Pesticides, rice productivity, and farmers' health: an economic assessment.

The organophosphorus (OP) insecticides were developed before and during World War II The history of their development has been reviewed (Holmstedt 1963; Karczmar 1970; Ursdin 1970; Koelle 1981) In 1936, Schrader synthesized paraoxon, parathion, and octamethylpyrophosphoramide (OMPA, schradan) in a search for an effective cockroach control agent (Ursdin 1970) Parathion use in agriculture began after World War II In 1949, a mixer loader was killed by parathion in Lake Placid, FL (Griffiths et al 1951) Monitoring red blood cell acetyl-cholinesterase (RBC AChE) of exposed workers was begun in 1950 in the Florida citrus industry (Griffiths et al 1951), perhaps the first use of human blood esterase monitoring in agriculture

Blood Cholinesterases as Human Biomarkers of Organophosphorus Pesticide Exposure

Behavioral changes in the rat after low doses of cholinesterase inhibitors

The present study reports two experiments in which a total of 20 participants without prior flight experience practiced the final approach phase in a fixed-base simulator. All participants received self-controlled concurrent feedback during 180 practice trials. Experiment 1 shows that participants learn more quickly under variable practice conditions than under constant practice conditions. This finding is attributed to the education of attention to the more useful informational variables: Variability of practice reduces the usefulness of initially used informational variables, which leads to a quicker change in variable use, and hence to a larger improvement in performance. In the practice phase of Experiment 2 variability was selectively applied to some experimental factors but not to others. Participants tended to converge toward the variables that were useful in the specific conditions that they encountered during practice. This indicates that an explanation for variability of practice effects in terms of the education of attention is a useful alternative to traditional explanations based on the notion of the generalized motor program and to explanations based on the notions of noise and local minima.

The education of attention as explanation of variability of practice effects: learning the final approach phase in a flight simulator.

At a symposium, which has been considered as a landmark in environmental concerns, held at the Institute for Terrestrial Ecology in 1965 the following statements on behavioral toxicology were made (Warner et al. 1966): 

(1)

“The behavior (or activities) of an organism represents the final integrated result of a diversity of biochemical and physiological processes. Thus, a single behavioral parameter is generally more comprehensive than a physiological or biochemical parameter.




(2)

Behavioral patterns are known to be highly sensitive to changes in the steady state of an organism. This sensitivity is one of the key values for its use in exploring sublethal toxicity.




(3)

Behavioral measurements can usually be made without direct physical harm to the organism. With aquatic animals especially, implantation of detectors introduces problems of considerable complexity. Behavioral measurements can avoid this difficulty.”

Behavioral responses of birds to pesticides and other contaminants

Both anecdotal reports from pilots and theories of visual cues would predict lower approaches to narrow or long runways than to wide and short runways. Similar, practice approaches made by pilots to a particular width of runway should lead to an increase in subsequent approach angles flown to wider runways and a decrease in approach angles flown to narrower runways. Two experiments with instrument-rated pilots made quantitative tests and these predictions. In Experiment I, three pilots flew simulated approaches and landings in a fixed-base simulator with a computer-generated image visual display. Practice approaches were flown with an 8,000-ft long runway that was either 75, 150, or 300 ft wide; test approaches were to runways with widths or 75, 100, 150, 200, and 300 ft. In Experiment II, 40 pilots controlled the slant of a moving model runway during simulated night visual approaches. Five different models simulated runways from 100 to 300 ft wide and 3,000 to 9,000 ft long. As predicted, training on a wide runway in Experiment I lowered approach angle in approaches to narrower runways; a narrow practice runway also raised approach angles to wider runways. The magnitude of these practice effects increased as distance from runway threshold decreased. There was also a general tendency for approach angles to decrease as runway width decreased. The latter effect was corroborated in Experiment II; in addition, generated approach angles decreased with increasing runway length. Giving half the pilots information about runway size prior to each approach had no effect on responses. These findings add to the quantitative evidence of danger in night visual approaches due to visual illusions and large variability in the visual perception of approach angle. Language: en

Effect of different runway size on pilot performance during simulated night landing approaches

: The need for study of behavioral difficulties resulting from exposure to pesticides is based upon reports of behavioral difficulties in aerial applicators following organophosphate poisoning and is underscored by a recent plane crash of a cropduster pilot in which prior exposure to several organophosphate pesticides was implicated. The present study examines effects on performance of pigeons and squirrel monkeys of Phosdrin (mevinphos), a cholinesterase-inhibiting pesticide not previously studied in the laboratory. Variable interval schedules of reinforcement were used with both food and water as rewards. A dose related decrease in response rate was observed with all animals. Decrements in behavior were observed at doses below which external symptoms of Phosdrin poisoning occurred, indicating the need for further investigation of the behavioral actions of pesticides.

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Behavioral changes from chronic exposure to pesticides used in aerial application: effects of phosdrin on the performance of monkeys and pigeons on variable interval reinforcement schedules.

Two simulator experiments were conducted to quantify the effectiveness, in terms of pilot performance, of four different visual glidepath indicator systems (the 2-bar VASI, 3-bar VASI, T-VASIS, and PAPI) in the severely reduced nighttime visual environment often referred to as the "black hole." Performance in Experiment I was best with the T-VASIS and decreased with the 3-bar BASI, PAPI, and 2-bar VASI, in that order; but differences between the T-VASIS, 3-bar VASI, and Papi were not statistically significant. Approaches flown withou the ground-vased glidepath indicators tended to be low and extremely variable. Observing behavior was compared in approaches with the T-VASIS and 2-bar VASI. Observing response frequency increased as distance from runway threshold decreased and was significantly higher with the T-VASIS. Differences in performanange provided by a given system and to the rate of observing the indicator during approaches.

Pilot performance during simulated approaches and landings made with various computer-generated visual glidepath indicators.

Previous experiments in this laboratory have demonstrated illusions due to variations in both length and width of runways in nighttime "black hole" approaches. Even though approach lighting is not designed to provide vertical guidance, it is possible that cues from approach lights could interact with cues from runway lighting to reduce illusions due to variation in runway size. Two experiments were conducted to evaluate the effect of approach lighting on perception of approach angle in simulated night approaches. In the first experiment, 40 pilots made simulated visual approaches to a 150- by 6,000-ft runway (45.7-1829 m) with and without a 3,000-ft approach (914 m) light system (ALSF-2). Pilots controlled a moving runway model to produce a constant "normal" angle of approach over the distance range of 23,000 ft (7010 m) to 8,000 ft (2438 m) from threshold. In the second experiment, 24 pilots made simulated approaches to a 150- by 6,000-ft runway which was either fully visible or which had lights of the upwind half occluded. In addition, a 1,400-ft (427 m) abbreviated approach light system (SSALS) was used at three intensities. Decreasing the visible length of the runway by occulting lights of the far half increased mean generated approach angles from 2.2 degrees to 2.7 degrees in agreement with results of a previous experiment involving similar lengths of runways. Neither the presence of equal intensity approach lights nor uncomfortable glare from approach lights 20 times brighter than runway lights had an effect of practical significance on responses. These findings reinforce previous experimental demonstrations of the importance of runway size cues related to varying runway length, and also show that potential size cues provided by approach lights do not prevent illusions due to variations in runway size.

Effects of approach lighting and variation in visible runway length on perception of approach angle in simulated night landings

The need for study of the effects on performance of non-lethal organophosphate insecticide exposure is founded on many reports of behavioral difficulties in aerial applicators following exposure. In this study, a different pair of gerbils served in each of the following schedules of reinforcement: FR 25, FR 75, DRL 12-sec, DRL 20-sec, and VI 1-min. Baseline performance in these tasks tended to be comparable to that of more common laboratory species, but was more variable in the case of the VI 1-min task. Mevinphos doses of 0.20 mg/kg and above produced observable somatic signs of poisoning and also produced dose-related decrements in performance in FR and VI tasks. Performance in the DRL schedule was affected only at a dose of 0.30 mg/kg. No performance deficits or overt somatic signs of poisoning were present at mevinphos doses of 0.10 mg/kg or lower. These results do not agree with those of an earlier study in which decrements in VI performance of pigeons and squirrel monkeys appeared at low mevinphos doses which did not produce overt somatic signs of poisoning. The possibility of variations in mevinphos effect as a function of species and task was discussed.

Henry W. Mertens

Papers

Effect of different runway size on pilot performance during simulated night landing approaches

Behavioral changes from chronic exposure to pesticides used in aerial application: effects of phosdrin on the performance of monkeys and pigeons on variable interval reinforcement schedules.

Pilot performance during simulated approaches and landings made with various computer-generated visual glidepath indicators.

Effects of approach lighting and variation in visible runway length on perception of approach angle in simulated night landings

The effects of mevinphos on appetitive operant behavior in the gerbil