post hoc analysis using the Tukey HSD test

showed that for each of these indices, the Control group

differed significantly from both the Low and High lead

exposure groups (p<0.05), indicating that lead toxicity

markedly altered the hematological parameters.

It was observed that there was a statistically significant

alteration (P < 0.05) in the hematological indices of the

albino rats when compared to that of the control (Table

1). However, the effect of the different dose levels of

lead on the hematological parameters showed some

differences. The result from Weekly effect of Lead

Toxicity on Hemoglobin (g/dl) showed that there was a

significant variation in Haemoglobin level among

individual rats. This may be due to factors such as

genetics,

health

status,

environmental

factors

(temperature, stress etc), nutrition and diet. The effect

of different concentrations of lead toxicity on Packed

Cell Volume (PCV) which revealed significant

variation among individual rats. This variability may be

attributed to various factors, including genetics, health

status, environmental factors (such as temperature and

However, some previous studies have reported less

pronounced hematological alterations following low-

dose lead exposure, possibly due to shorter exposure

duration, differences in animal strain, or variations in

environmental conditions.

MISJ-IJMRAAS (January – April 2026)

Page | 19

stress), nutrition, and diet, as individual differences in

these aspects can influence hematological responses to

lead exposure (Ihedioha and Okoye 2012). Also there

was a significant variation in White Blood Cell (WBC)

levels among individual rats, which may be attributed to

factors such as genetics, health status, environmental

factors (e.g., temperature, stress), nutrition, and diet,

influencing immune responses (Adeyemi and Akanji.

2011). Moreover, it was observed that there was a

significant variation in Red Blood Cell (RBC) levels

among individual rats, with a reduction in RBC counts

observed from week 2 to week 8 in all treatment groups

compared to the control. This decrease may be

attributed to factors such as genetics, health status,

environmental factors (e.g., temperature, stress),

nutrition, and diet, which can influence erythropoiesis

and RBC survival (Ihedioha and Okoye, 2012).

Data Availability Statement:

The data supporting the findings of this study are

available from the corresponding author upon

reasonable request.

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Conflict of Interest:

The authors declare that there are no conflicts of interest

regarding this study.

Funding Statement:

This research received no specific grant from any

funding agency in the public, commercial, or not-for-

profit sectors.

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