Citing concerns about air quality, the American Lung Association of New York State Wednesday joined the coalition fighting St. Lawrence Cement’s plans to build a cement plant in Columbia County.  St. Lawrence wants to close a 1960s-era cement plant in Catskill, Greene County, and build a US$320m plant with three times its capacity across the Hudson River in the City of Hudson and Town of Greenport.  Compared with the old plant, the new plant is projected to reduce emissions of several pollutants, including sulfur dioxide, which causes acid rain, and lead and mercury, which can be toxic.  But it could increase emissions of volatile organic compounds and nitrogen oxides, which combine in sunlight to create ozone pollution. Tiny particulates that are linked to lung disease also may increase.