The study focuses on the period between 2005 and 2018 and tracks combustion emissions of various polluting compounds from various sectors, looking at every state in the contiguous United States, from season to season and year to year.
In general, the researchers find that when air pollution is generated in one state, half of that pollution is lofted into the air and carried by winds across state boundaries, to affect the health quality of out-of-state residents and increase their risk of early death.
Electric power generation is the greatest contributor to out-of-state pollution-related deaths, the findings suggest. In 2005, for example, deaths caused by sulfur dioxide emitted by power plant smokestacks occurred in another state in more than 75% of cases.
Encouragingly, the researchers found that since 2005, early deaths associated with air pollution have gone down significantly. They documented a decrease of 30% in 2018 compared to 2005, equivalent to about 30,000 avoided early deaths, or people who did not die early as a result of pollution. In addition, the fraction of deaths that occur due to emissions in other states is falling—from 53% in 2005 to 41% in 2018.
Perhaps surprisingly, this reduction in cross-state pollution also appears to be related to electric power generation: In recent years, regulations such as the Environmental Protection Agency’s Clean Air Act and other changes have helped to significantly curb emissions from this sector across the country.
The researchers caution, however, that today, emissions from other sectors are increasingly contributing to harmful cross-state pollution. . . .
They looked at multiple species of pollutants, such as sulfur dioxide, ozone, and fine particulates, from various emissions sectors, including electric power generation, road transportation, marine, rail, and aviation, and commercial and residential sources, at intervals of every hour of the year.
They first obtained emissions data from each of seven sectors for the years 2005, 2011, and 2018. They then used the GEOS-Chem atmospheric chemistry transport model to track where these emissions ended up, from season to season and year to year, based on wind patterns and a pollutant’s chemical reactions to the atmosphere.
Finally, they used an epidemiologically-derived model to relate a population’s pollutant exposure and risk of early death. . . .
For example, electric power generation has the greatest range, as power plants can loft pollutants far into the atmosphere, allowing them to travel over long distances. In contrast, commercial and residential sectors generally emit pollutants that chemically do not last as long in the atmosphere. . . .
In terms of the impact on individual states, the team found that many of the northern Midwest states such as Wyoming and North Dakota are “net exporters” of pollution-related health impacts, partly because the populations there are relatively low and the emissions these states generate are carried away by winds to other states.
Those states that “import” health impacts tend to lie along the East Coast, in the path of the US winds that sweep eastward.
New York in particular is what the researchers call “the biggest importer of air pollution deaths”; 60% of air pollution-related early deaths are from out-of-state emissions. . . .
Direct link to study article:
https://www.nature.com/articles/s41586-020-1983-8Premature mortality related to United States cross-state air pollution