Nguyen Tran Thanh An of District 12 is one of those.

Tuoi Tre (Youth) newspaper quoted him as saying: "One day at 11pm I was returning from Cu Chi to the city along with my wife and daughter.

"When I arrived at the street, everything was blindingly bright and I [lost balance and] fell. A bus luckily missed my family by just a few centimetres. After that I heard many people fell like me, but do not know why."

Huynh Kim Tuoc, director of the HCM City Energy Saving Centre, said the street has many high-capacity streetlights to serve the heavy traffic. But he said designers forgot one important thing: that the lights must not blind drivers.

"Traffic densities are different at 19h and 23h. It means that drivers only need adequate and not blinding light.

"This is light pollution," Tuoc warned.

"And its long-term impact is horrible. It seems there have been no studies into urban light pollution, but it is of a serious magnitude."

Le Thi Hoai Nam, who lives in Nguyen Son Street, Tan Phu District, said that she and her family are victims of light pollution who have been unable to sleep for a long time and her son and daughter are not able to focus on studying.

"At first we thought we were stressed. But when a doctor asked me if I live near signboards or buildings with high-capacity lights I was startled because around our bedrooms are signboards of karaoke parlours, restaurants, hotels.

"My doctor said electromagnetic waves from signboards and lights around my house have made my family insomniac and caused physiological disorders."

Light pollution destroys urban dwellers' health gradually.

"High capacity lights have a strong effect on people's central nervous system," Dr Phuong Loan of Sai Gon General Hospital said.

"It makes people easily angry, and in the long term skin and breast cancers are caused by light pollution.

Lighting design ignored

Pham Thanh Hung, an architect at a Japanese company, said: "Light design should always come first before any construction. However, [people] do not pay attention to this. In developed countries, regulations about lighting are very clear and all Vietnamese architects understand that."

A renowned advertising expert said: "To get permission for one outdoor signboard, a company has to furnish at least 20 documents but none of them about lighting.

"But foreign companies [in Viet Nam] adhere to strict rules about lighting and materials that are appropriate for sight."

Dr Che Dinh Ly, deputy head of HCM City's Natural Resources and Environment Institute, said: "It is time to act and consider light pollution a threat to people's health."

According to Dr Jason Pun, head of Hong Kong University's Light Pollution Study Group, in mega cities, light pollution is often several thousand times above safe levels and it means that in such cities people's health faces a threat.

"Let us restrict and even say no to electric light when it is not necessary," he said.