An analysis of prenatal exposure factors and offspring health outcomes in rodents from synthesized nanoparticles.

Over the past several decades the industry involving nanotechnology has developed at a rapid pace, increasing global human exposure to synthesized nanoparticles (NPs). A consensus within toxicology on the effect of synthesized NPs to human health has yet to be reached, and little is known about the NPs developmental toxicology to organisms exposed in utero. This review aimed to identify the current state of in vivo prenatal NP toxicology literature and to provide an overview of several influential factors on offspring exposure and health outcomes. Scientific peer-reviewed literature was identified through PubMed, Web of Science, and Google Scholar database searches using combinations of keywords relevant to prenatal NP exposure. The 220 articles yielded from the database search were screened for inclusion and exclusion criteria, and 37 articles were included in the final analysis. Across selected literature, eight NP materials and eight exposure routes were identified. Pregnant murine dams were exposed to NPs throughout the entire gestational period, and some studies expanded exposure durations into preconception or postnatal periods. The average particle size across all exposure routes was 27.03 nm, although aerosolized agglomerates and cellular uptake where not accounted for. Thirty-five studies reported significant adverse effects on offspring after birth, where abnormalities of the nervous system were most commonly reported. Although current literature suggests a biological plausibility for prenatal NP toxicity, the lack of standardized methodology and diverse endpoints contribute to the continued ambiguity as to the attributable risks of individual exposure factors on health outcomes and mechanisms of cellular toxicity.

Particle Emissions from Laboratory Activities Involving Carbon Nanotubes.

This site study was conducted in a chemical laboratory to evaluate nanomaterial emissions from 20-30 nm diameter bundles of single-walled carbon nanotubes (CNTs) during product development activities. Direct-reading instruments were used to monitor the tasks in real time and airborne particles were collected using various methods to characterize released nanomaterials using electron microscopy and elemental carbon (EC) analyses. CNT clusters and a few high aspect ratio particles were identified as being released from some activities. The EC concentration at the source of probe sonication was found to be higher than other activities including weighing, mixing, centrifugation, coating and cutting. Various sampling methods all indicated different levels of CNTs from the activities, however, the sonication process was found to release the highest amounts of CNTs. It can be cautiously concluded that the task of probe sonication possibly released nanomaterials into the laboratory and posed a risk of surface contamination. Based on these results, the sonication of CNT suspension should be covered or conducted inside a ventilated enclosure with proper filtration or a glovebox to minimize the potential of exposure.

Performance of Particulate Containment at Nanotechnology Workplaces.

The evaluation of engineering controls for the production or use of carbon nanotubes (CNTs) was investigated at two facilities. These controls assessments are necessary to evaluate the current status of control performance and to develop proper control strategies for these workplaces. The control systems evaluated in these studies included ventilated enclosures, exterior hoods, and exhaust filtration systems. Activity-based monitoring with direct-reading instruments and filter sampling for microscopy analysis were used to evaluate the effectiveness of control measures at study sites. Our study results showed that weighing CNTs inside the biological safety cabinet can have a 37% reduction on the particle concentration in the worker's breathing zone, and produce a 42% lower area concentration outside the enclosure. The ventilated enclosures used to reduce fugitive emissions from the production furnaces exhibited good containment characteristics when closed, but they failed to contain emissions effectively when opened during product removal/harvesting. The exhaust filtration systems employed for exhausting these ventilated enclosures did not provide promised collection efficiencies for removing engineered nanomaterials from furnace exhaust. The exterior hoods were found to be a challenge for controlling emissions from machining nanocomposites: the downdraft hood effectively contained and removed particles released from the manual cutting process, but using the canopy hood for powered cutting of nanocomposites created 15%-20% higher ultrafine (<500 nm) particle concentrations at the source and at the worker's breathing zone. The microscopy analysis showed that CNTs can only be found at production sources but not at the worker breathing zones during the tasks monitored.

Evaluation of environmental filtration control of engineered nanoparticles using the Harvard Versatile Engineered Nanomaterial Generation System (VENGES).

Applying engineering controls to airborne engineered nanoparticles (ENPs) is critical to prevent environmental releases and worker exposure. This study evaluated the effectiveness of two air sampling and six air cleaning fabric filters at collecting ENPs using industrially relevant flame-made engineered nanoparticles generated using a versatile engineered nanomaterial generation system (VENGES), recently designed and constructed at Harvard University. VENGES has the ability to generate metal and metal oxide exposure atmospheres while controlling important particle properties such as primary particle size, aerosol size distribution, and agglomeration state. For this study, amorphous SiO(2) ENPs with a 15.4 nm primary particle size were generated and diluted with HEPA-filtered air. The aerosol was passed through the filter samples at two different filtration face velocities (2.3 and 3.5 m/min). Particle concentrations as a function of particle size were measured upstream and downstream of the filters using a specially designed filter test system to evaluate filtration efficiency. Real time instruments (FMPS and APS) were used to measure particle concentration for diameters from 5 to 20,000 nm. Membrane-coated fabric filters were found to have enhanced nanoparticle collection efficiency by 20-46 % points compared to non-coated fabric and could provide collection efficiency above 95 %.