Chemical shipments on U.S. railroads rose 13.1 percent last week, the Association of American Railroads said.

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

For the week ended June 12, rail car chemical loadings rose to 28,598 from 25,287 a year earlier, 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 year-to-date rail car chemical loadings have risen 12.7 percent compared with the same period in 2009.

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