A new study looks at air pollution and its effects on premature deaths in the United States. Premature deaths    1     (define) as those that take place before the average age of death.

Researchers found that half of all such deaths related to air pollution    2     (result) from pollution that came from another state. The study is the first     3    (examine) how pollution crossing state lines affects early deaths .

Worldwide, an    4    (estimate) 4.2 million premature deaths are linked to outdoor air pollution. Most of those deaths are from heart disease, stroke and lung disease, as well as acute breathing infections in children.

Efforts to deal with outdoor air pollution have    5    (large) centered on relationships between local sources of pollution and local air quality.    6       Barrett and other researchers found that, in the United States, cross-state pollution is a major concern.

The computer model looked at the atmospheric chemistry processes and weather conditions over    7    11-year period. The researchers then examined how each of the lower 48 states affects pollution and people's health in every other state.

The team found electric power plants    8    release sulfur dioxide (二氧化硫) were the biggest    9    (contribute) to deaths related to pollution from other states. In 2005, sulfur dioxide from power plants was involved    10    75 percent of cases of premature deaths from out-of-state pollutants.