Natural resources include peat deposits, small quantities of oil and natural gas, granite, dolomite (limestone), marl, chalk, sand, gravel, and clay. About 70% of the radiation from neighboring Ukraine's 1986 Chernobyl nuclear disaster entered Belarusian territory, and about a fifth of Belarusian land (principally farmland and forests in the southeastern regions) was affected by radiation fallout. The United Nations and other agencies have aimed to reduce the level of radiation in affected areas, especially through the use of caesium binders and rapeseed cultivation, which are meant to decrease soil levels of caesium-137.