NEW YORK - Chemical shipments on U.S. railroads fell 9.1 percent last week, the Association of American Railroads said on Thursday.

Chemicals shipments on trains, called rail car loadings, are a measure of demand for products ranging from plastics to fertilizers.

For the week that ended Sept. 12, chemical rail car loadings fell to 25,231 from 27,760 in the year-ago period, the AAR said.

The figures often provide an early glimpse of broader trends for the chemical industry as well as manufacturing, according to analysts.

The weekly data indicated that year-to-date rail car chemical loadings have fallen 15.2 percent compared with the same period in 2008.

Rail car loadings represent about 21 percent of chemical volumes by tonnage. Trucks, barges and pipelines carry the rest.

(Reporting by Ernest Scheyder; Editing by Richard Chang)