The owner of a tanker truck that accidentally leaked small amounts of a cancer-causing chemical into the Huangpu River on Wednesday has been fined for overloading the truck, officials announced yesterday.

　　Authorities said an examination of the leak shows it was too small to cause any serious pollution of the river.

　　The truck broke down while climbing a small slope to get to shore from a ferry. About 15 liters of liquid styrenes leaked out of unsealed tubes on the inclined tanker.

　　Lu tao, an agent from the marine police bureau, said the 15-ton tanker was carrying 30 tons of styrenes.

　　The truck, which is registered in Jiangsu Province, was delivering freight to a chemical factory in Pudong at the time of the accident.

　　It broke down while moving on a 25-degree-slope ferry board connecting to the river bank at the Nenjiang Road ferry dock around 8:45am.

　　It is difficult for a large tanker truck to drive over such a slope; however, the leak wouldn't have happened if not for the extra load, police said.

　　"If only the container had carried a bit less liquid, the leak could have been avoided," Lu said.

　　Police impounded the truck after the accident, but released it yesterday after the owner paid a fine of 500 yuan (US$60) for overloading. The local maritime safety administration said experts tested samples of nearby waters and noted no sign of chemical pollution.

　　Styrenes is a lighter-than-water chemical liquid with an irritating smell that doesn't dissolve well in water.

　　It has been linked to cancer.

　　Considering the small size of the leak and that it didn't happen close to any tap water sources, authorities claim the accident will have no long-term effect on the environment.