In May 1984 Senator Frank Ferguson, a senior member of the Alaska State Legislature, asked the University of Alaska-Fairbanks to sponsor two international symposia on the phenomenon known as Arctic haze. An appropriation was provided, and Prof Glenn Shaw began immediately to implement this request, convening a session in October 1984 in cooperation with the northwest meeting of the American Association for the Advancement of Science. Dr David Drewry attended this meeting and graciously offered the services and facilities of the Scott Polar Research Institute of the University of Cambridge as the site for the 1985 international symposium on Arctic Air Pollution. The Arctic is one of those regions of the world that has long fascinated both men and women. It has invited the explorer, it has stimulated the soul of the poet, it has intrigued the scientist, it has challenged the industrialist, and it has engendered awe in those populations unfamiliar with its character and essence. At the same time, for centuries the Arctic has served as home to a hardy population of indigeneous people who have learned through the years that it offers them a very special quality of life. These people, although separated artificially by our geopolitical boundaries, have evolved a culture and value system that operates in harmony with the land they inhabit. They have come to understand the fragility of its nature and that, because of its intense extremes, small infusions of non-native substances may have larger-than-normal impacts of wide reach.

An International Symposium on Arctic Air Pollution was held at the Scott Polar Research Institute, Cambridge, England, 2–5 September 1985. The conference, sponsored by the State of Alaska through the University of Alaska at Fairbanks, involved participants from the circumpolar region in discussions about the location of pollution sources and transport pathways, climatic influences of Arctic air pollution, and possible effects on human health. On the final day participants considered issues of international scientific cooperation and state responsibility; the latter topic included the difficult subject of international liabilities regarding the transfer of pollutants across international boundaries. In view of its multinational, even multi-continental character, the problem of Arctic air pollution is perhaps the quintessential example of such transferral and its attendant problems. This symposium volume contains edited versions of the papers presented at the four-day meeting in Cambridge, and the conclusions and recommendations adopted by consensus among the participants. This was not the first symposium devoted to the phenomenon of Arctic air pollution. Indeed, the first conference during which the subject of Arctic haze was discussed was held in Norway in 1977. At that conference it was agreed to try and set up a loosely coordinated, informal Arctic Chemical Network to share data on atmospheric chemistry. In retrospect this informal agreement represented a superb example of unselfish international cooperation.

This contribution was invited because I recently served on a National Research Council Committee which considered and wrote a report on the Epidemiology of Air Pollution. The report was to be released on September 1 1985, and I intended to discuss its conclusions and apply them to the problem before us. The report had not been officially released, so I spoke instead about issues discussed during the committee's deliberations that were likely to be of interest to this group, and are pertinent to future studies in Alaska.

This group is addressing one of the most important issues debated by that National Research Council Committee: is today's ambient air pollution damaging human health, and will ambient pollution be more or less harmful in the future? The role of epidemiology in getting answers to those questions was equally important to us and may be important for those in this conference who will act upon one or more of our recommendatons.

We asked ourselves at the outset whether one comprehensive longitudinal study could be designed to answer the most important health effects questions. The answer was an emphatic ‘no’. There was an equally emphatic ‘no’ to the question of a study or studies to establish safety. Evidence of safety is not just the converse of evidence of risk, and safety is much harder to demonstrate than risk. Whatever the size and rigor of population studies with negative results, they are virtually useless in assuring safety in other populations and circumstances.

ABSTRACT. A strong and persistent air temperature inversion at ground level, resulting from outgoing radiation, is a feature of Arctic and sub-Arctic regions. In sheltered valleys the lowest air layers become extremely stable and prone to pollution. Temperature gradients of 30°C per 100 m are common in the lowest 50 m. The stable air structure extends 1 or 2 km upward from the surface and permits transport of pollutants from mid-latitudinal sources in sheet-like layers across the Arctic with negligible vertical dispersion. This produces widespread Arctic haze, most effectively in winter and early spring during cold, dry periods when the air is stable and well-stratified, and ending in April when conditions become turbulent and moist. Considering the distances involved, the concentration of pollutants in the haze seems surprisingly high, but it is a natural consequence of exceptionally stable air. Urban haze is most intense during December and January, when the inversions are undisturbed even at midday: pollution levels in a small community like Fairbanks during winter can equal or exceed those of large industrial, urban centres with populations two orders of magnitude larger, such as Detroit, Los Angeles or New York. Local winter problems become especially acute at latitudes north of 60° in continental regions such as Siberia, interior Alaska and Canada.

ABSTRACT. Early in this century it was recognized that large doses of ionizing radiation could injure almost any tissue in the body, but small doses were generally thought to be harmless. By the middle of the century however it came to be suspected that even the smallest doses of ionizing radiation to the gonads might increase the risk of hereditary disease in subsequently-conceived offspring. Since then the hypothesis that carcinogenic and teratogenic effects also have no threshold has been adopted for purposes of radiological protection. It is estimated nevertheless that the risks that may be associated with natural background levels of ionizing irradiation are too small to be detectable. Hence validation of such risk estimates will depend on further elucidation of the dose-effect relationships and mechanisms of the effects in question, through studies at higher dose levels. In contrast to the situation with ionizing radiation, exposure to natural background levels of ultraviolet radiation has been implicated definitively in the etiology of skin cancers in fair-skinned individuals. Persons with inherited defects in DNA repair capacity are particularly susceptible. Non-ionizing radiations of other types can also affect health at high dose levels, but whether they can cause injury at low levels of exposure is not known.

ABSTRACT. Airborne measurements of the absorption rate of solar radiation by arctic haze indicate atmospheric heating rates of 0.15 to 0.25 Kday−1 (24 hr weighted averages) at latitudes between 72.6° and 74°N in early spring (15 March—4 April 1983). Haze interacts with solar radiation to alter the radiative balance of the atmosphere– surface system, generally resulting in more solar energy being absorbed by the atmosphere and less by ground, ice or water. Planetary albedo is also affected, increasing for haze over water and decreasing for haze over ice. Haze interaction with infrared (planetary) radiation has not been measured, though the infrared component represents a most important contribution to overall energy balance. Calculations provide some information, but experimental evidence is needed both to validate the calculations and because of the enhanced concentration of greenhouse gases measured in the haze layers. Cumulative deposition of black carbon over the surface produces a change in optical properties of the ice, which may result in increased surface temperatures and accelerating ice melt. To evaluate its consequences, experimental evidence of the magnitude of this effect is needed. An extended monitoring program is suggested. Climatic effects of changes in energy budget depend on spatial and temporal properties of the haze layers, which need to be examined more thoroughly.