Beijing has vowed to regulate 75 unofficial landfills by the end of this year and another 100 next year, while bringing 250 landfills into line by the end of 2015. The pledge has come from the Beijing Municipal Commission of City Administration and Environment. The commission said it will improve leachate capacity at informal landfills. Leachate is any liquid that, in passing through matter, extracts solutes, suspended solids or any other component of the material it has passed through. "Informal landfills pose a serious environmental threat and health damage to the country if left unregulated," said Mao Da, an expert in solid-waste management at Beijing Normal University. Mao said the standard of landfills in the capital varies, and some without proper management are posing a serious threat to the environment. Without a proper landfill procedure, some buried waste will seriously pollute underground water and soil.