Environmental exposure modeling has been used extensively in the last years to obtain estimates of environmental concentrations of engineered nanomaterials (ENMs). In this perspective piece, we explore the issues when aiming to validate modeled environmental concentrations and propose options for both modelers and analytical chemists on how to proceed in the future to better compliment one another's efforts. In this context, validation means to determine the degree to which the simulation results from a model are accurate representations of the real world by comparison with analytical data. Therefore, for such a model validation procedure, analytical methods need to be available which provide information in the same subject area. Currently, a major issue with nanometrology is that a multitude of nanomaterials are present in natural systems but only some are ENMs; various other particles of natural origin are abundant in the same systems. The analytical tools available are not yet capable to distinguish the natural from engineered nanomaterials at the low ENM concentrations expected in complex environmental matrices. However, both modeling and analytical studies are able to provide an orthogonal view on nanomaterials: modeling is able to yield estimates of the presence of ENMs in various environmental compartments while analytics can provide physical characterization of ENMs in these systems with hints towards the total nanomaterial concentration. While we need to make strides to improve the two approaches separately, using the resulting data together in a mutually supportive way will advance the field of ENM risk assessment. Nano impactModeling studies are used to obtain information on environmental exposure concentrations of engineered nanomaterials. All model systems, including those describing nanomaterial fate and transport, always call for a validation by analytical data. However, in this case, there are currently only very limited measurements available and, further complicating the issue, it is difficult to distinguish between natural and engineered nanomaterials in many circumstances. In this perspective article we raise the point that it is currently not possible to validate modeled data on engineered nanomaterial concentrations in the environment, but rather that modeling and analytics can be used in tandem to provide an orthogonal view on the presence of nanomaterials in the environment.

The toxicity of sulfuryl fluoride (SF) to various pest species, the penetration of SF into flour, and the potential for any problems to arise because of fumigant cross resistance or malfunction of electronic equipment exposed to SF were studied in the UK. The pest species included Tribolium castaneum (rust-red flour beetle), T. confusum (confused flour beetle) Cryptolestes turcicus (Turkish grain beetle), Ephestia kuehniella (Mediterranean flour moth), Ptinus tectus (Australian spider beetle), Sitophilus granarius (granary weevil), Gnatocerus cornutus (broad-horned flour beetle), Tenebrio molitor (meal worm), Liposcelis bostrychophila (book louse) and Acarus siro (flour mite). For most of the pests, the egg stage was the most tolerant of fumigation, but the postembryonic stages of mites were as tolerant as the eggs. Most of the species were completely controlled by a concentration × product of 500 g h-1 m-3 at 30°C, or 1000 g h-1 m-3 at 25°C. Penetration studies into flour of 30 cm depth revealed that SF required 30 to 40 minutes to break through to this level whether or not there was forced air movement over the flour surface, and that only 2.5-3 h were required, irrespective of temperature over the range 18-28°C, for concentrations to reach 50-60% of those at the surface. At venting, 90% of the gas present in flour at 30-cm depth had dissipated after 4.5 h. Studies on phosphine-resistant and susceptible strains of T. castaneum revealed no cross resistance to SF, and repeated exposure of computer equipment to the gas revealed no malfunction. SF is a promising replacement for methyl bromide in the flour milling industry.

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Adventitious presence of genetically modified crops (AGMP) in their non‐GM counterparts is an important problem in the EU, where a policy of coexistence between the two is being sought. The economic impacts of AGMP could be severe and could prevent the practical application of GM coexistence measures. To date, research has concentrated on the contribution of pollen gene flow as the major source of AGMP, while other sources have not been investigated. We have examined the potential for AGMP from the use of shared farm equipment and transport, which has previously been assumed to have a low contribution. Oilseed rape (OSR) was examined in a typical UK production regime including tillage, sowing, spraying, harvesting and grain drying. At each stage in the process, OSR in the machinery was measured and its potential for AGMP calculated. In sowing and grain drying, mustard grain was used as a proxy for GM grain and was measured during the processes by real‐time PCR quantification to give estimates of GM dilution rates during the processes. The effects of cleaning and other mitigation methods were examined. Total potential AGMP was estimated at 1.47% when no mitigation was performed, and 0.08% when machinery was cleaned. The best measures for avoiding this type of AGMP are presented in the context of the specific UK agriculture examined in this study.