Those unenthusiastic about the prospect of millions of tons of coal being shipped through the Pacific Northwest en route to Asian markets should be heartened by the stock prices of Peabody Energy.Analysts suggest the coal mining company is a canary in the you-know-what as its stock prices dropped 4.6 percent Friday on a report that the Asian demand for coal might not remain as robust as it now is.As reported by Bloomberg and others, the report comes from Deutsche Bank AG and suggests that Chinese coal demand could drop by 18 percent by 2015 if the country takes serious measures to curb air pollution. Such a drop would render China a net exporter of coal, which it was until 2008.Deutsche’s report is based on a scenario that may well not play out. But the fact that Wall Street is taking the report seriously by way of dumping coal stocks should give it some credence (the Motley Fool called Peabody one of Friday’s three worst stocks). The fact that China is taking a serious look at environmental regulations should finally put to rest that old canard that China will overcome the U.S. because they don’t care about air quality or other environmental concerns.American regulations and a new-found love for natural gas energy (yay fracking!) has put domestic coal markets in death spiral. With 44 percent of coal being mined in Wyoming and Montana, ports in Oregon and Washington — with the access they give to Asian markets — represent the American coal industry’s best chance at staying viable.Now, even that seems in doubt, and it has nothing to do with arguable concerns about coal dust in Queen Anne.