Toxicological Risks of Agrochemical Spray Adjuvants: Organosilicone Surfactants May Not Be Safe

Abstract

Agrochemical risk assessment that takes into account only pesticide active ingredients without the spray adjuvants commonly used in their application will miss important toxicity outcomes detrimental to non-target species, including humans. Lack of disclosure of adjuvant and formulation ingredients coupled with a lack of adequate analytical methods constrains the assessment of total chemical load on beneficial organisms and the environment. Adjuvants generally enhance the pesticidal efficacy and inadvertently the non-target effects of the active ingredient. Spray adjuvants are largely assumed to be biologically inert and are not registered by the USA EPA, leaving their regulation and monitoring to individual states. Organosilicone surfactants are the most potent adjuvants and super-penetrants available to growers. Based on the data for agrochemical applications to almonds from California Department of Pesticide Regulation, there has been increasing use of adjuvants, particularly organosilicone surfactants, during bloom when two-thirds of USA honey bee colonies are present. Increased tank mixing of these with ergosterol biosynthesis inhibitors and other fungicides and with insect growth regulator insecticides may be associated with recent USA honey bee declines. This database archives every application of a spray tank adjuvant with detail that is unprecedented globally. Organosilicone surfactants are good stand alone pesticides, toxic to bees, and are also present in drug and personal care products, particularly shampoos, and thus represent an important component of the chemical landscape to which pollinators and humans are exposed. This mini review is the first to possibly link spray adjuvant use with declining health of honey bee populations.

An Inert Pesticide Adjuvant Synergizes Viral Pathogenicity and Mortality in Honey Bee Larvae

“…2a), and that statewide organosilicone-surfactant use increased just prior to the onset of Colony Collapse Disorder and the increased colony losses observed in 2006 (Fig. 2b)429.…”

“…per acre of OSS adjuvants in California almonds29. Additional CADPR data referencing a major area of almond production, Stanislaus County, indicate that Sylgard 309 applications are commonplace during the late January to March bloom period (Fig.…”

“…To simulate a horizontal infectious event, the larvae were initially exposed to diet containing infectious viral material consisting of pathogens commonly found circulating in honey bee hives and foraging environments including Black Queen Cell Virus (BQCV), Deformed Wing Virus (DWV) Israeli Acute Paralysis Virus (IAPV) and Sacbrood Virus (SBV)30 or an equivalent volume of saline containing no infectious material. Chronic OSS exposure was assessed at 10 ppm in diet (v/v), a 1,000 fold dilution from a tank mix concentration of 1%, to simulate a potentially field relevant exposure rate29. After the first day, all larvae received only 10 ppm OSS or control (Ctrl) diet according to treatment group.…”

Non-target effects of a glyphosate-based herbicide on Common toad larvae (Bufo bufo, Amphibia) and associated algae are altered by temperature

“…the products that are actually used in the field, are more detrimental to tadpoles and other aquatic organisms than the active ingredient glyphosate itself (Folmar, Sanders & Julin, 1979; Howe et al, 2004; Relyea, 2005b). However, unfortunately these adjuvants are usually not declared and considered company secrets (Mullin et al, 2016; Wagner et al, 2013). Besides amphibians, several studies also show that freshwater microalgae are particularly vulnerable to glyphosate-based herbicides because of their physiological and biochemical similarity with terrestrial plants (Annett, Habibi & Hontela, 2014; Tsui & Chu, 2003) mainly by initiating oxidative stress in algae (Annett, Habibi & Hontela, 2014).…”

Evaluation of occupational glyphosate exposures among employees applying herbicides at a national park.

“…They also facilitate and enhance the absorbing, emulsifying, dispersing, spreading, sticking, wetting, or penetrating properties of herbicides [Mullin et al 2016]. In particular, surfactants are used to reduce the surface tension between the spray droplet and leaf surface.…”