Cholinergic Pesticides Cause Negative Neuronal Effects in Honeybees

by Lia Metzger

Recently, pesticides that target cholinergic neurotransmission have been found to aid in the decline of insect pollinators. In particular, neonicotinoids (nicotinic receptor agonists) and organophosphate miticides (acetylcholinesterase inhibitors) are commonly used and thus, frequently come in contact with honey bees. Palmer et al. (2013) investigated how these pesticides affect the neurophysiology of honey bees by using recordings from mushroom body Kenyon cells. Instead of studying the learning and behavior of honey bees that are exposed to neonicotinoids and organophosphate miticides, the authors used whole-cell recordings from Kenyon cells in honey bee brains, and assessed the native connectivity and nAChR expression in KCs. They found that the two neonicotinoids, imidacloprid and clothianidin, and coumaphos oxon decreased the KC excitability by inhibiting action-potential firing and reduced KC responsiveness to ACh. When the honey bee brains were exposed to both neonicotinoids and miticides as is common in large crops, the combined exposure added to the effects on KC excitability and nAChR-mediated responses. The honey bees are usually exposed to much higher concentrations of cholinergic pesticides, which indicates that the negative effects on the neurophysiological responses of the mushroom body cells would be heightened in reality. Continue reading

Acute Pesticide Poisoning in South Korea

by Kahea Kanuha

Occupational pesticide poisoning is a big health problem among agricultural workers, but there have been few studies on the differences, if any, in risk factors related to severity of pesticide poisoning. Kim et al. (2013) interviewed 1,958 male farmers in South Korea to explore work-related risk factors related to acute occupational pesticide poisoning according to the severity of the poisoning. It was found that the risk of acute occupational pesticide poisoning increased with total days of pesticide application, working on larger farms, not wearing personal protective equipment such as gloves or masks, not following pesticide label instructions, applying the pesticide in full sun, and applying the pesticide upwind. Continue reading

Pesticide Exposure May Degrade Human Cognitive Function

by Kahea Kanua

Pesticides are widely used toxins, yet research is only beginning to understand their effects on human brain and body functioning. In the United States, it is estimated that close to 8 billion dollars is spent on pesticides each year, yet only a few studies have examined the cognitive and neuropsychological impact of pesticide exposure, to mixed results. Schultz and Ferraro (2013) compared neuropsychological test performance of individuals with an occupational history of pesticide exposure to individuals with no such exposure history. The results suggested that occupational exposure to pesticides results in significant, and age-related, decline in some aspects of neuropsychological performance and information processing. Continue reading

Organophosphate Pesticides Cause DNA Damage in Rats

by Kahea Kanuha

The growing use of pesticides in large-scale agricultural applications as well as for household purposes has resulted in their widespread distribution in the environment. To see if pesticide exposure damaged DNA, Ojha et al. (2011) evaluated the genotoxicity of chlorpyrifos (CPF), methyl parathion (MPT), and malathion (MLT), three organophosphate pesticides, when given individually or in combination to rats. The results showed that even a single dose of CPF, MPT, or MLT caused significantly high levels of DNA damage in all the rat tissues examined. DNA damage was also observed in microscopic examinations of tissue samples from the liver, brain, kidney, and spleen of rats exposed to one or more pesticides. It was also observed that the damaged DNA is repaired by the endogenous repair systems with time. When the pesticides are given together, they do not potentiate …

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Honeybees Exposed to Acetylcholinesterase Inhibitors Exhibit Impaired Motor Function

Stress from parasites, pathogens, and pesticides have been contributing to the global decline of populations of honeybees and many pollinators for the past two decades. Specifically, the use of pesticides that affect neuromuscular functioning and kill parasitic mites have caused the accumulation of acaricides, or mite pesticides, in the wax combs of bees’ hives. To investigate the possibility of this accumulation contributing to the decline of bee populations, Williamson et al. (2013) studied the effects of prolonged exposure to pesticides that inhibit acetylcholinesterase (AChE) on the physiology and behavior of bees. Adult worker bees were fed sub-lethal concentrations of four AChE inhibitors in sucrose solutions and then were observed for walking, stopped, grooming, and upside down behavior. After the behavioral study, the bees were dissected to confirm that the four compounds they assayed or their metabolites were responsible for the change in behavior by testing for transcript expression levels of two honeybee AChE inhibitors and through biochemical assays. All AChE inhibitors caused increased grooming behavior, but coumaphos in particular caused more grooming and symptoms of sickness as the concentration increased. The authors found that the effects of pesticides that inhibit AChE on the motor functioning of bees could reduce their survival and contribute to the decline of bee colonies. —Lia Metzger

                  Williamson, S.M., Moffat, C., Gomerall, M.A., Saranzewa, N., Connolly, C.N., Wright, G.A., 2013. Exposure to acetylcholinesterase inhibitors alters the physiology and motor function of honeybees. Frontiers in physiology 4.

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Record of Contaminant Exposure Found in Blue Whale Earplug

The blue whale is the largest animal on earth and an Endangered Species.  The blue whale population has not only been affected by whaling activities but also by anthropogenic activities such as fishing entanglement, boat strikes, climate change and chemical emissions. Many of the resulting contaminants of the latter are found to reside in blubber and other lipid rich layers. Blue whales, and other large baleen whales, accumulate layers of earwax, known as cerumen, throughout their lifetimes. This wax builds up over time and produces dark and light colored layers, or laminae, which represent periods of feeding or migration. While early earplug analysis was used to age whales, it was recently discovered that it is possible to reconstruct lifetime profiles of hormones, mercury, and other pollutants. in whales.  Similar to blubber, these contaminants build up in the whale’s earplug in large enough concentrations to quantify. Tumble et al. (2013) looked at the earplug of a male blue whale to examine lifetime contaminant and hormonal profiles. They found 24 different laminae and estimated the whale’s age to be 12 years ± 6 months. Looking at the hormone levels, they were able to age the whale’s sexual maturity. When the contaminants were examined, it was found that much of the contaminants came from mother during the first 12 months. The mercury profiles showed peaks as a result of environmental and anthropogenic mercury increase. —Chloe Mayne
Trumble, S., Robinson, E., Berman-Kowalewski, M., Potter, C., Usenko, S., 2013. Blue whale earplug reveals lifetime contaminant exposure and hormone profiles. PNAS published ahead of print September 16, 2013,doi:10.1073/pnas.1311418110.

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Pesticide Concentrations in Stream Sediments from Three Farm Management Approache

The relative impacts of organic, integrated, and conventional sheep and beef farms on the physical and chemical properties of streams have been studied in the past, as well as the impact on stream macroinvertebrates. To determine if these different farming practices affect pesticide residues in streams, Shahpoury et al. (2013) quantified chlorinated pesticides in 100 sediment samples from 15 streams in New Zealand, finding that streams in all three farming categories contained pesticides in the stream sediment, but sediments from conventional farms contained significantly higher concentrations of dieldrin, endosulfans, current-use pesticides, and chlorinated pesticides compared to organic and integrated farms. —Kahea Kanuha

Shahpoury, B., Hageman, J., Matthaei, C., Magbanua, S., 2013. Chlorinated pesticides in stream sediments from organic, integrated and conventional farms. Environmental Pollution 181, 219-225.

There is an increasing global interest in understanding how different farm management approaches affect the environment. Three such management approaches are organic, integrated, and conventional. Organic farming avoids the use of synthetic pesticides and fertilizer, with the goal of using environmentally sustainable approaches to farm management. Conventional farming uses these chemicals. Integrated farming aims to achieve optimal results by finding a balance between the economic benefits of synthetic fertilizers and pesticides and their environmental costs. Pesticides are of an increasing concern because they often have unintentional impacts on non-target organisms and may accumulate in the tissue of animals and humans. In addition, they persist in the environment for a long time and may continue to have environmental impacts long after initial application.
Shahpoury et al. collected sediment samples from 15 streams passing through sheep/beef farms on the South Island of New Zealand. The farms were arranged in clusters at five locations, each cluster comprising three neighboring farms using different farm management techniques: organic, conventional, and integrated. Sediment sample extracts were analyzed for 19 legacy pesticides and 5 current-use pesticides. The current-use pesticides selected for this analysis have been widely applied, previously detected in groundwater systems, are highly toxic compared to other pesticides, and have high volatilization potentials, making them prone to vapor drift from and between farms.
To more easily understand the data, the pesticide concentrations were split into groups for analysis: dieldrin, endosulfans, current-use pesticides, and all pesticides. Dieldrin was originally developed in the 1940s as an alternative to DDT and was widely used in the 1950s—1970s. However, long-term exposure has proven toxic to a wide range of animals, including humans; dieldrin has been linked to a range of human health problems and is now banned in most of the world. Endosulfans are highly toxic insecticides banned in New Zealand in January 2009. Current-use pesticides are pesticides registered for use in New Zealand when the sampling took place, while legacy pesticides are pesticides, often very toxic, applied in the past that have remained in the environment.
For each of these pesticides or pesticide groups, mean concentrations were found to be highest in stream sediments from conventional farms. A previous study of the same 15 sheep/beef farming streams found that stream macroinvertebrate communities were more degraded in streams passing through conventional farms than through integrated or organic farms. It is certainly possible that the higher pesticide concentrations found in stream sediments from conventional farms have contributed to the macroinvertebrate community degradation.

Chlorinated pesticides were found throughout the study areas regardless of the farm management strategies applied during the 8—11 years preceding the study. One explanation of this is the high volatilization potential of some pesticides. This results in the pesticides being volatized or evaporated into the air and then carried by wind into a different area. As the impacts and concentrations of pesticides are further studied, it seems clear that pesticide use in farming often has unintended and long-range impacts on areas different from those where pesticides were originally applied.

Mortality of Bees Exposed to Neonicotinoid Clouds around Corn Drilling Machines

Several studies have linked the spring sowing of maize seed to the lethal poisoning of bees and have found that worker bees coming in contact with the exhaust from the drilling machines became contaminated with insecticides and rapidly died. In previous studies with still caged bees and free bees, the correlation between the particles from the drilling machines and the poisoning of bees was not clear. To specify how close the bees have to be to be poisoned, Girolami et al. incorporated the distance from the drilling machines, the type of drilling machine, and the number of times the bees had to pass by the machines before they were killed.  The authors also ran the drilling machines with 200 g of Talc added to the seed containing hoppers during three trials in order to capture the extent of the exhaust cloud. After being exposed to high humidity, bees that were moved alongside the machines were lethally poisoned. No significant difference in bee mortalities was found between modified and unmodified corn drillers. The exhaust cloud extended approximately 20 feet around the drilling machine. —Lia Metzger

                  Girolami, V., Marzaro, M., Vivan, L. Mazzon, L., Giorio, C., Marton, D., Tapparo, A., 2013. Aerial powdering of bees inside mobile cages and the extent of neonicotinoid cloud surrounding corn drillers. Journal of Applied Entomology 137, 35-44.

                  In order to mimic the movement of foraging bees, ten cages, each containing one bee, were attached to a four meter aluminum bar, held 2.5 meters high, and walked by the side of the drilling machine. In some trials, the bees were held at 2, 4, and 6 meters from the still drilling machine, and then placed in either lab humidity or high humidity to test for the lethality of the neonicotinoid cloud. In addition, the bees were walked 1—5 meters or 5—9 meters from the right side of the mobile drilling machine and parallel to its movement for 30 seconds. Then the caged bees made a U-turn around the drilling machine and were walked along the left side, reflecting the movement of bees making a round-trip around the sowing field. To test for the exposure to insecticides in the exhaust, the bees underwent chemical analysis and were only exposed on one side of the drilling machine in the same way. This allowed for the authors to differentiate the levels of contaminants on each side of the drilling machines and the lethality of the exhaust at varying distances from the machines.
                  The authors found bees that had been exposed at 2, 4, and 6 meters by passing by the drilling machine rapidly died from clothianidin if they were placed in high humidity afterward. Mapping the deaths of the bees between 2 to 12 meters on the right side and up to 8 meters on the left side of the drilling machine, the extent of the neonicotinoid cloud was measured as approximately 10 meters on each side and 2 meters high. Possible change in the shape of the cloud was considered, but the proposed elliptical shape formed by wind and movement would not reduce the extent of the cloud. Even though the modified drilling machines direct their exhaust at the ground instead of at a 45° anglethere was no significant difference between the mortality of bees passing by modified or unmodified drilling machines. Machines sowing seeds that were coated in fungicide did not cause significant poisoning to the bees, but the coatings clothianidin, imidacloprid, and thiamethoxam all caused more than 50 % of the bees that passed by to die. Furthermore, the chemical analysis revealed that all of the bees contained very large quantities of insecticide, with the highest levels of insecticide in bees passing by at 1 meter and decreasing in insecticide levels at greater distances.

                  The poisonous exhaust can account for the mass deaths of bees in sowing season from corn drillers that are used during this time. Although there were differences in levels of poisons in the bees, the majority of the bees that passed by the drilling machines in the way that bees normally forage were killed. The authors showed that, even with modified drillers or insecticides not affecting the bees directly, the airborne contaminants are extremely lethal to bees.

Effects of agricultural pesticides on the health of Rana pipiens frogs

The balance of natural ecosystems is almost certainly being disturbed by human modification of the natural environment. One such modification is the use of pesticides, which may leak into the surrounding soil and water and influence the surrounding ecosystems. Prior lab results have shown that pesticides could affect the health status of amphibians. To verify if similar results would be seen in natural populations, Cristin et al. (2013) sampled leopard frogs at three contaminated sites and two reference sites and used size, weight, spleen cellularity, phagocytic activity, and other measurements to examine the differences between frogs collected from contaminated sites and reference sites. The results of the study show that the juvenile frogs exposed to agripesticides are smaller in weight and length. It was also found that the number of active phagocytes, cells that protect the body by ingesting potentially harmful foreign particles and bacteria, was significantly reduced in exposed frogs. Thus pesticide use may inhibit amphibian growth and immune system response. —Kahea Kanuha

                  Christin, M.S., Menard, L., Girous, I., Marcogliese, D.J., Ruby, S., Cyr, D., Fournier, M., Brousseau, P. 2012. Effects of agricultural pesticides on the health of Rana pipiens frogs sampled from the field. Environmental Science and Pollution Research published ahead of print September 21, 2012, doi: 10.1007

                  Cristin et al. began by selecting five study sites: three contaminated sites and two reference sites along the tributaries of the St. Lawrence River in Monteregie, Quebec, Canada. The contaminated sites were directly adjacent to agricultural land and were therefore exposed to pesticide runoff. The reference sites included a conservation wetland and a wetland within a rural park, with managed landscape and human activity nearby. Pesticide concentrations were measured through collections of surface water samples. Repeated sampling was necessary since pesticide concentrations may fluctuate considerably with rain patterns and pesticide application time in the surrounding crop fields. For each site, temperature, conductivity, pH, and nitrate concentrations were recorded.
                  Juvenile R. pipiens were captured at the end of July and the beginning of September at each of the five sites. Overall health of the frogs was quantified through measurements of length and weight. The body index, or ratio of weight to length, was used rather than the measurements themselves in subsequent analyses.
To determine immune response impairment, the authors examined the viability of splenocytes, cellularity, and phagocytosis. Splenocytes are white blood cells produced in the spleen, and play an important role in immune system response. The spleen of each animal in the study was removed and cell suspensions were then prepared. Cellularity is the number and type of cells present in a given tissue. Viability, essentially the amount of living cells, was measured to ensure cell extraction methods were effective and that there were enough living cells to proceed with phagocytosis analysis. Both cellularity and splenocyte viability were determined microscopically after trypan blue dye exclusion, which stains dead cells blue.
Phagocytes are cells that ingest harmful foreign particles to protect the body and constitute the first line of defense against infectious microorganisms. Phagocytic activity of splenocytes was determined by introducing fluorescent bacteria to the spleen cells, incubating the cells, and then collecting the fluorescence emission. Higher fluorescence emissions indicate higher bacteria count and thus less phagocytic activity.
The results indicate that frogs living in sites exposed to pesticides runoff are smaller in length and weight
                  In both July and September, frogs living in agricultural regions had significantly lower body indices than frogs sampled in reference sites. In addition, there were no significant differences of body indices between the two reference sites. Spleen cellularity results show significant decreases in the number of splenocytes for frogs sampled in the three contaminated sites. However, in September one of the reference sites showed a number of splenocytes six times higher than the other reference site. Viability for all groups of frogs captured was over 70%, indicating the splenocyte suspensions were suitable to be used in the phagocytosis assay because there were enough living cells. The phagocytosis results for frogs sampled in July show a significant decrease in phagocyte numbers for four of the five contaminated sites. The September results show a significant decrease in two of the contaminated sites. In both months there was no significant difference between the reference sites.
                  It has already been observed that pollutants can reduce tadpole growth, but the exact way in which contaminants impair growth is not fully understood. Contaminated environments may hasten a tadpole’s metamorphosis in order to escape from a poor growing environment, which leads to a smaller size. However, the smaller size of frogs sampled from contaminated sites in this study may be due to other reasons, such as physiological effects of contaminants on growth or food limitation due to low food quality. The specific interactions between pesticides and the immune system also warrant further investigation in order to fully understand the impact of agricultural practices on aquatic systems.

This study has shown that juvenile frogs exposed to agripesticides are smaller and have compromised immune systems compared to frogs captured in reference sites. Further studies on almost all aspects of the relationship between agrochemicals and ecosystem response are necessary to more fully understand the complex consequences of human actions.

Agricultural Pesticide Use Decreases Species Richness in Stream Invertebrates

Despite years of scientific studies to guide regulation efforts, it is unknown to what degree agricultural pesticides cause species losses and thus a decrease in total biodiversity. To examine this relationship, Beketov et al. (2013) analyzed the effects of pesticides on taxa richness of stream invertebrates, using additional analyses to discriminate the possible confounding factors from the effects of pesticides. In all study sites it was shown that pesticide use caused a loss in species and family richness, indicating that pesticide use should be considered a main driver of regional biodiversity loss. —Kahea Kanuha
Beketov, M., Kefford, B., Schafer, R., Liess, M., 2013. Pesticides reduce regional biodiversity of stream invertebrates. Proceedings of the National Academy of Sciences 110, 11039—11043.

                  Beketov et al. applied the contaminant category richness to study the impacts of pesticide use on freshwater stream invertebrates. Contaminant category richness describes the taxa richness of stream invertebrates particular to different water contaminant levels, quantified by the relationship between the number of individuals and the number of taxa recorded. Data were used from Europe (33 sites) and Australia (18 sites) and included pesticide exposure assessment, stream invertebrate records, and data on environmental factors that may compound the effects of pesticides.
                  Study sites were assigned a contamination category based on toxic units (TUs) computed from the maximum pesticide concentrations at peak water runoff events. The contamination categories were then compared to the species and family richness of each respective study site. The Chao 2 richness estimator used the collected data to predict the species richness for an infinite number of samples taken at each site. Results show significant differences in taxonomic richness among all contamination categories. The percentage decrease in taxonomic richness between the uncontaminated and highly contaminated sites ranged from 27%, from the Australian family-level data, to 42%, for the European species-level data. Such an extensive decline is comparable to the effects of other known drivers of biodiversity loss. This indicates that for the goal of slowing biodiversity loss, safer standards should be set for pesticide use, methods, and mitigation practices.
                  Two methods were used to discern the possible effects of confounding factors from the effects of pesticide use. In the first, the SPEAR approach was used to identify the taxa that are particularly vulnerable to pesticides. After these taxa were identified, the data were checked to see whether the overall declines in taxa richness were based on the losses of taxa particularly vulnerable to pesticide use. As expected, it was found that pesticide contamination was associated with a decrease in the number of pesticide-vulnerable taxa. Secondly, available water quality and habitat variables were analyzed to see if any of them would explain the differences between contamination categories. The only significant difference found was in electrical conductivity between the slightly and heavily contaminated sites in Australia, but it was not a consistent linear trend and thus it is unlikely to be a major driver of the observed diversity patterns.

                  The effects of pesticide use on the taxa richness in Europe were identified in the contaminant concentration level that is considered to be protective by current European agricultural pesticides regulation. This indicates that current standards are not high enough to protect stream biodiversity. Agricultural pesticide use is predicted to increase in the coming decades due to the effects of climate change, and without more stringent regulation it may become an even more important driver of biodiversity loss in the future.