A. di Domenico

An overview of TCDD half-life in mammals and its correlation to body weight.

Major determinants of TCDD half-life in organisms are lipophilicity, metabolism, and hepatic binding sites. In addition, half-life seems to be empirically correlated to organism body weight. In this paper, this correlation is evaluated by a regression analysis of half-life measures and body weight data selected from the literature. Single exposure studies on laboratory mammals and human half-life data were specifically taken in consideration. The analysis outcome appears to be highly significant probably owing to the stability and generally slow metabolism of the substance in the organisms considered. The effect on half-life of factors other than body weight does not seem to influence significantly data dispersion around the regression line. The potential effects of a dose-dependent excretion cannot be excluded as toxicokinetic studies have been usually carried out at high exposure doses.

The influence of soil particle adsorption on 2,3,7,8-tetrachlorodibenzo-p-dioxin biological uptake in the rabbit.

A comparative study on the biological uptake in the rabbit of 2,3,7,8-tetrachloridibenzo-p-dioxin (TCDD) in different formulations, including accident-contaminated Seveso soil, was attempted. On the whole, these results indicated that soil-borne TCDD had a bioavailability lower than that of free (solvent-borne) TCDD.

ENVIRONMENTAL PERSISTENCE OF 2,3,7,8-TCDD AT SEVESO

TCDD levels were determined at 44 soil sites in Zone A during three surveys carried out at different times (1, 5, and 17 months) after the ICMESA accident. The data obtained provide statistically significant (P<.01) evidence that the geometric mean of TCDD levels in the unworked soil of Zone A diminished sharply in the first six months after the accident. Following this period, no further decreases in TCDD levels were detected. Available data are consistent with the hypothesis that TCDD presence in the Seveso environment diminished with time and at a rate which also decreased with time until it eventually became ~0 (steady state). Experimental data have been fitted to two mathematical functions complying with such observations. From the steady-state function the mean TCDD levels at t=0 may be estimated to have been from 5 to 11 times as high as steady-state values.

A two-exponential model to describe the vanishing trend of 2,3,7,8-tetrachlorodibenzodioxin (TCDD) in the soil at Seveso, northern Italy.

Abstract A linear combination of two exponentials associated with fast- and slow-vanishing dynamics is used to describe TCDD persistence pattern in the soil at Seveso. Slow dynamics (long-term coordinates; t ⪢ 1.50 y) were considered in an earlier investigation. This paper considers the pre-requisites for fitting the fast exponential term. In the absence of enough direct experimental data, a four-data set (short-term coordinates; t ≤ 1.50 y) was made up from mathematical calculations. The amount of TCDD in Sevesos most contaminated area (Zone A) is tentatively estimated to be ≥ 34 kg (from regression equation lower edge); TCDD fast dynamics half-life is shown to be 23 days (mean value).

PCDD, PCDF, and PCB contamination of air and inhalable particulate in Rome

SummaryThe isomer specific determination of PCDD, PCDF and PCB was carried out on samples of air and inhalable particulate from Rome. Samples were taken daily for six months and pooled to yield two samples per month. Normal PCDD+PCDF concentrations expressed in TEQ ranged from 48 to 87 fg/m3, while total PCB ranged from 0.1 to 1.4 ng/m3. The 2, 3, 7, 8-substituted PCDD and PCDF congener pattern is shown together with the PCB congener pattern.

Ecotoxicological profile of xylenes. Working party on ecotoxicological profiles of chemicals

The xylenes (o, m, p), which are produced in large amounts and widely used, must be considered as environmental contaminants, as they have been identified in the atmosphere of many countries. Their acute and chronic toxicity in mammals is moderate. Mutagenic and teratogenic properties can be excluded. Carcinogenic potential has been at present inadequately studied. In man some disturbances are evident at the concentration of 45 ppm. Hepatic metabolism is a valid process of detoxification and its high rate limits the risk of accumulation of the xylenes in adipose tissue. Ecotoxicological data refer almost exclusively to water. No long-term tests have been made. However, the high volatility, elevated elimination, and the low factor of accumulation suggest the impact on aquatic environment should be limited. Xylenes are easily biodegraded by many microorganisms. Photoxydation is one of the main degradation processes, responsible for the disappearance of the xylenes from the atmosphere.

Chemiobiokinetic study in freshwater fish exposed to lindane: Uptake and excretion phase rate constants and bioconcentration factors

Four species of freshwater fish (Brachidanio rerio, Poecilia reticulata, Salmo gairdneri, Lepomis macrochirus) were exposed to lindane (2–6 μg 1‐1) in a flow‐through system to investigate chemical bioconcentration kinetics. Lindane concentration was assayed in fish fat and water matrices at different exposure and excretion times. For all species, it was observed that a concentration plateau in fish was already reached after a 60 h exposure, whereas > 90% of lindane apeared to have been excreted after a 160 h excretion period. Bioconcentration and its kinetics did not appear to be significantly species‐dependent. Bioconcentration factors were in the range of 300–730 in fish and from 20 to 50 times as high in fat.

Analytical procedures to detect 2,3,7,8-TCDD at Seveso after the industrial accident of July 10, 1976

The analytical procedures used at Seveso (Milan, Italy) for the determination of 2,3,7,8-TCDD, and some isomers, in biological and environmental samples are reviewed in this paper. During the emergency period, up until the first 10 days of August, the extracts, mostly from soil or vegetation samples, were evaporated to dryness and then mixed with less than or equal to 10-ml solvent. Of these solutions, aliquots up to 10 microliter were injected into a low-resolution gas chromatograph (GC) combined with a low-resolution mass spectrometer (MS). Analytical sensitivity for vegetation and soil was less than 10 ppb and approximately 100 ppt, respectively--sufficient for the early mapping of the most heavily contaminated territory. After the emergency period, the greatest improvement in environmental sample analysis was the introduction of cleanup procedure which greatly reduced the presence of unwanted material in samples. Cleanup was followed by the complete removal of the solvent. Dry samples could be taken up with rather small volumes (greater than or equal to 0.1 ml) of solvent, of which an aliquot was used for GC-MS analysis. The instrumental setup was kept as above. For animal samples, extraction entailed preliminary alkaline digestion followed by a number of cleanup steps. The final dry sample was taken to desired volume by adding solvent (greater than or equal to 0.1 ml), of which a few microliters were injected in GC-MS apparatuses. Detection thresholds improved markedly and were less than 10 ppt for agricultural soil and sediment, less than or equal to 0.05 ppt for water, in the range of 60 to 200 ppt for air dust, less than 10 ng/m2 and 10 ppt for wipe and scrape tests, respectively, less than 50 ppt for vegetation, and 250 ppt for biological substrata. Major later improvements in TCDD assay were the use of high-resolution gas chromatography (hrGC-MS), in some cases combined with high-resolution mass spectrometry (hrGC-hrMS). This provided greater specificity, sometimes accompanied by a very marked increase in detection sensitivity.

Structure-dependent photocatalytic degradation of polychlorobiphenyls in a TiO2 aqueous system

Abstract Three positional isomers for each polychlorobiphenyl (PCB) homologous group tetra-, penta-, and hexachlorosubsubstituted were irradiated in a TiO 2 (anatase) semiconductor aqueous suspension. Parent PCB disappearance was studied as a function of irradiation time, and a correlation between isomer substitution pattern and the photodegradative behavior was shown. In each group, the slowest disappearance trend was exhibited by the isomer with unsubstituted ortho positions, thereby capable of adapting into a planar structural configuration with minimum (estimated) energy requirement. In general, photodegradation rate increased with increasing degree of ortho chlorosubstitution.

Environmental Photochemistry of Chlorinated Aromatics in Aqueous Media. A Review of Data

A review of data relative to the photochemistry in aqueous media of chlorinated benzenes (PCBzs), phenols (PCPs), naphthalenes (PCNs), dibenzofurans (PCDFs), and dibenzo-p-dioxins (PCDDs) is presented. Analysis of data is focussed on direct, sensitized, and catalysis-assisted photoprocesses occurring under environmentally relevant conditions. The purpose of the review is to provide a basis for preliminary assessment of potential effectiveness of sunlight photochemistry as detoxication mechanism in natural water bodies for the above chlorinated aromatics which, due to their potential high exposure and toxic effects (see Appendix), are among those pollutants which have priority for hazard assessment.