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Environment Magazine September/October 2008


January-February 2010

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Editors' Picks - January/February 2010

International Air Pollution Transport: Impacts on the United States
Committee on the Significance of International Transport of Air Pollutants, National Research Council, Global Sources of Local Pollution: An Assessment of Long-Range Transport of Key Air Pollutants to and from the United States (Washington, DC: National Academies Press),

While air pollution has traditionally been thought of as a local issue, the increasing scope of human impacts on the environment has prompted the recognition that we all share one atmosphere. A recent National Research Council (NRC) study emphasized this fact, concluding that long-range transport can have significant impacts on air pollution in the United States. Co-sponsored by the U.S. Environmental Protection Agency, the National Oceanic and Atmospheric Administration, the National Aeronautics and Space Administration, and the National Science Foundation, the study examines four types of air pollutants: ozone and its precursors; particulate matter and its precursors; mercury; and persistent organic pollutants (POPs). Ozone and particulate matter can cause respiratory and cardiovascular effects including death, mercury is a potent neurotoxin, and many POPs can have carcinogenic or endocrine-disrupting effects. Pollutants from foreign sources can increase pollutant concentrations and deposition in the United States, affecting human health and the environment.

The report provides an extensive survey of the current knowledge of the pathways between pollutant emissions and concentrations or deposition. It focuses on how pollutants travel across continents, and how sources of pollution can be identified. Pollutants that remain for 3–4 days in the atmosphere can have continental-scale impacts, while those that remain 1–2 weeks can affect distant continents, and longer-lived pollutants cause hemispheric or global concerns. At the latitude of the United States, prevailing winds are from west to east, so the United States is affected by Asian pollution and in turn affects European air quality.

The NRC study details two mechanisms for long-range transport: one in which pollution plumes rise from their source and travel aloft before subsiding to the surface in a receptor region, and another in which pollution is well-mixed and raises baseline pollutant levels. While the study concluded that significant quantities of all four pollutants are transported over long distances, uncertainties remain in fully characterizing their international transport pathway, due to uncertainties in emission sources, chemical and phase transformations in the atmosphere, and poorly-characterized meteorology.

While many air pollution concerns, especially for ozone and particulate matter, are caused by local emissions, international contributions are non-negligible, and the relative contributions of international sources is likely to increase in the future. For example, violations of the U.S. ozone standard are primarily caused by domestic emissions, but they are augmented by an increase in the baseline level of tropospheric ozone in the Northern Hemisphere (which has increased by 40–100 percent since industrialization). As regulations become stricter in the United States and emissions increase in rapidly-developing Asian regions, the role of international pollution will become relatively greater.

Mercury and POPs are pollutants of global concern due to their long lifetime in the atmosphere. There has been less scientific research on mercury and POPs transport, and their lower concentrations in the atmosphere make them more difficult to measure. For mercury, the report highlights the global cycling of mercury among land, ocean, and atmosphere and the long-term nature of mercury contamination. For POPs, the report notes that while atmospheric concentrations of some historically-emitted POPs (such as pesticides that have since been phased out) have declined, others (such as combustion-generated compounds and persistent chemicals currently in use) are increasing.

The committee concludes by suggesting priorities for additional research into characterizing pathways of international transport, including improved emission scenarios, monitoring data, satellite observations, and chemical transport modeling. While extremely thorough in its summary and recommendations on tracing the pathway from pollutant sources to distant concentrations and deposition, the report spends less time on connecting these pathways to impacts. From a policy perspective, the key question is how to use information on transport pathways to minimize damages to human health and the environment. The report summarizes the few studies that have attempted to connect long-range transport to impacts on mortality for two of the pollutants, ozone and particulate matter, but more are certainly needed. A future assessment could provide more targeted priorities for research that would be useful for air pollution policy makers who are designing regulations from local to global levels.

Noelle Eckley Selin
  Engineering Systems Division, Department of Earth, Atmospheric and Planetary Sciences,
       Massachusetts Institute of Technology. Cambridge. MA

Real-Time Climate Change Adaptation

Ford, J.D., Gough, W.A., Laidler, G.J., MacDonald, J., Irngaut, C., Qrunnut, K. 2009. Sea ice, climate change, and community vulnerability in northern Foxe Basin, Canada Climate Research 38 (2), pp. 137–154

There is widespread and growing concern in both academic and policy arenas about vulnerability and the need to adapt to climate change. Much of this concern is being expressed in anticipation of the effects of changing climate regimes in the future; specifically, how can we prepare ourselves to best deal with uncertain consequences? A recent article in Climate Research is noteworthy for presenting a real-world, retrospective case study on the ways in which an indigenous Igloolik Inuit community has adapted to climate change as it has been unfolding in the region and impacting upon their day-to-day lives.

Using both quantitative analysis of sea-ice conditions and qualitative analysis of focus groups and interviews, the authors take the year 2006 and use it “as a lens for understanding determinants of vulnerability” and to “characterize adaptive capacity”. The year 2006 was an anomalous ice year, and this is significant because it is expected that these anomalous conditions will become the norm, rather than the exception. The authors explore the local residents' knowledge of the sea ice conditions in that year, as well as their interpretations and experiences of change over time.

Interestingly, 2006 represented a turning point in the Inuits' own understanding of changing ice conditions, as comparisons with earlier interview data showed that was the year that residents accepted that climate change was responsible for the patterns they were observing, rather than “normal” variability. The authors examine the multiple factors—both climate-related, and not climate-related—that affected the Inuit people's vulnerability to the physical and cultural risks posed by changing sea ice. This generates a multi-faceted picture of vulnerability and adaptation, with a range of responses from carrying your satellite phone in your pocket, rather than on your snowmobile (learned when the snowmobile fell through thin ice), to halting hunting seasons due to the unsafe condition on the ice for travel. Indeed, the authors note that despite the poor ice conditions, “A combination of risk management, avoidance, and sharing strategies, facilitated by Inuit knowledge, flexible local institutions, and sharing networks, enabled the moderation of increased physical risks of using the ice in fall 2006.” The authors' analysis also pointed to more far-reaching changes, such as increased reliance on store food as “country food” became less accessible; and increased demand (and rising prices) for gasoline as hunters needed to travel farther to reach target populations. Both of these imposed additional vulnerability on those without cash resources.

Through this in-depth examination of vulnerability and adaptation as it is playing out in the Igloolik community, the authors confirm that vulnerability is exacerbated when multiple stressors coincide. However, on a more hopeful note, they also describe how rapid, robust adaptation can take place. Amidst the doom and gloom of future climate uncertainties, it is reassuring to learn that plain-old learning from experience still applies—and perhaps applies more than ever.

Lorrae van Kerkhoff
  Fenner School of Environment and Society, ANU College of Medicine, Biology and Environment,
       The Australian National University. Canberra. Australia


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