The air quality in a district in Quanzhou, in eastern China's Fujian province, where almost 7 metric tons of petrochemicals leaked on Sunday, contaminating the air and water, has improved steadily in the days since, the local environmental protection bureau said on Thursday.

A hose from an oil tanker owned by Fujian Donggang Petrochemical Industry ruptured when it was offloading the petrochemicals at a wharf inQuanzhou's Quangang district at 1:14 am on Sunday, Beijing News reported.

The results of an early investigation into the accident, which leaked 6.97 tons of toxic C9 aromatics into the water, showed it was caused by wear and tear of the hose. Aromatics are hydrocarbon chemical products typically derived from the oil refining process, with C9 meaning the products' chemical formulas contain nine carbon atoms.

After the spill, local farmers reported a foul odor in the area, and local fish farms and fishing equipment were contaminated by an oily, yellowish-brown compound. Several locals went to hospitals complaining of dizziness, sore throats and tight chests, and one 49-year-old farmer, surnamed Xiao, was hospitalized for possible pneumonia, Beijing News said.

Science and Technology Daily, which said the compounds were flammable and toxic but not lethal, strongly advised people against breathing in large amounts of the chemical or eating contaminated fish or vegetables.

The bureau said the cleanup of the water had been completed on Sunday afternoon, after more than 600 personnel and 100 ships were mobilized for the cleanup effort.

Air quality also improved gradually as the volatile organic compound level, which measures the amount of chemical in the air, dropped from 0.43 micrograms per cubic meter on Sunday afternoon to around 0.13 mcg per cu m on Wednesday, the bureau added.

Any level below 4 mcg per cu m is considered safe according to petrochemical industry standards, it said, adding it will continue to monitor the situation, send samples for safety checks, and handle the incident in accordance with laws and regulations.

The district's bureau of agriculture, forestry and water said it had issued an emergency notice on Sunday to local farmers, warning them not to harvest, sell or eat marine products from the area, and wait for safety test results from the authorities.

Beijing News said local fish farmers had suffered losses ranging from tens of thousands of yuan to more than 1 million yuan ($144,300) due to the pollution. Fujian Donggang Petrochemical Industry apologized for the spill in a statement released on Sunday and promised to compensate them for their losses.