Side effects of pesticides

Board on Agriculture and Natural Resources and Board on Environmental Studies and Toxicology, C.o.L.S. 2000. The Future Role of Pesticides in U.S. Agriculture/ Committee on the Future Role of Pesticides in U.S. Agriculture. 301 pp. 

Carson, R. 1962. Silent Spring. The Riverside Press, Boston, MA. 368 pp. 

Ecobichon, D.J. 2001. Toxic effects of pesticides. In Cassarett and Doull s Toxicology. The Basic Science of Poisons, Klaassen, C., Ed. McGraw-Hill, New York. pp. 763-810. 

Beyond Silent Spring. Chapman Hall, London. 322 pp. 

Graham, J. and Wienere, B. 1995. Risk versus Risk. Harvard University Press, Cambridge, MA. 337 pp. 

---

Koeman, J.H. (Ed.) (1972). Side Effects of Persistent Pesticides and Other Chemicals on Birds and Mammals in the Netherlands. Report by the Working Group on Birds and Mammals of the Committee TNO for Research on Side Effects of Pesticides. TNO-Nieuws 27 527-632. 

De Jong, F.M.W. (1998) Development of a field bioassay for the side effects of pesticides on decomposition. Ecotoxicology and Environmental Safety, 40, 103-114. 

The public awareness of the possible negative side effects of pesticide production and use has definitely led to a greater requirement for responsibility from the chemical industry, greater prudence on the part of farmers, and... 

The lesson we have learned from the many laboratory and field studies of DDT is that real-world observations, as well as sophisticated laboratory experiments, are important in order to unveil possible side effects of pesticides. 

Jorgen H.V. Stenersen, Dr. Philos., is a professor in ecotoxicology at the Biological Institute, University of Oslo. He graduated as Cand. Real, in biochemistry in 1964 (University of Oslo) and subsequently worked at the Norwegian Plant Protection Institute on research related to possible side effects of pesticides. His first interests were the mechanisms behind insect resistance to insecticides, with emphasis on DDT resistance in stable flies. He was also engaged in studies of the extent of DDT contamination of soil, fauna, and humans as a result of DDT usage in orchards. 

With increasing awareness of the side effects of pesticides and the increasing number of cases of pesticide resistance, integrated pest management (IPM) is an important method of pest control. IPM involves using cultural methods of control combined with the use of pesticides. Pesticide use is minimised in an attempt to protect and enhance the activities of beneficial insects (natural enemies and polhnating insects) and extend the life of the pesticides that are available. 

Side effects of fertilisers, pesticides, insecticides, and herbicides... 

As a result, organic fruit growers have to make maximum use of preventative or indirect plant protection measures, some of which were already described in terms of their effect on fruit quality (e.g. lower planting densities, see sections above). However, there remains an increased risk for pests and diseases causing stress, decreased photosynthetic activity and capacity. Also in certain sensitive cultivars, the application of permitted plant protection products (such as lime sulphur) can result in phytotoxic effects or latent stress in trees (Palmer et al, 2002). The decrease in photosynthetic activity by both pest/disease attack and pesticides may, in turn, result in reduced fruit quality. Both long-term latent and short-term acute side effects of organic plant protection products have not yet been sufficiently investigated. 

Once the public had their attention drawn to the chemicals to which they were being exposed, it is hardly surprising that they formd plenty to worry about. There are 75,000-90,000 synthetic chemicals in use, many of which have never been a subject of intensive toxicological testing. Even fewer have been subject to thorough enviromnental impact assessments. These facts were emphasised to the public, especially by some of the NGOs. Virtually, the only time members of the public heard or read about individual chemicals in the media was when they were mentioned as part of scare stories— pesticides in food, contaminants in tap and botded water, side effects of drugs and so... 

Part of the problem was that the side effects were constantly ramifying. A first-order effect—say, the decline or disappearance of a local insect population—led to changes in flowering plants, which changed the habitat for other plants and for rodents, and so on. Another part of the problem was that the effects of pesticides on other species were examined only under experimental conditions. Yet the application of DDT was under field conditions, and as Carson pointed out, scientists had no idea what the interactive effects of pesticides were when they were mixed with water and soil and acted upon by sunlight. 

Having accepted that there is a need for pesticides and that their use will continue for the foreseeable future, RPU focuses on the technologies that minimise the costs and deleterious side effects of such interventions. I shall start by dealing with its three major elements separately however, it is where they can be combined (Figure 8.2) that the greatest benefits accrue. 

Herbicide resistance is currently less of a problem than with the other pesticide groups, although, once it occurs, the effects are profound. Instead, the major interest centres around the control of off-target drift (i.e. application issues), specificity and the use (and side-effects) of certain herbicides with genetically modified crops. The examples listed in Table 8.1 indicate the continuing importance of pre-1980 molecules. For instance, glyphosate has become the most important herbicide, with its recent fall in price, broad spectrum of efficacy, low mammalian toxicity and (where GM crops are acceptable) its compatibility with Roundup ready crops. 

P. C. Jepson (Oregon State Univ., USA) discussed the effects of pesticides on natural enemies that play a critical role in 1PM. The factors governing the key processes underlying pesticide impact were analyzed to explore ways of mitigating the side effects on beneficial organisms. R. ffrench-Constant (Univ. of Bath, UK) described that neonicotinoid resistance was conferred by DDT-R gene in Drosophila, and therefore required no fitness cost. Y. Suzuki (NARO, Japan)... 

Tornier, I. (2001). Side effects of an insect growth regulator on bumble-bees and honey-bees. In Hazards of Pesticides to Bees, Vol. 98 (Belzunces, L., Pelissier, C. and Lewis, G., Eds). INRA, p. 299. 

Schafer, H. and Mnhlen, W. (1996). First experiences to test side-effect of alsystin on bnmble bees (Bombus terrestris L.) in the field. In Proceedings of the Vlth International Symposium on Hazards of Pesticides to Bees (Lewis, G., Ed.). Sept. 17-19, Brannschweig, Germany, Appendix 30. 

All decisions involve tradeoffs. Does the benefit of increased food product ion outweigh possible health risks of a pesticide Do the beneficial effects of a new drug outweigh a potentially dangerous side effect in a small fraction of users The answers are rarely obvious, but we should at least try to base our responses on facts. 

It is very clear, therefore, that there have been many examples of neurotoxic effects, both lethal and sublethal, caused by pesticides in the field over a long period of time. Far less clear, despite certain well-documented cases, is to what extent these effects, especially sublethal ones, have had consequent effects at the population level and above. Interest in this question remains because neurotoxic pesticides such as pyre-throids, neonicotinoids, OPs, and carbamates continue to be used, and questions continue to be asked about their side effects, for example, on fish (Sandahl et al. 2005), and on bees and other beneficial insects (see, for example, Barnett et al. 2007). 

---