There is an increasing global concern for adverse effects of inorganic fertilizer and pesticides applied to agricultural soils. This study investigated metal speciation in soil and health risk assessment of Jute mallow ( Corchorus olitoriuos ) from a farm settlement in Ikorodu, Lagos State. Soil samples were collected according to the set standard procedure, sequentially extracted and analyzed for selected heavy metals using standard methods. Results showed that chromium (Cr) was associated with reducible fraction (Fe-Mn) for top soil, while cadmium (Cd), manganese (Mn), and copper (Cu); lead (Pb) and nickel (Ni); and Cr were predominantly bound to carbonate, reducible and residual mineral components respectively for sub-soil. The results of Contamination Factor (CF), Contamination Degree (CD), Pollution Load Index (PLI) and Geoaccumulation Index (I geo ) showed that the soil samples were not polluted for all the investigated metals. The Cd level in the soil (13.54 ± 1.21 mg·kg﹣1) and vegetables (0.83 ± 0.05 mg·kg﹣1) were above the USEPA critical permissible limit of 3.0 mg·kg﹣1 and 0.1 - 1.2 mg·kg﹣1 respectively. The daily intake of estimated selected heavy metals from the vegetable ranged from 8.8 × 10﹣03 to 1.4 × 10﹣02 for adult and 3.8 × 10﹣03 to 1.1 × 10﹣02 for children while the Hazard Quotient (HQ) for adults ranged from 5.4 × 10﹣05 to 1.1 × 10﹣01 and that of children ranged from 8.3 × 10﹣03 to 1.4 × 10﹣02. The cancer risk (CR) values of heavy metals in the soil ranged from 1.02 × 10﹣11 to 9.90 ×
In Nigeria, the rate of increase in human population which, according to the National Population commission, stood at 88.6 million people in 2006, (and is projected to hit 160 million within the next one decade) does not enjoy a corresponding rate of increase in food supply [
Findings reveal that vegetable farmers use a wide range of pesticides at different levels to reduce losses from pests and diseases. However, despite the contribution of pesticides to agricultural production, pesticides are of major environmental concern. Many pesticides and chemicals are not biodegradable, they bioaccumulate in the food chain and detrimental to human and the ecosystem [
It is commonly acknowledged that total soil heavy-metal concentration alone is not a good measure of bioavailability and is not a very helpful tool to determine the potential risk associated with soil contamination. Therefore, chemical speciation, which plays a vital role in determining the bioavailability of toxic metal in a soil solution, is often used as a predictor of metal bioavailability to soil organisms and plants [
Heavily contaminated soils may pose long-term risks to ecosystems and human health [
Several studies recently have examined heavy-metal transfer from soil to vegetables [
This study was conducted in a farm settlement in Ikorodu, Lagos state, Nigeria. Ikorodu Farm settlement is on the designated areas for farming in Lagos State. It is located in Ikorodu, its geographical coordinates falls within 6˚40'0'' North, 3˚ 40'0'' East. The farmers in the Settlement are into several aspects of agriculture, ranging from crops farming and animal husbandry which cut across snail farming, poultry production, piggery, grass cutter farming, Vegetable farming and others. It is bounded in the North by Agbowa-Ikosi town; in the South by Isiu town, in the East by Gberigbe town, while in the West by Ode-Remo town with considerable land mass of approximately 502 square kilometres. The map of the area was shown in
Soil samples were collected randomly at 0 - 15 and 15 - 30 cm depth after land clearing, before the application of fertilizer and pesticide. The sample was collected at the uphill, hill wash and valley bottom. Two (2) weeks later after fertilizer application, pesticide application soil sample was collected at the same depth. Soil and vegetable samples were collected 4 weeks after pesticide application (
Soil pH was determined using pH meter at a ratio of 1:2.5 soil/water according to the procedure described by [
S/N | Sample | Depth/Number of Sample | ||
---|---|---|---|---|
Stages of Sample Collection | 0 - 15 | 15 - 30 | ||
1 | Soil | Immediately after land clearing | 3 | 3 |
2 | Soil | 2 weeks after fertilizer application | 3 | 3 |
3 | Soil and vegetable | 2 weeks after pesticide application | 3 | 3 |
4 | Soil and vegetable | 4 weeks after pesticide application | 3 | 3 |
outlined by [
A large number of sequential extraction methods have been reported, many of which are variant on Tessier procedure [
The sequential extractions were carried out on 1 g of soil, in 85 ml polypropylene centrifuge tube to simplify centrifuge-washing of the residue after each extraction and to minimize contamination risks and any loss of the solids through the successive extraction steps. The sample suspensions with extractant were stirred at 220 min−1 using a Rotavit shaker (Selecta). After each extraction step, the suspensions were centrifuged at 3000 min−1 (Heraeus SAPATECH centrifuge) for 30 min. The supernatants were carefully removed and stored in polyethylene bottles at 4˚C. The residues were washed with ultrapure water before the addition of the next extracting agent.
Digestion of the vegetable was carried out according to the method described by [
The concentration of Pb, Cd, Cu, Zn and Fe present in the soil extracts and vegetable digest were assayed using AAS (Buck Scientific Model 200 A) with air acetylene flame. The calibration of AAS was done using multi-elemental solution prepared by serial dilution of 20, 10, 5, 3, 2 and 1 ppm with r2 value above 0.9 before the analysis of the samples. As samples were aspirated into the flame, the heavy metals of interest present in the sample absorbed some of the light from the hollow cathode lamp reducing the intensity of the light transmitted. The computer data system of the machine converted the intensity of light into the absorbance which was directly proportional to the concentration of the heavy metals present in the sample. The metal concentration in mg/l was converted to mg/kg using the following equation:
Metal conc ⋅ ( mg / kg ) = metal conc ⋅ ( mg / l ) × dilution factor ( l ) mass of the sample ( kg ) (1)
Descriptive (Mean and Standard deviation) and inferential (ANOVA) statistics were used. Duncan was used to compare means using statistical analysis system (SAS). The data were expressed as mean ± standard deviation. The significant differences between groups were compared to find out the major biogeochemical processes controlling the distribution and partitioning of metals.
The health risk assessment model used in this study to calculate the exposure risk to children and Adults from heavy metals in soil is based on those models developed by [
For cancer risk, only the carcinogen risk for inhalation exposure modes was considered in the model, and was used in the assessment of cancer risk [
C D I i n g = C U C L × R i n g × F exp × T exp A B W × T a v g × 10 − 6 (2)
C D I I n h = C U C L × R I n h × F exp × T exp P E F × A B W × T a v g (3)
C D I d e r m a l = C U C L × S A F × A s k i n × F exp × T exp A B W × T a v g (4)
where CDI (mg∙kg−1∙day-1) is the Chemical daily intake through ingestion (CDIing), inhalation (CDIinh), dermal contact (CDIdermal) Ring is the ingestion rate at 200 mg∙day−1 for children (1–6 years) and 100 mg∙day−1 for adults [
C U C L = X + t 1 − ∝ , d f s n (5)
where X is the arithmetic mean, s is the standard deviation and n is the number of samples. In this study, quantified risk or hazard indexes for both carcinogenic and non-carcinogenic effects were applied to each exposure pathway in the analysis. The chemical daily intake (CDI) for different exposure pathways was calculated for each element and subsequently divided by the corresponding reference dose yields a hazard quotient (HQ) (non-cancer risk). For carcinogens, the chemical daily intake (CDI) was multiplied by the corresponding slope factor to produce an estimate of cancer risk. Hazard index (HI) is equal to the sum of HQ. If the value of HI (non-cancer risk) is < 1, it is believed that there is no significant risk of non-carcinogenic effects; if the value of HI > 1, there is a chance that non-carcinogenic effects may occur [
H Q = C D I i n g R f D o = C D I d e r m a l R f D o × G I A B S = C D I i n h R f D i × 100 μg / mg (6)
The methodology for the estimation of non-carcinogenic risks was provided in the USEPA Region III’s Risk-based Concentration Table[
D I R = C ( metalconc . ) × C ( factor ) × D ( vegintake ) (7)
where C(metal conc) = heavy metal concentration in vegetable (mg∙kg−1);
C(factor) = conversion factor (0.085);
D(vegetable intake) = Daily intake of vegetable (kg∙person−1∙day−1).
T H Q = E f r × E D × D I R R f D × B W × A T (8)
In order to assess the overall potential for non-carcinogenic effects from more than one heavy metal, a hazard index (HI) has been formulated based on the Guidelines for Health Risk assessment of Chemical Mixtures of US Environmental Protection Agency [
H I = ∑ T T H Q = T T H Q v e g 1 + T T H Q v e g 2 + ⋯ + T T H Q v e g n (9)
where, THQ is the target hazard quotient; EFr is the exposure frequency (365 days/year); ED is the exposure duration (70 years); C is the metal concentration in foods (mg∙kg−1∙fw); RfD is the oral reference dose (mg∙kg−1∙day−1); AT is the averaging time for non-carcinogens (365 days/year × number of exposure years). The oral reference doses were based on 1.5, 0.02, 0.04, 0.0003, 0.0005, and 0.004 mg∙kg−1∙day−1 for Cr, Ni, Cu, As, Cd, and Pb, respectively [
The descriptive statistics result of the physico-chemical properties at the study location is presented in
The result revealed that the total extractable cadmium levels in the study area were above the critical permission of 3.0 mg∙kg−1 for agricultural soil [
Sample | MC | pH | EC (µs/cm) | OC | O.M | |
---|---|---|---|---|---|---|
Land clearing | Topsoil | 6.42 ± 2.27b | 7.06 ± 0.05a | 176.2 ± 2.00b | 1.59 ± 0.06ab | 3.18 ± 0.12ab |
Subsoil | 17.53 ± 11.1a | 6.75 ± 0.26bc | 131.2 ± 28.0b | 1.16 ± 0.23bc | 2.32 ± 0.46bc | |
Fertilizer application | Topsoil | 11.48 ± 6.65ab | 7.05 ± 0.1a | 162.3 ± 6.65b | 1.30 ± 0.16bc | 2.60 ± 0.33bc |
Subsoil | 7.99 ± 3.52ab | 6.96 ± 0.096ab | 141.3 ± 25.1b | 0.99 ± 0.20c | 1.99 ± 0.41c | |
Pesticide application | Topsoil | 9.52 ± 2.72ab | 6.62 ± 0.20c | 398 ± 311a | 1.56 ± 0.27ab | 3.11 ± 0.55ab |
Subsoil | 8.95 ± 6.46ab | 6.95 ± 0.094ab | 167.8 ± 58.0b | 1.163 ± 0.36bc | 2.33 ± 0.73bc | |
Harvesting | Topsoil | 10.3 ± 1.38ab | 7.13 ± 0.18a | 163.1 ± 39.2b | 1.91 ± 0.37a | 3.82 ± 0.74a |
Subsoil | 7.58 ± 2.09ab | 6.92 ± 0.017ab | 149.6 ± 55.6b | 1.57 ± 0.255ab | 3.153 ± 0.51ab |
MC = Moisture content, EC = Electrical conductivity, OC = Organic carbon, OM = Organic matter. Values in the same column followed by the same superscript are not significantly (P < 0.05) different.
Sample | P (mg/kg ) | Na | Mg | Ca | TN | |
---|---|---|---|---|---|---|
Land clearing | Topsoil | 52.38 ± 3.00a | 1.20 ± 0.20a | 1.03 ± 0.42ab | 1.10 ± 0.2a | 0.7 ± 0.03cd |
Subsoil | 56.03 ± 6.07a | 1.07 ± 0.21ba | 1.23 ± 0.23a | 1.07 ± 0.21ba | 0.60 ± 0.07d | |
Fertilizer application | Topsoil | 53.3 ± 5.41a | 1.10 ± 0.2 ba | 1.13 ± 0.2a | 1.17 ± 0.3a | 1.03 ± 0.07bc |
Subsoil | 53.16 ± 0.57a | 1.03 ± 0.32 ab | 1.13 ± 0.45a | 0.97 ± 0.35a | 1.04 ± 0.23bc | |
Pesticide Application | Topsoil | 52.69 ± 3.53a | 0.97 ± 0.15abc | 1.07 ± 0.15a | 0.91 ± 0.03ab | 0.91 ± 0.10bcd |
Subsoil | 50.57 ± 2.37a | 1.0 ± 0.1 ab | 1.0 ± 0.26ab | 1.0 ± 0.26a | 1.18 ± 0.36b | |
Harvesting | Topsoil | 56.9 ± 4.18a | 0.70c ± 0b | 0.77±0.15ab | 0.73±0.21ab | 1.62±0.36a |
Subsoil | 56.13 ± 3.48a | 0.6 ± 0.3c | 0.47 ± 0.31b | 0.47 ± 0.21b | 1.07 ± 0.15bc |
More so, about 80% of lead was found in the non-residual fraction while high percentage of the total extractable fraction contributed to the mobile phase (exchangeable and carbonate phase) and as such implicates higher risk for lead contamination. However, total extractible Pb from all the sampling points in both study areas falls below 140 mg∙kg−1 set by USEPA for agricultural soil. Pb was found to be mostly associated with the exchangeable fraction in the top soil with percentage range of 27.6% to 44.9% (
The total extractable Chromium in the soil was below 750 mg∙Kg−1 limit permissible by [
The level of Nickel in the farmland fell within the permissible limit of 150 mg∙Kg−1 set by [
The concentrations of total extractible Cu in the farmland were all below the toxic limit of 250 mg∙kg−1 set by [
On the other hand, appreciably high amount of Cadmium found in carbonate fraction in the sub soil suggested that cadmium is potentially available to some extent in these soils because metals in this fraction are usually thought to be readily available for plants uptake. By these criteria, cadmium must be considered quite mobile and biologically available in the soil samples. The availability of this metal in the sequentially extracted fractions in the sub soil shows the order; Carbonate (33.6% to 46.2%) > Oxidizable (24.7% to 29.9%) Reducible (3.8% to 33.7%) > Residual (7.0% to 20.5%) > Exchangeable (1.22% to 1.75%) > Oxidizable (0.74% to 1.81%) (
Lead was found to be mostly associated with the reducible fraction in the sub soil with percentage range of 15.8% to 55.4% respectively (
The Chromium content was strongly associated with the residual fractions in the sub soil with percentage range of 20.8% to 39.9% respectively (
Most of the Nickel was found in the reducible fractions in the sub soil with percentage range 6.3% to 53% respectively (
However, it was inferred from the result that majority of extractable Cu in the sub soil was associated with the carbonate fraction which it’s potential mobility and bioavailability. The association of Cu with different fractions was observed to be in the order for the sub soil; Carbonate (3.89% to 50.3%) > Oxidizable (17.6% to 33.4%) > Exchangeable (5.45% to 42.8%) > Residual (11.4% to 21.9%) > Reducible (1.97% to 4.95%) (
The Cadmium concentration was noted above the recommended value of 3.0 mg∙kg−1 for agricultural soil [
The Muller Index of Geoaccumulation, Igeo indicating the level of contamination found in various soils, is widely recognized in Europe. Igeo consist of seven grading ranging from unpolluted to very seriously pollute. Grade 6 indicates a 64-fold enrichment over the background values [
The result from the study shows that the soil was not contaminated for all the metal analyzed in the soil (
In geochemical investigations, PLI is used as a resourceful tool to measure and compare soil contamination. Analyzed soil at all the sampling points displayed higher PLI values for Ni and progressive deterioration in quality (
Heavy-metal exposure has potential and serious health risk to [
Hazard Index (HI) values for analyzed elements to both adults and children decrease in the order of Mn > Cd > Cr > Ni > Pb > Cu. The HI summation for the sites using Mobile Fractions (F1 + F2 + F3 + F4) showed that Manganese poses a higher risk of non-cancer effects among the studied elements while Copper poses the lowest (
Element | Soil (ppm) | CF | CD | PLI | Classification |
---|---|---|---|---|---|
Cd | 10.3 | 0.11 | 0.21 | 0.001 | Low contamination Factor/Polluted |
Pb | 6.93 | 0.35 | 0.65 | 0.017 | Low contamination Factor/No Pollution |
Cr | 4.81 | 0.14 | 0.31 | 0.007 | Low contamination Factor/No Pollution |
Ni | 8.66 | 0.43 | 0.74 | 0.006 | Low contamination Factor/No Pollution |
Mn | 25 | 0.04 | 0.08 | 0.003 | Low contamination Factor/No Pollution |
Cu | 4.48 | 0.18 | 0.39 | 0.01 | Low contamination Factor/No Pollution |
Element | Cd | Cdcar | Pb | Pbcar | Cr | Crcar | Ni | Nicar | Mn | Cu |
---|---|---|---|---|---|---|---|---|---|---|
Type of distribution | LogN | LogN | LogN | N | LogN | LogN | ||||
95% UCL | 1.649 | 1.649 | 1.294 | 1.294 | 1.072 | 1.072 | 2.988 | 2.988 | 2.187 | 1.045 |
RfDing | 1.00E−01 | 3.50E−03 | 3.00E−03 | 1.10E−02 | 1.40E−01 | 4.00E−02 | ||||
RfDinh | 2.0E−05 | 1.00E−01 | 7.66E−05 | 5.00E−02 | ||||||
RfDdermal | 2.50E−05 | 3.50E−02 | 7.50E−05 | 4.40E−04 | 1.40E−01 | 4.00E−02 | ||||
SFinh | 5.00E−01 | 5.00E−01 | 4.20E+01 | 8.40E−01 | ||||||
Children | ||||||||||
CDIing (mg∙kg−1∙d−1) | 9.29E+07 | 7.30E+00 | 6.04E+00 | 1.68E−06 | 1.23E−06 | 5.89E−07 | ||||
CDIinh (mg∙kg−1∙d−1) | 2.60E−11 | 2.04E−11 | 1.69E−11 | 4.71E−11 | 3.44E−11 | 1.65E−11 | ||||
CDIdermal (mg∙kg−1∙d−1) | 1.45E−02 | 1.13E−02 | 9.40E−03 | 2.62E−02 | 1.92E−02 | 9.16E−03 | ||||
HQing | 9.29E+08 | 2.09E+03 | 2.01E+03 | 1.53E−04 | 8.79E−06 | 1.47E−05 | ||||
HQinh | 1.30E−05 | 1.69E−10 | 6.15E+15 | 6.88E−10 | ||||||
HQdermal | 2.32E+04 | 3.23E−01 | 9.62E+03 | 1.49E+03 | 1.37E−01 | |||||
HI = ∑HQi | 9.29E+08 | 2.09E+03 | 1.16E+04 | 1.49E+03 | 6.15E+15 | 1.47E−05 | ||||
Cancer Risk | 1.30E−11 | 1.02E−11 | 7.10E−11 | 9.90E−10 | ||||||
Adult | ||||||||||
CDIing (mg∙kg−1∙d−1) | 1.16E−06 | 9.12E−07 | 7.55E−07 | 2.11E−06 | 1.54E−06 | 7.36E−07 | ||||
CDIinh (mg∙kg−1∙d−1) | 1.71E−10 | 1.34E−10 | 1.06E−10 | 4.21E−10 | 3.08E−10 | 1.47E−10 | ||||
CDIdermal (mg∙kg−1∙d−1) | 2.68E+00 | 2.11E+00 | 1.67E+00 | 4.86E+00 | 3.56E+00 | 1.70E+00 | ||||
HQing | 1.16E−03 | 2.61E−04 | 1.01E−02 | 4.80E−03 | 1.10E−05 | 1.84E−05 | ||||
HQinh | 8.34E−08 | 1.06E−11 | 5.50E+01 | 6.16E−02 | ||||||
HQdermal | 4.28E+06 | 6.03E+01 | 1.72E+06 | 2.75E+05 | 6.35E+01 | 4.25E+01 | ||||
HI = ∑HQi | 4.28E+06 | 6.03E+01 | 1.72E+06 | 2.75E+05 | 6.36E+01 | 4.25E+01 | ||||
Cancer Risk | 8.55E−11 | 6.70E−11 | 4.45E−09 | 8.61E−09 |
The estimated daily intake of metals from the Jute Mallow and the hazard quotient and hazard index for adult and children for were presented in (
The daily intake of Cd for adult ranged between (0.023 and 0.026 mg∙day−1∙person−1) and children ranged between (0.016 and 0.018 mg∙day−1∙person−1) (
Cr is an important element for the insulin activity and DNA transcription. However, an intake below 0.02 mg per day could reduce cellular responses to insulin [
Element | Cd | Pb | Cr | Ni | Mn | Cu | HI |
---|---|---|---|---|---|---|---|
UL (mg∙day−1∙person−1) | 6.4E−02 | 2.4E−01 | 1.05E−02 | 1.0E−00 | 1.1E+01 | 1.0E+01 | |
RfDo (mg∙kg−1∙day−1) | 5.0E−04 | 4.0E−03 | 1.5E−00 | 2.0E−02 | 1.4E−02 | 4.0E−02 | |
Children | |||||||
DI | 1.6E−02 | 1.9E−02 | 1.1E−02 | 1.1E−02 | 2.4E−01 | 3.8E−02 | |
HQ | 8.1E−02 | 9.0E−02 | 3.6E−03 | 3.6E−03 | 8.3E−03 | 4.6E−03 | 2.6E+00 |
Adult | |||||||
DI | 2.4E−02 | 8.8E−03 | 1.4E−02 | 2.1E−02 | 3.5E−01 | 5.7E−02 | |
HQ | 1.1E−01 | 3.5E−02 | 5.4E−05 | 5.2E−03 | 1.3E−01 | 7.0E−03 | 2.9E−01 |
the RfD established at 1.5 mg∙kg−1 per day (equivalent to 105 mg per day) [
Ni does not have a specific function in humans; however, it is a co-factor for some microbial intestine enzymes. Ni content in the adult human body should remain below 0.1 mg per day, and excess may cause damages to DNA and cell structures [
Copper is an essential micronutrient required in the growth of both plants and animals. In humans, it helps in the production of blood haemoglobin. In plants, Cu is especially important in seed production, disease resistance, and regulation of water. Copper is indeed essential, but in high doses, it can cause anaemia, liver and kidney damage, and stomach and intestinal irritation. Copper normally occurs in drinking water from Cu pipes, as well as from additives designed to control algal growth. The daily intake of copper ranged from (0.05 - 0.2 mg∙day−1∙person−1) for adult and (0.034 - 0.13 mg∙day−1∙person−1) for children of RfD established as 0.04 mg∙kg–1 per day, equivalent to 8.0 mg per day for a 70 kg adult [
Although the HQ-based risk assessment method does not provide a quantitative estimate for the probability of an exposed population experiencing a reverse health effect, it indeed provides an indication of the risk level due to exposure to pollutants [
The sequence of HQ for adults and children followed the decrease order Cd > Mn > Pb > Ni > Cu > Cr (
Metal speciation and health risk assessment of soil and vegetable collected from Ikorodu farm settlemen of Lagos had been carried out. The results of speciation analysis showed that Pb and Ni, Cd, Mn and Cu were predominantly associated with exchangeable and residual fractions respectively, while Cr was associated with reducible fractions for top soil. Also, for sub soil; Cd, Mn and Cu, Pb and Ni, and Cr were predominantly bound to carbonate, Fe-Mn oxide and Silicate mineral components of the soil respectively. A comparison of the result of total extractible metals with standard set by USEPA reveals that Pb, Cr, Ni, Mn and Cu were below the threshold limit in the vegetable farmland while Cd level was above the critical permissible limit of 3.0 mg/kg for agricultural soil and therefore portend a health risk. The result also shows that the plant species investigated (Corchorus olitorius) accumulate all metals below the threshold limit suggested by USEPA (1986) except for Cd and Pb which exhibit higher concentration above the limit of 0.3 mg∙kg–1 and 5 mg∙kg–1. The concentration of total extractible metals in farmland was also compared to some other soil around the world, even though each area has its own geochemical characteristics. The investigation revealed Cd as the biggest contaminant and chief cause of concern. Four soil quality indices namely; contamination factors (CF), contamination degree (CD), pollution load index (PLI) and geo-accumulation index (Igeo) were further used to determine degree of anthropogenic influence on the soil quality. From the result, it can be deduced that the soil was practically not contaminated with all metals investigated in the soil except Cd which has very high contamination factor (CF), contamination degree (CD), pollution load index (PLI) and geo-accumulation index (Igeo). The health risk of heavy metal exposure to humans from the soil and vegetable was also investigated. The result reveals dermal and ingestion exposure route were the major exposure routes for adult and children respectively which can also serve as exposure route for cancer development. The Hazard index value (HI > 1) from the study shows that the soil poses non-cancer threat to human. The cancer risk Cd, Pb, Cr and Ni ranged from 1.02E−11 to 9.90E−10 and 6.70E−11 to 8.61E−09 for Children and Adult respectively.
The level of cancer risk of Cd, Pb Cr and Ni falls below the threshold values 10−4 to 10−6 which some environmental and regulatory agencies considered as unacceptable risk. ΣCR for all the metals and routes for Children (1.08E−09) and Adults (1.32E−08) were lower than the acceptable value of 10−5. The finding of this study regarding DIR, HQ and HI showed that the consumption of bush okra grown at Ikorodu farm settlement was free of risk. But the situation could however change in future depending on the dietary pattern of the consumer and the volume of contaminant added to the ecosystem. It is therefore recommended that routine monitoring of the farmland should be carried out on regular bases. Additionally, Farmer need to be educated about the dangers associated with chemical used on the farm.
The authors declare no conflicts of interest regarding the publication of this paper.
Makanjuola, O.M., Bada, B.S., Ogunbanjo, O.O., Olujimi, O.O., Akinloye, O.A. and Adeyemi, M.O. (2019) Heavy Metal Speciation and Health Risk Assessment of Soil and Jute Mallow (Corchorus Olitorus) Collected From a Farm Settlement in Ikorodu, Lagos, Nigeria. Journal of Agricultural Chemistry and Environment, 8, 201-223. https://doi.org/10.4236/jacen.2019.84016