<P> The Air Quality Agreement is an environmental treaty between Canada and the United States . It was signed on 31 March 1991 by Canadian prime minister Brian Mulroney and American President George H.W. Bush and entered into force immediately . It was popularly referred to during its negotiations as the "Acid Rain Treaty", especially in Canada . Negotiations began in 1986 when Mulroney first discussed the issue with then - president Reagan . Mulroney repeatedly pressed the issue in public meetings with Reagan in 1987 and 1988 </P> <P> The Government of the United States of America and the Government of Canada, hereinafter referred to as "the Parties", </P>

What is the canada us air quality agreement