The herbicides ametryn, prometryn, propazine, and terbutryn were detected in less than 2 percent of samples. Temporal variation in concentration of herbicides in samples from the Mississippi River at Baton Rouge, 1991-97. The 1993 load of alachlor ESA represents July-December only. Annual loads of selected herbicides discharged to the Gulf of Mexico, 1991-97. Relation of total annual load and use for selected herbicides discharged to the Gulf of Mexico, 1991-97.
Lines are annual load as a constant percentage of annual use.
Table Table 1. Herbicides and herbicide metabolites analyzed in samples from the Mississippi River at Baton Rouge, Louisiana, 1991-97. Because many herbicides are relatively water soluble and mobile, they can be transported in surface runoff from agricultural fields to streams. Although herbicides have many benefits, they may also produce toxic side effects that may pose a potential hazard to human health and the environment. For instance, the U.S. Environmental Protection Agency classifies the herbicide alachlor as a human carcinogen, and several other herbicides including atrazine, cyan-azine, and metolachlor are classified as possible human carcinogens.