Aquatic hazard assessment of MON 0818, a commercial mixture of alkylamine ethoxylates commonly used in glyphosate‐containing herbicide formulations. Part 1: Species sensitivity distribution from laboratory acute exposures

Abstract

Abstract:The sensitivity of 15 aquatic species, including primary producers, benthic invertebrates, cladocerans, mollusks, and fish, to MON 0818, a commercial surfactant mixture of polyoxyethylene tallow amines, was evaluated in standard acute (48-96-h) laboratory tests. In addition, the potential for chronic toxicity (8 d) was evaluated with Ceriodaphnia dubia. Exposure concentrations were confirmed. No significant effects on any endpoint were observed in the chronic test. A tier-1 hazard assessment was conducted by comparing species sensitivity distributions based on the generated data, as well as literature data, with 4 exposure scenarios. This assessment showed moderate levels of hazard (43.1% of the species exposed at or above median effective concentration levels), for a chosen worst-case scenario-unintentional direct over-spray of a 15-cm-deep body of water with the maximum label application rate for the studied formulations (Roundup Original, Vision Forestry Herbicide; 12 L formulation ha À1 , equivalent to 4.27 kg acid equivalent [a.e.] ha À1 ). The hazard decreased to impairment of 20.9% of species under the maximum application rate for more typical uses (6 L formulation ha À1 , 2.14 kg a.e. ha À1 ), and down to 6.9% for a more frequently employed application rate (2.5 L formulation ha À1 , 0.89 kg a.e. ha À1 ). Finally, the percentage (3.8%) was less than the hazardous concentration for 5% of the species based on concentrations of MON 0818 calculated from maximum measured concentrations of glyphosate in the environment. Environ Toxicol Chem 2017;36:501-511. # 2016 SETAC

Aquatic hazard assessment of MON 0818, a commercial mixture of alkylamine ethoxylates commonly used in glyphosate‐containing herbicide formulations. Part 2: Roles of sediment, temperature, and capacity for recovery following a pulsed exposure

“…The effect of increased test temperature on cold‐water fish species was assessed with S. namaycush and S. alpinus . As presented in Table , no significant differences were observed between the toxicity values calculated for S. namaycush when tested at 10 °C or 15 °C. However, higher temperature increased the sensitivity of S. alpinus to MON 0818 as apparent from the significant difference ( p < 0.05, ANOVA) in EC50 values.…”

“…When tested in the presence of sediment, the EC50 values for all tested organisms were greater than those calculated from water‐only tests . In 3 cases, no significant mortality was observed, even at the greatest tested concentration (10 mg L −1 nominal).…”

“…The calculated EC10, EC25, EC50, and EC90 values for tests with aquatic organisms in the presence of sediment are presented in Table and compared to the results of the water‐only tests presented in Rodriguez‐Gil et al . In all cases, the calculated EC50 values were significantly greater (assessed by comparison of the 95% confidence intervals for each estimate) in the presence of sediment compared with those from the water‐only tests.…”

“…Comparison of the median effective concentration values (EC50s) calculated for the species tested in the presence of sediment and the EC50s obtained under the same conditions but in the absence of sediment as presented in the companion study . For reference, the species sensitivity distribution presented in the companion study is also plotted.…”

“…However, as noted in the companion paper, , a direct estimation of hazard from standard laboratory studies (based on water‐only 48–96‐h exposures) and worst‐case estimated exposure concentrations (EECs) can, in some cases, greatly overestimate the actual risk posed by a compound in real‐world systems, and should be considered only as a first step in a tiered risk assessment approach . In the case of POEA, the development of higher tier probabilistic approaches, taking into account actual field‐measured concentrations and their probability distributions, has been traditionally limited by the lack of adequate analytical methods able to quantify the compound at environmentally and/or toxicologically relevant concentrations.…”