Emissions causing acid rain have been cut in half and emissions causing smog by one-third in the border region of Canada and the United States over the past 20 years, Canadian Environment Minister Peter Kent said Monday.

Marking the 20th anniversary of the Canada-U.S. Air Quality Agreement, Kent said that the agreement has significantly reduced acid rain and smog.

In Canada, emissions of the key pollutants that contribute to smog, acid rain and poor air quality have seen significant declines since 1990.

Emissions of sulphur oxides (SOx) declined by about 54 percent, mainly due to reductions from base metal smelters which were down 72 percent and fossil fuel-fired electricity generating utilities which decreased by 45 percent.

Since the addition of the Ozone Annex to the agreement in 2000, Canada has been able to reduce nitrogen oxides emissions by a third in the southern and central Ontario and southern Quebec transboundary region defined under the agreement.

"The combination of these initiatives has also resulted in particulate matter emission reductions of 34 percent," Kent said.

Particulate matter is a major contributor to human health affects and has been linked to respiratory illnesses such as chronic bronchitis and asthma, to cardiac illness, and to premature death.

Kent said the Canada-U.S. Air Quality Agreement provides an example of successful bilateral cooperation that has achieved tangible progress in improving the environment.

"Canada is looking forward to continuing its bilateral cooperation with the U.S., and to resolving the environmental challenges that face our countries," he concluded.