Figure 1. View of Pollutant Sources and Effects
©1997, International Joint Commission
1.0 OVERVIEW
In this 23rd Progress Report, as in the last several reports, the International Air Quality Advisory Board considers the sources, ambient concentrations, effects and available management tools for what are often called the primary or criteria pollutants (sulphur dioxide (SO2), nitrogen oxides (NOX), particulate matter (PM), and ozone). Concerns regarding carbon dioxide, a greenhouse gas, and volatile organic compounds (VOCs), are also reviewed.
Sulphur dioxide and sulphates have a role in acid rain. While sulphur dioxide emissions have been reduced significantly in the United States and Canada over the last 15 years, the associated environmental insult has not been eliminated.
Nitrogen oxide emissions in North America, the other principal component of acid rain, notwithstanding increased controls over the past several years, and more stringent requirements in the next several, are predicted to increase after the turn of the century. Precipitation in sensitive portions of our two countries remains sufficiently acidic to preclude ecosystem recovery, and indeed to perhaps do further damage. The Board offers to provide a more extensive review of this situation in subsequent reports.
Sulphate also forms a significant portion of fine particulate matter (diameter less than 2.5 microns), which is associated with loss of visibility, particularly noticeable in park lands, and respiratory distress in humans. This size of particle is the subject of regulatory activity and reflection in both countries.
Nitrogen oxides are a precursor, along with VOCs, to the formation of ozone, a pollutant which reaches concentrations in various transboundary regions producing a discernable negative effect on the otherwise healthy individuals engaging in vigorous exercise, and pronounced distress in the sensitive portion of the population.
In the early 1970's, the same numerical goal for ambient ozone was established in both the United States and Canada (.08 ppm over one hour). Subsequently a standard of .12 ppm over one hour was introduced in the United States. During this time, however, the United States has been more aggressive in the development and implementation of control programs to attempt to address excess ozone concentrations.
In recognition of the negative effects associated with such concentrations, the U.S. Environmental Protection Agency is now considering an ozone standard (.08 ppm over 8 hours) closer to, but not identical with, the current Canadian objective. In response to established health impacts, Canada may further tighten its .08 ppm/one hour objective.
With regard to climate change, the accumulated weight of evidence indicates that human activities are contributing to significant change in the global climate, with definite implications for humankind. Carbon dioxide is a principal greenhouse gas; much of its production is the result of human activity.
Indeed, nitrogen oxides and carbon dioxide (CO2), and, to a lesser extent, sulphur dioxide, are associated with transportation (as is VOC production) and electrical energy generation (particularly coal fired utilities) sectors. Figure 1 is a simplified illustration of the sources and products of these pollutants in the environment.
It is clear that further reduction in emissions from these two sectors, and others, will be necessary if ecosystem damage is to be curtailed and ecosystem quality is to be preserved and sustained.
Consideration also is given to a number of regional, largely bilateral air management initiatives, ranging from co-operation between Washington State and the province of British Columbia, to transboundary efforts in the Northeastern States and the Atlantic Provinces. The effectiveness of the Paso del Norte Task Force in the El Paso Texas/Cuidad Juarez Chihuahua bilateral region, other United States/Mexico initiatives and the work of the Commission for Environmental Co-operation are also examined.
Figure 1. View of Pollutant Sources and Effects
©1997, International Joint Commission