Comprehensive review of ensulizole toxicology data and human exposure assessment for personal care products
Bibliographic record
Abstract
A comprehensive review of existing toxicity and human exposure data for the ultraviolet filter ensulizole (2-phenylbenzimidazole-5-sulfonic acid) as currently used in over-the-counter sunscreen formulations was conducted. Authorized maximum ensulizole usage levels in consumer end-use products worldwide range from 3% to 8%, with the maximum usage level limited to 4% in the United States, Canada, and Australia. Postmarketing clinical safety studies of ensulizole have reported only occasional local skin effects, none of which were associated with systemic toxicity. Ensulizole has been investigated in vitro, in animal toxicity studies, and in human studies for its pharmacokinetics, pharmacodynamics, and potential toxicological properties. Experimentally determined values of 4% for oral absorption in rats and of 0.26% for dermal absorption in humans were used for risk calculation purposes. There was no evidence of ensulizole bioaccumulation from rat in vivo studies, consistent with its high water solubility and low octanol/water partition coefficient. Ensulizole is not classifiable as an irritant, although local skin irritation with no systemic effects was noted in a 3-month repeated-dose dermal toxicity study in rabbits. Ensulizole is non-(photo)sensitizing, non-phototoxic, and has demonstrated low toxicity in acute (oral, dermal, and intraperitoneal) and subchronic repeated-dose studies in mammalian species. Subchronic 3-month no-observed-adverse-effect levels (NOAELs) were identified at 100 mg/kg/day (dermal rabbit) and 1000 mg/kg/day (oral rat OECD 408 study), the highest doses tested, respectively. Ensulizole is considered non-genotoxic, based on negative in vitro studies. No in vivo genotoxicity or long-term carcinogenicity studies were identified. Carcinogenicity risk is not expected based on the negative genotoxicity data, empirical evidence from repeated-dose toxicity and developmental toxicity studies, and the absence of effects on the androgen, estrogen, thyroid, immune, developmental, or reproductive systems. Based on the selected rat subchronic NOAEL of 1000 mg/kg/day and conservative assumptions for estimating the systemic exposure dose (SED) from the application of sunscreen products, margins of safety (defined as NOAEL/SED) >100 were obtained for ensulizole. Therefore, the available data show that ensulizole does not pose risks to human health when used in sunscreen products at concentrations up to 4%, the permitted maximum usage level in the United States, Canada, and Australia.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.004 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".