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Christopher J. Schmitt

Publications and source records attributed to Christopher J. Schmitt.

44 records · Page 3Linked to original sources
USGS1990

National contaminant biomonitoring program: Residues of organochlorine chemicals in U.S. Freshwater Fish, 1976–1984

The U.S. Fish and Wildlife Service periodically determines concentrations of organochlorine chemicals in freshwater fish collected from a nationwide network of stations as part of the National Contaminant Biomonitoring Program (NCBP, formerly a part of the National Pesticide Monitoring Program). From late 1984 to early 1985, a total of 321 composite fish samples were collected from 112 stations and analyzed for organochlorine chemical residues. The mean concentrations of total DDT did not change from 1980–81 to 1984, following a period of steady decline through the 1970's; however, the mean concentrations of p,p′ -DDT declined significantly. The most persistent DDT homolog ( p,p′ -DDE) was detected at 98% of the stations sampled in 1984, and constituted 73% of total DDT residues, up from 70% in 1974–79. Collectively, these findings indicate a low rate of influx and continued weathering of DDT in the environment. Residues of polychlorinated biphenyls (PCBs) also remained widespread, but a significant downward trend in total PCBs was evident, and early eluting PCB components were present at fewer stations than in the past. Mean concentrations of dieldrin have not changed since 1978–79; concentrations remained highest in Hawaii and in the Great Lakes. Toxaphene concentrations declined from 1980–81 to 1984, especially in the Great Lakes, and the incidence of toxaphene declined from 88% of the stations sampled in 1980–81 to 69% in 1984. Mean chordane concentrations did not change from 1980–81 to 1984, following a period of decline; however, trans -nonachlor replaced cis -chlordane as the most abundant component, suggesting a lower influx of chlordane to the aquatic environment. Residues of other organochlorines—mirex, pentachloroanisole (PCA), benzene hexachloride (BHC) isomers, endrin, heptachlor, hexachlorobenzene (HCB), and Dacthal ® (DCPA)—were either found at relatively few (<25%) of the stations sampled in 1984 or were characterized by relatively low concentrations. In general, organochlorine concentrations were lower in 1984 than at any time reported previously.

Archives of Environmental Contamination and Toxico↗
USGS1988

Chemical characterization and mutagenic properties of polycyclic aromatic compounds in sediment from tributaries of the Great Lakes

Sediments from four inshore industrial sites and a reference site in the Great Lakes were extracted with solvents and characterized chemically for polycyclic aromatic compounds (PACs). An aqueous phase and a crude organic extract were obtained. The crude organic extract was further resolved into fractions A-2 (polycyclic aromatic hydrocarbons) and A-3 (nitrogen-containing polycyclic aromatic compounds), which were analyzed for PACs by gas chromatography and gas chromatography-mass spectrometry. The extracts and fractions were tested for mutagenicity in three assays: Ames, rat hepatocyte unscheduled DNA synthesis, and Chinese hamster ovary hypoxanthine-guanine phosphoribosyl transferase (CHO/HGPRT). Sediments from the industrial sites contained 27 to 363 &mu;g/g total PACs; the reference site, less than 1 &mu;g/g. Qualitative differences in the residue profiles among the sites were attributable to the probable sources of the PACs (petroleum versus combustion). Only one industrial site yielded measurable (0.1 &mu;g/g or more) concentrations of individual nitrogen-containing PACs. In the Ames assay, only the highest doses of the A-2 fractions from two sites approached positive results. Conversely, the crude organic extract and A-2 and A-3 fractions from all sites induced unscheduled DNA synthesis. Crude organic extracts and the A-2 and A-3 fractions from all industrial sites gave well-defined dose-response relations in the CHO/HGPRT assay. We established the presence of chemical mutagens in sediment that could be correlated with neoplasms in fish from many of the sites; however, the mutagenicity of the sediment extracts was not completely related to the degree of contamination by PACs. We also discuss the utility of mutagenicity assays in the evaluation of complex chemical mixtures and recommend the use of a CHO/HGPRT-type assay in which cells are not required to proliferate in the presence of potential interfering chemicals.

Environmental Toxicology and Chemistry↗
USGS1987

The effects of sample preparation on measured concentrations of eight elements in edible tissues of fish from streams contaminated by lead mining

The influence of sample preparation on measured concentrations of eight elements in the edible tissues of two black basses (Centrarchidae), two catfishes (Ictaluridae), and the black redhorse, Moxostoma duquesnei (Catostomidae) from two rivers in southeastern Missouri contaminated by mining and related activities was investigated. Concentrations of Pb, Cd, Cu, Zn, Fe, Mn, Ba, and Ca were measured in two skinless, boneless samples of axial muscle from individual fish prepared in a clean room. One sample (normally-processed) was removed from each fish with a knife in a manner typically used by investigators to process fish for elemental analysis and presumedly representative of methods employed by anglers when preparing fish for home consumption. A second sample (clean-processed) was then prepared from each normally-processed sample by cutting away all surface material with acid-cleaned instruments under ultraclean conditions. The samples were analyzed as a single group by atomic absorption spectrophotometry. Of the elements studied, only Pb regularly exceeded current guidelines for elemental contaminants in foods. Concentrations were high in black redhorse from contaminated sites, regardless of preparation method; for the other fishes, whether or not Pb guidelines were exceeded depended on preparation technique. Except for Mn and Ca, concentrations of all elements measured were significantly lower in cleanthan in normally-processed tissue samples. Absolute differences in measured concentrations between clean- and normally-processed samples were most evident for Pb and Ba in bass and catfish and for Cd and Zn in redhorse. Regardless of preparation method, concentrations of Pb, Ca, Mn, and Ba in individual fish were closely correlated; samples that were high or low in one of these four elements were correspondingly high or low in the other three. In contrast, correlations between Zn, Fe, and Cd occurred only in normallyprocessed samples, suggesting that these correlations resulted from high concentrations on the surfaces of some samples. Concentrations of Pb and Ba in edible tissues of fish from contaminated sites were highly correlated with Ca content, which was probably determined largely by the amount of tissue other than muscle in the sample because fish muscle contains relatively little Ca. Accordingly, variation within a group of similar samples can be reduced by normalizing Pb and Ba concentrations to a standard Ca concentration. When sample size ( N ) is large, this can be accomplished statistically by analysis of covariance; when N is small, molar ratios of [Pb]/[Ca] and [Ba]/[Ca] can be computed. Without such adjustments, unrealistically large N s are required to yield statistically reliable estimates of Pb concentrations in edible tissues. Investigators should acknowledge that reported concentrations of certain elements are only estimates, and that regardless of the care exercised during the collection, preparation, and analysis of samples, results should be interpreted with the awareness that contamination from external sources may have occurred.

Missouri↗
USGS1986

Organochlorine chemical residues in bluegills and common carp from the irrigated San Joaquin Valley floor, California

Samples of bluegills ( Lepomis macrochirus ) and common carp ( Cyprinus carpio ) collected from the San Joaquin River and two tributaries (Merced River and Salt Slough) in California were analyzed for 21 organochlorine chemical residues by gas chromatography to determine if pesticide contamination was confined to downstream sites exposed to irrigated agriculture, or if nonirrigated upstream sites were also contaminated. Residues of p,p′ -DDE were detected in all samples of both species. Six other contaminants were also present in both species at one or more of the collection sites: chlordane ( cis -chlordane + trans -nonachlor); p,p′ -DDD; o,p′ -DDT; p,p′ -DDT; DCPA (dimethyl tetrachloroterephthalate); and dieldrin. Concentrations of most of these residues were generally higher in carp than in bluegills; residues of other compounds were found only in carp: α-BHC (α-benzenehexachloride), Aroclor ® 1260, and toxaphene. Concentrations of most organochlorines in fish increased from upstream to downstream. Water quality variables that are influenced by irrigation return flows ( e.g. , conductivity, turbidity, and total alkalinity) also increased from upstream to downstream and were significantly correlated ( P < 0.05) with organochlorine residue levels in the fish. In carp, concentrations of two residues-⌆DDT ( p,p′ -DDD + p,p′ -DDE + + p,p′ -DDT; 1.43 to 2.21 mg/kg wet weight) and toxaphene (3.12 mg/kg wet weight)-approached the highest levels reported by the National Pesticide Monitoring Program for fish from other intensively farmed watersheds of the United States in 1980 to 1981, and surpassed criteria for whole-body residue concentrations recomended by the National Academy of Sciences and National Academy of Engineers for the protection of piscivorous wildlife.

California↗
USGS1985

National Pesticide Monitoring Program: Residues of organochlorine chemicals in freshwater fish, 1980–81

The U.S. Fish and Wildlife Service analyzed residues of organochlorine chemicals in 315 composite samples of whole fish collected in 1980–81 from 107 stations nationwide as part of the National Pesticide Monitoring Program (NPMP). The mean concentrations of total DDT and all p,p ′-ho-mologs except p,p ′-DDT showed significant but small declines relative to mean concentrations before 1978–79. The mean concentration of p,p ′-DDT did not change. The most persistent DDT homolog ( p,p ′-DDE) continued to constitute about 70% of total DDT residues, as it did in 1974–79. DDT contamination attributable to former DDT manufacturing facilities remained evident at sites in Alabama and Arkansas, and high concentrations at one site in Hawaii suggested that input to the environment was continuing. Conversely, the data do not support the contention of others that DDT was still being used in the Southwest. Residues of polychlorinated biphenyls (PCBs) remained widespread, but a significant downward trend in total PCBs was evident, especially in areas that the NPMP has previously shown to be the most heavily contaminated. Mean concentrations of dieldrin had not changed since 1978–79, and levels remained highest in Hawaii and in the Great Lakes. Toxaphene concentrations plateaued after a period of steady increase through the 1970's, but the incidence of toxaphene continued to increase; residues were present at 88% of the stations sampled in 1980–81, including one in Alaska (most likely as a consequence of atmospheric transport). Mean chlordane concentrations were slightly lower than in 1978–79, and residues were detected at fewer stations in 1980–81 than in 1978–79. Residues of other organochlorines [ e.g. , mirex, pentachloroanisole (PCA), benzene hexachloride (BHC) isomers, endrin, heptachlor, hexachlorobenzene (HCB), Dacthal ® (DCPA) 2 , and methoxychlor] were either found at relatively few (<25%) of the stations sampled in 1980–81 or were characterized by relatively low concentrations.

Archives of Environmental Contamination and Toxico↗
USGS1984

Bioavailability of Pb and Zn from mine tailings as indicated by erythrocyte aminolevulinic acid dehydratase (ALA-D) activity in suckers (Pisces: catostomidae)

The activity of the erythrocyte enzyme δ-aminolevulinic acid dehydratase (ALA-D) was measured in 35 catostomids (black redhorse, Moxostoma duquesnei ; golden redhorse, M . erythrurum ; northern hogsucker, Hypentelium nigricans ) collected from three sites on a stream contaminated with Pb-, Cd-, and Zn-rich mine tailings and from an uncontaminated site upstream. Enzyme activity was expressed in terms of hemoglobin (Hb), DNA, and protein concentrations; these variables can be determined in the laboratory on once-frozen blood samples. Concentrations of Pb and Zn in blood and of Pb in edible tissues were significantly higher, and ALA-D activity was significantly lower, at all three contaminated sites than upstream. At the most contaminated site, ALA-D activity was 62–67% lower than upstream. Lead concentrations in the edible tissues and in blood were positively correlated ( r = 0.80), whereas ALA-D activity was negatively correlated with Pb in blood ( r = −0.70) and in edible tissues ( r = −0.59). Five statistically significant relations between Pb and Zn in blood and ALA-D activity were determined. The two models that explained the highest percentage (> 74%) of the total variance also included factors related to Hb concentration. All five significant models included negative coefficients for variables that represented Pb in blood and positive coefficients for Zn in blood. The ALA-D assay with results standardized to Hb concentration represents an expedient alternative to the more traditional hematocrit standardization, and the measurement of ALA-D activity by this method can be used to document exposure of fish to environmental Pb.

Missouri↗