"The North American Agreement on Environmental Cooperation, one of two side agreements to the NAFTA (the other a labour cooperation agreement), was signed by Canada, Mexico and the United States in August 1993 and came into force in January 1,1994. The NAAEC was developed to support the environmental provisions of the NAFTA by establishing a level playing field with a view to avoiding trade distortions and promoting environmental cooperation." (Quoted from article)