Commercial formulations of pesticides are invariably not single ingredients. Instead they are cocktails of chemicals, composed of a designated pesticidal "active principle" and "other ingredients," with the latter collectively also known as "adjuvants." These include surfactants, antifoaming agents, dyes, etc. Some adjuvants are added to influence the absorption and stability of the active principle and thus promote its pesticidal action. Currently, the health risk assessment of pesticides in the European Union and in the United States focuses almost exclusively on the stated active principle. Nonetheless, adjuvants can also be toxic in their own right with numerous negative health effects having been reported in humans and on the environment. Despite the known toxicity of adjuvants, they are regulated differently from active principles, with their toxic effects being generally ignored. Adjuvants are not subject to an acceptable daily intake, and they are not included in the health risk assessment of dietary exposures to pesticide residues. Here, we illustrate this gap in risk assessment by reference to glyphosate, the most used pesticide active ingredient. We also investigate the case of neonicotinoid insecticides, which are strongly suspected to be involved in bee and bumblebee colony collapse disorder. Authors of studies sometimes use the name of the active principle (for example glyphosate) when they are testing a commercial formulation containing multiple (active principle plus adjuvant) ingredients. This results in confusion in the scientific literature and within regulatory circles and leads to a misrepresentation of the safety profile of commercial pesticides. Urgent action is needed to lift the veil on the presence of adjuvants in food and human bodily fluids, as well as in the environment (such as in air, water, and soil) and to characterize their toxicological properties. This must be accompanied by regulatory precautionary measures to protect the environment and general human population from some toxic adjuvants that are currently missing from risk assessments.

Ignoring Adjuvant Toxicity Falsifies the Safety Profile of Commercial Pesticides.

Pesticides are commonly used in agriculture to enhance crop production and control pests. Therefore, pesticide residues can persist in the environment and agricultural crops. Although modern formulations are relatively safe to non-target species, numerous theoretical and experimental data demonstrate that pesticide residues can produce long-term negative effects on the health of humans and animals and stability of ecosystems. Of particular interest are molecular mechanisms that mediate the start of a cascade of adverse effects. This is a review of the latest literature data on the effects and consequences of contamination of agricultural crops by pesticide residues. In addition, we address the issue of implicit risks associated with pesticide formulations. The effects of pesticides are considered in the context of the Adverse Outcome Pathway concept.

Pesticides: formulants, distribution pathways and effects on human health - a review.

The potential effects of adjuvants, including surfactants used in pesticide formulation, have been extensively studied for many small organic chemicals, but similar investigation on pesticides is limited in most cases. Solubilizing effects leading to the apparently increased water solubility of a pesticide are commonly known through the preparation of formulations, but fundamental profiles, especially for a specific monodisperse surfactant, are not fully studied. Reduced volatilization of a pesticide from the formulation can be explained by analogy of a very simple organic chemical, but the actual mechanism for the pesticide is still obscure. In contrast, from the point of view of avoiding groundwater contamination with a pesticide, adsorption/desorption profiles in the presence of surfactants and adjuvants have been examined extensively as well as pesticide mobility in the soil column. The basic mechanism in micelle-catalyzed hydrolysis is well known, and theoretical approaches including the PPIE model have succeeded in explaining the observed effects of surfactants, but its application to pesticides is also limited. Photolysis, especially in an aqueous phase, is in the same situation. The dilution effect in the real environment would show these effects on hydrolysis and photolysis to be much less than expected from the laboratory basic studies, but more information is necessary to examine the practical extent of the effects in an early stage of applying a pesticide formulation to crops and soil. Many adjuvants, including surfactants, are biodegradable in the soil environment, and thus their effects on the biodegradation of a pesticide in soil and sediment may be limited, as demonstrated by field trials. Not only from the theoretical but also the practical aspect, the foliar uptake of pesticide in the presence of adjuvants has been investigated extensively and some prediction on the ease of foliar uptake can be realized in relation to the formulation technology. However, effect on root uptake of pesticides is to be further investigated. In an aqueous environment more or less contaminated by various chemicals such as detergents and their degradates, it is necessary to investigate the effect of adjuvants on uptake, bioconcentration, and trophic transfer of pesticides for better understanding of pesticide contamination of aquatic species in the aquatic environment.

Surfactant effects on environmental behavior of pesticides.

Developmental toxicity and transcriptome analysis of zebrafish (Danio rerio) embryos following exposure to chiral herbicide safener benoxacor

Investigating the biodegradation pattern of an ecofriendly pesticide delivery system based on wheat gluten and organically modified montmorillonites

The aim of our research was to determine the influence of the soil type and adjuvants on the dynamics of ethofumesate degradation in soil. Samples of two types of soil were placed in growth chambers. Ethofumesate was applied at a rate of 800 g·ha -1 , alone and in mixture with adjuvant based on methylated crop oil and surfactant adjuvant. Residues of ethofumesate were determined using high-performance liquid chromatography with UV detection. The type of soil influenced the degradation rate of ethofumesate. Significant differences in degradation rate between soils during the first period after treatment (36 days) influenced the DT50 indicator. The addition of oil adjuvant slowed down the degradation of ethofumesate and increased the level of residue in soils. The DT50 value for mixture ethofumesate + oil adjuvant was about 8-10 days higher in comparison with the DT50 for ethofumesate applied alone. No significant differences were observed between degradation rates and the DT50 for ethofumesate applied alone and with surfactant adjuvant.

Degradation of ethofumesate in soil under laboratory conditions

Influence of herbicide and adjuvant application on residues in soil and plant of sugar-beet

The aim of the present study was to determine the influence of an addition of adjuvants on behavior of metazachlor in soil - residues, degradation rate and leaching into the soil profile. Experiments were carried out in field and laboratory conditions. Metazachlor was applied alone and in mixture with three different adjuvants: oil, surfactant and multicomponent (dedicated to preemergence application). Metazachlor residue was analyzed using GC/ ECD. At harvest time, in soil samples taken from plots where metazachlor was applied alone, the residue amounted to 0.0072 mg kg -1 . The addition of adjuvants caused an increase of metazachlor residues (0.0082–0.0108 mg kg -1 ). The adjuvant addition caused a slowdown of leaching of herbicide into soil profile. Moreover the addition of oil and surfactant adjuvants slowed down the degradation of metazachlor in soils. The DT 50 values for mixture metazachlor + oil and surfactant adjuvants were about 8-16 days higher in comparison with the DT 50 for metazachlor applied alone (26 days). No significant differences were observed between degradation rates and the DT 50 for metazachlor applied alone and with multicomponent adjuvant.

Behaviour of metazachlor applied with additives in soil: laboratory and field studies.

The aim of the present study was to determine the infl u- ence of an addition of adjuvants on behaviour of phenmedipham in agricultural environment - residues in soil, plant, degradation rate and leaching into the soil profi le. Field experiments were conducted during a three-year -period from 2006 until 2008 on ar - able fi elds located in South-Western Poland. Chemical weed con- trol in sugar beet was carried out by commercial formulation of phenmedipham. The herbicide was applied alone and in mixture with adjuvants (oil and surfactant). Phenmedipham residues were analysed using high performance liquid chromatography with UV detection. At lifting time, in soil samples taken from plots where phenmedipham was applied alone, the residues amounted to 0.0082-0.0128 mg kg -1 . In sugar beet roots samples, the resi- dues of phenmedipham were lower than in soil and amounted to 0.0032-0.0084 mg kg -1 . The addition of adjuvants caused an in- crease of the active substance (a.s.) residues in soil and roots of sugar beet. The residues of phenmedipham determined in roots did not exceed acceptable values MRLs (Maximum Residue Lev- els). The addition of oil adjuvant reduced the degradation rate of phenmedipham in soil. No signifi cant differences were observed between degradation rates for phenmedipham applied alone and with surfactant adjuvant. The DT 50 value for mixture phen- medipham + oil adjuvant was about 1

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Influence of adjuvants on behavior of phenmedipham in plant and soil

The aim of this work was to evaluate the influence of an adjuvant addition on chloridazon degradation rate in soil. The experiment was carried out under controlled laboratory conditions. Chloridazon was applied alone and in a mixture with three different adjuvants: oil, surfactant and multicomponent (used for preemergence application). Chloridazon residue was analysed us- ing gas chromatography with electron capture detector (GC/ECD). Good linearity was found between logarithmic concentration of chloridazon residues and time. The addition of oil and surfactant adjuvants slowed down the degradation of chloridazon in soil. The DT 50 values for the mixture of chloridazon + oil and surfactant adjuvants was about 8-14 days higher in comparison with the DT 50 for chloridazon applied alone (43 days). No significant differences were observed between degradation rates and the DT 50 for chloridazon applied alone and with a multicomponent adjuvant.

http://www.plantprotection.pl/pdf-92261-26315?filename=Degradation rate of.pdf

Mariusz Kucharski

Papers

Degradation of ethofumesate in soil under laboratory conditions

Influence of herbicide and adjuvant application on residues in soil and plant of sugar-beet

Behaviour of metazachlor applied with additives in soil: laboratory and field studies.

Influence of adjuvants on behavior of phenmedipham in plant and soil

Degradation Rate of Chloridazon in Soil as Influenced by Adjuvants