Pesticide Residues In Selected Vegetable Collected From Wet Markets Of Bangladesh

Pesticide residues in vegetable have become a major concern associated with food safety issues. Translocation of pesticides in selected vegetable samples was determined using gas chromatography-mass spectrophotometry (GC-MS) procedures and quick, easy, cheap, effective, rugged and safe (QuEChERS) method with acetate buffering (AOAC Official Method 2007.01) was used for sample preparation. Pesticide residues above the maximum residue levels (MRLs) were found in 3 brinjal, 2 country bean and 1 tomato samples. The result revealed that country bean collected from Karwanbazar, Dhaka and Jessore sadar wet market contained 44.92 µg/kg and 38.65 µg/kg Dimethoate residue, respectively. Brinjal sample collected from Jatrabari, Dhaka, Khetlal bazar and Mithapukur bazar wet market contained 32.54 µg/kg, 25.82 µg/kg and 20.65 µg/kg Quinalphos residue respectively. Tomato sample collected from Narsingdi sadar wet market contained 8.50 µg/kg Quinalphos residue, which was lower than Maximum Residue Levels (10 µg/kg).


INTRODUCTION
Vegetable are major part of diet contributing nutrients, vitamins and minerals. Vegetable grown in Bangladesh are vulnerable to be contaminated by different pesticides. Contamination of foods with toxic chemicals poses a serious threat to public health, especially in a country like Bangladesh where due to poor health literacy and the level of awareness is very low. Pesticides have been associated with a wide spectrum of human health hazards ranging from short-term impacts such as headache and nausea to chronic impacts like cancer, reproductive harm and endocrine disruption (Chowdhury et al., 2014). Quality control and assuring safety of fruits and vegetable have become one of the major challenging issues in Bangladesh. Often consumers are dissatisfied with the poor quality product mainly due to sub-standard postharvest handling of pesticides. On the other hand, the issue of food safety has been emerged as the most serious threat in the context of nutrition security and public health of the country. There are huge concerns over the use of harmful chemicals during production and postproduction stages. The main concerns related to the presence of heavy materials, chemical residues and microbial contamination. Farmers usually apply pesticides excessively, indiscriminately and irrationally as they are not aware about the risks of pesticide residues, the guidelines on dosage and timing to use or the standardized regulations in pesticide application. This is the root of residue problems of pesticide (Zhou, 2009). The present study was carried out to determine the presence of organophosphate residues in 5 vegetable crops collected from selected areas of

Sample preparation and testing
For sample preparation, a quick, easy, cheap, effective, rugged and safe (QuEChERS) method with acetate buffering (AOAC Official Method 2007.01) was used. After homogenization with a house-hold mill, 15 gm of the homogenized sample was weighed into a 50 mL Falcon tube and 100 ml of 50 mg/ml triphenyl phosphate (TPP) surrogate standard solution in acetonitrile was added followed by 15 mL of acetonitrile containing 1% acetic acid. Then, 6 gm MgSO4 and 2.5 g sodium acetate trihydrate were added and the sample was mixed well by vortex. The sample was then centrifuged at 5000 rpm for 5 minutes. 5 mL of the supernatant were transferred in an eppendrop with 750 mg MgSO4 and 250 mg PSA. The extract was shaken using a vortex mixture and centrifuged at 10000 rpm for 5 minutes. Approximately 3 mL of the supernatant were filtered through a 0.45 mm filter and 800 mL portions were transferred to autosampler vials. The extracts were evaporated to dryness under a stream of argon and reconstituted in 800 mL acetonitrile/water (20/80, v/v) for the GC-MS analysis.

GasChromatography-Mass Spectrometry (GC-MS)
Chromatographic instrumentation and quantification were carried out by Gas chromatography-mass spectrometry (ModelGC450, Varian Inc., The Netherlands) detector equipped with split/ splitless injector with electronic pressure control. A fused silica CP-Sil 8 CB-LB/MS capillary column (30 m x 0.25 mm i.d.) was used in combination with the following oven temperature program: initial temperature 50 0 C, held for 2 minutes, 20 0 C minute -1 rpm to 160 0 C held for 2 minutes, followed by 3 0 C minute -1 to 300 0 C held for 1 minute. The carrier gas (helium, 99.999%) flow rate was set to a constant head pressure of 200 kPa at flow rate of 1 mL minute -1 . The mass spectrometer was operated in electron ionization mode with a transfer line temperature of 280 0 C, manifold temperature 40 0 C, trap temperature 200 0 C, filament number 2, ion source 230 0 C and selected ion monitoring (SIM) mode. The ion energy for electron impact (EI) was kept at 70 eV. MS Workstation version 6.9.1 was used for data acquisition. For positive identification, both retention time (Rt) and the presence of three fragment ions were considered.

Analysis of vegetable samples of Jatrabari market for pesticides residue Brinjal
Jatrabari wet market Total 30 samples of brinjal, tomato, green chili, cucumber and country bean were analyzed in the laboratory. Pesticide residues detected in 3 brinjal samples, 2 country bean samples and 1 tomato sample (figure 2). The result showed (table 2) that country bean collected from Karwanbazar, Dhaka wet market contained 44.92 µg/kg Dimethoate residue, which is higher than Maximum Residue Levels (20 µg/kg). Other samples of Karwanbazar, market did not contain any residue of pesticides. Brinjal sample collected from Jatrabari, Dhaka wet market contained 32.54 µg/kg Quinalphos residue, which is higher than Maximum Residue Levels (10 µg/kg). Other samples of Jatrabari market did not contain any residue of pesticides. Brinjal sample of Khetlal bazar, Joypurhat wet market, Joypurhat was positive to Quinalphos and the concentration was 25.82 µg/kg, which is higher than Maximum Residue Levels (10 µg/kg). Other samples of Khetlal bazar did not contain any residue of pesticides.

Analysis of vegetable samples of Jessore sadar wet market for pesticides residue
Country bean sample of Jessore sadar wet market contained 38.65 µg/kg Dimethoate, which is higher than Maximum Residue Levels (20 µg/kg). Tomato, brinjal, cucumber and green chili of Jessore sadar wet market did not contain any residue of pesticides. El-Saeid and Selim (2013) detected residues of organophosphorus, organochlorine, pyrethroid and carbamate from market vegetables (viz., beans, eggplant, cauliflower, tomato, pepper, carrot, cucumber, squash, potato, onions and okra) which showed above the MRL in 15.89% of the total tested samples. Rahman et al. (2014) found 26% vegetables (viz., brinjal, hyachinth bean, cabbage, cauliflower and red amaranth) samples from five major vegetables growing regions (Bogra, Jessore, Norsingdi, Jamalpur and Rajshahi of Bangladesh) were contaminated with dimethoate, chlorpyriphos and quinalphos residues, of which 24% of the contaminated samples contained residue above MRL. The mean concentration of carbaryl residue 0.10 mg/kg in tomato and 0.09 mg/kg found in brinjal in Al-Qassim region of Saudi Arabia (Osman et al., 2011). Tomato sample collected from Narsingdi sadar wet market contained 8.50 µg/kg Quinalphos residue, which is lower than Maximum Residue Levels (10 µg/kg). No pesticide residues detected in other samples of Narsingdi sadar wet market. Brinjal sample of Mithapukur bazar, Rangpur wet market contained 0.65 µg/kg Quinalphos residue, which is higher than Maximum Residue Levels ( Carbaryl residue was detected in tomato sample as 1.52 mg/kg. Parent pesticides may be converted to their metabolite and hence, might remain below detection limit, though some previous studies have recorded carbamate residues in different vegetables in different region of the world (Latif et. al., 2011). Several factors er application methods may contribute to the high occurrence of pesticide residues detected in the vegetable samples from the wet markets. Bangladesh normally has an unplanned control mechanism, and rampant pesticide overdosing is practiced in field level to increase crop productivity (Rahman and Alam, 2007). Moreover, the majority of farmers lack sufficient perception and knowledge about the nature of chemical pesticides and their effects on health by consuming pesticides residues. Therefore, consumers may unknowingly consume vegetables and fruits containing uncontrolled levels of pesticide residues that ultimately leads to severe health problems .
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 (Gupta 2014). Symptoms of exposure to organophosphates such as Dimethoate, Ethoprophos, Diazinion, Malathion, Quinalphos, Cypermethrin, parathion, and phosphamidon cause different types of health problems like miosis, urination, diarrhea, diaphoresis, lacrimation, excitation, and salivation (Moore 2009). Psychological and behavioral effects of organophosphorus pesticide like anxiety, depression, coma and convulsions are acute exposure, while chronic exposure of pesticide residues leads to cognitive and emotional deficits. As organophosphates act directly on the nervous system, severe organophosphate exposure is clinically manifested by marked miosis and loss of the pupillary light reflex, fasciculations, flaccid paralysis, pulmonary rales, respiratory distress, and cyanosis with less than 10% of the normal value of serum cholinesterase (Kumar et. al., 2010). Exposure to carbofuran leads to overstimulation of the nervous system due to direct inhibition of acetylcholinesterase. Symptoms of carbofuran overexposure in humans include headache, weakness, abdominal cramping, nausea, blurred vision, convulsions, tremor, and coma (Tenenbaum 2008).
Pesticide residues in food and crops are a direct result of the application of pesticides to crops growing in the field, and to a lesser extent from pesticide residues remaining in the soil (Puri, 2014). Besides, due to lack of awareness and proper knowledge of the farmers, the misuse of pesticides has become a serious problem in agricultural production (Abhilash & Singh, 2009 (Ferdousi and Rahman, 2016). In Bangladesh, the use of toxic pesticides is increasing alarmingly and it is found that pesticides use increased by 328 percent during the last 10 years, posing a serious hazards on human health due to its long-term residual effect (BARI 2010). The problem becomes severe when the indiscriminate use of pesticides by farmers is made worse due to illiteracy and low levels of awareness of the hazardous effect of pesticides to human health .

CONCLUSION
Based on the result of the analysis of selected vegetable, it can be concluded that farmers are applying pesticides excessively, indiscriminately and irrationally as they are not aware about the risks of pesticide residues, the guidelines on dosage and timing to use or the standardized regulations in pesticide application. Due to lack of awareness and proper knowledge of the farmers, the misuse of pesticides has become a serious problem in agricultural production. From the study result, it is revealed that pesticide residues in brinjal, and country bean samples were higher than Maximum Residue Levels (MRLs). Long term accumulation of pesticides residues in human body via dietary intake of vegetable and other food commodities is an alarming problem. The impact of pesticide residues can be minimized by preventive measures such as rational use of pesticides, washing and proper processing of food products, practicing organic farming, use of natural pesticides and bio-pesticides, and strict implementation and amendment of pesticide-related laws. The adoption of effective legislation for properly regulating pesticide use and increasing awareness and technical know-how in the farming community should be incorporated. The study results may upgrade the knowledge of consumers, public health experts and policy makers regarding pesticide residues in vegetable and can help for setting guidelines and monitoring pesticide residues to save human health.