Pesticide residues in cropland soils and shallow groundwater in Punjab Pakistan

Dimethoate residues in Pakistan and mitigation strategies through microbial degradation: a review

Organophosphate pesticides (OPs) are used extensively for crop protection worldwide due to their high water solubility and relatively low persistence in the environment compared to other pesticides, such as organochlorines. Dimethoate is a broad-spectrum insecticide that belongs to the thio-organophosphate group of OPs. It is applied to cash crops, animal farms, and houses. It has been used in Pakistan since the 1960s, either alone or in a mixture with other OPs or pyrethroids. However, the uncontrolled use of this pesticide has resulted in residual accumulation in water, soil, and tissues of plants via the food chain, causing toxic effects. This review article has compiled and analyzed data reported in the literature between 1998 and 2021 regarding dimethoate residues and their microbial bioremediation. Different microorganisms such as bacteria, fungi, and algae have shown potential for bioremediation. However, an extensive role of bacteria has been observed compared to other microorganisms. Twenty bacterial, three fungal, and one algal genus with potential for the remediation of dimethoate have been assessed. Active bacterial biodegraders belong to four classes (i) alpha-proteobacteria, (ii) gamma-proteobacteria, (iii) beta-proteobacteria, and (iv) actinobacteria and flavobacteria. Microorganisms, especially bacterial species, are a sustainable technology for dimethoate bioremediation from environmental samples. Yet, new microbial species or consortia should be explored.

Use, exposure, and environmental impacts of pesticides in Pakistan: a critical review

The excessive use of pesticides is posing major threats to humans and the environment. However, the environmental exposure and impact of pesticides in Pakistan have yet been systematically reviewed, despite the country's leading role in pesticide use. Therefore, this study identified and then reviewed 85 peer-reviewed scientific publications on the topic. It was found that, compared to the worldwide average, Pakistan had high consumptions of pesticides, with an alarming increase of 1169% in the last two decades. The quantities of pesticides used followed an order of pyrethroids > organophosphates > organochlorines > carbamates, but organochlorines were the most problematic due to their environmental occurrence, the ability to transport across the media, and identified human and ecological toxicities. Additionally, the misuse or overuse of pesticides by farmers is prevailing due to insufficient knowledge about the risks, which leads to high risks in occupational exposure. These issues are further aggravated by the illegal use or continuous impacts of banned organochlorine pesticides. For the future, we suggested the establishment of organized monitoring, assessment, and reporting program based on environmental laws to minimize contamination and exposure to pesticides in Pakistan. Remediation of the contaminated areas to mitigate the adverse environmental-cum-health impacts are recommended in the most affected regions.

Biotransformation of dimethoate into novel metabolites by bacterial isolate Pseudomonas kilonensis MB490

Bacterial strain (Pseudomonas kilonensis MB490) isolated from agricultural fields of Mianwali, was selected to check its potential to degrade Organophosphate insecticide dimethoate (DM). Strain MB490 was able to degrade dimethoate equally well at given pH range (6.0, 7.0 and 8.0), thus showing its pH independence for dimethoate degradation. Optimum temperature for dimethoate degradation varied from 25-30 °C. There was more dimethoate degradation under shaking conditions with optimum growth. Strain MB490 showed 90% dimethoate degradation in M-9 broth and 90.6% in soil slurry, while exhibited 81.5% dimethoate degradation in soil microcosm within 9 days, based on HPLC analysis of bacterial samples supplemented with 200 mg/L dimethoate. The average half-life (t _1/2) of dimethoate after bacterial degradation ranged from 1.95 days in 1st phase to 5 days in 2nd phase in M-9 broth, soil slurry and soil microcosm, while in control media without bacteria, it ranged from 30 to 64.3 days. GCMS investigation revealed the transformation of dimethoate into 5 metabolic products namely Methyl diethanol amine, Aspartylglycine ethyl ester, Phosphonothioic acid propyl-O, S-dimethyl ester, O, O, O-Trimethyl thiophosphate and omethoate which were ultimately mineralized by the strain MB490, providing energy for its growth.

Assessment of Cholinesterase inhibition activity of birds inhabiting pesticide exposed croplands and protected area in hot semi-arid region of Pakistan

Acetylcholinesterase (AChE) activity levels can be used as an indicator for AChE inhibition due to pesticide poisoning in bird species. We assessed the comparative brain cholinesterase (AChE) activity level of five bird species inhabiting pesticide exposed croplands and Protected Area i.e. Deva Vatala National Park (DVNP), Bhimber by using a spectrophotometric method. AChE activity levels ranged from 56.3 to 85.9 µmol/min/g of brain tissue of birds representing DVNP. However, AChE activity levels ranged from 27.6 to 79.9 µmol/min/g of brain tissue of birds representing croplands. AChE activity levels observed in Jungle babbler, Common babbler, and Red-vented bulbul showed significant differences (P < 0.05) at two sites. However, White wagtail and Black drongo demonstrated non-significant differences (P > 0.05). Maximum inhibition was recorded in Jungle babbler (53%) followed by Common babbler (35%), Red-vented bulbul (18%), White wagtail (15%), and Black drongo (7%). The brain cholinesterase inhibition levels under-protected ecosystems (DVNP, Bhimber) and agricultural landscape suggest insecticidal contamination and its impact on avifauna diversity. The study also emphasizes on the importance of pesticide-free zones to protect the biodiversity of birds.

Groundwater screening for 940 organic micro-pollutants in Hanoi and Ho Chi Minh City, Vietnam

Groundwater is the main source of drinking water for more than half of the residents of Hanoi (HN). It also provides about one third of the total water demand for residents of Ho Chi Minh City (HCM). However, due to rapid urbanization and frequent discharges of untreated urban wastewater to surface water, freshwater is widely contaminated by man-made chemicals, which may result in groundwater pollution. As part of an ongoing campaign to collect baseline information on the occurrence of organic micro-pollutants (OMPs) in the aquatic environment in Vietnam, 43 water samples were collected from 26 groundwater wells in HN (22) and HCM (4) in September 2013 and August 2014. Samples were analyzed by gas chromatography-mass spectrometry (GC-MS) and the resulting chromatograms were screened for 940 OMPs by an automated identification and quantification system (AIQS) within a GC-MS database. A total of 74 compounds were detected, with between 4 and 43 (median 18) compounds found at each site. Overall, contamination levels were low, with over 89 % of the detected concentrations that were less than 0.5 μg L(-1). Results suggest that most of the sampled aquifers have been impacted by non-point source pollution. Most of the contaminants detected are either currently not regulated in drinking water or are present at low levels. A health risk assessment for detected contaminants implied that there were no risks to humans. Since this study was based on a limited number of samples, especially in HCM, further, more detailed studies on the occurrence of OMPs in groundwater in HCM and a full risk assessment of detected contaminants should be prioritized.

Toxicity effects of profenofos on embryonic and larval development of Zebrafish (Danio rerio)

The aim of the present study was to evaluate the developmental toxicity of profenofos to early developing Zebrafish (Danio rerio) embryos (4h post fertilization) in a static system at 1.0 to 2.25mg/L. Median lethal concentrations (LC50) of profenofos at 24-h, 48-h, 72-h and 96-h were determined as 2.04, 1.58, 1.57 and 1.56 mg/L, respectively. The hatching of embryos were recorded at every 12h interval and the median hatching time (HT50) was also calculated for each concentration. In a separate set of experiments, 96-h LC10 (0.74 mg/L) and LC50 (1.56 mg/L) concentrations were used to assess the developmental toxicity in relation to behavior, morphology, and interactions with the targeted enzyme acetylcholinesterase. Live video-microscopy revealed that the profenofos exposed embryos exhibited an abnormal development, skeletal defects and altered heart morphology in a concentration-dependent manner, which leads to alterations in the swimming behavior of hatchlings at 144-h, which indicate that developing zebrafish are sensitive to profenofos.

Organochlorine pesticides (OCPs) in South Asian region: a review

Organochlorine pesticides (OCPs) are semi volatile organic compounds of global concern. During the last decades, their distribution, sources, transformation, toxicity and accumulation in the terrestrial and aquatic ecosystems have gained significant attention. Many of these chemicals are characterized by long range atmospheric transport potential, and their occurrence in remote areas is attributed to transport of chemicals from places where OCPs are still in use. The South Asia region is a place where primarily emissions are still taking place and thus it is important to assess the status of OCPs pollution. This document provides the historical overview and country specific environmental legislation of OCPs from the South Asian region in the context of their illegal use and storage for extended periods and still until to date. In addition, the current review discusses the existing knowledge on the levels and distribution of OCPs in different environmental compartments of South Asian region. Data on OCPs also highlights the risk assessment of these organic contaminants in the regional environment and spans the long range atmospheric transport phenomena based on Himalayas and Northern mountainous glaciers. Paradoxically in the scientific literature sources, distribution and transport of these organic pollutants in South Asian region are very limited compared to the rest of the world.

Status of organochlorine contaminants in the different environmental compartments of Pakistan: a review on occurrence and levels

This review evaluates and summarizes the results of the studies of organochlorines-contaminated water, sediment/soil and biota in Pakistan. Pattern of occurrence of each contaminant class from different study sites is followed as DDTs > Cyclodiens > HCHs > PCBs. The studies conducted in the surrounding areas of the demolished DDT manufacturing units and obsolete pesticides stores of country showed extremely highest values of ∑DDTs, which differ significantly (p < 0.05) than those reported from the agricultural areas and fresh water bodies of the country. HCHs, heptachlor, dieldrin, and HCB were also reported in many studies, but the concentrations are comparable among all the locations in the country. The authors suggested surface run-off, dumping of waste from industries and contamination from obsolete pesticides and demolished OCPs manufacturing units as the major sources in Pakistan. Information on PCBs is scares and studies on assessment of PCBs occurrence, and spatial trends in various environmental matrices needs special attention to produce the scientific publication. The results draw attention that POPs contamination must be considered as a priority environmental concern due to their use in agricultural and industrial sector.

The level and distribution of selected organochlorine pesticides in sediments from River Chenab, Pakistan

Organochlorine pesticides (OCPs), viz. β-hexachlorocyclohexane (β-HCH), γ-HCH, aldrin, dieldrin, endrin, heptachlor, endosulfan-I, endosulfan-II, heptachlor endoepoxide, heptachlor exoepoxide, mirex, dicofol, o,p'-dichlorodiphenyltrichloroethane (o,p'-DDT), p,p'-dichlorodiphenyltrichloroethane (p,p'-DDT), dichlorodiphenyldichloroethane (DDD), and dichlorodiphenyltrichloroethylene (DDE) and 12 other physicochemical parameters were measured in surface sediments from River Chenab during two sampling seasons (summer and winter, 2007) to evaluate spatial and temporal trends of sediment pollution. Hierarchical agglomerative cluster analysis identified three groups of sites based on spatial similarities in physicochemical parameters and OCP residual concentrations. Spatial discriminant function analysis (DFA) segregated 14 parameters, viz. dicofol, endosulfan-I, heptachlor endoepoxide, dieldrin, DDD, DDE, endosulfan-II, o,p'-DDT, p,p'-DDT, pH, electrical conductivity (EC), Cl⁻¹, total P (%), and silt, which explained 96% of total variance between spatial groups. γ-HCH was the most frequently detected (63%) pesticide, followed by DDD (56%). The ratio of DDTs to their metabolites indicated current input and anaerobic biodegradation. Temporal DFA highlighted aldrin, heptachlor endoepoxide, Cl⁻¹, total P, and EC as important variables which caused variations between summer and winter. DDTs were relatively more prevalent as compared to other OCPs in the sediments samples during both seasons. DDT metabolites were detected at greater frequencies and concentrations in winter, whereas DDT isomers were more prevalent in summer sediment samples. Factor analysis identified agricultural and industrial activities as major sources of sediment OCP contamination. Concentrations of γ-HCH, heptachlor endoepoxide, dieldrin, and DDTs (isomers and metabolites) in all sediment samples were well above interim sediment quality guidelines (ISQGs) and probable effect limits (PEL) given by Canadian Sediment Quality Guidelines (CSQGs).

Organochlorine residual concentrations in cattle egret from the Punjab Province, Pakistan

In this study, residual concentration of organochlorine pesticides (OCPs) in the sediments, prey, and eggs of Bubulcus ibis were measured from three breeding heronries from the Punjab province of Pakistan. Pattern of contamination in eggs followed the order: DDTs>HCHs>heptachlor>aldrin. Overall, pesticide residual concentrations were greater in eggs of cattle egrets collected from heronry on the River Ravi. Among HCHs, γ-HCH was more prevalent in eggs, whereas DDTs followed the order: DDD>DDE>p,p'-DDT>o,p'-DDT. Eggshell thinning was detected which showed negative relationship with residual concentration of DDE. In prey samples, residual concentration of POPs followed the order: DDTs>HCHs>dicofol>heptachlor; however, contamination pattern in sediments followed a slightly different order: DDTs>heptachlor>dicofol>HCHs>dieldrin>aldrin. Concentration of β-HCH was more prevalent in sediments and comparatively greater concentrations of POPs were measured in sediments collected from the River Ravi. Dicofol was found for the very first time in the biological samples from Pakistan, and its concentration was measured as relatively high in eggs from heronry from the River Chenab. Residual concentrations measured in eggs were below the levels that could affect egret populations. Biomagnification of the total OCPs through the food chain was evident in three breeding heronries. The concentration of DDE measured in eggs of the cattle egret suggests the need for monitoring this contaminant in other bird species at different trophic levels.

Isolation and characterization of a profenofos degrading bacterium

Profenofos, a well known organophosphate pesticide, has been in agricultural use over the last two decades for controlling Lepidopteron pests of cotton and tobacco crops. In this study, a bacterial strain, OW, was isolated from a long term profenofos exposed soil by an enrichment technique, and its ability to degrade profenofos was determined using gas chromatography. The isolated strain OW was identified as Pseudomonas aeruginosa according to its physiological and biochemical properties, and the analysis of its 16S rRNA gene sequence. The strain grew well at pH 5.5-7.2 with a broad temperature profile. Bioremediation of profenofos-contaminated soil was examined using soil treated with 200 microg/g profenofos, which resulted in a higher degradation rate than control soils without inoculation. In a mineral salt medium (FTW), removal in the level of profenofos of 86.81% was obtained within 48 h of incubation. The intermediates of profenofos metabolism indicated that the degradation occurred through a hydrolysis mechanism, and one of the metabolites was found to be 4 bromo-2-cholorophenol (BCP) which in turn was also mineralized by the strain. The results of this study highlighted the potentiality of P aeruginosa as a biodegrader which could be used for the bioremediation of profenofos contaminated soil.

Pesticides exposure in Pakistan: a review

This is the first systematic review of studies done since 1960, and to give an integrated picture of pesticides exposure to humans, animals, plants, waters, soils/sediments, atmosphere etc. in Pakistan. Authors have extracted data from different departments, published literature in research journals and National reports. Although the wide-spread usage of pesticides in Pakistan has controlled the pests, but like other countries, it has started causing environmental problems in the area. In some areas of Punjab and Sindh groundwater has been found contaminated and is constantly being under the process of contamination due to pesticide use. There is considerable evidence that farmers have overused and misused pesticides especially in cotton-growing areas. It is evident from the biological monitoring studies that farmers are at higher risk for acute and chronic health effects associated with pesticides due to occupational exposure. Furthermore, the intensive use of pesticides (higher sprays more than the recommended dose) in cotton areas involves a special risk for the field workers, pickers, and of an unacceptable residue concentration in cottonseed oil and cakes. The authors have also discussed the merits and demerits of different studies. The review will set the future course of action of different studies on pesticide exposure in Pakistan. Data limitations are still the major obstacle towards establishing clear environmental trends in Pakistan. The authors suggest that a reliable monitoring, assessment and reporting procedures shall be implemented in accordance with appropriate environmental policies, laws and regulations in order to minimize the pesticides exposure.

Pesticides in shallow groundwater of Bahawalnagar, Muzafargarh, D.G. Khan and Rajan Pur districts of Punjab, Pakistan

In Pakistan there is little data on environmental contamination of rural water sources by pesticides. This study evaluated pesticide contamination of groundwater in four intensive cotton growing districts. Water samples were collected from 37 rural open wells in the areas of Bahwalnagar, Muzafargarh, D.G. Khan and Rajan Pur districts of Punjab and analysed for eight pesticides which are mostly used. Information on types of pesticide used and distance to nearest pesticide mixing area and application areas was obtained for each site. From the eight pesticides analysed, six pesticides were detected in the water samples. Only cypermethrin and cabosulfan were not detected. The percentage of detection of bifenthrin, lambda-cyhalothrin, carbofuran, endosulfan, methyl parathion and monocrotophos was, respectively 13.5%, 5.4%, 59.4%, 8%, 5.4% and 35.1% in July; 16.2%, 13.55%, 43.2%, 8%, N.D. (not detected) and 24.3% in October. Maximum contamination levels (MCLs) established by the U.S. Environmental Protection Agency for drinking water were not exceeded. The study has shown the need for monitoring pesticide contamination in rural water resources, and the development of drinking water quality standards for specific pesticides in Pakistan. The conclusions and recommendations will be disseminated to senior decision makers in central and local governments, extension agents and farmers.

Organochlorine pesticides and polychlorinated biphenyls in foodstuffs from Asian and oceanic countries

Public concern about the adverse environmental and human health impacts of organochlorine contaminants led to strict regulations on their use in developed nations two decades ago. Nevertheless, DDT and several other organochlorine insecticides are still being used for agriculture and public health programs in developing countries in Asia and the South Pacific. As a consequence, humans in this region are exposed to greater dietary levels of organochlorines. In this review, published information on organochlorine concentrations in foodstuffs from South and Southeast Asia and Oceanic countries has been compiled. Foodstuffs that contribute to human exposures and dietary intakes of organochlorines were examined, and the data compared with those reported from more developed nations. Among various developing countries in Asia, considerable information on organochlorines in foodstuffs has been available from India since the late 1960s. DDT and HCH were the major insecticides in Indian foodstuffs. Concentrations of these insecticides have declined more than two orders of magnitude in farm products, such as food grains and vegetables, in two decades. Milk and milk products are the major sources of dietary exposure to DDT and HCH in India. The residues of these insecticides in dairy products were close to or above the MRLs of the FAO/WHO. Dietary intake of DDT and HCH by Indians was > 100 fold that in more developed nations. Sporadic incidences of greater concentrations (> 1 microgram/g) of aldrin, dieldrin, and heptachlor have been measured in Indian vegetables. Untreated surface waters could be a potential source of DDT and HCH exposure. In most Southeast Asian countries DDT was the common contaminant in animal origin foodstuffs. The higher percentage of p,p'-DDT in meat and fish from Southeast Asian countries, except Japan and Korea, indicated the recent use of DDt in vector control operations. Dietary intakes of DDt and HCH in Southeast Asia were an order of magnitude less than those of Indians but 5- to 10 fold greater than in more developed nations. In addition to DDT, aldrin and dieldrin were prominent in meat collected from Thailand and Malaysia. Aquatic food products from more industrialized countries, such as Japan, South Korea, Hong Kong, and Taiwan, contained significant levels of PCBs. In South Pacific countries, particularly in Australia and New Zealand, chlordanes and PCBs were the most prevalent organochlorines in foodstuffs. Food contamination by DDT, HCH, aldrin, and dieldrin was less than in developing countries in Asia but greater than in the U.S. and Japan. Intake of PCBs in Australia was greater than in the U.S. Meat and fish were the major sources of organochlorine exposure by Australians. Human dietary intake of organochlorines has been declining more slowly in developing countries in Asia. Current intakes were at least 5- to 100 fold greater than those in more developed nations, suggesting a greater risk from organochlorine exposure. Factors such as malnutrition, common among rural poor in developing nations, can increase these risks. Of greatest concern is the magnitude of exposure to organochlorines to which infants and children are subjected through human and dairy milk. The estimated intake of DDT by infants was at least 100 fold greater than the ADI of the FAO/WHO. In addition to DDT, excessive exposures to HCH and dieldrin may cause potential health effects in infants because they are more vulnerable to toxic effects. The design and implementation of appropriate epidemiological studies and their integration with monitoring of human, food, and environmental samples would be a major step in assessing the risks of organochlorine residues in foods and controlling or eliminating them. With the continued globalization of trade in food products, and the concomitant risk that food contaminated through point-source pollution may be widely distributed, identification of sources and their control should be matters of