The release of microplastics (MPs) from nylon tea bags poses a critical concern for human exposure; however, their detection and quantification remain challenging especially in beverage matrices, and hence, this study pioneers the use of high-resolution optical coherence tomography (OCT) integrated with an image processing algorithm to rapidly detect and quantify the size and count of the MPs directly in the water extractions simulating tea brewing. The water extractions prepared by simulating tea brewing conditions, hot (100 °C, 1–5 min), cold (2 °C, 1 h), and ambient (30 °C, 1 h), were observed employing OCT imaging and validated through Nile Red (NR) staining and digital microscopy. The nylon tea bags steeped in hot water for 5 minutes released 16 000 to 24 000 LMPs (>30 µm) and SMPs (12–30 µm) per millilitre. The estimated daily intake (EDI) of MPs indicates a higher exposure for children (ranging from 0.201 to 0.349 mm³ kg⁻¹ day⁻¹) compared to adults (0.046 to 0.080 mm³ kg⁻¹ day⁻¹). In contrast, cold brewing for 1 hour released fewer LMPs but an equal quantity of small MPs (SMPs) compared to hot brewing. This OCT-based approach offers a rapid, versatile platform for the detection and quantification of MPs from diverse packaging materials and provides a powerful tool for comprehensive risk assessment when combined with chemical and toxicological analyses.

Rising atmospheric CO ₂ levels have significantly increased ocean acidification (OA), endangering coral reefs, and nutrient (nitrate (NO ₃ ⁻ ), and phosphate (PO ₄ ³⁻ )) pollution also weakens the coral reef resilience. Therefore, the study evaluates the prevailing OA level over the Sri Lankan coral reef areas using the aragonite saturation state (Ω _Ar ) and assesses the nitrate (NO ₃ ⁻ ), and phosphate (PO ₄ ³⁻ ) concentrations over the coral sites. The study was conducted on coral reefs on the eastern coast (EC), southern coast (SC), northern coast (NC), and west coast (WC) of Sri Lanka from April to June 2024. A total of 63 seawater samples were collected around each coastal site for analysis. The Ω _Ar were supersaturated (Ω _Ar > 1) and ranged from 2.98 ± 0.04 to 4.92 ± 0.12. Throughout the study period, the study sites had Ω _Ar values exceeding 2.92 ± 0.16, indicating that the nation's corals were resilient to deterioration, and the comparative analysis demonstrates that these sites were not vulnerable to OA. The NO ₃ ⁻ concentrations of 2–5 µmol L ^− 1 , from human activities, may intensify coral bleaching during heat stress. Results showed that SC (2.19 ± 1.28 µmol L ^− 1 ) and WC (3.52 ± 1.48 µmol L ^− 1 ) had NO ₃ ⁻ above the permissible range, which may be due to waste discharge and high runoff. The significantly higher PO ₄ ³⁻ concentrations were reported in EC (0.35 ± 0.07 µmol L ^− 1 ). Coral bleaching hotspot (HS) identification emphasizes how spatially distributed HS are from January to June. The OA risk assessment confirmed that climate change brought high risk to the coral reef ecosystems, which impact on the ecology and economy of Sri Lanka.