Comprehensive Assessment of Environmental Emissions, Fate, and Risks of Veterinary Antibiotics in China: An Environmental Fate Modeling Approach.

China is one of the major global consumers of veterinary antibiotics. Insufficient recognition of emissions and environmental contamination hamper global efforts to prevent antibiotic resistance development. This pioneering study combined empirical data and modeling approaches to predict total 2010-2020 emissions of 80 veterinary antibiotics ranging from 23,110 to 40,850 tonnes/year, after 36-50% antibiotic removal by manure treatment. Following an initial increase of 10% from 2010 to 2015, emissions declined thereafter by 43%. While 85% of emissions discharged into soils, approximately 56%, 23%, and 18% of environmental residue were ultimately distributed in soils, freshwaters, and seawaters under steady-state conditions. In 2020, 657 (319-1470) tonnes entered the ocean from inland freshwaters. Median ∑antibiotics concentrations were estimated at 4.7 × 103 ng/L in freshwaters and 2.9 ng/g in soils, with tetracyclines and sulfonamides as the predominant components. We identified 44 veterinary antibiotics potentially posing high risks of resistance development in freshwaters, with seven exhibiting high risks in >10% of Chinese freshwater areas. Tetracyclines were the category with the most antibiotics exhibiting elevated risks; however, sulfamethylthiazole demonstrated the highest individual compound risk. The Haihe River Basin displayed the highest susceptibility overall. The findings offer valuable support for control of veterinary antibiotic contamination in China.

Interspecies calibration for biomonitoring metal contamination in coastal waters using oysters and mussels.

Differences in metal bioaccumulation among species make it difficult to compare biomonitoring results obtained using different marine bivalve species. To address this challenge and improve the interpretation of biomonitoring data, we studied the toxicokinetic mechanisms underlying these differences and developed a method to estimate seawater metal concentrations based on metal concentrations in the organisms. We transplanted six common species of oysters and mussels found in Chinese coastal waters into the Jiulong River estuary and monitored metal concentrations in the organisms, water, and suspended particles every three days over a six-week period. A one-compartment first-order toxicokinetic model was used to describe the relationship between metal bioaccumulation and metal concentrations in the environment. The model parameters, including aqueous uptake (ku) and dietary assimilation (kp) rate constants, and elimination rate constant (ke), were estimated using a Markov Chain Monte Carlo fitting method with a priori information from a systematic review we conducted. The toxicokinetic model successfully fitted the temporal changes in metal bioaccumulation in all six bivalve species and explained the interspecies differences. Using the calibrated models, we were able to calculate metal concentrations in the seawater at the bivalve collection sites and enable comparisons of biomonitoring data across multiple species. In conclusion, we have established a toxicokinetic framework to explain interspecies differences in metal bioaccumulation in six commonly found bivalves and provided a useful tool for interpreting biomonitoring data in coastal environments.

Predicting Risks of Cadmium Toxicity in Salinity-Fluctuating Estuarine Waters Using the Toxicokinetic-Toxicodynamic Model.

In estuaries, salinity fluctuates rapidly and continuously, greatly affecting the bioavailability and thus toxicity of contaminants, especially metals, causing difficulties in deriving site-specific water quality criteria. We developed a method for predicting the toxicity of the metal cadmium (Cd) in estuarine waters of any salinity fluctuation scenario. Cd bioaccumulation and toxicity were measured in an estuarine clam Potamocorbula laevis under stable salinities (salinity = 5, 15, 25) and fluctuating salinities (5-25), using the toxicokinetic-toxicodynamic (TK-TD) framework. Cd bioaccumulation decreases with increasing salinity; whereas intrinsic Cd sensitivity of organisms reaches the minimum at an intermediate salinity around 20. At each specific Cd level, interpolating TK-TD parameters measured at the stable salinities well predicts the Cd bioaccumulation and toxicity under fluctuating salinities. To extend the model for various Cd levels, the biotic ligand model (BLM) was integrated into the TK-TD framework. The BLM-based TK-TD model was successfully applied to scenarios of simulated and monitored salinity fluctuations in estuarine waters, for which the median lethal concentrations and no-effect concentrations (2.0-3.1 µg L-1) of Cd were derived. Overall, we integrated the BLM and TK-TD models and provided a useful tool for predicting metal risks and deriving criteria values for salinity-fluctuating estuarine waters.

[A clinical study of actual corneal ablation depth in laser in situ keratomileusis].

PURPOSE: To assess the predictability of corneal ablation depth in LASIK using NIDEK EC5000 excimer laser. METHODS: Standard LASIK surgery was performed in 79 myopic patients with or without astigmatism with the NIDEK EC5000 excimer laser system.Ultrasonic corneal pachymetry was performed immediately after flap creation and after laser ablation during LASIK procedure,by which the actual corneal ablation depth was calculated.The values of actual and predicted ablation depth were compared. RESULTS: The actual ablation depth was (92.32+/-29.86)µm, the predicted ablation depth was (74.16+/-25.95)µm.The differences between them(18.16+/-14.71)µm were statistically significant(p<0.001).Linear regression suggested that the actual ablation depth correlated closely with the predicted ablation depth(r=0.87,p<0.001).The regression model was Y=18.06+1.001X.The differences remained statistically significant and were independent of the levels of preoperative corneal keratometry,absolute preoperative spherical equivalent and the preoperative central cornea thickness. CONCLUSIONS: The actual ablation depth was about(18.16+/-14.71)µm thicker than the predicted ablation depth in the NIDEK EC5000 excimer laser system. We may have to take into account this deviation in order to ensure sufficient thickness of residual stromal bed.