After three containers of chlorine gas used to treat water leaked three years ago, the Ha Giang Water Supply and Drainage Company failed to treat the hazardous gas.

The company reported that it built a big tank of limewater to hold the containers. The gas leaking from the containers would thus dissolve and not affect the environment.

However, people living in the area complained that the gas was sometimes released into the environment, affecting their health and crops.

Resident Nong Viet Khai said the white gas could easily be seen when it was released, and that it withered trees and crops in the surrounding area.

Those inhaled the gas felt difficulty breathing, said another resident, Tran Van Su.

"We hope that local authorities will soon treat the gas to help local people live and work normally," he said.

The water company's director Nguyen Vinh Phu admitted that chlorine gas was sometimes leaked into the environment. He apologized to households living in the surrounding area and said the company would put more lime into the tank to help treat the gas, adding that local residents should stay away from areas where the gas was concentrated.

Phu said it was difficult to treat the gas because there were no hazardous waste treatment facilities in the province. The company asked for help from the provincial Department of Natural Resources and Environment but received none, he said.

Hoang Minh Tien from the provincial Environmental Police Office said the local police did not receive any environmental protection commitment from the company. Under current regulations, the company was supposed to commit to treating the gas when buying it. However, the company failed to treat the gas when it leaked and let the situation remain unresolved for a long time, affecting local residents.

Environmental police would work with the provincial Department of Natural Resources and Environment to investigate the case and strictly punish any violators, he added.

Deputy Director of the department Do Thai Hoa said the department would report the case to the provincial People's Committee to seek an appropriate solution and set a deadline for the company to deal with the gas.

When added to water, chlorine acts as a disinfectant, killing bacteria and other microbes that can spread diseases to humans. However, breathing a certain amount of chlorine can adversely affect the human respiratory system, causing symptoms such as coughing, chest pain and water retention in the lungs. Chlorine also irritates the skin and eyes. The effects of chlorine on human health depend on the amount of chlorine and length and frequency of exposure.