The acetochlor registration partnership surface water monitoring program for four corn herbicides (original) (raw)

and USEPA required, that market forces following the registration of acetochlor would reduce the mass of corn A surface drinking water monitoring program for four corn (Zea herbicides applied in the United States by substituting mays L.) herbicides was conducted during 1995-2001. Stratified ranreduced-rate acetochlor formulations for previously dom sampling was used to select 175 community water systems (CWSs) within a 12-state area, with an emphasis on the most vulnerable sites, registered corn herbicides such as alachlor, metolachlor, based on corn intensity and watershed size. Finished drinking water was atrazine, 2,4-D, butylate, and EPTC. This was borne monitored at all sites, and raw water was monitored at many sites using out by USDA figures (National Agricultural Statistics activated carbon, which was shown capable of removing herbicides and Service, 2004), which show that the total amount of their degradates from drinking water. Samples were collected biweekly these six herbicides applied to corn during the first four from mid-March through the end of August, and twice during the offyears of the acetochlor registration (1994-1997) fell by season. The analytical method had a detection limit of 0.05 g L Ϫ1 for 83.5 million kg from the amount applied the previous alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)-acetamide] four years (Fig. 1). The amount of acetochlor applied and 0.03 g L Ϫ1 for acetochlor [2-chloro-N-(ethoxymethyl)-N-(2-ethylduring this same period was 40.3 million kg, thereby 6-methylphenyl)-acetamide], atrazine [6-chloro-N-ethyl-N-(1-methylexceeding the reduction required by USEPA. ethyl)-1,3,5-triazine-2,4-diamine], and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)-acetamide]. Of the 16 528 In addition to the use reduction target, the USEPA drinking water samples analyzed, acetochlor, alachlor, atrazine, and imposed conditions on acetochlor intended to limit pometolachlor were detected in 19, 7, 87, and 53% of the samples, respectential risks to human health and the environment, intively. During 1999-2001, samples were also analyzed for the presence cluding an extensive surface water monitoring program of six major degradates of the chloroacetanilide herbicides, which involving 175 CWSs. The ARP agreed to suspend sales were detected more frequently than their parent compounds, despite and use of acetochlor in any watershed where the timehaving higher detection limits of 0.1 to 0.2 g L Ϫ1. Overall detection weighted AMC of acetochlor in drinking water exfrequencies were correlated with product use and environmental fate ceeded 2 g L Ϫ1 (USEPA, 1994) and to voluntarily characteristics. Reservoirs were particularly vulnerable to atrazine, cancel the USEPA registration of acetochlor if the AMC which exceeded its 3 g L Ϫ1 maximum contaminant level at 25 such sites during 1995-1999. Acetochlor annualized mean concentrations exceeded 2 g L Ϫ1 in either two large (Ͼ100 000 people) (AMCs) did not exceed its mitigation trigger (2 g L Ϫ1) at any site, CWSs or 10 of any size. The USEPA set this value of and comparisons of observed levels with standard measures of human 2 g L Ϫ1 for acetochlor as a conservative limit based on and ecological hazards indicate that it poses no significant risk to the 2 g L Ϫ1 maximum contaminant level (MCL) it had human health or the environment.