An examination of human blood for the presence of volatile nitrosamines

Human blood was examined for the presence of volatile nitrosamines. Nitrosamines were detected by chemiluminescence and mass spectrometry after separation from blood by distillation and solvent extraction. N-nitrosodimethylamine was detected in all but one of 51 blood samples taken from 23 different people, at concentrations from the detection limit (0.1 μg/litre) to 1.4 μg/litre with a mean concentration of 0.5 μg/litre. N-Nitrosodiethylamine was detected in 11 samples, the detection limit being 0.1 μg/litre. No other volatile nitrosamines were detected. After a test meal of bacon, spinach, bread and beer, the concentration of N-nitrosodimethylamine increased. There was no appreciable difference between the nitrosamine concentrations in the blood of laboratory workers and in the blood of other people. Salivary nitrite concentrations measured semi-quantitatively concurrently with blood sampling varied considerably but showed no apparent correlation with blood nitrosamine levels. Measurements in rabbits given a continuous infusion of N-nitrosodimethylamine gave a clearance rate approximately equal to the blood flow through the liver and a volume of distribution of 1.2 litre/kg body weight. By applying these results to man, the body burden after the meal was calculated as 40–50 μg. This is substantially higher than the estimated weekly intake of volatile nitrosamines from food.     

Suppression of dimethylnitrosamine metabolism and toxicity by nitrososarcosine and other nitrosamines.

Groups of rats were pretreated with nitrososarcosine (NS), diethylnitrosamine (DEN), or dibutylnitrosamine (DBN) in order to observe potential effects on dimethylnitrosamine (DMN) toxicity and metabolism. NS and DEN completely suppressed DMN-induced inhibition of liver protein synthesis while the case with DBN was not as clear. DMN metabolism was effected by suppression of DMN demethylase activity, and an inhibition of RNA, DNA, and protein methylation by [¹⁴C]DMN by each nitroso compound.     

Occurrence of preformed volatile nitrosamines in preparations of some Nigerian medicinal plants: a preliminary report.

Preparations of some tropical plants of medicinal importance collected from the savannah vegetational belt of Nigeria were analysed for preformed volatile N-nitrosamines. N-nitrosamines were analyzed by chemiluminescence detection on a thermal energy analyzer (TEA) following gas chromatographic (GC) separation. Only N-nitrosodimethylamine (NDMA) in the range of 1.2-3.4 microg/kg was detected in four out of the 29 sample preparations. These preliminary data suggest that medicinal plant preparations may be due in part to microbial contamination, contributing to N-nitroso compound burden in many developing countries where ethnomedicine in still widely practised.     

Excretion of volatile nitrosamines in a rural population in relation to food and drinking water consumption.

Urinary excretion of volatile nitrosamines was assessed in 59 non-smokers living in a rural county of Québec, Canada. Water and food intakes were measured by means of a 24-hour recall. Nitrates were analyzed in the tap water of all participants (geometric mean=2.0 mg nitrate-N/L) and dietary intakes of nitrate and vitamins C and E were estimated via a validated Canadian food database. Urine was collected over the same 24-hour period and analyzed for nitrates by hydrazine reduction and for volatile nitrosamines by gas-chromatography/mass spectrometry. N-Nitrosopiperidine (NPIP) was found in urine samples from 52 of the 59 subjects. Geometric mean of NPIP urinary excretion was 67 ng/day and maximum value was 1045 ng/day. No other volatile nitrosamine was detected. There was a correlation between urinary nitrate excretion and total nitrate intake (r=0.71, P < 0.001). However, no relationship was found between urinary NPIP excretion and either nitrate excretion, dietary or water nitrate intakes. NPIP excretion was significantly correlated to coffee intake (r=0.40, P=0.002) and this relation was not modified by vitamin intake. We conclude that nitrate intake is not related to nitrosamine excretion in this rural population. The influence of coffee consumption on NPIP excretion deserves further attention.     

Interspecies sensitivity in the aquatic toxicity of aromatic amines

It is known that Daphnia magna is highly sensitive to aniline. The objective of this study is twofold: (i) to find out if also other aromatic amines are more toxic to Daphnia; and (ii) to investigate if also other species are more sensitive to the effects of aromatic amines. Sensitivity histograms of anilines have been constructed based on literature data, taken from several publications, for acute toxicity to several species. The sensitivity distributions show that in particular water fleas are highly sensitive to some of the aromatic amines. Data for the acute and chronic excess toxicity of anilines and other ‘polar narcotics’ for D. magna has been analyzed. Anilines are significantly more toxic than other polar narcotic compounds. In addition, the acute to chronic ratios in D. magna are also higher for anilines than for other ‘polar narcotics’. Finally, the effects of the position of the substituents on the excess toxicity to D. magna have been examined. Results show that excess toxicity is lower in case of ortho substituted aromatic amines. This may indicate a steric hindrance of the ortho substituent in the toxic process of anilines to daphnids.     

Prediction of chemical toxicity to aquatic organisms: ECOSAR vs. Microtox® Assay

This study was designed to compare the toxicities of various chemical explosives and related compounds to aquatic organisms as predicted by a luminescent bacterium assay (Microtox® assay) and by the computer program ECOSAR. Toxicities were rated “very toxic,” “toxic,” or “less toxic” using the same criteria as the published bacterium assay. The two methods agree for most of the 24 compounds studied, and the disagreements are about equally divided as to which method predicts the greater toxicity. Experimental toxicity data were available for 12 of the 24 compounds. With these data, ECOSAR made eight predictions that coincided with the experimental toxicity class, while the luminescent bacterium assay predicted seven. For 17 of 21 experimental LC₅₀ values, ECOSAR predicted log LC₅₀ within one log unit. Published 1998 John Wiley & Sons, Inc. Environ Toxicol Water Qual 13: 211–216, 1998     

Biotransformation, sex hormones, and toxicity of two volatile anesthetics in mice.

Male and female DBA 11 mice recovered from 1 hr of anesthesia with chloroform of fluoroxene apparently unharmed. However, many of the animals died within 24-48 hr after anesthesia. Pretreatment with phenobarbital increased, while pretreatment with a small dose of carbon tetrachloride decreased, this toxicity. Relatively more males than females died. Pretreatment with estradiol in males and testosterone in females reversed this ratio. We conclude that the murine toxicity of chloroform and fluoxene is dependent on biotransformation by hepatic microsomal enzymes and that the testosterone enhances postanesthetic toxicity of these agents.     

Dietary effects on the pharmacokinetics of three carcinogenic nitrosamines.

The concentrations of N-nitrosodimethylamine (DMN), N-nitrosodiethylamine (DEN), and N-nitrosodibutylamine (DBN) were monitored as a function of time in the blood and liver of rats fed either a normal diet or a diet marginally deficient in lipotropes. The disappearance of each nitrosamine from the blood showed first-order kinetics. Hepatic clearance of DEN and DBN also followed first-order kinetics, but the time dependence of DMN concentration in liver tissue showed an anomalous behavior. Diet-related differences in the pharmacokinetic data did not explain the variations in carcinogenicity caused by diet.     

Methylmercury stimulates the exhalation of volatile selenium and potentiates the toxicity of selenite

The aim of the present experiments was to investigate whether a single dose of 24 mumol/kg methylmercuric chloride (MeHgCl) in rats can influence the effect of an equimolar dose of sodium selenite (Na2SeO3) on body weight or the exhalation of dimethylselenide, a volatile metabolic product of selenium. Due to the difference in their single-dose toxicities, only selenite depressed body weight gain, when given alone. The experiments indicated that methylmercury, irrespective of whether it was given 1-2 h before, or at the same time as sodium selenite, potentiated the effect of the latter on body weight. Methylmercury also increased the exhalation of volatile selenium, but this effect decreased when the administration of selenite was delayed.     

Comparison of embryo toxicity using two classes of aquatic vertebrates

Toxicity tests of musk ketone (MK) and tetrabromobisphenol-A (TBBPA) on embryos were conducted in two amphibian species, Xenopus (Silurana) tropicalis and the Swedish native species Rana arvalis. TBBPA was also tested on fish embryos of Danio rerio. All species were tested in similar experimental setup. Musk ketone caused decreased heart rates at concentrations from 10 and 100 μg/L in R. arvalis and X. tropicalis, respectively. TBBPA caused effects at 1000 μg/L in all three species. The responses were comparable between all three species which supports the relevance for using data from non-native species in national risk assessment.     

Selenium toxicity: cause and effects in aquatic birds

There are several manners in which selenium may express its toxicity: (1) an important mechanism appears to involve the formation of CH(3)Se(minus sign) which either enters a redox cycle and generates superoxide and oxidative stress, or forms free radicals that bind to and inhibit important enzymes and proteins. (2) Excess selenium as selenocysteine results in inhibition of selenium methylation metabolism. As a consequence, concentrations of hydrogen selenide, an intermediate metabolite, accumulate in animals and are hepatotoxic, possibly causing other selenium-related adverse effects. (3) It is also possible that the presence of excess selenium analogs of sulfur-containing enzymes and structural proteins play a role in avian teratogenesis. L-selenomethionine is the most likely major dietary form of selenium encountered by aquatic birds, with lesser amounts of L-selenocysteine ingested from aquatic animal foods. The literature is suggestive that L-selenomethionine is not any more toxic to adult birds than other animals. L-Selenomethionine accumulates in tissue protein of adult birds and in the protein of egg white as would be expected to occur in animals. There is no suggestion from the literature that the levels of L-selenomethionine that would be expected to accumulate in eggs in the absence of environmental concentration of selenium pose harm to the developing embryo. For several species of aquatic birds, levels of Se as selenomethionine in the egg above 3 ppm on a wet weight basis result in reduced hatchability and deformed embryos. The toxicity of L-selenomethionine injected directly into eggs is greater than that found from the entry of L-selenomethionine into the egg from the normal adult diet. This suggests that there is unusual if not abnormal metabolism of L-selenomethionine in the embryo not seen when L-selenomethionine is present in egg white protein where it likely serves as a source of selenium for glutathione peroxidase synthesis in the developing aquatic chick.     

Top-priority fragment QSAR approach in predicting pesticide aquatic toxicity

In the framework of pesticide risk assessment, a fragment-based QSAR approach is presented to correlate LC50-96 h acute toxicity to the rainbow trout (Oncorhynchus mykiss). While there are other fragment-based modeling routes, our approach exploits the possibility of prioritizing fragments' contributions to toxicity. On the assumption that one fragment might be mainly responsible for the molecular toxicity, we developed a three-stage modeling strategy to select the most important moieties and to establish their priorities at a molecular level. This strategy was tested on a heterogeneous dataset containing 282 pesticides, collected under the EU-funded project Demetra. Quantitative toxicity prediction yielded good results for the training set (R2TR = 0.85) and the test set (R2TS = 0.75). The advantages and limitations of the current priority strategy are examined.     

Role of selenium toxicity and oxidative stress in aquatic birds

Adverse effects of selenium (Se) in wild aquatic birds have been documented as a consequence of pollution of the aquatic environment by subsurface agricultural drainwater and other sources. These effects include mortality, impaired reproduction with teratogenesis, reduced growth, histopathological lesions and alterations in hepatic glutathione metabolism. A review is provided, relating adverse biological effects of Se in aquatic birds to altered glutathione metabolism and oxidative stress. Laboratory studies, mainly with an organic form of Se, selenomethionine, have revealed oxidative stress in different stages of the mallard (Anas platyrhynchos) life cycle. As dietary and tissue concentrations of Se increase, increases in plasma and hepatic GSH peroxidase activities occur, followed by dose-dependent increases in the ratio of hepatic oxidized to reduced glutathione (GSSG:GSH) and ultimately hepatic lipid peroxidation measured as an increase in thiobarbituric acid reactive substances (TBARS). One or more of these oxidative effects were associated with teratogenesis (4.6 ppm wet weight Se in eggs), reduced growth in ducklings (15 ppm Se in liver), diminished immune function (5 ppm Se in liver) and histopathological lesions (29 ppm Se in liver) in adults. Manifestations of Se-related effects on glutathione metabolism were also apparent in field studies in seven species of aquatic birds. Reduced growth and possibly immune function but increased liver:body weight and hepatic GSSG:GSH ratios were apparent in american avocet (Recurvirostra americana) hatchlings from eggs containing 9 ppm Se. In black-necked stilts (Himantopus mexicanus), which contained somewhat lower Se concentrations, a decrease in hepatic GSH was apparent with few other effects. In adult American coots (Fulica americana), signs of Se toxicosis included emaciation, abnormal feather loss and histopathological lesions. Mean liver concentrations of 28 ppm Se (ww) in the coots were associated with elevated hepatic GSH peroxidase, depletion of hepatic protein bound thiols and total thiols, but a small increase in GSH. Diving ducks in the San Francisco Bay area exhibited a positive correlation between hepatic Se concentration and GSH peroxidase activity (r=0.63, P<0.05), but a negative correlation between hepatic Se and GSH concentration (r=-0.740, P<0.05). In willets (Catoptrophorus semipalmatus) from the San Diego area, positive correlations occurred between hepatic Se concentration and GSSG (r=0.70, P<0.001), GSSG:GSH ratio, and TBARS. In emperor geese (Chen canagica) from western Alaska, blood levels of up to 9.4 ppm occurred and were associated with increased plasma GSH peroxidase activity (r=0.62, P<0.001), but with decreased plasma GSSG reductase activity. When evaluating Se toxicity, interactive nutritional factors, including other elements and dietary protein, should also be taken into consideration. Further studies are needed to examine the relationship between different forms of environmentally occurring selenium, arsenic and mercury on reproduction, hepatotoxicity and immune function of aquatic birds. Further selenium nutritional interaction studies may also help to illucidate the mechanism of selenium induced teratogenesis, by optimizing GSH and other antioxidant defense mechanisms in a manner that would stabilize or raise the cell's threshold for susceptibility to toxic attack from excess selenium. It is concluded that Se-related manifestations of oxidative stress may serve as useful bioindicators of Se exposure and toxicity in wild aquatic birds.     

Micromethod for acute aquatic toxicity assessment using the green alga selenastrum capricornutum

The method is intended for use (a) as a screening test to estimate toxicity to phytoplankton and (b) as part of an integrated scheme for hazard assessment of waters and wastewaters.     

Comparative aquatic toxicity of the pyrethroid insecticide lambda-cyhalothrin and its resolved isomer gamma-cyhalothrin

In this review we compare the sensitivity of a range of aquatic invertebrate and fish species to gamma-cyhalothrin (GCH), the insecticidally active enantiomer of the synthetic pyrethroid lambda-cyhalothrin (LCH), in single-species laboratory tests and outdoor multi-species ecosystem tests. Species sensitivity distribution curves for GCH gave median HC₅ values of 0.47 ng/L for invertebrates, and 23.7 ng/L for fish, while curves for LCH gave median HC₅ values of 1.05 ng/L and 40.9 ng/L for invertebrates and fish, respectively. A model ecosystem test with GCH gave a community-level no observed effect concentration (NOEC_community) of 5 ng/L, while model ecosystem tests with LCH gave a NOEC_community of 10 ng/L. These comparisons between GCH and LCH indicate that the single active enantiomer causes effects at approximately one-half the concentration at which the racemate causes similar effects.     

A simple microplate algal assay technique for aquatic toxicity assessment

A simple, miniaturized algal assay procedure using microplates has been developed to assess aquatic toxicity with the green alga, Selenastrum capricornutum. Cell count-generated EC₅₀ data comparisons with the classic assay using flasks have indicated good agreement between the two methods following toxic assessment of various wastewater samples and metal solutions. Parametric comparisons (ATP us cell counts) with the microplate method show equally good correlation. The technique is highly versatile in conducting basic algal bioassays for varying times (4-hour, 4-day, 8-day EC₅₀'s) and with differing parameters, depending on set objectives. Other interesting features of the microplate technique include handling rapidity, economy, space-saving convenience, and automation potential.     

Response characteristics of an aquatic biomonitor used for rapid toxicity detection

The response characteristics of an aquatic biomonitor that detects toxicity by monitoring changes in bluegill (Lepomis macrochirus Rafinesque) ventilatory and movement patterns were evaluated in single chemical laboratory studies at concentrations near the 96-h LC(50) concentration and at the EILATox-Oregon Workshop in sequential tests of multiple unknown samples. Baseline data collected prior to exposure allows each fish to serve as its own control. When at least 70% of exposed fish exhibit ventilatory or movement parameters significantly different from baseline observations, a group alarm is declared. In the laboratory studies, the aquatic biomonitor responded to the majority of chemicals at the 96-h lc(50) within an hour or less, although substantially higher response times were found for malathion and pentachlorophenol. Workshop tests of single chemical concentrations presented as blind samples were consistent with the laboratory test results. There were no alarms under control conditions in any test. Although data are limited, the aquatic biomonitor appears to respond more rapidly to chemicals causing membrane irritation, narcosis or polar narcosis than to acetylcholinesterase inhibitors or oxidative phosphorylation uncouplers. All four monitored parameters (ventilatory rate, cough rate, ventilatory depth and movement) contributed to identification of first alarms at acutely toxic levels. Understanding these response patterns can be useful in data interpretation for biomonitor applications such as surface water monitoring for watershed protection, wastewater treatment plant effluent monitoring or source water monitoring for drinking water protection.     

Fate,behavior, and aquatic toxicity of the fungicide IPBC in the Canadian environment

Canadian water quality guidelines (CWQG) for 3‐iodo‐2‐propynyl butyl carbamate (IPBC) were developed based on a review of environmental chemistry, fate, and toxicology of IPBC. IPBC is used in Canada in antisapstain formulations for treatment of freshly sawn lumber, as an industrial mildewcide, and as an antimicrobial. In British Columbia, IPBC is an active ingredient in the most widely used antisapstain formulation (Kop‐Coat NP‐1); 36,020 kg of IPBC were used by lumber mills for antisapstain purposes in 1996. IPBC is moderately soluble in water, and is not likely to adsorb to suspended solids or sediments. It is not persistent in the water column; hydrolysis is expected to be the main route of dissipation. IPBC was reported to affect fathead minnows at levels as low as 0.019 mg L⁻ and Daphnia magna at levels as low as 0.07 mg L⁻¹. It is not expected to bioaccumulate. An interim water quality guideline for the protection of freshwater aquatic life of 1.9 μg L⁻¹ is recommended. This guideline was derived according to the Canadian Council of Ministers of the Environment's (CCME) Protocol for the Derivation of Water Quality Guidelines for the Protection of Aquatic Life, and is intended to be protective of all forms of freshwater aquatic life at all aquatic life stages. © 2000 John Wiley & Sons, Inc. Environ Toxicol 15: 201–213, 2000