Part of the book: Insecticides
This chapter provides insights into the difficulties and challenges of performing risk evaluations of agrochemicals. It is a critical review of the current methodologies used in ecological risk assessment of these chemicals, not their risks to humans. After an introduction to the topic, the current framework for ecological risk assessment is outlined. Two types of assessments are typically carried out depending on the purpose: i) regulatory assessments for registration of a chemical product; and ii) ecological assessments, for the protection of both terrestrial and aquatic ecosystems, which are usually site-specific. Although the general framework is well established, the methodologies used in each of the steps of the assessment are fraught with a number of shortcomings. Notwithstanding the subjectivity implicit in the evaluation of risks, there is scepticism in scientific circles about the appropriateness of the current methodologies because, after so many years of evaluations, we are still incapable of foreseeing the negative consequences that some agrochemicals have in the environment. A critical appraisal of such methodologies is imperative if we are to improve the current assessment process and fix the problems we face today. The chapter reviews first the toxicity assessment methods, pointing to the gaps in knowledge about this essential part of the process and suggesting avenues for further improvement. Deficiencies in the current regulations regarding toxicity testing are discussed, in particular the effect of the time factor on toxicity and the issue of complex mixtures. Other matters of concern are the extrapolation of toxicity data from the individual to the population and community levels, and the sub-lethal effects. The exposure assessment methods are dealt with in a second place. These rely on modelling and actual measurements of chemical residues in the environment. Various techniques employed to determine to exposure and bioavailability of agrochemicals to the various organisms in both aquatic and terrestrial ecosystems are reviewed. Again, the shortcomings and gaps in knowledge are addressed and suggestions for improvement are pointed out. Then, the process of putting together the information from the toxicity and exposure assessments to evaluate risks is discussed. Tiers I and II of the risk assessment are reviewed. The challenge here is to keep objectivity in the evaluations; this may require the introduction of new methods of risk assessment. Finally, the risk assessment implies establishing a management strategy that aims at reducing or minimising the impacts of agrochemicals under normal agricultural scenarios. Recommendations are often case-specific and need to be based on sound science as well as common sense principles. The chapter concludes with a summary of issues that need to be considered for improving risk assessments of agrochemicals.
Part of the book: Toxicity and Hazard of Agrochemicals
This chapter focuses on the detrimental effects that pesticides have on managed honey bee colonies and their productivity. We examine first the routes of exposure of bees to agrochemicals used for crop protection and their application to crops, fate and contamination of water and plants around the fields. Most of the time, the exposure of bees to pesticides is through ingestion of residues found in the pollen and nectar of plants and in water. Honey bees are also exposed to pesticides used for the treatment of Varroa and other parasites. The basic concepts about the toxicity of the different kinds of pesticides are explained next. Various degrees of toxicity are found among agrochemicals, and emphasis is given to the classic tenet of toxicology, “the dose makes the poison,” and its modern version “the dose and the time of exposure makes the poison.” These two factors, dose and time, help us understand the severity of the impacts that pesticides may have on bees and their risk, which are analysed in the third section. Sublethal effects are also considered. The final section is devoted to some practical advice for avoiding adverse impacts of pesticides in beekeeping.
Part of the book: Beekeeping and Bee Conservation
Contamination of corn, peanuts, milk and dairy products with aflatoxins is a worldwide problem, particularly in subtropical regions where the climatic conditions are ideal for the growth of Aspergillus flavus, the fungi that produces these toxins. Developing countries have major difficulties in marketing these products abroad due to the stringent international regulations concerning this carcinogenic toxin. Adding to the problem is the analytical cost involved in monitoring the produce, which require sophisticated instrumentation and qualified personnel, neither of which are available for field testing. The development of a rapid Aflatoxin Quicktest™ provides an effective, reliable and cheaper option for screening levels of aflatoxin above the regulatory thresholds in such produce. The test consists of a lateral flow device (LFD) coated with antibodies specific to aflatoxin B1, although it detects other aflatoxins (i.e. G and M) with high cross-reactivity. Its high sensitivity allows analysis of these toxins in the range 2–40 μg/kg of sample in 15 minutes, plus the time for extraction, which varies among different products. Quantification of the test results is done using a Quick Reader, by comparing the readings of individual tests against a standard curve of the analytes in the same manner as it is done with any other analytical equipment. A validation study was carried out using peanuts from Australia and peanuts and corn from Timor-Leste to assess the performance of the Aflatoxin Quicktest™. Results obtained with the LFD showed a good correlation with the standard analytical measurements by HPLC-fluorescence (r2 above 0.90 for all cases), indicating the Aflatoxin Quicktest™ is capable of measuring levels of aflatoxins accurately and reliably. Given their ease of use, low cost and fast processing time, the Aflatoxin Quicktest™ can be used for screening agricultural produce in countries that cannot afford the costly alternative of using specialised personnel and equipment.
Part of the book: Poisoning