Environmental risk assessment of pesticides in the River Madre de Dios, Costa Rica using PERPEST, SSD, and msPAF models

Abstract

This study assesses the ecological risks (ERA) of pesticides to aquatic organisms in the River Madre de Dios (RMD), which receives surface runoff water from banana, pineapple, and rice plantations on the Caribbean coast of Costa Rica. Water samples collected over 2 years at five sites in the RMD revealed a total of 26 pesticides. Their toxicity risk to aquatic organisms was assessed using three recent ERA models. (1) The PERPEST model showed a high probability (>50 %) of clear toxic effects of pesticide mixtures on algae, macrophytes, zooplankton, macroinvertebrates, and community metabolism and a low probability (<50 %) of clear effects on fish. (2) Species sensitivity distributions (SSD) showed a moderate to high risk of three herbicides: ametryn, bromacil, diuron and four insecticides: carbaryl, diazinon, ethoprophos, terbufos. (3) The multi-substance potentially affected fraction (msPAF) model showed results consistent with PERPEST: high risk to algae (maximum msPAF: 73 %), aquatic plants (61 %), and arthropods (25 %) and low risk to fish (0.2 %) from pesticide mixtures. The pesticides posing the highest risks according to msPAF and that should be substituted with less toxic substances were the herbicides ametryn, diuron, the insecticides carbaryl, chlorpyrifos, diazinon, ethoprophos, and the fungicide difenoconazole. Ecological risks were highest near the plantations and decreased progressively further downstream. The risk to fish was found to be relatively low in these models, but water samples were not collected during fish kill events and some highly toxic pesticides known to be used were not analyzed for in this study. Further sampling and analysis of water samples is needed to determine toxicity risks to fish during peaks of pesticide mixture concentrations. The msPAF model, which estimates the ecological risks of mixtures based on their toxic modes of action, was found to be the most suitable model to assess toxicity risks to aquatic organisms in the RMD. The PERPEST model was found to be a strong tool for screening risk assessments. The SSD approach is useful in deriving water quality criteria for specific pesticides. This study, through the application of three ERA models, clearly shows that pesticides used in plantations within the RMD watershed are expected to have severe adverse effects on most groups of aquatic organisms and that actions are urgently needed to reduce pesticide pollution in this high biodiversity ecosystem.

Pesticide registration, distribution and use practices in Ghana

“…The possible environmental risks have been demonstrated in other studies by Ramo et al (2016) and Teklu et al (2016) in Costa Rica and Ethiopia, respectively. There is, therefore, a need to perform environmental risk assessments of current pesticides use in Ghana to identify pesticides that pose the highest risks to the aquatic environment and to determine threshold levels of the pesticides that are protective of the environment.…”

“…that choosing for a particular pesticides was based on its availability on market in their area of operation, its price and its efficacy for insect pests. From the result, it is important to encourage farmers to use pesticides only when necessary as anticipated pest occurrence and pesticides application may lead to problems of pest resistance, environmental pollution, and occupational exposure among others (Metacalf 1980;Ngowi et al 2001;Ramo et al 2016). The pesticides use and frequency by farmers are provided in Table S1.…”

Toward a conceptual approach for assessing risks from chemical mixtures and other stressors to coastal ecosystem services

“…A selection of 34 chemicals were prioritized and analyzed based on data from the Costa Rican pesticide registration program and interviews with farmers and crop owners. The 30 pesticides included in the sampling program were considered to be the most relevant stressors for this case study (Rämö et al ).…”

“…A total of 26 pesticides were found at 5 sites in the RMD river between 2011 and 2012: 7 herbicides, 13 fungicides, and 6 insecticides or nematicides were found in mixtures of up to 16 pesticides (Rämö et al ). The risks of these pesticide mixtures were assessed by Rämö et al () using the multi substance Potentially affected fraction (msPAF) method (de Zwart and Posthuma ). This method assesses the risks of pesticide mixtures as the potentially affected fraction (PAF) of species, meaning that impacts are translated into ES and that the cumulative risk is assessed at the same time.…”

“…For example, the impact of pesticide pollution on the habitat services provided by aquatic plants may be assessed using msPAF by determining the fraction of aquatic plants potentially affected by pesticide mixtures. Such an assessment was carried out by Rämö et al () and suggested that up to 61% of aquatic plant species in the RMD are potentially affected at the 50% effect level (EC50), an effect level that may be interpreted as unsustainable toxic effects on the populations of the affected species, and subsequently lead to the collapse of those species in the system.…”