Addressing the relevance of polystyrene nano- and microplastic particles used to support exposure, toxicity and risk assessment: implications and recommendations.

Background: There has been an exponential increase in the number of studies reporting on the toxicological effects associated with exposure to nano and microplastic particles (NMPs). The majority of these studies, however, have used monodispersed polystyrene microspheres (PSMs) as 'model' particles. Here we review the differences between the manufacture and resulting physicochemical properties of polystyrene used in commerce and the PSMs most commonly used in toxicity studies.

Screening and prioritization of nano- and microplastic particle toxicity studies for evaluating human health risks - development and application of a toxicity study assessment tool.

Unlabelled: Concern regarding the human health implications that exposure to nano- and microplastic particles (NMPs) potentially represents is increasing. While there have been several years of research reporting on the ecotoxicological effects of NMPs, human health toxicology studies have only recently emerged. The available human health hazard data are thus limited, with potential concern regarding the relevance and reliability for understanding the potential human health implications.

Systems Modeling of Developmental Vascular Toxicity.

The more than 80,000 chemicals in commerce present a challenge for hazard assessments that toxicity testing in the 21 century strives to address through high-throughput screening (HTS) assays. Assessing chemical effects on human development adds an additional layer of complexity to the screening, with a need to capture complex and dynamic events essential for proper embryo-fetal development. HTS data from ToxCast/Tox21 informs systems toxicology models, which incorporate molecular targets and biological pathways into mechanistic models describing the effects of chemicals on human cells, 3D organotypic culture models, and small model organisms.

In vitro genotoxicity studies: n-Butyl acrylate L5178Y mouse lymphoma (TK+/- locus assay), 2-Ethylhexyl acrylate gene mutation assay in Chinese hamster V79 cells, and 2-Ethylhexyl acrylate micronucleus test in human lymphocytes.

Available point mutation tests have shown inconsistent results with various acrylates. Most of those tests were performed prior to OECD guidelines and appropriate data regarding cytotoxicity are not given. Data from three current OECD guideline compliant experiments conducted under GLP are provided.

Critical evaluation of 2-ethylhexyl acrylate dermal carcinogenicity studies using contemporary criteria.

Skin tumors have been observed in C3H/HeJ mice following treatment with high and strongly irritating concentrations of 2-ethylhexyl acrylate (2-EHA). Dermal carcinogenicity studies performed with 2-EHA are reviewed, contrasting the results in two mouse strains (C3H/HeJ and NMRI) under different dosing regimens. Application of contemporary evaluation criteria to the existing dermal carcinogenicity dataset demonstrates that 2-EHA induces skin tumors only at concentrations exceeding an maximum tolerated dose (MTD) and in the immune-dysregulated C3H/HeJ mouse model.