NATIONAL WATER QUALITY LABORATORY
                      TECHNICAL MEMORANDUM 98.03A

                                                 August 28, 1998

Subject:        Changes in Reporting Levels and Data Qualifiers 
                for Selected Pesticides and Degradation Products in
                Schedules 2050 and 2051

Effective date   
of changes:     December 15, 1997

Authors:        Bill Foreman, Methods Research and Development Program
                303-467-8079, email: wforeman; and
                Bob Gilliom, Chief, NAWQA Pesticide Synthesis Team
                916-278-3094, email: rgilliom

Revision:       This memorandum replaces NWQL Technical Memorandum 98.03
                and portions of 96.06A.

Supplemental    Further information regarding schedule 2050 reporting
material:       changes and the procedure used to establish the new
                reporting levels is available as a supplement to the web
                page version of this technical memorandum, which 
                is accessible under "Technical Memoranda" on the
                National Water Quality Laboratory's home page at
                http://wwwnwql.cr.usgs.gov/USGS.

                                SCOPE

This technical memorandum announces changes, effective December 15,
1997, in the following data reporting practices for NWQL schedules 2050
and 2051 (Werner and others, 1996):

(1)  Reporting levels for nondetections will be raised for 14
     constituents.

(2)  An "E" code (estimated value) data qualifier will be added for all
     values of aldicarb, aldicarb sulfoxide, and aldicarb sulfone.

(3)  Esfenvalerate and 1-naphthol are deleted from the method.

These changes are based on analysis of performance data for schedule
2050 from the Organic Blind Sample Program by the NWQL's Quality
Assurance Unit and from routine laboratory reagent spike recovery data.
This memorandum also clarifies approaches previously used to derive
reporting levels for all constituents in schedules 2050 and 2051.

                    BACKGROUND ON REPORTING LEVELS

Reporting levels for all constituents in schedules 2050 and 2051
previously were announced in NWQL Technical Memorandum 96.06A issued
April 15, 1996, and were defined as equivalent to the method detection
limit (MDL), as determined by the U.S. Environmental Protection Agency's
(USEPA, 1994) MDL procedure.  However, as noted in USGS Open-File Report
96-216 (Werner and others, 1996) documenting the schedule 2050 method,
reporting levels (mistakenly listed as MDLs in table 12 of the OFR) for
a number of the constituents were set higher than MDL values determined
by the USEPA procedure (table 4 in the OFR).  These higher reporting
levels were based on in-house experiments, which showed that the
calculated MDLs could not be achieved in practice (based on producing an
ultraviolet spectra of sufficient sensitivity for matching with a
spectral library).

MDL values provided in memo 96.06A were obtained using the USEPA's MDL
procedure for 20 method constituents (see table A at the end of this
memo).  For the remaining 21 method constituents listed in memo 96.06A
(see table B at the end of this memo), the reporting level was set at a
value greater than the MDL, because the MDL could not be achieved.

               SUMMARY OF CHANGES IN DATA REPORTING

Reporting changes are required for the schedule 2050 and 2051
constituents listed in table 1.  These changes were based on method
performance data for schedule 2050 acquired from the Quality Assurance
Unit's Organic Blind Sample Program, which revealed a substantial number
of false negatives and several serious method recovery performance
problems, and from routine laboratory reagent spike recovery samples. 
No reporting changes were deemed necessary for any of the remaining
constituents in schedules 2050 and 2051.

Changes in reporting levels for nondetections are required for 14 method
constituents (table 1).  The 14 constituents include 5 for which MDL
values have been used to date as the reporting level (table A), and 9
for which reporting levels greater that the MDL have been used to date
(table B).

An "E" code is added to all values for aldicarb, aldicarb sulfoxide, and
aldicarb sulfone because of: (1) low and variable recoveries of aldicarb
and aldicarb sulfone and (2) post-collection conversion of aldicarb to
aldicarb sulfoxide, resulting in variable high bias in aldicarb
sulfoxide.  As reported in Werner and others (1996, p.34),
chlorothalonil, dichlobenil, and DNOC continue to be "E" coded because
of variable recovery performance during solid-phase extraction and HPLC
analysis.

The NWQL will no longer report esfenvalerate and 1-naphthol in schedules
2050 and 2051 because of unacceptable performance (mean recoveries of
<16% for both constituents from 165 laboratory reagent spike samples).



Table 1. Changes in data reporting for selected constituents 
         in schedules 2050 and 2051 at the NWQL

[WATSTORE, Water Data Storage and Retrieval System]
________________________________________________________________________

                                                     Reporting level
   Constituent       Parameter        NWQL          (microgram/liter)
                    (WATSTORE)      lab code      ______________________
                       code*        2050/2051     Current    Effective
                                                            Dec.15,1997
________________________________________________________________________

Constituents with Increased Reporting Levels

Carbofuran           49309A/B       5418/5618     0.028         0.12
Chloramben           49307A/B       5419/5619     0.011         0.42
Clopyralid           49305A/B       5423/5623     0.050         0.23
2,4-D                39732B/C       5408/5608     0.035         0.15
2,4-DB               38746A/B       5407/5607     0.035         0.24
MCPA                 38482A/B       5433/5633     0.050         0.17
MCPB                 38487A/B       5434/5634     0.035         0.14
Oryzalin             49292A/B       5440/5640     0.019         0.31
Triclopyr            49235A/B       5446/5646     0.050         0.25
        
Current "E" Coded Constituents with Increased Reporting Levels

DNOC                 49299A/B       5402/5602     0.035         0.42
Dichlobenil          49303A/B       5404/5604     0.020         1.20
Chlorothalonil       49306A/B       5421/5621     0.035         0.48

New "E" Coded Constituents with Increased Reporting Levels

Adicarb              49312A/B       5411/5611     0.016         0.55
Adicarb sulfone      49313A/B       5413/5613     0.016         0.10

New "E" Coded Constituent with No Reporting Level Change

Aldicarb sulfoxide   49314A/B       5412/5612     0.021      no change

Constituents Deleted from Schedules

Esfenvalerate        49298A/B       5429/5629     0.019       deleted
1-Naphthol           49295A/B       5438/5638     0.007       deleted
______________________________________________________________________
*Letter following 5 digits represents method code for schedule
 2050/2051.

              IMPLICATIONS OF CHANGES IN REPORTING LEVELS

These changes in reporting levels for nondetections (the value that
accompanies the "<" code) result in a much more realistic assessment of
what actual concentration of a pesticide could likely be detected if it
were present.  For example, many nondetections of carbofuran may have
been reported when the actual concentration was greater than 0.028 ug/L
(false negatives), but a very small percent of actual concentrations
greater than 0.12 ug/L will not be detected (see table 1).

Each constituent has a set of qualitative identification criteria that
must be met before it is quantified.  If these criteria are not met, a
"less than" concentration at the reporting level listed in table 1 will
be reported.  However, if identification criteria are met, the
concentration will be reported, even if less than the new reporting
level. This is consistent with the previous reporting conventions for
schedules 2050 and 2051, which use an "E" data qualifier to denote
estimated low-level concentrations.

                           EFFECT ON DATA BASE

The National Pesticide Synthesis Team of the NAWQA Program and NWQL
recommend that Districts delete all historic values of esfenvalerate and
1-naphthol produced using schedules 2050 and 2051 from their data base.

There will be no change in historical results reported for detections of
constituents listed in table 1, since all reported detections and
concentrations have been and still are considered reliable (except for
esfenvalerate and 1-naphthol).

Reporting level changes for the constituents in table 1 will cause a
shift in reporting levels, and thus nondetection (less than)
concentrations, in the data base.  Historical reporting levels are not
being changed in the data base at this time.  During FY 1998, the Office
of Water Quality, the NAWQA Program, the NWQL, and other Water Resources
Division representatives will develop policy on changes in historical
data and further guidance on interpreting analytical results, both new
and historical, for these schedules.  Data users should be cautious when
interpreting historical data for these constituents in light of the new
higher reporting levels.  The new reporting levels for nondetections are
more reliable indications of the actual concentrations that can be
detected.

                CLARIFICATION OF REPORTING LEVELS LISTED 
                   IN NWQL TECHNICAL MEMORADUM 96.06A


Table A. Constituents with reporting levels listed in NWQL 
         Technical Memorandum 96.06A that were set equivalent 
         to the Method Detection Limit (MDL)
________________________________________________________________________
 
                                                      Reporting level
  Constituent         Parameter        NWQL            set in 96.06A
                     (WATSTORE)      lab code            at the MDL
                        code*        2050/2051       (microgram/liter)
________________________________________________________________________

Aldicarb              49312A/B       5411/5611             0.016**
Aldicarb sulfone      49313A/B       5413/5613             0.016**
Aldicarb sulfoxide    49314A/B       5412/5612             0.021
Bentazon              38711A/B       5414/5614             0.014
Carbaryl              49310A/B       5417/5617             0.008
Carbofuran            49309A/B       5418/5618             0.028**
Chloramben            49307A/B       5419/5619             0.011**
Dacthal monoacid      49304A/B       5447/5647             0.017
Dichlorprop           49302A/B       5401/5601             0.032
Esfenvalerate         49298A/B       5429/5629             0.019**
Fenuron               49297A/B       5405/5605             0.013
3-Hydroxycarbofuran   49308A/B       5449/5649             0.014
Methiocarb            38501A/B       5436/5636             0.026
Methomyl              49296A/B       5437/5637             0.017
Neburon               49294A/B       5403/5603             0.015
Norflurazon           49293A/B       5439/5639             0.024
1-Naphthol            49295A/B       5438/5638             0.007**
Oryzalin              49292A/B       5440/5640             0.019**
Oxamyl                38866A/B       5441/5641             0.018
Silvex                39762B/C       5444/5644             0.021
________________________________________________________________________
 *Letter following 5 digits represents method code for schedule
  2050/2051.
**Reporting level for constituent being changed effective December 15,
  1997 (see table 1).


Table B. Constituents with reporting levels listed in NWQL Technical 
         Memorandum 96.06A as being equivalent to the MDL but that were 
         actually set in 96.06A at a concentration greater than the MDL

________________________________________________________________________ 
 
                                                     Reporting level
   Constituent         Parameter       NWQL         set in 96.06A at a
                      (WATSTORE)     lab code     concentration greater
                         code*       2050/2051        than the MDL
                                                    (microgram/liter)
________________________________________________________________________
                                                                                                   
Acifluorfen            49315A/B      5410/5610            0.035
Bromacil               04029A/B      5415/5615            0.035
Bromoxini              49311A/B      5416/5616            0.035
Chlorthalonil          49306A/B      5421/5621            0.035**
Clopyralid             49305A/B      5423/5623            0.050**
2,4-D                  39732B/C      5408/5608            0.035**
2,4-DB                 38746A/B      5407/5607            0.035**
Dicamba                38442A/B      5426/5626            0.035
Dichlobenil            49303A/B      5404/5604            0.020**
Dinoseb                49301A/B      5400/5600            0.035
Diuron                 49300A/B      5427/5627            0.020
DNOC                   49299A/B      5402/5602            0.035**
Fluometuron            38811A/B      5430/5630            0.035
Linuron                38478A/B      5432/5632            0.018
MCPA                   38482A/B      5433/5633            0.050**
MCPB                   38487A/B      5434/5634            0.035**
Picloram               49291A/B      5442/5642            0.050
Propham                49236A/B      5443/5643            0.035
Propoxur               38538A/B      5450/5650            0.035
2,4,5-T                39742B/C      5409/5609            0.035
Trichlopyr             49235A/B      5446/5646            0.050**
_______________________________________________________________________
 *Letter following 5 digits represents method code for schedule
  2050/2051.
**Reporting level for constituent being changed effective December 15,
  1997 (see table 1).  


                               REFERENCES

U.S. Environmental Protection Agency, 1994, Guidelines establishing test
     procedures for the analysis of pollutants (App. B, Part 136,
     Definition and procedures for the determination of the method
     detection limit): U.S. Code  of Federal Regulations, Title 40,
     revised July 1, 1994, p. 635-637.

Werner, S.L., Burkhardt, M.R., and DeRusseau, S.N., 1996, Methods of
     analysis by the U.S. Geological Survey National Water Quality
     Laboratory--Determination of pesticides in water by Carbopak-B
     solid-phase extraction and high-performance liquid
     chromatography: U.S. Geological Survey Open-File Report 96216.


                                      /s/

                            Robert S. Williams, Jr., Chief
                            National Water Quality Laboratory
                            Branch of Analytical Services


Supersedes:   This memorandum replaces NWQL Technical Memorandum 98.03
              and portions of 96.06A.

Key Words:    Schedule 2050, Reporting levels, Pesticides, Deletions

Distribution: E and http://wwwnwql.cr.usgs.gov/USGS