Lehigh Hanson Inc, the U.S. unit of Heidelberg Cement AG (HEI), has pledged to achieve required mercury standards a year ahead of a 2013 deadline. However it has said that the rules have to be relooked at. Lehigh is among companies lobbying for legislation being debated in the Republican-led House that would require the Environmental Protection Agency to scrap and rewrite regulations on cement plants, one of the biggest sources of toxic mercury emissions. Meeting the EPA’s deadline would cost $3.4 billion and may lead to shutting down 18 of about 100 US cement plants, according to the Portland Cement Association. The EPA says the cost would be no more than $950 million, and environmental organizations say the industry’s claims are belied by actions such as Lehigh’s plans in Maryland. Cement plants melt limestone and other minerals to go into concrete, used in roads, bridges and buildings, at temperatures that can exceed 3,000 degrees Fahrenheit (1,649 degrees Celsius), generating mercury pollution that ranks second behind coal-fired power plants, according to the EPA. Mercury, typically ingested by eating contaminated fish, poses the biggest risk to fetuses and children, in whom it can cause long-term damage to thinking, memory and the nervous system.