Table 1.
Summary of total assessment scores (TAS) and QA/QC criteria strengths and weaknesses of in vivo studies prioritized based on adequate evaluation of critical QA/QC identified as part of a Tier 1 screening assessment. Strengths and weaknesses listed reflect how the data support or limit, respectively, the interpretation of study results within a risk assessment context. Strengths and weaknesses are thus context-specific, and those listed as strengths here may be perceived as weaknesses under another context, and vice versa. Additional study information included in the Supplementary Information
| Author | Strengths | Weaknesses | TAS (/52) |
|---|---|---|---|
| Lim et al. (2021) [102] | Excellent reporting of study design characteristics; inclusion of both sub-organismal and organism level endpoints reported helping to inform potential mechanisms of toxicological action | Monodisperse polystyrene spherical particles – unclear how to extrapolate results to environmentally relevant exposures. | 37 |
| Ma-Hock et al. (2012) [97] | Excellent reporting of particle characteristics and exposure conditions, including an estimate relating external exposure to an internal dose; NOAEL reported based on no adverse effects up to the maximum concentration tested. | Single type of polymer tested at only two concentration doses, plus control – acrylic ester copolymer – unclear how to extrapolate results to environmentally relevant exposures. | 37 |
| Ong et al. (2020) [74] | Study conducted according to repeat oral dose OECD 408 guideline with excellent reporting for all three areas evaluated, including particle characteristics, study design and application for risk assessment – NOAEL reported. | Study targets the evaluation of adverse effects related to repeated dietary ingestion of fibrillated cellulose – unclear how to read-across to NMPs. | 44 |
| Amereh et al. (2019) [115] | Good characterization of particles, which include two different sizes in the sub-micron range; particles tested at both high and environmentally relevant concentrations, LOAEL can be extrapolated. | Single type of polymer tested – polystyrene spheres; particles dosed into drinking water, unclear actual delivery and/or homogeneity of exposure; adverse effects limited to sub-organismal level endpoints only. | 34 |
| Amereh et al. (2020) [114] | Good characterization of particles, which include two different sizes in the sub-micron range; particles tested at both high and environmentally relevant concentrations, LOAEL can be extrapolated. | Single type of polymer tested – polystyrene spheres; particles dosed into drinking water, unclear actual delivery and/or homogeneity of exposure; adverse effects limited to sub-organismal level endpoints only. | 34 |
| Deng et al. (2017) [116] | Inclusion of both sub-organismal and organism level endpoints reported helping to inform potential mechanisms of toxicological action, with exposure concentrations reported to represent environmentally relevant concentrations. | Two sizes of monodisperse polystyrene spheres; particles dosed into drinking water, unclear actual delivery and/or homogeneity of exposure; particles supplied as a dispersion in a solution containing 1:1 ethanol:water, unclear residual levels of ethanol in test system. Several comments published in the peer review literature raising concerns related to histopathological analysis and toxicokinetics. | 34 |
| Dolan et al. (2016) [112] | Study conducted according to repeat oral dose OECD 408 guideline with good reporting for study design and application for risk assessment – NOAEL reported. | Poor reporting of particle characteristics, where study reports adverse effects related to repeat dietary ingestion of pecan shell fiber, ground from pecan shells – unclear how to read-across to NMPs. | 34 |
| An et al. (2021) [96] | Lowest test concentration selected as being representative of concentrations reported for freshwater systems. | Monodisperse polystyrene spherical particles – unclear how to extrapolate results to environmentally relevant exposure; particles dosed into drinking water, unclear actual delivery and/or homogeneity of exposure; particles supplied as a dispersion in a solution containing 1:1 ethanol:water, unclear residual levels of ethanol in test system. | 31 |
| Kotkoskie et al. (1996) [113] | Concentration test range selected to be representative of concentrations in food product for human consumption, NOAEL reported. | Poor reporting of particle characteristics, where study reports adverse effects related to repeat dietary ingestion of cellulose fibers – unclear how to read-across to NMPs. | 30 |
| Park et al. (2020) [118] | Various organism and sub-organism level effects reported, including body weight, pathological effects in stomach epithelial cells, effects on reproduction and immune system, such as via Immunoglobins (Ig, IgA, total IgG, IgE, and IgM) | Monodisperse polyethylene particles – unclear how to extrapolate results to environmentally relevant exposure; particles dosed into drinking water, unclear actual delivery and/or homogeneity of exposure; unclear relevance of exposure concentration range used 3.75–60 mg/kg bw; questions related to the use of p < 0.5 as a measure of statistical significance. | 30 |
| Hou et al. (2020) [117] | Body weight and changes in organ coefficients, sperm damage analysis, including count, malformation, etc., inflammatory responses and apoptosis-related proteins and cells. A combination of both organism and sub-organism level endpoints. Concentrations of 0.1, 1, and 10 mg/L used in drinking water, with an estimate that mice drank 6–7 mL/d, resulting in a nominal derived concentration of 0.6–60 μg/d. | Poor particle characterization, with particle description limited to monodisperse polystyrene spherical particles – unclear how to extrapolate results to environmentally relevant exposure. | 27 |
| Li et al. (2020) [121] | Verification of particle size, shape and composition, while sufficiently reporting information for each of the critical criteria. | Monodisperse polystyrene spherical particles – unclear how to extrapolate results to environmentally relevant exposure; particles dosed into drinking water, unclear actual delivery and/or homogeneity of exposure; particles supplied as a dispersion in a solution containing 1:1 ethanol:water, unclear residual levels of ethanol in test system. Concentrations of > 7.18 × 109 particles/L are perceived to be significantly greater than typical human exposure. | 27 |
| Wei et al. (2021) [119] | Verification of particle size, shape and composition, while sufficiently reporting information for each of the critical criteria. | Monodisperse polystyrene spherical particles – unclear how to extrapolate results to environmentally relevant exposure; particles dosed into drinking water, unclear actual delivery and/or homogeneity of exposure; particles supplied as a dispersion in a solution containing 1:1 ethanol:water, unclear residual levels of ethanol in test system. | 27 |
| Xie et al. (2020) [120] | Sufficient level of information reported for each of the critical criteria. | Monodisperse polystyrene spherical particles – unclear how to extrapolate results to environmentally relevant exposure. | 27 |
| Li et al. (2020) [104] | Sufficient level of information reported for each of the critical criteria. | Monodisperse polystyrene spherical particles – unclear how to extrapolate results to environmentally relevant exposure. | 23 |