Occurrence and stability of PCMX in water environments and its removal by municipal wastewater treatment processes.

Para-chloro-meta-xylenol (PCMX) is a synthetic antiseptic used extensively to control the spread of germs and viruses, and as a result, enormous amount of PCMX could be discharged to water environments through drainage. To investigate the extent of PCMX contamination, water samples were collected from rivers and coastal waters in Hong Kong, and PCMX concentrations were determined by a newly developed method using liquid chromatography-tandem mass spectrometry combined with stable isotope-dilution. We discovered widespread PCMX pollution in the water environment. Then, we revealed for the first time that PCMX in wastewater is not effectively removed by chemically enhanced primary treatment (CEPT), one of the wastewater treatment processes used in Hong Kong (∼75% of wastewater) and other megacities around the world. This suggests that the CEPT effluent or the primary treatment effluent is an unintended continuous source of pollution for PCMX in water environments. Finally, we found that PCMX was relatively stable in the water environment and could pose a risk to aquatic organisms. These findings underscore the importance of raising public awareness of the environmental consequences from overuse of PCMX-based disinfectants and the need to reevaluate the various wastewater treatment processes in removing PCMX.

Thioproline Serves as an Efficient Antioxidant Protecting Human Cells from Oxidative Stress and Improves Cell Viability.

Oxidative stress is associated with the pathophysiology of many degenerative human diseases, including Alzheimer's disease, atherosclerosis, Parkinson's disease, and cancers. We discovered in our previous study that thioproline (SPro), a proline analogue, is generated in oxidant-exposed cells. With the prior observation that SPro served as an efficient nitrile trapping agent, we tested in this study the hypothesis that this oxidative stress generated cysteine-formaldehyde adduct, SPro, may serve as an antioxidant protecting cells from oxidative stress. Interestingly, results showed that HeLa cells cultured in SPro-supplemented culture media are more tolerant of oxidative stress, indicated by a dosage-dependent increase in cell viability. Investigation of the molecular mechanism of the observed increase in cell tolerance to oxidative stress revealed SPro acting as an effective antioxidant by sacrificial oxidation. Results also showed that SPro had been incorporated into cellular proteins and induced changes in protein expression profiles of treated cells. Despite being yet to determine the participation of individual factors to the observed increase of cell tolerance to oxidative stress, this study sheds light on the potential use of SPro as a dietary supplement for protecting humans from oxidative stress-associated degenerative human diseases.