Database quality-control procedures
of data quality-control procedures were performed for data in the
Health-Based Screening Level (HBSL) database: (1) verification of
toxicity information collected from U.S. Environmental Protection
Agency (USEPA) data sources and (2) verification of HBSL values and the
methodology and information used to calculate them. These two
procedures are described below.
(1) Toxicity information collected from USEPA data sources was
entered into the HBSL database. After data entry, each record was
manually re-checked against its original USEPA data source. Any
incorrect values were corrected in the database with the correction
date noted. The process was then repeated to ensure that the
corrections made were accurate (see figure). This quality-control
procedure is followed each time updates are made to the database
in order to minimize
data entry errors.
(2) Using toxicity information collected from USEPA data sources,
HBSL values were independently calculated by two individuals from the USGS.
The independently calculated HBSL values were
compared with each other and discrepancies were iterated and resolved
before the values were entered into the database. The quality control process includes consulting with USEPA OW in a variety of cases when the computation of an HBSL is not straightforward (see Exceptions to how HBSLs are calculated). This procedure is followed
each time updates to toxicity information result in an update to an