Genetics,Synergists, and Age Affect Insecticide Sensitivity of the Honey Bee,Apis mellifera

The number of honey bee colonies in the United States has declined to half of its peak level in the 1940s, and colonies lost over the winter have reached levels that are becoming economically unstable. While the causes of these losses are numerous and the interaction between them is very complex, the role of insecticides has garnered much attention. As a result, there is a need to better understand the risk of insecticides to bees, leading to more studies on both toxicity and exposure. While much research has been conducted on insecticides and bees, there have been very limited studies to elucidate the role that bee genotype and age has on the toxicity of these insecticides. The goal of this study was to determine if there are differences in insecticide sensitivity between honey bees of different genetic backgrounds (Carniolan, Italian, and Russian stocks) and assess if insecticide sensitivity varies with age. We found that Italian bees were the most sensitive of these stocks to insecticides, but variation was largely dependent on the class of insecticide tested. There were almost no differences in organophosphate bioassays between honey bee stocks (<1-fold), moderate differences in pyrethroid bioassays (1.5 to 3-fold), and dramatic differences in neonicotinoid bioassays (3.4 to 33.3-fold). Synergism bioassays with piperonyl butoxide, amitraz, and coumaphos showed increased phenothrin sensitivity in all stocks and also demonstrated further physiological differences between stocks. In addition, as bees aged, the sensitivity to phenothrin significantly decreased, but the sensitivity to naled significantly increased. These results demonstrate the variation arising from the genetic background and physiological transitions in honey bees as they age. This information can be used to determine risk assessment, as well as establishing baseline data for future comparisons to explain the variation in toxicity differences for honey bees reported in the literature.     

Assessing Risks of Plant-Based Pharmaceuticals: I. Human Dietary Exposure

Protein-based drugs are the fastest growing class of drugs for the treatment of disease in humans and other animals. However, the current method of producing proteins for pharmaceutical application is predicted to fall short because of population growth and demographic trends. This study characterized human dietary risks using quantitative risk assessment techniques for three pharmaceutical proteins produced in field-grown maize. The three proteins were aprotinin, gastric lipase, and Escherichia coli heat-labile enterotoxin B subunit (LT-B). The human dietary risks from the three proteins inadvertently occurring in food were evaluated using three different exposure scenarios so that potential risks could be compared. The three exposure scenarios ranged in conservatism to evaluate the range of risk between the proteins and scenarios. Risk quotients (RQs) were calculated for all three scenarios to integrate exposure and effect (toxicity). The risk assessments revealed that the most conservative scenario produced higher RQs than the other two scenarios. The dietary risks from scenario 1 for aprotinin were three orders of magnitude greater than for scenario 2, and four orders of magnitude greater than for scenario 3. This risk assessment revealed that dietary risks will vary dramatically and depend on factors such as the specific pharmaceutical protein, protein expression, and exposure scenarios. The assessment also reinforced the need for case-by-case assessments.     

In situ plankton community respiration measurements show low respiratory quotients in a eutrophic lake

Planktonic community respiration is an important carbon cycling process, typically quantified by converting measured values of dissolved O₂ consumption rates into CO₂ production rates assuming a respiratory quotient of 1 (RQ = CO₂ per O₂ by moles). However, the true variability in planktonic RQs between different aquatic ecosystems is poorly understood. We conducted in situ RQ measurements in a eutrophic lake dominated by algal-derived substances and found that RQs were significantly below 1. In fact, many RQ values were extremely low (0.2–0.6), below theoretical RQs for oxidation of algal organic matter substrates (0.7–0.8), suggesting that other factors than substrate control need to be considered to understand the RQ. This view was further supported by lack of correlations between RQ and microbial variables known to be strongly substrate dependent, including bacterial growth efficiency and the functional capacity of the bacterioplankton community to degrade different compounds. Based on the measured dynamics in methane and nutrient pools, we discuss that methane oxidation and nitrification likely occurred in the lake, contributing to the unusually low RQs. Our findings demonstrate that planktonic RQs in productive lakes can systematically be below 1, suggesting that CO₂ emissions from these lakes may currently be overestimated.     

Probabilistic Environmental Risk Assessment for Dibutylphthalate (DBP)

In the risk assessment methods for new and existing chemicals in the European Union (EU), environmental “risk” is characterized by the deterministic quotient of exposure and effects (PEC/PNEC). From a scientific viewpoint, the uncertainty in the risk quotient should be accounted for explicitly in the decision making, which can be done in a probabilistic risk framework. To demonstrate the feasibility and benefits of such a framework, a sample risk assessment for an existing chemical (dibutylphthalate, DBP) is presented in this paper. The example shows a probabilistic framework to be feasible with relatively little extra effort; such a framework also provides more relevant information. The deterministic risk quotients turned out to be worst cases at generally higher than the 95th percentile of the probability distributions. Sensitivity analysis proves to be a powerful tool in identifying the main sources of uncertainty and thus will be effective for efficient further testing. The distributions assigned to the assess ment factors (derivation of the PNEC) dominate the total uncertainty in the risk assessment; uncertainties in the release estimates come second. Large uncertainties are an inherent part of risk assessment that we have to deal with quantitatively. However, the most appropriate way to characterise effects and risks requires further attention. Recommendations for further study are identified.     

Field trials of spinosad as a replacement for naled, DDVP, and malathion in methyl eugenol and cue-lure bucket traps to attract and kill male oriental fruit flies and melon flies (Diptera: Tephritidae) in Hawaii

Spinosad was evaluated in Hawaii as a replacement for organophosphate insecticides (naled, dichlorvos [DDVP], and malathion) in methyl eugenol and cue-lure bucket traps to attract and kill oriental fruit fly, Bactrocera dorsalis Hendel, and melon fly, B. cucurbitae Coquillett, respectively. In the first and second methyl eugenol trials with B. dorsalis, naled was in the highest rated group for all evaluation periods (at 5, 10, 15, and 20 wk). Spinosad was equal to naled at 5 and 10 wk during both trials 1 and 2, and compared favorably with malathion during trial 2. During the first cue-lure trial with B. cucurbitae, naled and malathion were in the top rated group at 5, 10, 15, and 20 wk. Spinosad was equal to naled at 5 wk. During the second cue-lure trial, spinosad and naled were both in the top rated group at 10, 15, and 20 wk. Use of male lure traps with methyl eugenol or cue-lure had no effect on attraction of females into test areas. Our results suggest that spinosad, although not as persistent as naled or malathion, is safer to handle and a more environmentally friendly substitute for organophosphate insecticides in methyl eugenol and cue-lure traps for use in B. dorsalis and B. cucurbitae areawide integrated pest management programs in Hawaii.     

Effect of temperature on efficacy of insecticides to differential grasshopper (Orthoptera: Acrididae)

The effect of temperature on activity of insecticides for controlling grasshoppers in leafy green vegetables was evaluated. Insecticides evaluated had differing modes of action and included diflubenzuron, azadirachtin, Beauveria bassiana, spinosad, endosulfan, esfenvalerate, and naled. We evaluated these insecticides for efficacy to third instars of differential grasshopper, Melanoplus differentialis (Thomas), at temperatures ranging from 10 to 35 degrees C. In the laboratory, treatment with esfenvalerate resulted in 100% mortality at temperatures of 10 to 35 degrees C, and efficacy was not temperature dependent. Treatment with spinosad resulted in similar mortality as with esfenvalerate at all temperatures except 10 degrees C. The activity of B. bassiana was greatest at 25 degrees C and was adversely affected by high and low temperatures. Treatment with diflubenzuron resulted in increased mortality at high temperatures, and at 35 degrees C its activity was similar to that of esfenvalerate and spinosad. The activity of azadirachtin ranged from 19 to 31% and was not influenced by temperature. In field studies, spinosad, diflubenzuron, and esfenvalerate provided differing levels of mortality both at application and when nymphs were exposed to 1-h-old residues. However, only spinosad and diflubenzuron provided similar levels of mortality when nymphs were exposed to 24-h-old residues. The residual activity of endosulfan, naled, esfenvalerate, and spinosad decreased with increasing time (0-24 h) after exposure to sunlight and high summer temperatures. Compared with other insecticides, naled had a short residual activity period and activity was dependent upon immediate contact with the nymphs or their substrate. B. bassiana was inactive under high temperatures and intense sunlight as occurs in summer.     

Bayesian Updating of Model-Based Risk Estimates Using Imperfect Public Health Surveillance Data

Model-based estimation of the human health risks resulting from exposure to environmental contaminants can be an important tool for structuring public health policy. Due to uncertainties in the modeling process, the outcomes of these assessments are usually probabilistic representations of a range of possible risks. In some cases, health surveillance data are available for the assessment population over all or a subset of the risk projection period and this additional information can be used to augment the model-based estimates. We use a Bayesian approach to update model-based estimates of health risks based on available health outcome data. Updated uncertainty distributions for risk estimates are derived using Monte Carlo sampling, which allows flexibility to model realistic situations including measurement error in the observable outcomes. We illustrate the approach by using imperfect public health surveillance data on lung cancer deaths to update model-based lung cancer mortality risk estimates in a population exposed to ionizing radiation from a uranium processing facility.     

Application of a Probabilistic Risk Assessment Methodology to a Lead Smelter Site

Exposure of children to lead in the environment was assessed at the Murray Smelter Superfund site using both a deterministic risk assessment approach, the Integrated Exposure Uptake Biokinetic (IEUBK) model, and a probabilistic approach, the Integrated Stochastic Exposure (ISE) model. When site-specific data on lead in environmental media were input as point estimates into the IEUBK model, unacceptable risks were predicted for children living within five of eight study zones. The predicted soil cleanup goal was 550?ppm. Concentration and exposure data were then input into the ISE model as probability distribution functions and a one-dimensional Monte Carlo analysis (ID MCA) was run to predict the expected distribution of exposures and blood lead values. Uncertainty surrounding these predictions was examined in a two-dimensional Monte Carlo analysis (2-D MCA). The ISE model predicted risks that were in the same rank order as those predicted by the IEUBK model, although the probability estimates of exceeding a blood lead level of 10?µg/dl (referred to as the P10) from the ISE model were uniformly lower than those predicted by the IEUBK model. The 2-D MCA allowed evaluation of the confidence around each P10 level, and identified the main sources of both uncertainty and variability in exposure estimates. The ISE model suggested cleanup goals ranging from 1300 to 1500 ppm might be protective at this site.     

Magnitude and regulation of bacterioplankton respiratory quotient across freshwater environmental gradients

Bacterioplankton respiration (BR) may represent the largest single sink of organic carbon in the biosphere and constitutes an important driver of atmospheric carbon dioxide (CO₂) emissions from freshwaters. Complete understanding of BR is precluded by the fact that most studies need to assume a respiratory quotient (RQ; mole of CO₂ produced per mole of O₂ consumed) to calculate rates of BR. Many studies have, without clear support, assumed a fixed RQ around 1. Here we present 72 direct measurements of bacterioplankton RQ that we carried out in epilimnetic samples of 52 freshwater sites in Québec (Canada), using O₂ and CO₂ optic sensors. The RQs tended to converge around 1.2, but showed large variability (s.d.=0.45) and significant correlations with major gradients of ecosystem-level, substrate-level and bacterial community-level characteristics. Experiments with natural bacterioplankton using different single substrates suggested that RQ is intimately linked to the elemental composition of the respired compounds. RQs were on average low in net autotrophic systems, where bacteria likely were utilizing mainly reduced substrates, whereas we found evidence that the dominance of highly oxidized substrates, for example, organic acids formed by photo-chemical processes, led to high RQ in the more heterotrophic systems. Further, we suggest that BR contributes to a substantially larger share of freshwater CO₂ emissions than presently believed based on the assumption that RQ is ∼1. Our study demonstrates that bacterioplankton RQ is not only a practical aspect of BR determination, but also a major ecosystem state variable that provides unique information about aquatic ecosystem functioning.     

Evaluation of SPLAT with spinosad and methyl eugenol or cue-lure for "attract-and-kill" of oriental and melon fruit flies (Diptera: Tephritidae) in Hawaii

Specialized Pheromone and Lure Application Technology (SPLAT) methyl eugenol (ME) and cue-lure (C-L) "attract-and-kill" sprayable formulations containing spinosad were compared with other formulations under Hawaiian weather conditions against oriental fruit fly, Bactrocera dorsalis (Hendel), and melon fly, Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae), respectively. Field tests were conducted with three different dispensers (Min-U-Gel, Acti-Gel, and SPLAT) and two different insecticides (naled and spinosad). SPLAT ME with spinosad was equal in performance to the standard Min-U-Gel ME with naled formulation up to 12 wk. SPLAT C-L with spinosad was equal in performance to the standard Min-U-Gel C-L with naled formulation during weeks 7 to12, but not during weeks 1-6. In subsequent comparative trials, SPLAT ME + spinosad compared favorably with the current standard of Min-U-Gel ME + naled for up to 6 wk, and it was superior from weeks 7 to 12 in two separate tests conducted in a papaya (Carica papaya L.) orchard and a guava (Psidium guajava L.) orchard, respectively. In outdoor paired weathering tests (fresh versus weathered), C-L dispensers (SPLAT + spinosad, SPLAT + naled, and Min-U-Gel + naled) were effective up to 70 d. Weathered ME dispensers with SPLAT + spinosad compared favorably with SPLAT + naled and Min-U-Gel + naled, and they were equal to fresh dispensers for 21-28 d, depending on location. Our current studies indicate that SPLAT ME and SPLAT C-L sprayable attract-and-kill dispensers containing spinosad are a promising substitute for current liquid organophosphate insecticide formulations used for areawide suppression of B. dorsalis and B. cucurbitae in Hawaii.     

A Probabilistic Human Health Risk Assessment for Environmental Exposure to Dibutylphthalate

In the European Union, Directive 92/32/EC and EC Council Regulation (EC) 793/93 require the risk assessment of industrial chemicals. In this framework, it is agreed to characterise the level of “risk” by means of the deterministic quotient of exposure and effects parameters. Decision makers require that the uncertainty in the risk assessment be accounted for as explicitly as possible. Therefore, this paper intends to show the advantages and possibilities of a probabilistic human health risk assessment of an industrial chemical, dibutylphthalate (DBP). The risk assessment is based on non-cancer endpoints assumed to have a threshold for toxicity. This example risk assessment shows that a probabilistic risk assessment in the EU framework covering both the exposure and the effects assessment is feasible with currently available techniques. It shows the possibility of comparing the various uncertainties involved in a typical risk assessment, including the uncertainty in the exposure estimate, the uncertainty in the effect parameter, and the uncertainty in assessment factors used in the extrapolation from experimental animals to sensitive human beings. The analysis done did not confirm the reasonable worst-case character of the deterministic EU-assessment of DBP. Sensitivity analysis revealed the extrapolation procedure in the human effects assessment to be the main source of uncertainty. Since the probabilistic approach allows determination of the range of possible outcomes and their likelihood, it better informs both risk assessors and risk managers.     

Attraction and mortality of oriental fruit flies to SPLAT‐MAT‐methyl eugenol with spinosad†

Studies were conducted in 2007 and 2008 in Hawaii, USA to quantify attraction and feeding responses resulting in mortality of the male oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), to a novel male annihilation treatment (MAT) formulation consisting of specialized pheromone and lure application technology (SPLAT) in combination with methyl eugenol (ME) and spinosad (=SPLAT‐MAT‐ME with spinosad) in comparison with Min‐U‐Gel‐ME with naled (Dibrom). Our approach involved a novel behavioral methodology for evaluation of slow‐acting reduced‐risk insecticides. Methyl eugenol treatments were weathered for 1, 2, 4, and 8 weeks in California, USA, and shipped to Hawaii for bioassays. In field tests involving bucket traps to attract and capture wild males, and in toxicity studies conducted in 1 m³ cages using released males of controlled ages, SPLAT‐MAT‐ME with spinosad performed similar to or outperformed the standard formulation of Min‐U‐Gel‐ME with naled for material aged for up to 8 weeks in the 2008 tests. In laboratory feeding tests in which individual males were exposed for 5 min to the different ME treatments, mortality induced by SPLAT‐MAT‐ME with spinosad recorded at 24 h did not differ from that caused by Min‐U‐Gel ME with naled at 1, 2, and 4 weeks. Spinosad has low contact toxicity, and when mixed with SPLAT offers a reduced‐risk alternative for control of B. dorsalis, without many of the negative effects to humans and non‐targets of broad‐spectrum contact poisons such as naled. Our results indicate that SPLAT‐MAT‐ME with spinosad offers potential for control of males in an area‐wide integrated pest management (IPM) system without the need for conventional organophosphates.     

Effectiveness of attract-and-kill systems using methyl eugenol incorporated with neonicotinoid insecticides against the oriental fruit fly (Diptera: Tephritidae)

Laboratory bioassays and field trials were conducted to evaluate an "attract-and-kill" system using methyl eugenol (ME) with neonicotinoid insecticides against male oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae). In laboratory bioassays, mortality of male flies resulting from the conventional toxicant, naled was 98.3-100% at 24 through 72 h after treatment, whereas the neonicotinoid insecticides imidacloprid and acetamiprid caused only approximately 60-80% at 24 through 72 h after treatment. In the assays of residual effect, naled was persistent up to 96 wk, whereas imidacloprid or acetamiprid was persistent up to 150 wk, resulting in 38.9 or 61.2% male mortality, respectively. Imidacloprid, in particular, caused a delayed lethal effect on flies. In another experiment, male mortality within 28 wk from clothianidin, another neonicotinoid insecticide, was approximately 80% after exposure for 24 h, suggesting a delayed lethal effect similar to those treated with imidacloprid, and mortality was up to 91.8%, if observed, 72 h after treatment. In field trials, attractiveness was similar between ME alone and ME incorporated with naled or neonicotinoids, indicating that addition of these insecticides to ME in traps is not repellent to B. dorsalis males. Using an improved wick-typed trap with longer attractiveness for simulating field application, addition of imidacloprid or acetamiprid maintained 40.1 or 64.3% male mortality, respectively, when assayed once every 2 wk from traps placed in orchards for 42 wk without changing the poison, whereas incorporation with naled resulted in as high as 98.1% after 34 wk and approximately 80% at 42 wk, indicating that persistence is increased compared with sugarcane fiberboard blocks for carrying poison attractants. This study also suggests that neonicotinoid insecticides could be used as an alternative for broad-spectrum insecticides as toxicants in fly traps.     

Soil Cleanup Goal for Dioxin Using Probabilistic Risk Assessment Techniques

State regulators in Florida recently approved a first-of-its-kind probabilistic risk assessment (PRA) for determining an alternative residential Soil Cleanup Target Level (SCTL) for dioxin (32 ng/kg TEQ). The default residential SCTL (7 ng/kg TEQ) is based on a single, deterministic calculation with numerous conservative assumptions, resulting in an overly conservative value far beyond the regulatory mandate (i.e., 10^?6 increase in cancer risk). Conversely, this PRA used a Monte Carlo simulation to estimate risk for all members of a large population using a combination of scientific data and professional judgment, with final details developed during negotiations with regulators. The simulation parameters were defined probabilistically and reflect the ranges of values for the following exposure variables: body weight, exposure duration, exposure frequency, fraction from contaminated source, soil ingestion rate, and relative bioavailability. Other variable and uncertain parameters were treated deterministically per direction from the regulators. The state also required that a pre-supposed high-risk subpopulation be analyzed separate from the full receptor population. Despite the conservativeness of the alternative SCTL, this PRA represents a significant step toward more realistic estimates of human health risks caused by environmental contaminant exposure.     

On the respiratory quotient (RQ) of termites (Insecta: Isoptera)

The respiratory quotient (RQ) at 28 degrees C was determined by Warburg manometry in 23 species of termites from the Mbalmayo Forest Reserve (Cameroon) and three sub-tropical species cultured under laboratory conditions in the U.K. or freshly collected in Australia. The data are tabulated with other recently reported RQs (determined by manometry or GC) and with measured CH(4) emission rates to provide a survey of 29 species covering both lower and higher termites in all major trophic (functional) categories. In all species, except the wood-feeding Coptotermes acinaciformis and the soil-feeding Cubitermes fungifaber, the observed mean values (with manometry corrected for known fluxes of H(2) and CH(4)) were at or well above 1.00. Soil-feeding forms (except C. fungifaber) generally showed a high apparent RQ (not corrected for H(2)), with nine species (out of 13) above 1.20 and six species above 1.30. Well-replicated laboratory experiments with Reticulitermes lucifugus showed that there was a tendency for RQ to fall with time over a 4-h incubation, although remaining greater than 1.00.The observed RQs are consistent with carbohydrate being the principal substrate supporting respiration in all trophic and taxonomic categories, with little or no contribution from the degradation of lignin or other polyaromatic materials. However, in many species (especially soil-feeders), the observed RQ is greater than that expected from known fluxes of O(2), CO(2) and CH(4) on the assumption that carbohydrate is the respiratory substrate. This presupposes that there is a large hydrogen sink (additional to CH(4) production), possibly the emission of H(2) gas, and/or the existence of unresolved digestive mechanisms or electron routings. Uncertainties in the use of manometry with termites are discussed.     

Dietary exposure and risk assessment to cadmium of the adult population of Jiangsu province,China: Comparing between semi-probabilistic and fully probabilistic approaches

With rapid industrialization and modernization in China, long-term dietary exposure to cadmium (Cd) has the potential to cause health risks. The traditional probabilistic approach for long-term dietary assessment was a semi-probabilistic method that had limitations in qualifying the variation in concentration data. Thus, this article estimated the long-term dietary exposure to Cd of the adults of Jiangsu province using semi-probabilistic and fully probabilistic approaches, and compared the two models. Cd concentration data were obtained from the national food contamination monitoring program 2001–2009. Food consumption data were gathered from the National Diet and Nutrition Survey conducted in 2002. The provisional tolerable daily intakes (PTDI) of 0.8 μg kg^–1 bw for Cd was applied in the risk assessment. The estimates of semi-probabilistic approach were within the provisional tolerable daily intakes (PTDI) at mean and all percentiles. However, the P95 of exposure with fully probabilistic approach for all population groups were above PTDI. Rice and rice products followed by wheat flour and wheat flour products, crustaceans, pak-choi, beans, and bean products contributed most to the Cd intake for adults. The fully probabilistic estimates could indicate a possible public health concern on Cd for adults in Jiangsu province.     

Importance of dose‐response model form in probabilistic risk assessment: A case study of health effects from methylmercury in fish

We compared the effect of uncertainty in dose‐response model form on health risk estimates to the effect of uncertainty and variability in exposure. We used three different dose‐response models to characterize neurological effects in children exposed in utero to methylmercury, and applied these models to calculate risks to a native population exposed to potentially contaminated fish from a reservoir in British Columbia. Uncertainty in model form was explicitly incorporated into the risk estimates. The selection of dose‐response model strongly influenced both mean risk estimates and distributions of risk, and had a much greater impact than altering exposure distributions. We conclude that incorporating uncertainty in dose‐response model form is at least as important as accounting for variability and uncertainty in exposure parameters in probabilistic risk assessment.     

Probabilistic Analysis of Human Health Risks Associated with Background Concentrations of Inorganic Arsenic: Use of a Margin of Exposure Approach

Substantial evidence exists from epidemiological and mechanistic studies supporting a sublinear or threshold dose–response relationship for the carcinogenicity of ingested arsenic; nonetheless, current regulatory agency evaluations have quantified arsenic risks using default, generic risk assessment procedures that assume a linear, no-threshold dose–response relationship. The resulting slope factors predict risks from U.S. background arsenic exposures that exceed certain regulatory levels of concern, an outcome that presents challenges for risk communication and risk management decisions. To better reflect the available scientific evidence, this article presents the results of a Margin of Exposure (MOE) analysis to characterize risks associated with typical and high-end background exposures of the U.S. population to arsenic from food, water, and soil. MOE values were calculated by comparing a no-observable-adverse-effect-level (NOAEL) derived from the epidemiological literature with exposure estimates generated using a probabilistic (Monte Carlo) model. The plausibility and conservative nature of the exposure and risk estimates evaluated in this analysis are supported by sensitivity and uncertainty analyses and by comparing predicted urinary arsenic concentrations with empirical data. Using the more scientifically supported MOE approach, the analysis presented in this article indicates that typical and high-end background exposures to inorganic arsenic in U.S. populations do not present elevated risks of carcinogenicity.