Secondary organophosphate esters: A review of environmental source, occurrence, and human exposure
Bibliographic record
Abstract
Organophosphate esters (OPEs), a group of synthetic chemicals widely used as flame retardants and plasticizers, have garnered significant international attention due to their adverse effects on the environment and human health. Traditionally, environmental OPEs are thought to originate via direct emissions. Recent evidence suggests that OPEs also have an important indirect source: The transformation of organophosphite antioxidants (another group of mass-produced commercial chemicals) to OPEs via atmospheric chemical reactions. This indirect source can lead to the formation of secondary OPEs (SOPEs) such as tris(2,4-di-tert-butylphenyl) phosphate (TDtBPP), which are widely distributed in the global environment and have distinct physiochemical and toxic properties compared with the well-studied primary OPEs. Therefore, there is an urgent need to obtain a strong fundamental knowledge of SOPEs. This review summarizes the current understanding of the sources, environmental occurrence, human exposure pathways, and environmental hazards of SOPEs. They have been detected in various environmental matrices such as air, soil, and indoor dust, as well as in consumer products such as face masks and foodstuffs. Notably, the reported SOPE concentrations are higher than most primary OPEs. Human exposure pathways related to SOPEs include dietary intake, dust ingestion, hand-to-mouth contact, dermal absorption, and air inhalation. Additionally, risk evaluation indicates that SOPEs are more persistent in the environment and in organisms, and may pose a higher risk than the primary OPEs. Finally, by summarizing the current advances and remaining challenges for the investigation of SOPEs, we propose future research directions regarding their environmental monitoring needs, transformation chemistry, environmental impact, and health effect.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.005 | 0.005 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
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 source (direct Gemma or distilled Codex), 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".