Scientists from the China University of Petroleum and the Qingdao Institute of Marine Geology have found that the first farmers began to pollute the seas 4 thousand years ago. The details of the study can be found on the information portal The Holocene.
Geologists analyzed sediments at the bottom of the South China Sea and found that 4 thousand years ago the level of pollution of the sea with heavy metals increased. Probably at this time, the farmers living in Hainan began to actively develop the island. In addition, the climate became colder at about the same time. This, according to scientists, contributed to the pollution. Farmers had to work hard to cultivate crops. Heavy metals were leaving the farms for the seas, which accumulated in the soil due to the use of many metal tools.
Previously, scientists found that the waters off the coast of the Iberian Peninsula began to be polluted with lead at approximately the same time interval. However, those concentrations of heavy metals were so low that they could not threaten human health, which cannot be said about today.