United States
Environmental Protection
Agency
Office of Water
Office of Pesticides and
Toxic Substances
x>EPA National Pesticide Survey
Fall 1990
Quality Assurance/
Quality Control
- f-
What is
QA/QC?
QA/QC
Throughout
the Survey
*ere lmf>ten»sn«"' •*
"**• ""
element of the
These
WPS Oua/jfy Assurance/Oua/rty Control
•~>rt or i Rocvc/eri
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• ^ <^AP
(SAP). The ten-member SAP
findings of the pilot study.
reviewed the overall Survey design and the
on four broad areas of the
^^ Q{
changes.
QA/QC in the Field.
procedures for field ^
conducted according to s
arrd contractor personnel mvoJved I .n
field actfoes such as sampling and
designed-questionnaires to obta,
and land use in the surround^ a r
agricultural extension agents. To re
prablems, EPA set ^ a teteP^r
also conducted audits at a number of f, etc
of the QC procedures. These
from
(SOPs). A,, State
efore undertaking
inistered speciaily
construction, pesticide use,
and county
> J lin questions or
a ny H y EPA
assess the effectiveness
ms or inconsistencies
the sampling phase of
the highest analytical
activities included a
it were a water Cam,
bottle, shipped to the field, and returne^
samples (samples to jjtjch * nown
laboratory control standards. In adc,
samples for approximately ten pecen t rt
overflow relief to the primary
required to obtain analytical
format, and pass an a
Audits were conducted
instrumentation were accurate and property
following the established opera *ng
Reagent watlr analyzed as if
transferred to a sampling
with tne samp[es), spiked
' d)i and instrument and
analyzed duplicate
collected and provided
laboratories were
resuits in a standardized
resu ^ ^ ^
procedures and
, that the laboratories were
could be tracked and
Performance evaluation
u -
QA/QC in Data Mhnagemerrt
conducted us^ the
system. NPSIS was
schedu.es.
a. communications link
implementation.
K
NFS Quality Assurance'Quatit* C -rtr-.
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Problems
Identified and
Corrected
through
QA/QC
Summary
control for data entry errors. QA for data entry was implemented through the
performance of random audits of the data entry process. After completion of all
QA/QC checks, the data were transferred to NPSIS.
-" •fi, , -'"' .
The NPS quality assurance program identified and corrected potential problems
that could have affected data quality/ Quality control checks and quality assurance
audits worked together to ensure that sampling, data collection, and laboratory
analysis continued on schedule and that field and laboratory staff followed specific
procedures. Rigorous reviews and quality assurance audits at each phase of the
Survey --initial planning and design, the pilot study, the full Survey, and data
analysis *- assisted management staff in monitoring the progress of the Survey to
prevent problems that could compromise data quality. For example, EPA revised the
Survey design, based on the pilot study results and SAP recommendations, to correct
implementation problems by:
• adopting a two-stage design for identifying community water system
wells;
allocating sampling randomly within the Survey schedule to minimize the
possibility of seasonally-induced bias;
dropping the laboratory method for volatile organic compounds due to
problems with sample aeration under Survey conditions; and
expanding the Survey's questionnaires to collect additional information on
well characteristics, cropping, and pesticide use.
The Survey's QA program also provided critical information that prevented
serious data losses during sampling and data collection. These situations were rare
and were corrected immediately. For example, early in the Survey QA staff identified
that the laboratories were receiving an overload of samples. If this problem had not
been discovered and resolved, sample data and analysis results would have been
lost. EPA quickly provided analytic support to the laboratories and corrected sample
storage procedures, EPA also identified trace amounts of chlorine in some well water
samples, which adversely affects detecting pesticides. In response, EPA quickly
initiated additional procedures to test for chlorine in the field as well as in the primary
laboratories.
Quality assurance staff identified other technical problems such as incorrect
interpretation of questionnaire terms, an inaccurate instrument calibration standard,
and inappropriate delays in computer database backups. Again, as a result of early
detection, these minor problems were corrected before serious loss of information or
data quality occurred.
EPA was diligent in supporting and implementing a quality assurance program
for the NPS. The Survey's key QA/QC elements - expert review, pilot studies, training,
specific standard operating procedures, detailed quality assurance plans for each
major phase of the study, and routine audits - are now recognized throughout EPA as
models for other EPA studies. The direct benefit for the policy analysts, scientists, and
others who will use NPS results is an information base of documented, consistent,
high quality data on drinking water wells, pesticide use, and ground-water vulnerability.
WPS Quality Assurance I Quality Control
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Where to Go
for More
Information
This fact sheet is part of a series of NFS outreach materials, fact sheets and
reports. The following additional fact sheets are available through EPA's Public
Information Center (401 M Street SW, Washington DC 20460, 202-382-2080):
Project Summary
Analytical Methods
Fact Sheet for each
detected analyte
Summary Results
Survey Analyses
How EPA Will Use
The NPS Results
Survey Design
Glossary
Additional information oh the Survey and on pesticides in general can be
obtainecHrom the following sources:
U.S. EPA-Safe Drinking Water Hotline •
1-800-426-4791 (In Washington, DC - 382-5533)
Monday-Friday, 8:30 am to 4:30 pm Eastern Time
I
National Pesticide Telecommunications Network
1-800-858-7378 :
24 hours a day I
U.S. EPA Office of Pesticide Programs (OPP) Docket
401 M Street, SW Room NEG004
Washington, DC 20460 j
(202) 382-3587 i
National Technical Information [Service (NTIS)
5285 Port Royal Road !
Springfield, VA 22161
(703) 487-4650
Information on regulation of
pesticides in drinking
water
Information on health
effects and safe
handling of pesticides
Background documents
for Survey (available
for review)
Copies of the
NPS Phase I Report
(available 1991) and
NPS Phase II Report
(when available)
If you are concerned about the presence of pesticides and nitrate in your private water
well, contact your local or State health department. Other experts in your State
environmental agency or agriculture and health department may also be helpful to
you. If you receive your drinking water from a community water system and have
questions about your water quality, contact your local community water system
owner/operator or the State water supply agency.
NPS Quality Assurance IQ
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