Nitrapyrin

Field studies

Administrative data

Endpoint:

field studies

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2 April 1986 to 1 October 1987

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Study conducted to GLP in compliance with agreed protocols, with no or minor deviations from test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. However, because there is no detail regarding the purity of the test material used in the study, the study was assigned a reliability score of 2.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1987

Report date:

1978

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: EPA Guideline Subdivision N Guideline 164-1 (environmental fate)

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Nitrapyrin

EC Number:

217-682-2

EC Name:

Nitrapyrin

Cas Number:

1929-82-4

Molecular formula:

C6H3Cl4N

IUPAC Name:

2-chloro-6-(trichloromethyl)pyridine

Results and discussion

Any other information on results incl. tables

At all locations, the concentration of test material in the surface 0 to 6 inches of soil was higher at some time after application compared to the 0-day sampling. Since the chemical was incorporated immediately following application using tillage methods, the test material would not have been evenly distributed throughout this soil zone. This non-uniform initial distribution would result in some sampling variability. With time after application, the distribution of the test material became more uniform. To compensate for this initial variability in distribution of the compound and produce a more realistic representation of the dissipation of test material, the highest average soil concentration at a site during the first 7 days following application was used as the first value for calculating the first-order half-life at that location.

- Mississippi

The dissipation of residues of test material was fairly rapid with residues not detected ( ≥ 0.05 ppm) in any soil sample at the 79- 120- , and 201-day samplings. Test material was not detected below the 0- to 6-inch sampling increment. The first-order dissipation half-life of test material in the surface 6 inches of soil based on the average soil concentrations for the 7- through 40-day samplings was about 13 days. Residues of the metabolite DCMP were not detected (≥ 0.05 ppm) in any soil sample during the study. Residues of the metabolite 6-CPA acid were found in a few samples from the 0- to 6-inch layer during the first 40 days after application, but were no longer detected at the 79-day sampling.

 

- Illinois

The dissipation of the test material was fairly rapid and residues were detected (≥ 0.05 ppm) in only one sample at 80 days and were no longer detected at the 120-day sampling. An 80-day sample from the 6- to 12-inch depth of one subplot contained detectable residues of test material, but for all other samplings, detectable (≥ 0.05 ppm) residues were limited to the upper 0-6 inches of soil. The first-order dissipation half-life of test material in the surface 6 inches of soil based on the average soil concentrations for the 7- through 40-day samplings was about 28 days.

The metabolites DCMP and 6 -CPA were not detected (≥ 0.05 ppm) in any soil sample on any sampling date after application.

 

- Michigan

The dissipation of residues of test material in the soil was fairly rapid, and by the 81-day sampling residues were detected in only two of the plots and in only one plot on day 123. Residues were no longer detected (≥ 0.05 ppm) at the 184-day sampling in any plot. Except for the 18- to 24-inch sample from one plot on day 45, residues of test material were not detected below the upper 6 inches of the soil. Since residues were not detected in the 6- to 12-inch or 12- to 18-inch samples on day 45, the validity of the results for the 18- to 24-inch sample is suspect and was probably the result of contamination. The first-order dissipation half-life for test material residues in the surface 6-inch layer of soil based on the average soil concentration for the 3- to 45-day samplings was about 15 days.

No residues of DCMP were detected in any soil sample on any sampling date. Residues of 6 -CPA were only detected (≥ 0.05 ppm) in the 0- to 6-inch samples from two plots on day 3.

 

- California

The residue levels of test material in the soil remained fairly constant during the first 14 days after application but then declined more rapidly through the remainder of the study. Residues were detected (≥ 0.05 ppm) in only one plot at 77 days and were no longer detected in any samples at the 118- and 208-day samplings. At 28 days residues of test material were detected in the 6- to 12-inch and 12- to 18-inch samples of one subplot, but on all other sampling dates, detectable residues were limited to the upper 6 inches of the soil.

Since residues were not detected below 6 inches at any other time and no precipitation or irrigation occurred between the 14- and 28 day samplings (14 May 1986 - 28 May 1986), the residues below 6 inches in the one subplot at 28 days were probably due to sample contamination or mislabelling. The first-order dissipation half-life for test material in the surface 6 inches of soil based on the average concentrations for the 5- to 77-day samplings was about 34 days.

Residues of DCMP were detected (≥ 0.05 ppm) in only the 0- to 6-inch sample from one plot on day 7, and were not detected in any other sample. Residues of 6-CPA were detected (≥ 0.05 ppm) in only a few 0- to 6-inch samples and were no longer detected after the 77-day sampling. At the 28-day sampling, residues of the 6-CPA were detected in the 6- to 12-inch and 12- to l8-inch samples of the same plot that residues of test material were detected to the 12- to 18-inch depth and were probably also the result of sample contamination.

 

Applicant's summary and conclusion

Conclusions:

At four field sites representing a wide variety of environmental conditions, the dissipation of residues of test material in soil following a 1.0-lb a.i./acre application of test material was fairly rapid. Residues of test material were not detected at any site after 123 days. The first-order dissipation half-lives based on the average concentrations of test material in the surface 6 inches of soil ranged from 13 - 34 days.
The limited leaching of test material was clearly demonstrated in the field studies. Residues were confined to the 0- to 6-inch layer of soil except for a single 6- to 12-inch sample at one site. Due to the adsorption and fairly rapid dissipation of test material, differences in soil conditions or precipitation between sites had no real effect on the depth of leaching.
Residues of the metabolites DCMP and 6-CPA were detected in only a few samples and were no longer detected at any site after 77 days following application. Except for the suspect 28-day samples at the California site, both metabolites were confined to the 0- to 6-inch layer of soil.
The results of the four field studies conducted at varying locations throughout the corn-producing areas, clearly demonstrate the test material and its metabolites do not persist in soil and are confined to the surface layer of soil. Based on these studies, the potential for long-term accumulation or deeper leaching to ground water of test material or the metabolites would be expected to be very low following applications of test material under similar use conditions.

Executive summary:

Field studies were conducted in Mississippi, Illinois, Michigan, and California to evaluate the dissipation and leaching of the test material and its metabolites following a 1.0-lb a.i./acre application of test material formulation. Dissipation of the test material was fairly rapid at all sites, and residues were no longer detected ( ≥ 0.05 ppm) after 123 days at any site. Except for residues in a single 6- to 12-inch sample at one site, test material was not detected below the surface 6 inches of the soil. Half-lives of test material in the surface 6 inches of soil ranged from 13 - 34 days. Residues of both metabolites were confined to the upper 6 inches of the soil and were no longer detected (≥ 0.05 ppm) at any site after 77 days. The results indicate that the potential for long-term persistence or deep leaching of test material or the metabolites following normal applications of the test material formulation under typical use conditions would be very low.