Residual levels of seven frequently used pesticides were investigated in 140 samples of two common vegetables, eggplants and tomatoes, from agricultural fields in the Narayanganj district of Bangladesh. The analysis of pesticide residues was performed by high-performance liquid chromatography with photodiode array detection. A large percentage of the eggplants (50%) and tomatoes (60%) from the Narayanganj district were contaminated with pesticides, and all of the levels were above the
The contamination of food by chemicals is a public health concern worldwide, and pesticides are a chemical hazard associated with food contamination [
Pesticide exposure is increasing in Bangladesh due to the acreage of irrigated agriculture. Approximately 80 types of registered pesticides with 170 different trade names are commonly used in agriculture and public health sectors in Bangladesh [
Several studies have demonstrated that vegetables sprayed with pesticides will absorb them internally, which can create adverse effects [
The vegetables were collected between June 2011 and December and March 2011 from the agricultural fields of three districts from Narayanganj (Rupgonj, Sonargaon, and Arihajar Upazilas), which are industrial areas located close to Dhaka City. Ten samples each of eggplants and tomatoes were collected directly from selected fields in the sampling area. The samples were placed in sterile polyethylene bags and transported to the laboratory on ice. They were stored at 4°C until analysis (within 24 hours).
Each vegetable sample (10 g) was homogenized with an Ultra-Turrax macerator (IKA-Labortechnik, Janke & Kunkel GMBH & CO.KG, Germany) at high speed for 3 min using a 40 mL solvent mixture that consisted of double-distilled hexane : acetone (3 : 1) at room temperature. Anhydrous sodium sulfate (20.0 g) was added to remove any remaining moisture. The samples were then centrifuged for 5 min at 3000 rpm, and the supernatant was transferred to a clean, graduated cylinder for volume measurement. The organic extract was concentrated to 5 mL on a vacuum rotary evaporator (Buchi, Switzerland) using a water bath at 45°C and 3.63 psi. The extract was cleaned up in a heat-activated (150°C for 4 h) charcoal-silica gel-alumina (0.1 : 5.0 : 5.0) column followed by elution with a solvent mixture of dichloromethane (2%) in double-distilled hexane. The elute was concentrated to 1 mL in a rotary evaporator, followed by evaporation to dryness under a gentle nitrogen stream. The dried sample was reconstituted in acetonitrile (1 mL) prior to injection into high-performance liquid chromatography (HPLC).
Analysis was conducted by a HPLC (Shimadzu, Japan) LC-10ADvp, equipped with an SPD-M 10 Avp attached to a photodiode array detector (Shimadzu SPD-M 10 Avp, 200–800 nm). A C18 Reverse Phase Alltech (250 × 4.6 mm, 5
For preparation of the calibration curve, equal volumes of several different concentrations of standard solutions were injected into the HPLC machine. Quantification was performed according to the calibration method described by Bhattacharjee et al. [
The validation of the analytical method was performed according to the European Commission (EC) guidelines in terms of the accuracy, precision, and limit of quantification (LOQ) [
The precision was estimated by monitoring the repeated (
The average percentage recoveries ranged from 80.33% to 99.00% while precision ranged from 3.14% to 13.25%. In the present study, the LOQ was lower than reporting limit and MRL and ranged from 0.0036 to 0.0045 mg/kg for tomato and 0.0030 to 0.0037 for eggplant.
The health risk indices associated with pesticide residues were estimated from food consumption
Large percentages of the eggplants (50%) and tomatoes (60%) were contaminated with pesticides (Table
Residual levels of carbofuran, diazinon, dimethoate, fenitrothion, linuron, parathion, and phosphamidon in eggplant and tomato samples.
Sample | Concentration (mg/kg) | ||||||
---|---|---|---|---|---|---|---|
Carbofuran | Diazinon | Dimethoate | Fenitrothion | Linuron | Parathion | Phosphamidon | |
Standard | 5 | 25 | 5 | 5 | 25 | 5 | 5 |
MRL | 0.020 | 0.010 | 0.020 | 0.010 | 0.050 | 0.050 | 0.010 |
B-1 | BDL | 0.453 ± 0.033 | BDL | BDL | BDL | BDL | BDL |
B-2 | BDL | BDL | BDL | BDL | BDL | BDL | BDL |
B-3 | BDL | BDL | BDL | BDL | BDL | BDL | BDL |
B-4 | BDL | 4.514 ± 0.397 | BDL | BDL | 1.073 ± 0.054 | BDL | 1.416 ± 0.141 |
B-5 | BDL | BDL | BDL | BDL | 0.657 ± 0.059 | BDL | BDL |
B-6 | BDL | BDL | BDL | BDL | BDL | BDL | BDL |
B-7 | BDL | BDL | BDL | BDL | BDL | BDL | BDL |
B-8 | BDL | BDL | BDL | BDL | BDL | BDL | BDL |
B-9 | BDL | BDL | 1.806 ± 0.148 | BDL | BDL | BDL | BDL |
B-10 | BDL | BDL | BDL | 0.674 ± 0.038 | BDL | BDL | BDL |
T-1 | BDL | 1.888 ± 0.204 | BDL | BDL | BDL | 0.116 ± 0.003 | BDL |
T-2 | BDL | 2.611 ± 0.111 | BDL | BDL | BDL | BDL | BDL |
T-3 | BDL | ND | BDL | BDL | BDL | BDL | BDL |
T-4 | 0.673 ± 0.032 | 3.451 ± 0.417 | BDL | BDL | BDL | BDL | BDL |
T-5 | BDL | BDL | BDL | 0.657 ± 0.059 | BDL | BDL | BDL |
T-6 | BDL | BDL | BDL | BDL | BDL | BDL | BDL |
T-7 | BDL | BDL | BDL | BDL | BDL | BDL | BDL |
T-8 | BDL | 3.612 ± 0.169 | BDL | BDL | 0.540 ± 0.020 | BDL | 0.693 ± 0.062 |
T-9 | BDL | BDL | BDL | 1.888 ± 0.204 | BDL | BDL | BDL |
T-10 | BDL | BDL | BDL | BDL | BDL | BDL | BDL |
The results are expressed as the mean ± SD (standard deviation) of triplicates measurements. Here, B = eggplant; T = tomato; BDL = below the detection limit (0.001 ppm); MRL = maximum residual limit determined by EC regulation 396/2005 (from EU pesticide database) [
The HRI in the eggplant samples was highest for diazinon eggplant, followed by dimethoate, phosphamidon, and fenitrothion (Table
Percentage contamination and HRI of the investigated pesticides for eggplant.
Pesticide | Contamination rate (%) | MRL (mg/kg) | ADI (mg/kg/day) | EDI (mg/kg/day) | HRI | Health risk |
---|---|---|---|---|---|---|
Carbofuran | 0 | 0.02 | 0.003 | — | — | — |
Diazinon | 20 | 0.01 | 0.001 | 0.0143 | 14.3 | Yes |
Dimethoate | 10 | 0.02 | 0.001 | 0.0104 | 10.4 | Yes |
Fenitrothion | 10 | 0.01 | 0.002 | 0.0039 | 1.9 | Yes |
Linuron | 20 | 0.05 | 0.010 | 0.0050 | 0.5 | No |
Parathion | 0 | 0.05 | 0.005 | — | — | — |
Phosphamidon | 10 | 0.01 | 0.001 | 0.0081 | 8.1 | Yes |
MRL = maximum residual limit; HRI = human risk index; ADI = acceptable dietary intake; EDI = estimated dietary intake. The HRI was calculated by considering an average daily vegetable intake for a 60 kg adult as 0.345 kg/person/day [
The HRI in the tomato samples was also highest for diazinon (Table
Percentage contamination and HRIs of the investigated pesticides for tomato.
Pesticide | Contamination rate (%) | MRL (mg/kg) | ADI (mg/kg/day) | EDI (mg/kg/day) | HRI | Health risk |
---|---|---|---|---|---|---|
Carbofuran | 10 | 0.02 | 0.003 | 0.0039 | 1.3 | Yes |
Diazinon | 40 | 0.01 | 0.001 | 0.0166 | 16.6 | Yes |
Dimethoate | 0 | 0.02 | 0.001 | — | — | — |
Fenitrothion | 20 | 0.01 | 0.002 | 0.0073 | 0.7 | No |
Linuron | 10 | 0.05 | 0.010 | 0.0031 | 0.3 | No |
Parathion | 10 | 0.05 | 0.005 | — | — | — |
Phosphamidon | 10 | 0.01 | 0.001 | 0.0040 | 4.0 | Yes |
MRL= maximum residual limit; HRI = human risk index; ADI = acceptable dietary intake; EDI = estimated dietary intake. The HRI was calculated by considering an average daily vegetable intake for an adult (60 kg) as 0.345 kg/person/day [
Approximately 23.53% of the contaminated samples contained multiple residues. Overall, only fenitrothion contamination in both eggplants and tomatoes caused no health risk, as indicated by the HRI.
We investigated the pesticide residue contamination levels of five organophosphates (diazinon, dimethoate, fenitrothion, parathion, and phosphamidon), one carbamate (carbofuran), and one phenyl urea herbicide (linuron) in two common vegetables, eggplants and tomatoes, from agricultural fields in the Narayanganj district of Bangladesh. Large percentages of the eggplants (50%) and tomatoes (60%) were contaminated with pesticides at levels exceeding the maximum residual limit (MRL) set by the EC regulation.
None of the eggplant samples were contaminated with carbofuran. However, carbofuran was detected in a single tomato sample at a level 33 times above the MRL. The carbofuran level of market vegetables in Pakistan, including eggplants and tomatoes, has been recorded as 0.00–0.39 mg/kg, 0.0–19.5 times higher than the MRL [
Diazinon was the most common (35%) pesticide detected in the vegetable samples (Figure
Typical chromatogram of a dimethoate standard (5 mg/kg) (retention time = 3.4 min).
Chromatogram of VS-9 showing the presence of dimethoate (RT: 3.301 min).
Dimethoate was detected in only a single eggplant sample at 1.806 mg/kg but was not found in the tomato samples. The detected level was 90 times higher than the MRL established by the European Union [
Fenitrothion and linuron are the next two most common types of pesticides detected in the vegetable samples after diazinon. The highest fenitrothion level (1.88 mg/kg) was detected in a tomato sample, which was approximately 188 times higher than the MRL. The highest linuron level in an eggplant sample (1.07 mg/kg) was approximately 21 times higher than the MRL. In India, the fenitrothion residual level for both tomato and eggplant was reported to exceed the MRL by 33 times [
Parathion was detected in only a single vegetable sample (tomato) at 0.116 mg/kg, approximately 2.3 times higher than the MRL. A similar multiclass pesticide residue analysis showed that parathion levels in market eggplants and tomatoes in Bangladesh exceeded the MRL by 0–6.4 and 0–4.6 times, respectively [
Phosphamidon was detected in a single sample for each of eggplant and tomato, with the highest level in an eggplant sample at 1.146 mg/kg. This level is approximately 140 times higher than the MRL, which is alarming. In several field vegetables in India, the residual phosphamidon level exceeded the MRL (0.51 mg/kg) by 51.0 times [
Several factors may contribute to the high occurrence of pesticide residues detected in the vegetable samples from the Narayanganj district. Bangladesh frequently has a weak control mechanism, and rampant pesticide overdosing is practiced to increase crop productivity [
Fortunately, the soil degradation times of some pesticides, such as fenitrothion (4 days) and dimethoate (7 days), are relatively short, and it is possible that both pesticide levels would have dramatically decreased by the time the vegetable was consumed by the general public. This fact could also contribute to the relatively lower pesticide levels of these two types of pesticides seen in the analyzed samples. The differences in the soil half-life indicate that the natural decontamination of a pesticide also depends on its physiochemical properties. This may also explain the highest contamination seen with diazinon, which could actually be due to its relatively longer soil degradation time (40 days) and low water solubility (60 mg/L) (Table
Physiochemical properties of the investigated pesticides [
Name | Molecular formula | Molecular weight | Soil half-life (days) | Water solubility (mg/L) |
---|---|---|---|---|
Carbofuran | C12H15NO3 | 221.30 | 50 | 351 |
Diazinon | C12H21N2O3PS | 304.35 | 40 | 60 |
Dimethoate | C5H12NO3PS2 | 229.26 | 7 | 39,800 |
Fenitrothion | C9H12NO5PS | 277.24 | 4 | 30 |
Linuron | C9H10Cl2N2O2 | 249.10 | 60 | 75 |
Parathion | C10H14NO5PS | 291.26 | 14 | 24 |
Phosphamidon | C5H12NO3PS2 | 229.26 | 17 | 1,000,000 |
The HRI is the ratio of the estimated dietary intake (EDI) to the accepted daily intake (ADI) and indicates whether the calculated amount of the pesticide residue exceeds the amount of the pesticide that can be consumed every day for a lifetime. Thus, an HRI value greater than 1 indicates that the estimated dietary intake exceeds the ADI and is considered unsafe for human health [
Not only were the levels very high, but some of the vegetable samples also contained multiresidues of different types of pesticides. Exposure to pesticides through contaminated food leads to a spectrum of adverse health effects that depend on the nature of the pesticide and on the amount and duration of exposure [
This is a small pilot study that successfully pasteurized the residual pesticide levels of seven commonly used pesticides in two field vegetables before they were transported to market. The actual levels of exposure to consumers may thus be different after they reach their homes and following proper washing. More comprehensive studies should be undertaken to determine the levels of different pesticide residues on other vegetables and fruits originating from different regions in Bangladesh and at several different sampling intervals. Regular monitoring of the use of common pesticides on vegetables should also be undertaken as this study indicated the presence of high residual pesticide levels that may pose a health hazard. The adoption of effective legislation for properly regulating pesticide use and increasing awareness and technical know-how in the farming community should be incorporated in Bangladesh.
Large percentages of the eggplants (50%) and tomatoes (60%) from the Narayanganj district were contaminated with pesticides, and all of the levels were above the MRL proposed by the EC regulation. Diazinon was the most common (35%) pesticide detected in the vegetable samples. The HRI for diazinon was the highest for both eggplant and tomato samples, which may be due to its physiochemical property. Fenitrothion and linuron are the two second most common types of pesticides detected in the vegetable samples. Regular monitoring of the use of common pesticides on vegetables should be undertaken.
The authors declare that there is no conflict of interests regarding the publication of this paper.
This study was financially supported by Universiti Sains Malaysia RU Grants (1001/PPSP/815073).