Workshop report: strategies for setting occupational exposure limits for engineered nanomaterials.

Occupational exposure limits (OELs) are important tools for managing worker exposures to chemicals; however, hazard data for many engineered nanomaterials (ENMs) are insufficient for deriving OELs by traditional methods. Technical challenges and questions about how best to measure worker exposures to ENMs also pose barriers to implementing OELs. New varieties of ENMs are being developed and introduced into commerce at a rapid pace, further compounding the issue of OEL development for ENMs. A Workshop on Strategies for Setting Occupational Exposure Limits for Engineered Nanomaterials, held in September 2012, provided an opportunity for occupational health experts from various stakeholder groups to discuss possible alternative approaches for setting OELs for ENMs and issues related to their implementation. This report summarizes the workshop proceedings and findings, identifies areas for additional research, and suggests potential avenues for further progress on this important topic.

Factors associated with sources, transport, and fate of chloroform and three other trihalomethanes in untreated groundwater used for drinking water.

Multiple lines of evidence for indicating factors associated with the sources, transport, and fate of chloroform and three other trihalomethanes (THMs) in untreated groundwater were revealed by evaluating low-level analytical results and logistic regression results for THMs. Samples of untreated groundwater from wells used for drinking water were collected from 1996-2007 from 2492 wells across the United States and analyzed for chloroform, bromodichloromethane, dibromochloromethane, and bromoform by a low-level analytical method implemented in April 1996. Using an assessment level of 0.02 µg/L, chloroform was detected in 36.5% of public-well samples and 17.6% of domestic-well samples, with most concentrations less than 1 µg/L. Brominated THMs occurred less frequently than chloroform but more frequently in public-well samples than domestic-well samples. For both public and domestic wells, THMs occurred most frequently in urban areas. Logistic regression analyses showed that the occurrence of THMs was related to nonpoint sources such as urban land use and to point sources like septic systems. The frequent occurrence and concentration distribution pattern of THMs, as well as their frequent co-occurrence with other organic compounds and nitrate, all known to have anthropogenic sources, and the positive associations between THM occurrence and dissolved oxygen and recharge indicate the recycling of water that contains THMs and other anthropogenic contaminants.

A comparative dose-related response of several key pro- and antiinflammatory mediators in the lungs of rats, mice, and hamsters after subchronic inhalation of carbon black.

OBJECTIVE: The objective of this study was to investigate mechanisms underlying species specificity in particle-induced lung inflammation. METHODS: Rats, mice, and hamsters exposed to air, 1, 7, or 50 mg/m3 of carbon black for 13 weeks were killed at 1 day, 3 months, and 11 months after exposure. Bronchoalveolar lavage was performed and characterized for cell number, cell type, reactive oxygen and nitrogen species, and cytokine levels. Ex vivo mutational analysis of inflammatory cells was evaluated by coincubating with lung epithelial cells. Lung tissue was evaluated for gene expression of various antiinflammatory mediators. RESULTS: There was a dose- and time-related effect with all the parameters. Rats demonstrated greater propensity for generating a proinflammatory response, whereas mice and hamsters demonstrated an increased antiinflammatory response. CONCLUSIONS: These differences in pro- and antiinflammatory responses may contribute to the apparent species differences in inflammation and tumorigenesis.

Research strategies for safety evaluation of nanomaterials, part II: toxicological and safety evaluation of nanomaterials, current challenges and data needs.

This article summarizes a roundtable discussion held at the 2005 Society of Toxicology Annual Meeting in New Orleans, LA. The purpose of the roundtable was to review the current challenges and data needs for conducting toxicological and safety evaluations for nanomaterials, with the goals of presenting the current state-of-the science on the safety of nanomaterials and bringing together scientists representing government, academia, and industry to identify priorities for developing data to facilitate risk assessments for these materials. In this summary, the unique physicochemical properties associated with nanomaterials are reviewed in the context of the difficulties associated with measuring and characterizing them. In addition, the development of appropriate hazard data, the collection of accurate human and environmental exposure information, and the development of a better fundamental understanding of the modes of action for nanomaterials are discussed as factors that will impact the development of comprehensive toxicological and safety evaluations.