Derivation and application of indoor air screening values for inhalation exposure to semi-volatile organic compounds.

Semi-volatile organic compounds (SVOCs) are being increasingly studied in indoor air. The absence of health-based inhalation exposure guidelines for most SVOCs impedes the interpretation of indoor air concentrations from a health risk context. To accelerate the derivation of screening values for a large number of SVOCs, a tiered framework was developed to evaluate and adjust published hazard assessments for SVOCs to calculate benchmarks relevant for evaluation of inhalation risk. Inhalation screening values were derived for 43 SVOCs considered in this study, most of which required extrapolation from oral exposure guidelines. The screening values were compared to published SVOC concentrations in homes in Canada to evaluate the potential health risks of chronic exposure to SVOCs in indoor residential environments. SVOCs that could be prioritized for further evaluation were dibutyl phthalates (DBP), di(2-ethylhexyl) phthalate (DEHP) and polybrominated diphenyl ethers (PBDEs). The framework could be applied more broadly in the future to derive screening values for other non-traditional indoor air contaminants with limited inhalation hazard data or assessments.

Application of a framework for the selection of an appropriate occupational exposure limit for manganese.

Occupational exposure limits (OELs) serve as benchmarks for the interpretation of workplace exposures within a health risk context. Different organizations derive OELs for many chemicals, including manganese. OELs recommended by different organizations can vary quantitatively, which can present a challenge to occupational hygienists or other risk managers that need to select a value for decision-making purposes. In this article, we illustrate the application of a previously-developed OEL selection framework to demonstrate the decisions that would be required to select the most appropriate OEL for various manganese exposure scenarios. The framework helped to identify the need to focus an evaluation on three quantitatively similar values-the ACGIH TLV, SCOEL IOELV, and DFG MAK. These values were compared with regulatory standards and considered for their relevance and reliability. The OEL selection framework was a useful tool in guiding the selection process for manganese OELs.

Technical guide for applications of gene expression profiling in human health risk assessment of environmental chemicals.

Toxicogenomics promises to be an important part of future human health risk assessment of environmental chemicals. The application of gene expression profiles (e.g., for hazard identification, chemical prioritization, chemical grouping, mode of action discovery, and quantitative analysis of response) is growing in the literature, but their use in formal risk assessment by regulatory agencies is relatively infrequent. Although additional validations for specific applications are required, gene expression data can be of immediate use for increasing confidence in chemical evaluations. We believe that a primary reason for the current lack of integration is the limited practical guidance available for risk assessment specialists with limited experience in genomics. The present manuscript provides basic information on gene expression profiling, along with guidance on evaluating the quality of genomic experiments and data, and interpretation of results presented in the form of heat maps, pathway analyses and other common approaches. Moreover, potential ways to integrate information from gene expression experiments into current risk assessment are presented using published studies as examples. The primary objective of this work is to facilitate integration of gene expression data into human health risk assessments of environmental chemicals.

Contribution of drinking water to dietary requirements of essential metals.

Drinking water can be a source of essential metals, but only one study published thus far has compared the intake of essential metals in drinking water to dietary reference intakes. This assessment compares the ingestion of chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), selenium (Se), and zinc (Zn) from drinking water at the maximum concentrations that should be found in water, or at concentrations that are potentially more likely to be found in Canadian water, to the recommended dietary allowance or adequate intake values established by the Institute of Medicine. At guideline limits, water provides sufficient Cr and Cu to meet nutritional requirements, and Mn and Zn levels are sufficient for some age categories to meet nutritional requirements. At concentrations that are more likely to be found in Canadian water, adequate intakes for Cr and Mn may be met by water alone for bottle-fed infants, and water was estimated to provide 23-66% of daily Cu requirements. Drinking water might become a significant source of some essential metals in individuals whose diets are low in these metals, especially in the case of Cu.