Subchronic inhalation toxicity of gold nanoparticles

Risk, associated with nanomaterial use, is determined by exposure and hazard potential of these materials. Both topics cannot be evaluated absolutely independently. Realistic dose concentrations should be tested based on stringent exposure assessments for the corresponding nanomaterial taking into account also the environmental and product matrix. This review focuses on current available information from peer reviewed publications related to airborne nanomaterial exposure. Two approaches to derive realistic exposure values are differentiated and independently presented; those based on workplace measurements and the others based on simulations in laboratories. An assessment of the current available workplace measurement data using a matrix, which is related to nanomaterials and work processes, shows, that data are available on the likelihood of release and possible exposure. Laboratory studies are seen as an important complementary source of information on particle release processes and hence for possible exposure. In both cases, whether workplace measurements or laboratories studies, the issue of background particles is a major problem. From this review, major areas for future activities and focal points are identified.     

Nanosilver induces minimal lung toxicity or inflammation in a subacute murine inhalation model

Background

Multi-walled carbon nanotubes (MWCNTs) are new manufactured nanomaterials with a wide spectrum of commercial applications. To address the hypothesis that MWCNTs cause persistent pulmonary pathology, C57BL/6J mice were exposed by pharyngeal aspiration to 10, 20, 40 or 80 μg of MWCNTs (mean dimensions of 3.9 μm × 49 nm) or vehicle. Lungs were preserved at 1, 7, 28 and 56 days post- exposure to determine the potential regions and target cells for impact by MWCNT lung burden. Morphometric measurement of Sirius Red staining was used to assess the connective tissue response.

Results

At 56 days post-exposure, 68.7 ± 3.9, 7.5 ± 1.9 and 22.0 ± 5.1 percent (mean ± SE, N = 8) of the MWCNT lung burden were in alveolar macrophages, alveolar tissue and granulomatous lesions, respectively. The subpleural tissues contained 1.6% of the MWCNT lung burden. No MWCNTs were found in the airways at 7, 28 or 56 days after aspiration The connective tissue in the alveolar interstitium demonstrated a progressive increase in thickness over time in the 80 μg exposure group (0.12 ± 0.01, 0.12 ± 0.01, 0.16 ± 0.01 and 0.19 ± 0.01 μm for 1, 7, 28 and 56 days post-exposure (mean ± SE, N = 8)). Dose-response determined at 56 days post-exposure for the average thickness of connective tissue in alveolar septa was 0.11 ± 0.01, 0.14 ± .02, 0.14 ± 0.01, 0.16 ± 0.01 and 0.19 ± 0.01 μm (mean ± SE, N = 8) for vehicle, 10, 20, 40 and 80 μg dose groups, respectively.

Conclusions

The distribution of lung burden was predominately within alveolar macrophages with approximately 8% delivery to the alveolar septa, and a smaller but potentially significant burden to the subpleural tissues. Despite the relatively low fraction of the lung burden being delivered to the alveolar tissue, the average thickness of connective tissue in the alveolar septa was increased over vehicle control by 45% in the 40 μg and 73% in the 80 μg exposure groups. The results demonstrate that MWCNTs have the potential to produce a progressive, fibrotic response in the alveolar tissues of the lungs. However, the increases in connective tissue per μg dose of MWCNTs to the interstitium are significantly less than those previously found for single-walled carbon nanotubes (SWCNTs).     

Nanosilver induces minimal lung toxicity or inflammation in a subacute murine inhalation model

Background  

There is increasing interest in the environmental and health consequences of silver nanoparticles as the use of this material becomes widespread. Although human exposure to nanosilver is increasing, only a few studies address possible toxic effect of inhaled nanosilver. The objective of this study was to determine whether very small commercially available nanosilver induces pulmonary toxicity in mice following inhalation exposure.     

Smoke and toxicity

Smoke and toxic gases (STG) are the main cause of fire deaths. They combine to make escape difficult and to retard rescue work and fire-fighting. The paper reviews advances in the characterization of the STG hazard, and discusses improved materials of construction to meet the new, more stringent safety criteria used by responsible architects and design engineers. Because of the wide choice of safer materials now available at reasonable cost in a number of product areas such as furniture foams and cable insulation, the time is approaching when such materials can be introduced without harming the economics of these industries. Indeed, a convincing demonstration of intrinsic safety could without harming the economics of these industries. Indeed, a convincing demonstration of intrinsic safety could encourage the introduction of improved plastics and other organic materials into a wide range of market applications.     

DEHP and toxicity

DEHP has had widespread use in flexible vinyls, serving as the workhorse plasticizer. Extensive studies have shown that DEHP has a very low order of toxicity. Originally, concern developed over the effect DEHP might have on the environment. In 1980 results of two-year feeding studies on rats and mice by NCI caused the emphasis to shift to health aspects of DEHP. Although evidence to date shows DEHP has extremely low order of toxicity (acute), is a minimal irritant to skin or eyes, and poses no hazard to the environment, the chemical industry will continue investigations of phthalate plasticizers.     

The physical toxicity of chemicals. V. Interaction terms for solubilities and partition coefficients

The solubilities of anisole, phenetole, 1,3-dimethoxybenzene and benzonitrile in water at 25° have been measured, and the partition coefficients of these compounds together with p-toluonitrile between cyclohexane and water have been determined. Aromatic ether groups interact less with water than do aliphatic ether groups. Aromatic nitriles interact with water and appear to be associated in the liquid state and in concentrated solutions. The use of partition coefficients and solubilities for interpretation and prediction of toxicities is discussed.     

Biological vs. Chemical evaluation of toxicity and protein quality of cottonseed meals

Summary 1. Toxicological evaluation of 68 cottonseed meals in rats failed to show a direct correlation between their toxicity and their free, total or combined gossypol content. The common practice of considering the free gossypol content of cottonseed meal as a yardstick for its toxicity is questioned. 2. There was poor correlation between biologically evaluated protein quality of cottonseed meals and their nitrogen solubility in 0.02N sodium hydroxide. Application of this chemical test for indicating the protein quality of cottonseed meals is likewise questioned on the basis of existing evidence. Presented at the Conference on Cottonseed Meal Quality as Related to Processing, Southern Regional Research Laboratory, New Orleans, La., January 24–25, 1955.