Government needs to study concentrations of antibiotics in rivers
In September 2014, I led a research study into Hong Kong’s river water and the findings were published in Ecotoxicology and Environmental Safety.
We discovered that the concentrations of six typical antibiotics commonly used in humans and by vets in animals (including ofloxacin, doxycycline, sulfapyridine, sulfadiazine, sulfamethoxazole, and sulfadimidine) were high and comparable to rivers on the mainland, especially doxycycline.
At some sampling sites, the concentrations of sulfamethoxazole and doxycycline in the river water were higher than in the sewage influent.
These sites were mainly in two regions, in areas of the Kam Tin River and the Shek Sheung River, which were densely populated. Doxycycline belongs to the class of antibiotics known as tetracyclines and sulfamethoxazole belongs to the class known as sulfonamides. Tetracyclines and sulfonamides are commonly used in hospitals and livestock feeding.
The consumption of aquatic products or water from those rivers which were contaminated with antibiotics can cause human allergy and toxicity problems.
Chronic exposure to tetracycline (including doxycycline in this study), for example, could lead to steatosis (an accumulation of fat in the liver) by altering genes related to lipid metabolism and transportation.
Secondly, bacteria exposed to antibiotics in the environment may accelerate the persistence or emergence of antibiotic resistance genes which pose potential harm to both ecosystems and to human health.
The development of antibiotic resistance in bacteria in river waters could lead to bacterial antibiotic resistance among human populations.
The environmental risk assessment showed that ofloxacin and doxycycline presented a medium to low ecological risk to algae in river water in this area. For the sulfonamides detected, sulfamethoxazole posed a low ecological risk to algae in two sampling sites. Overall, 26.1 per cent of the river water samples posed a medium risk.
The government should conduct a regional cross investigation and mapping of antibiotics occurrence in river water and sediment, to set up a guideline of effluent from sewage treatment plants and farming.
Wenjing Deng, assistant professor, department of science and environmental studies, Hong Kong Institute of Education