Response of Zooplankton and Phytoplankton Communities to Creosote-Impregnated Douglas Fir Pilings in Freshwater Microcosms

Creosote has been used extensively as an industrial wood preservative for the protection of marine pilings, railway ties, and utility poles and is a common source of polycyclic aromatic hydrocarbons (PAHs) into aquatic environments. At present, there is little information by which to judge the potential for creosote leached from impregnated pilings to cause toxicity to biota in aquatic environments. The objective of the current study was to assess the effects of creosote on zooplankton and phytoplankton populations in freshwater microcosms in relation to changes in the concentration and composition of PAHs leached from creosote-impregnated Douglas fir pilings during an 83-day exposure period. The study consisted of single microcosms containing one half, one, two, three, four, and six treated pilings. Two microcosms that received untreated pilings were used as controls. The total surface area of pilings in each microcosm was normalized by adding the appropriate number of untreated pilings. Samples were collected periodically between –14 and 83 days pre- and post-exposure to determine aqueous concentrations of 15 priority PAHs and to assess the response of zooplankton and phytoplankton communities. Plankton community response to creosote was analyzed using principle responses curves. Peak aqueous concentrations of PAH occurred at day 7, ranging from 7.3 to 97.3 g/L. Zooplankton abundance decreased in all microcosms after introduction of the impregnated pilings, with the magnitude of response varying as a function of aqueous creosote concentration. Using inverse regression, a no-observed-effect concentration for the zooplankton community of 11.1 g/L was estimated. In contrast, algal abundance and diversity increased in all treatments between 7 and 21 days and attained levels up to twice that in control microcosms. This trend most likely reflected decreased grazing pressure because of the decrease in zooplankton populations, but it may also have reflected growth stimulation resulting from exposure to various constituents within the creosote mixture. Our results indicate that creosote leached from impregnated pilings deployed under typical conditions (e.g., wharves) may cause transient toxicity to benthic or limnetic communities shortly after deployment, but this likely poses few long-term risks to aquatic freshwater plankton communities.     

The toxicity of selenium in experimental freshwater ponds

Flue Gas Desulphurization equipment installed in coal-fired power stations to reduce sulphur dioxide emissions produces effluent containing several contaminants, including selenium. To assess the effects that this might have on fish reproduction and biological community richness, selenate and selenite were added to freshwater pond systems to achieve duplicated nominal concentrations of 0 (control), 2, 10 and 25 g Se/L. Perch (Perca fluviatilis), grass carp (Ctenopharyngodon idella Val.) and stickleback (Gasterosteus aculeatus) were placed in each pond in the early summer and left relatively undisturbed until the following spring. A spawning tray was then placed in each pond and monitored regularly for the appearance of perch egg ropes. When ropes were found, they were removed to the laboratory and either placed in uncontaminated well water or exposed to selenium. Almost half the perch exposed to 25 g Se/L died during the pond experiment, but there were no observed deaths at the lower concentrations. No grass carp were recovered from the 25 g Se/L ponds but all were recovered from the other ponds. Stickleback were missing from all treatments, presumably due to predation by the perch. Perch egg ropes were found in seven of the eight ponds, and all but one rope showed signs of successful fertilisation. Hatching success in the laboratory was highly variable for eggs obtained from the 0, 2, and 10 g Se/L ponds, but was always above zero. No eggs hatched from ropes obtained from the 25 g Se/L ponds. Effects of selenium on plants, macroinvertebrates and zooplankton in the ponds were generally limited. Accumulation of selenium in fish was dose-related and comparable with results reported from other contaminated systems. The results from this experiment suggest that mean environmental concentrations of approximately 25 g Se/L may seriously affect the reproductive capacity of perch, but no clear effects on reproduction are evident at mean concentrations of 10 g Se/L and below. Selenium-induced effects occur during gametogenesis, but only become evident between fertilization and hatching.     

Effects of atrazine on freshwater microbial communities

A multispecies toxicity test system using naturally derived microbial communities on polyurethane foam substrates was used to evaluate the toxic effects of the herbicide atrazine. Both structural (e.g., protozoan species number, biomass) and functional (e.g., colonization rate, oxygen production) community responses were measured. Oxygen production and the ability of communities to sequester magnesium and calcium were the most sensitive measures of toxic stress due to atrazine (maximum allowable toxicant concentrations [MATCs]=17.9 g/L). Dissolved oxygen was 33% lower, and there was 15% less calcium and magnesium in communities at and above 32.0 g/L atrazine compared to controls. Species richness and estimates of biomass (total protein and chlorophyll a) were less sensitive (MATCs=193) to atrazine. At the highest atrazine concentration (337 g/L), species numbers were 30% lower than controls, and protein and chlorophyll a content of communities were reduced by 38 and 91%, respectively. Low levels of atrazine (3.2–32.0 g/L) resulted in a 46% increase in species numbers and a greater concentration of total protein and chlorophyll a (41 and 57%, respectively). Results compared well with other estimates of chronic toxicity for effects of atrazine on aquatic communities. Reported MATCs ranged from 70.7 to 3,400 g/L. The results from this test emphasize the importance of monitoring both structural and functional measures of community integrity in toxicity testing with multispecies.     

Development of a Sublethal Test to Determine the Effects of Copper and Lead on Scleractinian Coral Larvae

A new sublethal toxicity test was developed in this study to measure the effect of copper and lead on the motility of coral larvae. Larval motility was significantly affected by copper and lead doses immediately after dosing. The copper EC₅₀ values for motility of Goniastrea aspera brain coral larvae (12 h, 21 g/L; 24 h, 16 g/L; 48 h, 22 g/L) were much lower than the copper LC₅₀ values for G. aspera larval survival (6 h, 260 g/L, and 24 h, 121 g/L, for 5-day-old larvae and 6 h, 248 g/L, and 24 h, 136.64 g/L, for 6-day-old larvae) during the early part of the experiments. However, at later times, the LC₅₀ values (48 h, 40 g/L, for 5-day-old larvae and 48- h, 87 g/L, for 6-day-old larvae) were similar to the EC₅₀ values for larval motility. The lead 72-h EC₅₀ value for G. aspera larval motility (2900 g/L) was much lower than the lead 72-h LC₅₀ value for larval survival (9890 g/L). The results show that larval motility can be a useful parameter to measure in order to determine the sublethal effects of trace metals on coral larvae.     

Uptake and phytotoxicity of soil-sorbed atrazine for the submerged aquatic plant,Potamogeton perfoliatus L.

The photosynthetic inhibitory effect of atrazine-sorbed soil placed on the leaf surfaces ofPotamogeton perfoliatus was investigated under laboratory conditions. Leaves simultaneously exposed to atrazine both in solution and sorbed to soil exhibited a similar uptake of atrazine and associated photosynthetic reduction as did leaves exposed to the same concentration of atrazine in solution only. A small quantity of atrazine (0.19 /gdw leaf) was found in leaves treated with atrazine-sorbed soil at 120 /kg whereas a significantly larger amount (3.57 g/gdw leaf) was present in leaves treated with dissolved atrazine at a concentration of 100 g/L. It is concluded that atrazine sorbed to soil on leaf surfaces is less available for uptake by aquatic plants than atrazine in solution. Of greater physiological concern is the physical presence of the soil on the leaves and the resultant reduction of light.     

Effects of different dietary levels of cadmium,lead, copper,and zinc on the vitality of the forest pest insect Lymantria dispar L. (Lymantriidae,Lepid)

Lymantria dispar (gypsy moth) larvae were reared on both a natural diet of oak leaves and an artificial medium contaminated independently with four different metal nitrates. Larvae were contaminated up to pupation either from 1st or 4th instars at four concentrations differing by a factor of 5. The lowest concentration levels were 2 g/g Cd, 4 g/g Pb, 10 g/g Cu, and 100 g/g Zn based on nutrient medium dry weight. Developmental rate, growth, mortality and reproductive success were determined. No-Observed-Effect-Concentrations (NOECs) calculated were dependent on the metal, the parameter investigated and the stage at which exposure commenced. In general, larvae exposed from the 4th instar were less susceptible to metal toxification than those exposed from hatching. Considering all parameters investigated, dietary NOECs were determined to be 2 g/g Cd, 4 g/g Pb, 10 g/g Cu, and 100 g/g Zn.     

Effects of atrazine and paraquat on nitrifying bacteria

The influence of atrazine and paraquat on a mixed culture of nitrifying bacteria was studied in an aqueous system. At a concentration as low as 1 g/mL paraquat exerted a complete inhibition of ammonium and nitrite oxidation for 40 days. Atrazine (1 g/mL and 2 g/mL), however, caused only an inhibition of ammonium oxidation for a short period. After 16–18 days of inhibition the ammonium oxidizing activity was resumed. In the presence of atrazine (1 g/mL), however, the rate of nitrite oxidation was increased. Within a period of 28 days, in culture media a partial degradation of atrazine occurred.     

Toxicity of mercury,copper, nickel,lead, and cobalt to embryos and larvae of zebrafish,Brachydanio rerio

The toxicity of mercury (HgCl₂), copper (CuCl₂: 5 H₂O), nickel (NiSO₄: 6 H₂O), lead (Pb(CH₃COO)₂: 3 H₂O) and cobalt (CoCl₂: 6 H₂O) was studied under standardized conditions in embryos and larvae of the zebrafish,Brachydanio rerio. Exposures were started at the blastula stage (2–4 h after spawning) and the effects on hatching and survival were monitored daily for 16 days. Copper and nickel were more specific inhibitors of hatching than cobalt, lead, and mercury. Nominal no effect concentrations determined from the dose-response relationships (ZEPs, Zero Equivalent Points) for effect on hatching time were 0.05 g Cu/L, 10 g Hg/L, 20 g Pb/L, 40 g Ni/L and 3,840 g Co/L, and those for effect on survival time were 0.25 g Cu/L, 1.2 g Hg/L, 30 g Pb/L, 80 g Ni/L, and 60 g Co/L. The no effect concentrations for Ni, Hg and Pb are consistent with previously reported MATC values for sensitive species of fish. The no effect concentrations for copper are 1–2 orders of magnitude lower than previously reported values. The major reason for the latter discrepancy was considered to be the absence of organics that can complex copper ions in the reconstituted water that we used, which had a hardness of 100 mg/L (as CaCO₃) and a pH of 7.5–7.7. Unexposed controls were started with embryos from different parental zebrafishes and the parental-caused variability in early embryo mortality, median hatching time and median survival time were estimated.     

Toxicity of seleno-L-methionine, seleno-DL-methionine, high selenium wheat, and selenized yeast to mallard ducklings

The toxicity of four chemical forms of selenium (seleno-L-methionine, seleno-DL-methionine, selenized yeast, and high selenium wheat) was compared in day-old mallard ducklings (Anas platyrhynchos). In the first experiment, in which the basal diet was 75% wheat, survival after 2 weeks was lower for ducklings fed 30 g/g selenium as seleno-L-methionine (36%) than for ducklings fed 30 g/g selenium as seleno-DL-methionine (100%) or 30 g/g selenium from high selenium yeast (88%). The concentration of selenium at 2 weeks in the livers of survivors was similar for ducklings fed 15 g/g selenium as seleno-DL-methionine (12 g/g, wet weight), seleno-L-methionine (11 g/g), and high selenium wheat (11 g/g), but was lower when the selenium came from selenized yeast (6.2 g/g). When fed 30 g/g selenium from the various sources, the selenium concentrations in liver were 20 g/g for seleno-DL-methionine, 19 g/g for seleno-L-methionine, and 9.9 g/g for selenized yeast. In a second experiment, in which the basal diet was a commercial duck feed, survival after 2 weeks was 100% in ducklings fed 30 g/g selenium as seleno-DL-methionine, seleno-L-methionine, or selenized yeast. Selenium concentrations in liver were similar for ducklings fed the 30-g/g selenium diets as the DL or L forms of selenomethionine (27 and 25 g/g), but lower for ducklings fed selenized yeast (13 g/g). The greater toxicity of the L form of selenomethionine was probably related to the palatability or nutritional nature of the wheat-based diet used in experiment 1, but the exact reason for the difference between the DL and L forms is unknown. Biologically incorporated selenium, derived from high selenium wheat, was no more toxic than selenium derived from the two purified forms of selenomethionine, and the selenium in selenized yeast was not as toxic as that in the two forms of selenomethionine.     

Atrazine uptake,photosynthetic inhibition,and short-term recovery for the submersed vascular plant,Potamogeton perfoliatus L.

The processes of atrazine (2-chloro-4-[ethylamino]-6-[isopropylamino-]-s-tri-azine) uptake and release in the submersed vascular plant,Potamogeton perfoliatus L., were rapid, approaching equilibrium with the surrounding environment within one hr. The ratio of internal atrazine concentration to external concentration was approximately 10 at the point of maximum photosynthetic inhibition and rapidly increased at lower external atrazine concentrations. The I₅₀ (the concentration inhibiting photosynthesis by 50%) for atrazine in solution was 80 g/L with the maximum observed photosynthetic reduction (87%) at a solution concentration of 650 g/L. Initial photosynthetic recovery ofP. perfoliatus following exposure to atrazine was rapid with oxygen evolution from treated plants (5, 25, and 100 g/L) being statistically indistinguishable from control plants after two hr of atrazine-free wash. However, there was an indication of residual photosynthetic depression in dosed plants, even after a 77 hr recovery period. In Chesapeake Bay, potential long-term exposure of submersed plants to concentrations of atrazine greater than 10 g/L is doubtful so that reduction ofP. perfoliatus photosynthesis under such conditions would be minimal and reversible.     

Short-term exposure of zooplankton to the synthetic pyrethroid,fenvalerate, and its effects on rates of filtration and assimilation of the alga,Chlamydomonas reinhardii

In acute tests of toxicity, two cladocerans,Daphnia galeata mendotae andCeriodaphnia lacustris, and the calanoid,Diaptomus oregonensis, were more sensitive to fenvalerate thanDaphnia magna, the organism used in standard laboratory bioassays. The 48-hr EC₅₀s for each species/stage in order of increasing sensitivity were adultD. magna — 2.52 g/L;D. magna (48-hr old) — 0.83 g/L; adultD. galeata mendotae — 0.29 g/L; adultC. lacustris — 0.21 g/L;D. galeata mendotae (48-hr old) — 0.16 g/L; adultDiaptomus oregonensis — –0.12 g/L. No toxicity was observed when these organisms were exposed to a range of concentrations of the emulsifiable concentrate without fenvalerate (the EC blank).Rates of filtration of the¹⁴C-labelled alga,Chlamydomonas reinhardii byD. galeata mendotae, C. lacustris andD. oregonensis were decreased significantly at sublethal concentrations of fenvalerate after only 24-hr exposure.Ceriodaphnia lacustris showed the greatest sensitivity with rates of filtration significantly decreased at 0.01 g fenvalerate/ L. Concentrations of fenvalerate 0.05 g/L resulted in decreased rates of filtration byD. galeata mendotae. A concentration of 0.10 g fenvalerate/ L caused rates of filtration to increase inD. oregonensis. whereas 0.05 and 0.5 g/L resulted in a decrease in these rates.Rates of assimilation of algae byD. galeata mendotae, C. lacustris andD. oregonensis exposed to similar concentrations of fenvalerate were decreased at concentrations 0.05 g fenvalerate/L. Changes in rates of assimilation were not as sensitive a parameter of toxicity as changes in rates of filtration. The EC blank had no significant effects on rates of filtration or assimilation for all three species.     

Biological and environmental monitoring of occupational exposure of pharmaceutical plant workers to methotrexate

Summary The exposure of 11 pharmaceutical plant workers to methotrexate (MTX) was studied. Personal air samples were taken during the different manufacturing processes: drug compounding, vial filling, and tablet preparation. The uptake of MTX was established by the determination of MTX in urine. MTX was analyzed using the fluorescence polarization immunoassay (FPIA), a method that is frequently used for monitoring serum levels in patients treated with MTX. The FPIA method was modified in such a way that MTX could be measured quickly and efficiently in air and urine samples. MTX was detected in air samples of all workers except for those involved in the vial filling process (range: 0.8–182 g/m³; median: 10 g/m³). The highest concentrations were observed for workers weighing MTX (118 and 182 g/m³). MTX was detected in urine samples of all workers. The mean cumulative MTX excretion over 72–96 h was 13.4 g MTX-equivalents (range: 6.1–24 g MTX-equiva g MTX-equivalents (range: 6.1–24 g MTX-equivalents). lents). A significantly lower background level of 10.2 g A significantly lower background level of 10.2 g MTX-equivalents was measured in urine of 30 control persons (range: 4.9–21 g MTX-equivalents).     

Some hygienic observations from the glass industry

Summary Metallic compounds and other agents used in the manufacturing of glass are probably responsible for the cancer risks observed for glassworkers, especially glassblowers. Few hygienic observations have been reported from the art glass industry. Three glassworks were therefore studied with regard to air concentrations of lead, arsenic, nickel and manganese. The hygienic conditions of the blow-pipes were investigated at these glassworks and another two with regard to inside deposits of slag containing lead, arsenic, manganese and nickel as possible transporters that cause oral exposure. Atomic absorption spectrophotometry was used for the analyses. Apart from lead, the metal concentrations in the air were around the detection limit. Glassworks producing heavy crystal glass usually had higher concentrations of lead in the air than the semi-crystal glassworks. Seven out of 12 samples from heavy crystal glassworks exceeded the Swedish threshold limit of 50 g/m³, while only four out of 28 samples from the semi-crystal glassworks exceeded this limit. Regarding metals in the slag from inside the blow-pipes, the concentrations (geometrical means) of lead and nickel were higher in the heavy crystal glassworks (6.9 g lead/mg slag, and 5.0 g nickel/mg slag versus 0.7 g lead/mg slag and 0.6 g nickel/mg slag in semi-crystal glassworks, respectively). The concentration of arsenic was similarly low in the pipes from all the glassworks ( 0.30 g/mg slag) and the concentration of manganese was only slightly higher in heavy crystal glassworks (5.4 g/mg slag versus 3.6 g/mg slag in semi-crystal glassworks).     

Organochlorine accumulation by sentinel mallards at the Winston-Thomas sewage treatment plant, Bloomington, Indiana

Farm-raised 12-month-old female mallards (Anas platyrhynchos) were released at the Winston-Thomas sewage treatment plant, Bloomington, Indiana. Five mallards were sacrificed at the start of the study and at approximately 10-day intervals through day 100. Concentrations of polychlorinated biphenyls (PCBs) in carcasses increased linearly with time of exposure and exceeded 16 g/g wet weight by day 100; PCBs in breast muscle exceeded 3.9 g/g by day 100. These PCB values are among the highest recorded for wild or sentinel waterfowl. PCB concentrations in breast muscle (26–523 g/g lipid weight) were 50–1,000 times greater than human consumption guidelines for edible poultry in Canada (0.5 g/g lipid weight) and 9–176 times greater than consumption guidelines for edible poultry in the United States (3.0 g/g lipid weight). Additionally, PCB concentrations in carcass and breast muscle exceeded the threshold of the Great Lakes Sport Fish Consumption Advisory do not eat category (1.9 g/g wet weight) by day 20 and day 50, respectively. Hepatic cytochrome P450-associated monooxygenases including BROD (benzyloxyresorufin-O-dealkylase), EROD (ethoxyresorufin-O-dealkylase), and PROD (pentoxyresorufin-O-dealkylase) were induced over 5-fold compared to reference mallards. BROD, EROD, and PROD were each significantly correlated to total PCBs and to the toxicity of selected PCB congeners, relative to 2,3,7,8-tetrachlorodibenzo-p-dioxin.     

The influence of contaminant and water quality conditions on larval striped bass in the Potomac River and upper Chesapeake Bay in 1990: Anin situ study

In situ contaminant and water quality studies were conducted with striped bass prolarvae,Morone saxatilis, in two major spawning areas of the Chesapeake Bay in 1990 to explore the possible effects of water quality and contaminants conditions on survival. Three 96-hin situ survival studies with striped bass prolarvae were conducted at three stations in the Potomac River and three stations in the upper Chesapeake Bay during a major portion of the spawning season (13–20°C). Water quality parameters, inorganic contaminants and organic contaminants were monitored in the water column at these three stations during the experiments. Concentrations of 10 metals associated with precipitation events occurring at field sites on the Potomac River and upper Chesapeake Bay were also determined.Survival of prolarvae ranged from 2 to 17.5% in all three 96-h tests conducted in the Potomac River. Control survival was greater than 79%. Survival of prolarvae during experiment 3 (all stations combined for each experiment) was significantly lower than survival of prolarvae during experiment 1. The low survival of prolarvae during experiment 3 occurred concurrently with a reported fish kill on the Potomac River. Chromium (14 g/L) and zinc (119 g/L) concentrations exceeding U.S. EPA water quality criteria were reported from a 48-h composite sample taken during experiment 3. Lower than normal pH conditions (6.8 and 6.9) were also documented during this experiment. Arsenic, chromium, and zinc may have been stressful.Survival of prolarvae at the three stations during upper Chesapeake Bay tests ranged from 36 to 52.5% for 96-h exposures but was slightly lower (23–34.5%) during a 120-h exposure. Control survival was >81% in all experiments. Survival of prolarvae during all experiments in the upper Bay was similar to natural survival that occurs with this life stage. Adverse water quality and contaminant conditions were not reported in the upper Chesapeake Bay striped bass spawning area.Detectable concentrations of cadmium (0.80 and 0.89 g/L), aluminum (5.4 g/L), chromium (1.1 g/L), and zinc (2.5 g/L) were reported in acidic precipitation samples (pH 3.4) collected from the Potomac River site. Surface water concentrations of these metals did not increase in the Potomac River study area after the precipitation events. The following metals were detected in acidic precipitation (pH 4.06–5.12) in the upper Chesapeake Bay: 22.1 g/L Al; 1.1, 1.8, 2.3 g/L Cd; 1.2 g/L Cu; 2.7 and 3.1 g/L Pb and 4.6 g/L Zn. Concentrations of Al (22.1 g/L) and Pb (3.1 g/L) in precipitation corresponded with increased concentrations in the surface waters at a nearby station in the upper Chesapeake Bay study area.     

Susceptibility of clinical isolates of campylobacter pylori to 24 antimicrobial and anti-ulcer agents

Forty-nine isolates of Campylobacter pylori were tested for their susceptibility to twenty antibiotics and four anti-ulcer agents by an agar dilution technique. Penicillin and amoxycillin were the most active drugs (MIC₉₀, 0.06 /ml); erythromycin, cefazolin, minocycline, ciprofloxacin, ofloxacin and gentamicin were sligthtly less active (MIC₉₀, 1 g/ml). Moderate activity was found for doxycyclin, rifampin, nitrofurantoin, norfloxacin, pefloxacin, enoxacin, paromomycin, metronidazole and tinidazole. All strains were resistant to trimethoprim (MIC > 512 g/ml). Nalidixic acid (MIC₉₀, > 256 g/ml) and colistin (MIC₉₀, > 64 gg/m1) had little to no activity. Of four anti-ulcer drugs, only bismuth subcitrate showed activity (MIC₉₀, 64 g./ml).Strains resistant to all 4-quinolones were found in patients who had previously received ofloxacin as part of a clinical trial aimed at eradication of C. pylori. These isolates remained susceptible to amoxycillin, tetracyclines and to other classes of antibiotics.Corresponding author.     

Internal lead and cadmium exposure in 6-year-old children from western and eastern Germany

Lead and cadmium levels in blood and deciduous teeth (shed incisors only) of 6-year-old German children were determined in 1991 in a large epidemiological study carried out in rural and urban areas of western Germany (Duisburg, Essen, Gelsenkirchen, Dortmund, Borken) and eastern Germany (Leipzig, Halle, Magdeburg, Osterburg, Gardelegen, Salzwedel). In total, blood lead and cadmium levels of 2311 German children and tooth lead and cadmium levels of 790 German children were analyzed. Blood lead levels were generally low in all study areas with geometric means between 39.3 g/1 and 50.8 g/l in the western German and between 42.3 g/1 and 68.1 g/l in the eastern German study areas. The mean blood lead level of Turkish children (n = 213) living in the western German study areas was 50.1 g/l and thus 5.6 g/1 higher than the overall geometric mean of the western German children. The higher exposure may be explained by a higher oral uptake from food and different living conditions. These children were excluded from multiple regression analysis because they were all living in the western study areas. The mean tooth lead levels ranged between 1.50 and 1.74 g/g in the western and between 1.51 g/g and 2.72 g/g in the eastern study areas. Thus, they show a distribution pattern similar to blood. Blood and tooth lead levels were higher in urban than in rural areas and higher in the eastern German than in the western German study areas. With regard to the blood and tooth cadmium concentrations, no significant differences between the study areas could be found. The mean cadmium levels in blood ranged between 0.12 g/1 and 0.14 g/l and the mean tooth cadmium concentrations between 20.8 ng/g and 27.8 ng/g. Blood and tooth lead and cadmium levels of the eastern and western German children were thus mainly at a relatively low level in all rural and urban study areas. The study demonstrates and confirms that blood and tooth lead levels are influenced by several demographic, social, and environmental variables. The results indicate that there has been a further significant decrease of lead and cadmium exposure in western German children since our last epidemiological study carried out in the same study areas in 1985/1986.     

Human exposure to volatile halogenated hydrocarbons from the general environment

Summary The objective of this study was to assess individual human exposure to volatile halogenated hydrocarbons (VHH) under normal environmental conditions by means of biological monitoring, i.e. by the measurement of these compounds or their metabolites in body fluids, such as blood, serum, and urine. Blood samples of 39 normal subjects without known occupational exposure to these agents were examined for the occurrence of VHH. The following compounds were present in quantifiable concentrations in 60 to 95% of the blood samples examined: chloroform (median 0.2 g/l; range < 0.1–1.7 g/l), 1,1,1-trichloroethane (median 0.2 g/l; range < 0.1–3.4 g/l), tetrachloroethylene (median 0.4 g/l; range < 0.1–3.7 g/l). Trichloroethylene could be detected in 31% of all blood samples (median < 0.1 g/l; range < 0.1–1.3 g/l). In addition, the levels of trichloroacetic acid (TCA) were determined in serum and 24-h urine samples of 43 and 94, respectively, normal subjects. TCA was present in measurable concentrations in all serum and urine samples examined. The median of the TCA levels in serum was 21.4 g/l (range 4.8–221.2 g/l) and in urine 6.0 g/24 h (range 0.6–261.4 g/24 h). The results are discussed in relation to data from the literature on human exposure to VHH from the general environment, i.e. via air, food, and water. The upper normal limits calculated from the results of this investigation can be used to detect even minor excessive exposures to VHH.     

Long-term effects of dinoseb and paraquat,both individually and combined,on embryonic development and hatching success ofFasciola hepatica miracidia

Toxic effects of the herbicides dinoseb and paraquat, both individually and combined, on embryonic development and hatching ofFasciola hepatica miracidia were assessed by exposing the eggs to varying concentrations (0–20 g/ml) of each of the herbicides. The results showed that dinoseb has an LC₅₀ value of 4.3 g/ml, paraquat has an LC₅₀ of 4.9 g/ml and the mixture of both dinoseb and paraquat has an LC₅₀ of 7.1 g/ml. Based on the LC₅₀ values, dinoseb is slightly more toxic than paraquat on the tested organisms. The results also showed that the mixture of dinoseb and paraquat is significantly less toxic than the individual pesticides.Eggs ofF. hepatica cultured in either dinoseb or paraquat both individually and combined showed a delay of embryonic development and hatching of the miracidia. Eggs cultured in 0–2 g/ml of dinoseb, paraquat and their mixture, fully embryonated and hatched within 14–16 days, while eggs cultured in 4–6 g/ml of the same herbicides showed a delay of four days for embryonic development and hatching of their miracidia.     

Bioaccumulation and toxicity of selenium in Chironomus decorus larvae fed a diet of seleniferous Selenastrum capricornutum

The bioaccumulation and toxicity of selenium in a simple aquatic food chain was investigated by feeding a diet of seleniferous algae (Selenastrum capricornutum) to fourth instar midge (Chironomus decorus) larvae. Treatment diets consisted of S. capricornutum cultured in three concentrations of selenite (0, 10, and 40 g Se/L) and four concentrations of selenate (0, 4, 10, and 40 g Se/L). The seleniferous algae was freeze-dried and utilized as a diet for the midge larvae. The data show that, under laboratory conditions, a 96 h dietary exposure of 2.11 g Se/g dry weight significantly reduced larval growth at tissue concentrations 2.55 g Se/g dry weight. The results demonstrate that some invertebrates are very sensitive to dietary selenium exposure. When compared to similar studies with Daphnia magna, the data suggest that invertebrate primary consumers differ in the metabolism of dietary selenium.