Assessment Comments
Assesment is based on results of U.S. EPA/IDNR fish tissue (RAFT) monitoring in 2002 and 2004.
Basis for Assessment
SUMMARY: The general aquatic life uses were not assessed due to the lack of information upon which to base an assessment. Fish consumption uses remain assessed as "not supporting" due to the continuance of the fish consumption advisory at this lake: levels of both chlordane and PCBs in bottom-feeding fish suggest the need to continue the existing fish consumption advisory at this lake. Other beneficial uses of this "general use" lake were not assessed. The source of data for this assessment is results of EPA/IDNR fish contaminant (RAFT) monitoring at Cedar Lake in 2002 and 2004.
Note: A TMDL for chlordane at Cedar Lake was prepared by IDNR and approved by EPA in 2001; thus, this lake was placed into IR Category 4a (TMDL approved) for the 2004 assessment/listing cycle. Because the 2006 Section 303(d) impairment due to PCBs was not addressed in the TMDL, this waterbody was moved from IR Category 4a to Category 5a (impaired; TMDL required) for the 2006 assessment/listing cycle.
EXPLANATION: Because data are not available to develop an assessment of support of the general aquatic life uses, these uses are considered "not assessed."
Fish consumption uses were assessed (monitored) as “not supported” based the existence of a fish consumption advisory at this lake and on results of ongoing U.S.EPA/IDNR fish contaminant (RAFT) monitoring at Cedar Lake in 2002 and 2004. The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of the degree to which Iowa’s lakes and rivers support their fish consumption uses. Prior to 2006, IDNR used action levels published by the U.S Food and Drug Administration to determine whether consumption advisories should be issued for fish caught as part of recreational fishing in Iowa. In an effort to make Iowa’s consumption more compatible with the various protocols used by adjacent states, the Iowa Department of Public Health (IDPH), in cooperation with Iowa DNR, developed a risk-based advisory protocol. This protocol went into effect in January 2006 (see http://www.iowadnr.gov/fish/news/consump.html for more information on Iowa’s revised fish consumption advisory protocol). Because the revised (2006) protocol is more restrictive than the previous protocol based on FDA action levels; fish contaminant data that previously suggested “full support” may now suggest either a threat to, or impairment of, fish consumption uses. This scenario applies to the fish contaminant data generated from the RAFT sampling conducted in Cedar Lake: levels of chlordane and PCBs exceeded advisory trigger levels in the samples of channel catfish and common carp from the 2002 RAFT, and levels of PCBs in the sample of channel catfish exceeded the advisory trigger level for PCBs in the 2004 RAFT. These results suggest the continued need for a consumption advisory at Cedar Lake. According to IDNR’s assessment methodology, the existence of a consumption advisory indicates that fish consumption uses should be assessed as “not supported”.
A fish consumption advisory has existed at Cedar Lake since 1986. Because of this advisory, Cedar Lake has been monitored as part of the RAFT program on an every-other-year basis since 1986. Levels of chlordane in fillets from bottom-feeding fish (channel catfish and common carp) have frequently exceeded the previous trigger level (FDA action level) of 0.3 ppm used by the Iowa DNR. In January 2006, Iowa adopted a revised protocol, as developed jointly by the Iowa Department of Public Health and the Iowa DNR, for issuing consumption advisories. The existing data for contaminants in fish from all Iowa lakes and rivers were reviewed to determine whether the new protocol would justify the continuance of existing advisories or justify the issuance of new advisories. The new trigger level for technical chlordane is 0.6 ppm (for a one meal per week advisory), and the new trigger levels for PCBs is 0.2 ppm (for a one meal per week advisory). A review of the existing data for Cedar Lake justifies continuance of the consumption advisory for common carp and channel catfish.
The level of technical chlordane in the composite sample of fillets from channel catfish collected for the 2002 RAFT program was 0.77 ppm; this level is greater than the IDPH/INDR trigger level of 0.6 ppm for a one meal per week consumption advisory. Also, the level of PCBs in the composite sample of fillets from common carp collected for the 2002 RAFT program was 0.44 ppm; this level is greater than the IDPH/INDR trigger level of 0.2 ppm for a one meal per week consumption advisory. Levels of both chlordane and PCBs, however, were well-below the “do not eat” trigger levels of 5.0 ppm for chlordane and 2.0 ppm for PCBs.
For the 2004 RAFT sampling, the composite samples of fillets from common carp and channel catfish had generally lower levels of contaminants. Levels of primary contaminants in the composite common carp fillets were low and did not suggest fish contaminant problems (mercury: 0.029 ppm; total PCBs: 0.180 ppm; and technical chlordane: 0.039 ppm). Levels of primary contaminants in the composite sample of channel catfish fillets were also relatively low (mercury: 0.02 ppm; total PCBs: 0.277 ppm; and technical chlordane: 0.163 ppm) The level of PCBs in the composite sample of fillets from common carp collected for the 2004 RAFT program (0.277 ppm), however, is greater than the IDPH/INDR trigger level of 0.2 ppm for a one meal per week consumption advisory.
Thus, because the levels of chlordane and PCBs exceeded advisory trigger levels in channel catfish and common carp in 2002, and because levels of PCBs in channel catfish exceeded the advisory trigger level in the 2004 RAFT sampling, continuance of the existing advisory, and the impairment of fish consumption uses, is justified. As per Iowa’s revised protocol, the type of advisory, however, was changed from a “do not eat” to a “one meal per week” advisory. According to the IDNR/IDPH advisory protocol, two consecutive samplings showing that contaminant levels are below the trigger level in fillet samples are needed to rescind an existing consumption advisory. RAFT monitoring will again be conducted at Cedar Lake in 2006.
