Aerial spraying is cost-effective.

Its insecticidal properties have been known for more than 150 years; although the earliest mention of the Chrysanthemum flowers from which it originates comes from early Chinese history, where it is believed that the flower passed into Europe along the silk roads. 1 The term "pyrethrum" refers to the dried and powdered flower heads of a white-flowered, daisy-like plant. belonging to the Chrysanthemum genus. Pyrethrum's insecticidal properties were recognized in the middle of the 19th century, when an American named Jumticoff discovered that many Caucuses tribes used it for the control of body lice.' The earliest cultivation of pyrethrum, also called "Persian pyrethrum" or "Persian pow ders", was in the region of the Caucuses extending into Northern Persia. 2 The first Persian powders that were processed and commercialized in Europe in the 1820s were most likely prepared from a mixture of C. roseum and C. corneum. During and after 1876, these preparations were introduced into the USA, Japan, Africa and South America. 3 ,4 The superior insecticidal properties of C. cinerariaefolium were first discovered around 1845 and these species sub sequently supplanted previously cultivated species. Chrysanthemum cinerpr iaefolium is currently cultivated in the

Ultra-low-volume (ULV) aerosol applications of insecticides are used to manage high densities of adult mosquitoes. We used two-dimensional probabilistic risk assessment methodologies to evaluate three pyrethroid insecticides (phenothrin, resmethrin, and permethrin), pyrethrins, and two organophosphate insecticides (malathion and naled), applied by truck-mounted ULV sprayer. Piperonyl butoxide, a synergist commonly used in pyrethroid and pyrethrins formulations, was also assessed. The objective of our study was to evaluate probabilistically if a deterministic human-health risk assessment of mosquito insecticides was sufficiently conservative to protect human-health. Toddlers and infants were the highest risk groups while adult males were the lowest risk group assessed in this study. Total acute exposure ranged from 0.00003 to 0.0003 mg/kg day -1 for the chemicals and subgroups assessed examining inhalation, dermal, oral, and hand-to-mouth exposure. We used the risk quotient (RQ) method for our risk assessment, which is calculated by dividing the total potential exposure for each subgroup and chemical by its ingestion toxic endpoint value (RfD). Mean RQs ranged from 0.000004 to 0.034 for all subgroups and chemicals, with none exceeding the RQ level of concern. Naled had the highest RQs of any chemical assessed while PBO had the lowest. Sensitivity analysis demonstrated that the exposure from inhalation and deposition contributed the largest variance to the model output. Results support the findings of previous studies that the risks from adult mosquito management are most likely negligible, and that the human-health deterministic risk assessment is most likely sufficiently conservative.

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Abstract-The use of pyrethroid insecticides has increased substantially throughout the world over the past few decades as the use of organophorous, carbamate, and organochlorine insecticides is being phased out. Pyrethroids are the most common class of insecticides for ultralow-volume (ULV) aerosol applications used to manage high densities of adult mosquitoes. Pyrethroids are highly toxic to nontarget organisms such as certain aquatic organisms, and there have been concerns about the effect of applications of ULV insecticides on these organisms. To address the uncertainties associated with the risks of ULV applications and the contradictory findings of other ecological risk assessments, the authors performed a probabilistic aquatic ecological risk assessment for permethrin using actual environmental deposition on surfaces to estimate permethrin concentrations in water. The present study is the first ecological risk assessment for pyrethroids to quantitatively integrate the reduction in bioavailability resulting from the presence of dissolved organic matter. As part of the risk assessment, the authors incorporated a species sensitivity distribution to take into account the differences in toxicity for different species. The 95th percentile estimated concentration would result in less than 0.0001% of the potentially affected fraction of species reaching the lethal concentration that kills 50% of a population. The results of the present study are supported by the weight of evidence that pyrethroids applied by ground-based ULV equipment will not result in deleterious effects on aquatic organisms. Environ. Toxicol. Chem. 2013;32:948-953. # 2013 SETAC

One of the most effective ways of managing adult mosquitoes that vector human and animal pathogens is the use of ultra-low-volume (ULV) insecticides. Because of the lack of environmental fate studies and concerns about the safety of the insecticides used for the management of adult mosquitoes, we conducted an environmental fate study after truck-mounted applications of permethrin and naled. One hour after application, concentrations of permethrin on cotton dosimeters placed at ground level 25, 50, and 75 m from the spray source were 2, 4, and 1 ng/cm2 in 2007 and 5, 2, and 0.9 ng/cm2 in 2008, respectively. One hour after application, concentrations of naled 25, 50, and 75 m were 47, 66, and 67 ng/cm2 in 2007 and 15, 6.1, and 0 (nondetectable) ng/cm2 in 2008, respectively. Deposition concentrations 12 h after application were not significantly different than 1 h after application for permethrin and naled either year. During 2007 and 2008 permethrin applications, two quantifiable air concentrations of 375 and 397 ng/m3 were observed 1 h after application. In 2007 and 2008, naled air concentrations ranged from 2300 to 4000 ng/m3 1 h after application. There were no quantifiable air concentrations between 1 and 12 h after application in either 2007 or 2008 for both naled and permethrin. Environmental concentrations observed in this study demonstrate that models used in previous risk assessments were sufficiently conservative (i.e., the models overestimated environmental concentrations). However, we also demonstrate inadequacies of models such as AgDrift and AGDISP, which currently are used by the US Environmental Protection Agency to estimate environmental concentrations of ULV insecticides.

We derived laboratory LC50 values, assessed non-target insect risks, and conducted a field bioassay for ultra-low-volume (ULV) aerosol applications of insecticides used to manage adult mosquitoes. The house cricket, Acheta domesticus (L.), was used as an indicator species for medium- to large-bodied ground dwelling insects. The 24-h LC(50) values for Permanone (formulated product of permethrin), Permanone + piperonyl butoxide (PBO), technical grade permethrin, and technical grade permethrin + PBO ranged from 0.052 to 0.9 microg/cm(2). The 24 h LC(50) for technical grade naled and Trumpet((R)) (formulated product of naled) were 0.038 and 0.44 microg/cm(2), respectively. The synergist ratio was 2.65 for Permanone + PBO and 1.57 for technical grade permethrin + PBO. The toxicity of technical grade permethrin was about 10-fold greater than Permanone. A risk assessment using modeled estimated environmental concentrations resulted in risk quotients (RQ) that exceeded regulatory levels of concern, but when compared to field-derived actual environmental concentrations RQs did not exceed a regulatory level of concern, except in the case of technical grade naled. These results were expected because higher tiered risk assessments using field-verified data generally lead to lower risk estimates. Field bioassays using caged crickets showed no significant mortality for permethrin or naled after a single truck-mounted ULV application. The results of the risk assessment using actual environmental concentrations are supported by the field bioassays and suggest that a single ULV application of synergized or unsynergized permethrin and naled most likely will not result in population impacts on medium- to large-bodied insects.

Herbicide active ingredients, formulation type, ambient temperature, and humidity can influence volatility. A method was developed using volatility chambers to compare relative volatility of different synthetic auxin herbicide formulations in controlled environments. 2,4-D or dicamba acid vapors emanating after application were captured in air-sampling tubes at 24, 48, 72, and 96 h after herbicide application. The 2,4-D or dicamba was extracted from sample tubes and quantified using liquid chromatography and tandem mass spectrometry. Volatility from 2,4-D dimethylamine (DMA) was determined to be greater than that of 2,4-D choline in chambers where temperatures were held at 30 or 40 C and relative humidity (RH) was 20% or 50%. Air concentration of 2,4-D DMA was 0.399 µg m−3at 40 C and 20% RH compared with 0.005 µg m−3for 2,4-D choline at the same temperature and humidity at 24 h after application. Volatility from 2,4-D DMA and 2,4-D choline increased as temperature increased from 30 to 40 C. However, volatility from 2,4-D choline was lower than observed from 2,4-D DMA. Volatility from 2,4-D choline at 40 C increased from 0.00458 to 0.0263 µg m−3and from 0.00341 to 0.025 µg m−3when humidity increased from 20% to 50% at 72 and 96 h after treatment, respectively, whereas, volatility from 2,4-D DMA tended to be higher at 20% RH compared with 50% RH. Air concentration of dicamba diglycolamine was similar at all time points when measured at 40 C and 20% RH. By 96 h after treatment, there was a trend for lower air concentration of dicamba compared with earlier timings. This method using volatility chambers provided good repeatability with low variability across replications, experiments, and herbicides.