Lead levels at nearly 80 times World Health Organisation safety standards were found in water samples from the public housing estate where the city's tainted water scandal began, a concern group revealed after its latest round of tests.
A water sample from Yan Ching House in Kowloon City's Kai Ching Estate showed levels of the heavy metal at 793 micrograms per litre in tests by the Lead in Drinking Water Concern Group, conducted in July and last month. Of the 704 households tested, water from 328 flats in all six blocks of the estate had excessive lead levels - with 19 exceeding the WHO standard of 10 mcg/l by 10 times or more.
Completed in 2013, Kai Ching was the first public housing estate to have excessive lead levels found in its water in tests by the Democratic Party in early July.
The government then confirmed that lead content in seven water samples taken from the estate exceeded WHO standards, which led to city-wide tests that exposed tainted water elsewhere.
Of 25 Kai Ching residents who underwent blood tests sponsored by the concern group, three - two elderly people in their 80s and a middle-aged woman - had excessive lead levels in their blood, ranging from 10.5 micrograms per decilitre to 18.4 mcg/dl. The safety standard for lead in blood is 5mcg/dl.
According to Yuki Leung Yuen-ting, convenor of the concern group, the water tests were funded by the Hong Kong Kowloon City Industry and Commerce Association, while the blood tests were funded by Beijing-loyalist lawmaker Ann Chiang Lai-wan.
"Ever since the lead-in-water incident broke out at Kai Ching Estate in early July, residents have been harmed both physically and psychologically," said Leung, who works there. "We hope residents could be compensated, such as by being exempted from rent and water fees."
To date, 11 public housing estates, plus private residential development The Caldecott in Cheung Sha Wan and three primary schools - St Thomas' Primary School in Sham Shui Po, St Francis of Assisi's Caritas School in Shek Kip Mei and Baptist Rainbow Primary School in Wong Tai Sin - have reported excessive lead levels.
Government test results show at least 126 residents from the affected public estates have excessive lead levels in their blood.
Speaking on Thursday, Secretary for Food and Health Dr Ko Wing-man said starting next Saturday quotas for blood tests will be reserved for two groups of people: residents of affected public housing estates and pupils of kindergartens at which results of water sampling tests exceed the WHO standard.
Additional reporting by Lai Ying-kit