The great French surgeon Leriche once said, "To be in good health is to live in the silence of one's organs." For Nature it is exactly the contrary, but one must not forget that the environment may strike in silence, as demonstrated by the accidents at Jintsu and Minamata in Japan. Close to 10 years were necessary to understand the mechanisms of deadly cadmium and mercury intoxications in humans. Two kinds of stresses to humans may come from the environment: (i) infectious disease, and (ii) unexpected, more-or-less complex chemical reactions.
The present groundwater standard of 0.1 microg/L for plant protection products (PPPs) has been under much debate because an ecotoxicological base is missing. In the present study, groundwater threshold values were calculated for all PPPs currently included in Annex I to Directive 91/414/EEC using three different approaches: (1) first-tier (Daphnia magna and Vibrio fisheri); (2) species sensitivity distributions, constructed for surrogate freshwater organisms for the truncated groundwater biodiversity; (3) the case-based model PERPEST. For the majority of the PPPs, the trigger value of 0.1 microg/L appears to be sufficiently protective. However, it may not fully protect groundwater life from several insecticides. Implications for the environmental risk assessment of groundwater and recommendations for future research are discussed.
Five dairy cows were fed 0–50 ppm diuron herbicide [3-(3,4-dichlorophenyl)-1,1-dimethylurea] for 33 days and samples of milk, blood, urine, and feces were collected at regular intervals during the experiment. Approximately 50% of the diuron was recovered in urine, 10% in feces, and 5% in blood. No herbicide was detected in milk. In general, there was a positive correlation in the concentration of diuron products between urine and blood and a negative correlation between urine and feces. However, the percentage excretion of diuron residues in urine, feces, or blood was consistent in all treatments. The remaining > 35% of diuron, which was not detected, could have been absorbed in the body or degraded into undetectable metabolites. Two diuron metabolites, 3-(3,4-dichlorophenyl)-1-methylurea (DCMU) and 3-(3,4-dichlorophenyl)urea (DCU), were identified and determined only in urine from animals treated with 25 and 50 ppm due to experimental difficulties. Moreover, DCMU and DCU accounted for 8 and 25%, respectively, of diuron intake.
The toxicity of 1,1,1-trichloroethane to carp (Cyprinus carpio) and daphnids (Daphnia magna) and the effects of gaseous-phase exposure on the growth of higher plants (Sorghum bicolor and Brassica napus) were investigated. The test systems were designed to minimize loss of the volatile material during the exposure period. During an exposure period of 14 days, there were no mortalities or other symptoms of toxicity in carp exposed to a mean measured 1,1,1-trichloroethane concentration of 7.7 mg/liter. The survival and reproduction of daphnids over a test period of 17 days were not affected at a measured concentration of 1.3 mg/liter. Growth of emergent seedlings was not inhibited at measured gaseous-phase concentrations of 18 mg/liter for S. bicolor and 6.9 mg/liter for B. napus. The simple modifications made to standard techniques proved sufficient to maintain the exposure concentrations of this volatile chemical. Mean measured concentrations were generally greater than 60% of the nominal values.
The metabolism of the xenobiotics 1,1,1-trichloroethane (TCE) or 1,1,2-trichloro-1,2,2-trifluoroethane and endogeneous substrates may be changed under physiological stress situations. We studied long-term effects on rats exposed to TCE, noise pollution, and their combination. The experiments were performed in a special set-up where four parallel groups of rats were simultaneously exposed to defined conditions the chemical vapor; the noise pollution of 90 dB; their combination; and a control group without any exposure. The vapor of TCE was applied at a concentration of 200 ppm/8 hr or of 2000 ppm/12 hr for 84 days each. The experiments were performed with TCE from two different commercial sources. One of those TCE preparations caused effects at the high dosage level in terms of enhanced levels of the relation of liver to body weight; liver microsomal protein content; liver microsomal monooxygenase activity; and 3,4-dihydroxyphenylglycol excretion in urine. Eight other physiological and biochemical parameters were not changed.
An analytical procedure specific for chlorinated benzo-1,2-quinones has been developed to examine the stability of these compounds under conditions used for investigating their toxicity to aquatic organisms. Solutions of the compounds in a number of organic solvents were unstable in the light, and addition of acetone solutions to water brought about rapid decomposition of the chloroquinones which had half-lives less than 0.5 hr: the corresponding chlorocatechols were the principal products. The kinetics of decomposition of tetrachlorobenzo-1,2-quinone in aqueous solutions were studied in detail and showed the formation of tetrachlorocatechol, 2,5-dichloro-3,6-dihydroxybenzo-1,4-quinone, 1,2,3-trihydroxy-4,5,6-trichlorobenzene, 1,2,4-trihydroxy-3,5,6-trichlorobenzene, dichloromaleic acid, and a trichlorocyclopentendione. In organic solvents in the light, 3,4,5-trichlorobenzo-1,2-quinone underwent a dismutation reaction with formation of 3,4,5-trichloro- and tetrachlorocatechol; in a comparable reaction, 4,5-dichlorobenzo-1,2-quinone formed 4,5-dichlorocatechol and 3,4,5-trichlorocatechol. The toxicity of aqueous solutions prepared by dilution of freshly prepared acetone solutions of tetrachlorobenzo-1,2-quinone was examined in the zebra fish embryo/larvae test, and it was found that the threshold toxic concentration could be accounted for entirely by the analytically established concentration of tetrachlorocatechol produced as a chemical transformation product. It is concluded that in toxicological examination of reactive compounds, exposure to the toxicant should be assessed from concentrations analytically determined during the experiments and that attention be directed to both the nature and the toxicity of the transformation products.
The effects of tetrachloro-1,2-benzoquinone (TCQ), a component in bleached kraft mill effluents (BKME), on vertebral and physiological parameters were investigated in juvenile fourhorn sculpin, Myoxocephalus quadricornis L. After about 4.5 months of exposure to 0.1 and 0.5 mg TCQ/liter in 7% salinity brackish water, the fish demonstrated vertebral deformities, aberrant mechanical properties of the vertebrae, effects on white and red blood cell counts, enhanced activity of delta-aminolevulinic acid dehydratase in erythrocytes, and increased levels of ascorbic acid in the liver. The effects are discussed in relation to those previously observed in fish exposed to complex BKME in the field and the laboratory.
Semivolatile organic compounds (SOC) occur in the troposphere either adsorbed at aerosol particles or in the free gas phase, depending on temperature, vapor pressure of the compound, and total particular surface. In order to estimate the abiotic degradation of such compounds, the OH reaction rate constant must be known, which cannot be measured directly in the gas phase at the relevant temperature due to experimental difficulties. In the method proposed here, the inert solvent 1,1,2-trichlorotrifluoroethane is used as the reaction medium and hydrogen peroxide as photolytic OH source. Relative reaction rates can be measured, using a reference compound of known kOH air. The relative rates can be converted into absolute ones due to the 1:1 relationship observed by Dilling, Gonsior, Boggs, and Mendoza (1988) Environ. Sci. Technol. 22, 1447-1453, between the relative rates in the inert solvent and those in the gas phase.
Most organic pollutants are supposed to act via the mechanism of nonpolar narcosis upon acute exposure. Because the chronic effects of these compounds are still relatively unknown, in this study a chronic toxicity experiment was performed with zebrafish, Danio rerio, exposed to 1,2,3-trichlorobenzene (123TCB), a nonpolar narcotic. Fish were exposed in a flow-through system for 68 and 147 days. Parameters measured are survival, growth, reproduction, and glycogen and protein content. The only parameter which was influenced was the number of eggs produced per female, resulting in an EC(50) of 40 microg/L. Using this value and acute toxicity data for 123TCB, an acute to chronic ratio (ACR) of 80 was calculated, which is larger than ACRs for other species exposed to nonpolar narcotics. This finding might indicate that compounds acting by nonpolar narcosis in acute tests can have completely different effects upon chronic exposure.
Specimens of either sex of the freshwater catfish, Clarias batrachus, were exposed to safe and sublethal concentrations of gamma-BHC (2 and 8 ppm) and cythion (1 and 4 ppm) for 4 weeks during different phases of annual reproductive cycle. Their effects on free fatty acids (FFA) and acyl glycerides, viz., monoglycerides (MG), diglycerides (DG), and triglycerides (TG), were studied in liver, plasma, gonads, and muscle. During the preparatory phase, both pesticides suppressed the levels of FFA and acylglycerides (MG, DG, and TG) in liver of either sex but had no effect on their levels in plasma, ovary, and muscle; however, FFA and TG were reduced in testis. Unlike the preparatory phase, in the prespawning phase different lipids responded variedly to the concentrations of both Cythion and gamma-BHC. In the female, FFA in liver and plasma was raised but in ovary and muscle it was decreased. Acylglycerides in studied tissues were also reduced except ovarian TG which was increased by both pesticides at safe concentrations. Contrary to this, in the male these lipids were raised in liver and testis. Moreover, during the spawning phase, these pesticides enhanced the hepatic FFA together with acylglycerides in the female but failed to elicit any change in their levels in the male. Plasma levels of FFA and TG were reduced in the female; however, in the male FFA was raised and TG remained unchanged. Ovarian FFA and TG were decreased and increased, respectively. During the postspawning phase, none of the lipid fractions could be affected in the male except hepatic FFA which was reduced; however, in the female TG along with FFA was decreased.
Dose-response studies were carried out on female F344 rats with two carcinogenic cyclic nitrosamines, nitroso-1,2,3,6-tetrahydropyridine (NTHP) and dinitrosohomopiperazine (DNHP). Groups of 20 rats were given the nitrosamines in drinking water solution, at concentrations ranging from 100 to 1 mg/liter of the former and 110 to 1.1 mg/liter of the latter, each lower dose being 40% of the dose above it. The lengths of treatment were 25 or 30 weeks at the higher concentrations, and were extended to most of the lifespan at the lower concentrations. The mortality rate of the animals with induced tumors of the upper gastrointestinal tract (and liver in the case of the highest dose of NTHP), decreased with lower doses at the higher concentrations. At the lower concentrations there was little effect on mortality rate, compared with untreated controls, but there were a number of rats with induced tumors of the upper GI tract and the incidence of these tumors increased with increasing dose of nitrosamine. Of the doses given, only the lowest dose of DNHP given for the shortest time was without significant carcinogenic effect. The relationship between dose of nitrosamine and carcinogenic potency, as measured by mortality rate, was linear over part of the range, but not at lower doses. The slopes of these dose responses differed between NTHP- and DNHP-treated animals, suggesting that the mechanisms of carcinogenesis by these two compounds are not identical.
Macrobenthic animal communities that colonized sand-filled aquaria were exposed to 1,2,4-trichlorobenzene (TCB), a recent replacement for polycholorinated biphenyls in the electrical industry. In one test, communities established by planktonic larvae entrained in continuously supplied unfiltered seawater for 50 days were exposed to waterborne TCB for 6 days; in the second test, the toxicant was added to the sediment before 8 weeks of colonization. Concentrations that affected community structure were usually two orders of magnitude lower for waterborne TCB than for sediment-bound TCB, but the same types of organisms were affected by each route of exposure. The lowest TCB concentrations (measured) that affected average numbers of individuals exposed via the water were 0.04 mg/liter for mollusks, 0.4 mg/liter for arthropods, and 4 mg/liter for annelids. Average number of species was significantly lower than the control at 4 mg/liter. For TCB exposures via the sediment, the lowest concentrations (nominal) that affected average numbers of individuals were 100 micrograms/g for mollusks and echinoderms, and 1000 micrograms/g for arthropods and annelids. Average number of species in experimental aquaria was significantly lower than the control at greater than or equal to 100 micrograms/g. TCB persisted in sediments, but some leached into water throughout the 8-week exposure via sediment.
Adult Eisenia fetida earthworms were exposed to sub-lethal concentrations of 1,2,4-trichlorobenzene to assess the toxicity of contaminated soils. The LC₅₀ of 1,2,4-TCB at 7 and 14 d were 945±175 and 890±169 mg kg⁻¹. A lower dose of 1,2,4-TCB (25 mg g⁻¹) had stimulatory effects on SOD and AChE activities, but AChE activities were significantly inhibited at higher treatment levels (100 and 400 mg g⁻¹). SOD activities increased after 2, 7, and 14 d of exposure, but AChE activities were significantly inhibited at 400 mg/kg 1,2,4-TCB after 2, 7, and 14 d of exposure, and the inhibition rates were 25.41%, 28.65%, and 25.05%. Ultrastructural observation of the intestinal epithelium at three concentrations (control, 50, and 400 mg g⁻¹) revealed that the epicuticle, cuticle layer, and microvilli were damaged with increasing 1,2,4-TCB concentration. At 400 mg kg⁻¹, mitochondria were seriously injured and the smooth endoplasmic reticulum was seriously dilated.
The performance of the free polyamines as plant stress indicators is studied in barley and rape plants grown in nutrient culture, by exposure to Cr(VI) or Cr(III) in concentrations ranging from 0 to 100 ppm. Putrescine levels are elevated up to 10 times in the leaves of stressed plants compared to those of control plants, but neither spermidine nor spermine show any consistent reactions on the stress. Cr(VI) is more toxic than Cr(III) and induces putrescine accumulation quicker than Cr(III). Chromium concentrations in leaves reach 3000-5000 ppm (dry wt) after exposure to 100 ppm Cr(VI) and 300-400 ppm (dry wt) following exposure to 100 ppm Cr(III). Simultaneously with, or following shortly after the putrescine induction, reductions in root growth, chlorosis, induction of leaf chitinase activity, and, later, reduced shoot growth and lowered water content in leaves are observed. The pattern of the effects indicates that the basal toxicity mechanism of the two chromium species is connected to disturbance of the normal function of the root. Putrescine induction is an integrated part of the response mechanism of the stressed plants, appearing as an early sign of stress. However, the chromium concentration of the leaves as a warning of chromium-induced stress is judged to be an even more sensitive indicator.
With the advances in nanotechnology, silver nanoparticles (AgNPs) have been applied in many industries, increasing their potential exposure level in the environment, yet their environmental safety remains poorly evaluated. The possible effects of different sized AgNPs (20, 30-60, 70-120 and 150nm diameter) on jasmine rice, Oryza sativa L. cv. KDML 105, were investigated at different concentrations (0.1, 1, 10, 100 and 1000mg/L) upon seed germination and seedling growth. The results revealed that the level of seed germination and subsequent growth of those seedlings that germinated were both decreased with increasing sizes and concentrations of AgNPs. Based on the analysis of AgNPs accumulation in plant tissues, it implied that the higher uptake was found when the seeds were treated with the smaller AgNPs, 20nm diameter AgNPs, but it was trapped in the roots rather than transported to the leaves. These resulted in the less negative effects on seedling growth, when compared to the seed soaking with the larger AgNPs with 150nm diameter. The negative effects of AgNPs were supported by leaf cell deformation when rice seeds were treated with 150-nm-diameter AgNP at the concentration of 10 or 100mg/L during seed germination. These results further strengthen our understanding of environmental safety information with respect to nanomaterials.
This study explored the suitability of using the trans/cis ratio of unsaturated fatty acids as an indicator of the acute toxicity of membrane active hazardous chemicals. The conversion of cis into trans fatty acids in Pseudomonas putida NCTC 10936 in response to 4-chlorophenol and temperature changes was compared with the results from another kind of toxicity test using the same organism, based on the sensitivity of its xylose oxidation-driven ATP synthesis to uncoupling. The response of both indicators is believed to be largely due to changes in the fluidity of the cytoplasmic membrane. However, the electron transport phosphorylation reacted faster and more sensitively to the fluidizing effect of 4-chlorophenol than the isomerization of unsaturated fatty acids. Therefore, measuring the trans/cis ratio does not provide as good early warning signals of acute toxicity as monitoring the response of the electron transport phosphorylation. If used as an indicator of chemostress, with Pseudomonas species as test organisms, the ratio should only be used in conjunction with other parameters reflecting the energetic state of the cells.
The metabolism in the rat of 109Cd biocomplexes present in the tissues of the edible mussel Mytilus galloprovincialis, previously exposed to 109CdCl2, was studied. The tissue distribution and binding of 109Cd were compared to those caused by an equal dose of 109Cd as CdCl2 or rat liver Cd-metallothionein. Administration of mussel 109Cd to rats resulted in an initial accumulation of 109Cd in the kidneys due to the presence of 109Cd-metallothionein, which constituted 25% of the 109Cd in the tissues of the mussels. Other 109Cd biocomplexes present in the mussel tissues were metabolized in the rat in a way similar to that of inorganic cadmium, i.e., initial accumulation in the liver. These findings indicate that the ingestion of seafood rich in metallothionein may give rise to a faster increase of renal cadmium levels than the consumption of a similar amount of inorganic cadmium.
Soybean fields provide habitats for many species of amphibians. However, the persistence and health of amphibian populations may be at risk from the increasing use of pesticides and other agricultural chemicals. We examined the activities of acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and carboxylesterases (CbEs) in 11 syntopic species of larval anurans. In vitro effects of malaoxon causing 50% BChE inhibition (IC(50)) were also studied. In addition, we calculated a relative risk index (RI) based on the geographic distributions of the anurans, the phenology of soybean cultivation, and basal enzymatic values related to potential pesticide detoxification. Among the 11 species, AChE activity varied from 17.5 ± 1.6 to 68.2 ± 4.7 nmol min(-1) mg(-1) protein (PT). BChE activity also varied significantly, ranging from 3.3 ± 0.4 to 7.5 ± 0.4 nmol min(-1) mg(-1)PT. Both measures of CbE activities varied widely (CbE α-NA: 2.1 ± 0.5-12.4 ± 1.1 nmol min(-1) mg(-1) PT; CbE-4NPV: 21.8 ± 1.8-102.6 ± 7.9 nmol min(-1) mg(-1) PT). We also corroborate that lower BChE activity levels for the tadpoles were associated at minor IC(50) values. The results of this study demonstrate significant variation in enzymatic levels among several tadpole species and intermediate to high RI values for 7 species. Based on these results, it appears that a conversion of native ecosystems to soybean crops may lead to increased ecological risk for anuran amphibians.
The toxicity of the nonylphenol polyethoxylate, R-11 and the neonicotinoid insecticide, imidacloprid were evaluated on the crustacean, Ceriodaphnia dubia Richard. These compounds were evaluated separately and as a mixture because they are applied for pest control and may exist as a binary mixture in surface water. Acute mortality estimates (48h) were developed followed by population-level studies after chronic exposure. LC50s and 95% CL for R-11 and imidacloprid were 9241 (8521-9842)microg/l and 2.1 (1.1-3.4)microg/l, respectively. In the population study, C. dubia were exposed to concentrations equivalent to the acute LC25 for R-11 (8090microg/l) and imidacloprid (0.3microg/l) separately and as a mixture for 8d. The results of the chronic study indicated that R-11 had a greater impact on population parameters than imidacloprid and the mixture had a greater impact than either compound alone. For example, the total number of individuals at the end of the chronic study was 73%, 19%, and 6% of the control for imidacloprid, R-11, and the binary mixture, respectively. Additionally, exposure to R-11, imidacloprid, and the mixture resulted in 52%, 10%, and 91% reductions in population growth rate compared to the control, respectively. The results of this study indicate that when combined, R-11 and imidacloprid act in a more than additive manner. Therefore, it is important that their potential effects on aquatic organisms be evaluated together.
A standardized bioassay previously developed with ivermectin for the yellow dung fly (Scathophagidae) and the face fly (Muscidae) was applied to test the response of 11 dung fly species to the presumably less toxic parasiticide moxidectin. The results were compared to existing data for the same species tested with ivermectin, albeit two new species (Scathophaga suilla and Musca domestica) were tested here with both the substances. Estimated lethal effect concentrations LC50 at which 50% of the flies died ranged more than tenfold from 0.012mg moxidectin/kg fresh dung for Sepsis neocynipsea (Sepsidae) to 0.140mg moxidectin/kg fresh dung for the house fly Musca domestica (Muscidae). In most of the species, we additionally revealed sub-lethal effects at lower moxidectin concentrations in terms of retarded growth and development and reduced body size. Mortality thresholds were about ten times higher for moxidectin than for ivermectin, hence moxidectin is indeed less toxic than ivermectin in absolute terms. Crucially, we obtained strong correlations among the 11 tested fly species in both lethal and sub-lethal responses to the two substances, such that species relatively sensitive to ivermectin were also relatively sensitive to moxidectin. Such correlations are expected if the two substances are structurally related and function in the same manner by disturbing ion channel transport. Methodologically speaking, all species used proved suitable for toxicological testing of parasiticides.
The main objective of this work was to use micronucleus induction in fish erythrocytes to study the risk to aquatic ecosystems due to the genotoxicity of Chlorotriazine Reactive Azo Red 120 textile dye. The frequencies of micronuclei were studied for three low doses of 1, 5, and 10 mg/L and blood sampling was carried out on the same fish after 3, 6, and 9 days. It was found that micronuclei increased not only in a dose-dependent manner but also in a time-dependent way, compared with negative (tap water) and positive (10 ppm benzene) control groups. There was also a slight, time-dependent increase in erythrocyte micronuclei of the control fish specimens. This study proved the genotoxicity of this dye, and suggests that further studies should be made on other dyes and some other toxic industrial pollutant discharges in water ecosystems, using fish as an indicator to monitor pollutant genotoxicity.
Over the last decades, amphibians decline has been reported worldwide. Exposure to polychlorinated biphenyls (PCBs) is one of the possible causes in addition to climate changes, UV-radiation or habitat destruction. In the present study, we tested the hypothesis that PCBs could induce oxidative stress in young tadpoles. Developing Xenopus laevis were exposed from 2- to 5-d postfertilization (pf) to 0.1 or 1 mg/l of Aroclor 1254. Lipid peroxidation and antioxidant systems (SOD, CAT, GST, GPx, GR activities and t-GSH level) were investigated in whole organisms. Exposure to both concentrations did not impact on the survival and development whereas the average body weight decreased. Exposure to 1 mg/l of Aroclor 1254 induced a significant (p<0.05) increase of GST activity when compared to controls 0 and DMSO. The other antioxidant enzymes and LPO evaluation remained unchanged. Our results demonstrate that exposure of X. laevis tadpoles to environmental concentrations of Aroclor 1254 interfere with normal growth. They also highlight that very young X. laevis tadpoles express antioxidant systems.