The use of hematological effects in the development of minimal risk levels

A survey of nitrate and nitrite concentrations in conventional and organic-labeled raw vegetables at retail

A national survey of the nitrate ( NO3(-)) and nitrite ( NO2(-)) concentrations in raw and highly consumed vegetables available at retail in the United States was conducted. A total of 194 samples of fresh broccoli, cabbage, celery, lettuce, and spinach categorized as conventional or organic by label were collected from 5 major cities in different geographic regions of the United States and analyzed to determine NO3(-) and NO2(-) concentrations. There were no differences in the mean NO2(-) values of conventional compared with organic vegetables taken from the 5 metropolitan areas. However, significant differences in mean pairwise comparisons between some conventional and organic vegetables for NO3(-) content were observed. The mean NO2(-) concentration of both conventional and organic vegetables ranged between 0.1 and 1.2 mg/kg of fresh weight (FW) with the exception of conventional spinach that contained 8.0 mg/kg FW. Mean NO3(-) contents of conventional broccoli, cabbage, celery, lettuce, and spinach were 394, 418, 1496, 851, and 2797 mg/kg FW, respectively, while their organic-labeled counterparts averaged 204, 552, 912, 844, and 1318 mg/kg FW. In most cases, organic vegetables were numerically lower in NO3(-) content than their conventional counterparts. Based on survey results, the finding that low NO3(-) levels were observed in some organic vegetables in different cities may warrant further study to determine if true differences exist, due to production practices, seasonal differences, and the magnitudes of those differences. Furthermore, the geographic differences in NO3(-) content of vegetables may flaw estimates of daily NO2(-) and NO3(-) exposure.

The relationship between repeat-dose toxicity and aromatic-ring class profile of high-boiling petroleum substances

A study was undertaken within the context of the U.S. EPA HPV Chemical Challenge Program to (1) characterize relationships between PAC content and repeat-dose toxicities of high-boiling petroleum substances (HBPS) and (2) develop statistical models that could be used to predict the repeat-dose toxicity of similar untested substances. The study evaluated 47 repeat-dose dermal toxicity and 157 chemical compositional studies. The four most sensitive endpoints of repeat-dose toxicity were platelet count, hemoglobin concentration, relative liver weight and thymus weight. Predictive models were developed for the dose-response relationships between the wt.% concentration of each of seven ring classes of aromatic compounds (the "ARC profile") and specific effects, with high correlations (r=0.91-0.94) between the observed and model-predicted data. The development of the mathematical models used to generate the results reported in this study is described by Nicolich et al. (2013). Model-generated dose-response curves permit the prediction of either the effect at a given dose or the dose that causes a given effect. The models generate values that are consistent with other standard measures. The models, using compositional data, can be used for predicting the repeat-dose toxicity of untested HBPS.

Health effects classification and its role in the derivation of minimal risk levels: Renal effects

The Agency for Toxic Substances and Disease Registry (ATSDR) derives minimal risk levels (MRLs) for priority hazardous substances. MRLs are health guidance values intended to serve as screening levels for health assessors to select contaminants of concern and to assess potential health effects at hazardous waste sites and areas affected by unplanned releases. Current MRLs are published in ATSDR toxicological profiles and are listed at the ATSDR website at . To date, ATSDR has derived 125 inhalation MRLs, 207 oral MRLs, and eight external radiation MRLs; 19 MRLs are based on renal effects. This article reports on endpoints used to derive the MRLs. It also presents the ranking of effects into less serious and serious categories as described in ATSDR's Guidance for Developing Toxicological Profiles.

Health effects classification and its role in the derivation of minimal risk levels: Hepatic effects

The Agency for Toxic Substances and Disease Registry (ATSDR) derives health based guidance values called minimal risk levels (MRLs) to assist with assessment of risks posed by exposures to hazardous chemicals. Current MRLs are posted on ATSDR's web site (www.atsdr.cdc.gov). From the total 326 MRLs currently posted, 79 MRLs are based on hepatic endpoints. The paper reports on endpoints used for the derivation of these MRLs and the use of uncertainty factors. It also describes the ranking of effects into less serious and serious categories as described in ATSDR's Guidance for Developing Toxicological Profiles.