Collection of Data on Pesticides in Maize and Tomato in Africa: Protocol for Africa Pesticide Residue Survey Study.

Pesticide use has grown rapidly in West Africa over the past decades. Regulatory capacity has not kept pace with the rapid proliferation of pesticide products and on-farm use. As a result, health and environmental impacts from the growing use of pesticides, despite their potential importance to food safety, remain largely unmonitored, underreported, and poorly understood by key stakeholders. This study protocol was the document for conducting a pesticide survey study to identify the most critically emerging pesticides across the Continent of Africa. Multiple countries were selected in this study to represent the north, east, south, and west regions of Africa. Two food commodities, maize and tomato, were chosen to monitor the pesticide level for food safety. This study protocol describes the fieldwork and laboratory work per the standards of Good Laboratory Practices (GLP) and ISO-17025 and US EPA 860 Residue Chemistry Guidelines but the survey study performed was not considered as a GLP or ISO 17025 study. This is because many steps were not able to be closely monitored per the GLP requirements. This protocol describes the requirements for a pesticide residue study in food collected from local markets. This protocol describes the test commodities, sampling methods, sample transfer/shipping, storage stability, sample analysis, sample disposal, and documentation and record keeping.

A sensory system at the interface between urban stormwater runoff and salmon survival.

Motor vehicles are a major source of toxic contaminants such as copper, a metal that originates from vehicle exhaust and brake pad wear. Copper and other pollutants are deposited on roads and other impervious surfaces and then transported to aquatic habitats via stormwater runoff. In the western United States, exposure to non-point source pollutants such as copper is an emerging concern for many populations of threatened and endangered Pacific salmon (Oncorhynchus spp.) that spawn and rear in coastal watersheds and estuaries. To address this concern, we used conventional neurophysiological recordings to investigate the impact of ecologically relevant copper exposures (0-20 microg/L for 3 h) on the olfactory system of juvenile coho salmon (O. kisutch). These recordings were combined with computer-assisted video analyses of behavior to evaluate the sensitivity and responsiveness of copper-exposed coho to a chemical predation cue (conspecific alarm pheromone). The sensory physiology and predator avoidance behaviors of juvenile coho were both significantly impaired by copper at concentrations as low as 2 microg/L. Therefore, copper-containing stormwater runoff from urban landscapes has the potential to cause chemosensory deprivation and increased predation mortality in exposed salmon.

Comparative thresholds for acetylcholinesterase inhibition and behavioral impairment in coho salmon exposed to chlorpyrifos.

Chlorpyrifos is a common organophosphate insecticide that has been widely detected in surface waters that provide habitat for Pacific salmon in the western United States. Although chlorpyrifos is known to inhibit acetylcholinesterase (AChE) in the brain and muscle of salmonids, the relationship between sublethal AChE inhibition and more integrative indicators of neuro-behavioral impairment are poorly understood. This is particularly true for exposures that reflect the typical range of pesticide concentrations in the aquatic environment. To directly compare the effects of chlorpyrifos on AChE activity and salmon behavior, we exposed juvenile coho salmon (Oncorhynchus kisutch) to chlorpyrifos (0-2.5 microg/L) for 96 h. A computer-assisted, three-dimensional video imaging system was used to measure spontaneous swimming and feeding behaviors in control and chlorpyrifos-exposed fish. After the behavioral trials, brain and muscle tissues were collected and analyzed for AChE activity. Chlorpyrifos inhibited tissue AChE activity and all behaviors in a dose-dependent manner. Moreover, brain AChE inhibition and reductions in spontaneous swimming and feeding activity were significantly correlated. Benchmark concentrations for sublethal neurotoxicity (statistical departure values) were <0.5 microg/L and were similar for both neurochemical and behavioral endpoints. Collectively, these results indicate a close relationship between brain AChE inhibition and behavioral impairment in juvenile coho exposed to chlorpyrifos at environmentally realistic concentrations.

Sublethal effects of copper on coho salmon: impacts on nonoverlapping receptor pathways in the peripheral olfactory nervous system.

The sublethal effects of copper on the sensory physiology of juvenile coho salmon (Oncorhynchus kisutch) were evaluated. In vivo field potential recordings from the olfactory epithelium (electro-olfactograms) were used to measure the impacts of copper on the responses of olfactory receptor neurons to natural odorants (L-serine and taurocholic acid) and an odorant mixture (L-arginine, L-aspartic acid, L-leucine, and L-serine) over a range of stimulus concentrations. Increases in copper impaired the neurophysiological response to all odorants within 10 min of exposure. The inhibitory effects of copper (1.0-20.0 micrograms/L) were dose-dependent and they were not influenced by water hardness. Toxicity thresholds for the different receptor pathways were determined by using the benchmark dose method and found to be similar (a 2.3-3.0 micrograms/L increase in total dissolved copper over background). Collectively, examination of these data indicates that copper is broadly toxic to the salmon olfactory nervous system. Consequently, short-term influxes of copper to surface waters may interfere with olfactory-mediated behaviors that are critical for the survival and migratory success of wild salmonids.

Pacific steelhead (Oncorhynchus mykiss) exposed to chlorpyrifos: benchmark concentration estimates for acetylcholinesterase inhibition.

Steelhead trout (Oncorhynchus mykiss) were exposed for 96 h to the organophosphate chlorpyrifos to establish benchmark concentration (BMC) values in the low-effect range of brain acetylcholinesterase (AChE) inhibition. The U.S. Environmental Protection Agency (U.S. EPA) benchmark dose software was used to model the data. Benchmark concentrations were determined for a range of inhibition levels at 5, 10, and 20%, at 1 and 2 control standard deviations (SD), and at an experimental limit-of-detection level of 2.5%. One contributing difficulty in establishing precise inhibition BMCs in the lower effect region is the variability associated with the AChE analytical method. To minimize this variability, the Ellman method was modified specifically for analysis of O. mykiss brain tissue. Laboratory-established BMCs for chlorpyrifos were then compared with the U.S. EPA 96-h water quality criteria and with the concentration levels detected in Northwest surface waters that are home to threatened steelhead trout. The U.S. EPA 96-h water quality criteria of 0.083 microg/L is below the BMC(02.5), the limit-of-detection value for this study. The average chlorpyrifos concentration detected during a two-week period in one monitored stream was 0.127 microg/L, which approaches the BMC(02.5). The peak chlorpyrifos concentration detected at 0.482 microg/L is near the BMC(1SD) estimate.