Hazardous levels of sewage-based bacteria have been found at beaches the Environmental Protection Department (EPD) says are clean, according to testing carried out by University of Hong Kong (HKU) researchers.
Water and sand samples collected by marine science students at Golden Beach and Clear Water Bay Second Beach contained quantities of enterococcus exceeding levels considered safe in other countries, according to the research paper published in Marine Pollution Bulletin last month.
Enterococcus indicates the presence of faecal matter which can incubate various health-threatening microbes, leading to gastroenteritis, pneumonia, hepatitis and infections of the skin, eyes and ears.
The samples were collected in September and October last year. During that period, the EPD graded the water at the two beaches as “good”, its best available rating.
Researcher Kylie Yuen Ka-lai said the results were a wake-up call. “If the government says a beach is in good condition and you can swim there, people will go for it,” she said. “But we shouldn’t trust this kind of thing so easily.”
But the WHO revised its guidelines in 2003 and now recommends screening marine water for enterococcus, which has higher resistance to salt and UV light, making it a more reliable measure of beach water contamination.
The US Environmental Protection Agency follows the WHO code, as do authorities in Europe, the UK and Australia. If US standards were followed in Hong Kong, the beaches tested would have been closed to swimmers during the sampling period and potentially for much of the year.
At Golden Beach, the EPD reported an average of 12 colony-forming units of E coli per 100 millilitres, well under its objective of 180 CFUs. By contrast, the HKU researchers found 41 CFUs of enterococcus, slightly above the US EPA’s objective of 35 CFUs.
The divergence at Clear Water Bay Second Beach was more striking. The EPD detected just 7 CFUs of E coli before it declared the beach safe, whereas the HKU researchers measured an imposing 124 CFUs of enterococcus per 100 millilitres – three and a half times the US objective.
“We cannot dance around the discrepancy,” said David Baker, research supervisor and a professor in the School of Biological Sciences at HKU. “I can’t imagine [the EPD] would refute the use of enterococcus when almost all of the scientific literature is promoting it today.”
Patrick Lei Chee-kwong, principal environment protection officer in the EPD’s Water Policy and Science Group, said the EPD has collected enterococcus data for almost five years. But the data has not been shared with the public or the scientific community and does not feed into beach water quality ratings.
Lei admitted enterococcus was tracking more strongly recently, but said there was no locally-produced evidence linking enterococcus with human illness and more research was needed. The EPD has not issued a press release on its marine water quality research since May 2010.
Hong Kong’s beaches attracted almost 10 million visitors last year. The two beaches in the HKU study are among the four that are open to swimmers all year round. Golden Beach is famed for its imported Hainanese sand, while the EPD website describes Clear Water Bay Second as “one of the most popular and finest beaches in Hong Kong”.
Limited testing by the HKU researchers found four other beaches relatively uncontaminated: the Hong Kong island trio of Repulse Bay, Stanley Main Beach and Shek O, and Butterfly Beach in the New Territories.
While the researchers used the same water sampling methods as the EPD, they also measured sedimentary bacteria, which the EPD does not. In the sands underwater at around waist depth, they found around four times as much enterococcus as in the water.
“The bacteria likes to adhere to sediments,” said Yuen. “If there is wave action or tidal action, it re-suspends the sediments. The bacteria then comes off the sediments and floats in the water column, where people are swimming.”
Despite the unsettling results, Baker said initiatives like the Harbour Area Treatment Scheme have had a positive impact on some of Hong Kong’s marine waters, and the government should view beach water quality as an opportunity for improvement.
“I think the government really shouldn’t be afraid of this, because they only stand to look good,” he said. “If they continue to invest in waste water management, and they continue to be transparent about the water quality data, then the trajectory is only going to be positive. It’s only going to improve over time.”