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Environ. Sci. Technol. 2006, 40, 2448-2454
New Risk Assessment Approach for
Quotient (HQ ) field application rate/oral or contact LethalDose (LD50)). When the calculated value of HQ is higher than Systemic Insecticides: The Case of
a threshold of 50, further studies are required. This thresholdis derived from data which only consider spray applications Honey Bees and Imidacloprid
(Gaucho)
In the case of plants treated by systemic insecticides, honey bees may be at risk via contaminated pollen and nectar(4). The contamination of nectar by sprayed systemic M A R I E - P I E R R E H A L M , * , † A . R O R T A I S , * , ‡ insecticides has been long documented (5), whereas little G . A R N O L D , ‡ J . N . T A S EÄ I , § A N D information is available on systemic formulations applied in soils and on seeds. Published data deal mainly with aldicarb,a carbamate substance used for the protection of various Centre d’Etude et de Recherche du Me´dicament deNormandie, 5 rue Vaubenard, 14032 Caen cedex, France, cultures (6). More recently, several authors supplied data on Laboratoire Evolution, Ge´nomes, Spe´ciation, CNRS-UPR9034, the presence of imidacloprid, a neonicotinoid systemic Baˆtiment 13, Avenue de la Terrasse, F-91198 Gif-sur-Yvette, insecticide, in nectar and pollen of treated plants (7).
France, and Laboratoire de Zoologie, INRA, Generally, systemic insecticides provide the treated plant with a permanent protection from soil invertebrates andsucking insects (8). Applied in soils and on seeds, they degradeslowly over time and disperse in all the plant tissues duringits growth. Therefore, using the field application rate of active The procedure to assess the risk posed by systemic substance as an exposure parameter to assess the risk posed insecticides to honey bees follows the European Directives by systemic insecticides to honey bees is not sensible. Unlike and depends on the determination of the Hazard Quotient sprayed insecticides, which have a short-lasting action on (HQ), though this parameter is not adapted to these plants, systemic insecticides are persistent. Moreover, thesemolecules, detected at low concentrations in the pollen and molecules. This paper describes a new approach to assess nectar of treated plants, are more likely to affect honey bees more specifically the risk posed by systemic insecticides by acute, chronic, and sublethal intoxications (9) rather than to honey bees with the example of imidacloprid (Gaucho).
This approach is based on the new and existing chemical In this paper, we propose a new approach to determine substances Directive in which levels of exposure (PEC, the risk posed by systemic insecticides to honey bees. It is Predicted Exposure Concentration) and toxicity (PNEC, based on the European Technical Guidance Directive (TGD) Predicted No Effect Concentration) are compared. PECs that assesses the impact of new (793/93 and 1488/94/CE are determined for different categories of honey bees in legislations) and existing chemical substances (EC-67/54/8 relation to the amounts of contaminated pollen and nectar and EEC-93/67 Directives) on ecosystems (10). This approach they might consume. PNECs are calculated from data on is applied to imidacloprid, which is a good study case because acute, chronic, and sublethal toxicities of imidacloprid to it has been extensively studied and presents a lot ofexperimental data.
honey bees, to which selected assessment factors areapplied. Results highlight a risk for all categories of honey Materials and Methods
bees, in particular for hive bees. These data are discussed A group of experts, namely the Scientific and Technical in the light of field observations made on honey bee Committee (CST), was nominated in 2001 by the French mortalities and disappearances. New perspectives are Ministry of Agriculture to assess the risk posed by imida- given to better determine the risk posed by systemic cloprid to honey bees. This committee examined all studies, delivered up to July 2004 by the Ministry of Agriculture, onthe toxicity of imidacloprid to honey bees (7). This paper Introduction
refers to some of the work achieved by this committee.
In the European Union, formulated pesticides are registered For many wildlife species, the standard practice in by the European Council Directive (EC-91/414) and the risk pesticide regulation (91/414 EEC) is to determine a toxicity posed by these molecules to honey bees is directly assessed exposure ratio (TER) and to compare it to a threshold (a by the European and Mediterranean Plant Protection safety factor) that aims at protecting these species. In this Organization (EPPO) guidelines No. 170 (1). These guidelines paper, we used the PEC/PNEC ratio (predicted environmental propose methods for evaluating side effects of agrochemical concentration/predicted no effect concentration) which aims products on honey bees. The approach is based on a 3 tier at protecting ecosystems (10). Honey bees (unlike most other assessment scheme comprising early studies in laboratory species) live in colonies and depend on each other for survival.
conditions, followed by semi-field studies, and completed Such interdependent relationships define the honey bees’ by field studies. According to this Directive, and to the colony as a superorganism (11). The functioning of a decision making scheme attached to the EPPO guidelines superorganism is similar to that of an ecosystem in the sense (2), moving from tier 1 (laboratory studies) to tier 2 (semi- that each unit (temporal castes in a colony and species in field studies) depends on a trigger criterion, the Hazard an ecosystem) is essential to sustain the system as a whole(12). Moreover, considering their role as pollinators (13), * Corresponding authors. Phone: (33/0) 2 31 56 59 10 (M.-P.H.), honey bees represent a good model to assess the risk of (33/0-1) 69 82 37 17 (A.R.); fax: (33/0) 2 31 93 11 88 (M.-P.H.), insecticides to pollinators and to protect many plant species (33/0-1) 69 82 37 36 (A.R.); e- mail: [email protected] or that rely on these organisms, through pollination, to repro- Centre d’Etude et de Recherche du Me´dicament de Normandie.
‡ Laboratoire Evolution, Ge´nomes, Spe´ciation, CNRS.
According to the PEC/PNEC approach and with the example of imidacloprid, we determined PECs with the 2448 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 40, NO. 7, 2006
TABLE 1. Estimated PECs for Different Categories of Honey Bees to Imidacloprida
imidacloprid
imidacloprid
imidacloprid
imidacloprid
imidacloprid
categories of bees
a Estimated amounts of food (sugar and pollen in mg) and imidacloprid (in pg) consumed per bee over d days, with different levels of food contamination (%). b Data from ref 21. c N. A.: No available data.
known concentrations of imidacloprid found in the con- bees. Nevertheless, a few studies have investigated the impact taminated pollens (sunflower and maize) and nectar (sun- of imidacloprid on honey bees by chronic and sublethal flower) consumed by honey bees, and we determined PNECs intoxications in laboratory, semi-field, and field conditions.
with the data derived from studies on acute, chronic, and To assess these studies, we referred to the EPPO guidelines sublethal toxicities of imidacloprid to honeybees.
because they present guidelines for semi-field and field Criteria for the Validation of Data. To determine the
concentration of imidacloprid in pollens and nectar issued PEC Estimates. By definition, a PEC corresponds to the
from imidacloprid seed-dressed plants and the honey bees’ amount of pesticides a honey bee might be exposed to, either exposure to imidacloprid, the CST validated the data of all by ingestion or contact. In this paper, with the example of the studies that met the following requirements in terms of imidacloprid and honey bees, we only considered oral sampling procedure, chemical analyses, and toxicity testing.
exposures because data on topical exposures are scant.
For the sampling procedure, studies needed to describe We can estimate honey bees’ exposure to both contami- thoroughly the methods used (sampling location, pesticide nated pollens (sunflower and maize) and nectar (sunflower) treatments history) and gather sufficient samples, both with (i) the known and validated concentrations of imida- qualitatively and quantitatively. Qualitatively, data obtained cloprid found in contaminated pollens and nectars, and (ii) from pollens collected directly on anthers of treated flowers, the amount of contaminated pollen and nectar consumed rather than in pollen traps, were kept and validated because by different categories of honey bees (21).
the concentration of imidacloprid in pollens of traps is highly (i) The amount of imidacloprid present in the food of variable and depends on the environment (i.e., the amount honey bees is directly related to the environement. For of plants treated by systemic insecticides) (14). Quantitatively, example, if a hive is located near extensive cultures of maize the CST retained the value of a minimum of 10 samples to and sunflower plants treated by imidacloprid, the proportions enable statistics (means and standard deviations). Samples of pollen and/or nectar that might be contaminated by coming from different experiments and locations, but imidacloprid are expected to be high. Since the relative presenting similar protocols, were grouped together to get proportions of contaminated food, versus uncontaminated food, consumed by honey bees are unknown, we considered For the chemical analyses, given the high toxicity of 5 different levels of contamination ranging from 20% (a low imidacloprid, we validated studies that detected the molecule level of contamination) to 100% (the highest level of the most accurately as possible, that is by high performance contamination) (Table 1), although the latter case might rarely liquid chromatography (HPLC) coupled to mass spectrometry (MS) (15) and using an appropriate limit of quantification (ii) The amount of contaminated food consumed by (LOQ ) 1 µg/kg), limit of detection (LOD < 0.5µg/kg), and different categories of honey bees depends on the amount sample weight (10 g). The only study that used a radioactivity of food the bees require to achieve particular tasks within method coupled with thin-layer chromatography (TLC) and the colony. Among them, Rortais et al. (21) considered the automated multiple development (AMD) techniques (16) was categories that are potentially the most exposed to imida- validated too because it allowed a clear identification of cloprid: those that achieve the most costly tasks in terms of imidacloprid, unlike less specific methods such as the energy and which consume the highest amounts of pollen derivation and gas chromatography (GC) (17, 18).
for their development. Therefore, for the calculation of the To determine the toxicity of imidacloprid to honey bees, PEC, the following categories of honey bees were consid- studies apply standardized tests designed by the OECD ered: the worker larvae which consume pollen and nectar guidelines (19, 20). Such tests are developed in laboratory for their development over about 5 days; the drone larvae conditions to assess oral (19) and topical (20) acute toxicities which consume pollen and nectar for their development over of pesticides (and other chemicals) to adult worker honey about 6.5 days; the nurses which consume pollen over a bees. These laboratory tests follow the EPPO guidelines No.
period of 10 days and nectar and/or honey to maintain the 170 (1) and the recommendations made by the International nest temperature at 34 °C over the entire brood attendance Commission for Plant-Bee Relationships (ICPBR). While period, lasting about 8 days; the wax-producing bees which these guidelines propose methods to test oral and topical consume nectar during the period of maximum wax pro- acute toxicities, there are currently no standardized tests to duction, lasting about 6 days; the winter bees which consume study chronic and sublethal toxicities of pesticides to honey nectar and honey to maintain the nest temperature at viable VOL. 40, NO. 7, 2006 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 2449
temperature during winter, lasting about 90 days in temperate additional long-term toxicity tests of two or three trophic regions; and the nectar and pollen foragers which consume levels of known NOEC, the factors 50 and 10, respectively, nectar and/or honey to cover their daily flight expenses. As are selected. In field conditions, an assessment factor is a forager life span is highly variable (between 1 and 3 weeks), determined case by case (10).
the amount of food consumed by a forager to collect food The approach presented in this paper consisted in finding has been estimated over a minimal period of one week.
appropriate PNECs for honey bees derived from PNECs Honey Bees’ Exposure to Contaminated Sunflower and/or designed for ecosystems. These PNEC values were estimated Maize Pollens. The honey bee’s exposure to contaminated with the available data obtained from studies on oral acute, pollens collected on treated plants is determined by the chronic, and sublethal toxicities of imidacloprid to honey bees. These values were derived from the lowest validatedtoxicities (LD50, lowest observed effect concentration (LOEC), PEC (pg) ) Validated concentration of imidacloprid found or no observed effect concentration (NOEC)) to which in sunflower and/or maize pollens (µg/kg) × assessment factors are applied. This new approach is Amount of pollens consumed by honey bees (mg) × specifically adapted to honey bees because it allows the Levels of contamination found in pollen (%) assessment of both colonies and individuals. These factorshad to be determined case by case, following the standard Honey Bees’ Exposure to Contaminated Sunflower Nectar. approach used by the TGD. Every time new data enabled us The nectar brought back to the colony is consumed by honey to reduce extrapolations (chronic toxicity data in relation to bees, either rapidly as it is or later on as honey when it is acute toxicity data), the assessment factors were generally stored. The relative amounts of nectar and honey consumed by honey bees are unknown. However, the amounts of sugar PEC/PNEC Estimates. The hazard posed by new sub-
contained in sunflower honey and nectar are known and stances to organisms is determined by the PEC/PNEC ratio.
are, on average, 80% and 59%, respectively (22, 23). Therefore, When this ratio is over 1, it highlights an intoxication risk for the amounts of sunflower nectar and/or honey consumed honey bees, whereas when it is below 1, it indicates no risk.
by honey bees can be determined by their sugar consumption, According to the TGD (10), this ratio is obtained and derived in relation to their energy requirement (21). As a result, for from acute toxicity data, but when a risk is found, the ratio every milligram of sugar required, a honey bee will have to is re-calibrated with new data obtained in more representative consume 1.25 mg of sunflower honey or 1.69 mg of sunflower conditions. For honey bees, the PECs were determined with nectar. Therefore, a honey bee’s exposure to contaminated all the available scientific data found on honey bees’ food sunflower nectar can be determined by the following consumptions because there were sufficient data, whereas the PNECs required more data. Therefore, following the TGDprocedure, PNECs were derived from acute toxicity data.
PEC (pg) ) Validated concentration of imidacloprid When a risk was highlighted, a new PEC/PNEC ratio was found in sunflower nectar (µg/kg) × Amount of sugar determined with data obtained from chronic toxicity studies.
consumed by honey bees (mg) × 1.69 Levels of If the new ratio remained over 1, a final PEC/PNEC ratio was contamination found in sunflower nectar (%) then calculated with new data coming from sublethal fieldtoxicity studies. This final ratio is the most representative Honey Bees’ Exposure to Contaminated Sunflower and/or ratio of the natural conditions of a honey bees’ colony.
Maize Pollens and to Contaminated Sunflower Nectar. Thehoney bee’s exposure to contaminated sunflower and/or maize pollens and to contaminated sunflower nectar is PEC Estimates. (i) In pollen collected directly on the anthers
of flowers, the concentrations of imidacloprid found in treatedsunflower and maize plants are 3.3 and 3.5 µg/kg, respectively (24, 25), or on average 3.4 µg/kg for both pollen types. Theconcentration of imidacloprid found in treated sunflower PNEC Estimates. By definition, a PNEC corresponds to
nectar is 1.9 µg/kg (25). (ii) Based on the estimated amounts the amount of substances that will have no impact on of pollen and nectar consumed by honey bees over several ecosystems. For numerous substances, the pool of data is days of activity (21), the potential amounts of imidacloprid usually too limited to predict their effects on ecosystems. In ingested by honey bees were determined (Table 1).
such circumstances, empirically derived assessment factors PNEC Estimates. There is currently no test and no toxicity
must be applied. These assessment factors allow the predic- data for larvae. For this category of honey bees, PNECs were tion of a concentration below which an unacceptable effect derived from the toxicity data obtained in adult workers.
will most likely not occur. The size of these assessment factors Table 2 shows the PNECs determined in adults and derived incorporates various uncertainties due to extrapolations from from acute, chronic, and sublethal toxicity data, to which single-species laboratory data to a multi-species ecosystem, specific assessment factors were applied.
in particular uncertainties due to intra- and inter-laboratory From acute toxicity data: the lowest validated LD50 (48 variations in toxicity data, intra- and inter-species variations, h) is 3.7 ng of imidacloprid per bee (26). According to the short-term to long-term toxicity extrapolations, and from TGD (10), the assessment factor for acute toxicity data is laboratory data to field impact studies. For the terrestrial 1000. However, the toxicity of imidacloprid was determined compartment, the size of the assessment factors depends on by several studies which tested models belonging to the same the confidence we have on the representativeness of the species, and found similar results. As these data present very toxicity data. For example, the size of these factors is reduced few uncertainties, an assessment factor of 100 was applied.
when more data become available at various trophic levels Therefore, the validated PNEC becomes 3.7/100 ) 37 pg/ Based on these parameters and in relation to the From Chronic Toxicity Data. In laboratory conditions, the experimental conditions, the TGD determines various as- lowest validated value was LD50 (10 d) ) 0.012 ng/bee (27).
sessment factors. In laboratory conditions, for short-term As this value was obtained from a long-term experiment, it toxicity tests (LD50) and for one trophic level, a factor 1000 seemed appropriate to apply the same assessment factor as is used, for long-term toxicity tests and for several trophic the one used for a long-term NOEC experiment, which is 100 levels with known NOEC, a factor 100 is applied, and for (10). However, this factor is used to determine a PNEC for 2450 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 40, NO. 7, 2006
TABLE 2. PNECs for Oral intoxications of Honey Bees to Imidacloprid
experimental conditions
assessment
toxicities
(imidacloprid intakes)
doses (ng/bee)
observed variables
(pg/bee)
a Feeders contained syrup contaminated by imidacloprid. In field conditions, feeders were placed near hives to reinforce the observed effects of imidacloprid seed-dressed plants on honey bees.
all the taxonomic groups of an ecosystem. To adjust this and greater in adult hive bees than in any other categories factor to one taxonomic group (the honey bees), we applied of bees. Whatever the validated toxicity data are, the a factor 10. This factor includes all variations found among determined PNECs are in a limited range of values (between and within taxonomic groups (inter- and intra-species 1.2 and 50 pg/bee). These estimates are in agreement with variations). Therefore, the validated PNEC becomes 0.012/ observations made in regions of extensive sunflower and maize cultures, which report a decrease in honey production From Sublethal Toxicity Data. In laboratory, semi-field, since the launching of imidacloprid on sunflower plants in and field conditions, one or several administered doses might 1994 (32), and several behavioral dysfunctions, foragers induce behavioral modifications among treated honey bees.
disappearances, and great honey bee mortalities in summer, When administering a unique oral dose of imidacloprid to during the blossoming of maize and sunflower plants, and honey bees for the testing of the knockdown effect, the lowest after winter, when all sunflower and maize pollens have been validated NOEC was 0.94 ng/bee (28). As this value was obtained from a short-term experiment, an assessment factor In areas of extensive sunflower and maize cultures treated of 100 should have been applied (TGD). However, this value by imidacloprid, all categories of honey bees, whatever their does not correspond to a LD50; it is a dose that has no impact age is, are at risk of intoxication. In such a situation, honey on honey bees. Moreover, the measured effect is a sublethal bees are most likely to bring back food that is contaminated effect. Therefore, we applied an assessment factor of 50. The by imidacloprid, and the observed effects might relate to validated PNEC becomes 0.94/50 ) 18.8 pg/bee. When either acute, chronic, or sublethal intoxications, all inducing administering several oral doses of imidacloprid to honey bees for the testing of the proboscis extension reflex (PER),the lowest validated concentration, after a 10 day experiment, In areas where sunflower and maize cultures treated by was 0.2 ng/bee (29). This value corresponds to a NOEC based imidacloprid are less abundant, honey bees might be less on the testing of sublethal effects after a long-term intoxica- intoxicated because they might consume a mixture of tion. Therefore, we applied an assessment factor of 10. The contaminated and uncontaminated food. In this situation, validated PNEC becomes 0.2/10 ) 20 pg/bee.
honey bees are most likely to be intoxicated by sublethal In semi-field conditions, a LOEC (5 d) of 0.075 ng/bee doses, rather than by acute or chronic doses, which might was validated for the testing of the time spent feeding on have lethal consequences at the individual and colony levels.
contaminated syrup (30). As this study was conducted in the At sublethal doses, pesticides are known to have profound natural conditions of foragers, an assessment factor of 10 impacts on the colony, in particular on the honey bees’ was applied (TGD, 10). The validated PNEC becomes 0.075/ longevity (34), the brood production (35, 36), the development of hypopharyngeal glands (37), and the egg laying (38).
In field conditions, a lowest NOEC (10 d) of 0.25 ng/bee Imidacloprid is known to affect the honey bees’ cognitive was validated for the testing of dances (31). Studies conducted behaviors such as the proboscis extension reflex PER (33).
in field conditions present similar conditions to those found Learning and memorization in honey bees’ tasks are very in the natural environment of honey bees. Therefore, an important. For example, a forager that is disorientated might assessment factor of 1 should be applied (TGD, 10), but we get lost and eventually die. In the case of massive foragers’ selected an assessment factor of 5 because the setting of the intoxications, the colony is likely to be greatly affected. In an feeders is artificial. Therefore, the validated PNEC becomes experiment under tunnels, Vandame et al. (39) exposed honey bees to deltamethrin at a sublethal dose that is 20-fold lower PEC/PNEC Estimates. According to the previously defined
than the registered dose at which foragers are expected to assessment factors, and whatever the level of food contami- be exposed to in the environment. They found that 54% of nation is, all the investigated categories of honey bees the treated bees were disoriented and took flight toward the presented an intoxication risk to imidacloprid (Figure 1).
sun. The authors concluded that such sublethal effects may The PEC/PNEC ratio was the highest for winter bees and be the cause of the symptom called the “disappearance bee nurses (between 10 and 100) and the lowest for pollen foragers disease” by beekeepers who observed colonies’ weakening without finding dead bees close to the hives. This hypothesiswas formerly raised by other scientists (40, 41).
Discussion
Imidacloprid can also affect honey bees by chronic The PEC/PNEC derived from the calculation of honey bees’ intoxications. In the long run, a repeated ingestion of low exposure to which appropriate assessment factors were doses of imidacloprid could cause immunodeficiency and applied show that the risk posed by imidacloprid is alarming diseases in honey bees. The impairment of the bees’ for all categories of honey bees. These ratios are all over 1, immunity system is a nonspecific mechanism (42). For VOL. 40, NO. 7, 2006 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 2451
FIGURE 1. Hazard posed by imidacloprid to different categories of honey bees feeding on various proportions of contaminated food:
estimated PEC/PNEC ratios derived from (A) acute toxicity data, (B) chronic toxicity data, and (C) sublethal toxicity data obtained in field
conditions for foragers and in laboratory conditions for all the other categories of honey bees (a risk is highlighted when ratios are greater
than 1).
example, sublethal concentrations of malathion result in In some cases, no honey bee troubles were observed by higher invasions of treated colonies by the wax moth (43).
beekeepers, but no scientific study has ever confirmed these 2452 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 40, NO. 7, 2006
observations. The presence of untreated or very little treated impacts of systemic insecticides on honey bees (9, 49, 50), areas near hives, and the presence of compensatory phe- as well as their sublethal effects on the behavior (41, 47, nomena (increase of brood development, replacement of 51-53) and physiology (38, 54, 55) of these organisms.
dead foragers) with no visible harmful consequences for the Based on the risk assessment method used for terrestrial colony may occur and explain the absence of any observed organisms, this method is original. It includes the assessment of several important parameters such as the following: (i) When assessing the risk posed by systemic insecticides, The detection and measurement of the amount of an active the HQ does not take into account several idiosyncrasic ingredient present in the various substrates used by honey parameters such as persistence in soils, presence in pollen bees. These measures are not statutorily requested. (ii) The and nectar, and transport in the air. The calculation of the development of various scenarios of honey bees’ exposure Toxicity Exposure Ratios (TER) (ratio between a toxicological to the active ingredient. These scenarios better predict the end point and a PEC), regularly used in the risk assessment risk posed by systemic insecticides to honey bees because of pesticides to organisms (mainly vertebrates and nematods), they take into account the biology and particular require- could take into account such crucial parameters. However, ments of a honey bees’colony (21). (iii) The use of novel and for social invertebrates such as honey bees, the use of the validated methods for the assessment of lethal and sublethal new and existing chemical substances approach (herein the honey bees’ intoxications. (iv) The use of assessment factors, PEC/PNEC ratio) should be more appropriate than the use when experimental designs are tightly related to environ- of the TER because it enables the protection of the whole mental conditions. This approach is usually applied to assess colony. The PEC/PNEC ratio could then be re-calibrated when more data on imidacloprid and on other systemic insecticidesare available.
Acknowledgments
For hive bees (nurses and winter bees), the PNECs could Authors M.P.H. and A.R. contributed equally to this work.
be refined when more data are available on the mechanisms The validation of the data used in this study on imidacloprid of a colony’s regulation (e.g., brood development) in field was realized in concert with a group of experts nominated and semi-field conditions. For larvae, exposures were derived by the French Ministry of Agriculture and known as the from data obtained on adult toxicities in order to obtain an “Comite´ Scientifique et Technique (CST) de l’Etude multi- indicative and comparative value. Given that larvae are more factorielle des troubles des abeilles”. M.P.H. and A.R. were or less sensitive than adults to chemicals (4, 44), more studies financed by the French Ministry of Agriculture to give need to determine accurately their exposure risk to imida- cloprid and to other systemic insecticides.
We could not investigate topical exposures of imidacloprid Note Added after ASAP Publication
to honey bees because there are not enough data available An incorrect reference was cited in Table 1 in the version on this mode of exposure. However, honey bees’ intoxications published ASAP March 7, 2006; the corrected version was by topical exposures should not be discarded. For examples, foragers might get contaminated by contaminated dustparticles during sowing operations (45).
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