A power plant on Missouri side of Mississippi River near Alton, Illinois.

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Factories that produce air pollution, along with soot and heavy metals, tend to be built near downwind borders.Local and state politics play a role.In choosing a site, corporations want to find locations where they will get less political blowback, study notes.

Toxic, air-polluting factories have been systematically builtat state borders so neighboring downwind states receive the brunt of the pollution, a recent study said.

According to the ,researchers at multiple universitiesstudied data at nearly 40,000 industrial facilities across the U.S. and compared it with data on prevailing wind patterns. They foundfactories that produce air pollution, along with soot and heavy metals, tend to be built near downwind borders, with the most toxic facilities located closest to the borders.

On the other hand, facilities that produce solid or liquid waste do not seem to follow that trend.

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The authors pointoutit is unclear if the aggregationof air-polluting factories near downwind bordersis intentionalbut do notethe circumstantial evidence is compelling.

"We've never really found a smoking gun where someone said 'locate here ,'" JamieMonogan, an assistant professor at the University of Georgia, told Vice. "But, you see the motivation and you see the circumstantial evidence."

The authors say "both state governments and firms have incentives to strategically locate polluting facilities where the environmental and health consequences will be borne as much as possible by residents of other jurisdictions."

"This allows them to reap the benefits of economic development while making their neighbors ," they say.

The research indicatesthe pattern of industrial location varies from state to state – but there's a significant pattern.

"States with stronger environmental programs ... evidence weaker propensity to have air polluting firms locate near downwind borders, while states that make greater use of 'smokestack chasing' economic development incentives show the opposite configuration," according to the authors. "This suggests that air polluter location is responsive to public policy."

The authors noted local and state politics play a role, and forward-looking companies realizeupwind sites are less likely to be approved by zoning boards; less likely to receive state economic incentives; more likely to draw 'not in my backyard' protests; more likely to draw in-state lawsuitsand more likely to draw regulatory penalties. Those considerations appear to ultimately determine a facility's locations.

"States and firms have incentives to locate big sources of air pollution in places where the adverse health effects will be experienced by downwind neighbors, co-author David Konisky, an associate professor at Indiana University, told weather.com. "This is a way to shift the negative burden of these facilities to people living in other states."

Konisky noted that while the U.S. Clean Air Act is intended to provide uniform air quality across the country, the decentralized nature of implementation creates challenges for meeting this goal.

"The CAA has had many successes over its four-plusdecades, but interstate air pollution remains a significant problem," Konisky said. "The strategic location of pollution sources near downwind borders is one reason why."

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