NATIONAL STATUS AND TRENDS PROGRAM
Description:
Since 1984, the National Status and Trends (NS&T) Program has monitored, on a national scale, spatial and temporal trends of chemical contamination and biological responses to that contamination. Temporal trends are being monitored through the Mussel Watch project that analyzes mussels and oysters collected annually at about 200 of those sites. Spatial trends have been described on a national scale from chemical concentrations measured in surface sediments collected by both the Mussel Watch and Benthic Surveillance Projects from 240 sites distributed throughout the coastal and estuarine United States. The Benthic Surveillance Project has, in addition, measured chemical concentrations in fish livers and performed histological analyses of fish for evidence of biological responses to chemical contamination.
The raw data from these projects are available. They have been interpreted to indicate that chemical contamination, while universal in an absolute sense, is at high levels near centers of human population. Even in those areas, actual biological responses to chemical contamination are usually limited the extreme contamination found in hot spots of limited spatial extent. Temporal trends in chemical contamination are beginning to be evident from the Mussel Watch project and, when trends exist, they are predominantly in the direction of decreasing concentrations.
Record Details:
Record Type:DATA SET
Product Published Date:07/21/1996
Record Last Revised:12/10/2002
Record ID:
3327
Keywords:
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Quality Assurance:
Title
:NATIONAL STATUS AND TRENDS PROGRAM
Data Use & Constraints
:Four ASCII files are available for download via this Internet Information Service.
Within the files the following conventions have been used:
Files are free formatted ASCII text beginning with a one record header defining variable names (fields) followed by all data records similarly structured. Fields are separated with hard tabs; i.e., ASCII CHR(09). Following standard free format conventions, records are in DOS format, terminated by a CR and line feed (LF); i.e., CHR(13) and CHR(10).
In all cases a positive concentration other than zero (0) is a real quantified value. A zero (0) has been inserted whenever the measured value was less than detectable. The listed detection limits vary by laboratory and year.
It is important to differentiate zeros from missing data. Since some computer applications will equate a missing entry (i.e., CHR(0) or null) with a zero, all missing numerical values have been given the value -0.001. This means that no attempt was made to measure that chemical, in that sample, in that year (usually because the chemical was not among the target analytes for that year). Some alphabetic variables may retain nulls, because, in those fields, there are no zeros that could be confused with nulls.
The Sediment Data file contains Mussel Watch data for 1986 through 1991 and Benthic Surveillance data for 1984 through 1988. Starting in 1988 and within the Mussel Watch Project, sediment samples stopped being collected at sites where sediment was already sampled in a prior year.
