Search

Insensitive munitions offer increased safety because of their “insensitivity” to unintended detonation relative to historically used formulations such as 2,4,6-trinitrotoluene (TNT). Dinitroanisole (DNAN) is an insensitive munition constituent, and its solubility and stability warrant investigations of potential toxicological hazard related to manufacturing discharges and training ranges. Although ecotoxicology data are available for other insensitive munition constituents, few data are available for DNAN. In the present study, acute and chronic exposures of a fish (Pimephales promelas) and 2 cladocerans (Ceriodaphnia dubia, Daphnia pulex) were conducted. The 50% lethal concentration (LC50) values of DNAN ranged from 14.2 mg/L to 42.0 mg/L, depending on species. In chronic exposures, fish survival (LC50 = 10.0 mg/L) was more sensitive than cladoceran survival (LC50 = 13.7 to >24.2 mg/L). However, cladoceran reproduction was equally or more sensitive to DNAN (50% inhibition values 2.7–10.6 mg/L, depending on species) than fish endpoints. Daphnia pulex was the most sensitive species, with only slight differences between the 3 populations tested. Although the aquatic toxicity of DNAN was lower than previously reported in the literature for TNT, future research is needed to determine the potential synergistic toxicity of all the constituents in insensitive munition mixtures and the implications of photo-oxidation. Environ Toxicol Chem 2014;9999:1–10. © 2014 SETAC

As the production and applications of silver nanoparticles (AgNPs) increase, it is essential to characterize fate and effects in environmental systems. Nanosilver materials may settle from suspension; therefore, the authors' objective was to utilize environmentally relevant bioassays and study the impact, bioaccumulation, tissue distribution, uptake, and depuration of AgNPs on a sediment-dwelling invertebrate, Lumbriculus variegatus. Hydrodynamic diameters of uncoated 30-nm, 80-nm, and 1500-nm AgNP powders and a polyvinyl pyrrolidone (PVP) AgNP suspension were measured utilizing dynamic light scattering in freshwater media (0-280 µS/cm). Aggregation for 30 nm, 80 nm, and 1500 nm silver increased with conductivity but was minimal for PVP silver. Lumbriculus variegatus were exposed to AgNPs or silver nitrate (AgNO3 ) spiked into sediment (nominally 100 mg/kg) and water (PVP 30 nm and 70 nm Ag, nominally 5 mg/L). Uptake was assessed through inductively coupled plasma mass spectroscopy (ICP-MS) and hyperspectral imaging. Particle sizes were examined through field flow fractionation-ICP-MS (FFF-ICP-MS) and ICP-MS in single particle mode (SP-ICP-MS). Lumbriculus variegatus were also depurated for 6 h, 8 h, 24 h, and 48 h to determine gut clearance. Bioaccumulation factors of sediment-exposed L. variegatus were similar regardless of particle size or coatings. The FFF-ICP-MS and SP-ICP-MS detected AgNPs for up to 48 h post depuration. The present study provides information on bioaccumulation and interactions of AgNPs within biological systems.

Carbon nanotubes were previously demonstrated to accumulate on the carapace and in the gut of daphnids in aquatic exposures. The purpose of the present study was to assess the effects of multiwalled carbon nanotube (MWCNT) exposure on the sublethal Daphnia magna endpoints swimming behavior, algal feeding, growth, and reproduction and to determine the relative magnitude of difference between lethal and sublethal toxicity thresholds in 48-h and 14-d exposures. A stable dispersion of MWCNTs was prepared using 100 mg/L natural organic matter (NOM), and all treatments were compared statistically to a NOM control. The swimming behavior endpoints of mean velocity and total distance moved were determined using digital tracking software. For the acute (48-h) exposure, a 50% lethal concentration (LC50) of 29.3 (23.6-36.3) mg/L and a 50% effective concentration (EC50) of 6.7 mg/L in the swimming velocity endpoint were determined. When swimming response was nonmonotonic below 2 mg/L, consistent reductions in velocity were observed at 6.9 mg/L and above. Median effect concentrations were lower in the chronic (14-d) bioassay. The 14-d LC50 was 4.3 mg/L (3.3-5.6 mg/L), and the reproduction EC50 was 5.0 mg/L. Lowest-observed-effect concentrations for survival and reproduction were 5.4 mg/L and 1.7 mg/L, respectively. Significantly fewer (23.1%) algal cells were consumed in the 3.9-mg/L treatment relative to the control. No significant effects on swimming behavior were observed for the 14-d bioassay. Less traditional sublethal endpoints such as swimming behavior and feeding rate may be especially important to assess for MWCNTs and other materials expected to be more physically than chemically toxic through mechanisms such as gut clogging.

Insensitive munitions offer increased safety because of their "insensitivity" to unintended detonation relative to historically used formulations such as 2,4,6-trinitrotoluene (TNT). Dinitroanisole (DNAN) is an insensitive munition constituent, and its solubility and stability warrant investigations of potential toxicological hazard related to manufacturing discharges and training ranges. Although ecotoxicology data are available for other insensitive munition constituents, few data are available for DNAN. In the present study, acute and chronic exposures of a fish (Pimephales promelas) and 2 cladocerans (Ceriodaphnia dubia, Daphnia pulex) were conducted. The 50% lethal concentration (LC50) values of DNAN ranged from 14.2 mg/L to 42.0 mg/L, depending on species. In chronic exposures, fish survival (LC50 = 10.0 mg/L) was more sensitive than cladoceran survival (LC50 = 13.7 to24.2 mg/L). However, cladoceran reproduction was equally or more sensitive to DNAN (50% inhibition values 2.7-10.6 mg/L, depending on species) than fish endpoints. Daphnia pulex was the most sensitive species, with only slight differences between the 3 populations tested. Although the aquatic toxicity of DNAN was lower than previously reported in the literature for TNT, future research is needed to determine the potential synergistic toxicity of all the constituents in insensitive munition mixtures and the implications of photo-oxidation.

As the production and applications of silver nanoparticles (AgNPs) increase, it is essential to characterize fate and effects in environmental systems. Nanosilver materials may settle from suspension; therefore, the authors' objective was to utilize environmentally relevant bioassays and study the impact, bioaccumulation, tissue distribution, uptake, and depuration of AgNPs on a sediment-dwelling invertebrate, Lumbriculus variegatus. Hydrodynamic diameters of uncoated 30-nm, 80-nm, and 1500-nm AgNP powders and a polyvinyl pyrrolidone (PVP) AgNP suspension were measured utilizing dynamic light scattering in freshwater media (0-280 µS/cm). Aggregation for 30 nm, 80 nm, and 1500 nm silver increased with conductivity but was minimal for PVP silver. Lumbriculus variegatus were exposed to AgNPs or silver nitrate (AgNO3 ) spiked into sediment (nominally 100 mg/kg) and water (PVP 30 nm and 70 nm Ag, nominally 5 mg/L). Uptake was assessed through inductively coupled plasma mass spectroscopy (ICP-MS) and hyperspectral imaging. Particle sizes were examined through field flow fractionation-ICP-MS (FFF-ICP-MS) and ICP-MS in single particle mode (SP-ICP-MS). Lumbriculus variegatus were also depurated for 6 h, 8 h, 24 h, and 48 h to determine gut clearance. Bioaccumulation factors of sediment-exposed L. variegatus were similar regardless of particle size or coatings. The FFF-ICP-MS and SP-ICP-MS detected AgNPs for up to 48 h post depuration. The present study provides information on bioaccumulation and interactions of AgNPs within biological systems.