Hazardous halogenated substances formed during combustion processes

The results of the emissions from combustion processes and/or from fire accidents show the risk to man and his environment and thus the need for strict legislation and critical analysis of unwanted compounds. These substances or their thermolysis products are often due to incomplete combustion or may result from the interaction of various substances.

In the following we report the formation of octachlorostyrene (OCS) and of high‐toxic substances such as polybrominated dioxins (PBrDD's), dibenzofurans (PBrDF's) by the combustion.

In order to determine a possible source of the non‐manufactured compound OCS, we conducted several model experiments in a combustion chamber at various temperatures from 400 °C to 800 °C. The thermolysis of chlorinated solvents like chloroform or of chlorinated aromatice like pentachlorobenzene produced—among other chlorinated substances—OCS as one of the major products.

Analogous combustion experiments with polyester plastics containing decabromodiphenylether as flame retardant and antimony trioxide as Synergist led to PBrDD's and PBrDF's. Here antimony trioxide seems to play an important role because in absence of this oxide, PBrDD's and PBrDF's were not found in our experimental conditions.     

Occupational exposure to airborne aromatic amines in rubber manufacturing: Determination by gas chromatography‐mass spectrometry

Aromatic amines (AAs) are used in a variety of chemical industries and consequently they are the object of great attention in occupational hygiene owing to the carcinogenic effects that many of them have shown. This work outlines a procedure for the determination of occupational exposure to airborne AAs in the rubber industry and the application of this method in a tyre manufacturing plant using p‐phenylenediamines as antiozonants. Samples were collected on a glass fibre filter followed by a silica gel tube and analyzed by GC‐MS/SIM using a capillary column coated with methyl silicone. p‐Phenylendiamines and other AAs probably formed as thermodegradation products were found in concentrations of up to 10 μg/m³ during rubber vulcanization.     

Polarographic investigations on the complexation of cadmium and zinc by thiol peptides

Complex formation of Cd²⁺ and Zn²⁺ with thiol derivatives has been investigated by differential pulse polarography. The binding of Cd²⁺ and Zn²⁺ with cysteine (CySH), glutathione (GSH) and the model peptide N‐acetyl‐cysteine‐methylamide (ASH) reveals different stoichiometry. Thus, Cd²⁺ forms 1:1 and 1:2 complexes with CySH while 1:2 and 1:4 complexes have been observed with GSH and ASH, respectively. Overall formation constants of Cd²⁺ with CySH (Iogβ ₂ 15.3) and with GSH (Iogβ5₂ 14.4) have been estimated using competitive complexation with nitrilotriacetic acid (NTA). Investigation of competition between Zn²⁺ and Cd²⁺ for the thiol complexation has underlined the role played by the amino group in CySH for the stabilization of Zn complexes in contrary to Cd complexes.     

Statistical interpolation model for the description of ground pollution due to the TCDD produced in the 1976 chemical accident at seveso in the heavily contaminated zone “A”;

The influence of NTA on chromium genetic activity was studied in the D7 strain of Saccharomyces cerevisiae. At low dose (subgenotoxic) of sodium chromate (CrVI) (5mM), NTA increased the point mutation while at higher dose (25 mM) of chromate in the presence of NTA a decrease of point reverse mutation was observed. Probably NTA affected either the uptake of Cr(VI) favouring the intracellular reduction to Cr(III), or the recombinational repair of DNA breaks induced by chromate oxiding activity.

An increase of point (reverse) mutation was obtained in the experiments with NTA and chromium chloride, suggesting the hypothesis that NTA might interact with Cr(III) forming NTA‐Cr(III) complexes able to permeate cellular membranes and bind to DNA. In addition NTA genetic inactivity was confirmed.     

Effects of the level of dietary protein on the toxicity of hexachlorocyclohexane in rats

Male albino rats were fed for 28 days from weaning on diets containing 5% (group 1), 10% (group 2) and 21% (group 3, normal protein) protein as casein. At the end of dietary period, HCH was administered daily for 30 days to investigate the interaction between protein deficiency and pesticide toxicity. The results indicated that rats fed a lower protein diet and HCH had a higher mortality, lower rate of growth, increased liver weight and deposition of the pesticide in blood and tissues in larger amounts. Blood pressure (systolic and diastolic) was significantly increased and the heart rate showed tachycardia in low protein exposed animals. A significant increase of total lipids, cholesterol, triglycirides, free fatty acids in serum and tissues of animals exposed to low protein was observed. A close correlation existed between lipid accumulation and storage of HCH in tissues and dietary protein seemed to play an important role in detoxification.     

Synthesis of 2,5‐diaryl‐2,4‐pentadienenitriles and their spectral,fluorescence and mutagenic properties

The condensation of substituted cinnamaldehydes and arylacetonitriles using sodium ethoxide in ethanol at room temperature afforded 2,5‐diaryl‐2,4‐pentadienenitriles in good yield. The structure of the reaction products was established on the basis of their infrared, nuclear magnetic resonance and elemental analysis data. Two representative compounds were studied for their mutagenic activity. One of them showed a weak mutagenicity while the second showed a high mutagenic activity in TA97a Salmonella strain. Both were negative in TA100. Some of these pentadienenitriles showed fluorescence in solutions.     

Hydrolysis of a model surfactant as measured using ACYL coenzyme a synthetase

Hydrolysis of a model nonionic surfactant, [1‐¹⁴C]methyl palmitate, was compared between porcine esterase and lipase using a new hydrolase assay. The assay incorporates acyl coenzyme A (CoA) synthetase to convert the hydrolytic product of methyl palmitate, palmitic acid, to its acyl CoA derivative; palmitoyl CoA is separated from unreacted substrate for quantitation by a highly efficient extraction. The assay achieves quantitative separation between product and substrate due to the high water solubility of the acyl CoA derivative, eliminating the need for time‐consuming chromatographic separations. After 60 min under optimal conditions, only 20 U/mL porcine hepatic esterase hydrolyzed 93.6+0.9% of 20μM methyl palmitate, while 100U/mL porcine pancreatic lipase was required to hydrolyze only 82.3 ±0.7% of the same substrate. While both enzymes detoxified the surfactant, esterase was more efficient, possibly indicating preferential specificity for simple monoesters; generally selective for endogenous triacylglycerols, lipase may be less specific for surfactants. However, together both enzymes may enable mammals to hydrolyze ingested nonionic surfactants from oil spill dispersants, reducing their toxicity.     

Ground water pollution by pesticides at the watershed‐soil catena scale: Lindane at the lower Colorado river basin (Argentina)

The movement of Lindane from application points at the surface soil towards the underground water and further transport within this compartment at the watershed‐soil catena scale, was inspected by measurements of the pesticide concentration in soil water at a controlled experiment where it was applied at a usual label dose. The concentrations of Lindane in soil water and the upper phreatic level were also measured at successive dates in samples obtained from a net of phreatimeter probes distributed over the area (1,500 km²) of the lower Colorado River basin (Bs. Aires, Argentina). The location of cultivated‐irrigated areas within the watershed was inferred from NDVI (Normalized Difference Vegetation Index)‐1 km‐10 day AVHRR images obtained at successive dates during the irrigation season. Feasible paths of underground gravitational water flows were computed by means of a GIS‐simulation model on the basis of local terrain slopes and aspects. The pattern of Lindane distribution over the basin was explained on the basis of the distribution of diffuse sources, the patterns of percolation and groundwater flows and the thermodynamic characteristics of the pesticide.     

Removal of pesticides from water samples by adsorption with fatty acids supported on barium sulphate

Oleic or linoleic acid supported on barium sulphate was used to remove atrazine and terbuthylazine in the range of 0.1–2.0 μg/L using spiked water samples. The sorption of atrazine depends on the stirring time and the best value is 150 min. Terbuthylazine is removed well with a stirring time of 60 min and its adsorption is about 90%. Detection of the residual pesticide in treated waters, after solid phase extraction (SPE), was carried out by GC‐MS operating in selected ion monitoring (SIM) using a calibration curve by direct injection of standard solutions of herbicide.     

Air pollution protection by waste amorphous SiO2 utilization in Portland cement production

This papers deals with waste amorphous silica obtained from AlF₃ production. This is a waste material that could be used as additive in cement production. Results are encouraging although there are no large quantities of this material available (about 4000 t/yr). Experiments were performed with the addition of 2.5%, 5.0%, 7.5% and 10.0% mass of amorphous silica obtained from AlF₃ production. Flexural and compressive strengths of the prepared mortar samples with w/c = 0.50 and with the constant flow were determined. Experiments show that optimal quantity for the amorphous silica addition is 5% of the cement mass.