A PAPER BY

OSIKEMEKHA ANTHONY ANANI AND JOHN OVIE OLOMUKORO

PRESENTED

BY

OSIKEMEKHA ANTHONY ANANI

AT THE

8TH IBCE&W (INTERNATIONAL BIOTECHNOLOGY CONFERENCE, EXHIBITION AND WORKSHOP) 2018

11-13TH MARCH, 2018.

POTENTIAL HEALTH RISK ASSESSMENT OF HEAVY METALS FROM A RIVER SEDIMENT IN SOUTHERN NIGERIA

INTRODUCTION

Sediments are an important part of the water body, located at the junction of the solid–liquid interface,

and have a significant influence on the structure and function of river ecosystems (Chen et al., 2016).

The contamination of river sediments by heavy metals has become one of the hot topics in the field of

environmental science because of their potential biological toxicity, environmental durability, and

biological severity (Reddy et al., 2004; Varol, 2011; Jiang et al., 2012; Anani and Olomukoro, 2017).

Human exposure to toxic metals have become a major health risk (Yabe et al., 2013).

The potential exposure pathways for heavy metals in contaminated sediment are calculated based on

recommendations by several American publications (US EPA, 1989).

Risk characterization predicts the potential cancerous and non-cancerous health risk of children and

adults by integrating all the information gathered to arrive at quantitative estimates of cancer risk and

hazard indices (US EPA, 2004).

RESEARCH ISSUES/PROBLEMS

Limnochemical analysis of the concentrations of heavy metals residues in water andsediments cannot provide direct indications of the impact of heavy metals on aquaticbiota, especially humans (Wegu and Omedodu, 2010).

Heavy metals found in aquatic environment and other related environment have beenreported as toxic or highly toxic to non-target species of aquatic animals whenbioacumulated (Adeyemo et al., 1994, Adeyemi et al., 2008 and Bakare et al., 2009) andcarcinogenic (IARC, 1993; Jarup, 2003; IRIS and US EPA , 2007; ATSDR, 2007; Samiand Saad, 2015).

There is the need for more data on the non-carcinogenic and carcinogenic risk onconcentrations of a wider range of heavy metals in our various aquatic bodies.

Furthermore, there no information on the probable human health risks of heavy metalsin adults (male and female) and children exposed to river sediment via oral and dermalexposure pathways in this region.

JUSTIFICATION FOR THE STUDY

The justifications for this study were based on:

The need to incorporate and select sites that serve and reflect progression ofpollution, ecological particularity and drainage for catchments of intensiveagricultural and other anthropogenic use.

The need to fully assess the human health risks of heavy metals and tosafeguard the health of the ecosystem and the community at large.

AIM AND OBJECTIVES

AIM:

This study aimed at assessing the potential health risk of heavy metals from a river

sediment in southern Nigeria.

OBJECTIVES: The specific objectives of this study were to:

assess the levels of heavy metals in Ossiomo River sediment

evaluate the probable health risks posed by the contaminated sediment on adults (male

and female) and children via two pathways (oral and dermal) through quantifications

MATERIALS

AND

METHODS

This study was conducted at about 5.1 km stretch of the Ossiomo River (Ologbo axis), Benin City situated in the

South West of Nigeria, in the following geographical locations; Latitude 6° 03’.1’’ N - Longitude 5° 40’.3’’ E (Fig. 1).

Four sampling stations in the river were selected to reflect the upstream and the downstream status of the river based

on the possible amount of agricultural and other anthropogenic pollution it received with the following ecological

factors and geographical locations (Plates 1 - 4):

STUDY AREA

Description of study area

Fig. :1 Map of study area showing designated sampling stations

Plate 1: Station 1: This is a reference zone free from agricultural and anthropogenic activities. This

station is located at Latitude 6° 02’.890’’ N and Longitude 5° 39’.599’’ E.

Plate 2: Station 2: This station is located closed to a timber factory and closed to a deck of boats and where human

activities were very high with crude oil exploration and processing by NNPC-IDSL (Nigeria National Petroleum

Company-Integrated Data Service Limited). It lies at Latitude 6° 01’.759’’ N and Longitude 5° 38’.344’’ E.

Plate 3: Station 3: This is located closed to local gin distillers, palm oil farm (PRESCO), cassava farm and sawmills of

Latitude 6° 01’.859’’ N and Longitude 5° 36’.870’’ E.

Plate 4: Station 4: This is located closed to a large cassava (garri) processing industry and a Palm tree farm which

lies at Latitude 6° 01’.091’’ N and Longitude 5° 35’.199’’ E.

Sampling Collection

A total of 72 samples was collected and analysed monthly from March 2015 – August 2016. The

sediment samples were collected with an Eckman grab in accordance with standard procedures as

described by APHA, (2005). All the samples were collected from a depth of about 150 cm in

triplicate and pulled together as a composite sample in a quality black polyethylene bags.

Plate 1: A photography of an Eckman grab- Photo credits by Anani 2015

Sample Techniques/Extraction

The samples were air-dried at room temperature, and were further dried in an oven at atemperature of 105° C and then were crumpled to a fine texture in a ceramic mortar, andthereafter sieved mechanically using a 0.5 mm mesh sieve.

The heavy metals, namely iron, manganese, zinc, copper, chromium, cadmium, lead, nickel,and vanadium, were analyzed according to methods adopted from APHA, (1998); Radojevicand Bashkin, (1999) using an Atomic absorption spectrophotometer (Solaar 969 UnicamSeries model).

Data Analysis

Inter-station comparisons were carried out to test for significant differences in the

physicochemical conditions using parametric analysis of variance (ANOVA) to locate

site(s) of significant difference and Univariate analysis. PAST 3.0 and Microsoft excel 2013

version were used as the statistical software tools for the data computation.

Quantifications of the Human Risk Assessment

HQ (Hazard Quotient) = CDI / RfD

methods by IRIS and US EPA, (2007) ATSDR, (2007). {Where: CDI =Chronic Daily Intake;RfD= Reference Dose}.

CDI (Chronic Daily Intake) = (Cs × IRsoil × EF × ED) / (BW × AT) for ingestion exposureand

CDI (Chronic Daily Intake) = (Cs × DPsoil × EF × ED) / (BW × AT) for dermal exposure

methods by IRIS and US EPA, (2007) ATSDR, (2007) and Zabin et al., (2008).

Table 1: Default values used for calculations (ingestion and dermal pathways)

VariableAdults

ChildrenMale Female

IRsoil (0.1 gm/d) 0.1gm/d) (0.2 g/d)

EF 350 350 350

ED 30 30 6

BW 70 65 15

AT 10950 10950 2190

DP (dermal permeability coefficient of sediment with water)) in kg. day-1

Fe NS

Mn 0.04

Zn 0.0054

Cu 0.012

Cr 0.0075

Cd 0.00001

Pb NS

Ni 0.0056

NB: NS means not specified {Where: Cs = Concentration of metal in sediment (mg. Kg-1); IRsoil =

Ingestion or oral rate of sediment (Kg.day-1); DPsoil = Dermal permeability coefficient rate of sediment

with water (Kg.day-1); EF = Exposure frequency (days year-1); ED= Exposure duration (years); BW =

Body weight (kg); AT = Average time (days)}.

Human Risk Assessment contd.

HI (Hazard Index) = HQ1 +HQ2 +HQ3...+ HQn

Methods by (Paustenbach, 2002). Where HQ1 is Hazard Quotient of the first heavy metal….

CR (Carcinogenic risk) = CDI × SF

Methods by US EPA; (1989), Vieira et al., (2011), Yu et al., (2010). Where CDI is the chronicdaily intake or dose (mg/kg/day) and SF is the slope factor, expressed in (mg/kg/day).

TCR (Total cancer risk) = 𝒌=𝟏𝒏 𝑪𝑫𝑰𝒌 × 𝑺𝑭𝒌

Methods by Gržetić and Ghariani, (2008). Where Where CDIk is the chronic daily intake ordose (mg/kg/day) for substance k, SFk is the slope factor, expressed in (mg/kg/day), forsubstance k and CDIk × SFk is the risk estimate for the kth substance.

RESULTS,

DISCUSSIONS

AND

FINDINGS

RESUTS OF THE HEAVY METAL QUANTIFICATION

Table 2: Total concentration (mg/kg) of heavy metals in the sediments of Ossiomo River

Stations/Metals Fe Mn Zn Cu Cr Cd Pb Ni V CI

Station 1

156.49 13.33 28.38 4.52 1.99 1.8 1.41 1.08 0.98

23.33

Station 2

329.14 24.5 43.63 10.73 4.89 5.89 6.36 2.65 2.23

47.78

Station 3

284 20.92 39.17 9.84 3.98 5.26 4.86 2.3 1.97

41.37

Station 4

226.8 19.08 34.92 7.2 3.03 3.25 3.1 1.89 1.7

33.44

Mean 249.11 19.46 36.53 8.07 3.47 4.05 3.93 1.98 1.72

Standard deviation 74.61 4.66 6.49 2.80 1.25 1.88 2.15 0.68 0.54

Minimum 156.49 13.33 28.38 4.52 1.99 1.80 1.41 1.08 0.98

Maximum 329.14 24.50 43.63 10.73 4.89 5.89 6.36 2.65 2.23

Median 255.40 20.00 37.05 8.52 3.51 4.26 3.98 2.10 1.84

Geometric mean 240.00 19.00 36.08 7.66 3.29 3.67 3.41 1.88 1.64

WHO/FEPA 2003 Limits 0.03 0.03 0.0123 0.3 - 0.04 0.06 - -

P-Values P<0.05 P<0.05 P>0.05 P<0.05 P<0.05 P<0.05 P<0.05 P<0.05 P<0.05

NB: CI: Cumulative Impact

RESUTS OF THE NON-CARCINOGENIC QUANTIFICATION

Table 3: Probable non-carcinogenic risk of heavy metals in Ossiomo sediment on male

Potential exposure of heavy metals

Heavy Metals Cs CDI Rfd dermal Rfd oral HQ dermal HQ oral

Fe 249.11 0.34 NS NS NS NS

Mn 19.46 0.03 0.04 0.046 0.01 0.58

Zn 36.53 0.05 0.01 0.02 0.06 2.50

Cu 8.07 0.01 0.01 0.04 0.01 0.28

Cr 3.48 0.00 0.01 0.001 0.01 4.76

Cd 4.05 0.01 0.00 0.001 5.55 5.55

Pb 3.93 0.01 NS 0.3 0.00 0.02

Ni 1.98 0.00 0.01 0.14 0.00 0.02

V 1.72 0.00 NS NS NS NS

HI 5.63 13.70

RESUTS OF THE NON-CARCINOGENIC QUANTIFICATION CONTD.

Table 4: Probable non-carcinogenic risk of heavy metals in Ossiomo sediment on female

Potential exposure of heavy metals

Heavy Metals Cs CDI Rfd dermal Rfd oral HQ dermal HQ oral

Fe 249.11 0.37 NS NS NS NS

Mn 19.46 0.03 0.04 0.05 0.01 0.62

Zn 36.53 0.05 0.01 0.02 0.06 2.69

Cu 8.07 0.01 0.01 0.04 0.01 0.30

Cr 3.48 0.01 0.01 0.00 0.01 5.13

Cd 4.05 0.01 0.00 0.00 5.97 5.97

Pb 3.93 0.01 NS 0.30 0.00 0.02

Ni 1.98 0.00 0.01 0.14 0.00 0.02

V 1.72 0.00 NS NS NS NS

HI 6.06 14.76

RESUTS OF THE NON-CARCINOGENIC QUANTIFICATION CONTD.

Table 5: Probable non-carcinogenic risk of heavy metals in Ossiomo sediment on children

Potential exposure of heavy metals

Heavy Metals Cs CDI Rfd dermal Rfd oral HQ dermal HQ oral

Fe 249.11 3.18 NS NS NS NS

Mn 19.46 0.25 0.04 0.05 0.03 5.41

Zn 36.53 0.47 0.01 0.02 0.26 23.35

Cu 8.07 0.10 0.01 0.04 0.04 2.58

Cr 3.48 0.04 0.01 0.00 0.06 44.43

Cd 4.05 0.05 0.00 0.00 25.88 51.76

Pb 3.93 0.05 NS 0.30 0.00 0.17

Ni 1.98 0.03 0.01 0.14 0.00 0.18

V 1.72 0.02 NS NS NS NS

HI 26.27 127.88

FINDINGS FROM THE NON-CARCINOGENIC RISK QUANTIFICATION

The CDI values obtained for this study were generally lower than1(CDI < 1) for the adults (male and female) in all the heavy metalsexempting that of the children.

In the quantification of the exposure factor in the male, female andchildren, it was observed that the HQ of the dermal exposure wasonly Cd; 5.55, 5.97 and 25.88 respectively.

However, the HI values of this study was observed to be greaterthan the set unity standard; an indicative of a non-carcinogenicpotential risk to the adults and children exposed to the cumulativerisk of the heavy metals.

FINDINGS FROM THE NON-CARCINOGENIC RISK QUANTIFICATION CONTD.

Cd showed a high potential hazard risk with values greater than theUS EPA, (1989 and 2004) unity limits. This an indication of a non-carcinogenic potential risk to the adults and children exposed to theheavy metal.

It was also observed that the rank of the potential impacts in theindividual was; Children > Females > Males.

The results of this study showed that the measured sedimentconcentrations of most of the studied elements created significantcarcinogenic lifetime risk from ingestion and dermal exposure to thesediment.

RESUTS OF THE CARCINOGENIC RISK QUANTIFICATION

Table 6: Probable carcinogenic risk of heavy metals in Ossiomo sediment exposed to adults (male and female) and children

Heavy metals SF CR male CR female CR children TCR

Cd 6.10E+03 3.38E+01 3.64E+01 3.16E+02 3.86E+02

Cr 5.00E+02 2.38E+00 2.56E+00 2.22E+01 2.72E+01

Pb 8.50E+00 4.58E-02 4.93E-02 4.27E-01 5.22E-01

RESULTS OF THE CARCINOGENIC RISK QUANTIFICATION

Mean

Standard deviation

Standard errorKEYS

Fig. 2.1: Box plot of the carcinogenic risk factor of heavy metals in Adults (male and female) and children exposed to Ossiomo sediment

PROBABLE CARCINOGENIC AND TOTAL CARCINOGENIC RISK QUANTIFICATION IN ADULTS AND CHILDREN

Fig. 2.2: The carcinogenic and total carcinogenic risk factor of heavy metals in Adults (male and female) and children exposed to Ossiomosediment

33.83 36.43

315.73

385.99

2.38 2.56

22.22 27.16

0.05 0.05 0.43 0.52

0.00

50.00

100.00

150.00

200.00

250.00

300.00

350.00

400.00

450.00

CR male CR female CR children TCR

He

avy

me

tal v

aria

bili

ty

Carcinogenic risk factors

Cd Cr Pb

FINDINGS FROM THE CARCINOGENIC AND TOTAL CARCINOGENIC RISK QUANTIFICATIONS

Cd was found to be the highest contributor to the cancer risk andfar above the stated regulatory standards.

For the quantification of the TCR, the values gotten aftercomputation were; Cd (3.86E+02), Cr (2.72E+01) and Pb (5.22E-0.1).These values are not considered acceptable for Cd and Cr accordingto literatures (Wu et al., 2015 and Guney et al., 2010), and alsohigher than the carcinogenic target risk of 1. 0 × 10−6 (USEPA, 2011).

It is obvious that both the ingestion and dermal exposure of theheavy metals are significant pathways for non-carcinogenic andcarcinogenic risks which are similar to other studies on heavymetals risk of soil (Islam et al., 2017 and Hu et al., 2017).

CONCLUSION

This study has proven that sediment contamination in Ossiomo Riveris important in the environmental point of view and should beconsider a major risk to human health as well to the ecosystem.

Risk assessment calculated for a lifetime exposure, indicated that thecarcinogenic risk is completely significant, but the non-carcinogenicrisk tends to become significant mainly for children which may likelyhave the highest impact, since it approaches values which could beunacceptable. Children activities such as playing, swimming, drinkingof contaminated sediment might be the major health risk routes.

There were particularly dangerous heavy metals; Cd and Cr, and theircumulative effects expressed in the children. Ingestion and dermalhazardous indices should be considered highly significant because theresults gotten from this study are highly alarming.

CONTRIBUTION TO KNOWLEDGE

This study has contributed to knowledge in the following ways:

by adding information to the data base of scientific research bodies.Been the first documented from this part of the world, the researchdata base will serve as a benchmark for subsequent researches.

the importance of screening the sediment along sides the water inorder to ascertain the attendants potential human risks and toquantify non-carcinogenic and carcinogenic impacts is needed.

the wake-up call of the ‘’boiling frog syndrome of the 21st century.’’By re-echoing the need of the drive of re-enforcement andcompliance by regulatory bodies to curtail pollution of thewatercourse.

RECOMMENDATIONS

Further studies should be carried out in other to monitor the long

term anthropogenic impacts on the river and proffer substantive

management and remediation to the pollution cause in order to

anticipate any possible human health risk impacts.

Hence, stringent environmental laws should be reinforced and

compliance should be adhered to in order to protect humans from

consuming surface water with sediment contaminants.

THANK YOU

FOR YOUR

ATTENTION