The government should further supervise and control hazardous waste discharged by enterprises and enforce drainage information disclosure regulations, experts said in response to a recent landfill scandal in Beijing.

KB (Beijing) Autosys Co Ltd, a South Korean company that produces auto parts in Miyun county, dumped hazardous waste directly on farmland and in forests for three years, seriously polluting the soil and air of surrounding villages.

Instead of disposing of the waste properly, the company simply dumped it in about 30 holes, the average diameter of which was 30 meters.

The waste was mostly powder from the leftover bits and pieces of the brake blocks, according to Jiang Huanhuan, an employee at the logistics department of KB (Beijing) Autosys.

The case aroused public fury after media brought it to light.

"Many enterprises with heavy hazardous waste in the city are not resorting to licensed companies to dispose of their waste but rely on private ones because of the lower cost, which results in pollution in soil, water and air," said Mao Da, an expert in waste management at Beijing Normal University.

"With poor corporate self-discipline and loose government supervision, the environment as well as public health are falling victim to hazardous-material discharges."

Jiang said his company is a victim as well. "We used a private recycling company for waste treatment and did not realize they were not licensed and had been dealing with the waste this way," he said.

Jiang said the company has been cooperating with a licensed waste treatment enterprise since the end of 2011, after negotiations with residents.

Liu Yuying, a resident of Miyun, filed a lawsuit against the company in 2012 after finding the land she rented has numerous holes with unknown black powder inside them.

"At first I thought people were disposing of garbage, but I was told later the garbage is poisonous," she said. "I can't build my vegetable greenhouse in a land of poison."

Mao said there is no way the company had no idea its hazardous wastes were treated this way, as no licensed waste treatment company will receive the hazardous waste for free.

According to the Beijing Environmental Protection Bureau's pollution prevention department, the city has more than 10 licensed waste treatment companies.

"It costs a lot for a company to have their hazardous waste disposed of at a licensed treatment company, almost 10 times more than kitchen waste," Mao said. "The high cost is the major reason many companies with heavy hazardous discharges avoid their responsibility and resort to illegal workshops or individuals to have the scrap dealt with."

Mao said the illegal workshops usually dump hazardous waste in a hole without any processing, which imposes a serious risk to the soil, water and air.

For example, the powder of leftover bits and pieces buried in the soil was mainly organic resin and antimony sulfide, the latter of which is a poisonous heavy metal that could threaten people's health, he said.

It is not known how much effect the hazardous waste will have on the environment now, but the bureau will further strengthen supervision of such companies, said Duan Qiliang, director of the county's environmental protection bureau.

Dong Liangjie, a former environmental scientist at the University of Hawaii, said the soil pollution is like an environmental time bomb.

The heavy-metal pollution of soil, once imposed, will have a tremendous negative effect and take a long time to repair, he said.

"Prevention is much more effective in bettering the environment than repair after the fact," he said.

zhengxin@chinadaily.com.cn