Adverse Effects from Pesticides

As discussed earlier, OC pesticides have played an important part in the management of crop pests. The following pages discuss, in brief, the use and toxicity of selected OC pesticides. 

Cyclodienes are an important group of chlorinated pesticides. The group hep-tachlor includes insecticides such as chlordane, aldrin, dieldrin, endosulfan, and heptachlor and its epoxide. These are used for the control of a variety of plant pests in agriculture and household environments. The entry of cyclodienes to the global market has created easy management for the control of crop pests. They appeared after World War II as tools to protect food crops and control diseases from pests. In fact, humans were protected from malaria, typhus, and loss of food crops by pesticides. 

Carbendazim (F) Carbendazim (F) Carbofuran (I) Carbophenothion (A) Carboxin (F) Chlordane (I) Bavistin, Delsene Bavistin, Delsene Bay 70143, Chinufur, Curaterr, Furacarb, Furadan, Yaltox Garrathion, Trithion Vitavax Belt, Carbodan, Carbosip, Chlor Kil, Chlortox, Corodane, Octa-Klor, Octachlor, Topiclor, Velsicol 1068 

Chlordimeform (A) Chlorobenzillate (I) Chlorothalonil (F) Chlorpyrifos (I) Chlorpyrofos methyl (I) Cyanazine (FI) Cypermethrin (I) 2,4-D (H) Dalapon (H) Fundal, Spanone, Galecron Acaraben, Akar, Benzilan Bombardier, Bravo, Daconil 2787 Dursban, Lorsban Dowco 214, Reldan Bladex, Fortrol Cymbush, Imperator, Ripcord, Barricade 2,4-D Dalapon 85, Radapon 

Demethol-S-methyl (A, I) Metasystox Diazinon (A, I) Basudin, Diazitol 

---

In 1987, the US EPA instituted a policy (52 FR 13305, Inert Ingredients in Pesticide Products) to reduce the potential for adverse effects from pesticide products containing toxic inert ingredients. This policy established data requirements for new inert ingredients and categorized inert ingredients into four lists (Table 1). 

Uses Aniline is an oily liquid used in the manufacture of dyestuffs, intermediates for dyestuffs, and manufacture of rubber accelerators and antioxidant substances. Aniline has been extensively used as an intermediate in the manufacture of plastics, pharmaceuticals, pesticides, isocyanates, and hydroquinones. Occupational exposure to aniline is extensive and as diverse as its industrial uses. Workers associated with the manufacturing of acetanalide bromide, coal tar, colors and dyes, leather, disinfectants, nitraniline, perfumes, rubber, and photographic materials become victims of adverse effects from aniline. 

Many of the principles used in pesticide exposure assessment are applicable to other classes of chemicals, and it is hoped that this book will encourage crossfertilization among disciplines. In particular, continued international co-operation and harmonization will be essential to ensure the protection of workers and the general public from the adverse effects of pesticides. 

Differences of adverse effect from one species to another have long been recognized. Knowledge in this field has been used to develop, for example, pesticides, which are more toxic to pests than to humans and other mammals. Among various species of mammals, most effects of toxicants are somewhat similar. This fact forms the basis for predicting the toxicity to humans from results obtained in toxicologic studies conducted in other mammals, such as the rat, mouse, dog, rabbit, and monkey. There are, however, notable differences in toxicity even among mammals. 

Many of the assumptions under which she was working have now been refuted. Her mechanism of action for the adverse effects of pesticides was that continuous exposure slowly damaged our cell s metabolic machinery. This is fundamentally wrong and has no serious scientific proponents today. Curiously, similar arguments and even Silent Spring itself are invoked today by people suffering from Multiple Chemical Sensitivity (MCS) syndrome (this topic to be dealt with in more detail later in this book). 

Another major difference between the current approach and the previous approach for evaluating the adverse effects of pesticide exposure involves the way in which the toxicity data are interpreted. In the current system, the carcinogenicity data from the chronic rodent studies are extrapolated using mathematical models which provide a numerical estimate of the upper bound of the cancer risk, and these numbers (Q values) are then used for a variety of regulatory purposes. In essence, this approach substitutes mathematical guidelines for the scientific judgement that was the key element in the earlier approach. 

Risk-benefit analysis as related to pesticides will be discussed from the following points of view (1) how does one determine risk, (2) what are the potential adverse health effects in man from exposure to pesticides, (it must be recognized that adverse effects of pesticides on wildlife and non-target organisms are also an important part of risk-benefit analysis. However, because of time limitations we will restrict our consideration to adverse health effects in man), (3) principles and problems concerning the estimation of risk to man from exposure to pesticides and (4) effects of pesticides that are considered to be beneficial. 

With the present major emphasis on the preparation and testing of a seemingly endless number of synthetic organic compounds for pesticidal activity and the clamor over their possible adverse effects on public health and our general environment, comparatively few people realize that certain natural insecticides have been used by man for centuries. The ancient Romans apparently utilized false hellebore as a rodenticide and insecticide (13), and preparations of Tripterygium ivilfordii (thunder-god vine) and Derris species have been employed by the Chinese for hundreds of years as insecticides (16). The insecticidal properties of sabadilla (from Schoenocaulon species) were known in the sixteenth century tobacco was in use as... 

Children s Susceptibility. The information on health effects of endosulfan in humans is derived mainly from cases of accidental or intentional exposure of adults to high amounts of the pesticide, and the main adverse effect is neurotoxicity. No reports of adverse effects in endosulfan-exposed children were found, but it is reasonable to assume that children will exhibit similar signs and symptoms to those in adults under similar exposure conditions. Some studies in animals have provided evidence that young animals respond to endosulfan differently than adult animals (Kiran and Varma 1988 Lakshmana and Raju 1994 Sinha et al. 1995,1997 Zaidi et al. 1985), but there is no conclusive evidence to suggest that young animals are more susceptible than older ones. Further studies that evaluate a number of different end points in young as well as older organisms would provide valuable information. 

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... 

In this study a series of surface water and deep soil samples were analyzed to detect ai migration or runoff of waste pesticides from typical Chemical Control Centers. Entomological evaluation of soil biota and monitoring of dermal exposure to pesticides of mlxer-appllcators took place throughout the 1980 season. No adverse effects as a result of the Chemical Control Centers were detected. 

The term acceptable is used widely to describe safe levels of intake and is apphed for chemicals to be used in food production such as, e.g., food additives, pesticides, and veterinary dmgs. The term tolerable is applied for chemicals unavoidably present in a media such as contaminants in, e.g., drinking water and food. The term PTWI (Provisional Tolerable Weekly Intake) is generally used for contaminants that may accumulate in the body, and the weekly designation is used to stress the importance of limiting intake over a period of time for such substances. The tolerable intake is similar in definition and intent to terms such as Reference Dose and Reference Concentration (RfD/RfC), which are widely used by, e.g., the US-EPA. For some substances, notably pesticides, the ARID (Acute Reference Dose), is also established, often from shorter-term studies than those that would support the ADI. The ARfD is defined as the amount of a substance in food that can be consumed in the course of a day or at a single meal with no adverse effects. 

Many drugs and pesticides readily cross the placenta to reach significant concentrations in fetal plasma. However, other chemicals cross the placenta less readily and their concentrations are lower in the fetal plasma than maternal plasma (6). In the case of the latter chemicals, the placenta may be exposed to higher concentrations of the chemical than the embryo. Thus, any adverse effects of the drugs on development may result from direct effects to the embryo and fetus or from indirect effects through altered placental function (7). 

---