Are organosilicon surfactants safe for bees or humans?

Organosilicon surfactants are the most potent adjuvants available for formulating and applying agricultural pesticides and fertilizers, household cleaning and personal care products, dental impressions and medicines. Risk assessment of pesticides, drugs or personal care products that takes into account only active ingredients without the other formulation ingredients and adjuvants commonly used in their application will miss important toxicity outcomes detrimental to non-target species including pollinators and humans. Over a billion pounds of organosilicon surfactants from all uses are produced globally per year, making this a major component of the chemical landscape to which bees and humans are exposed. These silicones, like most "inerts", are generally recognized as safe, have no mandated tolerances, and their residues are largely unmonitored. Lack of their public disclosure and adequate analytical methods constrains evaluation of their risk. Organosilicon surfactants, the most super-spreading and -penetrating adjuvants available, at relevant exposure levels impair honey bee learning, are acutely toxic, and in combination with bee viruses cause synergistic mortality. Organosilicon surfactants need to be regulated as a separate class of "inerts" from the more common silicones. In turn, impacts of organosilicon surfactant exposures on humans need to be evaluated. Silicones in their great diversity probably represent the single most ubiquitous environmental class of global synthetic pollutants. Do honey bees, a model environmental indicator organism, forewarn of hidden risks to humans of ubiquitous silicone exposures?

Field Residues and Effects of the Insect Growth Regulator Novaluron and Its Major Co-Formulant N-Methyl-2-Pyrrolidone on Honey Bee Reproduction and Development.

Owing to the recent declines in honey bee (Apis mellifera L.) populations, there is a need for field and laboratory studies to investigate threats to pollinator health. This study examines the hypothesis that the organophosphate alternative, Rimon 0.83EC, can have consequences to honey bee health by combining newly acquired field residue data, laboratory bioassays, and colony level feeding studies. Following label rate applications of Rimon 0.83EC to apple trees, average residue concentrations of the active ingredient, novaluron, were found to be 3.38 ppm in tree-collected pollen. Residues of the major co-formulant in Rimon 0.83EC, N-methyl-2-pyrrolidone (NMP), were below the limit of detection in the field, but a growth chamber study described here found that NMP can persist in pollen for up to 7 d with average concentrations of 69.3 ppm. Concurrent larval rearing studies found novaluron and NMP to be toxic to developing honey bees at doses as low as 100 ppb and 100 ppm, respectively. Nucleus colony feeding studies found that chronic exposure to Rimon 0.83EC at doses as low as 200 ppm (18.6 ppm novaluron) can result in interruptions to brood production that can last for up to 2 wk after exposure. Taken together, these data indicate the use of Rimon 0.83EC on blooming flowers is a significant threat to honey bee reproduction, and suggest the need for more strict and clear usage guidelines.

Determination of nonylphenol ethoxylate and octylphenol ethoxylate surfactants in beehive samples by high performance liquid chromatography coupled to mass spectrometry.

Nonylphenol and octylphenol ethoxylates (NP(EO)n and OP(EO)n) are major toxicants in agrochemicals used around beehives. Here we developed a LC-MS method for analysis of NP(EO)3-13 and OP(EO)3-13 oligomers in bee hive matrices. Less than 2 g of honey, pollen or wax were extracted using the QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) approach. Recoveries for each oligomer in all matrices are between 75% and 111% at three spiked concentrations. The method proved to be rapid, precise and sensitive. Five honey, 10 pollen and 12 wax samples were collected and analysed. NP(EO)n was detected in every sample with concentrations ranging from 26 ppb to 10,239 ppb. Much higher NP(EO)n residues levels were found in wax followed by pollen than in honey. OP(EO)n concentrations on average were more than 10 times lower in pollen and wax. This method demonstrates a probable wide occurrence of alkylphenol ethoxylates in USA beehives.

Quantitative determination of trisiloxane surfactants in beehive environments based on liquid chromatography coupled to mass spectrometry.

Organosilicone surfactants are increasingly being applied to agricultural agro-ecosystems as spray adjuvants, and were recently shown to impact the learning ability of honey bees. Here we developed a method for analyzing three trisiloxane surfactants (single polyethoxylate (EO) chain and end-capped with methyl, acetyl, or hydroxyl groups; TSS-CH3, TSS-COCH3, or TSS-H) in beehive matrices based on liquid chromatography coupled to mass spectrometry (LC-MS) and the QuEChERS (quick, easy, cheap, effective, rugged, and safe) approach from less than 2 g of honey, pollen, or beeswax. Recoveries for each oligomer (2-13 EO) were between 66 and 112% in all matrices. Average method detection limits (MDL) were 0.53, 0.60, 0.56 ng/g in honey, 0.63, 0.81, 0.78 ng/g in pollen, and 0.51, 0.69, 0.63 ng/g in beeswax. Five honey, 10 pollen, and 10 beeswax samples were analyzed. Trisiloxane surfactants were detected in every beeswax and 60% of the pollen samples. Total trisiloxane surfactant concentrations were up to 390 and 39 ng/g in wax and pollen. The described method is proved suitable for analyzing trisiloxane surfactants in beehive samples. The presence of trisiloxane surfactants in North American beehives calls for renewed effort to investigate the consequence of these adjuvants to bee health and the ongoing global bee decline.

High levels of miticides and agrochemicals in North American apiaries: implications for honey bee health.

BACKGROUND: Recent declines in honey bees for crop pollination threaten fruit, nut, vegetable and seed production in the United States. A broad survey of pesticide residues was conducted on samples from migratory and other beekeepers across 23 states, one Canadian province and several agricultural cropping systems during the 2007-08 growing seasons. METHODOLOGY/PRINCIPAL FINDINGS: We have used LC/MS-MS and GC/MS to analyze bees and hive matrices for pesticide residues utilizing a modified QuEChERS method. We have found 121 different pesticides and metabolites within 887 wax, pollen, bee and associated hive samples. Almost 60% of the 259 wax and 350 pollen samples contained at least one systemic pesticide, and over 47% had both in-hive acaricides fluvalinate and coumaphos, and chlorothalonil, a widely-used fungicide. In bee pollen were found chlorothalonil at levels up to 99 ppm and the insecticides aldicarb, carbaryl, chlorpyrifos and imidacloprid, fungicides boscalid, captan and myclobutanil, and herbicide pendimethalin at 1 ppm levels. Almost all comb and foundation wax samples (98%) were contaminated with up to 204 and 94 ppm, respectively, of fluvalinate and coumaphos, and lower amounts of amitraz degradates and chlorothalonil, with an average of 6 pesticide detections per sample and a high of 39. There were fewer pesticides found in adults and brood except for those linked with bee kills by permethrin (20 ppm) and fipronil (3.1 ppm). CONCLUSIONS/SIGNIFICANCE: The 98 pesticides and metabolites detected in mixtures up to 214 ppm in bee pollen alone represents a remarkably high level for toxicants in the brood and adult food of this primary pollinator. This represents over half of the maximum individual pesticide incidences ever reported for apiaries. While exposure to many of these neurotoxicants elicits acute and sublethal reductions in honey bee fitness, the effects of these materials in combinations and their direct association with CCD or declining bee health remains to be determined.

An isorhamnetin rhamnoglycoside serves as a costimulant for sugars and amino acids in feeding responses of adult western corn rootworms (Diabrotica virgifera virgifera) to corn (Zea mays) pollen.

Adult beetles of Diabrotica virgifera virgifera LeConte (western corn rootworm) feed on pollen of Zea mays L. (corn) and other plant species. To identify D. virgifera feeding stimulants, beetle responses to mixtures of known and novel phagostimulants, presented at their naturally occurring concentrations in maize pollen, were compared to individual component responses applying the amount occurring in 0.2 mg of pollen per cellulose feeding disk. On a molar basis, three major sugars (fructose, glucose, and sucrose) were more prevalent in corn pollen buffer extract (CPE) than free amino acids. Western corn rootworm feeding was stimulated by the three sugars (28% disk consumption) and, to an even greater extent, by a mixture of 21 free amino acids (41% disk consumption). However, the combination of three sugars and 21 amino acids elicited a level of D. virgifera feeding (41% disk consumption) similar to that of the 21 amino acids alone. A novel maize pollen phagostimulant was purified from CPE by using solid-phase extraction followed by RP-HPLC. Based on its mass fragment pattern, two UV maxima (254 and 359 nm), and previous isolation from maize pollen, this phagostimulant is tentatively identified as isorhamnetin 3-O-neohesperidoside. This compound interacted additively with the mixture of three sugars and 21 amino acids, to produce 77% of the phagostimulation level of CPE. Therefore, a possible stimulatory mechanism for D. virgifera feeding on corn pollen has been elucidated.

Antifeedant effects of proteinase inhibitors on feeding behaviors of adult western corn rootworm (Diabrotica virgifera virgifera).

Low-molecular-weight peptidyl proteinase inhibitors (PIs) including leupeptin, calpain inhibitor I, and calpeptin were found to be potent antifeedants for adult western corn rootworm (WCR) against the phagostimulation of cucurbitacin B (Cuc B) or a corn pollen extract (CPE). Leupeptin was the strongest (ED50 = 0.36 and 0.55 nmol/disk for Cuc B and CPE, respectively) among PIs tested with an antifeedant potency much stronger than the steroid progesterone (ED50 = 2.29 and 5.05 nmol/disk for Cuc B and CPE, respectively), but slightly less than the reference alkaloid, strychnine (ED50 = 0.17 and 0.37 nmol/disk for Cuc B and CPE, respectively). All active PIs contain a di- or tripeptidyl aldehyde moiety, indicating that PIs exert their antifeedant effects by covalent interaction with putative sulfhydryl (SH) groups on taste receptors as do these PIs with cysteine proteinases. However, opposite inhibition potency against Cuc B versus CPE by two thiol-group reducing agents, DTT and L-cysteine, and the results with other cysteine-modifying reagents obscure the net functional role of SH groups at WCR taste chemoreceptors. Surprisingly, the model phagostimulant for diabroticites, Cuc B, was more easily counteracted by these feeding deterrents than the stimulants present in CPE. Three-dimensional structure-antifeedant relationships for the PIs suggest that a novel taste chemoreception mechanism exists for these peptidyl aldehydes or that they fit partially into a strychnine binding pocket on protein chemoreceptors. Favorable economic benefit may be achieved if PIs are discovered to be useful in adult WCR control, since both pre- and postingestive sites would be targeted.

Impact of cysteine proteinase inhibition in midgut fluid and oral secretion on fecundity and pollen consumption of western corn rootworm (Diabrotica virgifera virgifera).

Cysteine proteinases predominate in the midgut fluid (MF) and oral secretion (OS) of adult western corn rootworm (WCR) based on their mild acidic pH optima (pH 6.0), enhanced activities after treatment with thiol reducing agents, and inhibition by selective cysteine proteinase inhibitors (PIs). Four cysteine PIs including E-64, calpeptin, calpain inhibitor II, and leupeptin (also a serine PI) strongly inhibited azocaseinolytic activity in a dose-dependent manner in both the MF and OS. The most significant effect on adult female WCR of cysteine PI consumption with corn pollen was the reduction in fecundity, but female survival was not apparently affected. Mean fresh weights for all PI-fed females were also lower than control groups. All PI-fed groups [E-64, calpain inhibitor I (Cal I) and leupeptin] had a significantly lower daily egg production than respective corn pollen-fed controls. E-64 was more potent than leupeptin and Cal I on inhibiting fecundity, which correlates with their relative anti-proteinase potency in vitro. E-64, Cal I, and leupeptin at 1.5-2 nmol/beetle/day reduced fecundity down to 25-45% of control values. Reduced egg production by PI-fed beetles results from a combination of the direct inhibition of protein digestion and a post-ingestive negative feedback mechanism, which reduces food intake. The supplement of ten essential amino acids into the E-64-treated pollen enhanced up to 3.7-fold the number of eggs laid compared to the E-64-fed group without these amino acids, suggesting that egg production is dependent on the supply of essential amino acids from corn pollen proteolysis.