WASHINGTON, June 19 -- The U.S. Department of Health and Human Services' Food and Drug Administration issued the following warning letter to Chang and Son Enterprises Inc.: * * * To: Mr. Sidney Chang, President, Chang and Son Enterprises, Inc., 301 River Road, Whately, MA 01093, United States Dear Mr. Chang, The United States Food and Drug Administration (FDA) analyzed the environmental sample identified as sample 1245959, which consisted of 15 environmental swabs collected on December 20, 2  more