Predicting Prenatal Developmental Toxicity Based On the Combination of Chemical Structures and Biological Data.

For hazard identification, classification, and labeling purposes, animal testing guidelines are required by law to evaluate the developmental toxicity potential of new and existing chemical products. However, guideline developmental toxicity studies are costly, time-consuming, and require many laboratory animals. Computational modeling has emerged as a promising, animal-sparing, and cost-effective method for evaluating the developmental toxicity potential of chemicals, such as endocrine disruptors, without the use of animals. We aimed to develop a predictive and explainable computational model for developmental toxicants. To this end, a comprehensive dataset of 1244 chemicals with developmental toxicity classifications was curated from public repositories and literature sources. Data from 2140 toxicological high-throughput screening assays were extracted from PubChem and the ToxCast program for this dataset and combined with information about 834 chemical fragments to group assays based on their chemical-mechanistic relationships. This effort revealed two assay clusters containing 83 and 76 assays, respectively, with high positive predictive rates for developmental toxicants identified with animal testing guidelines (PPV = 72.4 and 77.3% during cross-validation). These two assay clusters can be used as developmental toxicity models and were applied to predict new chemicals for external validation. This study provides a new strategy for constructing alternative chemical developmental toxicity evaluations that can be replicated for other toxicity modeling studies.

Read-across: Principle, case study and its potential regulatory application in China.

Read-across, has generated much attention and has been used in many regulatory schemes as an alternative approach to testing globally. The regulatory application of read-across in the chemical management in China is progressing but still limited. A workshop on the "Read-across: Principle, case study and its potential regulatory application in China", organized by the Chemical Risk Assessment Specialty Group under the Committee of Industrial Toxicology of Chinese Society of Toxicology, was held on May 28, 2019 to discuss the potential broader application and acceptance of read-across to support chemical risk assessment in China. The Workshop included global experts from regulatory agencies, academia and industry. Scientific presentations and constructive discussions raised awareness on the use of read-across in different regions, identified barriers to regulatory acceptance, and participants also brainstormed on practical strategies to help facilitate the further regulatory application of read-across approaches in China.

Correction to: Acute aquatic toxicity of tire and road wear particles to alga, daphnid, and fish.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Exploration of the GARD™skin applicability domain: Indirectly acting haptens, hydrophobic substances and UVCBs.

Hazard assessments of skin sensitizers are increasingly performed using new approach methodologies (NAMs), with several in chemico, in vitro, and most recently, also defined approaches accepted for regulatory use. However, keeping track of potential limitations of each method to define applicability domains remains a crucial component to ensure adequate predictivity and to facilitate the appropriate selection of method(s) for each hazard assessment task. The objective of this report is to share test results generated with the GARD™skin assay on chemicals that have traditionally been considered difficult to test in some of the conventional in vitro and in chemico OECD Test Guidelines for skin sensitization. Such compounds may include, for example, indirectly acting haptens, hydrophobic substances, and substances of unknown or variable composition, complex reaction products or biological substances (UVCBs). Based on the results of this study, the sensitivity for prediction of skin sensitizing hazard of indirectly acting haptens was 92.4% and 87.5% when compared with local lymph node assay (LLNA) (n = 25) and human data (n = 8), respectively. Similarly, the sensitivity for prediction of skin sensitizing hazard of hydrophobic substances was 85.1% and 100% when compared with LLNA (n = 24) and human data (n = 9), respectively. Lastly, a case study involving assessment of a set of hydrophobic UVCBs (n = 7) resulted in a sensitivity of 100% compared to available reference data. These data provide support for the inclusion of such chemistries in the GARD™skin applicability domain without an increased risk of false negative classifications.

Acute aquatic toxicity of tire and road wear particles to alga, daphnid, and fish.

Previous studies have indicated that tire tread particles are toxic to aquatic species, but few studies have evaluated the toxicity of such particles using sediment, the likely reservoir of tire wear particles in the environment. In this study, the acute toxicity of tire and road wear particles (TRWP) was assessed in Pseudokirchneriella subcapita, Daphnia magna, and Pimephales promelas using a sediment elutriate (100, 500, 1000 or 10000 mg/l TRWP). Under standard test temperature conditions, no concentration response was observed and EC/LC(50) values were greater than 10,000 mg/l. Additional tests using D. magna were performed both with and without sediment in elutriates collected under heated conditions designed to promote the release of chemicals from the rubber matrix to understand what environmental factors may influence the toxicity of TRWP. Toxicity was only observed for elutriates generated from TRWP leached under high-temperature conditions and the lowest EC/LC(50) value was 5,000 mg/l. In an effort to identify potential toxic chemical constituent(s) in the heated leachates, toxicity identification evaluation (TIE) studies and chemical analysis of the leachate were conducted. The TIE coupled with chemical analysis (liquid chromatography/mass spectrometry/mass spectrometry [LC/MS/MS] and inductively coupled plasma/mass spectrometry [ICP/MS]) of the leachate identified zinc and aniline as candidate toxicants. However, based on the high EC/LC(50) values and the limited conditions under which toxicity was observed, TRWP should be considered a low risk to aquatic ecosystems under acute exposure scenarios.