Effect of temperature on the evolution of n-butyl isocyanate from aqueous Benlate® formulations

Rates of n-butyl isocyanate (BIC) evolution from Benlate^® DF and WP formulations were determined at temperatures from 25 to 40°C. The aqueous Benlate^® mixture was added to a glass bottle containing basaltic gravel, and the gas phase BIC carried to an XAD-2 cartridge by a stream of air. The trapped BIC was eluted and analyzed by gas chromatography. For older samples obtained from a grower, the average rate of BIC evolution in the first 6 h in DF increased by more than 10-fold to 25 g/h (3.6 ppm in the head space) when the temperature was increased from 25 to 40°C. In the WP sample, the increase was 3.8-fold to 3.5 g/h (0.5 ppm). These results demonstrate that aqueous Benlate^® formulations produced higher levels of BIC under elevated temperatures, especially when Benlate^® DF was used.     

The effect of hexavalent chromium on the critical thermal maximum and body burden ofClioperla clio (Plecoptera:Perlodidae)

Clioperla clio (Plecoptera:Perlodidae) nymphs exposed to eight levels of hexavalent chromium experienced 0.03% (control) to 76.0% lethality after 96 hr at 9.0°C and had an LC50 of 101.3 mg/L (95% C.I.=88.9 – 118.1 mg/L). Nymphs exposed to sublethal levels of Cr⁺⁶ in EPA hardwater at 9.0°C had statistically significant reduction in upper temperature tolerance measured as critical thermal maximum (CTM_CONTROL > > , range 31.46–29.49°C). The ecological death endpoint criterion resulted in low variability for controls (C.V.=2.4%). Exposed nymphs digested with nitric acid had mean body burdens ranging from 1.37 (g total Cr/g dry weight) for those exposed to 5.25 mg/L, to 26.71 for the 143.25 mg/L exposure group. As Cr⁺⁶ exposure increased, body burden of nymphs increased linearly, and CTM significantly decreased. Since the 96-hr LC50 greatly exceeds Cr⁺⁶ measured in the field and the critical thermal maxima are at least 10°C greater than the adult emergence temperature, it is unlikely that environmentally realistic combinations of Cr⁺⁶ and temperatures will have adverse impacts on mature nymphs ofClioperla clio in nature if adverse conditions are of short duration.     

Control of the freshwater fouling bivalveCorbicula fluminea by halogenation

Mortality levels for adult and juvenile Asiatic clam,Corbicula fluminea, were determined after exposure to halogens (chlorine, bromine) in 28 to 32-day laboratory and field (industrial water supply) tests. Low levels of mortality (<53%) were generated in laboratory studies on exposure to constant doses of total residual chlorine (TRC) when mean test temperatures were <16C. Mortality levels were elevated (>53%) when test specimens were exposed to comparable TRC levels (0.2 to 1.0 mg/L) at temperatures in excess of 18C. Mortalities generated among adults by an initial 14-day low dose (0.25 mg/L TRC) followed by an 18-day high dose (0.50 to 1.00 mg/L TRC; >80% mortality) were comparable to those from a constant high dose (0.50 to 1.00 mg/L; 60 to 95% mortality). Adults and juveniles were comparably sensitive to halogen concentrations adequate for control. There is no substantial difference in the effectiveness of either chlorine or bromine in controlling adult and juvenile stages ofC. fluminea. Field studies conducted in the spring and fall produced markedly dissimilar results. Mortality levels during the spring field study exceeded 90% after 28 days of exposure to 0.25 mg/L TRC, while ambient temperatures rose from 20 to 25C. Mortality levels not exceeding 23% were observed among test organisms after 28 days of exposure to elevated TRC levels (<0.50 mg/L), while ambient temperatures were declining from 20 to 12C during October and November 1985.     

Trimethyltin toxicity to larvalUca pugilator: Effects of temperature and salinity

The toxicity of four trimethyltin concentrations to stage I zoeae of the fiddler crab,Uca pugilator, was tested at temperatures of 10°C, 20°C and 28°C and salinities of 10, 20 and 30. Stepwise multiple regression of the probit of mortality data produced a formula from which productive response surfaces were generated. 24 hr LC 50's in 30 salinity at 10°C was 12 ppm, at 20°C 3.35 ppm and 0.61 ppm at 28°C. Corresponding 48 hr LC 50's were about one-tenth of these values. An increase in temperature and a decrease in salinity sharply increased trimethyltin toxicity in fiddler crab zoeae.Contribution No. 1226, Center for Environmental and Estuarine Studies, University of Maryland     

Temperature-dependent elimination of 2,4,6,2′, 4′-pentachloro[U-14C]biphenyl inNereis virens (Polychaeta)

Four groups of 22 to 24 sandworms,Nereis virens, were maintained in closed aquarium systems with continuous charcoal filtration and 45 L capacity at 20% salinity and 4, 8, 12, and 16°C. The worms of 2.0 to 5.4 g initial wet weight inhabiting glass tubes were given 10 oral doses of 0.3g 2,4,6,2,4-pentachloro[U-¹⁴C]biphenyl (PCB) during 10 consecutive days and were subsequently allowed to eliminate the compound for up to 45 weeks. Consumption and accumulation averaged 80.9, 78.3, 73.5, and 68.4% at the four temperatures. The elimination may be described with an exponential function and was fastest at 12°C. For instance, the times of initial 30% decrease t_e30 were 18.7, 16.8, 5.3, and 8.0 weeks at 4, 8, 12, and 16°C. Forty to 45% of the eliminated PCB were recovered from the feces, and the amounts from the feces confirmed the optimum PCB elimination at 12°C. The elimination optimum at submaximum temperatures suggests that PCB elimination byNereis virens, at least in part, is an active process. By comparison with earlier work, a dependence of the elimination times t_e30 or t_e50 on initial concentration was found thus favoring a multicompartment elimination model. Unequal PCB contents of anterior and posterior worm parts were governed by unequal lipid contents.     

Carbamate insecticide removal in laundering from cotton and polyester fabrics

Even though carbamate insecticides are becoming increasingly important for insect control on field crops, few studies have focused on their removal from contaminated textiles. Hence, this study evaluated the effectiveness of selected laundering procedures in removing carbofuran and methomyl insecticides from 100% cotton and 100% polyester medium weight fabrics. After treating the fabric samples with 4.0% (w/w) aqueous solutions of Furadan^® 4F Insecticide (carbofuran) or Lannate^® L Insecticide (methomyl), they were air dried and laundered, using three detergents [All^® (non-ionic), Tide^® (anionic), and Wisk^® (anionic and non-ionic)] plus water only at two temperatures (warm: 49°C wash/40°C rinse and hot: 60°C wash/49°C rinse). The percentages of insecticide residue remaining on the fabrics after laundering were analyzed by high performance liquid chromatography (HPLC) with a fluorescence detector, and bioassay tests withDrosophilia malanogaster Meigen were used to evaluate their relative toxicity.All of the laundering procedures, including the water only wash, were effective in removing 99% of the carbamate insecticides from both the cotton and polyester fabrics. Among the insecticide/fabric types evaluated, the highest percentages of residue remaining were associated with the polyester fabrics treated with methomyl. After 72 hr, fruit fly mortality occurred on only the methomyl treated polyester laundered in warm water. These findings support those reported in previous studies on the ease with which carbamate contaminants are removed from textiles, compared to other insecticide types.Contribution No. 87-245-J.     

Spontaneous N,N′-dibutylurea (DBU) formation in benlate DF® formulation under elevated temperatures

Thermal degradation of benomyl in the fungicide Benlate DF® at temperatures higher than 55°C leads to the formation of N,N-dibutylurea (DBU). External moisture is not required, since starch, an inert ingredient in the formulation, serves as a source of water. Enhanced phytotoxicity of the heat-treated, DBU-rich Benlate DF® was demonstrated by lettuce seedling bioassay. Temperatures higher than 70°C were recorded in a metal shipping container in June 1995 in Hawaii. Accumulation of DBU was observed in Benlate DF® sealed in ampules and stored in this container. It is concluded that DBU formation is an intrinsic characteristic of Benlate DF® at the temperatures tested. High temperature and high humidity in tropical regions provide ideal conditions for DBU formation in Benlate DF®.     

Effect of temperature and sunlight exposure on the fate of soil-applied [14C]-gamma-hexachlorocyclohexane

The role of temperature and solar radiation in the rapid dissipation of-1,2,3,4,5,6-hexachlorocyclohexane (-HCH) from Indian soils was determined by quantifying volatilization, mineralization, binding and degradation of [¹⁴C]-HCH in a sandy loam soil. An increase in temperature from 15 to 45°C caused a 6-fold rise in volatilization. Degradation as well as mineralization of HCH increased with temperature, although both were minimal. Bound residues of HCH in soil increased from 3.3% at 15°C to 16.7% at 45°C, after 28 days. In flooded soils, volatile losses nearly doubled, while binding and mineralization decreased. Exposure of HCH-treated soil to sunlight in quartz tubes showed a two-fold increase in volatilization over the dark controls. Formation of-2,3,4,5,6-pentachlorocyclohex-l-ene (-PCCH) in the unflooded soils and-3,4,5,6-tetrachlorocyclohex-1-ene (-TCCH) in the flooded systems were enhanced by sunlight. Trace amounts of-HCH were detected in the volatilized organics from the quartz tubes. Flooding the soil markedly increased volatile losses, thus leaving only 14% of the initial HCH as residues in soil after 42 days of exposure in quartz tubes. Neither flooding nor sunlight had any significant effect on HCH binding in soil. Mineralization, though amounting to a maximum of only 3% in the unflooded soil, was further reduced in submerged soils. The data demonstrate the significant influence of temperature, humidity and solar radiation, on the rapid loss of HCH from Indian subtropical soils, evidently by rapid volatilization.     

Effects of triphenyltin on fish early life stages

Using a static-renewal procedure, effects of triphenyltin chloride (TPT) on hatching, survival, and morphology were assessed in early life stages of European minnows Phoxinus phoxinus. Embryonic-larval exposure at 16 and 21°C, and larval exposure at 16°C were compared. In the embryoniclarval exposure at 16°C, hatching was delayed and hatching success decreased at 15.9 g/L. Mortality increased at 3.9 g/L TPT, and complete mortality occurred after 7 and 9 days at 15.9 and 5.1 g/L, respectively. Mortality was higher at 21°C that at 16°C. Triphenyltin was more toxic to fish in larval stages. The induced effects were dose related, mortality increased at 1.8 g/L after 3 days, and was total after 5 days at 10.6 g/L. In all high TPT exposures, larvae developed skeletal malformations (bent tails), showed impaired swimming behavior or paralysis, and eyes became opaque. Marked histopathological alterations were found. Degenerative hydropic vacuolation of the cytoplasm were evident in skeletal muscles, skin, kidneys, corneal epithelium, lens, pigment layer of the retina and choroid, retina, and CNS including spinal cord. In severe cases, nuclear changes including pycnosis and karyorrhexis occurred. The observed toxicity of TPT was similar to that of tributyltin, but TPT acted more selectively on the lens and CNS, whereas other tissues were less affected. The study indicates that Phoxinus phoxinus larvae are negatively affected at peak TPT concentrations found in polluted environments.     

Cardiorespiratory and thermal effects of wearing gas protective clothing

Summary Six healthy men aged 25 to 37 walked on a treadmill at work levels of 21 and 41% of their for 25 to 30 min wearing gas protective clothing (GPC) consisting of an impermeable suit with a self-contained breathing apparatus (total weight 25 kg) or shorts (control tests, CT) in a temperate environment (t _a 24.3°C ± 1.0°C, rh 30–50%). When the GPC was worn at 21 and 41% , the most prominent increases, compared with the CT, were noted in the heart rate ( ± SE, 120 ± 5 vs 76 ± 3 beats min^–1 and 171 ± 5 vs 103 ± 3 beats min^–1), mean skin temperature (36.1 ± 0.2 vs 31.3° C ± 0.1°C and 36.9 ± 0.3 vs 30.9°C ± 0.4°C) and sweat rate (473 ± 51 vs 70 ± 23 g m^–2 h^–1 and 766 ± 81 vs 135 ± 18 g m^–2 h^–1) indicating a high cardiovascular and thermoregulatory strain, which was not decreased by ventilating the suit with an air flow of 281 min^–1 at 41% . The ventilation, oxygen consumption and production of carbon dioxide increased in relation to the extra weight of the GPC, partly dependent on the dynamic work level. It was concluded that the increase in the physiological load caused by the GPC was so high that the work-rest regimens, workers' level of physical fitness, cardiovascular health and heat tolerance should be considered whenever gas protective clothing is used.     

Effect of environmental temperature on naphthalene metabolism by Juvenile Starry flounder (Platichthys stellatus)

Juvenile starry flounder (Platichthys stellatus) maintained at 4° or 12°C were forced-fed³H-1-naphthalene. At 24 hr, after the initiation of exposure, significantly (p < 0.05) higher concentrations (2 to 15 times) of naphthalene were present in tissues of starry flounder at 4°C than those present in fish held at 12°C. The influence of lowering of water temperature on naphthalene retention was even more marked after one week. At this time, muscle and liver of fish at 4°C contained 26 and 34 times, respectively, more naphthalene than did muscle and liver of fish at 12°C. Concentrations of total metabolites, in most tissues were not substantially higher at the lower temperature either 24 or 168 hr after the naphthalene-exposure.Thin-layer Chromatographic separation of the metabolites revealed that at 24 hr, 1,2-dihydro-1,2-dihydroxynaphthalene (dihydrodiol) was the major component in liver (40 to 50% of extracted metabolites) and muscle (-80% of extracted metabolites) regardless of the temperature. Bile contained, primarily, conjugates (e.g., glucuronides), which yielded the dihydrodiol as the principal metabolite on enzymatic hydrolysis. From 24 to 168 hr, the concentrations of each metabolite class did not vary directly with the concentrations of total metabolites. Accordingly, at 168 hr, the ratio of total metabolite concentrations in liver of fish at 4°C compared to 12°C was 1.6, whereas the ratios for the dihydrodiol, sulfate/glucoside conjugates and glucuronide conjugates were 4.5, 0.6 and 3.8 respectively.Generally, lowered water temperature increased tissue concentrations of the parent hydrocarbon and its metabolites. However, the magnitude of the increase was dependent upon the compound, the tissue, and the time after the initiation of the exposure. The results emphasize the importance of determining concentrations of individual metabolites together with parent hydrocarbons in tissues of fish when assessing effects of environmental parameters on xenobiotic toxicity.     

Application of an Enzyme-Linked Immunosorbent Assay for the Analysis of Paraquat in Human-Exposure Samples

Paraquat is a toxic quaternary ammonium compound used as an herbicide around the world. Easy, fast, and inexpensive but sensitive methods are needed to study the effects of long-term, low-level exposure of paraquat on human health. An enzyme-linked immunosorbent assay (ELISA) was used for quantification of paraquat in urine and air-filter samples collected in a human-exposure study among farm workers in Costa Rica. A sample pretreatment consisted of removal of interfering substances using solid-phase extraction resin columns. The precision and accuracy of the method were tested using duplicate spiked urine samples. The correlation between results for blind samples obtained using ELISA and liquid chromatography–mass spectrometry was significant (R²=0.945 and 0.906 for spiked and field samples, respectively). With an LOQ of 2 ng mL^–1, this ELISA method was able to distinguish the exposed from the nonexposed farm workers. For the air-filter analysis, paraquat was extracted by 9M H₂SO₄ at 60°C for 12 hours, and the results obtained by ELISA showed good correlation (R²=0.918) with the spectrophotometric (256 nm) measurements. Paraquat in acid-stabilized urine samples was very stable, and no significant losses were detected during a 3-month storage at room temperature, at 4°C, or at –20°C.     

Nickel uptake and loss in the bivalvesCrassostrea virginica andMytilus edulis

Nickel uptake and loss byCrassostrea virginica andMytilus edulis were studied at naturally occurring seawater temperatures and salinity to determine their potential as indicators of nickel pollution. After 12 wks treatment with 5 and 10 g Ni/kg seawater, mean tissue concentrations inC. virginica were 9.62 ±3.56 and 12.96 ±5.15 g/g dry weight. Mean nickel concentrations inM. edulis treated with 5 and 10 g Ni/kg seawater for 12 wks were 10.40 ±2.66 and 16.43 ±3.19 g/g dry weight, respectively. Significant linear relationships were found between nickel uptake byC. virginica andM. edulis and seawater nickel concentrations over the concentration range. A significant inverse relationship exists between tissue nickel concentration and dry weight in bothC. virginica andM. edulis. After holding nickel-treatedM. edulis in ambient flowing seawater for 28 weeks, a 73 and 89% loss of nickel concentration occurred inM. edulis treated with 5 and 10 g Ni/kg, respectively. When treated similarly,C. virginica from both the 5 and 10 g Ni/kg treatments lost 48 and 68% respectively, of their tissue nickel concentration. The evidence suggests thatM. edulis would be a better indicator of nickel pollution in its environment thanC. virginica.Contribution #341     

Movement and transformation of 1,3-dichloropropene in the soil of flower-bulb fields

The fumigant 1,3-dichloropropene was injected into the soil of three bulb fields in the summer. At various times after injection, the contents of the (Z) and (E) isomers (formerly called thecis andtrans isomers) were measured in the unsaturated and saturated zones down to a 3 m depth. Within a month, the contents decreased to less than 0.2 mg/kg and they only gradually declined further in the subsequent months. Occasionally, very low contents (less than 1 g/kg) of the (Z) and (E) isomers were measured in the groundwater zone.The transformation 1 kinetics of 1,3-dichloropropene in soil material from the root zone was studied in more detail at 15°C in the laboratory. At higher initial contents (62 mg/kg), the rate of transformation was approximately first-order in the first period of about three weeks and this was followed by a rapid transformation. At lower initial contents (12 mg/kg), transformation was rapid from the beginning and only about 1% of the dose was left after two weeks.     

High tolerance of lampreys to Kepone® toxicity

Larval sea lampreys (Petromyzon marinus) were exposed to the organochlorine insecticide Kepone^® in freshwater solution in a continuous flow diluter system at 12 and 20°C. At 12°, the 36-hr LC50, 96-hr LC50, and incipient lethal concentrations were 1,100, 444 and 145 g Kepone/ L, respectively, while at 20°, the 96-hr LC50 was 414 g/L. These are the highest LC50 values for Kepone ever reported for a fish species. Rates at which larval lampreys accumulate and clear Kepone were measured at 12°C. The depuration rate constant (K_d: 0.13–0.46 per day) was the highest ever reported in a fish species, so rapid elimination may contribute to the exceptional ability of lampreys to survive acute Kepone poisoning. The uptake rate constant (K_u) was 450–650 per day, and the bioconcentration factor averaged about 1900. The most likely source of high tolerance of lampreys to Kepone is an ability to withstand high tissue levels: Lampreys survived body burdens of 500–600 g Kepone/g, exceeding all other known vertebrates. Technical difficulties associated with the use of Kepone solutions are discussed, such as precipitation and loss from solution through apparent volatilization.     

A novel technique for the detection of DNA single-strand breaks in human white blood cells and its combination with the unscheduled DNA synthesis assay

Summary A modified assay for the detection of DNA single-strand breaks (SSBs) in human mononucleated white blood cells (MWBCs) based on the nick translation (NT) reaction was developed and combined with the test for unscheduled DNA synthesis (UDS). Both assays were performed on disposable 96-well filtration plates and therefore allowed rapid and sensitive examination of SSBs and UDS. Only 5–8 ml of heparinized blood is required for an eightfold determination in both assays. The uptake of radioactive nucleotide precursors was demonstrated to depend linearly upon the NT reaction time and in both assay systems on the number of investigated cells. The best results and the lowest signal to noise ratio were obtained when the NT assay was performed at 25°C for 20 min. The test was standardized for 150000MWBCs/well and a polymerase I concentration of 20 U/ml. The same number of cells were used to measure UDS during a 4-h incubation at 37°C. We observed a dose-dependent increase in SSBs after in vitro incubation with N-methyl-N-nitrosoguanidine (MNNG), with a detection limit of 50 M when MNNG was present for 1 h and of 5M after 20-h incubation period. UDS in MWBCs was increased after treatment for 1 h with MNNG (200 M) only if poly(ADP)ribose synthesis was inhibited by 3-aminobenzamide. UDS was induced by 320 M methyl methanesulfonate, but SSBs could only be detected after inhibition of UDS by 100 M hydroxyurea. The described modification of the NT procedure for the detection of SSBs in DNA of human MWBCs and its combination with the detection of UDS could serve as a useful tool for biological monitoring in occupational or environmental medicine.This work is part of a thesis by T. Krause for a medical doctorate     

Thermal and Biocidal (Chlorine) Effects on Select Freshwater Plankton

Impact of select levels of temperature, individually and in combination, with different initial chlorine concentrations on the growth and reproduction of phytoplankter Chlorella vulgaris and zooplankton C. reticulata, C. viridis, and Diaptomus forbesi was evaluated. During the experiment, optimum growth temperature for the alga was estimated as 26°C, even though alga showed considerable growth up to 36°C. However, initial chlorine at concentrations ≥0.25 mg l⁻¹ adversely affected growth (P < 0.05 to 0.001) at all select temperature levels (26°C, 31°C, 33°C, 36°C, 39°C, 42°C, and 45°C). Investigations toward effects of different temperatures (26°C, 31°C, 33°C, and 36°C) on zooplankton indicated that survivability of these organisms was affected at temperatures ≥33°C. However, the percent growth rates of zooplankters at 26°C were significantly higher (P < 0.05) than those at 31°C, 33°C, and 36°C. Initial chlorine levels of 0.5 and 0.25 mg l⁻¹ were lethal to zooplankton; however, zooplankton survival was not affected at 0.06 mg l⁻¹ chlorinated water at all selected temperatures.     

Identification of cis- and trans-verbenol in human urine after occupational exposure to terpenes

Summary Urine from sawmill workers exposed to -pinene, -pinene and -3-carene was collected and hydrolyzed with -glucuronidase at pH 5.0 for 24h at 37°C. After hydrolysis the urine was cleaned on a SEP-PAK C₁₈ cartridge. The cartridge was eluted with n-heptane. The eluate was injected onto a gas chromatograph equipped with a 25-m (0.32-mm ID) SP-1000 capillary column. The major peak in the chromatogram was identified by GC-MS as trans-verbenol by electron impact at 70 eV. cis-Verbenol was also identified. These metabolites could not be detected in non-hydrolyzed urine from the exposed workers or in hydrolyzed urine from an unexposed individual. The recoveries of the verbenols from hydrolyzed urine were in the range of 85 to 94% and the metabolites were stable both in urine and in n-heptane after sample cleaning at –20°C for at least 12 weeks. We suggest that these metabolites are formed from -pinene by hydroxylation.     

Uptake and depuration of petroleum hydrocarbons by crayfish

No differences were noted in the amount of naphthalene uptake (approximately 125g) by individual crayfish exposed for 1, 2, or 4 hr at 25°C in open, non-aerated glass jars containing¹⁴C-naphthalene-5% of a water-soluble fraction (WSF) of No. 2 fuel oil. The cephalothorax, containing the hepatopancreas (a food absorption organ), showed greater uptake of naphthalene than the tail flesh or tail skeleton of individual crayfish exposed to the oil for 3 hr at 25°C. Crayfish exposed to the oil for 1, 2, or 4 hr and then placed in open, non-aerated containers of oil-free water lost most of the carbon-14 activity during the first 24 hr, with smaller losses occurring at 24 hr intervals up to and including 96 hr. Carbon-14 naphthalene in a 5% WSF of No. 2 fuel oil held in 12 open, non-aerated, oil-free, glass jars for 1, 2, 3, 4, and 5 hr at 25°C showed little volatilization (P > 0.4).     

Acute toxicities of selected heavy metals to the softshell clam,Mya arenaria

Summary Static acute toxicity bioassays with adult softshell clams and salts of copper, cadmium, zinc, lead, manganese, and nickel were conducted at 30 salinity and 22°C. Concentrations fatal to 50% in 168 hours, in mg/ (ppm) metal added at start, were 0.035 for Cu, 0.150 for Cd, 1.55 for Zn, 8.80 for Pb, 300.0 for Mn, and >50.0 for Ni. Additional tests were conducted with Zn²⁺ and Cu²⁺ at 30 during fall (17.5°C) and winter (4°C); clams displayed increasing survival with decreasing temperature. For Cu, LC-50 (336 hr) values at 17°C and 4°C were 0.086 and >3.00 mg/, respectively; for Zn these were 2.65 and >25.0, respectively.