Effects of restraint and animal interaction on carbon monoxide lethality: stress and the role of corticosterone

Stress is known to alter physiological homeostasis and distort experimental results. In particular, stress associated with restraint and group‐interaction may modify the lethality of toxic substances. Median lethal concentrations (LC₅₀) for carbon monoxide (CO) were determined using restrained or unrestrained mice exposed for 30 min as groups or individuals. To evaluate stress levels, the serum concentration of corticosterone (COS) was determined for each exposure configuration by radioimmunoassay. Additional LC₅₀ values for CO were determined after treating groups of restrained mice with mifepristone (10 mg/kg), to block the effects of COS, and groups of unrestrained mice with exogenous COS (2 mg/kg), to elevated the serum level. The LC₅₀ value obtained using restrained mice exposed in groups (0.26%) was significantly lower (p<0.05) than the values derived from all other exposure configurations (0.41–0.58%). The higher LC₅₀ values did not differ significantly, although the highest values were obtained from individual exposures. Levels of COS were strongly correlated with CO toxicity (r=0.90). The LC₅₀ obtained from mifepristone‐treated mice (0.41%) was significantly higher (p<0.05) than that obtained from restrained groups of untreated mice (0.26%). However, treatment with COS did not alter the LC₅₀ obtained from unrestrained groups of mice (0.41%). The results suggest that restraint and interaction must be coupled to significantly modify estimates of toxicity, and that effective interaction between restrained mice can occur (probably mediated by olfactory cues). Both factors appear to elevate stress levels in mice, and stress appears to increase the sensitivity of mice to intoxication by CO. However, COS may not be entirely responsible for the effects of stressors on toxicity. Copyright © 2000 John Wiley & Sons Ltd     

Combustion products of polymeric materials. IV—testing of toxicity hazard

A method based on exposure of mice in the CAB 4.5 smoke chamber for the evaluation of the biological toxicity of the products of flame and smoldering combustion of polumeric materials has been developed. A toxicity index, characterizing the danger from the products of combustion of the test polymer under the given conditions, was proposed on the basis of values of the concentration of carboxyhaemoglobin in the blood of the test animals, attaining charateristic critical limits (lethal limit) and LC₅₀ values.     

Biological effects of solvent extraction chemicals on aquatic organisms

Aquatic environments are the main recipient for chemicals lost from solvent extraction plants. Therefore, the toxicity of these chemicals to aquatic organisms must be considered. So far the effects of solvent extraction chemicals on aquatic organisms have been underestimated. The toxicity of some commonly employed solvent extraction chemicals to a green alga, Chlorella emersonii, a fish, Salmo gairdneri, and two cellulose-degrading bacteria, Cellulomonas sp. and Sporocytophaga myxococcoides, are reported. For most aliphatic amines studied (Primene JM-T, Amberlite LA-1, Adogen 283, Alamine 336 and Aliquat 336) inhibition of growth (algae and bacteria) and mortality of fish are shown at nominal concentrations below 1 mg dm^?3 (EC₅₀^s and LC₅₀^s). Other chemicals tested (Adogen 383, TBP, HDEHP, NA SUL AS-50, LIX 64N, Versatic 10 and 2-ethylhexanol) are less toxic, having EC₅₀^s for inhibition of growth and/or LC₅₀^s between 0.3 and 100 mg dm^?3. The acute toxicity to fish is shown to be dependent on ambient temperature for all chemicals studied. Solvent extraction chemicals spread into the environment have the potential to produce toxic effects on aquatic organisms. It is therefore recommended that the status of aquatic life in natural waters receiving solvent extraction chemicals is monitored.     

Toxicity of the pyrolysis and combustion products of poly(vinyl chlorides): A literature assessment

Poly(vinyl chlorides) (PVC) constitute a major class of synthetic plastics, Many surveys of the voluminous literature have been performed. This report reviews the literature published in English from 1969 through 1984 and endeavors to be more interpretive than comprehensive. PVC compounds, in general, are among the more fire resistant common organic polymers, natural or synthetic. The major products of thermal decomposition include hydrogen chloride, benzene and unsaturated hydrocarbons. In the presence of oxygen, carbon monoxide, carbon dioxide and water are included among the common combustion products. The main toxic products from PVC fires are hydrogen chloride (a sensory and pulmonary irritant) and carbon monoxide (an asphyxiant). The LC₅₀ value calculated for a series of natural and synthetic materials thermally decomposed according to the NBS toxicity test method ranged from 0.045 to 57 mg l^?1 in the flaming mode and from 0.045 to > 40 mg l^?1 in the non-flaming mode. The LC₅₀ results for a PVC resin decomposed under the same conditions were 17 mg l^?1 in the flaming mode and 20 mg l^?1 in the non-flaming mode. These results indicate that PVC decomposition products are not extremely toxic when compared with those from other common building materials. When the combustion toxicity (based on their HCI content) of PVC materials in compared with pure HCI experiments, it appears that much of the post-exposure toxicity can be explained by the HCI that is generated.     

Recent developments in understanding the toxicity of PTFE thermal decomposition products

Fluropolymers, especially polytetrafluoroethylene (PTFE), have good fire-resistance properties, but their application is limited by concerns over the toxicity of their thermal decomposition products. In experiments using a tube furnace system similar to the DIN 53 436 method, the 30-minute (+ 14 days observation) LC₅₀ in mass loss terms was found to be 2.9 mgI^?1 (Standard Error 0.40) under non-flaming conditions, approximately ten times as toxic as wood and most other materials. Toxicity was due to upper respiratory tract and airway irritation, and was consistent with the known effects of carbonyl fluoride and hydrogen fluoride. When decomposed in the NBS cup furnace test under-non-flaming conditions, PTFE evolved extreme-toxicity products with an LC₅₀ of approximately 0.05 mgI^?1 (mass loss), approximately 1000 times as toxic as wood and most other materials. Toxicity was due to deep lung irritation and oedema. Investigations of the range of conditions under which the extreme toxicity of PTFE products occurs in both small-scale (200-litre) and intermediate-scale (6 m³) experiments have shown that the highest toxicity occurs when PTFE is decomposed under non-flaming conditions over a temperature range of 400–650°C, and when the primary decomposition products are subjected to continuous secondary heating. At higher or lower temperatures, when the sample is flaming, when decomposition products from wood are also present in the chamber, when secondary heating is curtailed, or when the molecule contains hydrogen as well as fluorine, the toxicity of the products is greatly reduced, tending towards the region of ten times the potency of most other materials. Extreme toxicity is associated with a particulate, but the particulate atmosphere is not always extremely toxic, the potency decreasing as the fumes age.     

A literature review of the chemical nature and toxicity of the decomposition products of polyethylenes

The literature on polyethylenes has been reviewed with an emphasis on the identification of gaseous products generated under various thermal decomposition conditions and the toxicity of those products. This review is limited to publications in English through 1984. The analytical chemical studies of the thermal decomposition products generated under vacuum, inert and oxidative experimental conditions are described. In oxidative atmosphere, which most closely simulate real fire conditions, carbon monoxide (CO) was found to be the predominant toxicant. Acrolein was another toxicant often noted in these reviewed studies. More acrolein was generated under non-flaming than under flaming conditions. Results from seven different test procedures were considered in assessing the acute inhalation toxicity of combustion products from various polyethylene formulations. The combustion products generated from the polyethylenes studied in the non-flaming mode appeared to be slightly more toxic than those produced in the flaming mode. In the non-flaming mode the LC₅₀ values ranged from 5 to 75 mg l^?1. In the flaming mode the LC₅₀ values ranged from 31 to 51 mg l^?1. The toxicity of the degradation products of polyethylenes appears to be similar to that found for other common materials designed for the same end uses.     

Analysis and interpretation of the plumbing materials file of the NYS combustion toxicity data bank

New York State's Building and Fire Prevention Code includes a requirement that combustible materials used in electrical, plumbing and finishing systems be tested by the University of Pittsburgh protocol and that particular data from that testing be reported on standard forms to the Office of Fire Prevention and Control. The plumbing file in this data bank contains data on 41 products, excluding minor usages. In this paper, these data plus the data on Douglas fir are reported and analyzed. LC₅₀ was found to have significant correlations with indices of thermal instability, of rate of mass loss, and of corrosive irritants. The most parsimonious model developed with stepwise regression correlated LC₅₀ with three factors: %wt loss per degree of temperature rise, temperature at the beginning of rapid weight loss-temperature at which 1% of the sample weight was lost, and temperature at the end of rapid weight loss-temperature at which 1% of the sample weight was lost. LC₅₀ was weakly correlated with maximum CO concentration and in the ‘wrong’ direction (high CO concentrations were associated with low toxicity). Log LC₅₀ was significantly correlated with Log CO_max, but also in the ‘wrong’ direction. LC₅₀ was correlated with minimum oxygen concentration with a small R-squared and also in the ‘wrong’ direction. The question of the relevance of these test results to smoke exposures in real fires is discussed.     

Insecticidal effect of essential oils from mediterranean plants uponAcanthoscelides Obtectus Say (Coleoptera,Bruchidae), a pest of kidney bean (Phaseolus vulgaris L.)

The bioactivity of 22 essential oils from aromatic and medicinal plants was tested uponAcanthoscelides obtectus Say (Coleoptera, Bruchidae), a pest of kidney bean (Phaseolus vulgaris L.). The insecticidal effect was evaluated by determination of 24- and 48-hr LC₅₀ and LC₅₀ (from 1.50 mg/ dm³ to more than 1000 mg/dm³). Isoprenoids and phenylpropanoids were identified by gas chromatography. The most efficient essential oils were extracted from plants belonging to Labiatae.Origanum marjorana andThymus serpyllum essential oils were the most toxic.     

Watercress and amphipods Potential chemical defense in a spring stream macrophyte

We investigated the potential role of defensive chemicals in the avoidance of watercress (Nasturtium officinale) by the cooccurring amphipod,Gammarus pseudolimnaeus at two spring brooks: Carp Creek, Michigan and Squabble Brook, Connecticut. We conducted observations and laboratory experiments on the consumption of watercress, the toxicity of damaged (frozen) watercress, and the toxicity of damage-released secondary chemicals. Field-collected yellowed watercress typically lacked the bite and odor characteristic of green watercress and was consumed byG. pseudolimnaeus. G. pseudolimnaeus strongly preferred yellowed watercress to green watercress despite the higher nitrogen content of the latter (2.7 vs 5.4%), and usually consumed five times more yellowed watercress (>50% of yellowed leaf area vs. <8% of green leaf area presented). Fresh green watercress contained seven times more phenylethyl glucosinolate than yellowed watercress (8.9 mg/g wet vs. 1.2 mg/g). Cell-damaged (frozen) watercress was toxic toG. pseudolimnaeus (48-hr LC₅₀s: ca. 1 g wet/liter), and the primary volatile secondary chemicals released by damage were highly toxic. The predominant glucosinolate hydrolysis product, 2-phenylethyl isothiocyanate had 48-hr LC₅₀s between 0.96 and 3.62 mg/liter, whereas 3-phenylpropionitrile was less toxic, with 48-hr LC₅₀s between 130 and 211 mg/liter. These results suggest that live watercress is chemically defended against consumption. The glucosinolate-myrosinase system, recognized as the principle deterrent system of terrestrial crucifers, is also possessed byN. officinale and may contribute to defense from herbivory by aquatic crustaceans. This system may be just one of many examples of the use of defensive chemicals by stream and lake macrophytes.     

Fumigant and Contact Toxicities of Monoterpenes to <Emphasis Type="Italic">Sitophilus oryzae</Emphasis> (L.) and <Emphasis Type="Italic">Tribolium castaneum</Emphasis> (Herbst) and their Inhibitory Effects on Acetylcholinesterase Activity

A comparative study was conducted to assess the contact and fumigant toxicities of eleven monoterpenes on two important stored products insects—, Sitophilus oryzae, the rice weevil, and Tribolium castaneum, the rust red flour beetle. The monoterpenes included: camphene, (+)-camphor, (−)-carvone, 1-8-cineole, cuminaldehyde, (l)-fenchone, geraniol, (−)-limonene, (−)-linalool, (−)-menthol, and myrcene. The inhibitory effect of these compounds on acetylcholinesterase (AChE) activity also was examined to explore their possible mode(s) of toxic action. Although most of the compounds were toxic to S. oryzae and T. castaneum, their toxicity varied with insect species and with the bioassay test. In contact toxicity assays, (−)-carvone, geraniol, and cuminaldehyde showed the highest toxicity against S. oryzae with LC₅₀ values of 28.17, 28.76, and 42.08 μg/cm², respectively. (−)-Carvone (LC₅₀ = 19.80 μg/cm²) was the most effective compound against T. castaneum, followed by cuminaldehyde (LC₅₀ = 32.59 μg/cm²). In contrast, camphene, (+)-camphor, 1-8-cineole, and myrcene had weak activity against both insects (i.e., LC₅₀ values above 500 μg/cm²). In fumigant toxicity assays, 1-8-cineole was the most effective against S. oryzae and T. castaneum (LC₅₀ = 14.19 and 17.16 mg/l, respectively). Structure-toxicity investigations revealed that (−)-carvone—, a ketone—, had the highest contact toxicity against the both insects. 1-8-Cineole—, an ether—, was the most potent fumigant against both insects. In vitro inhibition studies of AChE from adults of S. oryzae showed that cuminaldehyde most effectively inhibited enzyme activity at the two tested concentrations (0.01 and 0.05 M) followed by 1-8-cineole, (−)-limonene, and (l)-fenchone. 1-8-Cineole was the most potent inhibitor of AChE activity from T. castaneum larvae followed by (−)-carvone and (−)-limonene. The results of the present study indicate that (−)-carvone, 1,8-cineole, cuminaldehyde, (l)-fenchone, and (−)-limonene could be effective biocontrol agents against S. oryzae and T. castaneum.     

Fire safety improvements in the combustion toxicity area: is there a role for LC50 tests?

It is a well‐known fact that the bulk of fire fatalities can be attributed to the inhalation of toxic combustion gases. This single fact has led regulators in Europe, the US, and other industrialized countries to consider (and in some cases to adopt) requirements for testing of products with various tests for toxic potency, commonly expressed as LC₅₀. The regulators have more recently been joined by the International Organization for Standardization (ISO), which has been developing standards for LC₅₀ and related variables. All of the standards considered so far have been limited to using only bench‐scale test results. Engineers, however, have known for quite some time that the actual toxic effect from combustion gases must be viewed as a product of two factors: (a) the product's real‐scale mass loss rate; and (b) its real‐scale LC₅₀. Thus, two issues can be seen to arise: (1) are real‐scale values of LC₅₀ adequately similar to the bench‐scale ones; and (2) is the range of mass loss rates exhibited by various products small enough so that differences could be ignored and products ranked/rated solely by their LC₅₀ values? This paper examines these questions by the use of a database of experimental results covering a wide range of building products. The analysis shows that far from being the dominant factor in the fire toxicity picture, LC₅₀ is a minor constituent. For real products, LC₅₀ values simply do not vary much. Mass loss rates, however, vary tremendously. Thus, it is demonstrated that the proper strategy for controlling fire toxicity hazard is by reducing the burning rate, not by attempting to make the effluent less toxic. These findings directly indicate that regulations based on controlling the LC₅₀ cannot hope to address the proper concern of reducing fire fatalities. Copyright © 2000 John Wiley & Sons Ltd.     

A novel bioactive agent improves adhesion of resin-modified glass-ionomer to dentin

Bioactive glasses are surface-active and able to induce remineralization of dentin. Two resin-modified glass-ionomer cements (RMGICs) doped with bioactive glass (Biosilicate^®) were used as restorative materials in dentin. Experimental powders were made by incorporating 2, 5, and 10 wt% of Biosilicate^® in Vitremer^® (VT) and Fuji II LC^® (FL) powders. Commercial FL and VT were used as control materials. Six cylinders of each material were tested for failure in compression (1.0 mm/min), after 24 h storage in distilled water at 37 °C. For microtensile bond strength (MTBS) test, cavity preparations were performed on 30 noncarious human molars and restored with the tested materials. Teeth were stored in water (37 °C) for 24 h or 7 days, sectioned into beams and tested for failure in tension (0.5 mm/min). Data were analyzed by analysis of variance and multiple-comparison tests (p < 0.05). Analysis of debonded specimens was performed by scanning electron microscopy. Only incorporation of 2 wt% of Biosilicate^® did not decrease compressive strength of the RMGICs. Two weight percent of Biosilicate^® into RMGICs produced an increase in MTBS after 24 h for FL and after 24 h and 7 days for VT. Two weight percent of Biosilicate^® particles into RMGICs did not affect compressive strength and improved MTBS to dentin.     

A review of the literature on the gaseous products and toxicity generated from the pyrolysis and combustion of rigid polyurethane foams

The literature on rigid polyurethane foam has been reviewed with an emphasis on the gaseous products generated under various thermal decomposition conditions and the toxicity of those products. This review is limited to publications in English through 1984. Carbon monoxide (CO) and hydrogen cyanide (HCN) were the predominant toxicants found among more than a hundred other gaseous products. The generation of CO and HCN was found to increase with increasing combustion products from various rigid polyurethane foams. Lethality, incapacitation, physiological and biochemical parameters were employ as biological end points. In general, the combustion products generated from rigid polyurethane foam in the flaming mode appear from to be more toxic than those produced in the non-flaming mode. The LC₅₀ values for 30-min exposures ranged from 10 to 17 mg l^?1 in the flaming mode and were greater then 34 mg l^?1 in the non-flaming mode. With the exception of one case, in which a reactive type phosphorus containing fire retardant was used, the addition of fire retardants to rigid polyurethane foams does not appear to generate unusual toxic combustion products.     

Nylons: A review of the literature on products of combustion and toxicity

The literature on polyamides was reviewed to determine the nature and extent of information available on these materials which are commonly used in consumer and industrial applications. This review was limited to aliphatic polyamides normally called nylon and excludes aromatic polyamides such as Nomex and bicomponent polymers consisting of nylon and other polymers. The review was further limited to those publications in English through June 1984. Typical pyrolysis products from a broad range of nylons do not appear to differ greatly. Many of the decomposition products detected in vacuum pyrolysis experiments appear as products of thermal degradation in inert and air atmospheres. In air, a general reduction in the quantities of heavier hydrocarbons is noted along with an increase in the production of CO, CO₂, H₂O, NH₃, HCN and NO_x. The toxicity of the thermal degradation products from various types of nylon has been evaluated by nine different protocols. Reported LC₅₀ values range from 10.8 m l^?1 to 61.9 mg l^?1. Dyes apparently do not affect the materials' combustion products toxicity but an increase in the amount of backcoating on a nylon fabric increases toxicity. Time to death measurements show that volatile products from nylons are less toxic than those from rayons or cotton, while the blending of wool with nylon greatly increases the toxicity of the thermal decomposition products. In general, however, the overall toxicity of the thermal degradation products from nylon do not appear to be greatly different than those from many other polymeric materials. Large-scale test results are ambiguous, and it is difficult to interpret the results in terms of a single component in a multicomponent system.     

Low-Toxic and Nonirritant Biosurfactant Surfactin and its Performances in Detergent Formulations

Developing eco-friendly, nonirritant, low-toxic, and high-efficient surface active ingredients for detergents is an ongoing challenge in the detergent field. Surfactin is one of the representative lipopeptides produced by microorganisms. In this article, we report the surfactin isolated from cell-free broth of Bacillus subtilis HSO121 and purified by reversed-phase high-performance liquid chromatography for detergent formulations. The biodegradability, acute dermal irritation, acute oral toxicity (LD₅₀ and LC₅₀), surface activity, washing efficiency, and compatibility with hard water of the purified biosurfactant surfactin have been studied to explore the feasibility for applications of the surfactin in detergents. Acute oral toxicity tests (LD₅₀ > 5000 mg kg⁻¹, LC₅₀ > 1000 mg kg⁻¹) and skin irritation tests (PII = 0) indicate that the surfactin is a low-toxic and nonirritant ingredient for detergent formulation. Moreover, the surfactin shows excellent surface and interfacial properties of emulsification and wettability, high compatibility, and stability in a wide range of temperatures, pH, and hard water and acceptable properties in biodegradability and foaming ability, which suggests that the biosurfactant surfactin is a promising ingredient for detergent formations in our daily life and for industrial applications.     

Comparison of the smoke toxicity of four vinyl wire and cable compounds using different test methods

Four vinyl wire and cable materials were tested using five smoke toxic potency test methods: the NBS cup furnace test (in its flaming and non-flaming modes), the NIST radiant test, the NIBS IT₅₀ test (also using the radiant apparatus) and the UPITT test. One of the materials is a standard poly(vinyl chloride) (PVC) flexible wire and cable material, used commercially for wire insulation. The three other materials tested represent a new family of vinyl thermoplastic elastomer alloys, which are advanced materials with good fire performance, particularly in terms of heat release and smoke obscuration. It was found that the smokes from all four materials are similar in terms of their toxic potencies, and that they are all within the ‘common’ range of toxic potency found. In particular, the toxic potencies of the smoke from the new vinyl thermoplastic elastomer alloys are not significantly different from those of other traditional vinyl wire and cable compounds. The results of the tests were also interpreted in terms of the toxicities and concentrations of the individual gases emitted. The fractional effective dose of the toxicants analysed was sufficient to account for the toxicity of the smoke for the NBS cup furnace and the NISt radiant test. It was not able to account for the toxicity found in the UPITT test. The adequacy of the test protocols themselves was also investigated. It was found that the UPITT and the NIBS IT₅₀ method are inadequate for measurement of smoke toxicity. It was also found that the NIST radiant test protocol is the one most likely to lead to the smallest amount of future testing.     

Light-dependent effects of alpha-terthienyl in eggs,larvae, and pupae of mosquitoAedes aegypti

Alpha-terthienyl is toxic toAedes aegypti larvae in the dark, but its activity is much enhanced in the presence of ultraviolet light. The development of first-instar larvae treated with alpha-terthienyl and ultraviolet light was followed until the emergence of adults. The LC₅₀ value for first instars was about 0.002 ppm. Practically all the larvae which survived 24 hr reached adulthood. Fourth-instar larvae were also sensitive to photochemical treatment. When their development into adults was followed, the LC₅₀ value was 0.45 ppm. Contrary to earlier reports, alpha-terthienyl was also phototoxic in pupae, but not when the adults were about to emerge. The LC₅₀ value was ca. 0.06 ppm for pupae which were 1 or 2 days old. This is the first example where the activity of a photoinsecticide has been demonstrated in pupae. Alpha-terthienyl did not affect the hatching of eggs.     

UV-protective treatment for Vectran® fibers with hybrid coatings of TiO2/organic UV absorbers

The high performance of Vectran^® fiber makes its application as an envelope material for airship feasible. The ultraviolet (UV) resistance of this fiber, however, is poor, and UV irradiation in the stratospheric environment causes rapid fiber aging. To protect Vectran^® fibers from UV irradiation, we prepared TiO₂ nanosols via a sol–gel method and added benzotriazole UV-1130, triazine Tinuvin^® 477, and hindered amine Tinuvin^® 123 to them to form organic/inorganic hybrid coatings. Fiber specimens were subjected to accelerated aging using a xenon arc weatherometer. Mechanical measurements as well as surface morphology and chemical composition analyses were performed to evaluate the UV-protective performance of different coatings. Hybrid coatings performed better than TiO₂ coatings in protecting fibers from UV. Among the hybrid coatings obtained, UV-1130 especially reinforced the UV-protective ability of the TiO₂ coating because of its strong UV absorbance. Although the performances of Tinuvin^® 477 and Tinuvin^® 123 were below optimal when combined with TiO₂ alone, both hybrids exhibited excellent synergistic effects when used together with UV-1130 and improved the UV-protective ability of the resultant hybrid coatings.     

Novel Antifeedant and Insecticidal Compounds from Avocado Idioblast Cell Oil

Several insecticidal compounds have been identified by bioassaydriven fractionation of avocado, Persea americana Mill, idioblast cell oil. A flash chromatography fraction of the oil showed substantial toxicity to early instars of the generalist insect herbivore, Spodoptera exigua (Hübner) (100% mortality after seven days). Following further fractionation, five biologically active compounds, 2-(pentadecyl)furan, 2-(heptadecyl)furan, 2-(1E-pentadecenyl)furan, 2-(8Z,11Z-heptadecadienyl)furan, and the triglyceride triolein, were identified. Several minor components were also tentatively identified, including 2-(1Z-pentadecenyl)furan, 2-(1E-heptadecenyl)furan, and 2-(1E,8Z,11Z-heptadecatrienyl)furan. Several 2-alkylfurans of this type have been reported previously from avocado (Persea spp.) and have received the common name of avocadofurans. The major compounds were tested individually for toxic and growth inhibitory effects. Individually, the compounds had low to moderate toxicity. Of these, 2-(pentadecyl)furan had the greatest effects, with an LC₅₀ value of 1031 g/g. At concentrations of 600 g/g or higher in diets, larval growth was inhibited by >70% compared to controls. The analogous 2-(heptadecyl)furan had an LC₅₀ value of 1206 g/g, and also significantly reduced larval growth (>75% versus controls) at concentrations of >600 g/g. The unsaturated analogs 2-(1E-pentadecenyl)furan and 2-(8Z, 11Z-heptadecadienyl)furan were less toxic. Triolein was only weakly toxic, with an LC₅₀ value of 10,364 g/g diet. Larval growth was inhibited only at concentrations of 7000 g/g or higher. The potential of avocadofurans in insect control is discussed.     

Irritancy of the smoke (non-flaming mode) from materials used for coating wire and cable products,both in the presence and absence of halogens in their chemical composition

Four wire coating materials (two of them based on PVC and the two others based on XLPE) were assessed for the irritancy of their smoke, under non-flaming conditions, by using the respiratory depression method, expressed as the RD₅₀. The DIN 53 436 combustion tube was used as the fire model, at a temperature of 550°C (smouldering mode), and the animal model was the mouse. Animals were exposed for 10 min, at concentrations too low to cause lethality. It was found that there was relatively little difference between the irritancy of all four smokes. This was an unexpected result, since it had been predicted that PVC smoke would be much more irritating than XLPE smoke. In fact, the smoke from the PVC compounds had an RD₅₀ roughly in the range of 100–1000 ppm, while the smoke from the XLPE compounds had an RD₅₀ roughly in the range of 10–100 ppm. This means that PVC smoke is somewhat less irritating than XLPE smoke. The components in the smoke of all materials were determined by a combination of continuous gas analysis, ion chromatography and gas chromatography/mass spectrometry, with the objective of understanding the factors causing the irritancy. Hydrogen chloride, one of the major decomposition products of PVC, is also the most important smoke constituent causing irritancy of the smoke. Its irritancy, however, was insufficient, by a considerable margin, to explain the full degree of irritancy found. The RD₅₀ of HCl is, like that of PVC smoke, in the range of 100–1000 ppm. On the other hand, the only compound found in the smoke of XLPE compounds with an RD₅₀ in the same 10–100 ppm range as he overall smoke is methyl vinyl ketone. Unfortunately, the concentration of methyl vinyl ketone was much too low to account for the irritancy levels encountered. Literature data indicate that polyethylene smoke is rich in long-lived free radicals and that PVC smoke does not contain them. Moreover, such free radicals are associated with various illnesses, particularly with respiratory symptoms. Thus, it is speculated that such free radicals could be the cause of the high irritancy of the smoke from the XLPE wire coating materials.