Toxicity testing, pesticides

The full extent of the toxicity of pesticides to aquatic life is not known. Although chronic toxicity testing is required for new substances, little is known about the long-term effects of older pesticides. Also, very little is known about the toxicity and occurrence of the products formed when pesticides break down (metabolites) or the many non-pesticidal additives (co-formulants and adjuvants) used in pesticide formulations. However, the future is looking brighter. New modelling techniques, EQS development, and the involvement of the NRA in the pesticide registration process, coupled with the development of newer, less persistent pesticides with lower dose rates, all should help to reduce the risk of pesticide pollution. 

With improvements in scientific knowledge and related technology, there is an expectation that more environmentally friendly pesticides will continue to be introduced, and that ecotoxicity testing procedures will become more sophisticated. There is much interest in the introduction of better testing procedures that work to more ecologically relevant end points than the lethal toxicity tests that are still widely used. Such a development should be consistent with the aims of organizations such as FRAME and ECVAM, which seek to reduce toxicity testing with animals. Mechanistic biomarker assays have the potential to be an important part of... 

A waste is toxic under 40 CFR Part 261 if the extract from a sample of the waste exceeds specified limits for any one of eight elements and five pesticides (arsenic, barium, cadmium, chromium, lead, mercury, selenium, silver, endrin, methoxychlor, toxaphene, 2,4-D and 2,4,5-TP Silvex using extraction procedure (EP) toxicity test methods. Note that this narrow definition of toxicity relates to whether a waste is defined as hazardous for regulatory purposes in the context of this chapter, toxicity has a broader meaning because most deep-well-injected wastes have properties that can be toxic to living organisms. 

Schreiber, B. and N. Brink. 1989. Pesticide toxicity using protozoans as test organisms. Biol. Fertility Soils 7 289-296. 

Federal agencies such as the FDA and EPA require a battery of toxicity tests in laboratory animals to determine an additive s or a pesticide s potential for causing adverse health effects, such as cancer, birth defects, and adverse effects on the nervous system or other organs. Tests are conducted for both short-term (acute) and long-term (chronic) toxicity. For chronic effects other than cancer, laboratory animals are exposed to different doses to determine the level at which no adverse effects occur. This level is divided by an uncertainty or safety factor (usually 100) to account for the uncertainty of extrapolating from laboratory animals to humans and for individual human differences in... 

Before this topic is left behind, it should be noted that statistical significance is by no means the only consideration in interpretation of toxicity test results. If, in our particular case, the pathologist were to inform us that the brain lesion observed was extremely unusual or rare, we should certainly hesitate to dismiss our concerns because of lack of statistical significance. The toxicologist needs equally to understand biological significance, and, in this case, would almost certainly pursue other lines of investigation (perhaps an ADME study to determine if the pesticide reaches the brain, or a toxicity test in other species) to determine whether the effect was truly caused by the chemical. 

OECD. 2001a. Guidance document on acute oral toxicity testing. OECD Series on Testing and Assessment No. 24. Environment Directorate, Joint Meeting of the Chemicals Committee and the Working Party on Chemicals, Pesticides and Biotechnology. ENV/JM/MONO(2001)4. Paris OECD. 

Nonclinical Reproductive Toxicity Testing Requirements for Drugs, Pesticides, and industriai Chemicais in india and China... 

Prenatal developmental toxicity testing of chemicals and pesticides requires evaluation of both cartilaginous and ossified skeletal components, but the corresponding testing guidelines do not specify how. Double staining is the preferred method and is strongly recommended. 

ASTM (American Society for Testing and Materials). (1988). Standard guide for conducting 10-day static sediment toxicity tests with marine and estuarine amphipods. In Annual Book of ASTM Standards, Pesticides, Resource Recovery, Hazardous Substances and Oil Spill Responses, Waste Disposal, Biological Effects, 11.04, ASTM E 1367. Ed. by ASTM, Philadelphia, USA, pp. 732-757. 

The method is based on the perturbation of the respiratory activity of yeast, Saccharomyces cerevisiae, immobilized on an agar gel containing the culture medium (i.e., agarized medium ), by the toxic test substance. Glucose is used as substrate while the substances tested consist of several metallic ions, phenols and cationic or anionic surfactants, pesticides and other toxics. 

The methods here proposed are target oriented that is the sought for analyte is known to the analyst. This occurs in the situations where the grower must use a certain production protocol, including pesticide treatments, as stated by contract. In the case where the analyte is not known, the assay can be used as a toxicity test able to detect the presence of a total anticholinesterase activity (TAA). 

Generally, it takes some five to seven years to bring a pesticide to market once its pesticidal properties have been verified. Many tests must be conducted to determine such things as the compound s synthesis, its chemical and physical properties, and its efficacy. In addition, in order for registration for use by the US EPA, numerous toxicity tests are undertaken including those for acute toxicity, those for chronic effects such as reproductive anomalies, carcinogenesis, and neurological effects and those for environmental effects. 

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