Is perchlorate also found naturally in fertilizer?
Yes, since the early 20th century Chilean nitrate fertilizer containing naturally-occurring perchlorate has been widely used in American agriculture. Current amounts of Chilean nitrate fertilizer products being shipped and used in the United States are substantial. According to the Foreign Trade Division, U.S. Census Bureau, the amounts of sodium nitrate imported from Chile into U.S. ports in 2001 was 88,150 metric tons. Specific to California, Chilean nitrate fertilizer containing perchlorate has been widely used since 1923; and between 1923 and 1998, the reported usage of sodium nitrate in California was 477,061 metric tons. Though the quantities used today are smaller than the amounts applied earlier in the century, the use of Chilean nitrate fertilizer in California remains substantial. Most recent data (2000 U.S. Department of Census) indicates more than 6,600 tons of Chilean nitrate fertilizer was imported to California that year.
