BEIJING, April 17 -- About 16.1 percent of soil in the Chinese mainland is polluted, an official report said on Thursday.

About 19.4 percent of farming land is polluted, said the report issued jointly by the Ministry of Environmental Protection and the Ministry of Land and Resources.

The general condition of the land is "not optimistic" as the quality of farming land is worrying and deserted industrial and mining land suffers serious pollution, according to the report.

It was based on a survey conducted from April, 2005, to December last year on about 630 square km of land across the country, except Hong Kong, Macao and Taiwan.

The pollution has been caused by complicated factors over a long period of time. "The main pollution source is human industrial and agricultural activities," the report said.

In breakdown, 11.2 percent of the surveyed land suffers slight pollution, while 1.1 percent is severely polluted.

About 2.3 percent of the land is lightly polluted and 1.5 percent suffers medium pollution.

Some 10 percent of woodland and 10.4 percent of grassland is polluted, the report added.

About 82.8 percent of the polluted land is contaminated by inorganic materials and the top three pollutants are cadmium, nickel and arsenic.