Pesticide Risk Indicators Research Articles

Pesticides, crop choices and changes in well-being

This study investigates how Pesticide Risk Indicators (PRIs) can be applied to help develop sound economic policies. We modified one of the numerous PRIs proposed over the years, the Environmental Impact Quotient (EIQ), originally developed for the fruit industry, to consider co-formulants and adjuvants. The new formula includes three components representing the externalities of farm worker risk, consumer risk, and ecological risk. It also considers the potential externalities of the use of pesticides on residents living near the farms where these products are used. We applied the modified EIQ to two areas located in central Italy (the Chiana Valley in Tuscany and the Tiber and Upper Tiber Valleys in Tuscany/Umbria), surveying a sample of farms to determine the quantity and types of pesticides used on five crops: durum wheat, soft wheat, corn, tobacco, and olives. After calculating the impact quotient, we used data from a survey conducted in a different Italian region regarding the willingness to pay (WTP) for a pesticide-free environment and determined the WTP for even minimal changes in that quotient. Using those results, we simulated the changes in welfare (calculated as changes in willingness to pay) that would result from modifying the amount of land used for each crop. Our findings indicate that the proposed WTP indicator may have broad utility and that its application may lead to enhanced awareness of the consequences of pesticide use in farming.

Reducing Pesticide Risk Associated With Dollar Spot Management on Golf Course Turfgrass

Pesticides are critical tools for golf course managers to maintain healthy and economically profitable golf course playing surfaces. However, the intensity and types of pesticides used on golf courses can be harmful to human and environmental health. Two separate studies were conducted at two locations in Wisconsin, USA between 2014 and 2020 to test the ability of reduced risk fungicide programs to control dollar spot (Clarireedia spp.) on golf course fairways and putting greens. Risk of the pesticide application programs was quantified in both studies using the active ingredient application rate, the Environmental Impact Quotient (EIQ), hazard quotient (HQ), and the Pesticide Risk Tool (PRT). The first study found that using the Smith-Kerns Dollar Spot Prediction Model to schedule fungicide applications did not reduce pesticide risk on its own, but that a pesticide program utilizing reduced risk products was just as effective in controlling dollar spot as a conventional program while reducing pesticide risk by ~50–80% depending on the pesticide risk indicator used. The second study established an average pesticide risk using HQ based on the pesticide records of 23 randomly selected Wisconsin golf courses. This statewide average was then used to test pesticide programs at 100, 75, 50, and 25% of the average risk for their efficacy in controlling dollar spot over a 4-year period. In the 4 years of the study, dollar spot severity of the 25% risk treatment was statistically indistinguishable from the other three programs. Taken together, these results indicate that pesticide risk can be significantly reduced on golf courses in the US Midwest without sacrificing dollar spot control.

Pesticide Exposure Levels and Risk Assessment in Operators Involved in the Cashew Production in Côte d’Ivoire

To assess the level of producers’ exposure and the health risk in relation to phytosanitary practices in cashew crops in C?te d’Ivoire, a descriptive longitudinal toxicological study was conducted in 2018-2019 with 76 cashew producers in the areas of Mankono, Dabakala and Bondoukou. The data collected permitted the assessment of phytosanitary risks on the health of producers according to the Quebec-IRPeQ pesticide risk indicators. Field observations translated into scenarios were used to determine the exposure levels of producers via the UK-POEM predictive model. The main active substances used were glyphosate, 2,4-D, cypermethrin, acetamiprid, lambdacyhalothrin, profenofos, imidacloprid, deltamethrin, mancozeb and metalaxyl. The risk indicators showed that 2,4-D (TRI = 1332.25; SRI = 432.98), profenofos (TRI = 2550.25; SRI = 637.56) and mancozeb (TRI = 841; SRI = 147.18) among herbicides, insecticides and fungicides respectively could have more adverse health effects after exposure. These findings translated into scenarios specifically showed high exposure of producers to herbicides, with exposure levels ranging from 1.31 mg/kg bw/day to 1.67 mg/kg bw/day, well above the acceptable operator’s exposure levels (AOEL). These health risks could be significantly reduced if the required personal protective equipment is worn. But, recommended doses of pesticides should be reconsidered, because in some cases, applicators exposure remained high despite the protective equipment.

Effect of buffer strips on pesticide risks in freshwaters

Freshwaters and particularly small water bodies are constantly threatened by the use of pesticides in agriculture. These risks have to be mitigated and reduced according to the European Sustainable Use Directive. The creation of vegetated buffer strips is one measure to effectively mitigate the pesticide risk to freshwaters in agricultural landscapes. This study quantifies the buffer strip effects on pesticide risk posed by arable crop farming for German freshwaters using the pesticide risk indicator model SYNOPS. A constant but only slight turnover towards pesticides with lower water body distance requirements over time was observed when no buffer strips were present. However, the presence of buffer strips contributed to a much higher extent to pesticide risk reduction to freshwaters. The chronic risk to freshwaters was reduced by 29% (simulating 5 m buffer strips) and by 47% (simulating 10 m buffer strips). The effect of risk mitigation by buffer strips varied between crop type and pesticide type. Highest effects of buffer strips were achieved for herbicides and in oilseed rape. Overall, the results show that the creation of buffer strips is a crucial step to effectively mitigate pesticide risk to freshwaters in agricultural landscapes.

Pesticide risk indicator for terrestrial adult stages of aquatic insects

Many taxonomic groups of freshwater insects have a reproductive terrestrial life stage, and some are highly sensitive to insecticides. In agricultural landscapes, it is likely that streams and rivers often run along agricultural fields treated with pesticides, but the risk to insects with a reproductive terrestrial life stage due to pesticide exposure is not well-covered by existing risk indicators. Different aquatic insect species may have different strategies for feeding and mating and, thus, different spatial and temporal distribution of the terrestrial abundance. This influences the fraction of individuals that can suffer from pesticide exposure, and thus the risk indicator in this paper includes spatial and temporal distributions of both insect abundance and air born pesticide deposition, in this case multiplied together and weighted with toxicity. The indicator is denoted Adult Stage Risk Indicator, ASRIi,j, and can be calculated for every combination of insect taxon i, and pesticide active ingredient j. An Excel/VBA based model is available as Supplementary material. However, setting up the indicator using another platform is simple, and for any application please refer to this paper.

Novel Pesticide Risk Indicators for Aquatic Organisms and Earthworms

There are many approaches of pesticide risk assessment. Despite their variation in difficulty and information complexity, all of them are intended to predict the actual pesticide risk as accurately as possible, i.e., to predict the behavior and hazard of a pesticide in the environment with high precision. The aim of this study was to develop a risk indicator of pesticide’s negative impact on soil and aquatic organisms. The developed pesticide risk indicator constitutes the sum of points of acute toxicity exposure ratio, long-term toxicity exposure ratio, and the bioconcentration factor. To develop the indicator, mathematical models were used; the input data included the soil and climate conditions of a specific region. Combining the data of pesticide toxicity in the environment allowed for a more accurate risk assessment in terms of using plant protection products. The toxicity and behavior in soil and water of 200 widespread pesticides were studied. It could be concluded that a mathematical model, PEARL 4.4.4, calibrated for region-specific soil-climate conditions, provides a relevant description of the natural translocation and decomposition of pesticides in soils. In addition, the output data of this model can be applied to calculate the risk indicators. The combination of these parameters with pesticide toxicity for non-target groups of organisms allows the risk indicator to be a universal tool for predicting the negative impact of pesticides on the environment at the regional level.

Integrated management of pesticides in an intensive agricultural area: a case study in Altinova, Turkey

Pesticide contamination of groundwater is a common critical problem faced by many countries due to excessive and unconscious applications. As a result of increasing concerns about pesticides, several qualitative and quantitative risk assessment models/indicators were developed and applied. In this study, a practical approach was presented for the protection of groundwater from pesticide contamination. The first phase is the assessment of the specific vulnerability of groundwater to pesticide contamination using the DRASTIC-Pesticide model. The second phase is the monitoring and assessment of groundwater quality to verify vulnerability assessment. The third phase is to assess the impacts of pesticides on the environment and human health using a commonly applied pesticide risk indicator, the environmental impact quotient (EIQ). The pilot study area (PSA) is the Altinova region at Antalya city of Turkey which exhibits intensive agricultural activities and covers an approximate surface area of 75 km2. A total of 25 groundwater wells were chosen for monitoring of groundwater quality where four sessions of seasonal field measurements were conducted for 1 year. Two sessions of water quality analyses were also performed for many physical, bacteriological, and chemical parameters, including pesticides. Additionally, soil samples were analyzed, site surveys were conducted, and other relevant information (topographical, geological and meteorological characteristics, pesticide use and toxicological data sets, etc.) was gathered. The PSA was determined to have high vulnerability to contamination of groundwater, and it was verified through monitoring results. The commonly used pesticides in the PSA were ranked according to their risks to select pesticides with the least environmental impacts.

Rice pest management with reduced risk pesticides in India.

Sitapur district in the Uttar Pradesh (U.P.) state of northern India has been observed to consume large amounts of WHO classified "extremely" and "highly hazardous" pesticides, in rice crop, posing significant health and environmental threats. Keeping in view this problem, integrated pest management (IPM) modules were synthesized for rice crop and then compared with non-IPM/farmer's practice (NIPM). This study assisted in identifying pesticides with reduced risk to the environment. To measure and compare risks, environmental impact quotient (EIQ) has been used as a pesticide risk indicator model, between IPM and NIPM programs. Using this model, the field EIQ values (EIQ field use rating or EIQ-FUR), for 32 commonly used pesticides in the region, were evaluated based on dosage, frequency, and percent active ingredients present in the pesticide formulations. The results conclude that copper oxychloride (CuOCl2) (50WP at 1.25kg/ha) and mancozeb (75WP at 1.25kg/ha) were the most detrimental to arthropod parasitoids and were the highest contributors to environmental risk (13-16%), in rice crop. This is based on the comparison of total dosage and active ingredients of pesticides applied under IPM and NIPM, with the total field EIQ values. The IPM modules were observed to have least impact on natural enemies with 30-40% increase in population, while keeping the weed population below 10%. NIPM, on the other hand, had resulted in 20% reduction in crop yields, 50% reduction in biodiversity, and about 150% increase in weed population, relative to the control (untreated) rice fields. Moreover, NIPM practices had been observed to pose 56% greater risk as per the total field EIQ values (62 for IPM and 141 for NIPM). The observations concluded that the EIQ model is a useful tool and can be easily used by the pesticide managers for assessing the risk against NIPM.

Impacto ambiental por uso de plaguicidas en tres áreas de producción de melón en la Comarca Lagunera, México

El uso intensivo de plaguicidas altamente tóxicos, en la producción de cultivos hortofrutícolas especializados, conlleva riesgos ambientales y sociales, que pueden medirse mediante indicadores de riesgo de plaguicidas, para evaluar el potencial de impacto negativo de estos productos en los ecosistemas y comparar los logros de la implementación de prácticas agrícolas sustentables, en términos de reducción de riesgos, por la utilización de plaguicidas. El objetivo de esta investigación fue estimar el potencial impacto ambiental, por uso de plaguicidas, en las tres áreas de mayor producción de melón en la Comarca Lagunera. Se realizó un estudio descriptivo transversal, mediante la aplicación de una encuesta en 19 predios, seleccionados mediante muestreo no probabilístico. El Impacto Ambiental (IA) se evaluó mediante el modelo del Cociente de Impacto Ambiental (CIA), que se basa en el cálculo del CIA y el Cociente de Impacto Ambiental en Campo (CIAC). Los resultados muestran que los plaguicidas que contribuyeron con la mayor carga ambiental en las áreasde estudio fueron: clorotalonil (49 %), azufre elemental (11 %) y endosulfan (10 %), en Mapimí; carbofuran (19 %), endosulfan (18 %) y carbendazim (12 %), en Matamoros-Viesca; y oxicloruro de cobre (20 %), endosulfan (17 %) y mancozeb (17 %), en Tlahualilo. Los sistemas de producción, con los valores del IAmás altos, se identificaron en fechas de siembra intermedias (199 a 500) y tardías (201 a 701), en Mapimí, y fechas tardías (132 a 383) en Matamoros-Viesca. El modelo del CIA permitió identificar a los plaguicidas y los sistemas de producción con el mayor impacto ambiental negativo en las tres principales áreas de producción de melón en la Comarca Lagunera, además de proporcionar una escala cuantificable, que permitirá evaluar y comparar futuros cambios en el uso regional de plaguicidas.

Pesticide Load—A new Danish pesticide risk indicator with multiple applications

Pesticides provide growers with an effective tool for the control of damaging crop pests preventing yield losses that could jeopardise food security. In recent years the potentially adverse effects of their use on human health and the environment has received increasing attention by the public and the competent authorities. In this context reliable pesticide risk indicators are pivotal to assess the potential risk associated with the use of pesticide. Several pesticide risk indicators, serving various purposes, have been developed over the years. Recently, a new pesticide risk indicator, the Pesticide Load (PL), was introduced in Denmark. The PL has replaced the Treatment Frequency Index (TFI) as the official pesticide risk indicator. The PL consists of three sub-indicators for human health, ecotoxicology and environmental fate, respectively. For each of the three sub-indicators a pesticide load (PL) is calculated and expressed as the PL per unit commercial product (kg, L or tablet). PL for human health (PLHH) is based on the risk phrases on the product label, while PL for ecotoxicology (PLECO) is calculated on basis of the LC/LD/EC50 values of the active ingredients for acute toxicity to mammals, birds, fish, daphnia, algae, aquatic plants, earthworms and bees and NOEC values for chronic toxicity to fish, daphnia and earthworms. PL for environmental fate (PLFATE) is calculated on basis of the half-life in soil (DT50), the bioaccumulation factor (BCF) and the SCI-GROW index. PL does not consider the actual exposure, i.e. it reflects the relative risks associated with the use of pesticides. Besides using PL for monitoring the yearly trend in pesticide use and load, the PL was also used for setting up a new pesticide tax scheme and for setting quantitative reduction targets. In Denmark, it is now compulsory for farmers to upload their pesticide use data, i.e. the annual pesticide statistics and the calculation of the PL can be produced on basis of pesticide use data rather than sales data that may not reflect the actual use by farmers. Because pesticide use data is available for each farm, maps providing detailed information on pesticide use in different regions can be produced. From 2010/11 to 2013/14 only minor differences were observed in the PL and, overall, similar trends were observed for the PL and TFI. Significant geographical differences, which could be attributed to differences in crop rotations, were apparent when estimating PL for each of the four major groups of pesticides (herbicides, fungicides, insecticides and plant growth regulators). The maps produced from the pesticide use data revealed significant variation in PL for ecotoxicological effects on aqueous organisms and bees as well as environmental parameters such as leaching potential. It is suggested to use the maps to identify ‘hot spots’ and design monitoring programmes or to launch initiatives that can reduce the PL. By linking information on mode of action to each commercial pesticide product it was also possible to obtain detailed information on the use pattern of the various pesticide modes of action, which is relevant information assessing the risk of evolution of pesticide resistance.

Predictive quality of 26 pesticide risk indicators and one flow model: A multisite assessment for water contamination

Stakeholders need operational tools to assess crop protection strategies in regard to environmental impact. The need to assess and report on the impacts of pesticide use on the environment has led to the development of numerous indicators. However, only a few studies have addressed the predictive quality of these indicators. This is mainly due to the limited number of datasets adapted to the comparison of indicator outputs with pesticide measurement. To our knowledge, evaluation of the predictive quality of pesticide indicators in comparison to the quality of water as presented in this article is unprecedented in terms of the number of tested indicators (26 indicators and the MACRO model) and in terms of the size of datasets used (data collected for 4 transfer pathways, 20 active ingredients (a.i.) for a total of 1040 comparison points). Results obtained on a.i. measurements were compared to the indicator outputs, measured by: (i) correlation tests to identify linear relationship, (ii) probability tests comparing measurements with indicator outputs, both classified in 5 classes, and assessing the probability i.e. the percentage of correct estimation and overestimation (iii) by ROC tests estimating the predictive ability against a given threshold. Results showed that the correlation between indicator outputs and the observed transfers are low (r<0.58). Overall, more complex indicators taking into account the soil, the climatic and the environmental aspects yielded comparatively better results. The numerical simulation model MACRO showed much better results than those for indicators. These results will be used to help stakeholders to appropriately select their indicators, and will provide them with advice for possible use and limits in the interpretation of indicator outputs.

Managing Pesticide Risks for Non-Target Ecosystems with Pesticide Risk Indicators

In the search for effective pesticide risk management tools, the design of pesticide risk indicators is nowadays receiving increasing attention as a complement to more established regulatory strategies. In the present paper, we apply some recently developed pesticide risk indices and test their potential for management purposes. A pilot approach is proposed, which explores pesticide worst-case hazard scenarios at different space-time scales by means of a set of 5 ecotoxicological risk indices. The results are then interpreted from the perspective of a decision support method using the so-called Critical Threshold Value approach. Our risk analysis is then enriched within a multicriteria framework which integrates environmental, agronomic and economic objectives.

Use pattern of pesticides and their predicted mobility into shallow groundwater and surface water bodies of paddy lands in Mahaweli river basin in Sri Lanka

ABSTRACTPesticides applied on agricultural lands reach groundwater by leaching, and move to offsite water bodies by direct runoff, erosion and spray drift. Therefore, an assessment of the mobility of pesticides in water resources is important to safeguard such resources. Mobility of pesticides on agricultural lands of Mahaweli river basin in Sri Lanka has not been reported to date. In this context, the mobility potential of 32 pesticides on surface water and groundwater was assessed by widely used pesticide risk indicators, such as Attenuation Factor (AF) index and the Pesticide Impact Rating Index (PIRI) with some modifications. Four surface water bodies having greater than 20% land use of the catchment under agriculture, and shallow groundwater table at 3.0 m depth were selected for the risk assessment. According to AF, carbofuran, quinclorac and thiamethoxam are three most leachable pesticides having AF values 1.44 × 10−2, 1.87 × 10−3 and 5.70 × 10−4, respectively. Using PIRI, offsite movement of pesticides by direct runoff was found to be greater than with the erosion of soil particles for the study area. Carbofuran and quinclorac are most mobile pesticides by direct runoff with runoff fractions of 0.01 and 0.08, respectively, at the studied area. Thiamethoxam and novaluron are the most mobile pesticides by erosion with erosion factions of 1.02 × 10−4 and 1.05 × 10−4, respectively. Expected pesticide residue levels in both surface and groundwater were predicted to remain below the USEPA health advisory levels, except for carbofuran, indicating that pesticide pollution is unlikely to exceed the available health guidelines in the Mahaweli river basin in Sri Lanka.

Field evaluation of two risk indicators for predicting likelihood of pesticide transport to surface water from two orchards

Two pesticide risk indicators, Pesticide Impact Rating Index (PIRI) and Environmental Potential Risk Indicator for Pesticides (EPRIP), were used to determine the likelihood of off-site transport to surface water of pesticides used in a cherry (Prunus avium cultivars) and an apple (Malus domestica cultivars) orchard. The predictions of off-site transport of some of the pesticides were verified against actual pesticide concentrations in surface water continuously monitored over two years. To our knowledge, only one other study in the published literature has attempted this. Of the chemicals monitored there was good agreement between the predictions and the field measurements from the apple orchard, but less so for the cherry orchard. In both risk indicators the attenuation factor based on the width of the buffer strip over-estimated the effectiveness of the buffer strip. There was good agreement between the EPRIP and PIRI risk assessment except for ethephon which EPRIP rated a higher risk than PIRI and dithianon which EPRIP rated a lower risk than PIRI. A strong correlation was found between the field observations and the EPRIP predicted environmental concentrations for the majority of cases. This study showed that even simple risk indicators (e.g. PIRI and EPRIP) can be good predictors for a first tier risk assessment of pesticide transport to neighbouring water bodies.

Adjustments of the Pesticide Risk Index Used in Environmental Policy in Flanders.

Indicators are used to quantify the pressure of pesticides on the environment. Pesticide risk indicators typically require weighting environmental exposure by a no effect concentration. An indicator based on spread equivalents (ΣSeq) is used in environmental policy in Flanders (Belgium). The pesticide risk for aquatic life is estimated by weighting active ingredient usage by the ratio of their maximum allowable concentration and their soil halflife. Accurate estimates of total pesticide usage in the region are essential in such calculations. Up to 2012, the environmental impact of pesticides was estimated on sales figures provided by the Federal Government. Since 2013, pesticide use is calculated based on results from the Farm Accountancy Data Network (FADN). The estimation of pesticide use was supplemented with data for non-agricultural use based on sales figures of amateur use provided by industry and data obtained from public services. The Seq-indicator was modified to better reflect reality. This method was applied for the period 2009-2012 and showed differences between estimated use and sales figures of pesticides. The estimated use of pesticides based on accountancy data is more accurate compared to sales figures. This approach resulted in a better view on pesticide use and its respective environmental impact in Flanders.

Helping farmers to reduce herbicide environmental impacts

While pesticides help to effectively control crop pests, their collateral effects often harm the environment. On the French island of Reunion in the Indian Ocean, over 75% of the pesticides used are herbicides and they are regularly detected in water. Agri-environmental models and pesticide risk indicators can be used to predict and to help pesticide users to reduce environmental impacts. However, while the complexity of models often limits their use to the field of research, pesticide risk indicators, which are easier to implement, do not explicitly identify the technical levers that farmers can act upon to limit such transfers on their scale of action (the field). The aim of this article is to contribute to developing a decision support tool to guide farmers in implementing relevant practices regarding the reduction of pesticide transfers. In this article, we propose a methodology based on classification and regression trees. We applied our methodology to a pesticide risk indicator (I-PHY indicator) for identifying the importance of the variables, their interactions and relative weight in contributing to the score of the indicator. We applied our methodology to the assessment of transfer risks linked to the use of 20 herbicides applied to all soils in Reunion and according to different climate, plot management and product application scenarios (4096 scenarios tested). We constructed regression trees which identified, for each herbicide on each soil type, the contribution made by each input variable to the construction of the indicator score. The tree is represented graphically, and this aids exploration and understanding. The 20 herbicides were divided into 3 groups that differed through the main contributing variable to the indicator score. These variables were all technical levers available to farmers to limit transfer risks. These trees then become decision support tools specific to each pesticide user, enabling them to take appropriate decisions with a view to reducing pesticide environmental impacts.

Evaluating risk from insecticide use at the field and regional scales in Iran

Approximately 50% of all pesticides registered in Iran are insecticides with potential risk to human health and the environment. The environmental impact quotient (EIQ) is a pesticide risk indicator that was used to rank the inherent risk of 48 insecticides in use in 28 Iranian provinces and evaluate their environmental impact (EI) at the field and provincial scales over three growing seasons from 2001 to 2005. The results indicate that the introduction of new insecticides over the past decades has produced a negligible decrease in inherent risk. About 75% of provinces had low EI scores of 0.62–11.3. The highest EI and EI/ha scores were found in Kerman and Mazandaran provinces, mainly from increased usage (amount of active ingredient) rather than increased toxicity of insecticides. Inherent toxicity (EIQ) was not significant for increased EI in contrast to the increase in pesticide usage. On average, diazinon comprised 37% of total usage, carbaryl 12.2% and teflubenzuron 8% of total usage. The toxicity of these insecticides ranked lower for EIQ. In contrast, the total usage of environmentally high-risk insecticides (imidacloprid, fipronil, lindane) was relatively lower during the study period. Overall, the increased use of insecticides was not related to the increase in the area under cultivation, but to the type of crop grown (pistachios, vegetables) and to inappropriate spraying equipment and inadequate storage practices, both of which are common problems in developing countries.

Selecting pesticides for inclusion in drinking water quality guidelines on the basis of detection probability and ranking

Pesticides released into the environment may pose both ecological and human health risks. Governments set the regulations and guidelines for the allowable levels of active components of pesticides in various exposure sources, including drinking water. Several pesticide risk indicators have been developed using various methodologies, but such indicators are seldom used for the selection of pesticides to be included in national regulations and guidelines. The aim of the current study was to use risk indicators for the selection of pesticides to be included in regulations and guidelines. Twenty-four risk indicators were created, and a detection rate was defined to judge which indicators were the best for selection. The combination of two indicators (local sales of a pesticide for the purposes of either rice farming or other farming, divided by the guideline value and annual precipitation, and amended with the scores from the physical and chemical properties of the pesticide) gave the highest detection rates. In this case study, this procedure was used to evaluate 134 pesticides that are currently unregulated in the Japanese Drinking Water Quality Guidelines, from which 44 were selected as pesticides to be added to the primary group in the guidelines. The detection probability of the 44 pesticides was more than 72%. Among the 102 pesticides currently in the primary group, 17 were selected for withdrawal from the group.

Development and field validation of an indicator to assess the relative mobility and risk of pesticides in the Lourens River catchment, South Africa

A GIS based pesticide risk indicator that integrates exposure variables (i.e. pesticide application, geographic, physicochemical and crop data) and toxicity endpoints (using species sensitivity distributions) was developed to estimate the Predicted Relative Exposure (PREX) and Predicted Relative Risk (PRRI) of applied pesticides to aquatic ecosystem health in the Lourens River catchment, Western Cape, South Africa. Samples were collected weekly at five sites from the beginning of the spraying season (October) till the beginning of the rainy season (April) and were semi quantitatively analysed for relevant pesticides applied according to the local farmers spraying programme. Monitoring data indicate that physicochemical data obtained from international databases are reliable indicators of pesticide behaviour in the Western Cape of South Africa. Sensitivity analysis identified KOC as the most important parameter influencing predictions of pesticide loading derived from runoff. A comparison to monitoring data showed that the PREX successfully identified hotspot sites, gave a reasonable estimation of the relative contamination potential of different pesticides at a site and identified important routes of exposure (i.e. runoff or spray drift) of different pesticides at different sites. All pesticides detected during a monitored runoff event, were indicated as being more associated with runoff than spray drift by the PREX. The PRRI identified azinphos-methyl and chlorpyrifos as high risk pesticides towards the aquatic ecosystem. These results contribute to providing increased confidence in the use of risk indicator applications and, in particular, could lead to improved utilisation of limited resources for monitoring and management in resource constrained countries.

Evaluation of pesticide impact rating index (PIRI) model as a pesticide risk indicator

Systematic methods for assessment of potential risk of pesticides to the environment can be consideredas valuable tools in decision-making and policy formulation. Pesticide Impact Rating Index (PIRI) isa user-friendly simple risk indicator and it can be used to rank pesticides in terms of their mobility. Thepredictions given by using PIRI for the pollution potential of pesticides on shallow ground waterbodies of Kalpitiya area in Sri Lanka was compared with the field experiments. Cultivated areas ofKalpitiya peninsula were selected for field trials.Oxytluorfen for onions, Chlorpyrifos, Diazinon, Dimethoate, Carbofuran, Carbaryl, Mcthornyl,Irnidacloprid, Fenthion and Captan for chili were applied in replicates at recommended applicationrates for particular crops. Each area was irrigated at the rate of 20 mm/day. The soil considered wasthe sandy soil with the organic matter of 1.6±0.2%. Residue levels of applied pesticides were measuredusing Gas Chromatographic and High Performance Liquid Chromatographi methods in irrigation wellsin 100 m diameter area at 3 m depth for 3 months in one week intervals from the time of pesticideapplication. The detected pesticides were confirmed using Gas Chromatographic MassSpectrophotometric method.Out of applied pesticides, Dirnethoate, Carbofuran, and Chlorpyrifos leached 3 m water table in 24±4days, 25±3 days and 3 5±6 days respectively after application of each pesticide. The field monitoringresults were 74% compatible with the predictions from PIRI. This indicates that PIRI can be used asa simple risk indicator model for the prediction of pesticide risk to water bodies.