The 2019 reassessment of the pesticide sulfoxaflor and, in particular, its impact on bees and other pollinators

1. Introduction

In 2011, the Rapporteur Member States of the EU (Ireland, with Czech Republic, Poland and France as co-rapporteurs) received an application from Dow AgroSciences for approval of the pesticide active substance sulfoxaflor. On this basis they provided an initial evaluation of the dossier on sulfoxaflor in a Draft Assessment Report (DAR) which was received by EFSA in November 2012. EFSA was required to conclude on whether this active substance can be expected to meet the approval criteria. EFSA conducted a public consultation on the DAR and provided comments. A final consultation on the conclusions arising from the peer review of the risk assessment and on the proposed maximum residue limits (“MRLs”) of sulfaxaflor took place with Member States via a written procedure in April 2014.

2. What is sulfoxaflor and what is it used for?

Sulfoxaflor is the ISO common name for [methyl(oxo){1-[6-(trifluoromethyl)-3-pyridyl]ethyl}-k6-sulfanylidene]cyanamide (IUPAC), a mixture of enantiomers² involving the S=N double bond and a cyano group

It is a non-flammable, not oxidising white powder with a sharp odour and with no impurities of toxicological, ecotoxicological and/or environmental concern.

In general pesticides are used on crops to protect them against insects and to maximise their yield. In the recent years, a specific class of insecticides, the neonicotinoids, was demonstrated to have negative impacts, in particular on pollinator insects, which led in many countries to a progressive ban of their uses except within greenhouse structures³.

These facts and subsequent trends have led to the development and registration of alternatives products, among which sulfoximine-based insecticides. Some of these, in particular sulfoxaflor were progressively registered in various regions, including the USA and the EU. It acts in a novel way on the central nervous system of insects, such as aphids which have developed resistance to other pesticides and targets the insect nicotinic acetylcholine receptor. It exhibits a high degree of efficacy against a wide range of sap-feeding insects, including those resistant to neonicotinoids and other insecticides.

However, since several years, there are some studies that reported that the sulfoximine insecticides could also represent a risk for pollinators. The representative uses assessed by the designated as Rapporteur Member State (RMS) were foliar spraying treatments on fruiting vegetables, spring and winter cereals and cotton to control sap feeding insects ⁴.

² In chemistry an enantiomer is composed of two molecules which are the mirror images of each other but non-superposable, such as the right hand and the left hand.
³ See the GreenFacts Highlights on: Neonicotinoids, bees, ecosystem services and agriculture
⁴ EFSA Report 2014 page 6 :”The representative uses evaluated comprise applications by foliar spraying to control sap feeding insects on fruiting vegetables, spring and winter cereals and cotton. Full details of the GAPs can be found in the list of endpoints in Appendix A.33 et aussi : Modification of existing MRLs for sulfoxaflor in various crops Assessment, page 7 :
https://efsa.onlinelibrary.wiley.com/doi/epdf/10.2903/j.efsa.2019.5587 

3. What are the conclusions of the EFSA reassessment of 2019 on the risks raised by sulfoxaflor used as a pesticide?

For the field and for non‐permanent structure greenhouses, a high risk to honeybees and bumble bees was identified related to some pertinent scenarios (treated crop scenario except after flowering period, weed scenario, field margin scenario). In case of permanent structure greenhouse, considering the low exposure in such scenarios, a low risk was concluded for honeybees, bumble bees and solitary bees.

These conclusions were reached on the basis of the evaluation of the representative uses of sulfoxaflor as an insecticide on fruiting vegetables (field and greenhouse application), cucurbits (field and greenhouse application), spring and winter cereals (field application), and cotton (field application).

The reliable endpoints that were considered appropriate for use in the regulatory risk assessment were derived from the studies and literature which are present in the dossier; they are described in the peer review.

4. How were these conclusions reached?

The conclusions of EFSA for the pesticide active substance sulfoxaflor followed the peer review of the initial risk assessment carried out by the competent authority of the Czech Republic, which was one of the co‐rapporteur Member State. The context of this peer review was a request by the European Commission following the submission and evaluation of confirmatory ecotoxicology data on this pesticide. Accordingly, the risk assessment for bees presented in the EFSA conclusion of 2014 (see reference above) has been amended due to the newly available studies.

The risk assessment included some novel refinement steps for which divergent views were expressed by Member States during the commenting phase. Different opinions were also expressed in relation to the interpretation and the use of the available higher tier studies and as regards the consideration of risk mitigation measures for the use of sulfoxaflor.

Following consideration of the technical report, the European Commission requested EFSA to adopt conclusions on all the points where disagreements were identified in the technical report and, where necessary, to organise a consultation of experts. The Commission also requested EFSA to take into consideration a recent publication related to the reproductive success of bumblebees following sulfoxaflor exposure.

5. What were the main elements of the previous 2014 EFSA risk assessment of sulfoxaflor?

The 2014 EFSA report evaluated several representative uses of sulfoxaflor as an insecticide on fruiting vegetables (field use and glasshouse application; including tomato, cherry tomato, pepper (bell and non-bell), aubergine, cucurbits (field use and glasshouse application; cucumber, water melon, courgette), spring and winter cereals (wheat, rye, barley, oats, triticale), and cotton as proposed by the applicant. Data were provided to confirm the efficacy of the active substance sulfoxaflor on various aphid species, when used as a single foliar application on solanacea, cucurbits, cereals and cotton, at the dose rate of 24 g/ha, as proposed under the representative uses evaluated.

5.1 Human toxicity

Sulfoxaflor is almost completely absorbed after oral administration and poorly metabolised; more than 93 % is rapidly excreted unchanged in urine and faeces. Sulfoxaflor is harmful if swallowed (with a subsequent labelling by the European Chemicals Agency (ECHA) “Xn; R22”). It is not acutely toxic via dermal route or after inhalation. It is neither a skin or eye irritant, nor a skin sensitiser. The liver is the main target organ after repeated oral administrations, either for short or long-term exposure. Overall, on the basis of the information available, ECHA concluded that sulfoxaflor should not be classified as carcinogen. Similarly, sulfoxaflor was not classified or proposed to be classified as toxic for reproduction and it was considered unlikely that sulfoxaflor is an endocrine disruptor in mammals.

Regarding decomposition products of sulfoxaflor, or ‘metabolites’, for the consumer risk assessment, at the time of the report it was assumed that the main metabolite present was as toxic as the parent compound, and the residue definition was therefore agreed as being the sum of sulfoxaflor with this metabolite (expressed as sulfoxaflor). However, only sulfoxaflor was considered for monitoring the animal residue. A consumer risk assessment was conducted for the uses for which a maximum residue limit (in food products) could effectively be proposed. Following the approach adopted, the toxicological reference values were not exceeded.

5.2 Eco-toxicity and potential environmental impact

On the basis of the available data and risk assessments, in 2014, a low acute and long-term dietary risk to birds from the representative uses of sulfoxaflor was concluded. Sulfoxaflor has some toxicity to lady beetles and is highly toxic to certain sap-sucking insects such as ants and, if they come into contact with spray droplets shortly after application, to bees, especially honey bees.

A low acute risk to wild mammals was also identified, however, a high long-term risk was indicated on the basis of the available first-tier risk assessments for the small herbivorous mammal scenario in vegetables (only for field uses) and cotton. On the basis of the available data and risk assessments, a low risk was also concluded for aquatic organisms, earthworms and other soil macro-organisms, soil microorganisms, non-target terrestrial plants and organisms involved in biological methods for sewage treatment.

Regarding endocrine effects, at the 2014 meeting, the experts concluded that although no specific concerns were identified from the available studies, no firm conclusion could be made, as in general, these studies alone were not sufficient to investigate all the relevant mechanisms and to detect all the adverse effects which could be caused by an endocrine mechanism of action.

In the 2014 risk assessment, the main data gaps identified concerned the risks to wild non-target terrestrial vertebrates and non-vertebrates.

5.3 The specific potential impact of sulfoxaflor on pollinator insects

Sufficient acute toxicity data on honeybees were available for the active substance and the representative formulations. The risk assessment indicated a high acute contact and acute oral risk to honeybees. In addition to the acute data, appropriate chronic data with the active substance were available for adult honeybees and larvae. Risk assessments data available for the pertinent metabolites indicated a low risk to honey bees.

A high risk to pollinators introduced in glasshouses where sulfoxaflor is used could not be excluded. Therefore, risk mitigation measures such as covering or removing bumble bee colonies for the application until the foliar residues have dried were proposed for these situations. However, the experts noted that some considerations to post-application exposure (as indicated by the results of the semi-field tests and the systemic properties of sulfoxaflor) needed to be taken into account. It was also noted by some experts that protection measures for the wild pollinators visiting the glasshouses should also be considered (e.g. by keeping the glasshouses closed).

Residue data that were available from four different crops indicated high initial residue levels in pollen and nectar. Nevertheless, it was acknowledged that the available data indicated a rather fast dissipation from pollen and nectar, and this information can be taken into consideration qualitatively. It was noted that long-term exposure of bees may not be expected because of the available information on the residue decline.

In the colony feeder study, five concentrations were selected and for each concentration, five colonies were tested. A 200 mL spiked sugar solution per day was offered to each of the free-flying colonies for 10 consecutive days. Overall, it was considered that a low risk could not be demonstrated in these studies.

A high risk was concluded for the situations when sulfoxaflor was used in flowering stage of the representative crops (even if it was an evening application). A low risk could be concluded for the situations when sulfoxaflor was used at least 5 days before the flowering period starts. Meanwhile, it was agreed that, overall, the studies and assessment that had been presented were not sufficient to demonstrate that a risk to honeybees can be excluded for applications made before the flowering period.

In the semi-field study, after an evening spray application, a statistically significant elevated adult mortality was observed on the first day after the application. Also, a clear pattern for sub-lethal effects (lower foraging activity, impaired locomotor activity) was observed, which was attributed to the treatment with sulfoxaflor. Both mortality and the sub-lethal effects were mainly observed on the day after the evening application. No significant impact on other parameters including the colony strengths was identified, and situations where flowering weeds were not present in the field would result in a low risk to bees.

In soil laboratory, after incubations under aerobic conditions in the dark, sulfoxaflor exhibited very low persistence. In another residue study simulating the exposure via contaminated soil of various crops (summer oilseed rape as test crop, at four sites in Germany), no residues were detected in pollen and nectar of the test crops. Relatively frequent guttation of summer oilseed rape occurred but practically no bees were observed collecting guttation liquid, and this route of exposure was deemed of low relevance.

In a greenhouse study where an evening spray application was performed on flowering tomato, the introduced bumble bee colonies were closed into their hives for more than a day after the spray application in order to decrease their potential exposure. No apparent effects were recorded on the foraging activity of the bumble bee colonies or on other parameters. However, the experts agreed that this study was not suitable for the risk assessment of wild (i.e. non-managed) bumble bees.

6. What is the present regulatory status of sulfoxaflor in the EU?

Sulfoxaflor was approved in accordance with Regulation (EC) No 1107/2009⁵, on 18 August 2015 by Commission Implementing Regulation (EU) No 2015/1295, amending the Annex to Commission Implementing Regulation (EU) No 540/2011.

Meanwhile, it was a specific provision of the approval that the applicant was required to submit by August 2017 to the European Commission further studies on:

• the risk to honey bees via the different routes of exposure, in particular nectar, pollen, guttation fluid and dust;
• risk to honey bees foraging in nectar or pollen in succeeding crops and flowering weeds;
• the risk to pollinators other than honey bees;
• the risk to bee brood.

In accordance with these specific provisions, the applicant, Dow AgroSciences, submitted an updated dossier to the rapporteur Member State (RMS) Ireland, in August 2017. For the standard risk assessment, the recommendations of EFSA Guidance on the risk assessment of plant protection products on bees (Apis mellifera, Bombus sp., and solitary bees) were applied by the applicant.

The updated dossier was evaluated by the designated co-rapporteur Member State (co-RMS), the Czech Republic, on behalf of the RMS Ireland, and expressed in the form of an addendum to the draft assessment report. EFSA added its scientific views on the specific points raised during the commenting phase, and finalised the related technical report in July 2018.

Meanwhile, there is no obligation on the European Commission to review the authorisations of uses for sulfoxaflor.

In April 2018, the Standing Committee on Plants, Animals, Food and Feed of the European Union, expanded a controversial ban on 3 neonocotinoids (clothianidin, imidacloprid and thiamethoxam) on the ground that they pose a threat to pollinators. Only the uses in greenhouses without contact with bees remain authorised.

⁵ REGULATION (EC) No 1107/2009 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 21 October 2009 concerning the placing of plant protection products on the market and repealing Council Directives 79/117/EEC and 91/414/EEC https://eur-lex.europa.eu/LexUriServ/LexUriServ.do 

7. What is the present regulatory status of sulfoxaflor in the USA?

Under the Federal Insecticide, Fungicide, and Rodenticide Act, the US Environmental Protection Agency (EPA) has authority to approve temporary emergency uses of pesticides, even those not officially approved, if the agency determines that it is needed to prevent the spread of an unexpected outbreak of crop-damaging insects, for example.

In September 2015, the 9th Circuit Court of Appeals concluded that the EPA violated federal law when it approved sulfoxaflor without reliable studies evaluating the impact the insecticide could have on honeybee colonies. The fact that the Court vacated EPA’s approval, meant that sulfoxaflor may not be used in the U.S.A. unless and until the EPA obtains the necessary information regarding impacts to honeybees and re-approves the insecticide in accordance with the law ⁶

Also in 2018, the EPA’s Office of the Inspector General released a report⁷ finding that the agency’s practice of routinely granting “emergency” approval for pesticides across millions of acres does not effectively measure risks to human health or the environment.

Insert: The main EPA’s Office of the Inspector General findings (September 2018)

Specifically, they found that the Office of Pesticide Programs (OPP) collects human health and environmental data through its emergency exemption application process, including the total acres affected, the proposed and actual quantities of the exempted pesticide applied, and the estimated economic losses. Yet, they found that the OPP does not use these data to support outcome-based performance measures that capture the scope of each exemption, or to measure the potential benefits or risks of each exemption.

The EPA’s Office of the Inspector General concluded that the OPP does not have outcome measures in place to determine whether the emergency exemption process protects human health and the environment. The OPP is missing key data management controls that would support its ability to manage its emergency exemption process. The OPP’s emergency exemption process also faces challenges regarding the collection and dissemination of reliable emergency exemption information. To mitigate these challenges, the OPP needs meaningful measures, better data management and consistent communication to increase the agency’s ability to manage its emergency exemption process.

Among their recommendations was:

1. To develop and implement applicable outcome-based performance measures to demonstrate the human health and environmental effects of the EPA’s emergency exemption decisions; 
2. To determine which application review performance target for emergency exemption applications the Office of Pesticide Programs plans to meet, and makes that target consistent between its Annual Performance Goal and its internal controls governing the emergency exemption process; 
3. To update and finalize the draft standard operating procedure that the Office of Pesticide Programs uses to guide the emergency exemption process;  
4. To develop formal emergency exemption application review procedures that detail specific data collection, management and reporting control steps, as well as procedures that require specific management controls for accurately and consistently updating the Office of Pesticide Programs Section 18 database. 

Despite this and the fact that the EPA itself considered this substance “very highly toxic” to bees, in 2018, through the so-called “emergency” approvals⁸, sulfoxaflor was granted a full registration on more than 16 million acres of crops known to attract bees, even if the EPA’s 2016 registration purportedly excluded its use in crops like cotton and sorghum that are known to be attractive to bees.

Further, in February 2019⁹, the EPA reported that of the 18 states where the approvals were granted for sorghum and cotton crops in 2018, 12 have given approvals for at least four consecutive years for the same “emergency”.

8. What is the regulatory status of sulfoxaflor in France?

According to the French Agency for food, environmental and occupational health and safety (ANSES), the advantages of sulfoxaflor over neonicotinoids are that it is not very persistent in soils and plants (1 to 4 days); it is less toxic to aquatic animals, and its degradation residues would not be toxic to pollinators.

However, in November 2017, relying on the precautionary principle, which is integrated in the Constitution in France, the Administrative Court of Nice ordered the suspension of the marketing authorization issued by ANSES to the insecticides containing sulfoxaflor, "until the substance of [their] legality is determined on the merits". This decision was confirmed by the “Conseil d’Etat”.

See the GreenFacts Highlights on: Neonicotinoids, bees, ecosystem services and agriculture

⁸ www.federalregister.gov/documents/2018/05/31/2018-11751/pesticide-emergency-exemptions-agency-decisions-and-state-and-federal-agency-crisis-declarations 
⁹ www.federalregister.gov/documents/2019/02/14/2019-02354/pesticide-emergency-exemptions-agency-decisions-and-state-and-federal-agency-crisis-declarations