POLLUTION ). Coal accounts for about 20%, 15%, and 20% respectively of sulphur dioxide (SO 2 ), nitrogen oxide (NOx), and carbon dioxide (CO 2 ) emissions in Canada. Coal is also a source of heavy metals emissions. In 1994, eastern Canadian coal-burning utilities (Nova Scotia Power Inc., New Brunswick Power and Ontario Hydro) were all below their SO 2 emission limits. Emissions were 329 kt (kilotonnes), compared to a legislated limit totalling 443 kt. However, in several acid-sensitive areas of eastern Canada, even with implementation of existing programs to control SO 2 emissions in Canada and the US, sulphate deposition will continue to cause lake acidification. A stakeholders' group chaired by Environment Canada is developing a national strategy to address acidifying emissions in the post-2000 period. Another working group chaired by Environment Canada is devising guidelines for NOx emissions from coal-fired utility boilers constructed after the year 2000. The Coal Association of Canada and the Canadian Electrical Association have each agreed to participate in Natural Resources Canada's Voluntary Climate Change Action Plan and Registry program, under which signed-up organizations voluntarily reduce their CO 2 and other greenhouse gas emissions by increasing their energy efficiency. On heavy metals, Environment Canada began a process in 1995 to prepare recommendations on the management of metal and organic compounds declared toxic under the Canadian Environmental Protection Act. It should be noted that there are also positive environmental effects from coal use. Coal-fired generating stations produce large volumes of ash and waste products. Most