In May 2010, Chile, with serious air quality problems, became the first South American country to join the Organization for Economic Co-operation and Development (OECD). The primary Chilean Air Quality Standards are designed to protect the human health, while the secondary standards are designed to protect the ecosystems. The atmospheric contamination problem was limited to Santiago, however, many mining zones and other northern, central, and southern cities in Chile have begun to show air quality problems, with severe health consequences for the population. The annual SO 2 concentrations in the copper mining areas of the north and central regions of Chile decreased substantially from 1993 to 2009. Chile recently released a new PM 2.5 standard, which will take effect on January 1, 2012.